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.
In brief and typically, dryolestoids were insect-baiting, mammalian pip-squeaks of
the northern Upper Jurassic. Remains are usually limited to teeth, with occasional bits of
lower jaw attached to them. The molars are characterised by
being short and wide, and they have a small talonid at the
backs of lowers, (Kemp 2005, p.166-167). Very occasionally, more substantial remains do
turn up, which provide a better picture of what the rest of the animals were like. They
were a significant mammalian off-shoot, rather than ancestral to ourselves.
Remarkably, having enjoyed their best days during the Upper Jurassic of Laurasia, (the then
mega-continent of the north), some eccentric dryolestoids pop up in the Upper Cretaceous of
South America, which was undergoing something of a 'Jurassic Park Revival’ at the time.
Various freaky representatives of predominantly earlier, northern lineages, (mammals and
dinosaurs), have been recovered from the Campanian-Maastrichtian rocks of Patagonia.
The first section of this directory contains critters more accurately referred to
somewhere within a taxon called Cladotheria sensu
McKenna, 1975, which contains dryolestoids and others. The second houses dryolestoids of
some kind or other, but as yet they defy a tidier arrangement.
This directory used to be larger and was split. Two families make up a grouping called
Dryolestida, and they now have their own enclosures:
Dryolestidae and
Paurodontidae.
The present organisation is partly endebted to (Warning, big, VERY BIG file):
http://epp.eps.nagoya-u.ac.jp/~seicoro/bio/mammalia.html |
| 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. Cladotherians B. Dryolestoids
| These genera are within Cladotheria sensu McKenna, 1975, which is a
wider taxon than Dryolestoidea. I’m a member myself.
Genus: Chunnelodon, Donodon,
other reports
Time-line:
Upper Cretaceous: Argentina
Lower Cretaceous: Chunnelodon, Donodon |
| Genus: Chunnelodon Ensom PC &
Sigogneau-Russell D, 1998
'Chunnel tooth'
Remarks: This is the first time I've encountered the use of British (& French?) slang
in zoological nomenclature. The Chunnel is the Channel Tunnel, which links England and
France. The name honours collaboration between the two countries; in this case, between
Mister E and Madam S-R. |
| Species: | Chunnelodon alopekodes Ensom PC & Sigogneau-
Russell D, 1998 |
| Place: | Purbeck Limestone Group, Dorset |
| Country: | England |
| Age: | Lower Cretaceous |
| Remarks: | The following is based upon my reading of Ensom
& Sigogneau-Russell, 1998.
Information on this mammal is presently provided by two lower
molars which very possibly came from the same mouth (p.41). Both have similar lengths
of 0.72mm, although the widths vary a bit; 0.36 for the type fossil and 0.41 for its
friend. In either case the crowns are narrow; not much wider than the front root.
The protoconid is a 'moderately high' cusp and the
paraconid is unimpressively sized, but not 'shelf-like' as
for Dorsetodon from the same location. The
metaconid is fairly tall, but lower than the protoconid.
At the rear of the crown, the talonid has been reduced to
a single cusp positioned on the lingual side. This is both
high and sharp. The rear root of the tooth is somewhat stronger than the front one, and
they're nearly in straight alignment on their labial sides.
The sharpness and alignment of the paraconid, metaconid and talonid cusp (known to its
friends as a hypoconulid) on the lingual aspect of the crown are unusual features.
Affinities
The crown of the molar isn't built like a dryolestid,
and the 'non-shelf-like protoconid isn't compatible with
paurodontids (p.52). That means Chunnelodon must belong somewhere else.
However, it does qualify as a cladotherian and may be a
relative of dryolestoids (including dryolestids and paurodontids). The same could apply
for Donodon from the Lower Cretaceous of Morocco.
Holotype
DORCM GS 378 is a left lower molar in the collection of the Dorset County Museum,
Dorchester. The specific name is Greek for 'sly as a fox', and this refers to the layer of
clay from which the fossil was obtained. It's called the Sly by local quarry workers, and
they're obviously well qualified to know. |
| Reference: | Ensom & Sigogneau-Russell (1998), New dryolestoid mammals
from the basal Purbeck Limestone Group of southern England. Palaeontology, 41(1), p.35-55.
|
| Genus: Donodon
Sigogneau-Russell D, 1991
Family: Donodontidae Sigogneau-Russell D, 1991 |
| Species: | Donodon perscriptoris Sigogneau-Russell D, 1991 |
| Place: | Anoual |
| Country: | Morocco |
| Age: | Berriasian?, Lower Cretaceous |
| Remarks: |
Ensom & Sigogneau-Russell express doubts about this genus belonging to Dryolestoidea
(p.52). As with Chunnelodon it seems to be
some form of cladotherian.
The holotype is an isolated upper molar, which was thought to
belong within the Sublegion of Dryolestoidea, if not Dryolestida. However, further
material, a referred dentary fragment with two molars,
doesn't belongs neither to that group or this genus. "I think that the dentary
specimen referred to D. perscriptoris should be attributed to
"Symmetrodonta" The reduction of the
lingual cingulid and mesial cingulid cuspule "f"
are similarities shared with Gobitheriodon", (Averianov 2002, p.713). |
| Reference: | Nouveaux Mammifères thériens du Crétacé inférieur du Maroc.
Comptes Rendus de lÀcadémie des Sciences, Série II 313, p.279-285. |
Seven Phases of Teeth
(Postcanines)
IV Cladotheria
The following is derived from and inspired by my reading of Butler & Clements, 2001,
(p.13-14).
For the purposes of their discussion, the authors divide Cladotheria into Dryolestida,
Amphitheriida and Zatheria, (p.13). The
basal postcanine
formulae for cladotherians aren't clear. With regards to outgroups, five
premolariforms are common amongst
morganucodontids, and a maximum of five are known
from paulchoffatiids, (basal multituberculates).
Kuehneotherium might have mustered up to
six, whilst other "symmetrodonts" made do
with four or less. One of the more basal cladotherians is
Amphitherium and it has five premolars; a condition known from at least one
primitive zatherian. However, basal cladotherians
(including drolestidans) had four
premolars.
The original cladotherian molar count is also uncertain. In
outgroups: morganucodontids 3-5; multis 2; docodonts 5-8;
Kuehneotherium 4-5. Within Cladotheria
dryolestids get up to nine, paurodontids can
have seven, which also seems to be the case for one specimen of Amphitherium.
Variation in the number of molars seems partly endemic to lineages with many teeth,
(docodontids and dryolestidans).
The evolution of cladotherian molars seems to have produced an increase in cusps and
cutting edges, (p.14). This was achieved by an increase in numbers, greater complexity in
the structures of the crown, or by a combination of both. However, the force advantageous
position of proximity to the jaw joint, (where power is at its greatest concentration),
acted as a constraint. It's no good having sophisticated grinders in a position which
provides insufficient power for their effective usage. If nine molars are good, ten aren't
necessarily better.
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. |
| Other reports:
Candeleros Formation, Rio Negro Province, Argentina
Remains have come to light at this new location, which is referred to the lower Cenomanian
of the Upper Cretaceous. So far reported are a fragmentary skull with partial
mandible, an incomplete lower jaw, (possibly from the same
taxon), a very fragmentary, broadly similar but larger jaw,
and a double rooted tooth, which probably belonged to an even bigger animal.
According to the abstract, various features "suggest affinities with dryolestoids,
among cladotherians." Unlike dryolestids, there's an unspectacular number of
molars, (m1-m3).
Reference: Apesteguia S, Rougier GW, Forasiepi AM, Novas FE & Nocacek M (2002), Los
Mamiferos de 'La Buitrera', Formacion Candeleros (Cenomaniano Temprano, Cretacico Tardio),
Provincia de Rio Negros, Argentina. 8th Congreso Argentino de Paleontologia y
Bioestratigrafia, Corrientes, Argentina.
With thanks to the Polyglot Paleontologist, where an English translation of the abstract is
freely available. |
A. Cladotherians B. Dryolestoids
| Taxon: Dryolestoidea Butler, 1939
Butler established Dryolestoidea as a suborder for Paurodontidae,
Dryolestidae and Amphitheriidae. However,
Amphitherium and relatives subsequently
resigned on the grounds of being too derived.
The dryolestoids in this section are neither dryolestids nor paurodontids. Most are rather
weird Upper Cretaceous critters from South America. Others are possibly dryolestoids
which are presently hard to pin down more precisely.
Some form from the fermentation, Mesungulatidae
Rougier et al, 2009 busied themselves with some SAm dryolestoids and provided some
restructuring starting on page 12. They refer a number of genera to the already
established family of Mesngulatidae, and cite a number of significant derivations
uniting them; eg. well developed cingula on upper and lower molars, roots that are
compressed from the front to the rear, and multi-rotted final premolars.
Peligrotherium and Reigitherium
differ from Mesungulatum by having higher crowns,
accessory cuspules set lingually on lower molars and
bucally on uppers. Nevertheless, they all appear to belong
to a monophyletic dryolestoid radiation, and Mesungulatidae is available as a category
to house them. Rather than persisting with several families based upon only single
genera, these researchers grant all three the honour of being mesungulatids.
