re: where have all the ornithischians gone?/Cart before horse

[david peters <davidrpeters@earthlink.net>]

Tim Williams wrote:

Did your analysis include _Ctenosauriscus_? 

>>>>No. As I understand it, only a vertebral spine is known. Let me know if 
>>>>otherwise, but note that Arizonasaurus _is_ a rauisuchian with a high 
>>>>spine, and it is not related.

Lagosuchians? 

>>>>Yes. Marasuchus sister to Herrarasaurus within Saurischia.

I'm curious not just about what's attracting _Silesaurus_ to _Pisanosaurus_, 
but what's pulling _Silesaurus_ *away* from the basal dinosauromorphs. 

>>> Name a taxon that would be a better sister taxa. I'll plug it in.

And what force is splitting _Lotosaurus_ off from the other crocodile-normal- 
tarsus taxa?

>>>>> The rest of Lotosaurus, other than the tarsus. Remember, croc normal 
>>>>> tarsus shows up three times: in basal Rauisuchids (with Euparkeria 
>>>>> showing as a precursor), in Crocodiliformes (not basal bipedal crocs), 
>>>>> and in lotosaurs. The latter two as reversals from bipedal (or nearly so) 
>>>>> ancestors at the base of the Archosauria.

PAUP nests everything, as you know, so I'm going to get "a hit" somewhere. 
Among 124 diapsids (with no more than a few in every clade) Lotosaurus comes 
out closest to Silesaurus and Pisanosaurus. 

Like Jaime, I'm curious what characters unite this trio (_Lotosaurus_, 
_Silesaurus_, _Pisanosaurus_).

>>>> That was sent privately. I'll try to do the same over the weekend when I'm 
>>>> back at the studio.

PS. Longisquama and Cosesaurus have also been PAUP analyzed. And we've all been 
waiting five years for the next guy/gal brave enough to test them. 
That brave guy would be Senter. His analysis is the most recent (2004) to look 
at _Longisquama_. He found_Longisquama_ to be outside the Neodiapsida (so well 
outside of the archosaurs), along with with the drepanosaurids. Senter didn't 
examine _Cosesaurus_ directly, but it looks like a fairly conventional 
prolacertiform.

>>>> Senter's paper used too few taxa (20). Taxa jump around because they are 
>>>> attracted to sister taxa. Too few to choose from and you get attraction by 
>>>> default, because "PAUP nests everything". In my work, I've included 
>>>> everything from Gephyrostegus to Iguana and Lotosaurus, so _everyone_ is 
>>>> invited to that dance. Without Huehuecuetzpalli and other squamates, 
>>>> Macrocnemus and Langobardisaurus are attracted to Prolacerta as Senter 
>>>> showed. Without Iguana, Sphenodon and Homeosaurus, Gephyrosaurus and 
>>>> Mesosuchus are attracted to Youngina, as Senter showed. Each of these 
>>>> small (smaller than 30 taxa) studies give us something to chew on, but 
>>>> without the one overall study to set the blueprint up you're putting 
>>>> bathrooms next to kitchens. Someone is goin to complain. Ever since 
>>>> Gauthier 1986 we've been putting the cart before the horse. Once the 
>>>> overall blueprint is established, we can start breaking into smaller 
>>>> clades more successfully. 

Best,
David

Cheers
Tim