RE: Dinosaur papers: a new hope

["Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>]

> From: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu]On Behalf Of
> Tim Williams

[snip]

> Pol, D. and Powell, J.W. (2007). Skull anatomy of _Mussaurus patagonicus_ 
> (Dinosauria: Sauropodomorpha) from the Late Triassic of Patagonia. 
> Historical Biology 19(1): 125-144.
> 
> ABSTRACT: "The skull anatomy of _Mussaurus patagonicus_ from the Upper 
> Triassic Laguna Colorada Formation is described based on a revision of the 
> type material and several recently found specimens. The studied material 
> include two distinct size classes of individuals. The type material consists 
> of extremely young individuals whereas the new specimens are interpreted as 
> juvenile or subadult individuals. The latter are significantly larger, 
> having a skull approximately three times longer than the type material. The 
> skull anatomy of this taxon shows derived characters shared with some basal 
> sauropodomorphs and eusauropods, which are absent in other basal 
> sauropodomorphs (e.g. _Thecodontosaurus_, _Plateosaurus_). These include the 
> presence of an extension of the infratemporal fenestra ventral to the orbit, 
> dorsal and anterior rami of quadratojugal subperpendicular to each other, 
> dorsoventral expansion of dentary at mandibular symphysis, slightly 
> procumbent teeth with broad serrations restricted to the apical region 
> (absent in some teeth). Differences among the studied specimens helps to 
> understand the early ontogenetic changes occurring in this basal 
> sauropodomorph, revealing major changes in the rostral and temporal 
> regions."
> 
> 
> Sereno, P.C. (2007). The phylogenetic relationships of early dinosaurs: a 
> comparative report. Historical Biology 19(1): 145-155.
> 
> ABSTRACT: "Surprising new anatomical information has come to light for the 
> early dinosaurs _Eoraptor lunensis_ and _Herrerasaurus ischigualastensis_. 
> _Eoraptor_ has a mid mandibular jaw joint, and _Herrerasaurus_ has a 
> promaxillary fenestra at the anterior end of the antorbital fossa. Initial 
> cladistic interpretation placed _Herrerasaurus_ outside Dinosauria. Since 
> then, _Eoraptor_ and _Herrerasaurus_ have been placed at the base of 
> Saurischia or within Theropoda in two large-scale quantitative analyses. A 
> comparative approach is taken here to show, first, that character choice is 
> a major factor behind differing results; only half of the character data 
> critical for each interpretation is incorporated into the opposing analysis. 
> In that shared portion of data, furthermore, nearly 40 percent of character 
> state scores vary for identical, or comparable, ingroup taxa. Resolving 
> these conflictive interpretations is clearly where future progress will be 
> made in understanding early dinosaur phylogenesis."
> 
I would greatly appreciate the Mussaurus and Sereno papers, myself...

                Thomas R. Holtz, Jr.
        Senior Lecturer, Vertebrate Paleontology
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
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