So seen, the fossil record allows the recognition of what may be a tendency for an
increase in size range for these mesuns. The earliest versions are small to smaller.
Paleocene Peligrotherium is a different proposition; a decently dog-sized
dryolestoid. Between comes Los Colonia Formation's Mesungulatum. That locality
is thought to be a bit more recent than the other Upper Cretaceous sites in Patagonia, and
its resident dryolestoid is around 30% larger than the earlier models. There's certainly
an increased in body-size ranges evident for North American
eutherians during the aftermath of the Cretaceous. A similar attitude for SAm
dryolestoids wouldn't be all that surprising to me. However, the relevant SAm fossil
record is much more restricted than the contemporary NAm one.
Another point briefly mentioned is diet. It's very brief: "...an important group of
omnivores-herbivores..." That isn't elaborated upon, but it contrasts with the
insect interests of more "traditional" dryolestoids (especially dryolestids) from
earlier times in Laurasia.
Genera: Atlasodon,
Barberenia, Bondesius,
Brandonia, Casamiquelia,
Coloniatherium, Groeberitherium,
Mesungulatum, Peligrotherium,
Quirogatherium, Reigitherium
(alternatively seen as a docodont),
Thereuodon, other reports
Time-line:
Paleocene: Peligrotherium
Upper Cretaceous: Barberenia, Bondesius, Brandonia,
Casamiquelia, Coloniatherium, Groeberitherium, Mesungulatum,
Quirogatherium, Reigitherium, Patagonia
Lower Cretaceous: Atlasodon, Thereuodon, Australia?
Middle Jurassic: England |
| Genus: Atlasodon
Sigogneau-Russell D, 1991
'Atlas tooth' |
| Species: | Atlasodon monbaroni Sigogneau-Russell D,
1991 |
| Place: | Anoual |
| Country: | Morocco |
| Age: | Berriasian?, Lower Cretaceous |
| Remarks: | An isolated tooth species similar to
Thereuodon. Originally described as 'symmetrodont',
they may be the milk dentition of a dryolestid or
stem-group zatherian, (Averianov 2002, p.172). |
| Reference: | Sigogneau-Russell (1991), Nouveaux Mammifères thériens du
Crétacé inférieur du Maroc. Comptes Rendus de l'Académie des Sciences, Série II, 313,
p.279-285. |
| Genus: Barberenia
Bonaparte JF, 1990
'for Barberena'
Family: Barbereniidae Bonaparte JF, 1990
Remarks: Similarities to Thereuodon suggest dryolestid or
stem-group zatherian milk teeth (Averianov 2002, p.712),
although 'symmetrodont' affinities were originally
proposed.
This section's turning into a dental nursery.
The generic name honours the work of Mario Costa Barberena, a Brazilian paleontologist
cocerned with Permian and Triassic vertebrates. |
| Species: | Barberenia araujoae 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 is a further critter described as a 'symmetrodont'
but subsequently transferred. There are four more in the same paper. Anyway, the upper
molars are considerably longer than wide (p.71). If cusps
bring wealth, then it was more richly endowed than most Los Alamitos (not actually)
'symmetrodonts'. The paracone is both bigger and taller than the somewhat rounded stylocone,
with both being positioned closely together. A metacone is sometimes in attendance, as is
a generally well-developed parastylar cusp. The ectoflexus
forms a bay of modest ambition, meaning it's rather shallow. Two metastylar cusps
often keep the stylocone company.
While perhaps descriptively qualifying as obtuse-angled 'symmetrodont' molars, they have
strong contrasts to the classic form. For starters, these teeth are elongated. They also
differ starkly with abtuse-angled models (eg. Tinodon).
Nevertheless, there are several similarities which might have been significant; the position
of the stylocone isn't too different; an enlarged parastylar area in league with a reduced
cingulum; and two basins provided by a crest linking the
paracone and stylocone. These could indicate affinities with other local critters (viable)
and maybe (not viable) Symmetrodontoides.
(Should this have been the case, the animal would've been an obtuse-angled descendant of an
acute-angled ancestor.) In any case, the distinguishments were strong enough to justify a
new family; Barbereniidae (p.73).
Lowers?
A fragment of lower jaw may also belong to this species, and came from the same place and
stratum. This find preserved a molar, which is certainly one of the ultimate three in the
series, and possibly the penultimate tooth. It's long and narrow, and the width:length
ratio is close to that of the uppers. The trigonid is
long with the paraconid being the tallest cusp. It's
positioned in the front half of the crown. Of the other two main cusps, the
protoconid is taller than the
metaconid. A small talonid
is nigh on centrally placed at the back of the tooth, and devoid of clear cusps.
It seems a suitable counterpart for the upper molars, and there are similarities apparent
with the crests. In the absence of clearly associated uppers and lowers, secure matchmaking
can be impossible.
Holotype
The type fossil, MACN-RN 166, is an upper left molar in the custody of the Museo Argentino
de Ciencias Naturales, Buenos Aries. It's serving its indefinite sentence accompanied by a
further trio of uppers. A fragment of lower jaw may belong to the same gang.
The specific name honours Dina Araujo, a Brazilian paleontologist with interests in
vertebrates of the Permian and Triassic. |
| Reference: | Bonaparte JF (1990), New Late Cretaceous mammals from the Los
Alamitos Formation, northern Patagonia. National Geographic Research 6, p.63-93. |
| Species: | Barberenia allenensis Rougier et al, 2009 |
| Place: | Allen Formation,
Patagonia |
| Country: | Argentina |
| Age: | Upper Cretaceous |
| Remarks: | The following is based upon my reading of
Rougier et al, 2008, a prepublication of a study which was published in early 2009. Oh
yeah, my copy also has different page numbers to the published version. Thanks go to
Javier.
The species was established for a molar-like tooth which, strictly speaking, probably
isn't a molar as such (p.8). Milk
premolars can be teeth temporarily performing molar
duties but, as they then get replaced (typically by less complex premolars at the same
position), they can't be defined as molars. No, the rules dictate that molars must be
teeth of the first generation without replacements. (Gerda's sister butts in at this
point. She apparently did replace several teeth her dentist understood to be molars with
second generation monstrosities of a simplistic construction. I've not asked for a closer
look and don't happen to know the appropriate terminology beyond 'weird'.)
Enough of Gerda's sister
This is also a new species for a genus which hopefully, at some stage, will get
demolished. As the fossil is probably a deciduous
tooth from a kid, documentation would be useful concerning the identity of the parents.
They were presumably members of some local dryolestoid species or other. However, as
things presently stand, it's not possible to ascertain which one. This problem results
in the erection of an artificial taxon to hold the baby. If taken overly literally, the
adults and juveniles are members of different genera. While that's nonsensical, a more
realistic solution isn't as yet available. Besides, my kids clearly do differ significantly
from me at times by far more than merely generic distinctions. At least, that's the
impression I've formed.
Be that as it may, this genus falls into the middling sized South American dryolestoid
category (p.9). In this instance, that results in a maximum length of 2.31mm and a
maximum width of 1.90. The cusps are more delicately built than is the case for
Quirogatherium, and it's also smaller. These
sharp and tall cusps are much like those of Barberenia araujoae. However, the
tooth is larger, it's less of an elongated triangle in outline, has a proportionately
smaller parastylar area, and the front cingulum isn't as
strongly developed.
The molar is triangular in outline and possessed two roots, with the front one being
larger. Winner of the cusp height contest is the paracone on the
buccal side, which experienced little wear. Second is the conical stylocone.
Rather than possessing a metacone, the owner opted for a minimalist bulge in the
metacone position.
Kid's stuff, or perhaps not?
Dryolestoid deciduous premolars are available form Upper Jurassic Laurasia, and this
fossil happens to be similar to them. That's way various researchers have stated the
possibility of SAm specimens (such as Barberenia) also being such teeth. However,
that isn't the only viable explanation (p.10). Of all known SAm dryolestoids, only
Peligrotherium of the Paleocene has so far provided
reasonably complete dentitions, and the position identified as P2 is also similar to
Barberenia. (The relatively high number of specimens from La Colonia is also more
suggestive of P2s rather than milk premolars.) This at least invites the possibility of
other such specimens being P2s rather than DP2s, and that leaves the issue as unsolved.
Holotype, free competition!
MML-Pv 13 is an upper molariform (probably not a
molar) in the collection of the Museum Minicipal de Lamarque. I've decided to launch an
exciting promotional competition concerning the meaning of the specific name of this
fossil from the Allen Formation. I refuse to reveal the meaning of allenensis!
The first reader to send in a correct explanation (or an interesting wrong one) could
win their name a place in virtual immortality with a mention on this page. Also on offer
is a thoroughly genuine photo of a Jurassic dryolestoid hunting a
Diplodocus. |
| Reference: | Rougier GW, Chornogubsky L, Casadio S, Arango NP &
Giallombardo A (2009), Mammals from the Allen Formation, Late Cretaceous, Argentina,
Cretaceous Research, 30(1), p.223-238. |
| Genus: Bondesius Bonaparte
JF, 1990
'for Bondesio'
Remarks: The generic name honours Pedro Bondesio, a researcher of mammals from the Cenozoic.
Bonaparte referred the genus to Symmetrodonta. A
more recent view sees it as being a dryolestidan milk tooth, and that's what I'm presently
following.
