PLEASE NOTE: THIS PROJECT IS NOT SCIENTIFIC. IT IS A HOBBY.
"I was looking for information on an old mammal and found this lot. What is this
project?"
It's got lots of information on old mammals. For a short bit of background information, see
here.
The original version of this directory has been split into two webpages.
Dryolestoidea I contains both relatively
basal and derived forms, with
the latter being from the Cretaceous of South America. This page is now Dryolestoidea II,
and it provides a home for the families of Dryolestidae and Paurodontidae. The classic age
of both days of both groups spanned from the Upper Jurassic-Lower Cretaceous of the
northern hemisphere. However, the dryolestids persisted for much longer in South America,
and some were presumably lucky enough to take part in the mass die-ins at the end of the
Cretaceous. While a dryolestoid is known to have survived into the Paleocene
(Peligrotherium), the same can't be
said of any dryolestidans.
Gremlins can be active when webpages are split, and they may have done some naughty things
with links between different directories. |
| Link:
T Mike Keesey, The Ages of the Mesozoic
http://dinosauricon.com/times/index.html
If you’re not sure what Kimmeridgian or Tithonian mean, this is where you can look them up.
When it comes to chronology, I’ve got a memory like one of those metal what-nots with holes
in. |
A. Paurodontidae B. Dryolestidae
| Taxon: Paurodontidae Marsh, 1887
Apologies for the next sentence. This name seems to have opened up a can of worms.
Paurodontids were small mammals which chewed grubs and insects. 150 million years later,
paurodontids are supposedly nematodes, simple worms, which chew plants.
http://nematode.unl.edu/nemaid.htm
Paurodontidae Thorne, 1941 is held to be a family of plant parasitic nematodes within the
suborder Tylenchina Chitwood, 1933. The rules of zoological nomenclature don’t allow two
families to share a common name. The nematodes will have to choose a new one. If anybody
happens to know a friend of plant parasites, such as Stictylus, who will assist them,
please put them in contact. This is not something I have any intention of pursuing myself,
though I’m happy to pass on any relevant details I might have available.
Back to the mammals
According to the definition I'm presently observing, paurodontids includes the proposed
family of Henkelotheriidae, a point which is briefly addressed in the entry for
Henkelotherium. |
| Links:
Plant and Insect Parasitic Nematode Home Page, University of Nebraska
http://nematode.unl.edu/wormhome.htm
"If all the matter in the universe except the nematodes were swept away, our world
would still be dimly recognizable…" - Cobb NA, 1914. (But to whom? - Self MY, 2001).
Photo Gallery, Trichodorous obtuses
http://nematode.unl.edu/trob.htm
OK, I appreciate this nematode belongs to a different family, but at least it’s a plant
parasitical one. And now back to Mesozoic mammals.
"Paurodontid therians remain among the rarest of Late
Jurassic mammals despite over a century of collecting in
Upper Jurassic sedimentary rocks. They are known only from three localities worldwide:
Guimarota, Portugal, and Como Bluff and Pine Tree Ridge, Wyoming", (Carpenter, 1998
p.402).
If correct, Brancatherulum isn't part of this family. (The definition of Theria
followed in these directories doesn't allow for the inclusion of Paurodontidae within the
taxon, but other definitions are possible.) |
| Genera: Araeodon,
Archaeotrigon,
Brancatherulum,
Dorsetodon,
Drescheratherium, Comotherium,
Euthlastus, Foxraptor,
Henkelotherium, Paurodon,
Pelicopsis, Tanaodon (= Tathiodon),
Tathiodon, otherreports
Time-Line:
Lower Cretaceous: Dorsetodon
Upper Jurassic: Araeodon, Archaeotrigon, Brancatherulum,
Comotherium, Drescheratherium, Euthlastus, Foxraptor,
Henkelotherium, Paurodon, Pelicopsis, Tathiodon |
| Genus: Araeodon Simpson GG,
1937
'weak tooth' |
| Species: | Araeodon intermissus ?Simpson GG, 1937 |
| Place: | Como Bluff Morrison Formation,
Wyoming & Dinosaur National Monument, Utah |
| Country: | USA |
| Age: | Upper Jurassic |
| Remarks: | The following is based upon my reading of Simpson,
1937.
Henry Osborn of the American Museum of Natural History was particularly interested in
getting more Mesozoic mammals in the 1890s. Knowing that Marsh had obtained many fossils
earlier from a Wyoming locality called Quarry 9, Osborne arranged for a collecting expedition
there in 1897 (p1). Two tons of matrix were brought back to New York for examination, and
the total of mammal specimens identified was slightly less than one. There were bits and
pieces of reptiles, but not a mammalian dickey bird. The remaining stuff was securely
archived, which is a polite way of saying shoved into a cupboard under the staircase. I
admit, I don't know where it was stored exactly, but nobody paid it any further attention
for a while. And then a while longer...
After many whiles, (about forty years worth of them), somebody did have another look. Half
hidden among the this and the that, was a scrap of lower jaw less than 1.5cm in length.
This happened to be just the sort of thing Osborne had been hoping for, so it's a pity he
didn't live long enough to meet it. Nevertheless, George Simpson much appreciated the
fossil. He happened to be about the most accomplished specialist for fossil mammals the
planet has ever known and, at the time of publication, hardly any further Jurassic remains
had been found for decades anywhere (p2). Museum collections can be good places to find
things.
Tooth formula
This is uncertain. For a start, only a partial dentary
was available, so nothing is known about the upper teeth. The lowers comprised some number
of incisors or other and presumably a
canine. If the remaining teeth and
alveoli have been correctly interpreted, then there were
probably three premolars and four
molars. It's possible a further cheek tooth could have been
present, but this seems unlikely.
A brief dental (and dentary) check up
The p1? premolar was very small and it was followed by two larger colleagues. The
postcanine trigonids
are proportionately long, while the double-rooted molars have small, unbasined,
unicusped talonids.
Paurodon appears to be a close relative. That genus, however, manages only six
cheek teeth instead of at least seven, and they're more widely spaced (p.3).
Araeodon doesn't have a diastema behind the
canine. Furthermore, the cusps on the lingual side are
more distinct in this critter.
The molars resemble those of Archaeotrigon brevimaxillus
even more closely, but there are contrasts on the talonids. These are smaller for
Araeodon, less semi-circular in shape and not positioned as lingually. In addition,
Arch. b. has only two premolars and three molars. That's at least two fewer
postcanines. Its sister, Archaeotrigon distagmus
probably had four molars as did Araeodon, (the other teeth aren't known), but those molars
are structurally more reminiscent of that genus.
Size
The owner of the jaw was a titch, and that helped it to hide among the matrix so
successfully. The three preserved teeth have lengths of 0.4, 1.0 and 1.1mm
respectively (presumably p1, p2 and m1). This jaw is proportionately short, and that's
unusual for what Simpson termed pantotheres.
Absent friends
Alveoli provide some information on missing teeth, but
crushing has diminished clarity. It's not possible to deduce a number for incisors. The
tooth in front of the first premolar was probably a canine, as there seems to be a single,
relatively large alveolus. A less likely possibility would be another premolar. The
p1 itself is single-rooted, but there are indications suggesting it divides lower down.
Its colleague, p2, is a larger but similarly designed tooth (p.5). Its crown is relatively
low and long with just a hint of a talonid, This tooth is
clearly double-rooted, and that helps suggests the pair of alveoli behind housed a
similarly sized p3, although not necessarily.
Preserved tooth number three is a molar. Its trigonid is
large and lengthy. The protoconid is roughly
triangular and connects with the paraconid and
metaconid by means of weakly developed crests. The
alveoli indicate m2 and 3 were both a bit larger than this molar, while m4 was the runt
of the litter. Front roots are larger than rear ones (p.6).
What's available of the coronoid process of the jaw indicates it ascended gently.
Holotype
The holotype, AMNH 27775, is a right mandible with three
postcanine teeth. The specific name means 'put off', 'neglected'. This reflects the fact
that it hid in the museum for most of four decades before being noticed. |
| Reference: | Simpson (1937), A new Jurassic mammal, American Museum
Novitates, 943, p.1-6. |
| Genus: Archaeotrigon
Simpson GG, 1927
Remarks : The SVP Bibliography BFV, (link below), offers the following earliest citation,
(as well as three more from the '20s). I’ve seen the year of the description given as 1937,
which cannot be right. 1927 is cited by McKenna & Bell, (1997), so that's almost
certainly correct.
Doubtful Reference?: Simpson (1926), The age of the Morrison Formation. American J of Sci
5, p.196-216. |
| Species: | Archaeotrigon brevimaxillus |
| Place: | Morrison Formation, Wyoming |
| Country: | USA |
| Age: | Upper Jurassic |
| Remarks: | This is listed in Table III of Carpenter, 1998
(p.402). It had a lower postcanine formula of two
premolars and 3-4 molars.
Simpson, 1937 provides some discussion and reveals this is the senior species for the
genus.
Peabody Museum, Yale. Collected in 1881, (Reed-Como party). "Not verified". |
| Reference: | |
| Species: | Archaeotrigon distagmus Simpson GG, 1929 |
| Aka: | Archaeotrigon secundus "not verified" |
| Place: | Morrison Formation, Wyoming |
| Country: | USA |
| Age: | Upper Jurassic |
| Remarks: |
The holotype is at the Peabody. Collected by Reed WH in 1880,
and also listed in the same table by Carpenter; ? premolars
and 4? molars. |
| Reference: | Simpson (1929), American Mesozoic Mammalia. Mem. Peabody Mus.
Nat. Hist. iii (i), p.1-235. |
| Genus: Brancatherulum
Dietrich WO, 1927 |
| Species: | Brancatherulum tendagurense Dietrich WO, 1927 |
| Place: | Upper Saurian Bed, Tendaguru |
| Country: | Tanzania, (which was German East Africa) |
| Age: | Kimmeridgian-Tithonian, Upper Jurassic |
| Remarks: | The genus is based upon a fragmentary and
toothless jaw, (Heinrich, 1998, p.269).
This is a small part of the booty from the famous pre First World War fossil hunt, which
found its way to the Humboldt Museum in Berlin. The generic name is in honour of W Branca,
who wrote about this fossil in 1916, (Ein Säugetier?-Unterkiefer aus den Tendaguru-Schichten.
Arch. Biont. 4, p.137-140). |
| Reference: | Dietrich (1927), Brancatherulum n.g., ein
Proplacentalier aus dem obersten Jura des Tendaguru in Deutsch-Ostafrika. Centralbl. Min.
Geol. Pal. 1927(B), p.423-426. |
| Genus: Comotherium
Prothero DR, 1981
'Como beast'
Aka: Euthlastus (partly) |
| Species: | Comotherium richi Prothero DR, 1981 |
| Place: | Morrison Formation, Wyoming |
| Country: | USA |
| Age: | Upper Jurassic |
| Remarks: |
A cast of the holotype is at Yale. The original was collected by Schaff CR, 1969. This
genus is based on upper dentition, which were originally
referred to Euthlastus. "It appears that Euthlastus and Comotherium
are closely related, and perhaps should be considered congeneric. It also seems likely
that if Euthlastus is a paurodontid, Comotherium must be as well",
(Engelmann & Callison 1998, p.377).
Lillegraven, 2000 reports that Thomas Martin agreed and reassigned Comotherium in
1999. |
| Reference: | Prothero (1981), New Jurassic mammals from Como Bluff, Wyoming,
and the interrelationships of non-tribosphenic Theria. Bull. Am. Mus. Nat. His. 167, p.277-
326. |
| Genus: Dorsetodon Ensom
PC & Sigogneau-Russell D, 1998
'Dorset tooth'
Remarks: Should an explanation of the name be required, 'odon' means tooth and the remains
come from Dorset. |
| Species: | Dorsetodon haysomi Ensom PC & Sigogneau-Russell
D, 1998 |
Place: | Purbeck Limestone Group, Dorset |
| Country: | England |
| Age: | Lower Cretaceous (or Upper Jurassic) |
| Remarks: | The following is based upon my reading of Ensom
& Sigogneau-Russell, 1998.
The Purbeck Limestone Group in southeast Dorset was the second source of Mesozoic mammal
fossis to enter production in southern England. That also means it was the second in the
world, as all previous finds had come from the
the Forest Marble Formation of Oxfordshire. Dorset joined in during the 1850s. Work
began in a new locality in a quarry in the 1980s, and this has allowed the Lower
Cretaceous fauna to expand further (p.35). In the local quarrying terminology, a particular
layer of clay is known as the Sly, and this marks the top of the fossil bearing stratum.
