Silesauridae

Taxa on This Page

1. Silesauridae X

The protodinosaur Silesaurus oploensis, from the Norian of Silesia, Poland Artwork by Dmitry Bogdanov, via Wikipedia, GNU Free Documentation/Creative Commons Attribution Share Alike

The Silesauridae are one of those groups that were unknown even just ten years ago, showing that paleontology, like science in general, is always full of new discoveries. They show that protodinosaurs were far more widespread and diverse than had previously been thought. The earliest, but not the most basal, of the silesaurids, Asilisaurus, lived as long ago as the Anisian (Nesbitt et al 2010). Some taxa previously included among the ornithischia, such as Technosaurus, have since been relocated here. Like other protodinosaurs, these were small, lightly built animals, about one and a half meters in length. They seem to have been mostly quadrapedal. Although considered the sister grpoup to dinosaurs, rather than actual ancestors, at least one genus, the herbivorous The well-preserved jaw indicates that Sacisaurus posesses a process at the tip that resembles the ornithischian predentary bone. Whether this is the result of homoplasy (convergence) or homology (common ancestry) will determine whether this taxon should be reassigned to the ornithischia, although in other respects it resembles Silesaurids such as Diodorus (Kammerer et al 2011). Alternatively, the ornithischian-saurischian split might be pushed back to the Silesauridae, which means the group itself might also be paraphyletic, or at least need redefining as several smaller monophyletic clades.

Descriptions

Skeletal reconstruction of Asilisaurus, with missing bones in gray. Image by S. Nesbitt. Copied from Chinlea

Silesauridae:  Asilisaurus, Eucoelophysis, Silesaurus, Lewisuchus (= Pseudolagosuchus), Technosaurus, and possibly Diodorus and Sacisaurus

Comments: "Named in 2010 by paleontologist Max C. Langer and colleagues from Brazil and Argentina. They defined it as a branch-based clade of all archosaurs closer to Silesaurus opolensis than to either Heterodontosaurus tucki or Marasuchus lilloensis. At the same time, a second group of scientists independently named Silesauridae as a node-based clade consisting of Lewisuchus, Silesaurus, their common ancestor and all its descendants. (Nesbitt et al 2010) Currently, both definitions encompass the same group of animals." - Wikipedia.