"Its slender roots, enlarged talonid, and anteriorly
projecting paraconid suggest that it is rather deciduous
than permanent tooth... Consequently, Bondesius is removed here from the
"Symmetrodonta" and placed within the Dryolestida. Currently, there is no
unambiguous record of "symmetrodonts" in the Late Cretaceous of South
America", (Averianov 2002, p.712).
I've also seen it suggested as the tooth of a bat or proto-bat, but I've no idea how
serious that view was. |
| Species: | Bondesius ferox 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).
The type fossil of mighty Bondesius is a lower molar
with an impressive length of a quarter of a centimetre (p.66). (It's impressive compared
to many.) The main three cusps display acute triangulation, and it's twice the size of
Tinodon lepidus. The
metaconid is larger than the paraconid, and set
somewhat closer to the protoconid. The triangulation
is asymmetrical. The lingual face of the protoconid is more
concave then is the case for Kuehneotherium
and T. lepidus. Excepting for a talonid at the back,
there's no shelving around the base of the crown (ie. no
cingula). The talonid sports a cusp termed the hypoconulid.
The centrally located protoconid is much the largest of the main cusps, with the paraconid
being the smallest. That one is also set low down at the front of the crown. This tooth
was held in place by a pair of roots, with the front one being considerably larger than
its colleague. Overall, it's reminiscent of Kuehneotherium and Tinodon,
although the lack of a cingulum is a distinction and characteristics of the protoconid and
paraconid also differ.
Upstairs?
An upper molar was also referred to the genus. This is a narrow crown with four cusps
aligned in a line (p.67), but the identity is subject to some doubt. It seemed to fit
expectations for 'acute-angled symmetrodonts', yet displays a couple of specialisations
on the general theme. Among these is the crest connecting the two front cusps, the strength
of the internal cingulum and the straight alignment of the cusps. I'll allow myself a
quick pat on the head as, when reading that, triconodonts
came readily to mind. However, Bonaparte observes: "... the
ectoflexus, the crista and the basined occlusal surface argue against this
relationship."
I've added a question mark to the heading of that paragraph. The referral was more
confident.
Holotype
The holotype, MACN-RN 161, is a right lower molar in the collection of the Museo Argentino
de Ciencias Naturales, Buenos Aries. The specific name isn't for the faint-hearted as it
means 'ferocious'. The tooth suggests a brutal killer and is relatively large, when
compared to 'symmetrodonts'. In that company, a
length of 2.5 millimetres qualifies as large. |
| Reference: | Bonaparte JF (1990), New Late Cretaceous mammals from the Los
Alamitos Formation, northern Patagonia. National Geographic Research 6, p.63-93. |
| Genus: Brandonia Bonaparte
JF, 1990
'for Brandoni'
Family: Brandoniidae Bonaparte JF, 1992
Remarks: The genus is named in honour of Zulma Brandoni de Gasparini for his work work on
Mesozoic Patagonian reptiles. Although I've seen 1992 cited as the year of authorship,
that's wrong. It's definitely 1990. I'm presently holding page 69 up to the monitor so
you can see for yourself. At that time, it was tentatively referred to the family of
?Spalacotheriidae. A new family was established two years later, and dryolestoid
affinities are now accepted.
A newer view
Rougier et al, 2008 includes a lower molar from the Allen Formation of Patagonia which
they termed cf Brandonia (p.7). That indicates that comparisons with this genus are
well worth making, although it may not be a member itself. Thanks are due to the supplier
of the paper, which was actually published in 2009.
It's a complete molar crown showing little wear and has thin roots. The layout is fairly
typical for dryolestoids excepting for the broadness of the
trigonid (p.8). The protoconid dominates the landscape. Its
buccal wall is convex whereas the lingual one is
flatter. Second in height is the metaconid situated on the most lingual area of the
metacristid crest. A cingulum at the front of the
crown carries two further cusps, and these appear to be homologous with the e and f of
other member of Cladotheria. They may have been
involved in an interlocking mechanism with the back of the neighbouring tooth. A rear
cingulum bears a single cusp, and it's in the right sort of position to equate with the
hypoconulid of more derived mammals. This is the structure
suspected of interlocking with the e and f of the following molar.
Size and affiliations
Maximum length 1-49mm, max. width 1.16mm.
The overall structure seems suitable for molars of Brandonia, although the tooth is
somewhat smaller than referred lower molars from other localities and shows some differences.
A close relationship is likely. However, upper molar details happen to have played a
lively role in considerations on this genus, and none are yet available from the Allen
Formation. The authors opted not to establish a new taxon
at this juncture.
|
| Species: | Brandonia intermedia 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).
Bonaparte tentatively referred this genus to ?
Spalacotheriidae (p.69). However, as with the other four 'symmetrodonts' in the paper, it
subsequently objected and demanded sanctuary with its dryolestoid relatives.
The labial margin of the upper
molar features an impressive stylocone, and this connects with the taller
paracone by means of a crest, which he termed the mesocrista. ('Meso' indicates the
position, as it runs across the middle of the crown.) The
ectoflexus has a form reminiscent of
Symmetrodontoides canadensis, and the same applies for the placement of the stylocone.
A parastylar hook is confluent with a reduced cingulum.
As with Casamiquelia there are two basins, but the
foremost 'coalesces with the parastylar-cingular area'.
The crown's a bit longer than wide, which a refreshingly accessible detail. Another point
that's none too obscure is the number of well formed cusps. There are only two; a paracone
and a stylocone. The former is larger, and the latter near the
buccal margin of the crown, which is graced by an
ectoflexus. That bay ensures an asymmetrical heart-like kind of outline when viewed
from the occlusal perspective.
The paracone is accorded a similar position to its counterparts from (according to the
text!) Peralestes, Spalacotherium
and other acute-angled 'symmetrodonts'. (My
exclamation mark is prompted by my understanding, that the first 'genus' is probably the
upper jaw of the second. If not, then only the lower molars are known from Spalacotherium,
so this comparison puzzles me.) In contrast to such critters though, Brandonia's
stylocone is fairly central on the labial margin, and several other cusps are 'missing'.
The presence of the aforementioned well-defined basis is a further contrast (p.70).
Similar features are known from some dryolestids including Melanodon (which I treat
as a synonym of Laolestes) and
Groebertherium.
Affinities
Although referred to ?Spalacotheriidae, Bonaparte felt the distinctions made membership of
the family improbable. This is enhanced by the recognition of it as a dryolestoid, and the
author did indeed state that structural similarities could point nearer to the dryolestids.
It was a matter left open for further studies and fuller collections.
Holotype
MACN-RN 164 is an upper molar in the collection of the Museo Argentino de Ciencias
Naturales, Buenos Aries. The specific name refers to the province of Rio Negro. A
couple of other molars keep it company. The specific name refers to similarities with
some dryolestid molars. Those turned out to have more
significance than originally realised. |
| Reference: | Bonaparte JF (1990), New Late Cretaceous mammals from the Los
Alamitos Formation, northern Patagonia. National Geographic Research 6, p.63-93. |
| Genus: Casamiquelia
Bonaparte JF, 1990
'For Casamiqula'
Family: Casamiqueliidae Bonaparte, 1999
Remarks: More recent research suggests this taxon probably
belongs within Dryolestida, (Bonaparte, 1999).
The generic name honours Rodolfo M Casamiquela, a paleontologist and geologist active in
Patagonia. |
| Species: | Casamiquelia rionegrina 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 was originally described as a small 'acute-angled
symmetrodont' based on two upper molars, but that interpretation now seems
inappropriate. These teeth are longer than wide, and a strong
ectoflexus produces something like a heart-shaped crown from the
occlusal perspective (p.68), with the resultant rear lobe
larger than the front one. Both are basined. The stylocone, positioned somewhat
buccally from the centre of the crown, is larger than the
paracone on the lingual margin. Both are connected by a
short crest, provisionally termed the mesocrista, and this divides two basined areas.
The proportions (which presumably refers to length:width) are similar to the Purbeckian
'symmetrodonts' 'Peralestes' and
Spalacotherium, but the cusp arrangement differs. (I'm presently following the
view that those two genera are co-generic, with the latter being the lower jaw. As
paracones are only present on upper teeth, I don't pretend to understand how
Spalacotherium can be directly comparable. Nevertheless, that's what it says on
page 68.) The size of the ectoflexus bay outdoes that
of any known 'symmetrodont'. The lack of either a parastylar hook or metastylar cusps
would also have been unusually, had Casamiquelia been a 'symmetrodont'. Those critters
have such things (p.69). Those aforementioned basins are reminiscent of some
dryolestids such as
Groebertherium stipanicici.
Holotype
MACN-RN 163 is a near complete upper molar in the collection of the Museo Argentino
de Ciencias Naturales, Buenos Aries. The specific name refers to the province of Rio
Negro. |
| Reference: | Bonaparte JF (1990), New Late Cretaceous mammals from the Los
Alamitos Formation, northern Patagonia. National Geographic Research 6, p.63-93. |
| The Upper Cretaceous in Argentinian
Patagonia
The following is based somewhat loosely upon Pascual et al, 2000.
