Craniological features of the muskrat (Ondatra) and its differences from the genus Arvicola

An overview of the craniological differences between muskrats and sympatric Arvicola based on materials from Ukraine is presented. One of the most notable differences is the absence of cement on the molars of muskrats, which is typical for all Arvicolini. The shape of the occlusal surface of muskrat molars is also characterised by a smaller number of enamel loops and a more rounded shape. The shape of the connection between the pterygoid processes of the sphenoid bones and the auditory bulla is different in these two genera. A number of other differences have been described, including the shape of the sphenoid bone openings, which are wider in muskrats with deeper paired oval holes.