Re: Dilophosaurus? sinensis skull photo

["Mickey Mortimer" <mickey_mortimer@email.msn.com>]

Nick Pharris wrote-

>What this thing bears an uncanny resemblance to, in my mind, is
>_Monolophosaurus jiangi_ (see _Canadian Journal of Earth Sciences_ , vol.
>30 [1993], p. 2029).  The way the crest begins just in front of the eyes,
for
>one thing, is more like _Mono_ than _Dilo_.  The lacrimal looks VERY like
>that of _Cryolophosaurus_, and the quadrate/quadratojugal/jugal area looks
>much like _Sinraptor_.  I wouldn't be surprised if _"D". sinensis_ turned
out
>to be a primitive tetanuran or basal carnosaur.

Jaime Headden wrote-


>I agree with Nick. Another few points, is that the antorbital fenestra is
rectangular and continues, at least anteriorly, above the maxilla and nasal,
on the lateral surface of the crest, as in *Mono.* and also, perhaps, in
*Proceratosaurus* Woodward. Unlike coelophysoids, the antorbital tooth row,
as Smith pointed out yesterday, does not continue ventral to the orbit;
there's a very extensive lachrymal flange that appears to exclude the jugal
from the antorbital fenestra, and the lachrymal itself resembles that of
*Mono.* and *Cryo.* more than anything else.

Although I haven't yet delved into the depths of basal tetanurine/ceratosaur
phylogeny, these are the differences I see between Dilophosaurus wetherilli
and D? sinensis.  Dilophosaurus wetherilli has-
- premaxilla thin below naris
- main body with teeth located anterior to naris
- maxillary teeth much longer
- subnarial notch much more apparent
- nasomaxillary crest taller
- lacrimal process extends into orbit
- nasomaxillary crest extends posteriorly past orbit
- external mandibular fenestra more reduced
- jugal thicker beneath orbit
- antorbital fenestra differently shaped
- external naris taller
- postorbital extends ventrally to lower rim of orbit

The first eight differences are autapomorphies of D. wetherilli, so don't
mean anything when considering phylogenetic relationships.  The others are
simply variations of shape, also useless phylogenetically.  Although I agree
"D" sinensis certainly isn't Dilophosaurus, I don't know of any
synapomorphies it shares with other genera.

differences from Monolophosaurus jiangi:
- nasal crest extends to premaxilla
- nasal crest fenestrated
- distinctive tall, blunt lacrimal horn/process
- squamosal extends into infratemporal fenestra
- maxillary fenestra larger
- antorbital fenestra smaller and differently shaped
- jugal thicker below orbit
- postorbital extends ventrally to lower rim of orbit
- external naris taller

Again, the differences are either autapomorphies or variations of shape.

One thing that would be good to know is if the crest of "D" sinensis is
formed of the nasal and lacrimal, like D. wetherilli, or the premaxilla and
nasal, like M. jiangi?  Is "D" sinensis's crest double or single?  Only when
we know the answer to these questions can we consider the phylogenetic
significance of the crests in these genera.

I also agree that the lacrimal of "D" sinensis and C. ellioti are similar,
but the similarity ends there.  The crests are completely different, the
jugal and quadratojugal of C. ellioti are thicker, C. ellioti's skull is
higher and the odd infratemporal configuration of C. ellioti is absent.

In response to Jaime, the tooth row of D. wetherilli also appears to end
antorbitally and I wouldn't discount jugal-aof contact in "D" sinensis.  If
Rauhut, Currie and others are right, the Ceratosauria isn't even
monophyletic and Rauhut, at least, believes Dilophosaurus isn't a
coelophysoid.  We need a stable phylogeny for these animals before we can
hypothesize on their relationships.

Mickey Mortimer