To most of us Patagonia could serve as an illustration of the meaning of remote. It's the
thinly populated region of southernmost South America. It also holds surprises.
Argentinian Patagonia has a small minority of native Welsh speakers and the most southerly
town in the world; Ushuaia. Patagonia also boasts an impressive array of Mesozoic and
post-Mesozoic fossil sites.
Among them are two mammal yielding localities of Upper Cretaceous origins. These are in
northern Patagonia. Find Rawson on a map and head inland to get the general area. This
study centres on remains recovered from La Colonia Formation in Chubut Province, (p.396).
Many more taxa have been found in Los Alamitos Formation,
Rio Negro Province, which is further north. The age is Campanian-Maastrichtian and this
correlates to the Alamitan South American Land Mammal Age (SALMA).
Newcomers form the north
While it might surprise many to hear of Welsh being spoken in Argentina, some of the
Cretaceous fossils have proved unexpected too. Welsh is a Celtic language with its roots
stretching back into the mists of pre-Roman times, when Celtic languages were widespread
across western and central Europe. You could say Welsh is a highly
derived relic of an ancient lineage, which arrived with
immigrants from the distant north. My first name, Trevor, is Welsh and linguistically, it
shares common origins with the names of such cities as Trier in Germany and Trelew in
Chubat Province, Patagonia.
Pascual et al offered an original perspective on a genus called
Reigitherium. They interpreted it as a
docodont. That group is best known from the Upper
Jurassic of the northern hemisphere. However, others see it as a
dryolestoidean, which would also make it a late relic
from a Jurassic lineage of the north. Based upon the presence of various dryolestoideans
in the area, that seems more likely. In either case, it's a very aberrant representative.
And this kind of theme crops up fairly regularly with Cretaceous Patagonian vertebrates.
La Colonia Formation
The lowest part of La Colonia is non-marine in origins, and up to 16 metres thick, (p.399).
On top of this comes rock with many fragmentary fossils of freshwater fish and plant
remains. This was probably the results of deposition in an estuary, on tidal flats or a
coastal plain. It shows both freshwater and tidal influences. The climate alternated
between humid and arid. This is the thickest section of the formation, (p.400), and the
source of most remains.
When humid conditions prevailed bioturbation was intense, (that's disturbance of the ground
caused by animals tunnelling or digging, and also plant roots growing). Remains of aquatic
and terrestrial residents are common: fish, turtles, crocodiles, plesiosaurs; lizards,
snakes, dinosaurs and some mammals. Notable among the dinos is a horned meat-eater called
Carnotaurus sastrei. And, as might be expected in Cretaceous Patagonia, it's a
peculiar representative. A quick check with Mike Keesey's Dinosauricon page shows
Carnotaurus had horns
above the eyes and incredibly short arms. (He has it down as a neoceratosaurian for fans of
such details). When the climate was arid there were salty mudflats hosting far less life.
The only signs of largish animals found are dental plates from fish.
The upper part of the formation is a fairly uniform sequence of claystones. This yields
fragments and occasional complete bivalve shells.
As yet, no absolute dating has been carried out and the ages represented by the formation
have been subject to differing interpretations. The presence of various index fossils
support Campanian-Maastrichtian, though the lowest strata are probably earlier and the
uppermost may well be Paleocene.
Ancient islands
During the Upper Cretaceous and Paleocene, southern South America was subject to oceanic
encroachment from the Atlantic, (p.401). The region was turned into an archipelago of
islands. At times the northeast and southwest of the continent were isolated from each
other. However, faunal interchanges were sometimes possible. Hasdrosaurid dinosaurs migrated
in from the north and reached the extreme south. Mammals with
tribosphenic teeth may have arrived at about the same
time, although unambiguous fossils are lacking. (At least one site in Peru with
marsupials may be Upper Cretaceous -Laguna Umayo.)
What is remarkable is the persistence of at least one major lineage of originally northern
non-tribosphenic mammals, the dryolestoideans. A possible (subject to interpretations)
pretribosphenic group was present in the Patagonian Paleocene, as shown by
Monotrematum. As that's the only
monotreme material so far found outside of Australasia,
that group seems to have originated in the southern hemisphere. (Other opinions suggest
monotremes are descendants of tribosphenic mammals, but endemic southern ones called
australosphenids.) Presumably,
Monotrematum's ancestors arrived via Antarctica, and perhaps swapped maps with
marsupials on their way to Australia.
Dryolestoids in South America
Every year, members of the Society of Vertebrate Paleontology meet up for a party...,
scientific discussions on vertebrate paleontology. The 2004 meeting is due in November. In
advance, abstracts of presentations are released. They are available on-line in a large
file. It runs to over 300 pages. Among them (about on page 30) can be found: Rougier G &
and Apesteguia S, The Mesozoic radiation of dryolestoids in South America: dental and cranial
evidence. That's my source for the following information.
The fossil record of South American Mesozoic mammals is relatively poor, but getting better.
Relevant fossil pre-dating the Upper Cretaceous are restricted to
triconodonts,
australosphenidans and Vincelestes. In
contrast, no tribosphenic mammals are presently known
from the Upper Cretaceous, (although others might disagree with regard to one or two
reports), and the scene was dominated by eccentric dryolestoids. Despite apparently being
at least almost extinct in the northern hemisphere, they were thriving in South America.
Unlike earlier relatives, these animals don't show an excessive enthusiasm for lots of
molars. A conservative four seems to have been in fashion.
The earliest record is from the Candeleros Formation, which is Cenomanian-Turonian. Parts
of skull and jaw have been found for two closely related species. The molars are
single-rooted. The Campanian of Patagonia provides both the Los Alamitos and Cerro Tortuga
Formations. These housed members of various families: probable dryolestids,
quirogatherids, casamiquelids, mesungulatids and reigitheriids. A diversity of sizes are
known with molars ranging between lengths of 1mm to almost a centimetre. The latter is
unusually large for the time. The probable tastes centred on insects and some predominant
munchers of plants. Other mammals were both less plentiful and less diverse. These include
multituberculates,
gondwanatherians and possible triconodonts, (or
animals with similar teeth). A few dryolestid teeth are also known from Upper Cretaceous
sites in Bolivia, but their age isn't indicated.
Several localities of the Patagonian La Colonia Formation have donated Maastrichtian fossils,
but the diversity is less impressive. Only reigitheriids and mesungulatids have so far
turned up, with the latter being known from middling to larger sizes. Their only known
companions are multis. The latest dryolestoid comes from the Paleocene. This was a
relatively large descendant of K-T survivors named Peligrotherium. It hails from the
Salamanca Formation, and may be a derived relative of
Reigitherium. (I presently have that genus listed as a weird
docodont. This is because that's how it was described in
the most recent paper I've got. If a newer publication becomes available, then I'll
probably rewrite the entry and move it.)
Los Alamitos mammal fauna
The following has been set off by my reading of Bonaparte, 1990. There's bound to be some
overlap with the above text. Bonaparte's study concerned remains from Los Alamitos
Formation.
The mammals of Los Alamitos are an interesting mix, and this remains applicable despite
subsequent revisions. At the time of Bonaparte's publication, 1990, 14 species were
recognised (p.79). One, Vucetichia, has since been amalgamated with
Ferugliotherium, which has itself
been transferred from Multituberculata to
Gondwanatheria. But, as a second species of
Austrotricondon appeared, the number of species hasn't declined. There's at least one
more present. Some fossils were tentatively referred to Ferugliotherium on the condition
that it was a multi. Those remains are multi, and can't be part of the genus. Unfortunately,
they aren't in very good condition, and can't be used as the basis of a formally described
taxon. Better material may turn up one day.
Deep South versus North America
This isn't intended as comment on the current political situation, as the subject is Upper
Cretaceous mammals. Los Alamitos is presently the only Gondwanan fauna of this age with a
good level of diversity and, especially as South America was an archipelago of islands, it
wouldn't be reasonable to assume it's somehow typical. Islands are notorious for housing
taxonomic eccentrics. Although there are a considerable number of faunas in North America
boasting of this level of variety (and higher levels), they shouldn't be taken as being
typical of Laurasia either. The composition of mammals differs in what's known of Asia and
Europe.
Bearing that in mind, the critters of Los Alamitos bear little resemblance to any northern
faunas of the time. Whereas multis often supply 30 or 40% of species in the north, only
one has been found here, and its fossils are rarities.
Diversity
Although various taxa were assigned to Triconodonta
and Symmetrodonta, there's much scope for doubt about
those conclusions. The 'triconodont' molar pattern of three
main cusps in a central line is basal for
mammals, and thus not necessarily informative about
relationships. It's also now thought that 'Symmetrodonta', as previously used, is a rough
grade rather than a grouping with genuine affinities. Besides which, all Bonaparte's
'symmetrodonts' are very possibly dryolestoids.
Los Alamitos was home to at least two gondwanatherians, and nothing comparable has been
found in Laurasia. A bit more is now known, but they're still a mysterious lineage of
herbivores with a fossil record beginning here, and extending through time to the Eocene of
Antarctica. Upper Cretaceous traces have turned up in Madagascar, India and perhaps
Tanzania, although the latter identification is no stronger than tentative. That's enough to
demonstrate a broad geographic range. There have also been advances in knowing what they
aren't. There's little to support relationships with either multis or the
placental xenarthrans; armadillos and relatives. As for
what they were, some kind of specialised mammal is the present verdict.
