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Re: No Cretaceous placental mammals?
<<No, I meant the third Early Cretaceous trity, after *Xenocretosuchus* and
the over 100 unnamed teeth from Japan.>>
Whoops, my keyboard made a stupid mistake. The Antarctican is Lower
Jurassic. What a stupid machine.
I seem to remember there's meant to be at least one more West Siberian trity
from the Kemerovo Region, and know for sure /Xenocretosuchus/ has been
picked up from north from the Shestakovo localities at Bol'schoi 3 Kemchug.
It's another exposure of the same Ilek Formation, and can only be reached by
canoe. It's in the middle of taiga forest. It's Bol'shoi 3 Kemchung
friends include an amphilestid named /Kemchugia/, two unnamed species of the
increasingly promiscuous /Gobiconodon/ plague and a bit of something. Other
than for the late trity, the local eucynodonts are fanatically triconodont
so far. However, sampling there is limited by canoe size. Presently, for
example, there's no chance of taking lots of sediment away for later
I recently read a Japanese paper: Matsuoka et al, 2002, A clue to the
Neocomian vertebrate fauna: initial results fromt the Kuwajima "Kaseki-kabe"
(Tetori Group) in Shiramine, Ishikawa, central Japan, Memoirs of the Faculty
of Science, Kyoto University, Series of Geology and Mineralogy, 59(1),
p.33-45. That provided further info on their trity, some pretty good
looking triconodont jaws and a multituberculate. For some reason, they seem
to publish bits of information spread across several journals.
Anyway, they've switched to using the plural. The trity teeth tally's got
to 150, and most belong to a 'large' type. (Sizes, if available, have
perhaps been published in yet another study.) These feature a relatively
low number of cusps in the usual three rows for the upper postcanine: 2:2:2.
Then there are some middling sized specimens, but the morphology's similar.
Both types are at least generically the same.
Then they've got a couple of small specimens of lower postcanines. These
are said to be comparatively small for tritys. (The smallest tritys so far
have juvenile skull lengths of around 4cm (/Lufengia/) and 5cm
(/Bocatherium/).) There's little description of these lower postcanines in
this particular study, but the authors state they are clearly
morphologically different to other lowers in the sample, and not simply due
to size. Presumably, that'll be a distinct genus at some stage.