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The Aglaspidid Arthropod Beckwithia from the Cambrian of Utah and Wisconsin

Stephen P. Hesselbo
Journal of Paleontology
Vol. 63, No. 5 (Sep., 1989), pp. 636-642
Published by: Paleontological Society
Stable URL: http://www.jstor.org/stable/1305623
Page Count: 7
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The Aglaspidid Arthropod Beckwithia from the Cambrian of Utah and Wisconsin
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Abstract

New specimens of Beckwithia typa, from the upper Middle Cambrian of Utah, show that, contrary to previous descriptions, the animal had at least 10 tergites (possibly 12) and probably a tail-spine. There is no evidence for a fused tail-plate, the one character that made Beckwithia appear anomalous with respect to other aglaspidid arthropods. It did, however, differ from most other aglaspidids in having a single series of axial spines along the trunk, but this cannot be regarded as a basis for continued separation of Beckwithia into a monogeneric family. A possible relationship with Kodymirus vagans is suggested by the presence of axial spines, although there may have been significant differences in the nature of the ventral sclerites. Beckwithia? major from the Upper Cambrian of Wisconsin is known only from fragmentary specimens and no evidence of a fused tail-plate has been found. Beckwithia? daubikhensis from the Khanka Massif, Soviet Union, is unlikely to be a member of this genus; the single specimen on which the taxon was based may be a poorly preserved Khankaspis bazhanovi.

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