Department of Organismal Biology and Anatomy, University of Chicago, Chicago IL, USA; Division of Earth and Ocean Sciences, Nicholas School of the Environment, Duke University, Durham, NC, USA; Department of Biology, Duke University, Durham, NC, USA.
Department of Evolutionary Anthropology, Duke University, Durham, NC, USA; Florida Museum of Natural History, University of Florida, Gainesville, FL, USA.
J Hum Evol. 2020 Jul;144:102786. doi: 10.1016/j.jhevol.2020.102786. Epub 2020 May 11.
Homunculus patagonicus is a stem platyrrhine from the late Early Miocene, high-latitude Santa Cruz Formation, Argentina. Its distribution lies farther south than any extant platyrrhine species. Prior studies on the dietary specialization of Homunculus suggest either a mixed diet of fruit and leaves or a more predominantly fruit-eating diet. To gain further insight into the diet of Homunculus, we examined how the occlusal surfaces of the first and second lower molars of Homunculus change with wear by using three homology-free dental topographic measures: Dirichlet normal energy (DNE), orientation patch count rotated (OPCR), and relief index (RFI). We compared these data with wear series of three extant platyrrhine taxa: the folivorous Alouatta, and the frugivorous Ateles and Callicebus (titi monkeys now in the genus Plecturocebus). Previous studies found Alouatta and Ateles exhibit distinctive patterns of change in occlusal morphology with macrowear, possibly related to the more folivorous diet of the former. Based on previous suggestions that Homunculus was at least partially folivorous, we predicted that changes in dental topographic metrics with wear would follow a pattern more similar to that seen in Alouatta than in Ateles or Callicebus. However, wear-induced changes in Homunculus crown sharpness (DNE) and complexity (OPCR) are more similar to the pattern observed in the frugivorous Ateles and Callicebus. Based on similar wear modalities of the lower molars between Homunculus and Callicebus, we infer that Homunculus had a primarily frugivorous diet. Leaves may have provided an alternative dietary resource to accommodate fluctuation in seasonal fruiting abundance in the high-latitude extratropical environment of late Early Miocene Patagonia.
巴塔哥尼亚霍蒙库鲁斯是一种中始新世晚期、高纬度圣克鲁斯组的原阔鼻猴。其分布范围比任何现存的阔鼻猴物种都更靠南。先前关于霍蒙库鲁斯饮食特化的研究表明，它可能是一种混合了果实和叶子的饮食，或者是一种更主要以果实为食的饮食。为了更深入地了解霍蒙库鲁斯的饮食，我们使用三种无同源性的牙齿拓扑测量方法（Dirichlet 法向能量（DNE）、旋转定向斑块计数（OPCR）和 Relief 指数（RFI））来研究第一和第二下臼齿的咬合面如何随磨损而变化。我们将这些数据与三种现存的阔鼻猴类群的磨损系列进行了比较：食叶的吼猴（Alouatta），以及食果的绒毛猴（Ateles）和白肩长臂猿（Callicebus，现归入 Plecturocebus 属的）。先前的研究发现，吼猴和绒毛猴的咬合形态随宏观磨损而发生明显变化，这可能与前者的食叶性饮食有关。基于先前关于霍蒙库鲁斯至少部分食叶的说法，我们预测，牙齿拓扑学指标随磨损而发生的变化模式将更类似于吼猴，而不是绒毛猴或白肩长臂猿。然而，霍蒙库鲁斯牙齿冠锐利度（DNE）和复杂性（OPCR）随磨损而发生的变化与食果的绒毛猴和白肩长臂猿的观察结果更为相似。基于霍蒙库鲁斯和白肩长臂猿下臼齿类似的磨损方式，我们推断霍蒙库鲁斯主要以水果为食。在中始新世晚期巴塔哥尼亚的高纬度亚热带极端环境中，叶子可能是一种替代的食物资源，以适应季节性果实丰度的波动。
