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Aspects of the systematics and paleoecologies of the middle to late Miocene North American rhinoceroses Peraceras, Teleoceras, and Aphelops

Alfred James Mead, University of Nebraska - Lincoln

Abstract

The Rhinocerotidae has a long and diverse history in North America. Much of the later portion of this history is recorded in Tertiary deposits of Nebraska and the surrounding Great Plains. Recovery of a large quarry sample of cranial and postcranial material from the Hottell Ranch Rhino Quarries, Banner County, Nebraska, allows the first detailed characterizations of the medial Barstovian rhinoceroses Peraceras superciliosum Cope and Teleoceras minor Olcott. The early to medial Barstovian “Aphelops ” ceratorhinus Douglass and “ Aphelops” montanus Douglass, from the Madison River and Flint Creek Valleys of Montana, are referred to Peraceras ceratorhinum (Douglass) n. comb. The affinities of Peraceras profectum (Matthew) and Peraceras hessei Prothero and Manning to the genotypic species Peraceras superciliosum remain unresolved. Sexual dimorphism is documented in 35 articulated adult skeletons of the Miocene rhinoceros Teleoceras major from Ashfall Fossil Beds, Antelope County, Nebraska. Morphometric analysis of 51 cranial, mandibular, forelimb, and hindlimb characters reveals larger male mean values in 50 of the 51 measurements, 23 are significantly different. Developmental maturity is apparently asynchronous in Teleoceras major, with fusion of longbone epiphyses delayed a minimum of two relative adult age classes in males. The sexual dimorphism, apparent herd structure, and breeding-age sex ratio for the Ashfall herd suggests that Teleoceras was a herding rhinoceros with a dominant bull and harem breeding system, ecologically similar to extant Hippopotamus amphibius of Africa. Nebraska quarry samples of lower cheek teeth of the Miocene rhinoceros Teleoceras are analyzed for the presence of enamel hypoplasia using macroscopic, thin-section, and scanning electron microscopic techniques. Isolation of the enamel hypoplasia to distinct bands on the Teleoceras dp4's suggests causes linked to severe physiological stress due to metabolic disruption or nutritional deficiency occurring at or very near birth. The observed p4-hypoplasias appear to reflect physiological stresses not related to weaning, but some other stressful period such as cow-calf separation prior to the birth of the next offspring.

Subject Area

Paleontology|Paleoecology|Paleontology

Recommended Citation

Mead, Alfred James, "Aspects of the systematics and paleoecologies of the middle to late Miocene North American rhinoceroses Peraceras, Teleoceras, and Aphelops" (1999). ETD collection for University of Nebraska-Lincoln. AAI9951302.
https://digitalcommons.unl.edu/dissertations/AAI9951302

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