Functional Correlates of Fiber Architecture of the Lateral Caudal Musculature in Prehensile and Nonprehensile Tails of the Platyrrhini (Primates) and Procyonidae (Carnivora)

Abstract

Prehensile-tailed platyrrhines (atelines and Cebus) and procyonids (Potos) display bony tail features that have been functionally and adaptively linked to their prehensile behaviors, particularly the need to resist relatively greater bending and torsional stresses associated with supporting their body weight during suspensory postures. We compared fiber architecture of the mm. intertransversarii caudae (ITC), the prime tail lateral flexors/rotators, in 40 individuals distributed across 8 platyrrhine and 2 procyonid genera, divided into one of two groups: prehensile or nonprehensile. We tested the hypothesis that prehensile-tailed taxa exhibit relatively greater physiologic cross-sectional areas (PCSAs) to maintain tail suspensory postures for extended periods. As an architectural tradeoff of maximizing force, we also predicted prehensile-tailed taxa would exhibit relatively shorter, more pinnate fibers, and a lower mass to tetanic tension ratio (Mass/P O ). Prehensile-tailed taxa have relatively higher PCSAs in all tail regions, indicating their capacity to generate relatively greater maximum muscle forces compared to nonprehensile-tailed taxa. Contrary to our predictions, there are no group differences in pinnation angles, fiber lengths or M/P O ratios. Therefore, the relatively greater prehensile PCSAs are driven largely by relative increase in muscle mass. These findings suggest that relatively greater ITC PCSAs can be functionally linked to the need for prehensile-tailed taxa to suspend and support their body weight during arboreal behaviors. Moreover, maximizing ITC force production may not come at the expense of muscle excursion/ contraction velocity. One advantage of this architectural configuration is it facilitates suspension of the body while simultaneously maximizing tail contact with the substrate. Anat Rec, 292:827-841, 2009.

Anatomical adaptations of the hind limb musculature of tree-kangaroos for arboreal locomotion (Marsupialia : Macropodinae)

“…binturong (Arctictis binturong) and koala (Phascolarctos cinereus), tend to move relatively slowly and deliberately, and employ prehensile digits and/or large, grasping claws to provide increased resistance to slipping and to help maintain contact with the substrate (Dublin 1903;Cartmill 1979;Grand 1990a;Argot 2001). A long, muscular, nonprehensile tail may be employed as a counter balance; or a prehensile tail may function as a grasping organ (Organ, Teaford et al 2009;Organ 2010). On the whole, climbers are less muscular than runners, reflecting the reduced value of propulsive force as a function of branch compliance (Grand 1983;Grand 1990b).…”

Tail growth tracks the ontogeny of prehensile tail use in capuchin monkeys (Cebus albifronsandC. apella)

“…transitional 1 1/2 no. distal caudal vertebrae; Organ et al, 2009). Organ (2010) demonstrated that relative to craniocaudal vertebral length, the caudal vertebrae of prehensile-tailed taxa generally exhibit greater bending strength than those of nonprehensile-tailed taxa, across vertebral levels.…”

“…However, among primates, prehensile tails characterize just five genera belonging to two platyrrhine clades: Alouatta, Ateles, Brachyteles, Lagothrix (Atelidae), and Cebus (Cebinae) (Groves, 2001(Groves, , 2005 Ryland and Mittermeier, 2009; see also Rosenberger and Matthews, 2008). Thus, for more than 70 years, researchers have devoted considerable attention to primate prehensile tail structure (e.g., Dor, 1937;Hill, 1960Hill, , 1962Ankel, 1962Ankel, , 1965Ankel, , 1972German, 1982;Rosenberger, 1983;Lemelin, 1995;Youlatos, 2003;Schmitt et al, 2005;Organ, 2006Organ, , 2007Organ, , 2010Organ et al, 2009Organ et al, , 2011 and function (e.g., Rose, 1974;Emmons and Gentry, 1983;Cant, 1986;Fontaine, 1990Fontaine, , 1994Bergeson, 1992Bergeson, , 1995Bergeson, , 1996Gebo, 1992;Meldrum, 1998;Garber and Rehg, 1999;Turnquist et al, 1999;Youlatos, 1999Youlatos, , 2003Lawler and Stamps, 2002;Bezanson, 2004Bezanson, , 2005Bezanson, , 2006Bezanson, , 2009Schmitt et al, 2005;Middleton et al, 2011).The primate tail can be divided into three regions based on external caudal vertebral morphology: proximal, transitional, and distal ( …”

The Tail of Tyrannosaurus: Reassessing the Size and Locomotive Importance of the M. caudofemoralis in Non‐Avian Theropods

“…The associations between muscle mass, vertebrae morphology, and function have been well studied in the tails of extant mammals, particularly procyonids and primates, and tail biomechanics are better understood among mammals than any other group of terrestrial vertebrates (Dor, 1937;German, 1982;Lemelin, 1995;Organ et al, 2009). However, in terms of mass and volume, most fully terrestrial mammals have unimpressive tails.…”