Re: Herrerasaurus - some questions

[Benn Breeden <bbreeden@umd.edu>]

Depending on who you ask, herrerasaurs may not even be theropods. 

There are certainly those who consider them (and Eoraptor) to be primitive 
members of Theropoda, and there is compelling evidence for this argument. 
However, the presence of a number of traits shared by sauropodomorphs and 
theropods that are lacking in Eoraptor and herrerasaurs indicates that they may 
simply be primitive members of Saurischia. Regardless, whether theropod or 
not, it can absolutely be inferred that there were more primitive members of 
Dinosauria than Herrerasaurus--after all, Saurischia and Ornithischia share a 
common ancestor that would have been dinosaurian by definition.

Primitive saurischians and ornithischians alike appear in the fossil record at 
the 
beginning of the the Late Triassic, and dinosauromorphs appear in the middle 
of the Middle Triassic. So it follows that the earliest dinosaurs likely 
emerged at 
some point between late Middle Triassic and the early Late Triassic.

That being said, I absolutely agree that Herrerasaurus is a very neat beastie 
indeed!


Benn Breeden
Undergraduate Student of Geology
University of Maryland, College Park

---- Original message ----
>Date: Fri, 28 Aug 2009 19:05:31 -0700 (PDT)
>From: B tH <soylentgreenistrex@yahoo.com>  
>Subject: Herrerasaurus - some questions  
>To: dinosaur@usc.edu
>
>This neat beastie has been called one of the earliest dino's - but it's 
>relatively 
larger size and (to me) a completely viable predator anatomy says it is more 
one 
of the earliest discovered more than a first dinosaur.  The experts call it 
"primitive" and I'm sure it is, but it still seems to have been a very capable 
theropod.
>
>Are there finds that indicate an ancestry to Herrerasaurus (that are still 
>dino's)?
>
>How far back do most of you consider that dino's first emerged?  The first 
>half 
of the Triassic?
>
>Stop retro-engineering chickens and bring one of these babies back!  They 
look like they could have taken one of us out without much effort.
>
>
>      
>