禄丰古猿牙齿釉质发育不全的观察研究

对出自禄丰石灰坝的26个禄丰古猿下颌齿列的246枚恒齿进行了观察研究,发现禄丰古猿具有普遍的带状釉质发育不全（LEH）现象,个体LEH比例为100%,恒齿LEH比例为85%。乳齿几乎没有LEH现象,第一恒臼齿的LEH比例也很低仅57%。根据牙齿萌出顺序及现代大猿的牙齿发育年龄特征,作者推断2—3岁之前的幼儿古猿很少出现釉质发育不全现象,这可能与母体的营养关照有关。禄丰古猿的LEH的发生频率具有明显的季节性,结合中新世晚期气候变化特征、古猿的生态环境、生活习性及食性特征分析,作者推测：季节性营养不良可能是造成禄丰古猿釉质发育不全的主要原因。     

禄丰古猿前部牙齿的釉面横纹与牙冠形成时间

釉面横纹的数目可用于推断个体牙齿的牙冠形成时间,在生长发育研究中具有重要的意义。本研究运用数码体视显微镜和扫描电镜观察了云南石灰坝禄丰禄丰古猿(简称禄丰古猿)30枚齿冠完整的前部牙齿,包括上下颌中门齿6枚、侧门齿10枚和犬齿14枚。根据唇侧面釉面横纹计数的观察结果,分别以7天和9天芮氏线生长周期,估算各齿型的牙冠形成时间,结果显示:以生长周期7天计算,中门齿牙冠形成时间约为3.6-4.1年,侧门齿牙冠形成时间约为2.7-3.7年,犬齿牙冠形成时间约为4.2-7.0;以生长周期9天计算,中门齿牙冠形成时间约为4.4-5.2年,侧门齿牙冠形成时间约为3.4-4.7年,犬齿牙冠形成时间约为5.2-8.8年。为更深入地了解禄丰古猿牙冠形成时间在不同齿型及性别间足否存在明显差异,本文用SPSS软件对其进行显著性差异检验。采用小样本平均值的t值假设检验(置信区间为95%),结果如下:禄丰古猿前部牙齿的牙冠形成时间在各类牙齿的上下颌中不存在显著性差异;犬齿牙冠形成时间存在非常显著的性别差异,雄性牙冠形成时间明显长于雌性,侧门齿也存在显著的性别差异,而中门齿性别间则无显著性差异。此外对禄丰古猿中门齿,侧门齿和犬齿的牙冠形成时间进行单因素方差分析并两两对比,结果显示中门齿与侧门齿的牙冠形成时间不存在显著性差异,而犬齿与中门齿和侧门齿均存在显著性差异,犬齿牙冠形成时间明显长于门齿。同时也对禄丰古猿前部牙齿的牙冠形成时间与齿冠高进行相关性分析,其结果表明两者有显著的正相关性。将禄丰古猿与其他古猿和现生大猿、南方古猿以及人属成员进行对比,结果显示其前部牙齿牙冠形成时间长于原修康尔猿、南方古猿、傍人、人属成员,接近于蝴蝶禄丰古猿和大猩猩,而明显小于黑猩猩、华南化石猩猩及现生猩猩。     

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。     

禄丰古猿牙齿釉质生长线与个体发育问题研究

运用扫描电子显微镜,对４枚禄丰古猿牙齿（恒齿）釉质结构进行了观察研究,发现：禄丰古猿牙齿釉质表面有明显的釉面横纹结构;釉面横纹的密度向牙颈方向逐渐增大;观察记数了４枚牙齿的釉面横纹数,进而推算出牙冠的形成时间和年龄。与化石人科成员,现代人及现生大猿比较,禄丰古猿牙冠发育模式及时间,与南方古猿纤细种比较接近或相似,明显长于南方古猿粗壮种,有别于现生大猿。     

禄丰古猿(Lufengpithecus lufengensis)牙齿釉质生长线与个体发育问题研究

运用扫描电子显微镜,对4枚禄丰古猿牙齿（恒齿）的釉质结构进行了观察研究。发现：禄丰古猿牙齿釉质表面有明显的釉面横纹结构;釉面横纹的密度向牙颈方向逐渐增大;观察记数了4枚牙齿的釉面横纹数,进而推算出牙冠的形成时间和年龄。与化石人科成员、现代人及现生大猿比较,禄丰古猿牙冠发育模式及时间,与南方古猿纤细种比较接近或相似,明显长于南方古猿粗壮种,有别于现生大猿。     

