Bessoecetor Bisonalveus Buxolestes Palaeosinopa Pantolestes Pentacodon Dyspterna Pantolestidae is an extinct family of semi-aquatic, non-placental eutherian mammals.

The anatomy of these archaic "insectivorous" mammals is best known through well-preserved Middle Eocene Buxolestes specimens found at Messel in Germany and a few other less complete specimens,[2] such as the Palaeosinopa found at Fossil Butte in Wyoming, estimated to have reached body weights of up to 1,400 grams (3 lb), making them relatively large early mammals.

[1] Freely articulated forearm bones (radius and ulna) permitted their powerful forelimbs wide rotational movements, while their digits had large bony claws —indicating they could dig and build underground dens.

[1] The youngest pantolestids known are Gobiopithecus khan and Kiinkerishella zaisanica from the Ergilian deposits of Khoer Dzan, Mongolia.

These late Asian forms are thought to be one of the few examples of European mammals dispersing into Asia during the Grande Coupure.