. Biology of the Heteromyidae. Heteromyidae. prs 1 rnm hysd prsd hyd 1 I prd. end mtd Fig. 5. —Heteromyid crown pattern in Perog- nathusparvus, AMNH 33504. Ironside, Malheur Co., Oregon; Recent. 5 A. Upper right cheek teeth. 5B. Lower left cheek teeth. Blackened wear sur- faces tilt toward bottom of page, white toward top. Anterior is to the right. See Fig. 4 for ab- breviations. wear. The absence of lingual facets suggests that neither upper nor lower teeth were wid- ened by styles. Jimomys may be a geomyoid more primitive than any heteromyid or geo- myid. Most authors subscribe to the hypoth
. Biology of the Heteromyidae. Heteromyidae. prs 1 rnm hysd prsd hyd 1 I prd. end mtd Fig. 5. —Heteromyid crown pattern in Perog- nathusparvus, AMNH 33504. Ironside, Malheur Co., Oregon; Recent. 5 A. Upper right cheek teeth. 5B. Lower left cheek teeth. Blackened wear sur- faces tilt toward bottom of page, white toward top. Anterior is to the right. See Fig. 4 for ab- breviations. wear. The absence of lingual facets suggests that neither upper nor lower teeth were wid- ened by styles. Jimomys may be a geomyoid more primitive than any heteromyid or geo- myid. Most authors subscribe to the hypothesis that eomyoids and geomyoids are descend- ed from sciuravids. Transverse lophs and rectangular cheek tooth shape are the chief features of dental similarity. Dawson (1968) figured several different members of the Sci- uravidae from the middle Eocene. Wood (1935^:82-83) did not assign Hel- iscomys to a heteromyid subfamily: "Genus incertae sedis, perhaps ancestral to all three subfamilies, with characters common to all. Perhaps nearest to the ; He emphasized dental primitiveness of the ge- nus and stated that ""Heliscomys, as far as its dental development is concerned, is structurally ancestral to the ; Wood (1939) described new specimens and questioned his earlier view that the 3-cusped. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Brown, James H; Genoways, Hugh H. [Stillwater, Okla. ?] : American Society of Mammalogists
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