Orbit orientation in primates has been linked to adaptive factors related to activity pattern and size‐related variation in structural influences on orbit position. Although differences in circumorbital form between anthropoids and strepsirrhines appear to be related to interspecific disparities in levels of orbital convergence and orbital frontation, there is considerable overlap in convergence between suborders. Unfortunately, putative links between convergence and frontation across primates, and consequent arguments about primate and anthropoid origins, are likely to be influenced by allometry, the size range of a respective sample, and adaptive influences on encephalization and activity patterns. Such a multifarious system is less amenable to interspecific treatment across higher‐level clades. An ontogenetic perspective is one way to evaluate transformations from one character state to another, especially as they pertain to allometric effects on phenotypic variation. We characterized the ontogeny of orbital convergence and frontation in 13 anthropoid and strepsirrhine species. In each suborder, correlation and regression analyses were used to test hypotheses regarding the allometric bases of variation in orbital orientation. Growth trajectories were analyzed intra‐ and inter‐specifically. Frontation decreased postnatally in all taxa due to the negative scaling of brain vs. skull size. Further, interspecific variation in relative levels of frontation was linked to corresponding ontogenetic transpositions in encephalization that differed within both suborders. In strepsirrhines, postnatal increases in convergence were largely due to the negative allometry of orbit vs. skull size. In contrast, convergence in anthropoids varied little during growth, being unrelated to ontogenetic variation in either relative orbit or interorbit size. Anat Rec, 302:2093–2104, 2019. © 2019 American Association for Anatomy
Pelvic form is hypothesized to reflect locomotor adaptation in anthropoids. Most observed variation is found in the ilium, which traditionally is thought to reflect thoracic and shoulder morphology. This article examines the articulated bony pelvis of anthropoids in three dimensions (3D) to test hypothesized variation in pelvic anatomy related to overall torso form.
Sixty landmarks were collected on articulated pelves from 240 anthropoid individuals. Landmark data were subjected to a Generalized Procrustes Analysis. Principal Components Analysis was used to identify trends among taxa. Linear metrics were extracted, and bivariate allometric analysis was used to compare intergroup differences and scaling trends of specific dimensions.
The combination of 3D and bivariate allometric analysis demonstrates a complex pattern of locomotor/phylogenetic and allometric influences on pelvic morphology. Apes have relatively narrower dorsal interiliac spacing than do most monkeys, with relatively smaller spinal muscle attachment areas but only minimally wider ventral bi‐iliac breadths. Hylobatids and atelids have a relatively more cranial position of their sacra than do other taxa, and hylobatids and cercopithecids relatively more retroflexed ischia. Within groups, the three pelvic joints (lumbosacral, sacroiliac, and hip) become relatively closer together with increasing body size.
A three‐dimensional consideration of the articulated pelvis in anthropoids reveals determinants of pelvic variation not previously appreciated by studies of isolated hipbones. This study provides no support for the hypothesis that the ape pelvis is mediolaterally broader than that of monkeys in relative terms, as would be expected if iliac shape is related to hypothesized differences in thoracic breadth and shoulder orientation. Instead, apes, especially great apes, have relatively narrow sacra and longer lower pelves, related to their shorter, stiffer lumbar spines and torsos. This difference, coupled with strong positive allometry of iliac breadth and negative allometry of key pelvic lengths, along with some variation in ischial morphology in certain taxa, explains much of the variation in pelvic form among anthropoid primates.
- PAR ID:
- 10051253
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- American Journal of Physical Anthropology
- Volume:
- 166
- Issue:
- 1
- ISSN:
- 0002-9483
- Page Range / eLocation ID:
- p. 3-25
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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