元谋古猿下颌臼齿三维立体特征

采用欧氏距离矩阵分析（EDMA）方法对72枚元谋古猿及作为对比样本的10枚禄丰古猿、现生大猿类和人类下颌臼齿齿冠13个测量标志点三维测量数据的统计分析显示：元谋古猿在下颌臼齿齿冠三维形态测量特征上与禄丰古猿最为接近。与现生大猿类及人类相比,元谋古猿和禄丰古猿均与人类之间呈现出非常显著的差异,而与猿类较为接近。它们两者及生大猿类均与人类之间具有许多共同的差异表现特点。元谋古猿在下颌臼齿三维测量特征方面与三种现生大猿类各自之间的差别表现相似。其中,元谋古猿与猩猩之间的牙齿形态特征上似乎更为接近。但目前对这些特征相似差异的含义尚难以确定。     

云南禄丰古猿产地的獾类化石

记述了云南禄丰古猿产地的一些獾类化石,主要据其牙齿和下颌特征订为食肉目、鼬科、獾亚科中一个新的属种——禄丰云南獾(Yunnanotherium lufengense gen.et sp.nov.)。从M1的冠面和牙根的特征看,可把宗冠福1991年提出、1997年所订的Trochotherium yuanmouense 1)的1枚M1(另1枚所谓m2经本文作者鉴定不属于这类动物)以及在元谋雷老发现的1枚M1和1枚m2放入这个属中。另外,产自禄丰古猿产地D剖面6层的1枚单个的m1也可归入这个属中。云南獾与欧洲的Trochotherium在牙齿(主要是M1)方面有某种程度的相像(如冠面较平坦、齿尖较低、齿根多),都是一类主要以软体动物为生的食肉动物,但二者之间在牙齿(特别是M1)的结构和下颌形态方面仍有明显的区别。这可能与二者所生长的时代以及生态环境不同有关。     

云南元谋小河地区古猿地点的小型猿类化石

本文记述的云南元谋小河地区古猿地点发现的一种小型猿类。它的牙齿形态比晚中新世的禄丰粗壮池猿进步。而牙齿的某些形态介于粗壮池猿和现生长臂猿之间,它的发现为探讨现生长臂猿的起源与进货提供了新的化石依据。依哺乳动物群的初步研究,其时代稍晚于禄丰古猿地点的时代。鉴于它的形态特征和地史分布,作者将它订为一新属新种：进步滇猿Ｄｉａｎｏ ｐｉｔｈｅｃｕｓ ｐｒｏｇｒｅｓｓｕｓ ｇｅｎ．ｅｔ ｓｐ．ｎｏｖ。     

巫山龙骨坡似人下颌属于猿类

本文将巫山似人下颌及其牙齿与东非早更新世人属 ,Dmanisi直立人以及元谋的禄丰古猿等做了比较。结果发现巫山标本的尺寸比前二者都小得多 ,而与后者很相符。巫山标本被有些人作为归属人属根据的那些特征大多是人和猿共具者 ,其中前臼齿齿根分叉则是在人类罕见 ,却是禄丰古猿的特征之一 ,前臼齿前接触面位置和跟座比例则反映猿类特征。最接近巫山下颌者是禄丰古猿 ,其间有否祖裔关系尚待更多标本来论证。     

消息与动态

从1983年10月中旬到12月中旬,中国科学院古脊椎动物与古人类研究所的禄丰古猿考察队在云南省禄丰县石灰坝村古猿化石地点又一次进行了大规模的发掘,获得了腊玛古猿和西瓦古猿的残缺的颌骨6件,牙齿近百枚。还发现许多“似长臂猿”等灵长类化石及大量的动物化石。 在这次发掘中,我们加强了对小动物化石的重视。用筛洗的办法获得了许多有价值的标本。经初步鉴定,约有30种之多。这对探讨禄丰古猿的地质时代和生活环境无疑地是很有意义的。 此外,我们还对周围地区的地质地貌和一些出露褐煤的地点进行了考察,并讨论了古猿生存时期禄丰地区的沉积环境和气候条件。 (徐庆华)     

Hypothesis for the causes and periodicity of repetitive linear enamel hypoplasia in large, wild African (Pan troglodytes and Gorilla gorilla) and Asian (Pongo pygmaeus) apes

