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Platecarpus tympaniticus - how to analyze a nomen dubium
Tim Williams and I have been having quite a discussion on the DML this year
about nomina dubia and how they should be treated. In the most recent JVP,
Konishi et al. (2010) present an excellent example of my philosophy in this
matter. Platecarpus tympaniticus is the type species of this well known genus
of mosasaurs. It's based on fragments described by Leidy back in 1865 and
ignored (Williston, 1898) or declared a nomen dubium (Russell, 1967) since.
Incidentally, note that despite the fact Russell thought it was indeterminate
within the genus Platecarpus, he retained it as the type species and kept other
diagnostic species in the genus (like I'm recommending for Stegosaurus).
Konishi and Caldwell (2009) even noted two species its quadrate could not be
distinguished from, qualifying it as a nomen dubium by my definition. Yet all
of these were just mentions in passing. It had never actually been redescribed
since Leidy. Based on what Tim has written on nomina dubia, he would say why
bother going through the motions to compare Platecarpus tympaniticus (*cough*
Ceratops, Rapator, Stegosaurus armatus *cough*) in detail to other species?
Just declare another species the type of Platecarpus or start using Lestosaurus
for the valid species and banish Platecarpus to nomen dubium oblivion.
But Konishi et al. wanted to do actual science instead. They wrote over two
pages of description and discussion on Platecarpus' holotype, and provided
numerous large photos and illustrations for their readers. They found that
even though the quadrate could not be distinguished from two other species, the
previously unconsidered basioccipital and cervicals could be distinguished from
all but P. ictericus. Thus P. ictericus is a junior synonym, and P.
tympaniticus is valid after all. But we wouldn't know any of this if we
followed Tim's methodology and took the easy way out, and Cope's taxon would
have been unfairly tossed aside.
Konishi, Caldwell and Bell, 2010. Redescription of the holotype of Platecarpus
tympaniticus Cope, 1869 (Mosasauridae: Plioplatecarpinae), and its implications
for the alpha taxonomy of the genus. Journal of Vertebrate Paleontology. 30(5),