Systematics of Lower and Lower Middle Devonian species of the trilobite Phacops Emmrich in North America. Bulletin of the AMNH ; v. 151, article 4

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New York : [American Museum of Natural History]
"Six species (one new) including 20 subspecies (4 new) of Phacops are recognized from the Lower and Middle Devonian of North America. Gedinnian-Siegenian species include P. logani Hall, 1861, and P. claviger Haas, 1969. Phacops clarksoni, new species, occurs in the Emsian Schoharie Formation of New York, and P. cristata Hall, 1861, occurs in the Emsian and Eifelian of the Appalachian Province. Phacops iowensis Delo, 1935, and P. rana (Green, 1832) occur in Givetian strata. A conservative position is taken on generic nomenclature and defended herein; all species, with the exception of P. rana are closely related and belong to the same monophyletic taxon. Special topics include a quantitative analysis of eye polymorphism and ontogeny in Phacops logani birdsongensis Delo, 1940, and P. logani raymondi (Delo, 1935), and of eye ontogeny in Phacops cristata stummi, new subspecies and P. c. canadensis (Stumm, 1954). Cladistic methodology in paleontology is briefly discussed, and theories of relationship among all subspecies and species are presented. A key to all Devonian phacopid taxa considered valid herein is included"--P. 289.
p. 287-337 : ill. ; 27 cm.
Includes bibliographical references (p. 336-337).