Origin and history of the Erinaceinae and Brachyericinae (Mammalia, Insectivora) in North America. Bulletin of the AMNH ; v. 171, article 1
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Date
1981
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New York : American Museum of Natural History
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Abstract
"Modern Erinaceidae include the familiar hedgehog, Erinaceus europaeus, the archetypical primitive placental mammal in the minds of many biologists. Now restricted to the Old World, the family flourished in North America during the Miocene when three subfamilies were present there. Restricted to North America, the Brachyericinae seem to have originated on that continent. Both North American genera of Amphechinini (new tribe of the Erinaceinae) are well known in the Old World in earlier Oligocene deposits and hence appear to have immigrated into North America just before their first appearance there in the early Miocene. Area of origin of the Erinaceini may be interpreted as (1) unspecified within Holarctica plus the Ethiopian Region or (2) as external to Holarctica, depending on how the evidence is weighed. The sudden appearance of the tribe over the extent of Holarctica plus the Ethiopian Region at the beginning of the Miocene and the existence of an adequate structural ancestor in North America immediately prior to the time of initial appearance suggests the first interpretation. Counter to this, the presence in the Oligocene of a derived sister group of the Erinaceini (i.e., the Amphechinini) suggests that the tribe existed by that time, probably in an area where adequate collections from that epoch have not been made, e.g., Africa. Van Couvering (1972) has suggested that many forms which suddenly appear in the Miocene record of Europe without known precursors may have existed in Africa during the Oligocene and migrated only after the two continental blocks met in the mid-Cenozoic. Because the African Oligocene record of small mammals is so pitifully poor and a plausible reason exists for expecting that the Erinaceini existed there during that epoch, the second hypothesis appears more probable at this time. Once established in North America in the early Miocene, both the Erinaceinae and Brachyericinae had relatively uneventful histories. Least eventful was that of the Amphechinini, one species (Parvericius montanus) appearing to be conspecific with forms known in the Oligocene of Asia and the other species (Amphechinus horncloudi) differing only slightly from its Old World predecessors and contemporaries in that genus. Although A. horncloudi did not survive the Arikareean when it first appeared, P. montanus persisted with little noticeable change from that age through the Barstovian. Only one species of Erinaceini is recognized, Untermannerix copiosus (new), which appeared in the Barstovian and persisted until the Clarendonian with no noticeable change. More complex was the history of the Brachyericinae. Both genera have two species of markedly different size. In each, the smaller species appears to suddenly replace the larger. In the case of Metechinus, the evidence for this abruptness is equivocal but for Brachyerix it is highly compelling. Most useful in the analysis of the data has been the cladistic method as outlined by Hennig in his 1966 work. It was a fundamental tool in the development of the more plausible second hypothesis of the history of the Erinaceini outlined above. Determination of primitive and derived states or polarity of a given character, a fundamental problem of the cladistic method, was made by analyzing the distribution of the different states among the several groups recognized in an initial, credible higher phylogenetic hypothesis. Character states widely scattered in a haphazard pattern among the groups were regarded as primitive; ones found in only a few groups, particularly when thought to be closely related, were regarded as derived. In cases where the pattern was ambiguous, by restricting the sample examined to forms known prior to an arbitrary geologic epoch, it was often possible to determine polarity in this subset. Because in this procedure one is examining the forms that would have been available had one lived at that earlier, arbitrary date, the methodological pitfalls are no different from examining the total sample including modern forms"--P. 5.
Description
116 p. : ill., maps ; 26 cm.
Thesis (Ph. D.)--Columbia University.
Includes bibliographical references (p. [111]-116).
Thesis (Ph. D.)--Columbia University.
Includes bibliographical references (p. [111]-116).
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