Surfaces Of Incisor Teeth Research Articles

A record of hibernation on the surface of incisor teeth in the hamster Mesocricetus raddei (Nehring, 1894)

The surface of the lower incisor teeth was studied in an adult male Mesocricetus raddei hamster with a temperature logger implanted into its peritoneal cavity in June 2010. From July 2010 to March 2011, the hamster lived under natural conditions in an enclosure and overwintered in a self-made burrow. Logger data showed that, beginning from mid-August, the animal body temperature periodically dropped and then returned to the norm, with the duration and depth of hypothermia (torpor bouts) increasing and those of nor-mothermia (arousals) decreasing with time. Growth increments on the incisor surface (presumably, daily increments) were unclear in the apical and middle tooth parts but very distinct in the basal part. The number and width of basal increments generally corresponded to the number and duration of arousals. The growth of the incisors apparently continued throughout the winter season, with every arousal after a torpor bout being marked by the formation of a distinct increment on the incisor surface. Thus, it appears that the pattern of increments on the incisor surface can be used to evaluate the course of wintering in hibernating hamsters. Experiments with vital markers are needed to confirm this assumption.

The dental developmental status of six East African juvenile fossil hominids

Radiographs of five juvenile fossil hominids from Koobi Fora, Kenya are described and presented together with measurements and observations made on the original speciments. Data are also presented for a single specimen from Olduvai Gorge, Tanzania. Four of these specimens are attributed to Paranthropus boisei (KNM ER 812, 1477 1820 and OH 30), and are all of remarkably similar dental developmental status. Conventional age estimates for these specimens of Paranthropus based on the first permanent molar, indicate an age at death of around 2·2 to 3 years. Perikymata counts on permanent lower central incisors of these specimens also indicate an age at death between 2·5 and 3 years. Two specimens attributed to early Homo (KNM ER 820 and 1507), are dentally more mature than specimens of Paranthropus boisei described here being closer to 5 years of age. Differences between the spacing and distribution of perikymata on the surfaces of incisor teeth are now apparent between Homo, Australopithecus. Paranthropus boisei and Paranthropus robustus: these are described in this paper. Details of the dental developmental patterns of these hominids are also discussed in the light of recent publications that have presented data about hominid eruption sequences and fossil hominid growth periods.