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.
Looking for books?
You could visit the
Book Centre and look around.
| These two taxa of
marsupials are best known from South America. It's
long been suspected they were descendants of immigrants from North America, who probably
arrived during the latter stages of the Upper Cretaceous. However, towards the end of
2004, genera of both groups were accused of coming from the North American Cretaceous. If
the interpretations are correct, then the radiations began before disembarkation. This
directory is centred on the alleged Mesozoic members. The true polydolopimorphians are
extinct, but the ameridelphians live on. They include all existing American marsups.
A brief introduction to marsupials
The following has been written with reference to Kemp, 2005 (p.190-192).
As marsupials use their teeth for all kinds of everything, there's plenty of variation among
the roughly 270 extant species. Nevertheless, these are variations on one ancestral theme.
The original dental formula was (per side): (uppers): five
incisors, one canine, three
premolars and four molars; (lowers): four, one, three and
four respectively. Tooth replacement involves only the third premolar. All other teeth
are primary, but eruption can be delayed. For example, delayed eruption allows kangaroos
to replace worn primary molars with fresh ones.
Molars
The original model was highly distinctive from other mammals. The metacone and paracone were
towards the middle of the crown, and there was a wide shelf on the
labial side; the stylar shelf. This was equipped with up to five cusps named from A to
E.
The lowers had the paraconid on the
lingual side. The talonid
had three cusps. Of these, the hypoconulid and entoconid were twinned; ie. close. The
hypoconid was set well apart from them.
Skull and body (p.191)
"There are several diagnostic characters of the marsupial skull, including the foramen of
the lacrimal lying external to the orbit, an alisphenoid
component to the auditory bulla, a pair of palatal fenestrae, and an inflected angular
process of the dentary."
The rest of the skeleton is less distinctive, but ankles (and wrists) have unifying
details. Distinctions from other mammals exist in the soft tissue of the body, but these
aren't likely to be available for fossil specimens. The brain is typically smaller than in
placentals. If you tell an assembley of marsupials
they're comparatively stupid, they wouldn't have the faintest idea what you meant. As a
consequence, attempting any such thing would be a demonstration of your own daftness.
The most basal of living marsupials are the didelphids of
America, a conservative family of 65 or so species.
|
A. "Polydolopimorphia" B. Ameridelphia
| Taxon: "Polydolopimorphia" (Ameghino, 1897)
The definition I'm following is in Case, Goin & Woodburne, 2004, (p.228-229). This
order is given as Marsupialia incertae sedis, and isn't assigned to the
ameridelphians. It consists of three suborders: Hatcheriformes, Bonapartheriiformes and
Polydolopiformes. Used in this sense, the order is extinct.
It's typically South American and post-Mesozoic in distribution. However, my concern is
with Mesozoic mammals, and those genera are North American.
Authorship
Case and Co attribute the taxon thus: (Ameghino, 1897). Mc
& Bell blame the name on Marshall, 1987, and report it was proposed as a suborder.
They also state:
"Sometimes incorrectly attributed to Ameghino, 1897. Not the same
concept as "†POLYDOLOPIMORPHIA" Archer, 1984:786, meant to include only
†Polydolopidae, †Prepidolopidae, †Glasbiidae, †Caroloameghiniiidae, and †Bonapartheriidae.
If †POLYDOLOPIMORPHIA were to prove useful, it would date from Archer, 1984, even though
Archer's proposal was tentative (see International Code of Zoological Nomenclature, Article
1).;"
Here it's used as an "order", not a sub- or a superorder, and the authorship citation is in
brackets.
Cretaceous polydollies?
In 2004 Case et al accused the following three NAm-K genera of having polydolly membership
cards: Ectocentrocristus,
Hatcheritherium and Glasbius. If so,
then polydolly sexual expression was presumably first consumated in North America. Fruits
from those deeds later found their way to South America and, for millions more years,
their descendants kept bonking riotously. I should say those aren't quite the terms Case
and colleagues use. (I'll also mention their paper sometimes gets cited as dating from
2005. However, my copy's got 2004 written on it!)
The first publication I saw that pulled the blankets from this delightful scenario was the
work of Davis, 2007. He was revising ancient NAm marsups called pedis
(Pediomyoidea). Anyway, I like to think of what
happened as follows although, again, these aren't quite the terms the author uses. For
example, any sex attributions are my own fabrications. You can't really sex isolated
molars.
He happened to have a red-blooded, all American, male Glasbius molar in his
collection. When put into a little bed with some completely naked polydolly-dollies, rather
than reacting by... He shrieked in horror, bolted from the love nest and locked himself in
a convenient drawer. So distressed were the screams, that Davis conclued either he can't
have been a polydolly at all or, if so, then a thoroughly gay and unhappy one.
