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Re: _Nanosaurus_ extract



Regarding George O.'s piece on _Nanosaurus_

        While I can't add anything of much use to the dino side of things,
as a dead croc person (I'm proud to admit that sort of thing even on a
dino list!) here's some additional info on _Hallops (Nanosaurus) victor_
that you might find useful/interesting/(boring?):
        In addition to the work conducted by Marsh - who as
George pointed out, originally considered _Hallops_ an
ornithischian, then later as a theropod - Von Huene and Lull
(1908) suggested that it was a *thecodont*.  As was usually the
case, this was more of a garbage can assignment more than
anything else, however, _Hallops_ does posses a number of
features shared with some members of this *grade*, in
particular a rotary crurotarsal (or *crocodile normal*) ankle
joint with a greatly elongated calcaneal tuber.  Possession of
this type of ankle morphology precludes consideration of
_Hallops_ as an ornithodiran, all of which possess an
*advanced mesotarsal* condition.  Importantly however, the
open acetabulum evident in the ilium of _Hallops_ in addition
to a number of characters relating to the carpals, sacrum, and
metatarsals, clearly ally it with Crocodylomorpha.  As things
currently stand, _Hallops_ with its long, gracile limbs, probably
represents some kind of sphenosuchian or protosuchid
crocodylomorph.  However, without additional cranial material
precise assignment to either group remains problematic.
        A second controversy surrounding _Hallops_ relates to
its stratigraphic provenance and age.  The specimen was found
in an allochthonous float block and displays preservation
characteristics atypical for the Morrison Formation from which
Marsh originally thought it to be derived.  Based on
sedimentological evidence it now seems likely that the source of
the _Hallops_ slab is the Ralston Creek Formation which
occurs below the Morrison Formation and is Middle Jurassic
(Callovian) in age.

Cheers,

Steve Salisbury
School of Biological Sciences
University of NSW, Australia
P2158753@vmsuser.acsu.unsw.EDU.AU