Russo Gabrielle A
Department of Anthropology, Stony Brook University, Stony Brook, NY 11794, USA.
J Hum Evol. 2016 Jan;90:135-62. doi: 10.1016/j.jhevol.2015.10.007. Epub 2015 Dec 1.
This study evaluated the relationship between the morphology of the sacrum-the sole bony link between the tail or coccyx and the rest of the body-and tail length (including presence/absence) and function using a comparative sample of extant mammals spanning six orders (Primates, Carnivora, Rodentia, Diprotodontia, Pilosa, Scandentia; N = 472). Phylogenetically-informed regression methods were used to assess how tail length varied with respect to 11 external and internal (i.e., trabecular) bony sacral variables with known or suspected biomechanical significance across all mammals, only primates, and only non-primates. Sacral variables were also evaluated for primates assigned to tail categories ('tailless,' 'nonprehensile short-tailed,' 'nonprehensile long-tailed,' and 'prehensile-tailed'). Compared to primates with reduced tail lengths, primates with longer tails generally exhibited sacra having larger caudal neural openings than cranial neural openings, and last sacral vertebrae with more mediolaterally-expanded caudal articular surfaces than cranial articular surfaces, more laterally-expanded transverse processes, more dorsally-projecting spinous processes, and larger caudal articular surface areas. Observations were corroborated by the comparative sample, which showed that shorter-tailed (e.g., Lynx rufus [bobcat]) and longer-tailed (e.g., Acinonyx jubatus [cheetah]) non-primate mammals morphologically converge with shorter-tailed (e.g., Macaca nemestrina) and longer-tailed (e.g., Macaca fascicularis) primates, respectively. 'Prehensile-tailed' primates exhibited last sacral vertebrae with more laterally-expanded transverse processes and greater caudal articular surface areas than 'nonprehensile long-tailed' primates. Internal sacral variables performed poorly compared to external sacral variables in analyses of extant primates, and were thus deemed less useful for making inferences concerning tail length and function in extinct primates. The tails lengths of five extinct primates were reconstructed from the external sacral variables: Archaeolemur edwardsi had a 'nonprehensile long tail,' Megaladapis grandidieri, Palaeopropithecus kelyus, and Epipliopithecus vindobonensis probably had 'nonprehensile short tails,' and Proconsul heseloni was 'tailless.'
本研究利用涵盖六个目（灵长目、食肉目、啮齿目、双门齿目、披毛目、树鼩目；N = 472）的现存哺乳动物比较样本，评估了骶骨（尾巴或尾骨与身体其他部分之间唯一的骨性连接）形态与尾巴长度（包括有无尾巴）及功能之间的关系。采用系统发育信息回归方法，评估在所有哺乳动物、仅灵长目动物以及仅非灵长目动物中，尾巴长度如何随11个具有已知或疑似生物力学意义的外部和内部（即小梁）骶骨变量而变化。还对被归类为不同尾巴类别的灵长目动物（“无尾”、“非抓握短尾”、“非抓握长尾”和“抓握尾”）的骶骨变量进行了评估。与尾巴长度较短的灵长目动物相比，尾巴较长的灵长目动物通常表现出骶骨的尾侧神经孔比颅侧神经孔大，最后一节骶椎的尾侧关节面比颅侧关节面在内外侧更宽，横突向外侧更宽，棘突向背侧突出，尾侧关节面面积更大。比较样本证实了这些观察结果，该样本表明，尾巴较短的（如加拿大猞猁）和尾巴较长的（如猎豹）非灵长目哺乳动物在形态上分别与尾巴较短的（如明打威猕猴）和尾巴较长的（如食蟹猕猴）灵长目动物趋同。“抓握尾”灵长目动物的最后一节骶椎比“非抓握长尾”灵长目动物的横突向外侧更宽，尾侧关节面面积更大。在现存灵长目动物的分析中，骶骨内部变量与外部变量相比表现不佳，因此被认为在推断已灭绝灵长目动物的尾巴长度和功能方面用处较小。根据外部骶骨变量重建了五种已灭绝灵长目动物的尾巴长度：爱德华古狐猴有一条“非抓握长尾”，格兰迪巨狐猴、凯氏古原狐猴和维也纳上猿可能有“非抓握短尾”，而黑森原康修尔是“无尾”。