Absentees
Los Alamitos has a severe shortage of multis, but a couple of other significant northern
lineages are completely missing. At this time, North America had fallen for the charms of
metatherians (and arguably some full-blown
marsupials). Asia was enjoying the attentions of
eutherians (and arguably some full-blown placentals).
Patagonia provided a home for neither. A secure presence for either group isn't yet known
from Cretaceous South America, although there are a couple of possible intruders further
north. (Problems with identification of poor material and clarity regarding the ages of
locations contribute uncertainty.) These magnificent 'northern cutters'
(boreosphenidans) may have been all the rage in
Laurasia, but Patagonia marched to the beat of a different drummer.
Welcome to Patagonia - where the Jurassic rocked on
A horde of mini-pillagers, dryolestoids, were thought to have enjoyed their greatest glory
during the Upper Jurassic and into the lowermost Cretaceous, when they stalked the hunting
grounds of North America and Europe. They didn't appear to have reached elsewhere.
At least, that's how things looked prior to Los Alamitos. In this part of the Campanian
world, plenty of dryolestoid sperm was fertilizing dryolestoid eggs. Audacious dryolestoids
were producing babies in fabulously derived shapes and
(according to presently unpublished finds) impressive sizes. This fauna contains the most
diverse gang of dryolestoid mammals ever found. There were those with traditional tastes,
who insisted on tearing up invertebrates. But there were also larger representatives with
(presumably) larger victims in mind. And, with Mesungulatum,
there were dryolestoids equipped for gardening duties. No northern versions are known to
have developed such an interest.
In terms of individuals, species and lifestyles, Los Alamitos is the pinnacle of dryolestoid
success.
Northern high-tech toothers
What follows involves some dollops of my own idle speculation.
The earliest metatherian and eutherian critters presently known are both about 125 million
years old, and come from the upper Yixian fauna of China.
This upper assemblage presently includes five distinctive mammalian lineages. As well as
Sinodelphys and
Eomaia there was also a multituberculate, a eutriconodont and a selection of
spalacotheroid 'symmetrodonts'. Ancient
docodonts are also known from elsewhere in Lower Cretaceous
Laurasia. The northern hemisphere provided accommodation for at least six distinct groups
of mammals.
By the end of the Cretaceous, half of them appear to have disappeared. There is a Campanian
record of a dryolestid from Wyoming (one molar), so perhaps that line was holding out
somewhere. Alternatively, its late occurrence could have been due to a southern dryolestid
invader, as faunal exchanges were sometimes possible.
Nevertheless, the radiation of 'northern cutters' coincided with the disappearance of a
number of other branches of the Mammalia tree, and most the ecological niches fell into, or
were grasped by boreosphenidan paws. (This doesn't seem to be the case for larger
eutriconodont predators, eg. Repenomamus.
The supply of their remains presently dries up long before the arrival of suitably sized,
potential 'northern cutter' competitors.)
It's tempting to assume we boreosphenidans ran riot,
and only the multis were able to persist (and indeed flourish) in their omnivore-herbivore
bastions. Simple. Tribosphenic molars conquered
Laurasia; a victory for high-toothnology.
'Southern cutters'
If this success were simply attributable to high-tech teeth, then parallel developments
might have been expected in Gondwana. After all, it presently seems
australosphenidans ('southern cutters') predate
their northern colleagues by about 25 million years. All else being equal, Los Alamitos
should've been under 'southern cutter' domination. As it wasn't, all else was presumably
not equal, and tribosphenic molars can't necessarily buy you love nor ensure the lion's
share of available ecospace.
Anybody for sex?
The apparent non-dominance in what little is known of Upper Cretaceous Gondwanan Mammalia
is due to some very interesting factors, although I've got no idea what they are. As sex
frequently comes to my mind, reproductive strategy could, possibly, perhaps, but not
necessarily be one of them. Both existing boreosphenidan lineages produce live young, and
logic demands that also applied for their most recent common ancestor.
Assuming the egg-laying monotremes are living
australosphenidans (which isn't necessarily the case), then that egging habit would surely
have been pursued by the entire lineage, excepting for the remote possibility of an unknown,
independent outbreak of live-birthers among them.
That certainly would've been a difference, and what happened after conception could
conceivably, possibly, perhaps, but not necessarily have been a significant difference. In
any event (and bearing in mind the paucity of relevant fossil faunas), 'southern cutters'
don't appear to have ever dominated Gondwana to anything like the extent that 'northern
cutters' achieved in Laurasia (and eventually the world), despite a 25 million head start.
Yet more speculation
From what's known of extant monotremes, neither the
platypus nor short-beaked echidna can be
considered fast breeders, and maternal care of hatchlings is required for several months.
(This information is too thin to carry much weight with regards to ancestral habits, as it
could be derived, but a wider survey is unlikely to be
available.) Neither has the possibility of quick production of lots of babies, whereas
some boreosphenidans are very capable of breeding like rabbits (or possums).
Further Mesozoic site summaries can be found at Localities.
The Mesozoic Mammals of Patagonia (not including the Allen Formation)
The species are mostly from the Los Alamitos fauna with others coming from La Colonia
Formation. Also listed are a couple of Paleocene mammals from neither formation. A
separate coral for the Upper Cretaceous Allen Formation is below.
Triconodonta-like
Austrotriconodon mckennai;
A. sepulvedai (Upper Cretaceous)
Docodonta? (or Dryolestoidea).
Reigitherium bunoduntum (Upper Cretaceous)
?Multituberculata.
Argentodites coloniensis (Upper Cretaceous).
Note: This interpretation has been challenged. An alternative view sees this 'genus'
as being a ferugliotheriid gondwanatherian.
Dryolestoidea (Upper Cretaceous unless otherwise
stated)
Barberenia araujoae;
Bondesius ferox;
Brandonia intermedia;
Casamiquelia rionegrina;
Coloniatherium cilinskii;
Groebertherium stipanicici;
Mesungulatum houssayi;
Quirogatherium major;
Reigitherium bunodumtum (if not a docodont);
Peligrotherium tropicalis (Paleocene)
?Dyolestida (Upper Cretaceous)
Notes: i. I'm not overly confident that the following are necessarily dryolestidans,
rather than 'merely' dryolestoids.
ii. In thier 2009 published study on mammals from the Allen Formation (termed Rougier et
al, 2008 in my bibliography), the authors found no justification for recognizing two
distinct species of Groebertherium. They accused G. novasi of being a junior
synonym of G. stipanicici.
Alamitherium bishopi;
Leonardus cuspidatus;
Parungulatum rectangularis;
Rougiertherium tricuspes
Gondwanatheria (Upper Cretaceous unless otherwise
stated)
Ferugliotherium windhauseni;
Gondwanatherium patagonicum;
Sudamerica ameghinoi (Paleocene)
Additional locality, the Allen Formation (Campanian-Maastrichtian)
The following is based upon my reading of Rougier et al, 2008, and thanks are due to the
supplier. The page numbering of my copy differs to that of the published study.
Cretaceous mammals were first struck in Patagonia at Los Alamitos in Rio Negro Province.
That pressed researchers into trying their luck elsewhere and, eventually, Chubat Province
was persuaded to add La Colonia Formation as a second source. Not wishing to settle for a
draw, Rio Negro went back on the attack and, thanks to fine footwork by busy paleo pixies,
the Allen Formation provided a third locality named Cerro Tortuga. Rougier and friends
were describing specimens from there (p.1).
A metaphorical matchbox
The amount of specimens they had wouldn't have filled even a small matchbox, but they
happened to match best with remains known from Los Alamitos Formation as far as the
genera went. However, there were distinctions to justify the establishment of new species
and one genus. As with the other Patagonian localities, there's a complete lack of either
marsups, placentals
or their direct ancestors. This strikes me as being problematic for the view espoused by
some researchers, for example Tom Rich, that has referred to Lower Cretaceous Australian
fossils (Ausktribosphenos) as being
possible early placentals. If Gondwanan in origin, which I personally strongly doubt, this
continuing absence of any therians in Patagonia is difficult
for me to understand. These sites are getting on for fifty million years later than
Ausktribosphenos; plenty of time for a placental expansion over all of Gondwana.
These mammal faunas are dryolestoid dominated; fairly distant relatives of therians (p.2).
Unpublished mammals from Bolivia, far north of the ancient Patagonian archipelago, also
provide dryolestoid-like critters and other non-therians. This is a strong contrast to
the therian domination of Lower Paleocene South America; a blink of a geological eyelid
later. Should the cradle of placentals indeed turn out to be Gondwanan (I think not),
then perhaps Upper Cretaceous South America should be termed the old folks' home.
Hi Allen
The Allen Formation is partially exposed at Cerro Tortuga, and mammal fossils were
collected from the foot of that exposure. This doesn't equate to the lower part of the
formation, as that doesn't happen to be on view there. Rather, in terms of the stratigraphy,
this happens to be about 38 metres below the top. The rock built up in predominantly
non-marine conditions according to the commonly occurring freshwater molluscs. Other
ancient deadlings include fish, bits of snake and turtles. They share the fossil bed with
dino egg shell and biologically produced fertilizer known as coprolites or, in politer
terminology, crap.
