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Zupaysaurus and Atlasaurus skull



From: Ben Creisler bh480@scn.org
Subject: Zupaysaurus and Atlasaurus skull

To reply to a query a few days back, here is additional 
info about Zupaysaurus and Atlasaurus. Sorry I don't have 
more details yet on either of these interesting critters.
Zupaysaurus
found in Talampaya National Park in La Rioja Province in 
the Andes, red beds; known remains include a partial 
vertebra, pelvic bones, shoulder bones, and a complete 
skull, "beautifully preserved". About 2.1 m.  (7 feet) 
tall with a skull 50 cm. (20 in.) long. Teeth are serrated 
and pointed. Late Triassic--TV announcer said "about 200 
million years ago," not a very accurate figure since this 
would make it Early Jurassic by my reckoning. Can't 
provide a picture but some nice photos of Talampaya 
National Park can be seen at 
http://www.geocities.com/Yosemite/Geyser/6072/Pp-
Talampaya.html

Atlasaurus skull
I quote here all the descriptions of the skull provided:
Autapomorphies include: supratemporal fenestra twice as 
wide as long (140 by 70 mm) not visible in lateral 
perspective; combined with paroccipital processes 48% of 
estimated length of mandible; paroccipital processes 
extend horizontally at nearly right angles to long axis of 
skull; mandibular symphysis and dentary very shallow 
(symphyseal depth 116% minimum depth of dentary, probably 
reversal from primitive sate in sauropods)...In other 
known sauropods the supratemporal fenestra is more dilated 
anteroposteriorly, and the dorsal margins of the fenestra 
slop laterally  so that it is visible in lateral 
perspective; the paroccipital process is markedly inclined 
ventrodistally, posteroventrally or both; the combined 
width of the processes is less than 48% of the length of 
the mandible; the ratio between the symphyseal depth and 
the minimum depth of the dentary is at least 150%...
 In the skull [of Atlasaurus], the postorbital process is 
broader transversely than anteroposteriorly, and the 
quadratic fossa is much shallower than in Camarasaurus 
(Wilson and Sereno 1998, characters 75.90). The 
basipterygoid processes are longer than in Brachiosaurus 
and Camarasaurus. The anterior end of the dentary is 
straight, not curved toward the symphysis. As preserved, 
the dental formula is pmx?, mx. 14-15? dent. at least 14; 
some teeth bear marginal tooth denticles.....
The relationships of Altasaurus appear to be within 
camarasauromorph sauropods, including Brachiosaurus and 
Camarasaurus, as indicated by a quadratojugal the major 
rami of which embrace an angle of 90 degrees or less....
(Photos show the braincase, left maxilla, and left 
dentary, but no reconstruction of the entire skull is 
provided.)