Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig 04103, Germany.
Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig 04103, Germany.
J Hum Evol. 2018 Jan;114:154-175. doi: 10.1016/j.jhevol.2017.10.012. Epub 2017 Nov 21.
Upper and lower jaws are well represented in the fossil record of mammals and are frequently used to diagnose species. Some hominin species are only known by either their maxillary or mandibular morphology, and in this study, we explore the possibility of predicting their complementary dental arcade shape to aid the recognition of conspecific specimens in the fossil record. To this end, we apply multiple multivariate regression to analyze 3D landmark coordinates collected on associated upper and lower dental arcades of extant Homo, Pan, Gorilla, Pongo, and Hylobates. We first study the extant patterns of variation in dental arcade shape and quantify how accurate predictions of complementary arcades are. Then we explore applications of this extant framework for interpreting the fossil record based on two fossil hominin specimens with associated upper and lower jaws, KNM-WT 15000 (Homo erectus sensu lato) and Sts 52 (Australopithecus africanus), as well as two non-associated specimens of Paranthropus boisei, the maxilla of OH 5 and the Peninj mandible. We find that the shape differences between the predictions and the original fossil specimens are in the range of variation within genera or species and therefore are consistent with their known affinity. Our approach can provide a reference against which intraspecific variation of extinct species can be assessed. We show that our method predicts arcade shapes reliably even if the target shape is not represented in the reference sample. We find that in extant hominoids, the amount of within-taxon variation in dental arcade shape often overlaps with the amount of between-taxon shape variation. This implies that whereas a large difference in dental arcade shape between two individuals typically suggests that they belong to different species or even genera, a small shape difference does not necessarily imply conspecificity.
上下颌在哺乳动物的化石记录中得到了很好的体现，经常被用于诊断物种。一些人属物种仅通过上颌或下颌形态被知晓，在本研究中，我们探索了预测其互补牙弓形状的可能性，以帮助识别化石记录中同种标本。为此，我们应用多元回归分析方法，对现生人类、黑猩猩、大猩猩、猩猩和长臂猿的上颌和下颌牙弓的 3D 标志点坐标进行了分析。我们首先研究了牙弓形状的现生变化模式，并量化了对互补牙弓进行准确预测的可能性。然后，我们基于两个具有相关上下颌的化石人属标本 KNM-WT 15000（广义直立人）和 Sts 52（南方古猿非洲种）以及两个不相关的南方古猿粗壮种标本 OH 5 的上颌和 Peninj 的下颌，探索了这种现生框架在解释化石记录方面的应用。我们发现，预测结果与原始化石标本之间的形状差异在属或种内的变化范围内，因此与它们已知的亲缘关系一致。我们的方法可以为评估灭绝物种的种内变异提供参考。我们表明，即使目标形状不在参考样本中，我们的方法也能可靠地预测牙弓形状。我们发现，在现生人科动物中，牙弓形状的种内变异量通常与种间形状变异量重叠。这意味着两个个体之间牙弓形状的巨大差异通常表明它们属于不同的物种甚至属，而较小的形状差异并不一定意味着它们是同一种。