It's thought this was deposited on the edges of shallow lakes. This horizon has also
produced remains from multituberculates,
docodonts,
'symmetrodonts' and a possible early boreosphenid
now known as Tribactonodon (p.36).
These fossils were obtained from about three tonnes of clay, and this impressive quantity
was supplemented by smaller amounts form a few kilometres further east. The material was
sorted through sieves down to a mesh size of 0.3mm (p.37).
'Dorset tooth'
Only teeth have been found and they merit the term mini. The holotype is the smallest of
the seven identified specimens (length 0.65mm, width 0.42), but the longest of them only
manages 0.82mm.
Of the main cusps, the protoconid is fairly high but
not in comparison to either Paurodon or
Archaeotrigon. There's a distinct
paraconid which is lower than the
metaconid. That's a distinction from other paurodontids
excepting for Archaeotrigon and Tathiodon. The paraconid
is a relatively flat, shelf-like cusp which angles forwards; a typical paurodontid
trait.
The roots broke off but their bases are preserved (p.39). The back root is aligned straight
behind the front one. This is in contrast to dryolestids, which had the rear root set
more lingually.
Affinities
The roots are subequal, the tooth crown isn't compressed and the talonid is relatively
large (p.49). These factors inidicate affinities with paurodontids rather than dryolestids.
It had been suggested that such differences could be due to a reason other than a familial
one; paurodontid dentitions could perhaps be milk teeth.
However, distinctions in the patterns of wear undermine such a conclusion. Paurodontidae
is maintained and this genus referrred to it.
Upper teeth
None have been identified for Dorsetodon in the collection of three dozen dryolestoid
uppers. 26 are clearly dryolestid. The other ten could be paurodontid, but it's not
presently clear.
Purbeckian dryolestoids
Dorsetodon is the first paurodontid detected in the fauna, but there are at least
three dryolestid species; Amblotherium nanum, A.
pusillum and Kurtodon. As some of the collected lower
molars don't conform to any of those taxa, there must be at
least one further species awaiting recognition.
Holotype
DORCM GS 433 is a right lower molar in the collection of the Dorset County Museum,
Dorchester. Half-a-dozen colleagues also inhabit this sanctuary, which is well worth a
visit should you happen to be in the area. As the county is justifiably renowned for some
beautiful landscape and small towns and villages that break beyond the definition of
picturesque, there are plenty of reasons to go there. The specific name honours WT Haysom.
He both the relavent quarry and alerted Paul Ensom to its possibilities. |
| Reference: | Ensom & Sigogneau-Russell (1998), New dryolestoid mammals
from the basal Purbeck Limestone Group of southern England. Palaeontology, 41(1), p.35-55.
|
| Genus: Drescheratherium
Krebs B, 1998
'Drescher's beast'
Remarks: The generic name honours Ellen Drescher: "who skillfully prepared and preserved
many of the fossils from the Guimarota mine", (Krebs 2000, p.121). The original
author assigned the genus to the family of Henkelotheriidae Krebs, 1991. |
| Species: | Drescheratherium acutum Krebs B, 1998 |
| Place: | Guimarota |
| Country: | Portugal |
| Age: | Kimmeridgian, Upper Jurassic |
| Remarks: | The following is based upon my reading of Krebs,
1998, which happens to be written in German. Thanks are due to the tireless
supplier.
Drescheratherium was described as being a henkelotheriid insectivore from the
Upper Jurassic of Portugal. I'm still including it within the family of Paurodontidae.
Only the upper jaw was described by Krebs (p.99), and four specimens volunteered their
assistance. It might be thought an odd coincidence that only upper jaws had been found,
but that probably isn't actually the case. Likely lower counterparts were also collected.
However, in contrast to the local Henkelotherium,
uppers and lowers were never found in direct association, and that made securely matching
them up more challenging. An intended study of the relevant
dentaries failed to appear. As the author died in 2001, it's presumably a task
somebody else will have to pursue.
The key differences to Henkelotherium are found in the teeth. 'Drescher's beast'
has a puzzlingly vast canine and, from the English language
Abstract: "... a vestigial P2" premolar. It's 'completely reduced' ("die völlige
Reduktion") in the German version. The description finally makes it clear that
'vestigial' in this case actually means 'absent'; words which aren't generally seen as
synonyms.
All specimens came from remains of an ancient swamp preserved in a coalmine near the
central Portuguese Atlantic Coast. In terms of Upper Jurassic mammal fossils, its wealth
of rare treasures makes El Dorado appear more like a poorly stocked junk shop. A few
sites of roughly similar age have yielded shards of jaw on a par with
Drescheratherium in terms of quality, but localities with fairly complete skeletons
are much rarer. From the Upper Jurassic only the Morrison Formation
Fruitafossor comes to mind. This
bankrupt coalmine managed two. Not so many years ago, I couldn't find a webpage giving
much background on the former swamp, so I felt moved to write my own:
Guimarota.
Jaw
The maxilla is described as comparatively large, but
the comparison is made in terms of a tiny mammal (p.92). Few other skull bones were
preserved excepting for parts of the jugal and perhaps
premaxilla, but their joints with the maxilla aren't clearly defined. It's possible
the premaxilla suture corresponds with the branch with the break to the front portion of
the jaw. Part of the wall of the maxilla is also missing, and that actually has the
advantage of enhancing the view of the first two molars (p.93).
According to the text, the final premolar was present on the maxilla, and I can't detect
anything suggesting that might not be literally meant. It's since gone absent without
leave. The thing broke off during preparation of the fossil, and was stuck back on.
Showing great determination for freedom, it then broke off again before a drawing was
made, although not prior to its participation in a photo session. The present address
of this tooth is unknown.
An intriguing jaw feature is found around the root of the canine. It's a very small
foramen pit; the sort of thing that could've been required for a specialised kind of
sense organ known as a whisker. There are a couple sentences in the description giving
some trouble, so I think I'd best quote them in full. "Über dem letzten Incisiv, an
den vorderen Abschluß des Maxillare grenzend, fällt ein hinten und oben scharf aber
unregelmäßig umrandetes, etwas eingesenktes Areal auf, das nicht auf Frakturen
zurückzuführen ist, da auf der Innenseite keine solchen in Erscheinung treten. Seine
Oberfläche zeigt eine feine, nach vorn gerichtete Faserung und eine ebenso verlaufende,
seichte Rinne. Diese Zone dürfte die flächige Sutur für das dich dort dem Maxillare
anlagernde Praemaxillare sein." I think that boils down to there being a somewhat sunken,
fine feature that may be part of the suture between the maxilla and premaxilla, and this
is in the bone at the level of the final incisor, but I'm not entirely sure.
Be that as it may, there's a short maxillary process for the
zygomatic arch, but most of that cheek structure was contributed by the jugal bone.
Again, it's not fully clear where the border between those bones is actually located.
Dentition
The count of incisors is unknown. However, lower jaws
likely belonging to the same taxon have been found, although
not formally assigned, and they indicate four such teeth per side. Frequently, although
not in my case, mammals enjoy having one more upper than lower incisor (p.94), and that
tendency prompts an expectation of five. Sticking with known details, the upper dental
formula per side is: ? incisors, 1 canine, 3
premolars (P2 isn't among them) and 5
molars.
Incisors
A lack of specimens doesn't always mean a complete absence of relevant information. Some
is provided by the jaws. There's a kind of pocket behind the remains of the final
incisor, and its depths are obscured with some coal. Other specimens, however, show
this feature isn't an alveolus for an upper tooth.
Rather, it's space to accommodate the crown of the lower canine. It's also made
explicitly clear that the final incisor is undoubtedly positioned on the maxilla, as
evidence for the premaxilla suture is in front of the vacated alveolus. Typical
mammals are no longer keen on having maxillary incisors,
but a number of earlier models rather enjoyed one there, or between the maxilla-premaxilla
border.
That now absent incisor was a small, vertically directed tooth. As half the root had
slipped out from the alveolus prior to the fossil being artificially stabilized, its
anchorage must've been insecure. It had a blunt, somewhat flattened crown with light
wear on its tip.
Canine
This tooth had the decency to remain in place, and it's extravagantly vast; over three
times higher than the tallest premolar (p.98). If Christopher Lee had used fangs of
these proportions when portraying Count Dracula, then they'd presumably have extended
down towards the base of his chin. The former owner must've gained some satisfaction
from possessing such things, yet nothing indicates it involved sucking blood from the
necks of scantily clad actresses with large, heaving breasts. Pity. Whatever its
value, it was only a single-rooted tooth with a simple, extremely sharp tip. Seen from
the side, it's somewhat curved along its course, and recurved at the top. In front view,
on the other hand, the crown manages to look straight. Some slippage from the alveolus
has occurred, so its height could be exaggerated to some degree. Nevertheless, it
nothing less than extravagantly vast.
Premolars
Despite the final premolar being termed P4, there are only three of these teeth, and
comparisons with Henkelotherium provide sense for
the numbering used. 'Henkel's beast' has four but, in the corresponding position to
the second of those, Frau 'Drescher's beast' has a large, natural gap. P2 is generally
the smallest in the series for paurodontids and relatives. In this case, the ancestors
took an even more disdainful line and dispensed with the damned thing entirely. The
state of wear on teeth shows this animal to have been an adult, and not expecting any
further tooth replacement, but there's no sign of any resorption, and no specimen has a
premolar in this position. It's not unknown for the second premolar to be lost during
life among Mesozoic mammals, and that position to be converted into a diastema as an
adult condition, eg Hakusanodon; in
that case, a lower premolar. However, such behaviour would generally leaved traces such
as alveoli plugged with bone. Krebs reports nothing of that kind here.
While the diastema between P1 and P3 is the widest in the series, other gaps occur between
the canine and premolars, and between P3 and P4. A still smaller one comes between that
and the first molar. P1 is the smallest premolar and P4 the largest. There's a clear
morphological contrast between P4 and the molars, but the tooth has a similar height to
M1. All premolar positions are honoured with loving descriptions. However, I'll
confine my briefer attentions to the P4, the best developed of the team.
Most of the crown's devoted to housing a single cusp, and it's off-centre on account of
being a bit forwards of the mid-line. The front face is convex whereas the rear one's
concave at the top and somewhat convex lower down. A small wear facet occurs on the
summit, a ridge behind the tip is barely worn, and a strong wear facet can be seen
further back. Remains of a short lingual
cingulum are found posteriorly, whereas a stronger one
features on the opposite side of the tooth. Short cingula also enliven the front regions
of each side, but not continuous cingulum is present (p.99). An
ectoflexus embays into the crown on the buccal side.
There are two roots with the larger of them, the rear root, set more lingually.
Molars
In keeping with traditions, the molars are more complex teeth. There are five and, as
the rear one occupies the back of the available tooth row space, that's the full
complement. These teeth aren't separated from one another by gaps. The rear posterior
buccal corner of the trigon extends back to greet the front lingual side of the
parastyle cusp of the following tooth. All molars are similarly built, but proportions
and details alter along the row, in a flowing story-like way, with themes. That helpful
habit could allow the identification of the positions of isolated molars. The occlusal
area increases from M1 to M3 and then decreases; M1 is longer than wide whereas M5 is
wider than long; the level of wear decreases from front to rear, and that reflects the
amount of labour dictated by the sequence of eruption. Rear molars erupted later than
front ones. Again, all positions are eulogised.
Krebs uses his terminology in a purely descriptive sense. For example, when he writes
metacond (Metaconus in German), it's meant as a reference to the cusp in the
appropriate position, and is agnostic as to whether it's a homologue of a genuine metacone;
one found on a tribosphenic molar. Whether it's a
homologue or not wasn't an issue of concern (p.100).
At this juncture, I was going to briefly allude to a specimen tooth, the M3, but it
happens to be rather broken. Still, as I'm hoping to gain a more generalized idea
rather than attempting a blow by blow account of each tooth, I'm going jump ahead to
page 103 instead for the "Wichtigste Merkmale... der oberen Molaren"; the most
important characteristics of the upper molars.
# There's a strong morphological contrast between the premolars and molars, and a
gradual sequence of developments running from M1 to M3; eg. length-width ratio.
# The front wall of the trigon rises vertically from the alveolus. The paracone is
large and sharp whereas the stylo- and metacone are significantly lower, and about as
tall as one another. The stylocone is positioned on the buccal end of a crest, the
paracristid, close to the front margin of the trigon. It's actually on margin in the
case of M1, but drifts somewhat lingually on each following
crown. The metacone of M3 is an elongated and raised element, centrally located on a
rear ridge.
