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Re: Theropod "migrations"



In a message dated 4/24/99 4:02:27 AM EST, gl91bciiLt@earthlink.net writes:

<< And now there's a Cretaceous Chinese stegosaur? >>

There has been an Early Cretaceous Chinese stegosaurian since 1973; and there 
also has been a Wealden (British Early Cretaceous) stegosaurian since 1912 
(Craterosaurus pottonensis, described by Seeley as dinosaurian in 1874 but 
not identified as stegosaurian until Nopcsa's 1912 paper). The historically 
first stegosaurian to be described is Regnosaurus northamptoni, by Mantell in 
1848, and it is also from the Wealden and likely a senior synonym of 
Craterosaurus pottonensis. I identified it as a stegosaur in 1993 (from 
photos, figures, and descriptions of the type specimen), and this 
identification was seconded by Barrett & Upchurch in 1995, who had the 
benefit of examining the specimen at first hand. See my Dinosaur Folios #1 
for the full story.

The Chinese Early Cretaceous stegosaur genus, Wuerhosaurus, now has two 
species (W. homheni and W. ordosensis), which together are perhaps the most 
derived of all stegosaurians. On the other hand, Regnosaurus = Craterosaurus 
seems to be among the most primitive (=least derived) stegosaurians, 
apparently some kind of relic (B&U even argued that it was a huayangosaurid) 
of a minor dacentrurid radiation of British stegosaurians.

All the Early Cretaceous stegosaurians were fairly large beasts, although not 
enough is known of Regnosaurus to make a reliable size estimate. The biggest 
problem with the Indian Dravidosaurus was making the figures in the paper fit 
the remains in the photographs, and many subsequent papers on stegosaurians 
used the figures without questioning them. The taxon was finally removed from 
Stegosauria by Chatterjee and Rudra in a recent paper on the K-T extinction. 
A lot of material in Indian vert paleo papers may be misidentified (e.g., 
Bruhathkayosaurus, Dandakosaurus, Kotasaurus), says Chatterjee (pers. comm.), 
because the people doing the identifications are not experienced career 
paleontologists.