Repetitive linear enamel hypoplasia (rLEH) is often observed in recent large-bodied apes from Africa and Asia as well as Mid- to Late Miocene sites from Spain to China. The ubiquity and periodicity of rLEH are not understood. Its potential as an ontogenetic marker of developmental stress in threatened species (as well as their ancient relatives) makes rLEH an important if enigmatic problem. We report research designed to show the periodicity of rLEH among West African Pan troglodytes (12 male, 32 female), Gorilla gorilla (10 male, 10 female), and Bornean and Sumatran Pongo pygmaeus (11 male, 9 female, 9 unknown) from collections in Europe. Two methods were employed. In the common chimpanzees and gorillas, the space between adjacent, macroscopically visible LEH grooves on teeth with two or more episodes was expressed as an absolute measure and as a ratio of complete unworn crown height. In the orangutans, the number of perikymata between episode onsets, as well as duration of rLEH, was determined from scanning electron micrographs of casts of incisors and canines. We conclude that stress in the form of LEH commences as early as 2.5 years of age in all taxa and lasts for several years, and even longer in orangutans; the stress is not chronic but episodic; the stressor has a strong tendency to occur in pulses of two occurrences each; and large apes from both land masses exhibit rLEH with an average periodicity of 6 months (or multiples thereof; Sumatran orangutans seem to show only annual stress), but this needs further research. This is supported by evidence of spacing between rLEH as well as perikymata counts. Duration of stress in orangutans averages about 6 weeks. Finally, the semiannual stressor transcends geographic and temporal boundaries, and is attributed to regular moisture cycles associated with the intertropical convergence zone modified by the monsoon. While seasonal cycles can influence both disease and nutritional stress, it is likely the combination of seasonal variation in fruiting cycles with specific stressors (malaria and/or intestinal parasites, especially hookworm) that results in this widespread phenomenon. This seasonal stress is sufficiently common and of long duration (6 weeks on average in orangutans) that we think rLEH may reflect significant stress in recent and, inferentially, fossil apes. Increasing seasonality may have impinged negatively on later Miocene apes, especially if they lacked a clear birth peak or seasonality in their reproductive cycles.     

Variation in perikymata counts between repetitive episodes of linear enamel hypoplasia among orangutans from Sumatra and Borneo

The goal of this study is to evaluate whether repetitive linear enamel hypoplasia (rLEH) in apes is ecologically informative. LEH, which appears as grooves of thinner enamel often caused by malnutrition and/or disease, is a permanent record of departures from developmental homeostasis in infant and juvenile apes. Orangutans were selected for the study as they are a threatened species, have a remarkably high prevalence of rLEH, and because Sumatra is deemed a better habitat for orangutans than is Borneo, facilitating an ecological comparison. Objectives are to determine: a) whether periodicity of rLEH in orangutans corresponds to monsoon‐mediated cycles in precipitation or food; and b) whether patterning of rLEH supports the view that Borneo is an inferior habitat. This study compares the counts of perikymata between adjacent LEH from 9 Sumatran and 26 Bornean orangutans to estimate the periodicity of rLEH. A total of 131 nonredundant inter‐LEH perikymata counts were transformed to natural log values to reveal clusters of counts in a multiplicative series. Using a value of 10 days to form one perikyma, rLEH tends to recur semiannually in both populations. However, Sumatran orangutans show significantly fewer semiannual intervals and more annually recurring episodes. Bornean orangutans show mostly semiannual intervals and are more variable in inter‐LEH perikymata counts. It is concluded that: a) developmental conditions for infant orangutans in Sumatra protect them somewhat from seasonal and environmental variation; b) temporal patterning of rLEH indicates that Borneo is the poorer habitat for orangutans; and c) the study of rLEH can be ecologically informative. Am J Phys Anthropol 154:125–139, 2014. © 2014 Wiley Periodicals, Inc.     

Reconstruction of periodicity of repetitive linear enamel hypoplasia from perikymata counts on imbricational enamel among dry‐adapted chimpanzees (Pan troglodytes verus) from Fongoli,Senegal

Periodicity of repetitive linear enamel hypoplasia (rLEH) in apes from high latitudes with single wet and dry seasons annually has not been described. We reconstruct periodicity and duration of rLEH in canine teeth from three recently deceased chimpanzees from Fongoli, Senegal with a marked seven‐month dry season. High‐resolution dental molds were taken in the field for magnified imaging with digital microscopy. Photomontages allowed counting of perikymata between episodes of rLEH for reconstruction of periodicity and duration of physiological stress. Where rLEH spans the imbricational enamel, the number of events is consistent with years required to form canine imbricational enamel; i.e., periodicity of rLEH seems circannual. We predicted perikymata counts between rLEH events ranging from 52 to 61 based on reported “long counts” of 7–6 days. Counts ranged from 29.5 to 44, individual mean of 36.7. This discrepancy could be explained by recurrent stress with a periodicity of 7.2–8.4 months, or by long counts of 10 days per stria. Neither is supported in the literature. Since we find evidence of rLEH with circannual periodicity, we postulate the existence of non‐emergent imbricational striae. Based on evidence that stress at Fongoli recurs annually, we reconstruct stress duration of 2–3 months, longer than reported for chimpanzees living in other habitats, which we attribute to heat stress and food shortage near shrinking waterholes. We conclude that canine teeth from a small mortality cohort of chimpanzees at Fongoli preserve a faithful record of dry season stress in an extreme environment. Am J Phys Anthropol, 2012. © 2012 Wiley Periodicals, Inc.     