# A parastyle forms a talon-like structure set buccally
on the leading flank of the trigon. It's clearly separated from the stylocone on M1,
drifts occlusalwärts (? I don't know what 'occlusal-wards' could mean) along the
series, and reaches the level of the stylocone with the final molar.
# The occlusal area of the trigon is bordered by a weak buccal cingulum, and this carries
a number of small cuspules. It starts at the stylocone on the first three molars, but
beyond that area on the final two. The rounded, posterobuccal corner of the trigon has
an indentation separating the cingulum from the small metastyle found on the end of the
rear ridge.
# The occlusal surface of the trigon has a median ridge (in the sense of Simpson, 1928
and, therefore, not a crista) running from the buccal side of the paracone to the central
cuspule of the cingulum. This ridge is somewhat inflated on the middle molars (definitely
an intended plural).
# A light ectoflexus bay generally occurs on the buccal side of crowns. It's clearest
on M4 but entirely absent for M5.
# Upper molars are triple-rooted.
As some readers will notice, should there be any, dryolestoid upper molars are things I
still find difficult. I can't recall having read anything in particular about them
prior to this paper. That suggests even more caution than usual should be exercised
with these notes.
Affinities
As upper molars don't have protocones and the probable (undescribed) lowers lack basined
talonids, they don't meet the requirements for being
called tribosphenic (p.106). Other than for the
great size of the canine and the absence of P2, the closest comparison can be made with
Henkelotherium, and both can be allocated to the same family. I'll leave you to
discuss whether that's Henekelotheriidae or Paurodontidae among yourselves, but the
latter is presently followed here.
This new genus brought the membership of Krebs' Henekelotheriidae up to four; the
Portuguese pair and North America's Pelicopsis and
Tathiodon. An extended diagnosis of the family was
provided.
Postcanine lengths
A table contains this information on page 109. As only uppers were under discussion,
sizes for lowers aren't given.
P1 (3 specimens) 0.51-0.57mm; P3 (4 sp.) 0.55-0.78mm; P4 (2 sp.) both 0.96mm.
M1 (4 specimens) 0.86-0.93mm; M2 (4 sp.) 0.93-1.15mm; M3 (3 sp.) 0.93-1.13mm; M4 (3 sp.)
0.83-0.99mm.
The positions for the holotype.
P1 0.51mm; P3 0.61; P4 0.96; M1 0.82; M2 0.93; M3 1.07; M4 0.83, M5 0.66.
Holotype
Gui Mam 4/73, then attending the Freie Universität in Berlin, plans to move to Lisbon
after graduation, and take up employment at the Museo dos Servicas Geologicos. It wishes
to watch Benfica play live rather than making do with Herta Berlin and the telly. The
specific name derives from the Latin, acutum, meaning 'point', 'sharp'. This
refers to both the upper canine and molar paracone.
Additional notes
Further information was summarized in Krebs, 2000. Known from isolated upper and lower
jaws, Krebs still referred to this genus as a henkelotheriid. The upper second
premolar, small in
Henkelotherium, is not present in Drescheratherium, which leaves a
short gap. Meanwhile, the first premolar of the dentary
is much reduced. This is all connected with the presence of a spectacular upper
canine; a sort of sabre-tooth pseudo-shrew? As very much
a shrew-sized creature, this genus was probably not a ferocious predator towards anything
that required deep stabs. Quite what it would have got up to with a long, pointed
canine isn't clear. (With further thanks to Vince Ward.) |
| Reference: | Krebs B (1998), Drescheratherium acutum gen. et sp. nov.,
ein neuer Eupantotherier (Mammalia) aus dem Oberen Jura von Portugal, Berliner geowiss.
Anhandlungen, E28, S.91-111. |
| Genus: Euthlastus Simpson
GG, 1927 |
| Species: | Euthlastus cordiformis Simpson GG, 1927 |
| Place: | Morrison Formation, Wyoming |
| Country: | USA |
| Age: | Upper Jurassic |
| Remarks: |
Another type fossil from the Peabody, which was collected by the
Reed-Como party in 1880. The earliest citation I’ve found comes from 1929, so it’s presumably
not the first.
Engelmann & Callison, 1998 (p.366) suggests this genus is based upon upper teeth. They
also seem to list it as a dryolestid and not a paurodontid. Morrison Formation paurodontids
are reportedly only based on lower dentitions.
However, on page 376): "We believe that Euthlastus is a paurodontid. An
undescribed specimen from Fruita with articulated skull and jaws appears to have a
paurodontid lower dentition and upper teeth very similar to Euthlastus, and the
type specimen of E. cordiformis has only five
molars." Consequently, I've paurodontized it. |
| Reference: | |
| Genus: Foxraptor Bakker RT
& Carpenter K, 1990
'Fox’s raider'
Remarks: Named in honour of Canadian paleontologist, Richard Fox. |
| Species: | Foxraptor atrox Bakker RT & Carpenter K, 1990 |
| Place: | Pine Tree Ridge, Morrison
Formation |
| Country: | USA |
| Age: | Upper Jurassic |
| Remarks: | Much of the following is based upon my reading of
Carpenter, 1998.
Although this genus and the Zofiabaatar were
established in 1990, the original description included some unfortunate problems. I don't
want to delve into or dwell upon them. However, a paragraph from page 394 provides some
context.
"Numerous errors regarding Zofiabaatar and Foxraptor by Bakker and
Carpenter (1990) necessitates redescription of the specimens. The turtle, Uluops,
is now under restudy by Gene Gaffney who will correct errors in Carpenter and Bakker
(1990). In both contributions I appear as an author in name only and without my
knowledge."
The lower jaw is robust and the dental formula reads: (lowers only): presumably four
incisors (only two preserved), one
canine, three premolars and
five molars, (p.398). The
postcanines are more numerous than in other North American paurodontids, but more are
found in the Portuguese taxa of
Drescheratherium and Henkelotherium from
Guimarota,
(p.399).
Mandible
The jaw is short and stout, (p.400), which is typical for the family. The external surface
is relatively free of features, although a depression at the back of the only known specimen
is the front of the masseter fossa. A shallow trough extends along the preserved length of
the lingual face. This is Herr
Meckel's groove. It deepens towards the front, and
descends more closely to the base of the jaw.
Teeth: incisors
The third and fourth are preserved, and they're somewhat spatulate. This is because the
tips curve in towards the tongue.
Canine
This is the tallest tooth in the mouth, and it's also robust. Again, the tip curves
lingually. It's separated from the first postcanine by a
small diastema, and this is a similarity with
Paurodon. At least, that's what an impression in the
surrounding matrix seems to indicate, (p.401). This area has suffered damage.
Premolars
The three premolars increase in size from p1 to p3, and their lengths range from 0.47-1.06mm.
Each has two roots of a similar size. The p1 and p2 are positioned close to one another,
while the p3 is relatively distant. The first premolar is small and strongly worn. The
largest tooth, the p3, has a reasonably well defined
cingulum on the lingual side. This is also present on the p2, but it's not as well
developed. The p3 is in direct contact with the first molar.
Molars
Four are preserved and an alveolus shows a fifth was
originally present. They're packed tightly together and have two roots each, which are of
similar sizes. I'm going to concentrate a bit on the first as a representative.
The trigonid of the m1 is large and longer than wide. The
cusps are relatively low and worn. The protoconid is
dominant. The paraconid at the front,
(lingual side), slopes diagonally forwards, and it's
connected to the front of the protoconid by a ridge; an abraded paracristid. The
metaconid is next to the rear of the dominant cusp, and
connects with a strong metacristid. This area bears a clear wear facet. Behind the
trigonid is a low, very small talonid heel. The
paraconid of the following tooth overhangs it.
The m2 is much the same, but larger. Its talonid isn't overhung by the proceeding tooth.
The m3 is similar in size with the m2, (p.402). Perhaps out of a sense of fun, its talonid
is overhung. The fourth molar is both the longest and widest. It tilts forwards. The
paraconid is more like a platform than a cusp. A further cusp, (the hypoconulid), is
located on the talonid and bears a wear facet. The lengths of m1 to m4 range from
1.17-1.33mm.
The m5 must have been much smaller and there's only one
alveolus. As the hole could conceivably have accommodated a pair of roots, the tooth
may or mayn't have been double-rooted.
Paurodontids
"Foxraptor differs from Paurodon, Archaeotrigon, Tathiodon, and
Araeodon (see Simpson 1929; 1937) in having a greater number of
postcanine teeth, and from the Guimarota specimens in
having few postcanine teeth", (p.402). There were, and perhaps still are differing
opinions as to whether more of these choppers represents a basal
or a further derived condition. The Guimarota
paurodontids are somewhat older, but that doesn't necessarily mean they must be more
'primitive'. Evolution can be messy, and numbers of teeth can increase as well as decrease
over time, as dolphins and armadillos demonstrate convincingly. Morphology is likely to be
more instructive than straightforward numerology. The geologically youngest paurodontid of
them all was Foxraptor, though Dorsetodon may have subsequently beaten it.
Holotype
The holotype, UCM 59089, is in the collection of the University of Colorado Museum. It's
also been incorrectly referred to as UCM 47257.
An unrelated FoxRaptor used to be a #sonic regular, which I don’t think has any obvious
Mesozoic connections. As this is a cartoon character, the rules of scientific nomenclature
are not applicable. |
| Reference: | Bakker & Carpenter (1990), A new latest Jurassic vertebrate
fauna, from the highest levels of the Morrison Formation at Como Bluffs, Wyoming. Part III.
The mammals; a new multituberculate and a new paurodont. Hunteria, 2, p.4-8. |
| Genus: Henkelotherium
Krebs B, 1991
'Henkel's beast'
Aka: "Simpsonodon" ('Simpson's tooth'- nomen nudum) Kühne W, 1968
Remarks: Named in honour of Siegfried Henkel, who was strongly involved in reopening the
Guimarota coal-mine for the purposes of paleontology.
Henkelotheriids?
This genus was referred to Henkelotheriidae Krebs, 1991, but this isn't a family I
presently provide a home for. The concept is discussed by Ensom & Sigogneau-Russell,
1998.
The diagnosis offered by Krebs for the taxon isn't presently overly
convincing. Henkelotheriids are supposed to be toothier than paurodontids (p.46). The
lower molars should have
paraconids and metaconids which are less reduced,
talonids which aren't centrally located, and the jaws
ought to be longer. Apparent similarities led him to add
Pelicopsis (known only from upper molars) and
Tathiodon (lowers) to the clan (p.48). Subsequently,
Drescheratherium also asked to be added.
Jaws are in rather short supply for some of the relevant genera, so whether there's a
characteristic difference in this regard is unclear (p.50). Furthermore, the relative
proportions of paraconids, metaconids talonids are variable for different molars in
Henkelotherium and paurodontids; eg. Archaeotrigon
brevimaxillus and Foxraptor. The wear facets of
Henkelotherium match well with paurodontids. This all suggests that the value of a
separate family is presently unclear, and its basis is, at least, debatable.
"To sum up, the distinction of Henkelotheriidae and Paurodontidae founded on the lower
molars needs to be confirmed by comparative material and studies" (p.51). |
| Species: | Henkelotherium guimarotae Krebs B, 1991 |
| Aka: | "Simpsonodon guimarotae" Kühne W, 1968 (nomen
nudum) |
| Place: | Guimarota |
| Country: | Portugal |
| Age: | Kimmeridgian, Upper Jurassic |
| Remarks: |
With the body and head providing a length of about seven centimetres, henkelo is based upon
an exceptionally well-preserved specimen. As Kühne didn’t supply an adequate description
in 1968, the earlier generic name isn’t valid. Simpsonodon has subsequently been
reemployed for a docodont from the Middle Jurassic of
Oxfordshire.
The holotype was found in December 1976 by the Portuguese helper Graziela, at a time when no
scientists happened to be on site. Happily, the forewoman, Dona Encarnacao, recognised
there was more than a jaw present, despite the presence of an obscuring layer of black coal.
It was assumed to be a skull. However, when prepared the following year, most of the
skeleton also came to light. Further material was found on a small chip off the main block;
two fingers and some bones from the skull. Many of the remains are articulated, ie: still
joined together.
Skull and lower jaw
The skull represents a mosaic of 'ancient and modern' features. Still 'reptilian' are the
Meckelian groove, traversing the length of the lower
jaw, (some discussion on that is included with the entry for Dryolestes, below), and
a depression behind the rearmost molar, which is a point of
contact for a rudimentary coronoid, an extra lower jaw bone. However, the bones for the
typical reptilian jaw joint, the dentary-squamosal,
aren't visible. They had probably taken up their mammalian activities in the inner ear.
