Abstract

A morphologic and morphometric study of teeth of some beavers of the group of Palaeocastorinae is presented in order to demonstrate that statistic analyses of tooth parameters could contribute to a better understanding of this group of beavers. The focus was laid on larger samples of Capacikala gradatus, Palaeocastor nebrascensis and "Capatanka" cankpeopi. Additionally, some cranial measurements are briefly considered. Overall morphology of the teeth is very similar in the three genera and can hardly be used to differentiate the considered taxa. Except for hypo- and mesostriae, striae in general are rare in the available material. Whether their rarity is due to how few unworn or little worn teeth are available, or due to the lack of these structures is unclear. Striae thus cannot be considered of taxonomic value in this group. Likewiese, neither the presence of anterior or posterior fossettes, nor their shape and orientation are taxonomically diagnostic.

The discriminant analysis of wear-independent residuals showed some separation of Capacikala gradatus, "Capatanka" cankpeopi and Palaeocastor nebrascensis with reasonable sized samples, but not all statistically significantly. The separation of all studied taxa on the basis of the wear-independent residuals of teeth showed some power to separate groups, but here the influence of the differences in sample seizes might be too strong to make clear statements. Also the comparison of tooth row length did not give a clear size separation between all taxa. Size data on skulls are limited and may not represent the real variation.

The data of tooth morphometry indicate similarities between C. cankpeopi and C. magnus thus their taxonomic status should be reviewed. Also the differentiation between Capacikala parvus, Capacikala gradatus and Capatanka minor should be reviewed as well as the species assignments in Palaeocastor. Material assigned to Palaeocastor sp. could be separated into three size forms. P. fossor is clearly separated.

Clara Stefen. Senckenberg Naturhistorische Sammlungen Dresden, Museum für Tierkunde, Königsbrücker Landstraße 159, 01109 Dresden

KEY WORDS: Tooth morphology, morphometrics, discriminant analysis

PE Article Number: 13.1.2A
Copyright: Society for Vertebrate Paleontology March 2010
Submission: 17 February 2009. Acceptance: 30 October 2009