Data are presented on anomalies of the skull based on examination of 260 skulls of Ovis canadensis nelsoni from the Desert Game Range in southern Nevada. Variations in the dentition are common, especially the absence of second pre-molars in adults. Approximately 7.4 per cent of the rams and 34.3 per cent of the ewes examined had one or more missing second pre-molars. This condition is more common in the lower jaw. A significant deflection of the occipital region from the anterioposterior axis was found in rams. In addition certain minor anomalies were found. The incidence of dental and other anomalies is believed to be higher than that normally found in other mammalian populations. Additional studies were made of anomalies of the skull in desert bighorn sheep, Ovis canadensis nelsoni, based on a collection of 260 skulls from the Desert Game Range of southern Nevada on deposit at the Biology Museum, Nevada Southern University. Reports by Hansen (1961), Kiger (1963), Allred and Bradley (1965), and Baker and Bradley (1965) are based on this collection which is especially valuable since it represents the largest sample of skulls from any population of bighorn sheep in North America. The present study is a re-evaluation and continuation of the study made by Allred and Bradley (1965) based on a larger sample with a more adequate representation of age groups, especially of lamb skulls. We wish to express our appreciation to Mr. Baine Cater, Refuge Manager, and Dr. Charles G. Hansen, Wildlife Biologist, for permission to move the collection to the Biology Museum for a more thorough study. Dr. James E. Deacon critically reviewed the manuscript.
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