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Ptiloncodus Harris, 1962; a Laurentian enigma

Published online by Cambridge University Press:  14 July 2015

R. L. Ethington  and
L. M. Ross Jr.
R. L. Ethington
Affiliation:
Department of Geological Sciences, University of Missouri, Columbia, Missouri 65211,
L. M. Ross Jr.
Affiliation:
Electron Microscopy Core Facility, University of Missouri, Columbia, Missouri 65211
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Abstract

Ptiloncodus Harris, 1962, a hook-shaped microfossil, is present in late Floian through Hirnantian [=late Ibexian through Gamachian] rocks in regions marginal to Laurentia. Specimens from the Great Basin provide additional information about this enigmatic microfossil. Two fused clusters of Ptiloncodus elements from western Utah do not duplicate clusters reported previously from coeval strata in central Nevada. EDS spectra confirm the long-standing assumption that these fossils are composed of calcium phosphate. SEM images show that short crystallites are aligned to provide fibrous surficial ultrastructure in the hooked part of these fossils, but more open arrangement is displayed at the top of the shank where paired lobate structures are attached. The join between the lobes and the shank is weak; these two parts of the fossil separate easily so that most specimens did not retain lobes. The shanks end in rounded terminations or in paired knobs that range from low protuberances to near hornlike features. The new data do not support any of several suggestions that compare Ptiloncodus to extant organisms, and uncertainty continues about its affinity and the function of its skeletal elements.

Type
Research Article
Information
Journal of Paleontology , Volume 84 , Issue 1 , January 2010 , pp. 88 - 97
Copyright
Copyright © The Paleontological Society 

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