As things turned out, the drawer he took refuge in contained a number of completely naked, female
pedi molars from various genera and species. After a while, the impeccably well-mannered
researcher couldn't help but hear noises of an amorous and sporting nature. To use the
specialized terminology of Australian scientists, the Glasbius male had clearly
developed an anatomical condition known as a stiff one-eyed trouser snake of
scaled down anaconda proportions. Surely not simply out of jealousy, it was clearly good
manners, Davis didn't peep in until small twirls of cigarette smoke coming out of the
keyhole indicated all events had reached their conclusions, rather as white smoke coming
from a chimney sometimes shows when an orgy of cardinals has climaxed at the Vatican.
Although unsure as to which pedi maiden had fanned his fandango, the male molar must
certainly be that way inclined, rather than having polydolly tendencies.
And then came a publication by Beck et Al, 2008 (thanks for the notification and copy,
Robin). This study concerns an early Pliocene northeast Australian marsup named
Numbigilga. I hardly need say that's Gugu-Yalanji for 'small bandicoot imitator'.
Less obvious is what a four million year old bit of jaw and an upper tooth might have to do
with Cretaceous "polydollies". Not a lot, directly speaking. However, these authors had
a look at the supposed polydolly criteria identified for Ectocentrocristus and
Hatcheritherium, and found them unconvincing in both cases (see discussion on page
759). Some of the characters cited are common enough in generalized marsups of various
affinities, and thus not necessarily indicative of polydolly-ism. To sum up (with
references omitted here): "Rejection of this hypothesis is more congruent with the complete
lack of undoubted marsupial (or even therian) fossils from pre-Paleocene deposits of South
America (the oldest undoubted South American therian is a probable polydolopimorphan from
the earliest Paleocene...), which instead contain a diverse range of non-therian
mammals..."
For bookeeping reasons, I'm presently retaining an emended version of the scheme proposed
by Case et al, 2004. However, unless it's used as a strict reference to the genuine
polydollies, all variants of "Polydolopimorphia" on this directory should have those
inverted commas round them. In general, don't take it literally.
Additional note on glasbiids
In line with the findings of Davis, 2007, I've relocated Glasbiidae. It's now
within Pedimyoidea.
Genera: Ectocentrocristus,
Hatcheritherium,
other reports
Time-Line:
Upper Cretaceous: Ectocentrocristus, Hatcheritherium |
| Genus:
Ectocentrocristus Rigby & Wolberg, 1987
Aka: Alphadon (partly) |
| Species: | Ectocentrocristus foxi Rigby JK & Wolberg DL,
1987 |
| Aka: | Alphadon cf rhaister |
| Place: | Judith River Formation, Montana & New Mexico |
| Country: | USA |
| Age: | Campanian, Upper Cretaceous |
| Remarks: | To open with a however
Beck et al, 2008 (p.755) casts doubt upon the polydolly affinities of this genus, as
mentioned below, and even upon the nature of the tooth in question. Various authors have
pointed out the possibility that this 'genus' may be based upon molar-like
milk-premolars; a kid for a marsup such as
Turgidodon. This wasn't addressed in the
paper this entry is currently based upon.
The following is based upon my reading of Case,
Goin & Woodburne, 2004.
This genus was originally referred to Didelphidae, a family of some ill-repute. Case and
colleagues reassigned it to Polydolopimorphia, (p.229).
Remains are restricted to isolated upper and lower molars,
and the holotype is an upper left one, (probably the M3). It's fairly large compared to
many Mesozoic mammals, with a length of 3.9mm. From the
occlusal perspective, the crown is roughly triangular, (p.230). The
labial side has no ectoflexus,
and there's a row of five stylar cusps. These diminish in size from front to back, with
cusp E being tiny. There are naturally an array of other features, several of which will
be mentioned.
The tooth was referred to Alphadon in 1966,
(p.231). However, the molars of such peradectids have a ridge termed the centrocrista, and
this isn't highly invasive of the stylar shelf. It is on this tooth, (p.232). Also the
relative sizes of the stylar cusps differ to the scheme in this genus, (eg. D is the
largest in peradectids). The form of the centrocrista in Ectocentrocristus is
characteristic for polydolopimorphians, who are best known from post-Cretaceous times in
South America. Further characteristics are also in common with
basal members of that group.
