Garth’s posterous

Bent in a kinda straight way 
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June 18, 2009

Limusaurus – an herbivorous ceratosaur?

Limu spec
 
limu skel
 
This is a bit different! I hadn't picked up on this in the previous piece I posted. I'd just assumed it was another coelurosaur.
 
As Archosaur Musings notes, while not unsurprising that a number of theropods became herbivores, it is surprising "...that Limusaurus is a ceratosaur and thus part of a clade which would normally not be associated with this kind of lifestyle at all – at least the others are consistent. Ceratosaurs such as the eponymous Ceratosaurus, bizarre Carnotaurus and Abelisaurus while obviously having their differences do have one thing in common, namely being tanking great animal with shredding carnivorous teeth. Because, well, they killed and ate their dinner and it had a tendency towards a) being alive, and thus unlike plants, b) could run away."
 
Also interesting that this critter apparently dates from the middle Jurassic and thus, given that it already shows a number of seeming adaptations to herbivory, must have had a number of herbivorous and omnivorous antecedents. This pushes herbivory much further back in time for Theropoda, and I suppose phylogenetically as well.
 
That "...a basal member of a basal clade of theropods adopted herbivory far earlier than we thought."
 
Much more at the Archosaur Musings link.
 

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Filed under  //   ceratosurs   dinosaurs   evolution   finger homology   herbivory   Limusaurus inextricabilis   theropods  

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June 18, 2009

Beaked, Bird-like Dinosaur Tells Story of Finger Evolution

This image shows a reconstruction of Limusaurus with no evidence of feather structures.
This image shows a reconstruction of Limusaurus
 
Introducing Limusaurus inextricabilis ("mire lizard who could not escape").
 
June 17, 2009
Scientists have discovered a unique beaked, plant-eating dinosaur in China. The finding, they say, demonstrates that theropod, or bird-footed, dinosaurs were more ecologically diverse in the Jurassic period than previously thought, and offers important evidence about how the three-fingered hand of birds evolved from the hand of dinosaurs.
 
The discovery is reported in a paper published in this week's edition of the journal Nature.
 
"This work on dinosaurs provides a whole new perspective on the evolution of bird manual digits," said H. Richard Lane, program director in the National Science Foundation (NSF)'s Division of Earth Sciences, which funded the research.
 
Full article here.
 

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Filed under  //   birds   dinosaurs   evolution   finger homology   Jurassic   Limusaurus inextricabilis   theropods  

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June 4, 2009

First definitive carcharodontosaurid from Asia

shaochilonglowres1

Shaochilong maxilla (top), braincase (middle) and skull roof (bottom) from Brusatte et al., 2009.

 

"While in Beijing I figured I should try to see the specimen, as some authors had suggested that it was a tyrannosauroid or a basal coelurosaur of some kind. Either way, it would provide important data for my thesis. But when I opened the drawer and saw the maxilla and braincase staring back at me, I quickly realized something was wrong. “C.” maortuensis is not a coelurosaur, but possesses a number of unique features seen in Carchrodontosaurus, Giganotosaurus, Mapusaurus, and Acrocanthosaurus—colossal theropods closely related to Allosaurus that are grouped within their own subclade, the Carcharodontosauridae (the shark-toothed reptiles, named for obvious reasons)."

The new name given to this animal, Shaochilong, "meaning “shark teeth dragon” in Chinese, [is an] obvious reference to the carcharodontosaurids."

Brusatte, S., Benson, R., Chure, D., Xu, X., Sullivan, C., & Hone, D.(2009). The first definitive carcharodontosaurid (Dinosauria: Theropoda) from Asia and the delayed ascent of tyrannosaurids Naturwissenschaften DOI: 10.1007/s00114-009-0565-2

Abstract:  Little is known about the evolution of large-bodied theropod dinosaurs during the Early to mid Cretaceous in Asia. Prior to this time, Asia was home to an endemic fauna of basal tetanurans, whereas terminal Cretaceous ecosystems were dominated by tyrannosaurids, but the intervening 60 million years left a sparse fossil record. Here, we redescribe the enigmatic large-bodied Chilantaisaurus maortuensis from the Turonian of Inner Mongolia, China. We refer this species to a new genus, Shaochilong, and analyze its systematic affinities. Although Shaochilong has previously been allied with several disparate theropod groups (Megalosauridae, Allosauridae, Tyrannosauroidea, Maniraptora), we find strong support for a derived carcharodontosaurid placement. As such, Shaochilong is the first unequivocal Asian member of Carcharodontosauridae, which was once thought to be restricted to Gondwana. The discovery of an Asian carcharodontosaurid indicates that this clade was cosmopolitan in the Early to mid Cretaceous and that Asian large-bodied theropod faunas were no longer endemic at this time. It may also suggest that the ascent of tyrannosaurids into the large-bodied dinosaurian predator niche was a late event that occurred towards the end of the Cretaceous, between the Turonian and the Campanian.

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Filed under  //   carcharodontosaurids   dinosaurs   evolution   science   Shaochilong   theropods  

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