[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Dinos in the Southern Hemisphere: Sereno et al. and the VII Mesozoic Terrestrial Ecosystems Symposium



Greetings, all.

A couple of recent items of interest concerning dinosaurs and the Southern
Hemisphere.

The first is the brand new paper by Sereno et al. in which _Nigersaurus_ and
_Jobaria_ are named:
Paul C. Sereno, Allison L. Beck, Didier B. Dutheil, Hans C. E. Larsson,
Gabrielle H. Lyon, Bourahima Moussa, Rudyard W. Sadleir, Christian A. Sidor,
David J. Varricchio, Gregory P. Wilson, and Jeffrey A. Wilson.  1999.
Cretaceous sauropods from the Sahara and the uneven rate of skeletal
evolution among dinosaurs.  Science 286: 1342-1347.

As previously mentioned, _Jobaria_ is found to be the sister group to
Neosauropoda, and _Nigersaurus_ is a basal rebbachisaurid diplodocoid.
Unfortunately, the details of the phylogenetic analysis in question are not
provided in this paper: readers are referred to Jeff Wilson's disseration.

The authors point out that the original material of "_Rebbachisaurus
tamesnensis_" of the Tiouraren Fm. (which produces _Jobaria_ and
_Afrovenator_) are not diagnostic, and indeed no type specimen was assigned.
It is likely that this material may contain _Jaboria_ fossils, as _Jaboria_
is the most common large vertebrate in the unit.  One of the derived
features of _Jaboria_ is a weird horseshoe-shaped chevron 1.

Okay, maybe it's just my Late K Asiamerican bias showing, but the Gadoufaoua
seems to be turning into the Land of Weird Dinosaurs: _Suchomimus_,
_Ouranosaurus_, _Lurdusaurus_, and now _Nigersaurus_ (the sauropod who
thought it was a neornithischian, or white rhino, or rodent, or vacuum
cleaner...). I would REALLY like to see a skull reconstruction of
_Nigersaurus_!  It is, incidentally, a "small" sauropod (small for a
sauropod = 15 m length).  The authors suggest that _Nigersaurus_ belongs in
the clade Rebbachisauridae with _Rayososaurus_, _Rebbachisaurus_, and a
dentary from the Campanian of Argentina referred to _Antarctosaurus_ by
Huene (in fact, the specimen that I think they are talking about is part of
the type of "_A." wichmannianus_: plate 29 Figs. 5a-d of Huene 1929 (Anales
del Museo de La Plata, Ser. 2)).

The authors also observe that although the order of appearance of clades of
dinosaurs is often correlated with their branching order, there is a very
uneven rate of evolution in these branching events.  The number of
synapomorphies between nodes shows no significant correlation with the
amount of time between branching events (or the duration of missing
ancestral lineages).  In basal synapsids, however, there is a stastically
significant correlation.

Also, I just got a copy (actually, an electronic download) of the abstracts
volume of the VII International Symposium on Mesozoic Terrestrial
Ecosystems, held in Buenos Aires shortly before SVP this year (hence I could
not go... bummer).  Lots of good stuff in there.  I'll mention more later,
but one I think that will have some interest first: Novas & Bandyopadhyay
reviewed the theropod material of India and find:
_Indosuchus_ & _Indosaurus_ ARE abelisaurids;
_Laevisuchus_ is a small abelisaurid, with diagnostic cervical vertebrae;
"_Compsosuchus_", "_Dryptosauroides_", "_Ornithomimoides_", and
"_Jubbulpuria_" are abelisaurid cervicals and caudals, but cannot be matched
with certaintly to the diagnostic taxa _Indosuchus_, _Indosaurus_, and
_Laevisuchus_'
_Indosuchus_ seems to be flat headed _Abelisaurus_ like form.

Good to see someone sorting this mess out!

Later, everybody!

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-314-7843