Certainly the petrosal, (the ear-casing of mammals), is
present and contains space for a spiralled cochlea. This is a thoroughly 'modern' feature
known from living mammals.
Teeth
The dental formula of Henkelotherium is somewhat closer to mammalian expectations,
than the eccentric obsession for molars shown by the dryolestids. Upper (probable): five
incisors, one canine, four
premolars and five-six molars.
Lower (probable): 4:1:4:6.
Limbs and lifestyle
The construction of the rear and front legs is more 'modern' than is the case for the extant
monotremes, which still display a propensity for
sprawling. Henkelotherium scampered around with a fully erect gait. Given the
build of its feet and tail, (long like those of a squirrel), it was possibly arboreal, (a
tree-dweller). For example, its claws suggest an agile acrobat, well versed in the art of
climbing up tree trunks and along branches.
Epipubic bones
The presence of epipubic bones, (aka marsupial bones), has
led to speculation that this critter might have raised its young in a pouch, (eg. Probst
1985 p.143.) However, this argumentation is dependant upon the primary purpose of these
bones being supports for a marsupium. Given that epipubic bones have a history stretching
back into pre-mammalian Therapsida, and that pouchless
marsupials and basal eutherians also have or had
them, this interpretation is unsustainable. It's more probable that the primary purpose
was as anchoring points for leg muscles. (Much of this entry is based upon Krebs 2000,
see Bibliography.)
Holotype
The holotype, IP-FUB Gui Mam 138/76, studies at the Freie Universität, Berlin. The specific
name refers to Guimarota.
In addition
In 2003, Ramón Vázquez Molinero presented a dissertation on Henkelotherium and
locomotion. It's presently accessible on-line at:
http://www.diss.fu-berlin.de/2004/12/.
The following notes are based upon it.
To sum up
The postcranial skeleton of Henkelotherium shares some broad characteristics with a
variety of living small mammals, regardless of their wider affinities, (p.6). As far as
they're known, the proportions of the spine and the asymmetrical build of the condyles on
the femur are similarities shared with some marsupials,
(didelphids aka opossums), and placentals, (tupaiids aka tree shrews). Despite not being
closely related, these extant mammals favour broadly equivalent living conditions. They're
generalists, making careers wherever they can. They have to deal with uneven ground,
clamber in bushes and even explore the trees, (p.7). Remains from Guimarota suggest an
ecosystem with dense vegetation, and that's a further similarity. While it may well have
been partially arboreal, it was also equipped for dealing with life at ground level.
Doing the Mesozoic mammalian locomotion
Leg bones provide useful clues as to how their former owners got around. You can tell a
dead horse used to be able to run more quickly than a cow, simply because of the way their
limbs are built. Much could be deduced even from ancient fossils. At least, this would be
possible if any were known. Until the discovery of Henkelotherium and
Haldanodon, the record for the Upper
Jurassic was less than very scant, (p.14). Discussions raged about whether the original
therians may have been tree- or ground-dwellers, and 'yes'
could have been a reasonable response to either option. They may have been.
However, when dealing with small animals, this demarcation is none too sharp. If there's
only seven centimetres of you, then there's virtually no such thing as flat earth. A
broadly similar repertoire of movements is required, no matter at what level your life is
mainly lived, (p.15).
Meet the panel
Molinero compared Henkelotherium with a range of existing mammals; five small marsups
and nineteen placentals. The volunteer
marsupials were South American opossums, (p.28). The
placental contingent was more diverse, but we're a much diverser group. It included mice,
a rat, a proper shrew, a couple of mini-primates, a mole, a desman, a squirrel, tree shrews
and more besides. Further specimens offered insights on the numbers of the
vertebrae.
As the author noted on page 17, several of the selected species are highly specialised.
For example, moles possess broad arm bones for digging, and desmans are aquatically
adapted. Such taxa were included so as to test for possible
specialisations in the Jurassic mammal.
Dimensions of Henkelotherium
As the head is only represented by fragments, a precise length can't be measured. However,
a mammal of this build with a body of 4.56 centimetres, would be expected to have a skull
of about 2cm, (p.41). Ignoring the tail, this leaves us with a critter of around 6.5 to
7cm, and an approximate weight of 15 to 20 grammes. As only part of the spine is preserved,
lengths are also a matter for estimation. Comparisons suggest the tail was probably about
twice as long as the body; ca. 9cm, (Table 3, p.56).
Uses for long tails
Tree-dwelling mammals often have long tails, and that was part of the reasoning for
comparing Henkelotherium with a
squirrel.,
(p.99). A prodigious tail can be a great help with balance and steering. Prehensile ones
can even provide a fifth limb. However, not only arboreal mammals find long tails useful.
An opossum called Sminthopsis longicaudata can justifiably be proud of its tail,
which is more than twice the length of the head and body combined. As it inhabits dry and
rocky terrain, it never catches sight of a tree, let alone lives in one. Nevertheless,
being small, this animal gets to do plenty of clambering and climbing. In Eurasia, the
harvest mouse has a tail of a similar relative length to the one owned by Henkelotherium,
and it's eminently prehensile. It comes in very handy for hanging onto grass stalks while
eating seeds. (A harvest mouse body can be less than three centimetres in length.) The
elephant shrew (Elephantulus brachyrhynchus) employs its impressive tail for balance
when running at high speed on flat ground, (although Henkelotherium lacks
specialisations for a similar mode of movement). A long tail doesn't necessarily indicate
an arboreal animal, (p.100).
Of the mammals questioned, proportions of the preserved spine in Henkelotherium
were similar to those found in the pen-tailed tree shrew, (Ptilocercus). This
animal dwells in the forests of Borneo and Sumatra, and nests have been found in the
treetops. This may be a closer analogue than a squirrel, as the latter are over three
times larger than the Jurassic animal. In relative terms, the tail is also a third
shorter, (p.101).
Like a tree shrew?
The slender and long nature of the caudal vertebrae leads
Molinero to suggest, that Henkelo used its tail in similar way to Ptilocercus; for
balance and steerage, as it moved among the branches and on the ground. Ptilocercus
is also known to derive a further benefit. Although about twice the size of
Henkelotherium, it still qualifies as small, and diminutive mammals have problems
retaining body heat. When sleeping, pen-tailed tree shrews have been seen with their tails
blanketed round their bodies, so as to maintain a cosy temperature. Whether 'Henkel's
beast' did anything of the kind is a matter for pure speculation, but it's rather
pleasing to imagine it did.
|
| References: | Krebs (1991), Das Skelett von Henkelotherium guimarotae
gen. et sp. nov. (Eupantotheria, Mammalia) aus dem Oberen Jura von Portugal. Berliner
geowiss. Abh., (A) 133, p.1-121. |
| Kühne (1968), Kimeridge (sic) mammals and their bearing on the
phylogeny of the Mammalia. In Drake E (ed) Evolution and Environment. Yale University
Press, p.109-123. |
| Links:
Ramón Vázquez Molinero
The abstract
Evolution of the locomotion of the primitive Theria as a precondition for the radiation of
modern mammals after the K/T boundary.
WDR Fernsehen, Der sechste Tag: Die Blütezeit der Säuger
http://www.quarks.de/leben2/06.htm
For non-German speakers, this report includes a photo of the fossil. It's based on the tv
programme, Quarks & Co.
Pfeil Verlag, Deutschland
http://www.pfeil-verlag.de/07pala/abb/2_80d8.pdf
Technical discussion on points of anatomy, (English). There’s a nice photo of the skull.
This is a page from Guimarota - A Jurassic Ecosystem, edited by Martin T & Krebs B,
2000. If I offer to write nice things about it, d'you think they'd send me a copy to review?
Too late. With thanks to Father Christmas for subsequently supplying one. |
| Genus: Paurodon Marsh OC,
1887 |
| Species: | Paurodon valens Marsh OC, 1887 |
| Place: | Morrison Formation, Wyoming |
| Country: | USA |
| Age: | Upper Jurassic |
| Remarks: | This critter had a small
diastema between the canine and first
premolar, (Carpenter 1998, p.401). The mouth was blessed
with the lower postcanine dental count of two premolars
and four molars per side, (p.402). |
| Reference: | Marsh (1887), American Jurassic Mammals. American J of Sci,
3, p.326-348, with pls. |
| Genus: Pelicopsis Simpson
GG, 1927 |
| Species: | Pelicopsis dubius Simpson, 1927 |
| Place: | Morrison Formation, Wyoming |
| Country: | USA |
| Age: | Upper Jurassic |
| Remarks: | Lives at the Peabody, Yale and was recruited by
the Reed-Como party of 1880.
A page appeared on the web with the following text: "Pelicopsis memoralis
loopt rond met Brachystomella parvula en Xenylla humicola tussen zijn
cheliceren." This was fairly puzzling, seeing as it's Flemish and concerns the
springtails
of Belgium. I've been reliably informed that there was a small typo involved. It should
have read Pelecopsis memoralis, and is apparently a springtail-loving spider. (Many
thanks to Frans Janssens for the information. And good luck to Bieke.)
Engelmann & Callison, 1998 (p.366) list this genus as a dryolestid based upon upper
teeth, rather than a paurodontid. However, on page 376: "Simpson (1929) and Prothero
(1981) suggested that Pelicopsis might represent one of the missing upper
dentitions of the paurodontids, in large part because of
the apparently short molar series in that taxon." |
| Reference: | Simpson (1927), Mesozoic Mammalia. VI. Genera of Morrison
pantotheres. Am. J. Sci. (5) xiii, p.409-416. |
| Genus: Tathiodon (Simpson
GG, 1927) Simpson, 1927
Aka : "Tanaodon" Simpson non Kirk, 1927 |
| Species: | Tathiodon agillis (Simpson, 1927) Simpson GG, 1927
|
| Aka: | Tanaodon agilis Simpson, 1927 |
| Place: | Morrison Formation, Wyoming |
| Country: | USA |
| Age: | Upper Jurassic |
| Remarks: | The holotype, collected by Reed WH in 1882, also
lives at Yale. Tanaodon is apparently a mollusc. Carpenter 1998 (p.402) offers the
postcanine tooth count of the
mandible as two premolars per side, accompanied by ?
molars. |
| References: | Simpson (1927), Mesozoic Mammalia. VI. Genera of Morrison
pantotheres. Am. J. Sci. (5) xiii, p.409-416. |
| Simpson (1927), Tathiodon, new genus, to replace Tanaodon Simpson
non Kirk. American J of Sci, 5, 71. |
| Other reports:
Fruita, Colorado, Morrison Formation
An undescribed new genus is mentioned in Wible et al, 2004, (p.21). |
A. Paurodontidae B. Dryolestidae
| Taxon: Dryolestidae Marsh OC, 1879
Aka: Amblotheriidae Osborn, 1887; Amblytheriidae Cope ED, 1889; Kurtodontidae Osborn, 1888;
Stylacodontidae Giebel, 1879; Stylodontidae Marsh OC, 1879
Though blessed with impressive nomenclature, this family consisted of unobtrusive meat
nibblers. Unfortunately, there’s been an awful lot of assigning, reassigning and
re-reassigning with some of these fossils. They’ve received various names, often from the
same workers, and even in the same years. I’ll try to avoid adding to the confusion, but it
won’t be easy.
Amongst the characteristics of the group are the roots of the lower
molars. The front one is enormous, whilst its posterior colleague is so weedy, that it
sometimes might get overlooked. The number of molars is also impressive.
placentals have up to three, whilst
marsupials can luxuriate with four. Dryolestids
wouldn't have dreampt of chewing with less than seven, and a few even went up to nine.
"At the posterior end of the molars of the lower jaw, a small cusp is found, which is
called the talonid."
"The small size of the talonid indicates that the Dryolestidae do not represent the
lineage that includes the direct ancestors of the modern mammals. Mammals with a
significantly enlarged talonid already lived alongside the dryolestids. These mammals,
which are known as "peramurids", are represented in the Guimarota mine by a
primitive and very small form."
Both quotations come from Guimarota - A Jurassic Ecosystem, (p.111). This page is on-line
and linked to the entry on Dryolestes leiriensis.
The dryolestids of the Upper Jurassic Morrison Formation might appear to be extraordinarily
diverse. However, this is somewhat artificial. Upper and lower
dentitions have received separate generic names over the years. As mammalian mouths
have a tendency to contain teeth on both jaws, some of these remains must represent the
same animals, (Engelmann & Callison 1998, p.366).
