Paleobiology of Mesocyon temnodon; a Preliminary Study

SPEARING, Kurt D; Morningside College, Sioux City, IA.  CUSTER, Riley H; Morningside College, Sioux City, IA


The Oligocene canid, Mesocyon temnodon, is known from specimens collected from localities in South Dakota, North Dakota, Wyoming, Colorado and Nebraska. It is a member of the subfamily Hesperocyoninae, however as it is in a likely paraphyletic genus its exact phylogenetic position is somewhat unclear.

In the collections at the North Dakota Geological Survey there is a relatively complete specimen (NDGS 64) that conforms favorably to Mesocyon temnodon even though some of the diagnostic characters are not visible. It is unusual in that much of the post crania is present, this allows for examination of details not usually possible in this species. This preliminary study is examining several aspects of the paleobiology of this canid.

The first aspect that was studied in detail dealt with the retractability of the claws. This was studied because dogs in the Hesperocyoninae are sometimes described as “cat like” and some of them are hypothesized to have retractable claws. By examining the phalanges of the NDGS 64 specimen, three lines of evidence were tested to determine the retractability of the distal phalanges. The size of the extensor and flexor processes, the depth of arc in the claw, and the morphology of the middle phalanx.  All three of these tests showed the claws to be not retractable.

Studies of its body mass, running speed, bite force, and ecological niche are in progress.