Abstract/Details

A reconsideration of the <i>Arthrophycus</i> ichnogenus: Definition, biostratigraphic utility, and a proposal to develop a numerical ichnotaxonomy


2010 2010

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Abstract (summary)

Arthrophycus Hall 1852 is a long-studied ichnogenus reported from localities worldwide, including all seven continents and twenty-eight countries. It is most abundant in Ordovician and Silurian strata and is regarded by some ichnologists as having biostratigraphic utility, although other occurrences of the ichnogenus have been reported from the Proterozoic to the Miocene. Imprecise or overly-brief descriptions and ambiguous or unclear illustrations, drawings, and photographs of specimens regarded as Arthrophycus have resulted in a taxonomic "wastebasket" and have led to confusion over the biostratigraphic utility of the ichnogenus.

A review of the primary Arthrophycus literature converged on the following diagnostic characters for the ichnogenus: annulations, simple form, branches, bundles, shape of cross-section, median groove, and internal structures. Characters such as annulations, branching, and median groove encompass variability not previously discussed in reviews of the ichnogenus. Refining the definition of these characters produced sixteen characters that could be coded for a numerical phenetic analysis of Arthrophycus ichnospecies. Cluster analyses revealed two main clusters: a cluster of six (A. alleghaniensis, A. brongniartii, A. linearis, A. lateralis, A. minimus, A. parallelus) considered to be valid Arthrophycus and a second cluster of discredited iclulospecies, members of which probably belong in other ichnogenera. The cluster analyses were supported by PCO and cladistic analyses.

Only Paleozoic occurrences of Arthrophycus are considered valid, including specimens from the Cambrian, Devonian, and Carboniferous, challenging previous conclusions that Arthrophycus is confined to the Ordovician and Silurian. This analysis also confirms an hypothesis that Arthrophycus originated in the southern continents in the Cambrian, persisted there in the Ordovician, and then expanded to the northern continents during the late Ordovician and Silurian.

Indexing (details)


Subject
Evolution and Development;
Paleontology
Classification
0412: Evolution and Development
0418: Paleontology
Identifier / keyword
Earth sciences; Biological sciences; Arthrophycus; Ichnotaxonomy
Title
A reconsideration of the <i>Arthrophycus</i> ichnogenus: Definition, biostratigraphic utility, and a proposal to develop a numerical ichnotaxonomy
Author
Seitz, Megan E.
Number of pages
224
Publication year
2010
Degree date
2010
School code
0128
Source
DAI-B 71/08, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
9781124137940
Advisor
Brandt, Danita S.
University/institution
Michigan State University
University location
United States -- Michigan
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3417673
ProQuest document ID
746097340
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/746097340
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