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Re: Chromogisaurus novasi, new guaibasaurid (basal sauropodomorph)



It all comes down to utility.  I named the clade Paratypothoracisini
in 2007 which contained only three taxa, because many of the osteoderm
morphologies within the clade are similar and preclude assignment of
isolated material to a specific genus.  It was a pain to keep refering
to them as the "Paratypothorax-like aetosaurs", especially when
cataloguing the material.

On Tue, Aug 3, 2010 at 7:05 AM, Mike Taylor <mike@indexdata.com> wrote:
> 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
>>
>>
>>
>