华南化石猩猩前部牙齿釉面横纹与牙冠形成时间研究

釉面横纹的分布与数目可以反映牙齿生长发育的时间和速率变化, 在化石研究中能为复原个体生活史提供重要依据。本研究运用扫描电子显微镜观察华南化石猩猩门齿、犬齿釉面横纹分布与数目, 并估算门齿和犬齿牙冠形成时间, 结果如下: 牙冠从牙尖至牙颈方向釉面横纹分布密度有疏密变化, 牙尖釉面横纹密度小于10条/mm, 中间至牙颈釉面横纹密度较尖部增大, 大约10-15条/mm; 犬齿釉面横纹数目多于门齿, 雄性犬齿釉面横纹数目多于雌性; 根据釉面横纹计数及其生长周期的组织切片观察结果, 估算门齿牙冠形成时间大约为2.97-6.66年, 犬齿雄性长于雌性, 分别为6.25-11.31年和4.28-7.29年。与一些古猿、早期人类、现代人以及现生大猿比较, 华南化石猩猩釉面横纹整体密度稍大于南方古猿和傍人, 小于黑猩猩、大猩猩、现代人和禄丰古猿; 除侧门齿外, 华南化石猩猩釉面横纹数目明显多于南方古猿、傍人和现代人, 与大猩猩接近; 华南猩猩前部牙齿牙冠形成时间与现生大猿、禄丰古猿差别不大, 与现生猩猩最相近, 长于南方古猿和傍人。

Perikymata and Crown Formation Time of Anterior Teeth of Fossil Orangutan from South China

Perikymata are typical enamel growth markings of anterior teeth, and their spacing pattern and total counts can provide helpful information on dental development and life history. In the present study, we observed and analyzed perikymata spacing pattern and counts of anterior teeth of fossil orangutans from South China by scanning electron microscopy, and estimated crown formation times of incisors and canines. By dividing tooth crown into three equal parts: cuspal, middle and cervical, the density of perikymata in cuspal third is lower than 10/mm, and there? is? no? significant? difference? between? the? middle? and? cervical? third,? counting? about? 10-15/ mm. Total numbers of perikymata counts are more in the upper central incisor than in the upper lateral incisor, more in canines than in incisors, and more in male canines than in female canines. Referring to the cuspal enamel formation time of anterior teeth in extant apes, we estimated that these formation times in incisors and canines of fossil orangutans were 0.5 year and 1.0 year, respectively. Lateral enamel formation time equals perikymata counts multiplied by nine- day periodicity of the Retzius line (which is very popular in our section analysis on molars). According to cuspal and lateral enamel formation times, we estimated that the incisor crown formation time was about 2.97-6.66 years. Canine crown formation times of male orangutans from South China were longer than that of females, and estimated between 6.25-11.31 years and 4.28-7.29 years, respectively.
Compared with some fossil large apes, Australopithecus and Paranthropus, early Homo, Homo sapiens and extant apes, perikymata spacing of anterior teeth of orangutans from South China is more dense than that of Australopithecus and Paranthropus, and less than that of African apes, Homo sapiens and Lufengpithecus lufengensis. Except for the upper lateral incisor, perikymata counts of anterior teeth of fossil orangutan are similar to extant great apes, and greater than Australopithecus, Paranthropus, and early Homo. Crown formation times of these orangutan teeth was much longer than Proconsul, Australopithecus and Paranthropus, and closer to extant African apes, Lufengpithecus lufengensis and modern orangutan, especially.