The Cretaceous-Tertiary boundary is in the formation above. Therefore, these deposits
are older. Faunal similarities suggest a similar sort of age as Los Alamitos and La
Colonia. There are some differences among the mammals. "Conspicuous
gondwanatherians" are reportedly absent at La Colonia and
the Allen formations. As ferugliotheriids do occur at Cerro Tortuga, I suppose that refers
specifically to sudamericids and perhaps some uncertainty as to whether feruglios are
gondwans. (These authors tentatively refer to feruglios as perhaps
multituberculates.) Whether the faunal
differences are due to temporal, environmental or preservation biases is as yet unclear.
There are some grounds for thinking that the Los Alamitos mammals could be a bit younger
than those from the other localities, but not by much.
Meet the Allen mammals
Dryolestoidea
Barberenia allenensis;
Cf. Brandonia;
Mesungulatum lamarquensia;
Groebertherium stipanicici
Gondwanatheria
Tropalcotherium
matuastensis
|
| Genus: Coloniatherium
Rougier GW, Forasiepi AM, Hill RV & Novacek M (2009)
'Colonia beast'
Family: Mesungulatidae
Remarks: More information will follow at some stage.
Meanwhile, during the fifth season of the year in Rheinland, Germany...
Kölle alaaf!
By selecting this magnificent generic name, which actually honours La Colonia Formation
from whence the remains came, it's possible the authors might find themselves receiving
invitations to attend Karneval gatherings in the German city of Cologne. The fifth
season of the year starts precisely at 11.11am on the 11th of November each year, and
carries on (with extremes of silliness and frivolity) until and including Shrove Tuesday.
There are parties, parades, parodies and more parties. Oh, and plenty of glasses of
Kölsch beer.
Presumably unbeknownst to the authors, many citizens of the place take to calling it
Colonia rather than the more usual Köln. With a bit of luck, 'Colonia beast'
could get adopted as a mascot for the annual madness.
As one of the many suitably silly songs says: "Vi-va Colonia!" |
| Species: | Colonia cilinskii Rougier et Al, 2009 |
| Place: | La Colonia Formation,
Patagonia |
| Country: | Argentina |
| Age: | Upper Cretaceous |
| Remarks: | More information will appear some time. |
| Reference: | Rougier et Al (2009), New mammalian remains from the Late
Cretaceous La Colonia Formation, Patagonia, Argentina, Acta Palaeontologica Polonica,
54(2), p.195-212. |
Genus: Groebertherium
Bonaparte JF, 1986
Aka: Groeberitherium
Remarks: The upper molars: "are dominated by two cusps,
the stylocone and paracone", (Clemens et al, 2003). This is similarly the case in
Laolestes, a Jurassic dryolestid. |
| Species: | Groebertherium stipanicici Bonaparte JF, 1986 |
| Aka: | G. novasi Bonaparte JF, 1986 |
| Place: | Los Alamitos Formation & Allen Formation,
Patagonia |
| Country: | Argentina |
| Age: | Campanian, Upper Cretaceous |
| Remarks: | More upper molars.
With thanks to Vince Ward for the author, year, and correct species spelling.
The following is based upon my reading of Rougier et al, 2008 and thanks are due to the
supplier. 2008 is the year on my prepublication copy (the actual publication was early
in 2009), and the page numbering of both versions also differs.
The Allen Formation provided one upper molar referable to this species (p.6). It's a
small dryolestoid by Patagonian standards, about a third the size of it colleague
Mesungulatum; maximum length (for this specimen)
1.16mm, max. width 1.73mm. The crown is tall, lacks cingula and is something like
symmetrical with an elongated trigon of cusps. As it's very similar to the earlier
established Groeberitherium from other localities, it didn't warrant a new species.
The trigon doesn't actually feature a metacone. That being the case, some might be
tempted to let this trigon be a bigon, but you'll be relieved to hear I'm not going to
write any such possibly confusing nonsense. Little wear is evident, so it seems the
absence of a metacone is not an effect of damage or erosion (p.7). The paracone is a
higher cusp than the stylocone.
Specific euthanasia and family squabbles
Unpublished data indicates fossils previously assigned to G. stipanicici and
G. novasi actually belong to only one species. The second mentioned species was
executed by firing squad.
Originally, Groeberitherium was referred to the family of Dryolestidae. This was
due to the lack of cingula on upper molars, lower molars featuring short
trigonids and a somewhat wide metacristid crest.
However, the large stylocone at the middle of the stylar area on uppers, and the fact
that this cone isn't connected with the paracrista crest, both speak against dryolestid
membership. It may well be a more basal player in the
lineage that led to Patagonia's mesungulatids.
Holotypes
The original holotype, MACN-RN 13, managed to get badly damaged after making its debut in
print, and has been rendered uninformative. Therefore, a neotype was elected by
Rougier et al, 2008.
The job was won by MACN-RN 19, a candidate who's also the type fossil of the now defunct
G. novasi Party. Both may be petted in the Museo Argentino de Ciencias Naturales
Bernardino Rivadavia Colleccion Rio Negro, but please be gentle whilst so occupied. |
| Reference: | Bonaparte (1986), Sobre Mesungulatum houssaysi y
nouvos mamiferos cretacicos de Patagonia, IV Congreso Argentino de Paleontologica y
Biostratigrafia, Actas 2, p.48-61. |
| Supposed genus: Guirogatherium
Aka: ??Guimarota
Remarks: I don't believe this reported generic name, which I've seen attributed to Bonaparte,
1990. I've been unable to find any confirmation for it and am now assuming that it's a
miss-spelling of Quirogartherium. |
| Supposed species: | Guirogatherium freyi |
| Place: | |
| Country: | |
| Age: | |
| Remarks: | Supposedly Bonaparte JF, 1990. I doubt it.
Perhaps the species name has some significance or other. |
| Reference: | |
| Genus: Mesungulatum
Bonaparte JF & Soria MF, 1985
'Mesozoic ungulate'
Family : Mesungulatidae Bonaparte JF, 1986 |
| Species: | Mesungulatum houssayi Bonaparte JF & Soria MF,
1985 |
| Place: | Los Alamitos Formation,
Patagonia |
| Country: | Argentina |
| Age: | Campanian, Upper Cretaceous |
| Remarks: |
Based on the crown of a molar. This was the first description
of Cretaceous mammal material from Argentina. It was originally described as a
placental. New analysis, (Gelfo and Pascual, 2001), has
referred it to Dryolestida. That paper is linked to Peligrotherium. (With thanks to
Martin Jehle for pointing this out).
"The occlusion between upper and lower molars of Mesungulatum houssayi shows a
shearing stage of the food in which the mesial and distal cristae worked as scissors, and a
crushing stage in which the lower molar cristae worked against the upper
cingula", (Gelfo & Pascual 2001, p.377).
A referred upper molar has a length of over 4mm. That suggests this is one of the largest
Cretaceous dryolestidans (or at least dryolestoids), (Clemens et al 2003). |
| Reference: | Bonaparte & Soria (1985), Nota sobre el primer mamifero
del Cretácio argentino, Campaniano-Maastrichtiano (Condylarthra). Ameghiniana 21 (2-4),
p.177-183. |
| Species: | Mesungulatum lamarquensis Rougier et Al, 2009 |
| Place: | Allen Formation,
Patagonia |
| Country: | Argentina |
| Age: | Upper Cretaceous |
| Remarks: | The following is based upon my reading of a
prepublication copy of the original description (which is listed in my bibliography as
from 2008). It also has different page numbers. Thanks are due to the supplier. The
study by Rougier and colleagues was formally published early in 2009, so that's what the
correct citation must be.
This is one of South America's strange seeming "Upper Jurassic" survivors from the Upper
Cretaceous; an ancient and originally northern lineage which, after its virtual disappearance
from the known fossil record, somehow staged a come back in the south (p.5). This impression
will probably diminish in oddness as the Gondwanan fossil record becomes better known, but
I can't wait that long before writing these notes. At least, I don't want to. It's a
dryolestoid; similar in size to Mesungulatum
houssayi, but different enough for a distinct species. For example, on upper molars
of this species, the stylocone isn't shifted lingually,
the outer wall of the stylocone is more vertical and the whole structure is positioned
close to the buccal edge of the crown. The
cingula are wider and give the tooth more of a rectangular
outline rather than the more triangular one for M. houssayi. There are other
divergent details as well, but let those suffice as examples. Two specimens were found
among the collection, and a fragmentary tooth could perhaps be a third.
Live fast, die young
Both the confidently assigned teeth are upper molars. The
type fossil used to have roots, although they failed to survive the resting in pieces though
the millions of years. Fairly often, after a journey through the digestive system of a
crocodile, fossilized mammal teeth can be formed of the dentine structure stripped of the
surrounding enamel. This one's somehow managed the opposite trick. The enamel survived in
good nick, but the tooth it once surrounded has mostly gone. That, along with the large
pulp cavity, suggests a James Dean like approach to life, at least as far as the dying
young bit went. It was presumably immature as teeth go, and hadn't full mineralized. Signs
of wear are also lacking excepting for on the tip of the paracone.
