On Bissektipelta and Diagnoses of Partial Skulls

["Jaime A. Headden" <qilongia@yahoo.com>]

A curious statement in the diagnosis from Parish and Barrett (2004) for
*Bissektipelta* makes me curious about their reasoning for treating
*Amtosaurus* as a nomen dubium. In this diagnosis, pg. 304, they state
"EMMENDED DIAGNOSIS: The genus can be diagnosed by the presence of a
single autapomorphy: a distinctive pattern of grooves on the dorsal skull
roof, forming a truncated ?Y? shape that separates three flat polygonal
areas of remodelled bone. _In addition, the combined presence of this
feature and of three separate exits for the hypoglossal nerve is unique
among ankylosaurs._"

  It would be of some importance for them to publish the last sentence
(accents are mine) yet treat the lack of any distinct autapomorphy as
reducing the value of *Amtosaurus.* They regard ornamentation pattern as
distinct, but ignore Penkalski (2001) on variation of the cranial dermal
armor in *Euoplocephalus* in which sometimes drastic changes in size and
rugosity will make such a valuation weak, if not useless in some cases.
Such variation occurs among edmontoniine/panoplosaurine nodosaur skulls,
as well, even among the same "species" and has often been used to define
species from one another, as in "Chasternbergia," as well as relative
distortion in the skull and weathering, smoothness within a species, etc..
This would seem to be a need to make a species better by destroying a
worse-weathered specimen, of which neither should have been named, perhaps.

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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