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1 April 2013 A New Look at Morphological Variation in the Ichnogenus Anomoepus, with Special Reference to Material from the Lower Jurassic Newark Supergroup: Implications for Ichnotaxonomy and Ichnodiversity
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Abstract

Numerous new trackways of the small, ornithischian dinosaurs ichnogenus Anomoepus were discovered in the Lower Jurassic (Hettangian) East Berlin Formation in Holyoke, Massachusetts. This new material consists of 16 trackways, on two bedding surfaces 1.5 cm apart, all in close proximity to each other. The abundant pedal and manual impressions have well-preserved digital pad impressions, and claw marks are often discernible also. An Osteometric analysis allows reconstruction of the pedal digits and weight-bearing portions of the metatarsals. On the basis of their small size, as well as distinctive features and proportions of both the manus and pes impressions, these prints are assigned to the ichnospecies Anomoepus lacertoideus (comb. nov.). Three ichnospecies of Anomoepus can be recognized in the Lower Jurassic of the Newark Supergroup: A. lacertoideus, A. scambus and A. crassus. The A. lacertoideus footprints described herein provide evidence that this small, ornithischian track maker engaged in a variety of locomotion-related behaviors. Trackways mostly consist of digitigrade pes prints, reflecting bipedal locomotion, but intervals of quadrupedal progression also are documented by metatarsal and manus imprints in seven trackways. The longest trackways, each consisting of 10 to 15 pes impressions, vary in morphology as a result of the presence or absence of an impression of the distal parts of metatarsals II and IV. The manus prints show two distinct digital divarication angles, 120° and 180°, depending on whether the animal was walking normally or stopping. Variations in substrate consistency influenced locomotor behavior, as shown by the variable pattern of body weight distributions on the pedal digits. Such differences are especially apparent in the longest trackways, which vary in stride and pace lengths. The trends of the abundant trackways at this site also suggest group behavior in Anomoepus, something previously unrecorded for this ichnogenus in the Connecticut River Valley. Evidence from the East Berlin Formation suggests that ichnogenus Anomoepus is not monospecific as some authors have suggested.

© 2013 Peabody Museum of Natural History, Yale University. All rights reserved. • http://peabody.yale.edu
Sebastian G. Dalman and Robert E. Weems "A New Look at Morphological Variation in the Ichnogenus Anomoepus, with Special Reference to Material from the Lower Jurassic Newark Supergroup: Implications for Ichnotaxonomy and Ichnodiversity," Bulletin of the Peabody Museum of Natural History 54(1), 67-124, (1 April 2013). https://doi.org/10.3374/014.054.0104
Received: 8 October 2012; Accepted: 1 December 2012; Published: 1 April 2013
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