The tooth originally had three roots; one beneath the paracone, the dominant cusp, and two
on the buccal side. The next largest cusp is the buccally positioned stylocone. As normal
for the family, no distinct metacone is part of the armoury.
A second complete, but heavily worn, molar is probably an upper left one. Various details
have been obliterated. It's of a similar size but seems to represent a different position.
A further fragment of a mesungulatid tooth suggests a somewhat larger original. It's part
of a lower molar, and may belong to this species (p.6).
Size
Upper molars (2 specimens): maximum length both 4.05mm; max. width 5.29-5.62mm.
Holotype
The type fossil may be congratulated in the collection of the Museo Municipal de Lamarque.
It's an upper molar known as MML-PV11, and the specific
name pays homage to its new home city. |
| Reference: | Rougier GW, Chornogubsky L, Casadio S, Arango NP &
Giallombardo A (2009), Mammals from the Allen Formation, Late Cretaceous, Argentina,
Cretaceous Research, 30(1), p.223-238. |
| Genus: Peligrotherium
Bonaparte JF, Van Valen LM & Kramartz A, 1993
'Peligro beast'
Family : Mesungulatidae Bonaparte JF, 1986 (according to Rougier et al, 2009)
Original placement : Peligrotheriidae Bonaparte JF, Van Valen LM & Kramartz A, 1993 |
| Species: | Peligrotherium tropicalis Bonaparte JF, Van Valen
LM & Kramartz A, 1993 |
| Place: | Punta Peligro, Salamanca Formation,
Patagonia |
| Country: | Argentina |
| Age: | Lower Paleocene |
| Remarks: | The following is based upon my reading of Gelfo
& Pascual, 2001.
Originally, Peligrotherium was held to be a
placental mammal, and possibly a condylarth, (p.369). This was due to details of
lower molars and an inferred dental formula. However, the
subsequent discovery of upper teeth associated with lowers supported an already proposed
revision. None of the molars are in any way tribosphenic,
and they seem to be derived from pre-tribosphenic ones; dryolestidan teeth. The closest
resemblance is with Mesungulatum. Peligrotherium
is a surprisingly late dryolestidan.
The original fossils consisted of part of a dentary with
three postcanines, and six fragments of further lower
jaws, (p.370). The state of preservation made interpretation difficult. In 1999, the
genus was tentatively reassigned as a dryolestidan, and this has since been confirmed. The
new material described in 2001 consisted of partial maxillae
and a dentary from the same individual.
This animal was large for a dryolestid, (p.371). Typically, its relatives were small
insectivores. However, the Upper Cretaceous Patagonian versions were atypical, and this
Paleocene genus followed their offbeat drum. Nothing is known about the numbers of
incisors or canines. Both
upper and lower postcanines number perhaps two premolars
and assuredly five molars per side. The first two molars are hyptertrophied, and sizes
decrease along the line from position 1 to 5. The upper molars have strange numbers of
roots, and talonids lack visible cusps. In dryolestids,
talonids are usually, low, triangular and equipped with a cusp termed a hypoconid.
Upper postcanines
"On the upper cheekteeth, both the crown morphology and the number and arrangement of
the roots are quite unusual", (p.371-372). Three distinct wear facets are present.
One corresponds to the paracone, (p.373), and the other two indicate a
cingulum joined to a stylar cusp. The largest molar, M1,
has a length of 11.65mm on the labial side, and a maximum
width of 11.8mm. Compared to earlier dryolestoids from the northern hemisphere, these
teeth are enormous; roughly ten times the more traditional sizes.
The M1 has four main roots, (p.374), and four is also the apparent number for the M2. The
next two molars are triple-rooted. Their lower counterparts are content with two each.
Not a tentative condylarth
The hypertrophied state of the first two lower molars is a similarity known from a
condylarth, (Periptychus), but this seems to be a matter of convergence, (p.375). The
upper molars aren't like those of any tribosphenic animals. The main cusp is on the
lingual side, (the paracone), and not the labial as with
condylarths, (the protocone). The lower molar has no basined talonid to accommodate this
cusp.
The holotype
The holotype is a right dentary with m1 and m2. UNPSJB PV 914 is a resident of the
Universidad Nacional Norpatagónica San Juan Bosco, Conodoro Rivadavia. The specific name
is incorrect in terms of Latin grammar, (with thanks to David Marjanovic). However, as a
correction hasn't yet been published, it's scientifically valid. |
| Reference: | Bonaparte et al (1993), La fauna local de Punta peligro,
Paleoceno inferior, de la provincia del Chubut, Patagonia, Argentina. Evolutionary
Monographs 14, p.1-61. |
| Link:
Gelfo JN & Pascual R, Geodiversitas 2001, 23 (3), p.369-379.
http://www.mnhn.fr/publication/geodiv/g01n3a4.pdf
Peligrotherium tropicalis (Mammalia, Dryolestida) from the early Peleocene of
Patagonia, a survival from a Mesozoic Godwanan radiation.
The full paper. |
| Genus: Quirogatherium
Bonaparte JF, 1990
'Quiroga's beast'
Family: Quirogatheriidae
Remarks: The generic name honours the late Juan C Quiroga, a pioneer paleontologist
from Argentina.
This is possibly an upper, dryolestid milk tooth,
(Averianov 2002, p.712). |
| Species: | Quirogatherium major 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).
If you were a paleontologist in Patagonia something like 75-80 million years ago, this
genus could well have been the mammal to look out for, especially if you were hungry.
Although based on but one right tooth, if a mammal has a four millimetre long upper
molar, then there's a strong probability its owner will be
able to offer you a good meal. I don't intend suggesting a bodysize on this basis but,
with some suitable accompanying plant produce, there may well have been enough meat
available to impress a couple of colleagues as well. Unless it was very secretive (or
inconveniently entirely nocturnal) this was a furry critter large enough to have been
readily spotted.
I'm tempted to mention how long rabbit molars are, but I don't happen to know. Should
anybody feel inclined to enlighten me: ktdykes@arcor.de.
(If possible please include the molar positions and whether uppers or lowers. And feel
free to include similar information for other small to middle-sized mammals as well.)
Meet a meaty barbereniid
You may have encountered Barberenia higher up this page.
This maxi-format relative is over twice the size (p.73). However, size isn't of all that
much relevance to classification, although it's often a helpful pointer.
Contrasts with Barberenia
The paracone and stylocone are closer together on the molar of Quiro, and the connecting
crest is both relatively higher and sharper. However, no basined depression occurs between
these two cusps. There's also a narrow depression between the line formed by the
stylocone, the two stylar cusps, and the sharp, high metacrista. For B., the
depression is larger and basined. The rear of Quiro's crown is adorned with a large bit of
cingulum shelving, especially on the
lingual side.
The basic plan was considered similar enough to refer both to the same family.
Holotype
MACN-RN 171 was the only specimen available. It's an upper molar and took up an offer of
accommodation at the Museo Argentino de Ciencias Naturales, Buenos Aries. The specific
name refers to its size. A maximum length of around 4mm qualified as large in comparison
to the other fossils collected. |
| Reference: | Bonaparte JF (1990), New Late Cretaceous mammals from the Los
Alamitos Formation, northern Patagonia. National Geographic Research 6, p.63-93. |
| Genus: Reigitherium
Bonaparte JF, 1990
'Reig's beast'
Family : Mesungulatidae Bonaparte JF, 1986 (accoriding to Rougier et al, 2009)
Original placement: Reigitheriidae Bonaparte, 1990
Remarks: On the basis of subsequent finds, this genus was controversially transferred to
an even more archaic group of mammals. Whereas Bonaparte opted for Dryolestoidea,
Pascual et al, 2000 settled for Docodonta, and that's the
view I followed. However, that's been widely challenged by other researchers. Presently,
I accept the placement of this genus in the family of Mesungulatidae as proposed by
Rougier et al, 2009. Should you rather have a docodont then:
revised Reigitherium.
The generic name honours Osvaldo A Reig for his research into evolution and the promotion
of Mesozoic vertebrate research in Argentina. (He subsequently died in 1992.) |
| Species: | Reigitherium bunodontum Bonaparte JF, 1990 |
| Aka: | Reigitherium bunodonta 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).
Reigitherium as a dryolestoid
All Bonaparte had available for this critter was a single
molar he interpreted as being an upper left one. Subsequently, in 2000, Pascual and
colleagues stated it was a lower molar, as they found it compared well to a tooth on a
partial dentary. I'm going to follow Bonaparte's original
opinion, although with some caution as it may be wrong. (This probably won't have
significance for other directional terms; eg. labial should
remain labial. Hopefully, somebody will review the situation sooner or later.
This 'upper' is a fairly rectangular crown in outline (p.76). The surface area which occluded
with the 'lower' is marked with furrows beginning from the 'paracone'. The cusp is large
enough to earn the epithet hypertrophied, and there's a depression incorporated into the brow
of its hill. The cusp is blunt as is the taller, but nevertheless rather indistinct
'stylocone'. Sadly for lovers of an ectoflexus, there's
none present. (My note: one wouldn't be expected on a lower molar.) Those hoping for a
parastylar cusp will also be disappointed. "Two transverse, inclined planes for a
V-shaped surface for occlusion with two lower molars." The front most of these is largest
and claims about two-thirds of the available occluding area.
