Oligoryctes Hough, 1956

ASHER, ROBERT J., McKENNA, MALCOLM C., EMRY, ROBERT J., TABRUM, ALAN R. & KRON, DONALD G., 2002, Morphology And Relationships Of Apternodus And Other Extinct, Zalambdodont, Placental Mammals, Bulletin of the American Museum of Natural History 2002 (273), pp. 1-117 : 58

Oligoryctes Hough, 1956

TYPE SPECIES: Oligoryctes cameronensis

Hough, 1956

INCLUDED SPECIES: O. altitalonidus Clark, 1937 (new combination) and the Tabernacle Butte taxon (unnamed in this paper; see below).

TEMPORAL AND GEOGRAPHIC DISTRIBUTION: Bridgerian (late early Eocene) through Orellan (early Oligocene) throughout the North American western interior, including Wyoming, Montana, Colorado, North Dakota, South Dakota, Saskatchewan, California, Nevada, Utah, Texas, and Nebraska, possibly including Asia if material described by Tong (1997) is included.

DIAGNOSIS: Oligoryctes is a shrew­sized animal with zalambdodont molars, lacking metacones and with reduced talonid basins. The m3 talonid cusp is slightly taller than the m3 paraconid. The upper molars have distinct protocones and anterior cingula, and the posterior two lower incisors are tricuspid. The medial aspect of the coronoid process is deep or pocketed. Oligoryctes has a relatively unspecialized posterior braincase without the elaborate lateral extensions of the squamosal, petromastoid, and occipital that form the lambdoid plates in Apternodus . Instead, Oligoryctes has a laterally rounded squamosal and petromastoid. It shows a prominent entoglenoid process for posterior support of the jaw joint, medial to the postglenoid foramen and anterior to the promontory of the middle ear. The basicranium shows an enlarged foramen ovale and lacks an alisphenoid canal. The squamosal extends posteriorly along the ventrolateral margin of the braincase, lateral to the large piriform fenestra. The anterior exit of the sinus canal and ethmoid foramen are located well anterior to the sphenorbital fissure and are not incorporated into its superior margin. As in Apternodus , the lacrimal foramen is large and laterally oriented.