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Obdurodon (was Re: Coronosaurus, new ceratopsid genus for Centrosaurus brinkmani)



David Marjanovic <david.marjanovic@gmx.at> wrote:


>> _Monotrematum_ is now often  considered a junior synonym of
>> _Obdurodon_.
>
> Really? *M.* is two isolated teeth from the Paleocene of South America; *O.*
> is good material (at least one skull, IIRC) from the Miocene of Australia.


_Obdurodon_ was originally described from two isolated teeth, named
_O. insignis_.  The superb skull is from the referred species, _O.
dicksoni_.  Both _Obdurodon_ species are from Australia.  The teeth
from Patagonia named _Monotrematum sudamericum_ are very similar to
those of _Obdurodon_, although substantially larger.  Hence the
proposed synonymy.  However...


Another hypothesis is that _Obdurodon_ is referrable to the
Ornithorhynchidae (the platypus family), but that _Monotrematum_ is a
stem-monotreme.  This is the hypothesis advanced by Phillips et al.
(2009; doi: 10.1073/pnas.0904649106 ).  This still means that the
terrestrial, ant-eating echidnas likely evolved from amphibious
ancestors, given how similar the teeth and femora of _Monotrematum_
are to ornithorhynchids.  So the platypus-like characters of
_Monotrematum_ would be primitive for the crown Monotremata; but
_Monotrematum_ would *not* be referrable to _Obdurodon_.





Cheers

Tim






Cheers

Tim