Holotype
The holotype, AMNH 77372, is a left upper molar. It's in the collection of the American
Museum of Natural History, New York. |
| Reference: | Rigby & Wolberg (1987), The therian mammalian fauna
(Campanian) of Quarry 1, Fossil Forest study area, San Juan Basin, New Mexico, in Fassett JE
& Rigby JK (eds.) The Cretaceous-Tertiary Boundary in the San Juan and Raton Basins,
New Mexico and Colorado, Geological Society of America, p.51-80. |
| Genus: Hatcheritherium
Case JA, Goin FJ & Woodburne MO, 2004
Aka: Alphadon (partly); Hatcheria
'Hatcher's beast'
Remarks: The generic name honours the collector of the fossils, John Bell Hatcher. If this
is who I think it is, then he had to wait very patiently indeed. Assuming he isn't a
namesake, Hatcher was an experienced fossiler, whose efforts included campaigns in
Patagonia from 1896-1899, (Simpson, 1980, p.15).
The name Hatcheria was already owned by a fish. Slightly distracting are the
mischievously frequent appearances of the incorrect name in the paper. It's more commonly
cited than the correct one, and this may be a curious, unlooked for world record. I'd
imagine the preoccupation must've been spotted late. Such cases are much easier to notice
with the benefit of hindsight. |
| Species: | Hatcheritherium alpha Case JA, Goin FJ & Woodburne MO,
2004 |
| Aka: | Alphadon cf. A. rhaister (partly); A. cf. A. rhiaster;
Hatcheria alpha |
| Place: | Lance Formation, Wyoming |
| Country: | USA |
| Age: | Maastrichtian, Upper Cretaceous |
| Remarks: | The following is largely based upon my reading of
Case et al, 2004. However, in the light of a later publication, Beck et al, 2008 (thanks
due to Robin), caution is required. As stated on page 755 and discussed in the paper,
Beck & colleagues reject the referral of 'Hatcher's beast' to Polydolopiorphia. If correct,
that clearly has implications for various aspects of this entry as presently written. It
also causes me to add some inverted commas. For example, should true polydollies have
first evolved in South rather than North America, then an explanation for their dispersal
from the North is redundant. Even so, as I happen to have added thoughts on that from
another source as well, it may still be of some interest. Besides, some marsups or other
do appear to have migrated south.
This genus is represented by a couple of upper molars. The
teeth are reasonably sized for a mammal of the Mesozoic, with their width exceeding the
length, (holotype: length 3,1mm against a width of 3.5, p.233). A ridge termed the
centrocrista has a V-shape. Four stylar cusps are present on the
labial side: B > D > A > C. The other specimen has a
length:width ration of 3.6:3.9mm. This size differential may have much to do with tooth
position; RM3 for the holotype, RM1 for its companion.
In 1966 both specimens were referred to Alphadon, (p.234). However, the cusps are
rounded; the crowns are low; and the centrocrista is invasive. These aren't characteristics
associated with peradectids. In particular, the centrocrista behaves as in
polydolopimorphians. Along with the earlier (but more derived)
Ectocentrocristus, this indicates northern origins
for that predominantly South American order.
Northern born southerners?
"Polydolopimorphian" and didelphimorphian marsupials are (or were) overwhelmingly residents
of South America. The polydollies are extinct, but opossums are living didelphimorphs. It's
long been recognised that there were affinities with animals of the North American
Cretaceous. What Hatcheritherium and Nortedelphys
suggest, is that these groups may have first emerged in the north, and then migrated,
(p.244). There are several possible modes for incursion. For example, when it comes to
small animals, founding populations can be transported surprising distances over oceans.
Seafaring wraiths
This is a short diversion from the paper and actually of limited relevance. Nevertheless,
it's an interesting illustration of what does happen today, and doubtlessly reflects events
in the past. The source is Lavers, 2003, p.240-242. (The English language original was
published in 2000).
"Aber jüngst ergab sich doch eine Gelegenh..." Whoops, that was German.
If you were to slice the tail off a green iguana, the animal would be both about forty
centimetres long and justifiably annoyed. In October 1995, a large raft of driftwood and
downed trees came ashore on a beach in Anguilla. The passengers, at least fifteen iguanas,
disembarked and moved in. They probably didn't construct the craft themselves. That was
done about a month previously by an obliging hurricane named Luis. A fortnight later his
smaller colleague, Marilyn, appears to have decided the course. Most probably, the voyage
had begun in the Guadeloupe Islands, which are about 300km southeast. Iguanas were still
lounging on the beach in March 1998, and one of the ladies appeared to be obviously
married. I can't imagine any other explanation for her pregnancy. Relatively large
animals, (especially ones with modest fuel consumption), can sail surprising distances.
300km isn't a record, as Table 8.8 shows. Verifiable distances for different groups of
landlubbing tetrapods (winged cheats omitted) are approximately: lizards -well over
1,500km; terrestrial tortoises -nearly 1,000km; rodents -about 900km; small meat-eating
mammals -about 300km; large mammals -not very far.
