Taxonomy, distribution, and paleoecology of holothurian (echinodermata) sclerites in upper Pennsylvanian cyclothem shales, north-central Texas and south-central Kansas

Date

1996-08

Journal Title

Journal ISSN

Volume Title

Publisher

Texas Tech University

Abstract

Holothurian sclerites have been found in abundant numbers in Upper Pennsylvanian (Missourian-Virgilian) cyclothem shales at three sites in the midcontinent region (Texas and Kansas) of North America. These microfossil assemblages comprise a number of different sclerite sieve plate, wheel, hook, table, and rod/cross morphotypes. Their excellent preservation and abundant numbers (> 36,000 identified specimens) provide an opportunity to document morphological variation of form species and to reevaluate form species taxonomy. Morphological analysis has identified twenty-one form species that represent twelve paragenera and seven parafamilies. Four of the form species are provisionally identified and are not assigned specific names. This study reports the second ever recovery of the form species Theelia hexacneme. Form species Paleochiridota radiata is re-established. This is the first report of Clavallus spicaudina and Protocaudina hexagonaria from the Pennsylvanian; the first report of Priscopedatus subhexagonus from North America; and the first report ofMercedescaudina triperforata, Praeeuphonides multiperforata, and Tetravirga sinensis from the Pennsylvanian and from North America.

The quality of the sclerite assemblages also allows form species joint occurrences to be used to develop a multi-element model of occurrences. Statistical analyses indicate that all form species pairs, with one exception, have occurrence correlations that do not support a species association. Thus, a monotypic sclerite model for form species taxonomy is considered valid for classification, and is interpreted as a reasonable approximation of Upper Pennsylvanian holothurian species.

The recovery of these sclerite assemblages from the midcontinent Upper Pennsylvanian cyclothems allows correlation of sclerite abundances and form species distributions to the different shale lithofacies that comprise cyclothems. Utilizing the common oxygen-level model as a primary control factor on lithofacies and fossil communities, a number of form species biofacies are recognized by overall abundance of sclerites and by relative form species diversity. A form species distribution model for upper Pennsylvanian cyclothems is proposed. The sequence of biofacies corresponds well with the cycle of lithofacies that are recognized and can be interpreted within the oxygen-level model. Differences in biofacies between the sections suggest that, in addition to oxygen level, other factors controlled holothurian occurrence.

Description

Keywords

Plants-- Fossis -- Texas, Paleobotany -- southwestern States, Fossils -- Identification, Holothurians, Plants-- fossel -- Kansas, Paleobotony -- Pennsylvanian

Citation