Melillo Stephanie M, Gibert Luis, Saylor Beverly Z, Deino Alan, Alene Mulugeta, Ryan Timothy M, Haile-Selassie Yohannes
Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology Leipzig, Germany.
Departament de Mineralogia, Petrologia i Geologia Aplicada Facultat de Ciències de la Terra, Universitat de Barcelona, Barcelona, Spain.
J Hum Evol. 2021 Apr;153:102956. doi: 10.1016/j.jhevol.2021.102956. Epub 2021 Mar 9.
Fossiliferous deposits at Woranso-Mille span the period when Australopithecus anamensis gave rise to Australopithecus afarensis (3.8-3.6 Ma) and encompass the core of the A. afarensis range (ca. 3.5-3.2 Ma). Within the latter period, fossils described to date include the intriguing but taxonomically unattributed Burtele foot, dentognathic fossils attributed to Australopithecus deyiremeda, and one specimen securely attributed to A. afarensis (the Nefuraytu mandible). These fossils suggest that at least one additional hominin lineage lived alongside A. afarensis in the Afar Depression. Here we describe a collection of hominin fossils from a new locality in the Leado Dido'a area of Woranso-Mille (LDD-VP-1). The strata in this area are correlated to the same chron as those in the Burtele area (C2An.3n; 3.59-3.33 Ma), and similar in age to the Maka Sands and the Basal through lower Sidi Hakoma Members of the Hadar Formation. We attribute all but one of the LDD hominin specimens to A. afarensis, based on diagnostic morphology of the mandible, maxilla, canines, and premolars. The LDD specimens generally fall within the range of variation previously documented for A. afarensis but increase the frequency of some rare morphological variants. However, one isolated M is extremely small, and its taxonomic affinity is currently unknown. The new observations support previous work on temporal trends in A. afarensis and demonstrate that the large range of variation accepted for this species is present even within a limited spatiotemporal range. The value added with this sample lies in its contribution to controlling for spatiotemporal differences among site samples in the A. afarensis hypodigm and its contemporaneity with non-A. afarensis specimens at Woranso-Mille.
沃兰索-米勒的含化石沉积物跨越了南方古猿阿法种从南方古猿湖畔种演化而来的时期(380万-360万年前),并涵盖了阿法种分布范围的核心区域(约350万-320万年前)。在这后一时期内,迄今已描述的化石包括引人关注但分类地位不明的布尔泰尔足化石、归为南方古猿德伊雷梅达种的牙齿颌骨化石,以及一件确凿归为阿法种的标本(内富拉伊图下颌骨)。这些化石表明,在阿法尔洼地至少还有一个人亚族世系与阿法种共同生活。在此,我们描述了一批来自沃兰索-米勒的莱多迪多阿地区一个新地点(LDD-VP-1)的人亚族化石。该地区的地层与布尔泰尔地区的地层属于同一年代(C2An.3n;359万-333万年前),年龄与哈达尔组的马卡砂岩以及从基底到下西迪哈科马段相似。基于下颌骨、上颌骨、犬齿和前磨牙的诊断形态,我们将除一件标本外的所有LDD人亚族标本都归为阿法种。LDD标本总体上落在先前记录的阿法种变异范围内,但增加了一些罕见形态变异的出现频率。然而,有一颗单独的M1极小,其分类归属目前尚不清楚。这些新的观察结果支持了先前关于阿法种时间趋势的研究工作,并表明即使在有限的时空范围内,该物种所公认的广泛变异依然存在。这个样本的价值在于,它有助于控制阿法种标本集中各地点样本之间的时空差异,以及它与沃兰索-米勒的非阿法种标本的同时代性。