Department of Pathology and Anatomical Sciences, University of Missouri, Columbia, MO 65212, USA.
J Hum Evol. 2012 Jul;63(1):1-51. doi: 10.1016/j.jhevol.2011.11.012. Epub 2012 May 30.
Renewed fieldwork at Hadar, Ethiopia, from 1990 to 2007, by a team based at the Institute of Human Origins, Arizona State University, resulted in the recovery of 49 new postcranial fossils attributed to Australopithecus afarensis. These fossils include elements from both the upper and lower limbs as well as the axial skeleton, and increase the sample size of previously known elements for A. afarensis. The expanded Hadar sample provides evidence of multiple new individuals that are intermediate in size between the smallest and largest individuals previously documented, and so support the hypothesis that a single dimorphic species is represented. Consideration of the functional anatomy of the new fossils supports the hypothesis that no functional or behavioral differences need to be invoked to explain the morphological variation between large and small A. afarensis individuals. Several specimens provide important new data about this species, including new vertebrae supporting the hypothesis that A. afarensis may have had a more human-like thoracic form than previously appreciated, with an invaginated thoracic vertebral column. A distal pollical phalanx confirms the presence of a human-like flexor pollicis longus muscle in A. afarensis. The new fossils include the first complete fourth metatarsal known for A. afarensis. This specimen exhibits the dorsoplantarly expanded base, axial torsion and domed head typical of humans, revealing the presence of human-like permanent longitudinal and transverse arches and extension of the metatarsophalangeal joints as in human-like heel-off during gait. The new Hadar postcranial fossils provide a more complete picture of postcranial functional anatomy, and individual and temporal variation within this sample. They provide the basis for further in-depth analyses of the behavioral and evolutionary significance of A. afarensis anatomy, and greater insight into the biology and evolution of these early hominins.
哈达尔的野外工作从 1990 年持续到 2007 年，由亚利桑那州立大学人类起源研究所的一个团队负责，在此期间共发现了 49 具新的属于南方古猿阿法种的后肢骨骼化石。这些化石包括上下肢骨骼以及中轴骨骼，增加了此前已知的阿法南方古猿化石的样本量。扩展后的哈达尔样本提供了多个新个体的证据，这些新个体的体型大小处于此前记录的最小和最大个体之间，因此支持了单一的二型物种的假说。对新化石的功能解剖学的考虑支持了这样一种假说，即不需要引入任何功能或行为上的差异来解释大小阿法南方古猿个体之间的形态变化。一些标本提供了关于这个物种的重要新数据，包括新的脊椎骨，支持了阿法南方古猿可能具有比以前认为的更类似人类的胸廓形态的假说，具有内陷的胸腰椎柱。一个远端拇指掌骨提供了阿法南方古猿存在类似人类的屈拇长肌的重要新数据。新的化石包括第一个已知的完整的第四跖骨，它具有类似人类的跖骨基底部的背侧-跖侧扩张、轴向扭转和穹顶状的头部，这表明存在类似人类的永久性纵向和横向足弓，以及在行走时类似人类的跟骨离地的跖趾关节的伸展。哈达尔的新后肢骨骼化石提供了一个更完整的后肢功能解剖学的图像，以及这个样本中个体和时间的变化。它们为进一步深入分析阿法南方古猿解剖结构的行为和进化意义提供了基础，并为这些早期人类的生物学和进化提供了更深入的了解。
