Browsing by Author "Sarmiento, Esteban E."
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Item The Cross River gorillas : a distinct subspecies, Gorilla gorilla diehli Matschie 1904. American Museum novitates ; no. 3304(New York, NY : American Museum of Natural History, 2000) Sarmiento, Esteban E.; Oates, John F., 1944-This study presents the results of a new set of measurements made on museum specimens of gorilla skeletons from the Cross River headwaters. It provides a review of the taxonomy of Cross River gorillas and describes their distribution and related aspects of their natural history. Considering their distinctiveness and geographic isolation, Cross River gorillas are best regarded as a distinct subspecies, G.g. diehli. Compared to other western gorilla populations, Cross River gorillas have smaller dentitions, smaller palates, smaller cranial vaults, and shorter skulls. Although Cross River gorillas do not seem to differ from other western gorillas in either body size or limb long bone lengths, measurements from a single male suggest that they may have shorter hands and feet and a larger opposability index than other western gorillas. Marked variation in the habitats of Cross River gorillas and insufficient data on behavior frustrate attempts to directly associate morphology with ecology. Many of their distinguishing characters, however, are parts of an adaptive complex that in most primates is characteristic of increasing terrestriality. A subspecific designation for Cross River gorillas correlates with other biogeographic patterns, since many primate species and subspecies inhabiting the Cross River area are distinct from their counterparts further south where other western gorillas occur.Item External and middle ear characteristics of primates, with reference to tarsier-anthropoid affinities. American Museum novitates ; no. 2787(New York, N.Y. : American Museum of Natural History, 1984) Packer, David J.; Sarmiento, Esteban E."Otic anatomy has been used to propose two different hypotheses about tarsier-anthropoid affinities: (1) Tarsius and Anthropoidea evolved independently from Paleogene omomyid tarsioids, and (2) Tarsius (or Tarsiidae) and Anthropoidea are phyletic sister groups. The arrangement of otic structures into form-function complexes of the middle and external ear is essential for phylogenetic analysis. Although the middle ear cavities in anthropoids contain mastoid cells not present in Tarsius, the two taxa share tympanic and anterior accessory cavities in a dual cavity-septum configuration. The resonant effects of the two coupled volumes are closely similar in Saimiri and Tarsius despite marked differences in the position of the septum and aditus, suggesting that their middle ear morphology is convergent. Although the intrapetrosal pathway of the internal carotid artery has been described as 'perbullar' in both anthropoids and Tarsius, the artery crosses part of the tympanic cavity (promontory) in platyrrhines but not in Tarsius. Furthermore, a branch of the tympanic nerve passes through the carotid foramen in at least some anthropoids but not the anterolaterally-shifted carotid foramen of Tarsius. The emergence of the internal carotid nerve onto the external aspect of the promontorial canal in tupaiids and probably Rooneyia viejaensis supports Szalay's (1975a) contention that a large promontorial artery links omomyids with living haplorhines. The bony external meatal tube is an adaptation designed to reduce physiological noise in species where the jaw joint borders directly on the external ear. Since the bony meatal tube is characteristic of the rounded and clinocranial skull of Tarsius, the skull of the earliest anthropoids probably did not closely resemble those of Tarsius or Paleogene forms currently recognized as 'tarsioid'"--P. [1].Item Generalized quadrupeds, committed bipeds, and the shift to open habitats : an evolutionary model of hominid divergence. American Museum novitates ; no. 3250(New York, NY : American Museum of Natural History, 1998) Sarmiento, Esteban E."Proposed models of hominid divergence and the currently accepted hominoid phylogeny fail to account for the distinguishing human characters that led anatomists to hypothesize a prepongid or prehominoid divergence of hominids. Because humans share a cautious climbing ancestry with other hominoids, similarities in the anatomy and proportions of the human musculoskeletal structure with those of gorillas and cursorial cercopithecids suggest that hominids underwent selection for terrestrial quadrupedality after their divergence from a common semiarboreal hominoid ancestor. Selection for terrestrial quadrupedality explains generalized monkeylike characters in humans, reconciling anatomical evidence with the currently accepted hominoid phylogeny. By emphasizing limb movements in the sagittal plane and limb elongation, terrestrial quadrupedalism preadapts an arboreal cautious climber to habitual bipedality. Ecological models based on cercopithecine