This helps explain why many isolated Pacific islands have populations of endemic rats,
while elephants are scarce. Waif dispersal is viable for small mammals, and could account
for the arrival of some marsupials in South America.
Back to the Mesozoic and Case et al, 2004, (p.245)
However, waif dispersal isn't the only possibility in this case. It wouldn't be plausible
for the interchange of large dinosaurs during the Upper Cretaceous. Hadrosaurs headed
south, and late sauropods exchanged pleasantries with them while heading in the opposite
direction. There must've been a landbridge, and the Caribbean seems likely for the
Campanian-Maastrichtian. Several possibilities have been proposed. Of particular promise
is one involving Cuba and the Aves Ridge, (p.246).
Holotype
The holotypes, YPM 14912, is an upper molar residing at Yale. The specific name refers to
its assumed primary (or at least very basal stem) position in
"polydolopimorphian" evolution. |
| Reference: | Case, Goin & Woodburne (2004), "South American"
marsupials from the Late Cretaceous of North America and the origin of marsupial cohorts,
Journal of Mammalian Evolution, 11(3/4), p.223-255. |
| Other reports:
Xxxxxxxxxxxxxxxxxxxx
Xxxxxxxxxxxxxxxxxx |
A. "Polydolopimorphia" B.
Ameridelphia
| Taxon: Ameridelphia Szalay, 1982
This cohort includes all living American marsupials.
While the history of the group has been predominantly South American, its roots first grew
in the northern Cretaceous. Presently, the only certainly Mesozoic
ameridelphian described is Nortedelphys, and
most other genera have no business being listed here. The entries were more or less been
compiled by accident and may as well stay. At least it will keep the other directories
tidier.
Genera:
Chulpasia, Esteslestes,
Jaskhadelphys,
Maastrichtidelphys, Monodelphis,
Necrolestes, Nortedelphys,
Progarzonia, other reports
Time-Line:
Recent: Monodelphys
Miocene: Necrolestes
Eocene: Esteslestes, Progarzonia
Paleocene: Chulpasia, Jaskhadelphys
Upper Cretaceous: Maastrichtidelphys, Nortedelphys, Europe |
| Genus:
Maastrichtidelphys Martin JE, Case JA, Jagt WM, Schulp AS & Mulder WA, 2005
'Maastricht womb'
Remarks: My information is presently limited to the contents of a news report, some notes
written by David Marjanovic and a mention of what is presumably the same fossil in Case et
al 2004, p.251.
The description has now arrived (many thanks), and a fuller entry will appear at
some time. |
| Species: | Maastrichtidelphys meurismeti Martin JE, Case JA,
Jagt WM, Schulp AS & Mulder EWA, 2005 |
| Place: | Maastricht |
| Country: | the Netherlands |
| Age: | Maastrichtian, Upper Cretaceous |
| Remarks: | This species is based on an upper
molar, which was found by amateur fossilers in 2002. A
professional paleontologist, James Martin, happened to be studying aquatic critters in the
Naturhistorisch Museum in Maastricht at the time, and he identified it as being from a
marsup. Colleague Judd Case agreed. Assuming this is the same fossil mentioned by Case et
al in 2004, they referred to it as from a didelphoid marsupial.
Marsupial?
Whether it's truly a marsup largely depends upon definitions. The concept of Marsupialia
followed by the authors is rather wide; all North American
metatherians appear to be included. This isn't in line with the views of other
authorities. David Marjanovic reports they assign the fossil to Herpetotheriidae and state
the group is: "seemingly related to the North American opossum". Of the other
genera used in their comparisons, Maastrichtidelphys was found to be closest to
Nortedelphys from the Upper Cretaceous of North Ameirca.
Season's greetings
The species' name honours the two discoverers, Roland Meuris and Frans Smet. They were
reportedly looking for shark teeth, but Smet noticed one two millimetre long fossil looked
decidedly mammalian. To the best of my knowledge, the dynamic duo have come up with the
oldest mammal remains ever found in the Netherlands, so I sincerely wish them
congratulations and a Happy New Year. (This initial entry happens to have been written on
31.12.2005.)
The specific name
I had been informed that the ending of the species' name should have been
meurismetorum, as it's in honour of two people. However, one of the original
authors, Dr Mulder, has informed me the published name is linguistically correct (pers. comm.
27.7.2006). Reportedly, as can be read in full on our site
guestbook: "Only when the names of the honoured persons are the same, an
ending of a species name should be "-orum"."
I disagree
With all due respect to the authors, I don't see how that can be the case.
Nevertheless, I'm pleased the matter was raised as it helped me look into things
more fully, and also prompted me to realise I had Dr Mulder's name incomplete in
the citation. (I'd neglected the initial initial; ie. 'E'.)
