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quinta-feira, 17 de março de 2011

Evolução 225: Uteodon e Osmakasaurus

Fonte:
Zootaxa 2783: 52–68 (2011)

The taxonomy of species assigned to Camptosaurus (Dinosauria: Ornithopoda)
ANDREW T. MCDONALD

Abstract
The taxonomic affinities of species assigned to Camptosaurus are reassessed in light of firsthand examination of the relevant specimens and a new phylogenetic analysis, the first to incorporate all putative species of Camptosaurus. “Camptosaurus” valdensis is found to be an indeterminate dryosaurid. The species C. prestwichii, C. aphanoecetes, and C. depressus differ in several important details from the type species, C. dispar, and are assigned to different genera as Cumnoria prestwichii, Uteodon aphanoecetes gen. et comb. nov., and Osmakasaurus depressus gen. et comb. nov. The recent assignment of O. depressus to the genus Planicoxa is considered unjustified. Key words: Camptosaurus dispar, Cumnoria prestwichii, Uteodon aphanoecetes gen. et comb. nov., Osmakasaurus depressus gen. et comb. nov., “Camptosaurus” valdensis, Planicoxa venenica .
Introduction
The type species of the genus Camptosaurus, C. dispar, was established by Marsh (1879) based upon material from
Como Bluff Quarry 13 in the Upper Jurassic Salt Wash Member of the Morrison Formation (Foster 2003; Carpenter & Wilson 2008). Since then, numerous iguanodontian species and specimens from the Callovian to the Aptian, a span of approximately 40 million years, of the United States and England have been placed in Camptosaurus. Some, such as Callovosaurus leedsi (Lydekker 1889; Galton 1980; Ruiz-Omeñaca et al. 2007), Owenodon hoggii
(Owen 1874; Norman & Barrett 2002; Galton 2009), and the holotype skull of Theiophytalia kerri (Brill & Carpenter 2007) have already been reassigned to other genera. C. depressus (Gilmore 1909) has also been reassigned, to the genus Planicoxa as P. depressa (Carpenter & Wilson 2008), though this assignment is not upheld herein. In contrast, C. prestwichii (Hulke 1880) is almost universally regarded by recent authors as referable to Camptosaurus (Galton & Powell 1980; Norman 2004; Carpenter & Wilson 2008; but see Naish & Martill 2008). The recently named species C. aphanoecetes (Carpenter & Wilson 2008) has not been extensively discussed elsewhere and its placement in Camptosaurus has not been tested.
To elucidate the relationships of the various species assigned to Camptosaurus, they were incorporated into a new phylogenetic analysis of basal iguanodont relationships. Apart from C. dispar, none of these species had ever been included in such an analysis. Determining the interrelationships of the putative species of Camptosaurus to each other and to other basal iguanodonts has implications for the taxonomy and the spatial and temporal distributions
of the genus.

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