South American Upper Cretaceous?
If assignments are correct, the family went on to enjoy a late blossoming in Upper Cretaceous
Patagonia. Several genera from there have been referred. However, whether that opinion
will withstand the test of time is another matter. Still, I'll leave the relevant entries
here until justification is available for placing them elsewhere. That's already happened
for Groeberitherium. It was originally
referred to the family but then got flung out by Rougier et, 2008 (a study that was
officially published in 2009). |
| Link:
Mikko Haaramo’s Dryolestidae
Mikko Haaramo’s Dryolestidae
Genera: Achyrodon (= Amblotherium), Alamitherium,
Amblotherium, Asthenodon (= Dryolestes),
"Athrodon" (= Kurtodon), "Butlerigale"
(= Dryolestes?), Crusafontia, Curtodon
(= Kurtodon), Cyrtodon (= Kurtodon),
Dryolestes (partly = Amblotherium), Guimarotodus,
Herpetairus (= Dryolestes / Laolestes),
Kepolestes (= Amblotherium), Krebsotherium,
Kurtodon, Laodon (= Amblotherium),
Laolestes (partly = Amblotherium / Dryolestes /
Leonardus, Malthacolestes (= Laolestes),
Melanodon (= Laolestes), Miccylotyrans,
Odontostylus (= Amblotherium), Parungulatum,
Peraspalax, Phascolestes,
Portopinheirodon,
Rougiertherium, Stylacodon (= Amblotherium / Dryolestes),
"Stylodon" (= Amblotherium), "Trouessartia"
(= Amblotherium), Trouessartiella (= Amblotherium),
other reports
Remarks: !!!???!!!
Time-Line:
Upper Cretaceous: Alamitherium, Dryolestes tenax,
Leonardus, Paraungulatum, Rougiertherium
Lower Cretaceous: Crusafontia, Kurtodon, ?Peraspalax,
Phascolestes, English Wealden
Upper Jurassic: Amblotherium (Wyoming), Dryolestes, Guimarotodus,
Krebsotherium, Laolestes, Miccylotyrans, Portopinheirodon |
| Genus: Alamitherium
Bonaparte JF, 1999
'Alamitos beast' |
| Species: | Alamitherium bishopi Bonaparte JF, 1999 |
| Place: | Los Alamitos Formation,
Patagonia |
| Country: | Argentina |
| Age: | Upper Cretaceous |
| Remarks: | With thanks to Mikko Haaramo. |
| Reference: | Bonaparte (1999), New Dryolestida (Theria) from the Late
Cretaceous Los Alamitos Formation (Argentina) and paleogeographical comments in Leanza,
H. A., (ed.) 1999: Abstracts of VII Int. Symposium on Mesozoic Terrestrial Ecosystems.
Buenos Aires, 1999, A1-A65. |
| Genus: Amblotherium
Owen R, 1871
Aka: Archyrodon Owen R, 1871; Dryolestes (partly); Kepolestes Simpson
GG, 1927; Laodon Marsh OC, 1887; Laolestes (partly); Odontostylus
Trouessart, 1898; Stylacodon sp. Marsh OC, 1879; "Stylodon" Owen R,
1866; "Trouessartia" ('for Trouessant') Crossman, 1899;
Trouessartiella Crossman, 1899
Remarks: Many names for a 25cm critter based on lower teeth. "Amblotherium is
a taxon based on the lower
dentition. It is distinguished from the other dryolestid lower dentitions primarily by
the more upright paraconid. This may be a primitive character within the group and may
result in incorrect groupings of species. Amblotherium is the only dryolestid
common to the Morrison and the Purbeck Beds in England perhaps for this reason",
(Engelmann & Callison 1998, p.369).
Trouessartia Canestrini, 1899, is a some kind of bird-annoying mite.
References:
For Amblotherium: Owen (1871), Monograph of the fossil Mammalia of the Mesozoic
formations. Palaeontolographical Soc, xxiv, p. 1-115, pls. i-iv.
For Laodon: Marsh, (1887), American Jurassic mammals. Amer J Sci 3, p.326-348, with
pls.
For Stylacodon: Marsh, (1879), Notice of a new Jurassic mammal. Amer J Sci 3, p.60-61.
| Reassigned species: A. debilis Simpson, 1927 see A. gracilis | |
| Species: | Amblotherium gracilis (Marsh OC, 1879) |
| Aka: | Amblotherium debilis Simpson, 1927; Dryolestes gracilis Marsh, 1881;
Kepolestes coloradensis Simpson, 1927; Laodon venustus Marsh, 1887;
Laolestes elegans Simpson GG, 1927; Stylacodon debilus; Stylacodon
gracilis Marsh, 1879 |
| Place: | Morrison Formation, Wyoming,
Dinosaur National Monument and Colorado |
| Country: | USA |
| Age: | Upper Jurassic |
| Remarks: | Some material is the AMNH collection, New York,
(AMNH 105166). There’s more at Yale, including the type fossil.
A. debilis is listed as a species in the review by Engelmann & Callison, 1998,
(p.366), though Lillegraven, 2000 reports both it and Kepolestes coloradensis as
junior synonyms. |
| Reference: | Simpson (1927), Mesozoic Mammalia. VI: Genera of Morrison
panthotheres. Amer. J. Sci 5, p.409-416. |
| Species: | Amblotherium nanum (Owen R), 1871 |
| Place: | Durlston Bay, Dorset |
| Country: | England |
| Age: | Lower Cretaceous |
| Remarks: | |
| Reference: | Owen, (1871), Monograph on the fossil Mammalia of the Mesozoic
formations. Palaeontological Society Monograph, 24, p.1-115. |
| Species: | Amblotherium pusillum (Owen), 1871 |
| Aka: | A. pusillus; "Stylodon pusillus" Owen R,
1866 |
| Place: | Durlston Bay, Dorset |
| Country: | England |
| Age: | Lower Cretaceous |
| Remarks: |
There are two valid biological genera called Stylodon; a
snail, (which also suffers from parasitical nematodes), and a plant. This is allowed, and
should anyone ever be tempted to try and unify the nomenclature of botany and zoology, don’t.
Oolitic, mentioned in the reference, refers to a form of limestone.
The specific name pusillum is in Table 2 of Savage, 1989 (p.5). pusillus
also gets used but the first version seems to be in widest use, as it's also favoured by
Ensom & Sigogneau-Russellm 1998 (p.51). |
| Reference: | Owen (1866), Description of part of the lower jaw and teeth of
a small oolitic mammal (Stylodon pusillus Ow.). Geol Magazine 1, p.199-201, with pl.
x. |
| Owen, (1871), Monograph on the fossil Mammalia of the Mesozoic
formations. Palaeontological Society Monograph, 24, p.1-115. |
Seven Phases of Teeth
(Postcanines)
V Dryolestidae
The following is derived from and inspired by my reading of Butler & Clements, 2001,
(p.14).
Dryolestids were fanatics for molars. With up to nine, plus
four premolars, four
incisors and a canine per side, they'd make The Osmonds
look edentulous. Taking into account both jaws, that
makes 72 teeth. Assuming no wisdom teeth, (which sounds like a safe bet), that's only a
dozen less then Donny, Marie and Little Jimmy Osmond combined. And dryolestids could
probably have sung better too.
"The large number of molars in dryolestids is correlated with mesiodistal compression
of the individual molars; the metaconid was shifted directly
lingual to the protoconid and the talonid was reduced
to a transverse ledge."
Based on juvenile specimens from Guimarota, Portugal, the replacement pattern was broadly
similar to that known from eutherians. All premolars were
diphyodont including the upper P1. The youngest
individuals already had the m1 lower molar. In one specimen a lower milk tooth (dp4) shows
much wear, so it must have done a fair amount of work. The lower premolars erupted in a
particular sequence: p1-p3-p2-p4. The p1 broke through at much the same stage as m3, whilst
p4 came on-line after m5. The final milk tooth (dp4) was
molariform, as was dp3 to a lesser degree, and their replacements had less complex
crowns. In the uppers, P1 erupted first and it replaced a
deciduous tooth. That detail is in contrast to most eutherians, which have a
monophyodont tooth in that position.
Most paurodontids had a more modest four or five molars, though the type specimen of
Henkelotherium had seven lowers. The m7 was much reduced and single-rooted. This
genus had four lower premolars. Most its paurodontid colleagues had relatively short
dentaries, which helps to account for their more reticent
tastes in molars.
Go to Phase: I Carnivorous non-mammalian cynodonts,
II Basal mammals,
III Kuehneotheriids (basal Holotheria),
IV Cladotheria,
V Dryolestidae,
VI Amphitheriida and Zatheria,
VII Tribosphenic dentition. |
| Genus: Butlerigale Kühne
'Butler's weasel' |
| Species: | "Butlerigale sp." Kühne |
| Place: | |
| Continent: | Portugal |
| Age: | Upper Jurassic |
| Remarks: | "Martin considers
"Butlerigale" of Kühne, originally a nomen nudum, as a possibly
pathological variant within the species limits of Dryolestes leiriensis",
(Lillegraven, 2000). This is contained in a review of a German language paper by Thomas
Martin, 1999. For the while, it seems best to leave this entry open. |
| Reference: | |
| Genus: Crusafontia Henkel
S & Krebs B, 1969
'For Crusafont'
Remarks: Sgr. Crusafont undoubtedly earned the honour, though I know not how. |
| Species: | Crusafontia cuencana Henkel & Krebs, 1969 |
| Place: | Castellar Formation - Camarillas Formation, Galve |
| Country: | Spain |
| Age: | lower Barremian, Lower Cretaceous |
| Remarks: | This genus supposedly features in Benton, MJ
1991b (p.36-37). The book is for the general market, doesn't delve into great detail
but includes a fine photo on page 37. As the author is a professor of vertebrate
paleontology, and I happen to have been an admirer of his writing for years, I was
pleased to have the benefit of his expertize when I found the book in a shop on
Christchurch High Street in August, 2006. The photo's
impressive and it was a charity shop. Such establishments rarely contain treasures
of relevance to Mesozoic eucynodonts, but it can happen occasionally.
Whops!
The text informs me that Crusafontia was around 20cm long, is known from an
unusually well-preserved partial skeleton, and it looks like a stunner. I'm also
informed the owner lived during the Upper Jurassic and was recovered from coal deposits
at Guimarota in Portugal. Given that Crusafontia is actually known to speak
Spanish with a Lower Cretaceous accent, those details were rather puzzling.
I had reason to check Mike Benton's book again in 2008 and, conveniently, I happened to
do so in close proximity to a different book on the fossils of Guimarota. As that also
contains photos of mammal specimens, I thought a comparison would be a good idea. Laying
two photos side by side, I couldn't help notice the extraordinary resemblance between
them. This is best explained by them being photos of the same specimen.
Rather than being Crusafontia, as repeatedly stated in Benton 1991b, that fossil
is without any doubt whatsoever the holotype of
Henkelotherium. Its actual body-head length is perhaps as long as 7cm and,
allowing for a most extravagant tail of perhaps 9cm, I can't imagine how that approximates
to about 20cm.
Sadly, that still leaves me lacking much reliable information on this genus. Everybody
makes mistakes. However, some are more spectacular than others. Giving a holotype an
entirely wrong generic name in print is best avoided, and the detail that it was a book
aimed at general readers, rather than the initiated, doesn't constitute a mitigating
circumstance. The public should be able to have reasonable trust in what the author is
telling them. Unfortunately, I showed too much trust back in 2006. |
| Reference: | Henkel & Krebs (1969), Zwei Säugertier-Unterkiefer aus der
Unteren Kreide von Una (Prov. Cuenca, Spanien). Neues Jahrbuch für Geologie und Paläontologie,
Monatshefte 8, p.449-463. |
| Species: | Crusafontia amoae Cuenca-Bescos G, Badiola A, Canudo JI,
Gasca JM & Moreno-Azanza, M, 2011 |
| Place: | Cuesta Corrales 2, Galve |
| Country: | Spain |
| Age: | upper Hauterivan - lower Barremian, Lower Cretaceous |
| Remarks: | This second species is based upon a couple of isolated
upper molars.
