Basal dinosaur I

[HPB1956@aol.com]

A big Thank you to Bruno for reporting about a Middle Triassic (?Ladinian)
ceratosaur found in Brazil. So after 2 years of W4TP (1) we've finally got
the description.

> The presence of large size "thecodonts" (?Prestosuchus)
> the traversodontid (?Massetognathus) and medium size dicynodnts
> (? Dinodontosaurus), as well the absence of Upper Triassic
> vertebrates, permit to infer a Middle Triassic (?Ladinian) age
> for stratigraphic levels of ceratosaur material.

It would be nice to have a radiometric dating. Same problem here as with the two
unnamed dinosaurs from Madagascar (2); Is it a late surviving fauna or not?

But this dating would nicely match with the late Ladinian-early Carnian
heterodontosaurian maxillary mentionened in (3) by Mickey Mortimer.
BTW: Does anybody knows how this dating was determined?

> These findings partially corroborate the hypothesis that the divergence
> between Ceratosauria and Tetanurae occurred before Upper Triassic.
> However the presence of a typical Ceratosauria in the Middle Triassic
> (?Ladinian) permit to suppose that such divergence could be have occurred
> at the Anisian or even before.

I would bet on it.

Cheers


Heinz Peter Bredow



(1) http://www.cmnh.org/dinoarch/2001May/msg00914.html
    Oldest Dinosaur Discovery
(2) http://www.cmnh.org/dinoarch/1999Oct/msg00388.html
    early dino news from Madagascar
    Flynn, J.J. et al. (1999).  A Triassic fauna from Madagascar, including 
    early dinosaurs.  Science 286 (5440): 763-765.
(3) http://www.cmnh.org/dinoarch/2001Jun/msg00407.html  Re: ORNITISCHIANS :-)
    BAEZ, A.M. and MARSICANO, C.A., 1998. A heterodontosaurian
    ornithischian in the Upper Triassic of southern Patagonia? Gondwana 10:
    Event Stratigraphy of Gondwana, Journal of African Earth Sciences