I've since sought further advice from a number of people and have consulted the
ICZN code on zoological nomenclature - available at:
http://www.iczn.org/iczn/index.jsp.
While it's possible I've overlooked something, my present opinion remains
essentially unchanged. The specific name of M. meurismeti should be
emended.
The relevant rules concerning specific names are, as far as I'm aware, contained in
Chapter 7, Formation and treatment of names, Article 31. 31.1.1 states the
requirement for observing Latin grammar. 31.1.2 stipulates the use of /-orum/ for
names honouring more than one man. I found no indication that this only applies in
cases of a common surname.
Precedent and parallels
Naming a species after two people with different surnames doesn't seem to be very
common, but it's certainly happened before. One instance is provided by the
dinosaur Utahraptor ostrommaysorum. Significantly, I'm advised that this
species was published as U. ostrommaysi but, as it honours two men, an
emendation was felt to be necessary. Utah seems to enjoy this kind of thing, as it
also boasts of Cedarpelta bilbeyhallorum (This actually honours a wife and
husband, but Latin grammar takes a masculine approach in such instances.)
There are also several Chinese dinosaur species named in honour of two countries.
In these particular cases, the grammatical rule is the same as for men:
Omnivoropteryx sinousaorum and Mamenchisaurus sinocanadorum.
Getting things wrong can be a by-product of being busy, and I've certainly made
more than my fair share of mysteaks. In this instance, however, I don't think the
error is mine. While presently valid, the specific name of Maastrichtidelphys
meurismeti isn't correct. However, I'm not a linguist. And it's important to
note that Dr Mulder remains of the opinion it is correct (pers. comm. 4.8.2006).
Perhaps there is a schism in the Latin Empire of the 21st century. In any case,
the name is scientifically valid.
Some discussion concerning this theme was conducted on the Dinosaur Mailing List
forum, and the appropriate thread will reveal various sources. A collective thanks
is due:
http://dml.cmnh.org/2006Jul/msg00393.html. |
| Reference: | Martin JE, Case JA, Jagt WM, Schulp AS & Mulder EWA (2005),
A new European marsupial indicates a Late Cretaceous high-latitude Transatlantic
dispersal route, Journal of Mammalian Evolution, 12(3/4), p.495-511. |
| Genus: Nortedelphys
Case JA, Goin FJ & Woodburne MO, 2004
'Northern womb'
Aka: Alphadon (partly)
Family: Herpetotheriidae
Remarks: The following is based upon my reading of Case, Goin & Woodburne, 2004.
This genus is assigned to the Ameridelphia. Previously, it was thought that
ameridelphians first evolved in South America from alphadelphian immigrants, (or their
descendants). However, the presence of a genus in the Upper Cretaceous of North America
suggests they were invented in the USA, (p.226).
The upper molars have a wide stylar shelf and long
trigons. The extoflexus
is moderate. Stylar cusp B is large, (p.234).
'Norte' is Castilianian. |
| Species: | Nortedelphys magnus Case JA, Goin FJ & Woodburne MO, 2004 |
| Aka: | Alphadon marshi (partly) |
| Place: | Paskapoo Formation, Alberta & Wyoming |
| Country: | Canada & USA |
| Age: | upper Maastrichtian, Upper Cretaceous |
| Remarks: | This is the largest of the three species and the
holospecies for the genus. It's known from fragments of the left jaws. The
maxilla contains the molars
M1-M4. The lower mandible houses p3-m4. The lengths of
the upper molars range from 1.75mm (M4) to 2.85 (M2). For the lowers this is 2.3mm (m1) to
2.75mm (m3). The p3 manages 1.8. Compared to the other species, the protocone of a tooth
is wider and not as spire-like. There's a larger entoconid on the
talonid and a variety of other distinctions among the
dentition. To defend the honour of the relatively short fourth upper molar, it was in
the early stages of eruption, (p.236).
Affinities
Nortedelphys is a didelphimorphian rather than a peradectian, (eg
Peradectes). On the upper molars, (p.243),
the centrocrista is V-shaped, which produces a pyramidal paracone and metacone. These
cusps are more rounded in peradectians.
The lower molars have informative characteristics on the
talonids. Among these are the ways in which the entoconid and hypoconulid are twinned.
For Nortedelphys, the hypoconulid is on the corner of the talonid, while the entoconid
is further forward on the lingual side, and the latter is
much larger. In peradectians, the hypoconulid is offset from the corner, and diagonally
twinned with a similarly sized entoconid. The molars in both cases are of about the same
size and share common characteristics, but they do have their distinctions.
