PubMed · 14266896
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M M WEINREB, Y SHARAV. 1964. TOOTH DEVELOPMENT IN SHEEP.. https://pubmed.ncbi.nlm.nih.gov/14266896/
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We have studied the correlation between the level of D-aspartic acid in dentin and the period of dentin formation in different types of teeth from the same individual. Except for the third molar, it is generally agreed that the formation of permanent dentin follows the pattern of growth, occurring earliest in the first molar and last in the second molar. In middle-aged individuals, racemization among the different types of teeth was highest in the first molar, corresponding to the earliest period of dentin formation. In elderly individuals, however, racemization tended to be highest in the second molar, in which dentin is formed last during growth. It is assumed that this may be due to the higher ambient temperature of the second molars, which are located deeper in the oral cavity. Thus, these results suggest that in elderly individuals racemization in teeth that have been situated deep in the oral cavity for a long time is more influenced by the environment than by the period of tooth formation.
In this study, dental development is described in two pairs of closely related catarrhine primate species that differ in their degree of folivory: 1) Hylobates lar and Symphalangus syndactylus, and 2) Papio hamadryas hamadryas and Semnopithecus entellus. Growth increments in histological thin sections are used to reconstruct the chronology of dental development to determine how dental development is accelerated in the more folivorous species of each pair. Although anterior tooth formation appears to be unrelated to diet, both S. syndactylus and S. entellus initiate the slowest-forming molar earlier than the related less-folivorous species, which supports the hypothesis that dental acceleration is related to food processing. S. syndactylus initiates M2 crown formation at an earlier age than H. lar, and S. entellus initiates and completes M3 at an earlier age than P. h. hamadryas. Similar stages of M3 eruption occur earlier in the more folivorous species; however, the sex of the individual may also play a role in creating such differences. Although the age at M3 emergence is close to that reported for the end of body mass growth in lar gibbons, hamadryas baboons, and Hanuman langurs, M3 emergence may not be coupled to body mass growth in siamangs.
Skulls and canines of 460 sea otters from Lopatka Cape, Kamchatka, were examined to assess development patterns, individual variation and sexual differences. An allometric formula was applied to morphometrical data, and the relative growth of each character to total length of skull was analyzed. In both sexes, most morphometrical characters ceased growth at about 2 years of age. Canine root length increased rapidly during the first year of life, while crown length decreased due to remarkable wear. There was large individual variation in the feeding and breathing/sniffing apparatus, while there was little variation in braincase size. There were sexual differences in most characteristics, although males and females showed similar growth patterns. The coronoid process of the mandible showed positive allometry in both sexes, and we attributed this finding to feeding habits. The fact that only male mastoids showed positive allometry may be due to the need for male otters to maintain a passing territory.