Development of Feeding and Airway Protection in Preterm Infant Mammals as a Model of Altricial Evolution
Title
Development of Feeding and Airway Protection in Preterm Infant Mammals as a Model of Altricial Evolution
Creator
German R Z; Mayerl C J; Gould F H; McGrattan K E
Publisher
Journal of Morphology
Date
2019
2019-06
Description
12th International Congress of Vertebrate Morphology, held July 21 – 25, 2019 in Prague, Czech Republic
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During the land‐to‐water transition in the Eocene, the cetacean skeleton underwent modifications that are well‐documented in the fossil record. The forelimb changed from a weight‐bearing pentadactyl structure to a flipper with an immobile carpus. Extant mysticetes, baleen whales, maintain six carpals, ossification of which is delayed or absent. Carpal number and morphology vary in odontocetes, toothed whales. Modern artiodactyls, which share a common ancestry with cetaceans, alter their carpal number in relation to the reduction of metacarpals. The most archaic artiodactyls have digit morphologies similar to Eocene whales. We used CT‐imaging to assess evolutionary changes in the articulation of the carpus within Eocene taxa associated with the limb‐to‐flipper transition. In particular, we compared Ambulocetus natans, a well‐preserved amphibious archaeocete taxon, with other semi‐aquatic archaeocetes. The pisiform of A. natans is robust and projects laterally, an orientation shared with extinct and extant cetaceans. However, articulation of the pisiform and trapezium vary among archaeocetes. The pisiforms of A. natans and Dorudon atrox, another Eocene cetacean, articulate with the ulna and cuneiform. This carpal is small in Maiacetus inuus, an Eocene cetacean, and lacks contact with the ulna. The trapezium of most mammals articulates with metacarpal I and the scaphoid. Both the trapezium and trapezoid lie distal to the scaphoid and medial to the magnum in terrestrial mammals. M. inuus differs from this pattern; the trapezium articulates with the radius. Moreover, M. inuus and A. natans display an additional carpal that lacks an artiodactyl homologue. The trapezium is lost in pentadactyl cetaceans, leaving direct contact between the scaphoid and metacarpal I. These morphological changes may relate to functional shifts from weight‐bearing locomotion to a mediolaterally expanded flipper that acts as a control surface.
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During the land‐to‐water transition in the Eocene, the cetacean skeleton underwent modifications that are well‐documented in the fossil record. The forelimb changed from a weight‐bearing pentadactyl structure to a flipper with an immobile carpus. Extant mysticetes, baleen whales, maintain six carpals, ossification of which is delayed or absent. Carpal number and morphology vary in odontocetes, toothed whales. Modern artiodactyls, which share a common ancestry with cetaceans, alter their carpal number in relation to the reduction of metacarpals. The most archaic artiodactyls have digit morphologies similar to Eocene whales. We used CT‐imaging to assess evolutionary changes in the articulation of the carpus within Eocene taxa associated with the limb‐to‐flipper transition. In particular, we compared Ambulocetus natans, a well‐preserved amphibious archaeocete taxon, with other semi‐aquatic archaeocetes. The pisiform of A. natans is robust and projects laterally, an orientation shared with extinct and extant cetaceans. However, articulation of the pisiform and trapezium vary among archaeocetes. The pisiforms of A. natans and Dorudon atrox, another Eocene cetacean, articulate with the ulna and cuneiform. This carpal is small in Maiacetus inuus, an Eocene cetacean, and lacks contact with the ulna. The trapezium of most mammals articulates with metacarpal I and the scaphoid. Both the trapezium and trapezoid lie distal to the scaphoid and medial to the magnum in terrestrial mammals. M. inuus differs from this pattern; the trapezium articulates with the radius. Moreover, M. inuus and A. natans display an additional carpal that lacks an artiodactyl homologue. The trapezium is lost in pentadactyl cetaceans, leaving direct contact between the scaphoid and metacarpal I. These morphological changes may relate to functional shifts from weight‐bearing locomotion to a mediolaterally expanded flipper that acts as a control surface.
Subject
Anatomy & Morphology
Identifier
Rights
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URL Address
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Pages
S126–S126
Volume
280
ISSN
0362-2525
Citation
German R Z; Mayerl C J; Gould F H; McGrattan K E, “Development of Feeding and Airway Protection in Preterm Infant Mammals as a Model of Altricial Evolution,” NEOMED Bibliography Database, accessed April 26, 2024, https://neomed.omeka.net/items/show/6433.