The width of the molars, the relatively equal sizes of paracone and metacone, and the deeper
ectoflexus, (p.244), help suggest this genus is less
specialised than later herpetotheriids. They also differ from pucadelphids. The
V-shaped centrocrista of the uppers habitually invades the wide stylar shelf, and nears
stylar cusp C, (as in other herpetotheriids).
As Nortedelphys is the oldest known didelphimorphian, its
plesiomorphic characteristics are forgivable.
Family
This genus is assigned to the family of Herpetotheriidae. If all interpretations are correct,
the herpetheriids were a long-lived and cosmopolitan family, known from North and South
America, Europe, Africa and perhaps Asia. They seem to have survived until the Oligocene.
Holotype
The holotype, UA 2846, consists of partial upper and lower jaws, which were found in
occlusion. The species name refers to its larger size. |
| Reference: | Case, Goin & Woodburne (2004), "South American"
marsupials from the Late Cretaceous of North America and the origin of marsupial cohorts,
Journal of Mammalian Evolution, 11(3/4), p.223-255. |
| Species: | Nortedelphys intermedius Case JA, Goin FJ & Woodburne MO, 2004 |
| Place: | Hell Creek Formation, Montan, Wyoming & South Dakota |
| Country: | USA, Canada |
| Age: | Maastrichtian, Upper Cretaceous |
| Remarks: | The species is based on fifteen isolated
molars. Uppers: LM1-3; RM1-3. Lowers: Lm1-3; Rm3. The
length range for the whole basketful is 1.82mm (LM1) - 2.54(Lm2). The holotype is a left
M3. It's got a moderate ectoflexus and five stylar
cusps, of which B is the largest. The stylar shelf is wide, (p.239). The paracone and
metacone are the same height, but the latter is more invasive, (p.240). The protocone is
low.
Holotype
UCMP 134776 is an upper molar, and it studies at Berkeley University in California. The
specific name refers to its middling size. |
| Reference: | Case, Goin & Woodburne (2004), "South American"
marsupials from the Late Cretaceous of North America and the origin of marsupial cohorts,
Journal of Mammalian Evolution, 11(3/4), p.223-255. |
| Species: | Nortedelphys minimus Case JA, Goin FJ & Woodburne MO, 2004 |
| Place: | Hell Creek Formation, Montana and Wyoming |
| Country: | USA |
| Age: | Maastrichtian, Upper Cretaceous |
| Remarks: | Three upper molars
were assigned to this species; LM3, RM2 and RM1. The lengths range from 1.49mm (M1) to
1.89 (M2). The M3 is wider than long, (p.242), which is usual enough for this position.
There's a deep ectoflexus. Four stylar cusps are
present and B is the largest. As with N. intermedius: wide stylar shelf; similar
heights for the protocone and metacone, with the latter being more massive.
Holotype
The holotype, UCMP 72211, is another student of Berkeley University, California, and also
a left M3. I'll leave you to work out the significance of the specific name. Clue: this
is neither the largest nor middlest species. |
| Reference: | Case, Goin & Woodburne (2004), "South American"
marsupials from the Late Cretaceous of North America and the origin of marsupial cohorts,
Journal of Mammalian Evolution, 11(3/4), p.223-255. |
| Other reports:
Europe
In 2003, a didelphoid marsupial was reported from the Masstrichtian of Europe, (Case et al
2004, p.251). Didelphoidea is a superfamily within Ameriadelphia. I'm not yet certain,
but I strongly suspect this is the same fossil as
Maastrichtidelphys. |
| You are about to leave the Mesozoic. The hodge-podge of
following ameriadelphians have no certain Cretaceous fossil record. Chulpasia and
Peradectes might perhaps predate the Paleocene according so some sources. |
| Genus:
Chulpasia Crotchet JY & Sigé B, 1993
'from Chulpas' |
| Species: | Chulpasia mattaueri Crotchet JY & Sigé B, 1993
|
| Place: | Chulpas |
| Country: | Peru |
| Age: | Paleocene (or perhaps Upper Cretaceous) |
| Remarks: | Teeth of this genus have
also been identified at Tingamarra, Australia, (Lower Eocene).
The age of the Chulpas fossils is presently not certain. They're near the K-T border,
though the overall content of the fauna is more suggestive of Paleocene, (de Muzion &
Cifelli 2001, p.95). The genus has similarities with
Glasbius It could be a Polydolopimorphan. If this is
borne out, then it would belong in the first section of this directory.
