Eolambia and Pararhabodon (was Re: New issue of JVP 2001(2))

["Tim Williams" <twilliams_alpha@hotmail.com>]

> A reanalysis of the phylogenetic position of Eolambia
> caroljonesa (Dinosauria, Iguanodontia). JASON J. HEAD,
> pages 392?396.


This is a particularly interesting paper.  Jason Head shakes the hadrosaurid
family tree again, this time arguing that _Eolambia_ is not a lambeosaurine,
nor even the sister taxon to the Lambeosaurinae.  Kirkland (1998)
interpreted this beast as a primitive, crestless lambeosaurine with some
hadrosaurine-like traits.  According to Head, the cranial features regarded
as lambeosaurine synapomorphies are erroneous interpretations of the
material on Kirkland's part.  Certain lambeosaurine characters described by
Kirkland in the postcranium actually have a wider distribution within the
Iguanodontia - like the distally expanded ischium and tall neural spines on
the caudals.  Head (2001) places _Eolambia_ closest to _Probactrosaurus_
(likewise considered as non-lambeosaurine).

Head (2001) is also inclined to scratch _Pararhabdodon_ from the
Lambeosaurinae (referred to this group by Casanovas et al., 1999).  Among
the rather un-lambeosaurine features of this Maastrichtian genus,
_Pararhabdodon_ has only around 35 tooth positions in the maxilla and
dentary, less than both hadrosaurines and lambeosaurines.


Tim


------------------------------------------------------------

Timothy J. Williams

USDA/ARS Researcher
Agronomy Hall
Iowa State University
Ames IA 50014

Phone: 515 294 9233
Fax:   515 294 3163

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