Re: Chromogisaurus novasi, new guaibasaurid (basal sauropodomorph)

[Mike Taylor <mike@indexdata.com>]

On 2 August 2010 16:01, Thomas R. Holtz, Jr. <tholtz@umd.edu> wrote:
> http://www.informaworld.com/smpp/content~db=all~content=a924950072~frm=title
> link
>
> Ezcurra, M. D. 2010. A new early dinosaur (Saurischia: Sauropodomorpha) from
> the Late Triassic of Argentina: a reassessment of dinosaur origin and
> phylogeny. Journal of Systematic Palaeontology 8: 371-425.
>
> Discussed at:
>
> http://chinleana.blogspot.com/2010/07/new-late-triassic-sauropodomorph.html
>
> Abstract:
> Abstract
> It was traditionally thought that the oldest known dinosaur assemblages were
> not diverse, and that their early diversification and numerical dominance
> over other tetrapods occurred during the latest Triassic. However, new
> evidence gathered from the lower levels of the Ischigualasto Fm. of
> Argentina challenges this view. New dinosaur remains are described from this
> stratigraphical unit, including the new species Chromogisaurus novasi. This
> taxon is distinguished from other basal dinosauriforms by the presence of
> proximal caudals without median notch separating the postzygapophyses,
> femoral lateral surface with deep and large fossa immediately below the
> trochanteric shelf, and metatarsal II with strongly dorsoventrally
> asymmetric distal condyles. A phylogenetic analysis found Chromogisaurus to
> lie at the base of Sauropodomorpha, as a member of Guaibasauridae, an early
> branch of basal sauropodomorphs composed of Guaibasaurus, Agnosphitys,
> Panphagia, Saturnalia and Chromogisaurus. Such an affinity is for the first
> time suggested for Guaibasaurus, whereas Panphagia is not recovered as the
> most basal sauropodomorph. Furthermore, Chromogisaurus is consistently
> located as more closely related to Saturnalia than to any other dinosaur.
> Thus, the Saturnalia + Chromogisaurus clade is named here as the new
> subfamily Saturnaliinae. In addition, Eoraptor is found to be the
> sister-taxon of Neotheropoda, and herrerasaurids to be non-eusaurischian
> saurischians. The new evidence presented here demonstrates that dinosaurs
> first appeared in the fossil record as a diverse group, although they were a
> numerically minor component of faunas in which they occur. Accordingly, the
> early increase of dinosaur diversity and their numerical dominance over
> other terrestrial tetrapods were diachronous processes, with the latter
> preceded by a period of low abundance but high diversity.
>
> No, I do not yet have a pdf, but am working on it.
>
> Congrats to Martin Ezcurra on the paper, and to Fernando Novas (as I am
> assuming he is the honoree of the trivial name).

... though one has to question how badly the world needed the
clade-name Saturnaliinae.  Should we now expect papers on the
palaeobiology of the saturnaliines, or is there some other actual
purpose envisaged for this name?

Not every two-taxon terminal clade needs to be named.




>
>
> Thomas R. Holtz, Jr.
> Email: tholtz@umd.edu   Phone: 301-405-4084
> Office: Centreville 1216
> Senior Lecturer, Vertebrate Paleontology
> Dept. of Geology, University of Maryland
> http://www.geol.umd.edu/~tholtz/
> Fax: 301-314-9661
>
> Faculty Director, Science & Global Change Program, College Park Scholars
> http://www.geol.umd.edu/sgc
> Fax: 301-314-9843
>
> Mailing Address:        Thomas R. Holtz, Jr.
>                        Department of Geology
>                        Building 237, Room 1117
>                        University of Maryland
>                        College Park, MD 20742 USA
>
>
>