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Biomedical subjects

J G Fleagle

Publications and source records attributed to J G Fleagle.

32 records · Page 2Linked to original sources
PubMed1982

Function of the subclavius muscle in a nonhuman primate, the spider monkey (Ateles).

Within the primate order, the morphology of the subclavius muscle is known to be unique among the prehensile-tailed South American monkeys. 3 spider monkeys, Ateles, were monitored electromyographically to determine the recruitment of this muscle during various locomotor and postural activities. Rather than indicating a static stabilizing function, which has typically been inferred from classical anatomical studies, results from this study suggest that the subclavius performs more as a dynamic element in movements of the pectoral girdle during brachiation, vertical climbing, pronograde quadrupedalism and leaping. Complementary activity patterns were also identified between the subclavius and the caudal fibers of the trapezius indicating that the subclavius is used when the animal must depress, or resist cranial displacement, of the protracted shoulder girdle, while the caudal trapezius is recruited when the girdle is retracted on the chest wall.

Animals↗
PubMed1982

Skeletal remains of Propliopithecus chirobates from the Egyptian Oligocene.

A distal humerus, a fragmentary ulna, a tibia and several partial calcanei from Oligocene sediments in the Fayum Province of Egypt are attributed to Propliopithecus chirobates. Comparison and analysis of this material indicates that this species was an arboreal quadruped. All of the skeletal elements are more similar to the same bones in the Miocene hominoid Pliopithecus vindobonensis than to any extant primate species. Like Pliopithecus and Aegyptopithecus zeuxis, Propliopithecus exhibits numerous primitive skeletal features and more closely resembles living ceboids than either extant hominoids or cercopithecoid monkeys.

Animals↗
PubMed1980

Sexual dimorphism in early anthropoids.

Sexual dimorphism in canine/premolar tooth size and in body size is found among many species of living primates and has been shown to be correlated with social organization. Among extant higher primate species that normally live in the nuclear families consisting of a mated pair with their offspring, adult males and females are similar in body size and in the size of canine and anterior premolar teeth. In contrast, higher primate species living in more 'complex' polygynous groups (either single-male harems or multi-male groups) are characterized by sexual dimorphism in the size of canine/premolar teeth and frequently by body size dimorphism as well. We provide here the first evidence for sexual dimorphism in three species of primates from the Oligocene of Egypt--Aegyptopithecus zeuxis, Propliopithecus chirobates, and Apidium phiomense. This is the earliest record of sexual dimorphism among higher primates and suggests, by analogy with living species, that the earliest known fossil Old World anthropoids lived in polygynous (either single-male harems or multi-male groups) rather than monogamous social groups.

Animals↗
PubMed1980

An electromyographic study of the pectoralis major in atelines and Hylobates, with special reference to the evolution of a pars clavicularis.

Among primates there is striking variation in the extent of the origin of pectoralis major from the clavicle. A significant clavicular attachment (pars clavicularis) occurs only in Alouatta, Lagothrix, Hylobates, Pan (troglodytes, paniscus and gorilla), and Homo. Interpreting this trait in nonhuman primates as an adaptation to frequent use of a mobile forelimb in climbing and suspension is contraindicated by the absence of a clavicular origin in Ateles and Pongo. We have undertaken a telemetered electromyographic study to determine any special role of the most cranial part of the pectoralis major in comparison to its caudal part, and to the deltoid, during vertical climbing, pronograde quadrupedalism, and armswinging in Ateles, Lagothrix, Alouatta, and Hylobates. The results show that the cranial pectoralis major possesses a role not shared by the caudal fibers: initiation of the recovery phase of the locomotor cycle. When ability to execute rapid or powerful recovery of the adducted forelimb is required in an animal with a shoulder joint lying on a plane cranial to that of the manubrium, the movement will be facilitated if the origin of the pectoralis major is extended onto the clavicle. Such is the case in nonhuman primates possessing this trait. The absence of a clavicular origin in Ateles and Pongo may be related to diminished selective pressures to perfect locomotor modes such as pronograde quadrupedalism, armswinging, or climbing thick vertical trunks, that demand rapid or powerful recovery of the adducted forelimb. If the arboreal ancestor of humans had evolved a clavicular origin of pectoralis major, this animal would be preadapted for certain uses of the forelimb in its bipedal descendant.

Alouatta↗
PubMed1980

Postnatal growth allometry of the extremities in Cebus albifrons and Cebus apella: a longitudinal and comparative study.

Cebus albifrons and Cebus apella, partially sympatric capuchin monkeys from South America, are known to differ substantially in adult body mass and bodily proportions. C. apella possesses a robust, stocky build in contrast to the more gracile, relatively longer limbed body design of C. alblfrons. Average birth weights and adult body lengths of these two congeners, however, are remarkably similar and do not serve to distinguish them. This study examines longitudinal growth rates and patterns of ontogenetic scaling in the extremities (humerus, radius, hand, femur, tibia, foot) in order to document the nature and magnitude of skeletal changes associated with increasing age and body mass. Our data indicate that the growth rates of the six skeletal components of the limbs differ only slightly and somewhat inconsistently between the two species. Body mass, however, increases at a consistently faster rate in C. apella. Relative to body mass, therefore, the extremities of C. albifrons scale much faster than those of C. apella. This implies that at any given postnatal body mass, C. alblfrons is longer limbed that C. apella. Conversely, C. apella is heavier than C. albifrons at any given limb length or age. We suggest that such differences in body mass distribution are causally related to differences in locomotor behavior and foraging strategies. Specifically, the relatively long-limbed C. albifrons is probably more cursorial and tends to travel longer distances each day than C. apella. C. apella is a much more deliberate quadruped and is also characterized by especially vigorous and powerful foraging and feeding behaviors. We also compare our results to other (mostly cross-sectional) studies of skeletal growth allometry in nonhuman primates.