Aberration!
Whatever the affinities of this mammal, dryolestoid or docodont, it was a weirdo. Both
these groups were typically baiters of beetles and worm-worriers, but this molar suggests
very different tastes; omnivorous to herbivorous (p.77). As Bonaparte saw things, this was
an atypical dryolestoid with ancestors not too unlike
Mesungulatum. In either case, this molar was a highly specialised implement for
an archaic lineage.
I suppose its vaguely comparable with Leonardo de Vinci's sketched flying machines from the
fifteenth-sixteenth century transition (a phrase indicating I'm not inclined to check the
year or years).There's a difference though. Reigitherium got its ornithopter to
fly.
Holotype
The type fossil, MACN-RN 173, lives at the Museo Argentino de Ciencias Naturales, Buenos
Aries. The specific names means 'hill tooth'. Some cusps are particularly rounded; more
like hills than peaks. Originally, it was written as bunodonta. However, a
correction was made in accordance with the genders of Latin grammar. |
| Reference: | Bonaparte (1990), New Late Cretaceous mammals from the Los
Alamitos Formation, northern Patagonia. Natl. Geogr. Res. 6, p.63-93. |
| Genus: Thereuodon
Sigogneau-Russell D, 1989
Family: Thereuodontidae Sigogneau-Russell D & Ensom P, 1998
Remarks: The remains consist of isolated upper teeth. Based on comparisons with
newly described Jurassic material from Portugal, Thomas Martin came to the conclusion that
these were milk teeth "of a dryolestid or a stem-group
zatherian," (Averianov 2002, p.712). I'll treat it as the former. It could just
as easily be the latter. |
| Species: | Thereuodon dahmani Sigogneau-Russell D, 1989 |
| Aka: | T. dahmanii |
| Place: | Anoual |
| Country: | Morocco |
| Age: | Berriasian?, Lower Cretaceous (early) |
| Remarks: | This was the first
'symmetrodont' to be reported from Africa. However, this interpretation now appears to
be unlikely. |
| Reference: | Sigogneau-Russell (1989), Découverte du premier Symmétrodonte
(Mammalia) du continent africain. Comptes Rendus de l'Académie des Sciences, Série II 309,
p.921-926. |
| Species: | Thereuodon taraktes Sigogneau-Russell D &
Ensom P, 1998 |
| Place: | Langton Matravers, Dorset |
| Country: | England |
| Age: | Lower Cretaceous (early) |
| Remarks: |
The following in based upon my reading of Sigogneau-Russell & Ensom, 1998.
I think I'll start with the health warning on page 455: "To sum up, in the present
state of knowledge, the monophyly itself of the
Symmetrodonta, as well as the inclusion of Thereuodon in this order, mainly on
account of the non-transverse metacrista shear, is tentative pending new discoveries from
the fossil record, or even further study of the existing fossil record." Whilst the
authors did indeed refer to this critter as a symmetrodont, and compared it to other
members of the order as then proposed, they clearly weren't convinced that this was the
taxon to which it belonged. These doubts appear to have been
fully justified. It also means that a far amount of the information contained within the
paper is actually of more relevance to other symmetrodonts, than it is for this directory.
A small team of small teeth
This species is based on five isolated upper teeth from the Purbeck Limestone, (p.447). In
various technical details, they most closely resemble the molars
of T. dahmani, (p.448), which neatly explains why they were referred to this genus.
There are some likewise technical differences, thus the separate species. For those who
appreciate such things: "Distinguished from T. dahmani by the
labial cingulum being
uninterrupted, the mediocrista being less acute, and possibly a greater protrusion of the
parastylar cusp; stylocone less sharp; metacone less well individualized; no cuspule
"c"; persistent but reduced facet A", (p.453).
The presence of the same genus in the fossil mines of Purbeckia and the somewhat younger
Lower K rocks of Morocco, poses an interesting question. How'd it happen? Europe and
Africa seem to have separated back in the Middle Jurassic, (Callovian), which means at
least 20 million years earlier. That is an improbable length of time for a common
ancestor.
O'er the sea to Sk..., um, North Africa
However, the sea which then separated the two continents seems to have been neither always
deep nor wide and, judging by the geology and available fossils, Southern Europe was
represented by a fine supply of islands. This provides a plausible route for mammalian
migration, especially as changes in sea level would have meant the temporary emergence of
more land; either as direct bridges and / or more islands as stepping stones.
Holotype
The holotype, DORCM GS 665, and its colleagues are in the collection of the Dorset County
Museum, Dorchester. It's a right upper molar of about 1mm in length. The species name
translates as 'perturbator'. This alludes to both the authors' questioning of the
relevance of this genus to Symmetrodonta, and the trouble it causes to those who study
these things, because of its apparent island hopping across the waters of the Tethys,
(p.451).
Time for tea
After visiting this museum, I suggest you turn right up the High Street and keep walking
for a couple of hundred yards. Try a cream tea in the old teahouse. Delicious. |
| Reference: | Sigogneau-Russell & Ensom (1998), Thereuodon
(Theria, Symmetrodonta) from the Lower Cretaceous of North Africa and Europe, and a brief
review of symmetrodonts. Cretaceous Research, vol 19, p.445-470. |
| Other reports:
Patagonia, Argentina
A dryolestidan was reported in October. Further information welcome.
Reference: Pascual R, Gelfo JN, Goin FJ, Reguero MA, Udrizar Sauthier DE & Balarino
L (2002), Un gran mamifero (Mammalia; Dryolestida) del Cretácio Superior de Patagonia,
Argentina. VIII Congresso Argentino de Paleontologia y Bioestratigrafia, Corrientes,
Argentina -(October 2002).
http://exa.unne.edu.ar/eventos/congresos/paleontologia/public_html/programa1.htm
Lightning Ridge, Australia
The opal fields of New South Wales are the source of a wide variety of fossils from the
Lower Cretaceous, (Aptian-Albian). One discovered by Edward Long is enigmatic. It's a
natural mould of a vertebrate tooth, which doesn't
correspond to any other known elements of the fauna. It was found at the interestingly
named 'Vertical Bill's claim' in Three-Mile Field, and is now in the collection of the
Australian Museum, Sydney. (p.232). It's not in good condition and any interpretation is
presently tentative. The crown is roughly triangular and possesses at least
molar-like cusps. Clemens et al (2003) found that it most
closely resembled a dryolestid upper molar. Unfortunately, there's no trace of the root or
roots, (p.233). This helps explain why they classified it as "synapsid?".
Should it be from a dryolestid, this would have been an unusually large one. The tooth is
12 millimetres long and 14 millimetres wide. That's roughly five or ten times the
'standard range'. The authors also note some similarities with peculiar 'notosuchian'
crocodiles known from elsewhere, and Triassic non-mammalian
eucynodonts, traversodontids, (p.234). Solving
this enigma would seem to be dependant upon finding better preserved specimens, so keep
digging.
Reference: 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.
Forest Marble Formation, England
Sigogneau-Russell, 2003b (p.524) reports on the rear half of a right lower
molar, which has been recovered from the Middle Jurassic
Kirtlington Bone Bed, Oxfordshire. In some ways, its morphology is close to
Henkelotherium, (next section). However, a wide cingulid on the internal side
(lingual) isn't known from any other dryolestoid. She
concludes: "This, combined with the very tall protoconid, certainly testifies to a
different line of Dryolestida."
Also in this paper are two fairly large lower molars from Watton Cliff, Dorset. They might
represent dryolestoids. She classifies them as
Trechnotheria indeterminate. |
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, March 2005. Last update: 6.6.2009.
Ktdykes@arcor.de |
Bibliography:
Averianov AO, (2002), Early Cretaceous "symmetrodont" mammal
Gobitheriodon from Mongolia and the classification of "Symmetrodonta".
Acta Palaeontologica Polonica 47 (4), p.705-716.
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.
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.
Ensom PC & Sigogneau-Russell D (1998), New dryolestoid mammals from the basal
Purbeck Limestone Group of southern England. Palaeontology, 41(1), p.35-55.
Gelfo JN & Pascual R (2001), Peligrotherium tropicalis (Mammalia,
Dryolestida) from the early Paleocene of Patagonia, a survival from a Mesozoic Gondwanan
radiation. Geodiversitas 23 (3), p.369-379.
Kemp TS (2005), The Origin and Evolution of Mammals, Oxford University Press,
pp.331.
McKenna MC & Bell SK, (1997), Classification of Mammals Above the Species Level.
Columbia University Press.
Pascual R, Goin FJ, González, Ardolino, A & Puerta PF (2000), A highly derived
docodont from the Patagonian Late Cretaceous: evolutionary implications for Gondwanen
mammals. Geodiversitas 22 (3), p.395-414.
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.
Sigogneau-Russell D (2003b), Holotherian mammals from the Forest
Marble (Middle Jurassic of England), Geodiversitas, 25 (3), p.501-537.
Sigogneau-Russell D & Ensom P (1998), Thereuodon (Theria, Symmetrodonta)
from the Lower Cretaceous of North Africa and Europe, and a brief review of symmetrodonts.
Cretaceous Research, 19, p.445-470. |