Holotype
The type specimen, MPZ CC2-1, is an upper left molar residing in the collection of the Museo de
Paleontología at the University of Zaragoza. The specific name honours the now deceased
paleontologist Olga Amo. |
| Reference: | Cuenca-Bescos et al (2011), New dryolestidan mammal from the
Hauterivian–Barremian transition of the Iberian Peninsula, Acta Palaeontologica Polonica, 56(2).
p.257-267. |
| Genus: Dryolestes Marsh OC,
1878
'tree robber'
Aka: Asthenodon Marsh OC, 1887; Herpetairus Simpson, 1927; ? Laolestes
(partly); Stylacodon (partly)
Remarks: A fully equipped Dryolestes mouth was apparently blessed with 68 teeth.
Some material originally included in this genus was subsequently reassigned to
Amblotherium, Docodon and even Laolestes.
Reportedly, the usual translation of the Greek word drys as oak is not in line with Marsh’s
usage, although it’s not wrong as such. Tree is apparently what was meant.
Thomas Martin concluded that Herpetairus represents the upper
dentition of this genus, which makes it a junior synonym,
(Lillegraven, 2000).
| Reassigned species: D. arcuatus Marsh, 1879 see D. priscus;
D. gracilis Marsh, 1881 see Amblotherium
gracilis | |
| Species: | Dryolestes leiriensis Martin T, 1999 |
| Place: | Guimarota |
| Country: | Portugal |
| Age: | Kimmeridgian, Upper Jurassic |
| Remarks: | The following is based upon my reading of Martin,
2000.
In terms of individual numbers, dryolestidans are the best represented mammals in the
Guimarota fauna. About 500 jaws and skull parts have been recovered for two families;
Dryolestidae and Paurodontidae, (p.109). Although these animals were more
derived than many of their contemporaries, they retained
archaic characteristics. (Coming to think of it, so do I, but less of them.) A developed
protocone wasn't present on the upper molars, and the lowers
lacked a basined talonid.
Dryolestids
Dryolestid molars tend to be short, broad and numerous. Rather than enhancing efficiency
through increased sophistication, the main approach used by this group was an increase in
quantity. D. leiriensis has this typical characteristic. It's the most common
representative from the location, and is relatively large. These kind-hearted insectivores
have donated nearly ninety jaw to posterity. As the genus was first reported from the
Morrison Formation of North America, its presence in
Europe could be puzzling. However, it's a consequence of ancient geography, when the
Atlantic was more pond than ocean-sized. Various taxa are
shared by both Portugal and the Morrison, including an obscure critter called
Allosaurus.
Lower jaw
The dentary of this species reaches about 3.5cm in length,
and that roughly equates to a
hedgehog. Unlike most of its contemporaries, this mammal was large enough to perhaps
be noticeable. An impressive feature is the large coronoid process towards the back, which
is an area for muscle attachments. As with modern mammals, there's an angular process at
the rear of the jaw. This characteristic doesn't occur in
multituberculates and more
basal lines such as docodonts.
The lingual side of the mandible contains a shallow
Meckelian groove. Another archaic touch is at the
base of the coronoid process. A triangular impression attests to the attachment of an
'extra' bone; a coronoid. No living mammal would dream of having such a thing on their
lower jaw, but they're popular with other tetrapods. In Dryolestes, this was
ancient luggage waiting to get lost. Two parallel depressions at the end of the Meckelian
groove may also indicate a further vestigial bone; the splenial, (p.112).
Dental formula
Each side of the jaw boasted: (uppers): five incisors, one
canine, four premolars and
at least six molars; (lowers): four, one, four and eight
respectively.
Lower teeth: incisors
The first two weren't far from pointing horizontally forwards, (p.110). Procumbent lower
incisors are common enough in mammals, though they're more
procumbent than most with Dryolestes. This is about function rather than fashion.
Such teeth are often employed for fur care. The first incisor is by far the longest, and
they become progressively more vertical along the tooth row.
Canine
The canine is also somewhat procumbent, It's large and
anchored by two big roots. The rear one is huge and reaches down nearly to the bottom edge
of the jaw. The cusp of the crown is triangular and curves inwards, perhaps in order to
guide food items towards the delights of the chewing experience, (p.111). The only other
tooth to approach the canine in height is the fourth premolar.
Premolars
The four premolars are also held in place with a pair of
enormous roots. The first two teeth are fairly small, and the p4 is the largest. They all
come provided with an extra small cusp at the back. These teeth were for holding and
killing welcome guests.
Molars
All the molars are smaller than the p4. Given the prodigious
number, this is hardly surprising. Eight molars are usual in this species and they had to
be packed into a space, in which many contemporaries would have stored five teeth or less.
There are three main cups, with the protoconid dominant
among and on the labial side. The arrangement is
triangulated. Each molar has a talonid heel at the back.
However, it's very small and can't be ancestral to the basined talonid of
tribosphenic molars. That more efficient model was
already under development in the north. (It had already arrived in the south; eg.
Ambondro.) No wonder dryolestid days were
numbered, it might be said. Actually, weird relatives in South America went on to survive
beyond 'The Age of the Dinosaurs'; eg. Peligrotherium.
What's for dinner?
The prevailing flavour of dryolestid dentition is sharp.
The teeth are particularly pointy, and that's a point to that. This is dentition for
dealing with insects, (p.112). "The power produced by the jaw muscles is
concentrated on the points of the tooth cusps, resulting in a very high pressure there.
Thus, the cusps can puncture the hard chitinous shell of insects, like the serrations of a
tomato knife puncture the smooth skin of a tomato before the actual cutting process
starts."
Microscopic examination of the molars can reveal signs of wear, and these are set slightly
to the diagonal. This is the result of some sideways movement of the jaws during chewing.
This is in contrast to the mechanics of reptilian jaws, which generally can only operate
vertically, (orthal). The forces produced by the transverse movement may account for the
extraordinarilly deep roots, (p.113), on such relatively low crowned teeth.
Tooth replacement
Nine dryolestid jaws in the collection contain at least some milk teeth, so they're from
juveniles. Seven are lower mandibles, (p.116). These
show that tooth replacement was broadly similar to the usual
placental scheme. (Marsupials are more
specialised in this regard. Only the third premolars are replaced.) Like me, dryolestids
replaced all their teeth once except for molars.
As they had shorter jaws, the juveniles had less molars. Often, only one or two are in
place, and the others erupted later as space became available. At least, they would've if
death hadn't intervened.
Skull and upper dentition
All remains of the head are fragments, (p.113). These include part of a snout. The
premaxilla shows the end of the muzzle was rounded, and
there are four alveoli for single-rooted
incisors. However, a further fragment reveals there was a
fifth of these teeth located in the maxilla. As maxillary
incisors don't occur in living mammals, this is a basal
characteristic.
The upper canine is large and double-rooted. The foremost
pair of premolars are rather pathetic, but the rear two are
larger. As with the lowers, the molar crowns have a triangulated arrangement of cusps, but
the apex is on the lingual side. This opposed triangulation
enhanced cutting ability. There's a significant difference to more
derived upper molars, in that the cones are a stylocone,
a metacone and a paracone. The stylocone on modern teeth is much reduced, and there's a
strong protocone instead. This isn't a matter of different jargon. The two structures
aren't homologous.
Body
A few bits are known. Among the fossils is a humerus with
a length of 1.7cm, (p.114). It probably comes from Dryolestes, as that's the only
mammal in the fauna of an appropriate size. The attachment points indicate the presence of
powerful muscles.
Holotype
The holotype is a lower left mandible known as Gui Mam 130/74. The specific name honours
the town of Leiria. The fossil site is on the outskirts. |
| Reference: | Martin (1999), Dryolestidae (Dryolestida, Mammalia) aus dem
Oberen Jura von Portugal. Abhandlungen der Senckenbergischen naturforschenden Gesellschaft
550, p.1-119. |
| Link:
Pfeil-Verlag, Deutschland
http://www.pfeil-verlag.de/07pala/abb/2_80d7.pdf
Fairly complex anatomy with a photo of the holotype. This is another page from Guimarota -
A Jurassic Ecosystem, edited by Martin T & Krebs B, 2000. Although the editors, authors
and publishers are predominantly German, due to economic realities, this book was produced
in English. Spare a thought for non-native-English speaking paleontologists, students and
hobbiers everywhere. |
| Species: | Dryolestes obtusus Marsh OC, 1880 |
| Place: | Morrison Formation, Wyoming |
| Country: | USA |
| Age: | Upper Jurassic |
| Remarks: |
Specimen at Yale. The collector is named as Marsh. At some time, material from this species
has also been referred to Herpetairus and Melanodon. |
| Reference: | |
| Species: | Dryolestes priscus Marsh OC, 1878? or 1887? |
| Aka: | Asthenodon segnes Marsh OC, 1887; Dryolestes arcuatus
Marsh OC, 1879; Herpetairus arcuatus (Marsh OC, 1879); Herpetairus humillis
Simpson GG, 1929; Laolestes elegans Simpson GG, 1927; Stylacodon validus
Marsh OC, 1880 |
| Place: | Morrison Formation, Wyoming
and Dinosaur National Monument |
| Country: | USA |
| Age: | Upper Jurassic |
| Remarks: |
Confusing and also in the Peabody, Yale. Laolestes grandis Simpson GG, 1929 has also
been referred to Dryolestes sp., Herpetairus arcuatus seems to have been a
re-diagnosis of D. arcuatus, which then became D. priscus!
This may in part or wholly be Laolestes eminens Simpson, 1927. However, Engelmann
& Callison, 1998, list it as a separate species based upon lower teeth, (p.367). |
| References: | Marsh (1878?), Fossil mammal from the Jurassic of the Rocky
Mountains. Amer. J Sci 3 p.459. |
| Marsh (1887?), American Jurassic mammals. Am. J. Sci. (3) xxxiii,
p.326-348. |
| Species: | Dryolestes tenax Marsh OC, 1889 |
| Place: | Lancian Formation, Wyoming |
| Country: | USA |
| Age: | Upper Cretaceous |
| Remarks: | A Peabody holotype. Bewildering age. It was
collected by Hatcher JB in 1889, whatever it actually might be. |
| Reference: | Marsh (1889), Discovery of Cretaceous Mammalia. Am. J. Sci.
(3) xxxviii, p.81-92. |
| Species: | Dryolestes vorax Marsh OC, 1879 |
| Aka: | at least partly = Dicrocynodontidae indet. = Docodon sp.
|
| Place: | Morrison Formation, Wyoming |
| Country: | USA |
| Age: | Upper Jurassic |
| Remarks: | Peabody |
| Reference: | |
| Species: | Dryolestes |
| Aka: | Herpetairus arcuatus |
| Place: | Morrison Formation, Colorado
and Dinosaur National Monument |
| Country: | USA |
| Age: | Upper Jurassic |
| Remarks: | These upper molars are relatively large. They
were described under the name of H., which is a junior synonym of D., (as
reported in Lillegraven, 2000). |
| Reference: | |
| Species: | Dryolestes |
| Aka: | Herpetairus humilis |
| Place: | Morrison Formation, Colorado |
| Country: | USA |
| Age: | Upper Jurassic |
| Remarks: | Described as H., this genus is a junior
synonym of Dryolestes, (as reported in Lillegraven, 2000). |
| Reference: | |
| Genus: Guimarotodus
Martin T, 1999 |
| Species: | Guimarotodus inflatus Martin T, 1999 |
| Place: | Guimarota |
| Country: | Portugal |
| Age: | Kimmeridgian, Upper Jurassic |
| Remarks: | This is a robust representative based upon a few
fragments of lower jaw. The name of the species reflects an 'inflated' cusp, (the
metaconid). This is relatively long and chisel-like, rather than pointed, suggesting a
diet of hard prey, (eg. armoured insects or snails.)
One specimen contains a heavily abraded fifth premolar,
though morphological differences to its dental colleagues indicate this is an obstinate
milk tooth.
The holotype is Gui Mam 9/75. The specific name refers to the inflated appearance of the
metaconid, which is long and chisel-like rather than
pointed. |
| Reference: | Martin (1999), Dryolestidae (Dryolestida, Mammalia) aus dem
Oberen Jura von Portugal. Abhandlungen der Senckenbergischen naturforschenden Gesellschaft
550, p.1-119. |
| Genus: Krebsotherium
Martin T, 1999
'Krebs' beast' |
| Species: | Krebsotherium lusitanicum Martin T, 1999 |
| Place: | Guimarota |
| Country: | Portugal |
| Age: | Kimmeridgian, Upper Jurassic |
| Remarks: |
The jaw of Krebsotherium is about 2,5cm long, which is somewhat smaller than in
Dryolestes, which suggests a largish shrew-size. The teeth are also pointier.
