The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Tom Rothwell - One of the best experts on this subject based on the ideXlab platform.
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New Felid Material from the Ulaan Tologoi Locality, Loh Formation (Early Miocene) of Mongolia
2015Co-Authors: Tom RothwellAbstract:Herein I describe new felid material from the early Miocene, Ulaan Tologoi locality of Mongolia. A dentary fragment and a Metapodial are the first large felid fossils to be recovered from the early Miocene of Asia. Both specimens are referred to the genus Pseudaelurus. Comparisons of these Asian specimens to previously described European, Asian, and North American species provide insights into the size and form of this cat. I review the Asian literature on early felids and discuss possible causes for fossil felid scarcity in the early Miocene of Asia
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Chapter 12: New Felid Material from the Ulaan Tologoi Locality, Loh Formation (Early Miocene) of Mongolia
Bulletin of the American Museum of Natural History, 2004Co-Authors: Tom RothwellAbstract:Abstract Herein I describe new felid material from the early Miocene, Ulaan Tologoi locality of Mongolia. A dentary fragment and a Metapodial are the first large felid fossils to be recovered from the early Miocene of Asia. Both specimens are referred to the genus Pseudaelurus. Comparisons of these Asian specimens to previously described European, Asian, and North American species provide insights into the size and form of this cat. I review the Asian literature on early felids and discuss possible causes for fossil felid scarcity in the early Miocene of Asia.
Robert G. Tague - One of the best experts on this subject based on the ideXlab platform.
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Rudimentary, “functionless” first Metapodials of Canis latrans : variation and association in length with longer, functional Metapodials
Evolution; international journal of organic evolution, 2020Co-Authors: Robert G. TagueAbstract:A tenet of evolutionary theory is that phenotypic variation of a trait is inversely related to the intensity of stabilizing selection pressure. Among homologous bones, such as Metapodials, a rudimentary, “nonfunctional” bone is expected to be more variable in length than nonrudimentary bones. This study compares variation and association in length among Metapodials using 277 adult skeletons of Canis latrans. Ca. latrans has a short, “functionless” first metacarpal (mc1) and “rudimentary, vestigial” first metatarsal (mt1). Results show that among the 10 Metapodials, mt1 has the highest variation in length; other Metapodials do not differ significantly from one another in their variation. Correlation coefficients for length of mc1 and mt1 with their ipsilateral Metapodials 2‐5 are significantly lower than coefficients for all other ipsilateral pairs. The correlation coefficient between left and right mt1 is significantly the lowest among all bilateral pairs of Metapodials. Results are interpreted as follows. Mt1's high variation and low association in length are the outcome of less intense stabilizing selection pressure compared with other Metapodials. The nonsignificant difference for variation in length between mc1 and Metapodials 2‐5 may be that mc1 is functional for development of a pollical dewclaw that helps restrain small prey. This article is protected by copyright. All rights reserved
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Variability of Metapodials in primates with rudimentary digits: Ateles geoffroyi, Colobus guereza, and Perodicticus potto.
American Journal of Physical Anthropology, 2002Co-Authors: Robert G. TagueAbstract:A tenet of evolutionary theory is that, within a species, phenotypic variability is inversely related to the intensity of stabilizing selection. A corollary is that a rudimentary or vestigial structure should be highly variable. This relationship between rudimentation and variability, however, may simply be part of a continuum, as several studies have shown that variability and size of a structure are inversely related. This study tests whether the first metacarpal (MC1) in Ateles geoffroyi and Colobus guereza and the second metacarpal (MC2) in Perodicticus potto are highly variable in their lengths relative to their other Metapodials. The former two species have rudimentary thumbs, and the latter species has a rudimentary index finger. Fourteen other species of primates are included in the comparison. The results show that MC1 in A. geoffroyi and C. guereza and MC2 in P. potto are the relatively shortest first and second Metapodials, respectively, in this sample of primates. However, an intraspecific analysis shows that neither MC1 in A. geoffroyi and C. guereza nor MC2 in P. potto is significantly more variable than the other Metapodials. Nevertheless, an interspecific analysis shows that MC1 in A. geoffroyi and C. guereza is relatively the most variable among the first Metapodials (i.e., MC1 and first metatarsal) in this study. MC2 in P. potto, however, is of relatively low variability compared with the other primates. These contrasting results are interpreted in terms of the developmental and evolutionary biology of digits.
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VARIABILITY OF A VESTIGIAL STRUCTURE: FIRST METACARPAL IN COLOBUS GUEREZA AND ATELES GEOFFROYI.
Evolution, 1997Co-Authors: Robert G. TagueAbstract:A tenet of evolutionary theory is that, under conditions of stabilizing selection, phenotypic variability is inversely related to selection intensity. Correspondingly, a nonfunctional, vestigial structure is expected to be highly variable relative to its functional homologue. This study tests the hypothesis that species with a vestigial pollex, Colobus guereza and Ateles geoffroyi, have a first metacarpal whose length is both highly variable relative to, and poorly correlated with, the lengths of the other Metapodials. The results are consistent with the hypothesis, though this combination of traits is also found in Presbytis rubicunda and Presbytis cristata. The latter two species have functional, albeit miniature, pollices. This study also demonstrates a general, inverse relationship among anthropoid primates between relative length of the first Metapodial and its relative variability. These results suggest that elevated variability accompanies structural reduction.
