Dinosauromorpha

Taxa on This Page

1. Dinosauromorpha
2. Lagerpeton X

Dromomeron romeri, a Lagerpetontid dinosauriform from the Late Triassic ( Norian) of New Mexico. This animal, closely relate dto the earlier, South American Lagerpeton, is one of a number of new discoveries that have shed light on the evolution of ornithodirans and the ancestry of dinosaurs Artwork by Nobu Tamura, via Wikipedia, GNU Free Documentation/Creative Commons Attribution Share Alike

The Silesaurid protodinosaur Silesaurus oploensis, from the Norian of Silesia, Poland. Length about 2.3 meters Artwork by Nobu Tamura, via Wikipedia, GNU Free Documentation/Creative Commons Attribution Share Alike

Evolution is an unbroken sequence. Bridging the divide between the thecodontian archosaurs and the first dinosaurs are a number of small, active, lightly built animals, the fossil remains of most of which have only come to light in the last few years. These are the protodinosaurs [1] or paleodinosaurs as Greg Paul refers to them in his early opus Predatory Dinosaurs of the World (although Staurikosaurus which he places in the paleodinosaurs is more properly included with the true dinosaurs). While very much playing second fiddle to their larger and more heavily built crurotarsan contemporaries, the little protodinosaurs would soon give rise to the true dinosaurs, and co-exist alongside them for at least ten million years or more. Their delicate bones would be less likely to be preserve than the heavy skeletons and armour plates of the large phytosaurs and aetosaurs, or the abundant remains of the traversodonts, dicynodonts, and replacing them, prosauropods. So it may well be that these little mesovertebrates were more common and diverse than they appear, and may have played an important role in Triassic terrestrial faunas. The fact that they flourished in a Norian world populated by herrerasaurid and coelophysid dinosaurs means that their extinction was not caused by competition with their very successful offspring, nor did they seme to have been discouriaged by sphenosuchid protocrocodiles, despite the latter being remarkably similar in size, build, and no doubt general appearance. It is more likely that were one of the many victims of the end-Triassic extinction event, although in view of the survival of sphenosuchians into the middle Mesozoic, it may well be that Jurassic protodinosaur remains may one day turn up. For now, these creatures remain one of the more intriguing of Triassic fuanas. MAK120206

[1] Or, as they are more generally referred to, the dinosauriformes or dinosauromorphs. Technically these latter terms designate clades that include birds and dinosaurs as well as protodinosaurs. In order to emphasise the ancestral and transitional nature of these early animals, we have chosen to retain this paraphyletic term.

Descriptions

Dinosauromorpha: Avipes? Birds > pterosaurs.

Lagerpeton:

Links: DinoData: Lagerpeton; Lagerpeton -- The Dinosauricon; dinosauromorpha.

References: Arcucci 1997). 010324.