The fauna contains up to eight marsupials. Sillustania quechuense Crochet & Sigé,
1996 has also been named, and assigned to Sillustaniidae, Polydolopoidea. |
| Reference: | Crotchet & Sigé (1993), Les mammifères de Chulpas
(Formation Umayo, transition Crétacé-Tertiare, Pérou. Données préliminaires Documents du
Laboratoire de Géologie de Lyon, 125, p.97-107. |
| Genus:
Esteslestes Novacek MJ, Ferrusquia-Villafranca, Flynn J, Wyss & Norell, 1991
Aka: Estelestes |
| Species: | Esteslestes ensis Novacek, Ferrusquia-Villafranca I, Flynn J, Wyss AR & Norell MA, 1991 |
| Place: | de Punta Prieta, Baja California Norte |
| Country: | Mexico |
| Age: | Lower Eocene |
| Remarks: | I did find this text: "Abstract for Bulletin
208 Fossil mammal and other vertebrate remains from the
Lomas Las Tetas de Cabra in Baja California Norte, Mexico, provide an opportunity to
examine the utility of continental scale geochronologies based on land mammal faunas…" |
| Reference: | Novacek et al (1991), Wasatchian (Early Eocene) mammals and
other vertebrates from Baja California, Mexico: The Lomas las Tetas de Cabra fauna.
Bulletin AMNH 208. |
| Genus: Jaskhadelphys
Marshall LG & de Muizon C, 1988
Aka: Jaskadelphys |
| Species: | Jaskhadelphys minutus Marshall LG & de Muizon C, 1988 |
| Place: | Itaborai |
| Country: | Brazil |
| Age: | Paleocene |
| Remarks: | Martin Jehle has this listed as a member of
"Jaskhadelphydae (valid?)", within the order of Didelphimorphia. The author of
the family is de Muizon, 1991.
The genus has also been identified in the somewhat older Tiupampa fauna of Bolivia. I don't
know whether these remains were assigned to a particular species, (mentioned in de Muizon
& Ciffeli 2001, p.87). The best information I have on size is that the critter was
'small', (p.88). |
| Reference: | Marshall & de Muizon (1988), The dawn of the age of
mammals in South America, National Geographic Research, 4, p.23-55. |
| Genus:
Monodelphis Burnett, 1830
Aka: Hemiurus Gervais, 1855; Microdelphys Burmeister, 1856;
Minuania Cabrera, 1919; Monodelphiops Matschie, 1916; Minuania
Cabrera, 1919; Peramys Lesson, 1842
Age: Still clambering.
Remarks: Monodelphis doesn't belong on this page. It's the short tailed opossum of
South America and a member of Didelphidae Gray, 1821. Whilst some people accuse it of
being old fashioned, it's certainly not Mesozoic. ("According to Carroll (1988), it's
been around since Early Miocene, ca. 25 Ma ago." With thanks to Mikko Haaramo.)
Seeing as it looks so cute though, we might as well have a couple of photos. |
| Links:
"Photos of some of my favorites"
http://www.rufnermountainphotos.homestead.com/Photo4.html
And very nice they are too. Scroll down past the two toads and the axolotl. Next comes
Chiquitta, a Brazilian Rain Forest Possum. "…And will readily breed with the right
conditions" applies to many of us.
Possum Page
http://www.duke.edu/~kksmith/possum.html
Professor Kathleen K Smith has a breeding colony of grey short-tailed opossums. Photo 1,
the cage. Photo 2, the possum. Photos 3 to 6… The poor mother! |
| Genus: Necrolestes
Ameghino F, 1891
'grave robber'
Family: Necrolestidae (Ameghino, 1891) |
| Species: | Necrolestes patagonensis Ameghino F, 1891 |
| Place: | Patagonia |
| Country: | Argentina |
| Age: | lower Miocene (Santacrucian) |
| Remarks: |
According to John H Burkitt: "A peculiar animal which was developed from the primitive
opossum stock. It is a small form, so similar to the placental insectivores that it was
long mistaken for a member of that group." Necrolestes was a marsupial
mole-like critter. According to Cox et al (1999), the fossil was the end of the snout.
The rest of this information comes from Simpson, 1980, p.77-78.
This was a highly specialized and utterly peculiar animal which is placed alone in its own
family, and lived about 17 million years ago. It's also said to have been first published
in 1894, but Simpson blames Florentino Ameghino in 1891. Ameghino had some unusual opinions
concerning the affinities of South American fossil mammals, but there wasn't that much to
compare them with at the time. He believed this genus represented an insectivore derived
from marsupial ancestors, and accused it of giving rise to all insectivores. The marsup
part of the story was correct.
Further skulls, jaws and pieces of skeleton were collected by Hatcher, and were then
described by Scott in 1905. He (erroneously) cancelled marsupial affinities and sought to
ally the animal with the golden moles of South Africa. There are similarities, but these
appear to be the results of similar lifestyles. In 1958, Patterson re-examined some
specimens in Princeton using instruments which hadn't previously been available.
Necrolestes resumed being seen as a marsupial, and very tentative connections with
borhyaenids were mooted. However, this wasn't based on anything substantial.
