RE: Paronychodon/Richardoestesia

[Michael Mortimer <mickey_mortimer111@msn.com>]

Phil Bigelow wrote-

> Sankey (2003), in a meeting abstract, noted in passing that theropod teeth 
> previously assigned to Paronychodon have been reassigned to Richardoestesia 
> isosceles.
>
> Who is the author (full citation, if possible) of this re-assignment?

Sankey (2002) has suggested Paronychodon and Richardoestesia teeth are 
morphotypes of the same taxon, based on morphology and relative abundance. The 
details of this study have yet to be published, though it does make sense 
stratigraphically, as both taxa first appear in Late Jurassic Europe and spread 
to North America in the Albian, with Late Cretaceous examples known from the 
Western North America, Central Asia and Europe. It's also logical anatomically, 
as Richardoestesia? isosceles would be expected to have some unserrated and 
possibly constricted teeth if it were microraptorian. It should be noted 
Paronychodon has priority over Richardoestesia, and lacustris and caperatus 
both have priority over isosceles. Also, Euronychodon has priority over 
Asiamericana, and portuculensis has priority over both asiatica and asiaticus. 
So if this synonymy is proven, none of the names associated with 
straight-toothed Richardoestesia will survive synonymization. Longrich (2008) 
proposed such a synonymy based on the weak longitudinal ridges on some 
Richardoestesia teeth, but Larson (2008) noted other contemporaneous theropods 
sometimes have weak ridges too (tyrannosaurids, 'velociraptorines') and that 
varied morphologies probably reflect positional variation in Paronychodon 
teeth. Thus it is unlikely they existed in the same jaws as Richardoestesia 
teeth.
 
HOWEVER, Hwang (2005, 2007) found that Paronychodon teeth are identical in 
enamel microstructure to serrationless troodontids like Byronosaurus and IGM 
100/1323, while Richardoestesia more closely matched dromaeosaurids.  So their 
proposed synonymy is incorrect.
 
Sankey, 2002. Theropod dinosaur diversity in the latest Cretaceous 
(Maastrichtian) of North America. Journal of Vertebrate Paleontology. 22(3), 
103A. 
 
Hwang, 2005. Phylogenetic patterns of enamel microstructure in dinosaur teeth. 
Journal of Morphology. 266, 208-240. 

Hwang, 2007. Phylogenetic patterns of enamel microstructure in dinosaur teeth. 
PhD thesis. Columbia University. 274 pp.
 
Larson, 2008. Diversity and variation of theropod dinosaur teeth from the 
uppermost Santonian Milk River Formation (Upper Cretaceous), Alberta: a 
quantitative method supporting identification of the oldest dinosaur tooth 
assemblage in Canada. Canadian Journal of Earth Science. 45, 1455-1468.

Longrich, 2008. Small theropod teeth from the Lance Formation of Wyoming, USA. 
in Sankey and Baszio (eds). Vertebrate Microfossil Assemblages: Their Role in 
Paleontology and Paleobiogeography. Indiana University Press, Bloomington, 
Ind.. pp. 135-158. 
 
Mickey Mortimer                                           
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