`  ::Ideally the text would be edited to include a discussion of the history of our understanding of the evolutionary relationships between Castor and other rodents, but that discussion doesn't really belong in the section ``Species``. Even if those sentences were factually correct, they seem out of place, and it makes the following paragraph initially confusing to read. I would recommend removing them completely. Another section just prior to ``Species`` entitled ``Evolution and Phylogenetic Relationships`` or something like that, would be ideal. The beaver fossil record is pretty well known, so hopefully someone could eventually come along and add that material into this new section. As for the phylogenetics portion of the section, I would offer this bit of text (at least for now):   :::``Beavers were traditionally classified in the suborder Sciuromorpha along with squirrels (Sciuridae), the mountain beaver (not an actual beaver) (Aplodontidae), gophers (Geomyidae), and pocket mice and kangaroo rats (Heteromyidae), based on the morphology of the masseter musculature Simpson, G.G. (1945) ``The principles of classification and a classification of mammals.`` Bulletin of the American Museum of Natural History 85: 197-203. . This classification was met with skepticism early on, as most other morphological characters, such as the dentition, were not congruent with this system Wood, A.E. (1965) ``Grades and Clades Among Rodents.`` Evolution. 19(1): 115-130.. Today, the zygomasseteric muscle configurations are known to be polyphyletic, having evolved convergently a number of times within Rodentia. Molecular phylogenetics has robustly supported beavers as residing within the suborder Castorimorpha, which includes the Castoridae and the Geomyoidea Carleton, M. D. and G. G. Musser. 2005. Order Rodentia. Pp 745-752 in Mammal Species of the World A Taxonomic and Geographic Reference. Johns Hopkins University Press, Baltimore.McKenna, Malcolm C., and Bell, Susan K. 1997. Classification of Mammals Above the Species Level. Columbia University Press, New York, 631 pp. ISBN 0-231-11013-8..``  ::In the preceding text I cited two traditional papers in rodent taxonomy and two recent-ish books on rodent taxonomy that are congruent with the consensus in the primary literature. Here's a list of papers from the primary literature on rodent molecular phylogentics, in case you're wondering whether there's (still) a consensus on this issue:  ::Adkins et al. (2001) ``Molecular Phylogeny and Divergence Time Estimates for Major Rodent Groups: Evidence from Multiple Genes`` Mol. Biol. Evol. 18(5):777–791  ::Debry and Sagel. (2001) ``Phylogeny of Rodentia (Mammalia) Inferred from the Nuclear-Encoded Gene IRBP`` Molecular Phylogenetics and Evolution 19(2): 290–301.  ::Huchon et al. (2002). ``Rodent Phylogeny and a Timescale for the Evolution of Glires: Evidence from an Extensive Taxon Sampling Using Three Nuclear Genes`` Mol. Biol. Evol. 19(7):1053–1065.  ::Montgelard et al. (2002) ``Molecular Systematics of Sciurognathi (Rodentia): The Mitochondrial Cytochrome b and 12S rRNA Genes Support the Anomaluroidea (Pedetidae and Anomaluridae)`` Molecular Phylogenetics and Evolution 22(2): 220–233.  ::Adkins et al. (2003). ``Higher-level systematics of rodents and divergence time estimates based on two congruent nuclear genes`` Molecular Phylogenetics and Evolution. 26(3): 409–420.   ::Veniamenova et al. (2007) ``Phylogeny of the Order Rodentia Inferred from Structural Analysis of Short Retroposon B1.`` Russian Journal of Genetics 43(7): 757–768.  ::Montgelard et al. (2008) ``Suprafamilial relationships among Rodentia and the phylogenetic effect of removing fast-evolving nucleotides in mitochondrial, exon and intron fragments`` BMC Evolutionary Biology 8:321  ::Blanga-Kanfi et al. (2009) ``Rodent phylogeny revised: analysis of six nuclear genes from all major rodent clades`` BMC Evolutionary Biology 9:71.  ::Churakov et al. (2010) ``Rodent Evolution: Back to the Root`` Mol. Biol. Evol. 27(6):1315–1326.  ::Fabre et al. (2012) ``A glimpse on the pattern of rodent diversification: a phylogenetic approach`` BMC Evolutionary Biology. 12(1): 88.  ::Ryu et al. (2013) ``Complete mitochondrial genome of the Eurasian ﬂying squirrel Pteromys volans(Sciuromorpha, Sciuridae) and revision of rodent phylogeny`` Mol Biol Rep (2013) 40:1917–1926.`