Animals↗
PubMed1979

Anatomy of the bony pelvis in parapithecid primates.

Four partial innominate bones, attributed to the parapithecid primates Parapithecus grangeri and Apidium phiomense, have recently been recovered from Oligocene deposits in the Fayum of Egypt. These fossils provide the first documentation of pelvic morphology for early anthropoids. In pelvic anatomy, parapithecids show definite similarities to higher primates rather than to prosimians, but cannot be clearly allied with any one extant group. Functionally, the fossils indicate quadrupedal or leaping habits rather than suspensory or bipedal behaviors.

Acetabulum↗
PubMed1978

Micropithecus clarki, a small ape from the Miocene of Uganda.

Micropithecus clarki, from Miocene sediments of Napak, Uganda, is the smallest known hominoid primate, living or fossil. In facial morphology it is very similar to extant gibbons. Dentally, it is most similar to the small apes from the Miocene of Kenya, Dendropithecus and Limnopithecus. All of the apes from the early Miocene of East Africa seem to represent a single phyletic group that could be easily derived from the Oligocene apes known from the Fayum of Egypt. Pliopithecus from the Miocene of Europe is more closely allied with the Oligocene radiation than with the later East African radiation.

Animals↗
PubMed1977

Locomotor behavior and muscular anatomy of sympatric Malaysian leaf-monkeys (Presbytis obscura and Presbytis melalophos).

Sympatric Malaysian leaf-monkeys, Presbytis obscura and Presbytis melalophos show quantitative differences in their use of different locomotor patterns during daily activities. P. obscura primarily moves quadrupedally along large boughs; P. melalophos relies more on leaping between smaller supports. P. melalophos also uses forelimb suspension more than does P. obscura. Comparison of the muscular anatomy of the shoulder, arm, trunk, hip and thigh show numerous statistically significant differences between the two species in relative mass of individual muscles and in details of muscular origin and insertion. In almost all instances these differences accord with the types of differences in muscular anatomy predictable from either biomechanical analyses of locomotor behavior or comparative anatomical studies of other mammalian species.

Animals↗
PubMed1976

Locomotion and posture of the Malayan siamang and implications for hominoid evolution.

Wild, adult siamang were observed for over 800 h in lowland dipterocarp forest in the Krau Game Reserve, Pahang, West Malaysia. Siamang use four patterns of locomotion: brachiation, climbing, bipedalism and leaping. The pattern of locomotion used by the siamang varies with the size of arboreal supports and with major behavioral activity. Travel is primarily by brachiation along large boughs. Locomotion during feeding is primarily climbing among small branches. In feeding, siamang use suspensory postures among small supports and seated postures on large supports. Comparison of siamang locomotion and posture with that of other apes suggest that quadramanous climbing during feeding is the basic hominoid locomotor adaptation.

Animals↗
PubMed1975

Ape limb bone from the oligocene of Egypt.

An ulna attributed to Aegyptopithecus zeuxis provides the first evidence for interpreting the locomotor behavior of the earliest apes. The fossil indicates that Aegyptopithecus was an arboreal quadruped and that the primitive hominoid locomotor pattern was most nearly analogous, among living primates, to that of Alouatta, the howler monkey.

Animals↗
PubMed1975

Physical growth of cebus monkeys, Cebus albifrons, during protein or calorie deficiency.

Infant cebus monkey (Cebus albifrons) on experimental diets providing low-protein (2.8% of calories) or low-calorie (67% of ad libitum intake) levels for 20 weeks beginning at 8 weeks of age showed marked changes in their patterns of physical growth. Significant size differences between the malnourished animals and the control group appeared within 4 weeks. Although rates of growth were significantly reduced in all measurements, all of the malnourished monkeys, including low-protein animals showing zero weight gain, continued skeletal growth (except in skull measurements) at low levels for the duration of experiment. Both the protein- and calorie-restricted animals developed a thin, emaciated appearance often associated with marasmus, not by the continuous loss of tissue byt by the redistribution of the tissue over a slowly expanding skeleton. For many skeletal proportions, the pattern and shape development in the malnourished animals differed from that of the control animals. Growth during malnutrition was most affected in those parts of the skeleton which were more advanced in relative size.

Animal Nutritional Physiological Phenomena↗
PubMed1975

A small gibbon-like hominoid from the miocene of Uganda.

A new palate from Napak IV in Uganda, dated at 19 million years or older, provides information about the facial morphology of a small Miocene hominoid from East Africa. The fossil resembles small extant gibbons in most features of facial and papatal morphology that are preserved, more so than does its European contemporary, Pliopithecus (Epipliopithecus) vindobonensis. The Ugandan hominoid is most closely related to the small Kenyan hominoids formerly placed in the genus Limnopithecus.

Animals↗
PubMed1975

Physical growth of cebus monkeys (Cebus albifrons) during the first year of life.

Infannt cebus monkeys, removed from their mothers shortly after birth, were reared in a primate nursery on diets of controlled nutritional quality. At regular intervals between birth and one year of age, each monkey was anesthetized, measured, and radiographed. Measurements were fitted to functions of the animal's age in days; a linear function for the first 6 to 8 weeks and a logarithmic function for the remainder of the first year. Mean constant curves have been calculated for each measure and estimates of animal variability have been obtained by interpolating sizes at given ages from regression lines fitted to the data for each animal. The maximum rate of growth was attained soon after birth. Cranial-caudal and distal-proximal maturity gradients in size attainment were observed.

Animal Nutritional Physiological Phenomena↗