Of interest to people who can understand this sort of thing, (which excludes myself), the
enamel microstructure presented "the discovery of the earliest enamel prisms known in
mammals", (Martin 2000, p.114). If the enamel crystals are bundled up into prisms,
rather than being more evenly distributed, then the covering is apparently strengthened.
In the light of Wood et al, 1999, I think I should add a qualification to the above. 'The
earliest enamel prisms' is clearly dependent upon the definition of prism employed. In a
more basal form, plesiomorphic prismatic enamel is present in
the non-mammalian genus, Pachygenelus, and the basal mammal, Megazostrodon,
(p.178). This condition is also known from various other critters including several
dryolestids, (eg. Laolestes, (p.189).
The holotype is Gui Mam 9/75. |
| Reference: | Martin (1999), Dryolestidae (Dryolestida, Mammalia) aus dem
Oberen Jura von Portugal. Abhandlungen der Senckenbergischen naturforschenden Gesellschaft
550, p.1-119. |
| Genus: Kurtodon Osborn HF,
1887
Aka: "Athrodon" (preoccupied by a fish); Curtodon Zittel, 1892;
Cyrtodon Winge, 1893
Remarks: Savage, 1989 gives the year of publication as 1888, (p.5). |
| Species: | Kurtodon pusillus Osborn HF, 1887 |
| Place: | Durlston Bay, Dorset |
| Country: | England |
| Age: | Lower Cretaceous (or possibly Upper Jurassic. It's borderline). |
| Remarks: |
If you'd like to check your copy, the 1911 edition of the Encyclopedia Britannica includes
this, (according to the on-line version):
"As regards the affinities of the creatures to which these jaws belonged, Professor
Osborn has referred the Triconodontidae and Amphilheriidae (!), together with the
Curiodontidae (!) (as represented by the English Purbeck Curtodon), to a
primitive group of marsupials, while he has assigned the Amblothersidae (!) and
Stylacodontidae to an ancestral assemblage of Insectivora. On the other hand, in the
opinion of Professor H. Winge, a large number of these creatures are primitive
monotremes. Besides the above, in the Trias of North
America we have Drornothereum (!) and Microconodon, extremely
primitive forms, representing the family."
Some of that spelling is decidedly eccentric. With the benefit of hindsight, both
professors were incorrect.
Cyrtodon (Brown R) Hooker WJ, 1833 is a genus of moss. |
| Reference: | Osborn (1887), Note on the genus Athrodon. Amer.
Naturalist, XXI, p.1020. |
| Link:
MARSUPIAL MOLE
http://51.1911encyclopedia.org/M/MA/MARSUPIAL_MOLE.htm
In case you've misplaced your 1911 Britannica, here's the item concerned. It's of some
interest, although mammal paleontology has moved on a long way since. This page comes
equipped with a great many banners. |
| Genus: Laolestes Simpson GG,
1927 - Melanodon Simpson GG, 1927
L. '?' - M. 'black tooth'
Aka: Herpetairus (partly); Malthacolestes Simpson, 1927; Melanodon Simpson,
1927
Remarks: McKenna & Bell, (1997), lists this as a synonym for Melanodon, as well
as being a valid genus. However, Lillegraven (2000) states that L. is "the
senior genus". I've included a couple of very possibly non-existent M. species
with this genus.
Laolestes is based on lower teeth, whilst Melanodon represents the upper,
(see Engelmann & Callison 1998, p.366 and p.377).
| Reassigned species: L. elegans Simpson, 1927 see
Amblotherium gracilis / Dryolestes
priscus | |
| Link:
Brasil ou Terra dos Papagaios
http://www.geocities.com/RainForest/Andes/8032/page15.html
Hmmm. According to the title, this Portuguese language article is about Brazil, the land of parrots.
And it features some pretty poly pics. However, Melanodon gets a mention. I’m not
quite sure why. McKenna & Bell, 1997 cites Malthacolestes as a synonym of that
genus, which is in turn Laolestes. |
| Species: | Laolestes andresi Martin T, 1999 |
| Place: | Porto Pinheiro |
| Country: | Portugal |
| Age: | Upper Jurassic (or Lower Cretaceous) |
| Remarks: | This is reported in Lillegraven, 2000. |
| Reference: | Martin (1999), Dryolestidae (Dryolestida, Mammalia) aus dem
Oberen Jura von Portugal. Abhandlungen der Senckenbergischen naturforschenden Gesellschaft
550, p.1-119. |
| Species: | Laolestes eminens (Marsh) Simpson GG, 1927 |
| Aka: | Dryolestes priscus Marsh OC, 1878? or 1887? |
| Place: | Morrison Formation, Wyoming |
| Country: | USA |
| Age: | Upper Jurassic |
| Remarks: | L. elegans was based on Dryolestes
fossils. The one time Laolestes now seems to be split across at least four genera,
(Amblo, Dryo, Lao and Melano). However, L. eminens does still seem to be regarded
as valid, (eg. Engelmann & Callison 1998, p.366). If you’d like to investigate this
personally, they’ve got some teeth at Yale. |
| Reference: | Simpson (1927), Mesozoic Mammalia. VI. Genera of Morrison
pantotheres. Am. J. Sci. (5) xiii, p.409-416. |
| Species: | Laolestes goodrichi (Simpson GG, 1929) |
| Aka: | Herpetairus humilus Simpson, 1929; Melanodon goodrichi
Simpson, 1929 (or 1927 according to Biosis) |
| Place: | Morrison Formation, Wyoming |
| Country: | USA |
| Age: | Upper Jurassic |
| Remarks: | Laolestes is favoured at the Peabody
although, with a view to heightening the confusion, the holotype of Mela goodrich is listed
separately. A short history of the specimen known as Lao: Found by the Reed-Como party in
1881. Later described as Melanodon cf. goodrichi, Herpetairus humilus
Simpson, 1929, Melanodon goodrichi Simpson, 1929 and Laolestes goodrichi
(Simpson, 1929). Take your pick. |
| Reference: | Simpson (1929), American Mesozoic Mammalia. Mem. Peabody Mus.
Nat. Hist. iii (i), p.1-235. |
| Species: | Laolestes grandis |
| Place: | Morrison Formation, Wyoming |
| Country: | USA |
| Age: | Upper Jurassic |
| Remarks: | This species is mentioned by Engelmann &
Callison, 1998, (p.366), so I presume it's seen as useful. |
| Reference: | |
| Species: | Loalestes oweni (Simpson GG, 1927) |
| Aka: | Malthacolestes osborni Simpson GG, 1927; Melanodon oweni
Simpson GG, 1927 |
| Place: | Morrison Formation, Wyoming |
| Country: | USA |
| Age: | Upper Jurassic |
| Remarks: | Laolestes has precedence at the Peabody,
with a reference to Martin T, 1999. Collected by Reed WH in 1880 & 1881. Engelmann
& Callison, 1998 (p.366) refer this species to Melanodon, but the referral back
to L. postdates that.
Malthacolestes was based on upper milk teeth. |
| Reference: | Simpson (1927), Mesozoic Mammalia. VI. Genera of Morrison
pantotheres. Am. J. Sci. (5) xiii, p.409-416. |
| Mammals of the Morrison Formation, Upper
Jurassic
The first part of the following is based upon my reading of Engelman & Callison, 1998.
If you develop an interest in Mesozoic terrestrial vertebrate paleontology, (dinosaurs and
all that jazz), it won't be long before you've read some complicated terminology and
become acquainted with some of the former residents of the Morrison Formation. Even if you
think that might be an early reference to The
Doors, ("Come on baby light my fire..."), Diplodocus, and
Stegosaurus would still be famous enough to be panellists on celebrity game shows.
And the presence of Allosaurus would transform such programmes into events, rather
than electronic wallpaper accompanied by irksome wittering. However, this classic Upper
Jurassic area of North America wasn't all about dinosaurs. There were many other animals
about too, a fair few of which were furry.
The Brushy slice
A layer of the Morrison Formation is known to its friends as the Brushy Basin Member,
(p.343), and this has yielded mammals in three States of
the Union. The most diverse mammalian faunas have been found in Como Bluff Wyoming, Fruita
Colorado and Dinosaur National Monument Utah. (Those latter two are west of the Rockies,
which will be of some significance shortly, so bear it in mind.) The haul from Como Bluff
includes triconodonts,
docodonts, multituberculates,
'symmetrodonts' and two families of
dryolestoideans, (dryolestids and paurodontids). All
these funny names refer to mammals.
Although geographically widespread, the Morrison Formation represents a relatively short
geological interval, (Upper Oxfordian - Lower Tithonian according to Carpenter 1998, p.393,
which is something like six million years). Mammal fossils aren't commonly found, but page
344 reports seven sites, (or constellations of sites). All are located in the Upper Brushy
Basin Member (or equivalents, p.345), with the exception of Garden Park in Colorado. The
few specimens from there are slightly older; Lower Brushy Basin. The study then turns its
attentions to systematical considerations and descriptions of new material, which explains
my abrupt leap to the Faunal Comparisons on page 377.
Fruita and Dinosaur National Monument have both yielded partial skulls of a then
undescribed multituberculate and seemingly the same triconodonts. However, in contrast to
Como Bluff, Laolestes-Melanodon and docodonts haven't been found. As all three sites
have been well sampled, this isn't likely to be due to a collecting bias. Their absence is
more probably an effect of either stratigraphic or geographic differences. Unlike the first
two localities, Como Bluff is east of the Rockies. Both these groups are represented at
locations even further to the east; in Europe. Docodonts are also present in the more
limited remains from Garden Park and Black Hills, which are also on the eastern side of the
mountains.
European allies
I confess that the authors didn't mention the presence of Laolestes-Melanodon or
docodonts from Upper Jurassic and Lower Cretaceous sites in Europe. However, Laolestes
from Portugal hadn't then been published, Docodon fossils from Dorset aren't
well-preserved, and a solitary tooth from England referred to Melanodon is of a
significantly more recent age. Perhaps due to a lack of psychic abilities, their list of
taxa common to both the Morrison and Portugal-England is
restricted to: Trioracodon,
Ctenacodon and
Amblotherium. (The listing on p.378 is qualified with the word 'notably', and so
it wasn't meant to be complete.)
It's possible that these apparently 'common' taxa may have something to do with the
difficulties posed by precise identification. For example, well-qualified scepticism has
been expressed regarding the actual presence of Ctenacodon in the Purbeck fauna of
Dorset. But, and as testimony to the benefits of hindsight, I've heard of no such doubts
concerning the subsequent identification of oodles of Dryolestes specimens from
Guimarota
(Kimmeridgian) or Laolestes at Porto Pinheiro. Consequently, there do seem to be
genera common to both regions.
Remains of a menu for Upper Jurassic insectivores
In his 1999 study, (see Bibliography), Stephen Hasiotis gives some indication of the
diversity of delicacies available for the hungry mammals of Como Bluff. Whilst insect
fossils might not be abundant there, fossilized traces of their activities, (ichnofossils),
are. Known from Como Bluff and similar locations in the Morrison Formation are the nests
of at least four kinds of termite, the same number of varieties of ant nest, three forms
of bee nest, wasp cocoons, at least five types of beetle burrow, as well as signs of active
dung beetles and grubs.
This paper recognizes nine intervals in the Formation, numbered 1 (earliest) to 9 (latest),
and summarized the age of disposition to between about 155-145 million years ago. Como
Bluff, a source of various mammals on this and further directories, is included in intervals
1-5.
Further Mesozoic site summaries can be found at Localities.
Meet the Mammals of the Morrison Formation (26 or 27 genera, 34 or 39 species)
NB: various other generic and species names have been in use at one time or another, and
may still be employed in some cases. Some of the names listed here may prove to be invalid;
for example, all the docodonts could be D. victor.
Docodonta (1 or 2 genera, 3 or 4 species)
Docodon victor; D. striatus;
D. superus; ?Peraiocynodon sp.
Placement uncertain: (1 genera, 1 species)
Fruitafossor windscheffelia;
Amphidon supperstes (a "symmetrodont", a worn
"amphilested"? It's definitely dead.)