The creature had a skull of around 3.5cm in length, a naturally up-turned nose and lots of
incisors, (five per side up and four down). The
canines were sharp and the
molars had triangular crowns. The front legs indicate a mole-like burrower. |
| Reference: | |
| Genus:
Progarzonia Ameghino, 1904 |
| Species: | Progarzonia sp. Ameghino, 1904 |
| Place: | Casa Mayor Fossil Beds |
| Country: | Argentina |
| Age: | Lower Eocene |
| Remarks: | John H Burkitt suggests the family Caenolestidae,
a group of South American rat opossums. |
| Reference: | |
| 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.
back to top
Trevor Dykes, November 2004. Latest update: 4.11.2008
Ktdykes@arcor.de |
| With further thanks due to:
Weight estimates
Dr John Alroy, North American Fossil Mammal Systematics Database
http://www.nceas.ucsb.edu/~alroy/nafmsd.html
The source of much of the above information, including weight estimates.
Weight estimates have generally, when not otherwise stated, been
shamelessly stolen from John Alroy's internet site. When other sources are available, this
may produce disparities. I've got two comments to offer.
Firstly, if you were to claim that some European hedgehogs (Erinaceus europaeus)
weigh 400 grammes, you'd be correct. If I were to add that some reach 1,2 kilos, I'd also
be correct. Some hedgehogs are bigger than others.
Secondly, the estimates partly depend upon the questions posed. If a calculation is based
upon an insectivore model, the answer may be 50g. Choose a South American opossum, and it'd
perhaps be closer to 150. Think primate, and 300g might result.
A further source is Gordon, 2003 (p.45-46). Cynthia Gordon's research offers various
alternatives. These depend upon which tooth is used, (lower molar 1 or Upper Molar 1),
and which group of animals it's compared to. As they were New World marsupials, I'll
include the range of estimates based upon Didelphidae. These calculations were derived
from a. m1 Length, b. m1 L x Width, c. M1 L and d. M1 L x W.
A third source is Gordon & Cifelli, 2003 (p.93-97). The methods are as for Gordon,
2003.
A rough system of measurement is employed in these directories. A standard mouse = 25g, a
rat counts as 400 whilst a beaver equals about 25 kilos.
The Peabody On-line VP Catalogue
http://george.peabody.yale.edu/vp/
If this resumes functioning, could somebody please look up YPM 14912, and 14911? Those are
the basis of Hatcheritherium. I want to be sure when they were collected. It refused
to cooperate this morning!
The thrilling animated graphics are courtesy of
HitBox Central,
Animation Library and
best animations.com. |
Bibliography:
Beck RMB, Archer M, Godthelp H, Mackness BS, Hand SJ & Muirhead J (2008), A
bizarre new family of Marsupialia (incertae sedis) from the Early Pliocene of
northeastern Australia: Implications for the phylogeny of bunodont marsupials, Journal of
Paleontology, 82(4), p.749-762.
Case JA, Goin FJ & Woodburne MO (2004), "South American" marsupials
from the Late Cretaceous of North America and the origin of marsupial cohorts, Journal of
Mammalian Evolution, 11(3/4), p.223-255.
Cifelli RL & Muizon de C (1998), Marsupial mammal from the Upper Cretaceous
North Horn Formation, central Utah. Journal of Paleontology, 72 (3), p.532-537.
Davis BM (2007), A revision of "pediomyid" marsupials from the Late Cretaceous
of North America, Acta Palaeontologica Polonica, 52(2), p.217-256.
Gordon CL (2003), A first look at estimating body size in dentally conservative
marsupials, p.4-55 (In) Functional Morphology and Diet of Late Cretaceous Mammals of North
America, Ph.D. Dissertation, University of Oklahoma, p.i-xiv and 1-177.
Kemp TS (2005), The Origin and Evolution of Mammals, Oxford University Press,
pp.331.
Lavers C (2003), Warum haben Elefanten so große Ohren?, Bastei Lübbe Verlag
Taschenbücher, 2. Auflage. (The English original was 2000).
McKenna MC & Bell SK (1997), Classification of Mammals Above the Species Level.
Columbia University Press.
Muizon de C & Cifelli RL (2001), A new basal "didelphoid" (Marsupialia,
Mammalia) from the Early Paleocene of Tiupampa (Bolivia), Journal of Vertebrate Paleontology,
21 (1), p.87-97.
Simpson GG (1980), Splendid Isolation, The Curious History of South American Mammals,
Yale University Press, pp266.
Spinar VS & Currie PJ (2000), The Great Dinosaurs (English translation from the
Czech original of 1994), Caxton Publishing Group. ISBN 1-84067-276-5. |
