NEW SPECIES OF BATODONOIDES (LIPOTYPHLA, GEOLABIDIDAE) FROM THE EARLYEOCENE OF WYOMING - SMALLEST KNOWN MAMMAL

A new early Eocene insectivore, Batodonoides vanhouteni, sp. nov., has molar teeth indicating a body size smaller than that of any mammal kn own to date. B. vanhouteni is the oldest known species assigned to the genus, which was known previously from the middle Eocene of Californi a. The type, all associated maxilla and mandible, preserves P2-M2 and c1-p2, dp4, p4-m3, with alveoli for i1-3. Some teeth (P4, c1, and p4) are still erupting, indicating that the specimen is a juvenile at abou t the age of dispersal. B. vanhouteni had two sets of functional teeth , unlike extant mammals of very small size. it retains the primitive p attern of cheek-tooth replacement, erupting P3 before P4, unlike the P 4-before-P3 sequence of almost all Lipotyphla. The distribution of bod y masses for Clarkforkian and Wasatchian insectivores indicates that l ate Paleocene and early Eocene lipotyphlans occupied a lower range of body masses (ca. 1.3-53 g) compared to extant Lipotyphla (ca. 2.5-1,10 0 g); the upper range of insectivore body masses was occupied by now-e xtinct ''Proteutheria.''