Enamel hypoplasias and physiological stress in the Sima de los Huesos Middle Pleistocene hominins

This study presents an analysis of linear enamel hypoplasias (LEH) and plane-form defects (PFD) in the hominine dental sample from the Sima de los Huesos (SH) Middle Pleistocene site in Atapuerca (Spain). The SH sample comprises 475 teeth, 467 permanent and 8 deciduous, belonging to a minimum of 28 individuals. The method for recording PFD and LEH is discussed, as well as the definition of LEH. The prevalence of LEH and PFD in SH permanent dentition (unilateral total count) is 4.6% (13/280). Only one deciduous tooth (lower dc) showed an enamel disruption. Prevalence by individual ranges from 18.7-30%. The most likely explanation for the relatively low LEH and PFD prevalence in the SH sample suggests that the SH population exhibited a low level of developmental stress. The age at occurrence of LEH and PFD was determined by counting the number of perikymata between each lesion and the cervix of the tooth. Assuming a periodicity of nine days for the incremental lines, the majority of LEH in the SH sample occurred during the third year of life and may be related to the metabolic stress associated with weaning.     

Linear enamel hypoplasia in gibbons (Hylobates lar carpenteri)

This study describes the expression of linear enamel hypoplasia (LEH), a sensitive dental indicator of physiological stress, in Thailand gibbons (Hylobates lar carpenteri). Previous studies of enamel hypoplasia in hominoids have focused on great apes, with little attention given to the expression of this stress indicator in gibbons. In that gibbons differ from both monkeys and great apes in numerous life history features, LEH expression in gibbons might be expected to show significant differences from both. In this study, 92 gibbon specimens from two sites in Thailand were compared with several samples of monkeys and great apes in their expression of LEH. The intertooth distribution of LEH in gibbons was compared to that of chimpanzees and rhesus monkeys. Gibbon populations from both sites exhibit LEH frequencies intermediate between those of the monkey samples, in which LEH prevalence is usually low, and those of the great ape samples, in which LEH prevalence is high. Gibbons differ significantly from monkeys, but not great apes, in the number of individuals whose teeth record multiple stress events. Multiple episodes of stress are rarely recorded in the teeth of monkeys, while multiple stress events occur with higher frequency in gibbons and great apes. Taxonomic variation in the duration of crown formation, the prominence and spacing of perikymata on dental crowns, life history features, and/or experience of physiological stress may explain these patterns. The intertooth distribution of LEH in gibbons is, for different reasons, unlike that of either chimpanzees or rhesus monkeys. The mandibular canines of gibbons have significantly more LEH than any of their other teeth. Aspects of crown morphology, perikymata prominence/spacing, enamel thickness, and crown formation spans are potential causes of taxonomic variation in the intertooth distribution of LEH.     

Age at first molar emergence in Lufengpithecus lufengensis and its implications for life-history evolution

The late Miocene hominoid Lufengpithecus from Yunnan Province, China, is crucial for understanding hominoid evolution in Asia. Given that age at first permanent molar emergence is a key life-history trait in primates, the present study determined the age at death of the Lufengpithecus lufengensis juvenile PA868, which was in the process of erupting its first molar. Using a perikymata periodicity of 7-11 days, along with estimation of cusp formation time and the postnatal delay of crown mineralization, perikymata counts obtained from the permanent central incisor and canine germs indicate that the age at death of PA868 was 2.4-4.5 years based on the central incisor germ, and 2.5-4.7 years based on the canine germ. The age at the first molar emergence was actually slightly younger (by about 0.3 years), as demonstrated by tiny wear facets on this tooth, which indicate that gingival emergence had occurred sometime before death. The average age at first molar emergence of Lufengpithecus lufengensis PA868 is estimated to be 3.2-3.3 years, with a range of 2.1-4.4 years. In comparison to extant primates and other fossil hominoids, the life history of Lufengpithecus lufengensis is similar to that of extant great apes and the Miocene hominoids Afropithecus turkanensis and Sivapithecus parvada, as well as Plio-Pleistocene Australopithecus, and different from monkeys, gibbons, and modern humans.