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Title: Can Geometric Morphometric Analyses of Limb Shape Reveal Ecomorphological Patterns Across the Evolutionary History of Synapsida?
Extant Mammalia are the only living representatives of the larger clade known as Synapsida, which has a continuous fossil record from around 320 million years ago to today. Despite the fact that much of the ecological diversity of mammals has been considered in light of limb morphology, the deep time origin of synapsid limb diversity and its influence on ecological diversity has received less attention. Here, we present shape analyses focusing on the forelimbs of the two earliest synapsid radiations (“pelycosaurs”, and pre-mammaliaforme Therapsida) in comparison to a broad sample of extant Mammalia. Using an expansive geometric morphometric data set, comprised of 384 fossil specimens and 148 extant mammalian specimens, we sought evidence for ecomorphological signals that could provide insight on the ecology of the earliest synapsids. Collecting shape data of humeral and ulnar elements from an extant sample representing multiple known eco morphologies provided the framework for a comparative exploration of extinct ecomorphologies, associated specifically with locomotion. Our results show that distal humeral shape is not informative of broad locomotor ecomorphologies in early fossil Synapsida. In contrast, proximal humeral shape shows a more complex pattern that suggests shape similarity between basal synapsids and members of extant Perissodactyla, and certain more » highly derived fully fossorial mammals, as just two examples. Overall, however, our findings suggest general shape analyses may have limited utility when analyzing for ecological-signal across deep time. Considering skeletal morphology in a holistic framework that considers unique combinations of shapes, as well as the use of biomechanically focused indices (such are functional proportions), may help to elucidate the more nuanced ways that locomotor ecology influenced limb shape in some of the earliest amniote radiations. « less
Authors:
;
Award ID(s):
1754502
Publication Date:
NSF-PAR ID:
10142679
Journal Name:
Journal of morphology
Volume:
280
Page Range or eLocation-ID:
S169
ISSN:
0898-9249
Sponsoring Org:
National Science Foundation
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