Brachyerix, a Miocene hedgehog from western North America, with a description of the tympanic regions of Paraechinus and Podogymnura. American Museum novitates ; no. 2477

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New York, N.Y. : American Museum of Natural History
"Although living hedgehogs have long been regarded [as] the archetypes of the primitive placental mammal, they have nonetheless had a complex Cenozoic history that is reflected in the recognition of three extinct and two living erinaceid subfamilies. Members of one extinct subfamily, the Brachyericinae, underwent a remarkable shortening of the skull and a reduction in the number of teeth during the Oligocene, Miocene, and early Pliocene. This trend culminated in the two North American genera, Brachyerix and Metechinus, in which only three teeth were retained anterior to P[subscript]4. Dimylechinus, a European form from the early Miocene, and Exallerix from the medial Oligocene of Asia both retained at least four teeth anterior to P[subscript]4. None of the four genera had an M[subscript]3. Brachyerix and Metechinus occur from the Great Plains to the Pacific coast of North America. Brachyerix is temporally restricted to the Miocene; Metechinus occurs in late Miocene and early Pliocene sediments. Although both genera are known from several localities, they are never found together, which may reflect an ecological separation of these two forms during temporal overlap. Both are known only from cranial osteology. During the past 40 years, the differences between these two North American genera have not been well defined, and only now with the availability of several specimens of each can the generic boundaries be adequately reviewed. Two species of Brachyerix are recognized in the present paper. Brachyerix macrotis, restricted to the early and medial Miocene, is the larger of the two and differs from B. incertis, new combination (late Miocene), in having a stronger lingual cingulum on P[superscript]3 and in entirely lacking a P[superscript]3 protocone. Metechinus marslandensis can now be synonymized with B. macrotis, whereas Talpa incerta and Metechinus fergusoni are both junior synonyms of B. incertis. Only Metechinus nevadensis still requires generic separation owing to its unique basicranium, small auditory bullae, nature of the sagittal crest, and relatively anteroposteriorly compressed M[subscript]1 trigonid. Dimylechinus bernoullii is an adequate structural ancestor for Brachyerix macrotis and its descendents. However, as both Dimylechinus and Exallerix are known only from single specimens, their relationship to the North American brachyericines as well as to one another is not well understood and will not be until further specimens are found. An appendix describing the ear regions of two living hedgehog genera, Paraechinus and Podogymnura, is included to supplement Butler's (1948) paper on the erinaceid ear region. Paraechinus is the only living erinaceid that has bony tubes covering part of the blood vessels contained in the tympanic cavity, a condition developed to the extreme in the Miocene Brachyerix"--P. [1]-2.
58 p. : ill. ; 24 cm.
Includes bibliographical references (p. 56-58).