C. Owen Lovejoy - One of the best experts on this subject based on the ideXlab platform.
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Metapodial or phalanx? An evolutionary and developmental perspective on the homology of the first ray's proximal segment.
Journal of experimental zoology. Part B Molecular and developmental evolution, 2013Co-Authors: Philip L. Reno, Walter E. Horton, C. Owen LovejoyAbstract:The first mammalian Metapodial (MP1) has periodically been argued to actually be a phalanx, because the first ray has one less element than the four posterior rays, and because the MP1 growth plate is proximal like those of all phalanges, rather than distal as in Metapodials 2–5. However, growth plates are formed at both ends in non-therian tetrapod Metapodials, and phylogenetic analysis demonstrates that growth plate loss is a therian synapomorphy that postdates the establishment of the mammalian phalangeal formula. These data, along with results of developmental and morphological studies, suggest that the MP1 is not a phalanx. The singular, proximal growth plates in MPs 2–5 are likely to be an adaptation to dynamic erect quadrupedal gait which was characterized by conversion of the posterior Metapodials into rigid struts with the carpus/tarsus. While the adaptive significance of the reversed ossification of MP1 is less clear, we present three functional/developmental hypotheses. J. Exp. Zool. (Mol. Dev. Evol.) 320B:276–285, 2013. © 2013 Wiley Periodicals, Inc.
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Growth Plate Formation and Development in Alligator and Mouse Metapodials: Evolutionary and Functional Implications
Journal of experimental zoology. Part B Molecular and developmental evolution, 2007Co-Authors: Philip L. Reno, Ruth M. Elsey, Walter E. Horton, C. Owen LovejoyAbstract:Mammalian Metapodials (metacarpals and metatarsals), unlike most long bones, form a single growth plate, and undergo longitudinal growth at only one end. The growth dynamics of non-mammalian tetrapod Metapodials have not been systematically examined in order to determine if unidirectional growth is unique to mammals. Here we compare murine Metapodial ossification in growth stages that parallel those of embryonic, juvenile and subadult American alligators (Alligator mississippiensis). Safranin O staining was used for qualitative histology, and chondrocyte differentiation and proliferation were assessed via immunohistochemistry for type X collagen and proliferative cell nuclear antigen (PCNA). We establish that growth plates form at both ends of alligator Metapodials and are maintained in the subadult. PCNA results show that alligators and mice share common patterns of chondrocyte proliferation during growth plate formation. In addition, while alligators and mice differ initially in the degree of organization and pace of chondrocyte differentiation, these parameters are largely similar in established growth plates. However, the replacement of cartilage by bone is highly irregular throughout growth in the alligator, in contrast to the more uniform process in the mouse. These results indicate that while alligators and mammals share common mechanisms of chondrocyte regulation, they differ substantially in their processes of ossification. Phylogenetic analysis indicates that the direct ossification of one epiphysis and reliance on a single growth plate is a derived character (synapomorphy) in therian mammals and likely indicates an adaptation for erect quadrupedal gait.
Jesus M Perez - One of the best experts on this subject based on the ideXlab platform.
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Sarcoptic mange and Metapodial development in growing male Iberian ibex (Capra pyrenaica).
Veterinary parasitology, 2006Co-Authors: Emmanuel Serrano, Jose E Granados, Jesus M PerezAbstract:The effect of mange (Sarcoptes scabiei) on Metapodial growth was studied in 24 uninfested and 16 infested male Iberian ibex from Sierra Nevada National Park (southern Spain). Our results show that infested ibex had smaller metatarsal bones, lower body weight, and a delayed rhythm of ossification, by about 1 year. We conclude that skeletal development and body weight in the Iberian ibex are sensitive to sarcoptic mange.
Mark C. Lawler - One of the best experts on this subject based on the ideXlab platform.
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Skull, mandible, and Metapodials of the extinct Harrington's mountain goat (Oreamnos harringtoni)
Journal of Vertebrate Paleontology, 1995Co-Authors: Jim I. Mead, Mark C. LawlerAbstract:ABSTRACT Chester Stock (1936) described a late Rancholabrean species of extinct mountain goat (Oreamnos harringtoni) based on scant remains from a cave in the Great Basin, Nevada. We present a review using cranial, mandibular, and Metapodial remains of O. harringtoni from 13 localities in the southwest. The extinct mountain goat is not just a smaller form of the living species, O. americanus. O. harringtoni has Metapodials 25% smaller than those of the living species, indicating that the mountain goat is shorter; however, its feet are relatively robust. Its masticatory region is robust but is situated on a narrower face; the apparently longer, narrower face is accentuated by the presence of thinner and smaller horns.