Abstract
Serial sections of the oral lips and angle of rodents representing 10 families, 47 genera and 79 species were studied microscopically, and the occurrence and relative amounts of sebaceous, apocrine sudoriferous and mucous glands described. These closely adjacent glands differ in their taxonomic correlations, amount of individual variation and evolutionary trends within rodents. Oral sebaceous glands are ubiquitous in the haired areas, but show specialized enlargement in diverse rodent groups, especially in Aplodontiidae, Heteromyidae, Zapodidae, Dipodidae and in some genera and species of Cricetidae and Muridae. Oral apocrine sudoriferous glands, large and active in Spermophilus, are reduced, vestigial or lacking in other sciurids, microtines and North American cricetines. Other rodent groups ( Bathyergidae, Capromyidae, Aplodontiidae, Heteromyidae, Geomyidae, Old World cricetines, Gerbillinae, Muridae, Zapodidae and Dipodidae), representatives of which were examined, lack traces of these glands. Different compound tubular and tubulo-alveolar mucous and mixed sero-mucous glands extend into the angle and lip area in different rodent groups, and without obvious relations in regard to the quantitative development of the other gland types in the region. Variation and possible functional and evolutionary attributes of the glands are discussed.