@article {25, title = {Re-evaluation of Sinocastor (Rodentia: Castoridae) with implications on the origin of modern beavers.}, journal = {PLoS One}, volume = {5}, year = {2010}, month = {2010 Nov 15}, pages = {e13990}, abstract = {

The extant beaver, Castor, has played an important role shaping landscapes and ecosystems in Eurasia and North America, yet the origins and early evolution of this lineage remain poorly understood. Here we use a geometric morphometric approach to help re-evaluate the phylogenetic affinities of a fossil skull from the Late Miocene of China. This specimen was originally considered Sinocastor, and later transferred to Castor. The aim of this study was to determine whether this form is an early member of Castor, or if it represents a lineage outside of Castor. The specimen was compared to 38 specimens of modern Castor (both C. canadensis and C. fiber) as well as fossil specimens of C. fiber (Pleistocene), C. californicus (Pliocene) and the early castorids Steneofiber eseri (early Miocene). The results show that the specimen falls outside the Castor morphospace and that compared to Castor, Sinocastor possesses a: 1) narrower post-orbital constriction, 2) anteroposteriorly shortened basioccipital depression, 3) shortened incisive foramen, 4) more posteriorly located palatine foramen, 5) longer rostrum, and 6) longer braincase. Also the specimen shows a much shallower basiocciptal depression than what is seen in living Castor, as well as prominently rooted molars. We conclude that Sinocastor is a valid genus. Given the prevalence of apparently primitive traits, Sinocastor might be a near relative of the lineage that gave rise to Castor, implying a possible Asiatic origin for Castor.

}, keywords = {Animals, China, Female, Fossils, Geography, Male, North America, Phylogeny, Rodentia, Skull, Species Specificity}, issn = {1932-6203}, doi = {10.1371/journal.pone.0013990}, author = {Rybczynski, Natalia and Ross, Elizabeth M and Samuels, Joshua X and Korth, William W} } @article {28, title = {Comparative morphological study on the stereo-structure of the lingual papillae and their connective tissue cores of the American beaver (Castor canadensis).}, journal = {Okajimas Folia Anat Jpn}, volume = {82}, year = {2006}, month = {2006 Feb}, pages = {127-37}, abstract = {

The lingual papillae and the connective tissue cores (CTC) of the American beaver were examined by light and scanning electron microscopy. The tongue of American beaver was about 9 cm in length, 3.5 cm in width, and has a lingual prominence. Four types of papillae (filiform, fungiform, vallate and foliate papillae) were observed. The filiform papillae can be classified into three types (filiform, large filiform and dorm-like papillae). Filiform papillae distributed on the anterior tongue and posterior of the lingual prominence consisted of a posterior thick main process and several small accessory processes. After removal of the epithelium, the CTCs of the filiform papillae had U-shaped, horseshoe-like primary cores with 10-15 rod-shaped small accessory cores. Large filiform papillae were distributed at the anterior margin of the lingual prominence. Dome-like papillae were distributed at the top of lingual prominence. Fungiform papillae were observed two types. Fungiform papillae, which were distributed at the anterior tongue, were round shaped. Fungiform papillae of the posterior of the lingual prominence were large and surrounded with a papillary groove. At the posterior of the tongue, three vallate papillae were arranged in a triangular pattern. Foliate papillae were on 22 to 25 parallel ridges and grooves.

}, keywords = {Animals, Connective Tissue, Epithelium, Feeding Behavior, Female, Male, Microscopy, Microscopy, Electron, Scanning, Rodentia, Tongue}, issn = {0030-154X}, doi = {10.2535/ofaj.82.127}, author = {Shindo, Junji and Yoshimura, Ken and Kobayashi, Kan} } @article {29, title = {The chromosomes of the Canadian Beaver Castor canadensis.}, journal = {Can J Genet Cytol}, volume = {21}, year = {1979}, month = {1979 Mar}, pages = {37-42}, abstract = {

A chromosome analysis of 24 Canadian beavers, Castor canadensis Kuhl (12 males and 12 females), captured in Laurentides Park, Q{\'e}bec, has been performed from preparations of blood lymphocyte and skin cultures. The chromosome number was found to be 2n = 40. Measurements were made to determine relative lengths and arm ratios of chromosomes, which are metacentric or submetacentric. Results are in agreement with those already published regarding the chromosome number, but differ in the identification of the X chromosome, and in the morphology of the Y and some autosomes. C- ad G-banding techniques allowed the precise identification of individual chromosome pairs. A detailed idiogram of G-bands is presented.

}, keywords = {Animals, Chromosome Banding, Chromosomes, Female, Karyotyping, Male, Rodentia, Sex Chromosomes}, issn = {0008-4093}, doi = {10.1139/g79-006}, author = {Genest, F B and Morisset, P and Patenaude, R P} }