Defining the Ichnogenus Arthrophycus Using Numerical Taxonomic Methods

ABSTRACT

A century and a half of imprecise or overly brief descriptions and ambiguous or unclear illustrations have rendered the ichnogenus Arthrophycus ripe for reexamination. An abundance of well-preserved, accessible Arthrophycus specimens from museum collections made it possible to use numerical taxonomic methods to distinguish among ichnospecies of Arthrophycus and refine the diagnosis of the ichnogenus using measurable, reproducible characters. We defined 16 characters for the numerical analyses. Cluster analysis sorts the ichnospecies of Arthrophycus into two groups: a cluster of five ichnospecies, comprising A. alleghaniensis, A. brongniartii, A. lateralis, A. minimus, and A. parallelus, which conform to a coherent concept of Arthrophycus, and a second cluster comprising 14 ichnotaxa questionably assigned to Arthrophycus. Principal coordinates analysis supports the separation of these two groups. The numerical analyses provide a rationale for taxonomic revision of the ichnogenus and the ichnospecies that have been assigned to it.

KEYWORDS:

• Arthrophycus
• Ichnotaxonomy
• Numerical taxonomy

Acknowledgments

MES thanks R. L. Anstey, B.Hampton, and R. Snider for guidance and encouragement, her family for their support, K. Linta and family for their hospitality, J. Wei, G. Yedid and Y. Ki for translation assistance. S. Butts of the Yale Peabody Museum, B. Husseini of the American Museum of Natural History, E. Landing and L. Hernick of the New York State Museum, and R. Laub of the Buffalo Museum of Science provided access to their collections. We thank A. K. Rindsberg and an anonymous reviewer for their meticulously thorough and edifying critiques.