Middle Pleistocene Hominin Teeth from Longtan Cave, Hexian, China

Abstract

Excavations at the Longtan Cave, Hexian, Anhui Province of Eastern China, have yielded several hominin fossils including crania, mandibular fragments, and teeth currently dated to 412±25 ka. While previous studies have focused on the cranial remains, there are no detailed analyses of the dental evidence. In this study, we provide metric and morphological descriptions and comparisons of ten teeth recovered from Hexian, including microcomputed tomography analyses. Our results indicate that the Hexian teeth are metrically and morphologically primitive and overlap with H. ergaster and East Asian Early and mid-Middle Pleistocene hominins in their large dimensions and occlusal complexities. However, the Hexian teeth differ from H. ergaster in features such as conspicuous vertical grooves on the labial/buccal surfaces of the central incisor and the upper premolar, the crown outline shapes of upper and lower molars and the numbers, shapes, and divergences of the roots. Despite their close geological ages, the Hexian teeth are also more primitive than Zhoukoudian specimens, and resemble Sangiran Early Pleistocene teeth. In addition, no typical Neanderthal features have been identified in the Hexian sample. Our study highlights the metrical and morphological primitive status of the Hexian sample in comparison to contemporaneous or even earlier populations of Asia. Based on this finding, we suggest that the primitive-derived gradients of the Asian hominins cannot be satisfactorily fitted along a chronological sequence, suggesting complex evolutionary scenarios with the coexistence and/or survival of different lineages in Eurasia. Hexian could represent the persistence in time of a H. erectus group that would have retained primitive features that were lost in other Asian populations such as Zhoukoudian or Panxian Dadong. Our study expands the metrical and morphological variations known for the East Asian hominins before the mid-Middle Pleistocene and warns about the possibility that the Asian hominin variability may have been taxonomically oversimplified.

Micro‐CT Imaging and Analysis of Enamel Defects on the Early Late Pleistocene Xujiayao Juvenile

“…The fact that the depression was also present at the EDJ indicates that during development, the enamel epithelium folded in this region. Such folding on the I 1 is consistent with the many wrinkles present on the lingual surface of the I 1 (Xing et al, , ). The apparent ‘vertical hypoplasia’ is therefore most likely simply a feature of the crown.…”

Late Pleistocene hominin teeth from Laoya Cave, southern China

“…Additionally, extra cusps like C6 and/or C7 are present in the M 3 s of the Daoxian Fuyan and Huanglong caves (Liu et al, 2010b. The MTC, which is highly rare in East Asian Middle Pleistocene fossil hominins (see Xing et al, 2014;Liu et al, 2017) and absent from all the specimens of East Asian fossil H. sapiens, appears in LYC1. A high and continuous MTC of the lower molar is frequently found in specimens of Neanderthal lineage (Bailey et al, 2011;Martínez de Pinillos et al, 2014).…”

“…The 'X' pattern, as in LYC1, did not become very common until relatively recently (Martinón-Torres et al, 2012;Xing et al, 2014). Only 4 out of 12 specimens of Early/Middle Pleistocene East Asian hominins exhibit the 'X' pattern.…”

Digital enhancement of dental enamel microstructure images from intact teeth

“…Dental enamel is one of the most abundant and best-preserved tissues in fossil specimens. (Alba, Fortuny, & Moya-Sola, 2010;Hlusko et al, 2013;Leece et al, 2016;Xing et al;. Line and Bergqvist (2005) analyzed the structure of HSBs in enamel of intact mammalian teeth dating of approximately 60 million years.…”