Triconodonta (5 genera, 9 species)
Aploconodon comoensis;
Comodon gidleyi;
Priacodon ferox; P. fruitaensis;
P. grandaevus; P. lulli; P. robustus;
Triconodon sp.;
Trioracodon bisulcus
Multituberculata (5 genera, 7 species)
Ctenacodon laticeps; C. scindens;
C. serratus; Glirodon grandis;
Morrisonodon brentbaatar;
Psalodon potens;
Zofiabaatar pulcher
Dryolestoidea
Paurodontidae (8 genera, 9 species)
Araeodon intermissus;
Arcaheotrigon brevimaxillus; A. distagmus;
Comotherium richi; Euthlastus cordiformis;
Foxraptor atrox; Paurodon
valens; Pelicopsis dubius;
Tathiodon agillis
Dryolestidae (4 genera, 7 species)
Amblotherium gracilis;
Dryolestes obtusus; D. priscus; D. vorax;
Laolestes eminens; L. grandis;
Miccylotyrans minimus
'Symmetrodonta' (1 genus, 1 species)
Tinodon bellus
|
| Species: | Laolestes (Melanodon) godsoni |
| Place: | |
| Country: | |
| Age: | |
| Remarks: | Possibly a synonym of L. goodrichi. |
| Reference: | |
| Species: | Melanodon hodsoni Clemens WA & Lees PM, 1971 |
| Place: | Wealden, ?Sussex |
| Country: | England |
| Age: | Lower Cretaceous |
| Remarks: | "Work was started at University College on
the bone-bed when Dr W. A. Clemens joined the Zoology Department in 1960 as a post-doctoral
fellow of the National Science Foundation. As a result of this new work five further
mammalian teeth were obtained from the deposit. Four of these were of
multituberculates and one was the upper
molar of a eupantothere allied to Melanodon",
(Kermack et al 1965, p.536).
Savage, 1989 (p.5) places this species in Sussex. I'm assuming this refers to the same
fossil mentioned above, but it might not. |
| Reference: | Clemens & Lees (1971), A review of the English Cretaceous
Mammals, Journal of the Linnean Society (Zoology), 50, supplement 1, p.117-130. |
| Genus: Leonardus Bonaparte
JF, 1990
'for Leonardi'
Remarks: The genus is named for Giuseppe Leonardi, an Italian-Brazilian vertebrate
paleontologist. |
| Species: | Leonardus cuspidatus Bonaparte JF, 1990 |
| Place: | Los Alamitos Formation,
Patagonia |
| Country: | Argentina |
| Age: | Campanian Upper Cretaceous |
| Remarks: | The following is based upon my reading of
Bonaparte, 1990 (and many thanks are due to Rob B of New South Wales for supplying a
copy).
This genus is referred to Dryolestidae (p.74), a family best known form the Upper Jurassic
of North America and Europe. They seem to have branched out into the southern
supercontinent of Gondwana. An unexpected feature to my eyes is how well spaced the upper
molars are, as each keeps a considerable gap between itself
and the neighbours. A photo of a maxilla donated by
Dryolestes leiriensis (not viewable above. You'll have to
find your own photo!) gives a very different impression; crowded molars with no inhibitions
about close contact. In stereotypic metaphorical imagery, the molars of Leonardus
form a reserved English bus queue, while the earlier relative preferred a more Tokyo
rush-hour commuter train approach; no touching! as opposed to pack 'em in.
Two specimens were available. There was a piece of upper left jaw with four molars and a
further isolated upper molar. Bits of roots represent the probable final molar on the
maxilla, so there must've been at least five.
The teeth of the jaw
The final preserved crown has a reasonably deep ectoflexus
bay, but I've certainly encountered more impressive attempts; eg.
Groebertherium. The other teeth are less enthusiastic
about this feature. The foremost is a short, wide thing (1mm and 2.5 respectively).
Number two manages a bit more length, while the third is the widest (3.00mm). The final one
has the greatest proportional length (1.6mm : 2.5).
In all cases the dominant cusp is the stylocone. This is near the
labial border of the first and second crowns, but more centrally located for the rear
pair. It's positioned further forwards than the equivalent feature of Groebertherium
(p.75). Next largest is a sharp paracone. In contrast to Upper Jurassic dryolestids (but
not to G.) there's no metacone.
Holotype
MACN-RN 172 is a piece of upper jaw with the final four molars. It's employed by the Museo
Argentino de Ciencias Naturales, Buenos Aries, and the specific name is derived from the
sharp cusps on the labial side of the teeth. |
| Reference: | Bonaparte (1990), New Late Cretaceous mammals from the Los
Alamitos Formation, northern Patagonia. Natl. Geogr. Res. 6, p.63-93. |
| Genus: Miccylotyrans
Simpson GG, 1927 |
| Species: | Miccylotyrans minimus Simpson GG, 1927 |
| Place: | Morrison Formation, Wyoming |
| Country: | USA |
| Age: | Upper Jurassic |
| Remarks: | Upper dentition. |
| Reference: | Simpson (1927), Mesozoic Mammalia. VI: Genera of Morrison
panthotheres. Amer. J. Sci 5, p.409-416. |
| Genus: Parungulatum
Bonaparte JF, 1999 |
| Species: | Parungulatum rectangularis Bonaparte JF, 1999 |
| Place: | Los Alamitos Formation, Patagonia |
| Country: | Argentina |
| Age: | Upper Cretaceous |
| Remarks: | With thanks to Mikko Haaramo for the information. |
| Reference: | Bonaparte (1999), New Dryolestida (Theria) from the Late
Cretaceous Los Alamitos Formation (Argentina) and paleogeographical comments in Leanza,
H. A., (ed.) 1999: Abstracts of VII Int. Symposium on Mesozoic Terrestrial Ecosystems.
Buenos Aires, 1999, A1-A65. |
| Genus: Peraspalax Owen R, 1871 |
| Species: | Peraspalax talpoides Owen R, 1871 |
| Place: | Durlston Bay, Dorset |
| Country: | England |
| Age: | Lower Cretaceous |
| Remarks: | |
| Reference: | Owen, (1871), Monograph on the fossil Mammalia of the Mesozoic
formations. Palaeontological Society Monograph, 24, p.1-115. |
| Genus: Phascolestes Owen
R, 1871 |
| Species: | Phascolestes mustelula (Owen R), 1871 |
| Place: | Durlston Bay, Dorset |
| Country: | England |
| Age: | Lower Cretaceous (or perhaps Upper Jurassic) |
| Question: |
Does anyone know what Phasco means? I think it's 'bag' and Owen
considered many of these Dorset beasties to be marsupials. Phascolarctos cinereus
is the koala. According to McKenna & Bell, (1997), Phascolestes was proposed
"as subgenus of Peralestes." |
| Reference: | Owen, (1871), Monograph on the fossil Mammalia of the Mesozoic
formations. Palaeontological Society Monograph, 24, p.1-115. |
| Genus: Portopinheirdon
Martin T, 1999
'Porto Pinheiro tooth' |
| Species: | Portopinheirdon asymmetricus Martin T, 1999 |
| Place: | Porto Pinheiro |
| Country: | Portugal |
| Age: | Upper Jurassic (or Lower Cretaceous) |
| Remarks: | This is mentioned in Lillegraven, 2000. |
| Reference: | Martin (1999), Dryolestidae (Dryolestida, Mammalia) aus dem
Oberen Jura von Portugal. Abhandlungen der Senckenbergischen naturforschenden Gesellschaft
550, p.1-119. |
| Genus: Rougeritherium
Bonaparte JF, 1999
'Rougier's beast' |
| Species: | Rougiertherium tricuspes Bonaparte JF, 1999 |
| Place: | Los Alamitos Formation,
Patagonia |
| Country: | Argentina |
| Age: | Upper Cretaceous |
| Remarks: | With further thanks to Mikko Haaramo. |
| Reference: | Bonaparte (1999), New Dryolestida (Theria) from the Late
Cretaceous Los Alamitos Formation (Argentina) and paleogeographical comments in Leanza,
H. A., (ed.) 1999: Abstracts of VII Int. Symposium on Mesozoic Terrestrial Ecosystems.
Buenos Aires, 1999, A1-A65. |
| Other reports:
Cedar Mountain Formation, Utah
The Oklahoma Museum of Natural History collection includes indeterminate dryolestid teeth
from the Albian, Upper Cretaceous rocks of Emery County. |
back to top
| Help:
Should anybody have any further information, I'd be pleased to hear of it.
Regarding references and Bibliography:
I haven't and can't verify all the references, so beware. Traditional papers used in
constructing this page are in the bibliography. If you feel these are too few, then send
some more.
With thanks to all the featured sources.
Trevor Dykes, November 2001. Last update: 19.6.2011.
Ktdykes@arcor.de |
Bibliography:
Benton MJ (1990b), The Rise of the Mammals. Eagle Editions, (printed 1998), ISBN
1-902328-18-3.
Bonaparte JF (1990), New Late Cretaceous mammals from the Los Alamitos Formation,
northern Patagonia, National Geographic Research, 6(1), p.63-93.
Butler & Clemens (2001), Dental morphology of the Jurassic holotherian mammal
Amphitherium, with a discussion of the evolution of mammalian post-canine dental
formulae. Paleontology, 44 (1), p.1-20.
Carpenter K (1998), Redescription of the Multituberculate, Zofiabaatar and
the Paurodont, Foxraptor, from Pine Tree Ridge, Wyoming, Modern Geology 23,
p.393-405.
Clemens WA, Wilson GP & Molnar RE (2003), An enigmatic (Synapsid?) tooth
from the Early Cretaceous of New South Wales, Australia. Journal of Vertebrate
Paleontology, 23 (1), p.232-237.
Engelmann GF & Callison G (1998), Mammalian Faunas of the Morrison Formation,
Modern Geology, Vo 34 (4), p.343-379.
Ensom PC & Sigogneau-Russell D (1998), New dryolestoid mammals from the basal
Purbeck Limestone Group of southern England. Palaeontology, 41(1), p.35-55.
Hasiotis ST (1999), Continental ichnofossils from the Upper Jurassic Morrison
Formation, Western Interior, USA: what organism behaviour tells us about Jurassic
environments and climates. In (eds. Santucci VL & McClelland L) National Park Service
Paleontological Research, vol 4, p.121-125.
Heinrich W-D (1998), Late Jurassic Mammals from Tendaguru, Tanzania, East Africa.
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Kemp TS (2005), The Origin and Evolution of Mammals, Oxford University Press,
pp.331.
Kermack KA, Lees PM & Mussett F (1965), Aegialodon dawsoni, a new trituberculosectorial
tooth from the lower Wealden. Proceedings of the Roy. Soc., London, B, 162, p.535-554.
Krebs B (1998), Drescheratherium acutum gen. et sp. nov., ein neuer
Eupantotherier (Mammalia) aus dem Oberen Jura von Portugal, Berliner geowiss. Anhandlungen,
E28, S.91-111.
Krebs B (2000), The henkelotheriids from the Guimarota mine, p.121-128, in Martin
T & Krebs B (eds), Guimarota - A Jurassic Ecosystem, Verlag Dr Friedrich Pfeil,
München.
Lillegraven JA (2000), Dryolestidae (Dryolestoidea, Mammalia) aus dem oberen Jura
von Portugal. Journal of Vertebrate Paleontology, 20 (4), p.785 [a review of Martin,
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Luo Z-X, Kielan-Jaworowska Z & Cifelli RL (2002): In quest for a phylogeny of
Mesozoic mammals. Acta Palaeontologica Polonica 47 (1), p.1-78.
Martin T (2000), The dryolestids and the "peramurid" from the Guimarota
mine, p.109-120, in Martin T & Krebs B (eds), Guimarota - A Jurassic Ecosystem, Verlag
Dr Friedrich Pfeil, München.
McKenna MC & Bell SK, (1997), Classification of Mammals Above the Species Level.
Columbia University Press.
Molinero RV, (2003), Comparative anatomy of Henkelotherium guimarotae
(Holotheria), a Late Jurassic small mammal, and its relevance for the evolution of the
mode of locomotion of modern mammals, PhD Dissertation, Freie Universität, Berlin.
Probst E (1985), Deutschland in der Urzeit, C. Bertelsmann, ISBN 3-572-01057-8
Rougier GW, Chornogubsky L, Casadio S, Arango NP & Giallombardo A (2008), Mammals
from the Allen Formation, Late Cretaceous, Argentina, Cretaceous Research, prepublication
copy (16 pages), officially published in 2009.
Savage RJG (1989), British mammals of the Mesozoic Era, Biological Journal of the
Linnean Society, 38, p.3-7.
Simpson GG (1937), A new Jurassic mammal, American Museum Novitates, 943, p.1-6.
Wible JR, Novacek MJ & Rougier GW (2004), New data on the skull and dentition
in the Mongolian Late Cretaceous eutherian mammal Zalambdalestes, Bulletin of the
American Museum of Natural History, 281, p.1-144.
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Evolution, 6 (2), p.177-213. |
