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Re: On diagnosing _Tyrannosaurus_



George Olshevsky wrote-

> I didn't say Tyrannosaurus doesn't have a diagnosis; only that it doesn't
yet
> have a reasonably current >published< one. Nobody seems to have collected
> together the diagnostic features of Tyrannosaurus in one place in print,
> where they can be referred to.

Molnar (1991) listed fifteen characters unique to Tyrannosaurus rex within
tyrannosaurids.
- orbital process of postorbital extending anteroventrally into orbit
- narrow key-hole shaped orbit
- deeper antorbital fossa
- absence of pterygopalatine fenestra
- deep, untapered anterior lacrimal process with a reduced foramen and no
well-developed horn core
- constriction of nasals between upper rami of lacrimals
- well-developed postorbital rugosity
- cranial nerve IV foramen posterolateral to III
- basicranial frontanelle absent
- orbit further forward
- maxillary tooth row shorter
- anterior maxillary teeth longer
- supratemporal recess longer anteroposteriorly
- parietals longer anteroposteriorly, frontals shorter
- quadrate condyles larger
However, this was before Nanotyrannus and Dinotyrannus were synonymized with
T. rex, so some of these characters may no longer be applicable.

Mickey Mortimer