analogies indicate that at least two adaptive stages prior to the elaboration of human material culture must have occurred if hominid divergence progressed from a semiarboreal life-style in a forest or woodland habitat to a committed terrestrial life-style in an open-country habitat. Based on a baboon model, the initial stage consisted of a generalized, widely distributed woodland ape. Predominantly quadrupedal, this ancestor utilized a wide range of behaviors to exploit a wide range of habitats and food resources. Analogous to gelada baboons, the second-stage hominids exhibited a commitment to open habitats while sacrificing generalized behaviors. The fossil evidence for hominid evolution closely fits this postulated model of hominid divergence. With decreasing geologic age, hominid fossils show an increasingly specialized structure and commitment to open habitats. The presence of (1) more than one hominid lineage committed to open habitats, (2) the likelihood of hybrids between different lineages, and (3) a discontinuous and fragmentary fossil record confound fossil phylogenies and the identification of ancestral hominids"--P. 2.Item The os navicular of humans, great apes, OH 8, Hadar, and Oreopithecus : function, phylogeny, and multivariate analysis. American Museum novitates ; no. 3288(New York, NY : American Museum of Natural History, 2000) Sarmiento, Esteban E.; Marcus, Leslie Floyd, 1930-2002.To clarify fossil hominid behavior and phylogeny, and to test the accuracy of basing these studies on single bones, navicular measurements of Olduvai and Hadar hominids, Oreopithecus, and a representative sample of humans and great apes were compared. The measurements chosen for comparison quantify the relative orientation, articular area, and curvature of the navicular facets. The measurements demonstrate that the OH 8 navicular belongs to a rigid foot with an adducted hallux and a strong commitment to terrestriality. The Hadar naviculars belong to a foot which lacked a fixed longitudinal plantar arch and had at least a degree of hallucal opposability comparable to that of mountain gorillas. The Oreopithecus navicular belongs to a mobile foot with a widely divergent hallux committed to arboreal behaviors. Multiple discriminant and canonical variate analyses of navicular measurements emphasize the uniqueness of Oreopithecus and the similarities between OH 8 and humans, and between Hadar and African apes. The African apelike morphology of the Hadar naviculars contradicts the alleged humanlike morphology of the Hadar pelvis and knee joints. This contradiction underscores the fallacies inherent in constructing phylogenies on the basis of single bones and/or fragmentary remains, and of reconstructing locomotor behaviors on the basis of localized anatomy.Item The phylogenetic position of Oreopithecus and its significance in the origin of the Hominoidea. American Museum novitates ; no. 2881(New York, N.Y. : American Museum of Natural History, 1987) Sarmiento, Esteban E."Since Oreopithecus was first described, its systematic position has been a subject of controversy. Despite the hominoid specializations in its postcrania, those classifications emphasizing the peculiarities in its dentition have arrived at numerous and varied interpretations. A review of the dental features of Oreopithecus, living catarrhines, and some known fossil catarrhines shows that those dental traits which may be used to classify Oreopithecus as either a hominoid, cercopithecoid, or early catarrhine exhibit a large degree of variability. Although only true hominoids exhibit the variability which encompasses all of the features of the Oreopithecus dentition, an early catarrhine or cereopithecoid could have possibly arrived at a similar dentition. The postcrania of Oreopithecus, however, shows conclusive evidence as to its hominoid affinities. As in hominoids, Oreopithecus exhibits the joint complex for forearm and shoulder rotation, both parts of a forelimb specialization which allows hominoids to climb vertical supports of large diameters. The large number of anatomical elements incorporated into this specialization and the one-to-one correspondence of these elements in Oreopithecus and hominoids strongly argue for a uniquely shared evolutionary history. Furthermore, Oreopithecus shares a strikingly large number of traits with a hypothetical ancestor of the pongid-hominid lineage more than any other known fossil form. Nevertheless, the position of Oreopithecus within the hominoids is uncertain. Many of the traits it shares with hylobatids may be expected in an early forerunner of the pongid-hominid lineage. On the other hand, many of those traits it shares with pongids may be expected in a large hylobatid which, due to its size, emphasized slow climbing aspects of its locomotor behavior"--P. 2.Item Terrestrial traits in the hands and feet of gorillas. American Museum novitates ; no. 3091(New York, N.Y. : American Museum of Natural History, 1994) Sarmiento, Esteban E.