Bivalve mollusks from the Maxville Limestone in Ohio

Ohio Journal of Science, The, Sept, 2007 by Richard D. Hoare

ABSTRACT. Bivalve mollusks are a common component of the Chesterian Maxville Limestone in Ohio, although not as abundant as the brachiopods. A number of taxa were found preserved as internal molds making identification difficult. The new species Leptodesma (Leptodesma) rhysema, Limipecten lamellus, Astartella clinata, and Sanquinolites bekitoensis are among the 29 taxa now known from the formation. The shale unit near the top of the formation contains mytilaceans and abundant pectenaceans dominated by Aviculopecten winchelli Meek, 1875, the latter with inarticulate brachiopod epibionts.

INTRODUCTION

Collections from eight localities have produced a significant increase in the known bivalve fauna of the Mississippian (Chesterian) Maxville Limestone (Fig. 1). Previous work by Whitfield (1882, 1891, 1893), Morse (1911) and Hoare and others (1988) described seven taxa. An additional 22 taxa are included herein. Corrections of previous taxonomic assignments are given in the discussion on previous work and in the systematic section. The location of Whitfield's bivalve specimens is unknown, presumably lost. Six specimens collected by Morse are in the collections of the Orton Geological Museum, The Ohio State University. The purpose of this study is to describe and illustrate the known bivalve fauna and to update the taxonomic assignment of previously described taxa.

MATERIALS AND METHODS

Collections from the limestone and shale were obtained by the use of hammer and sledge in the field as well as finding weathered out specimens. Further preparation was done under a microscope using a vibratool and fine needles. In extracting specimens from the limestone the shell commonly adhered to the matrix and in chipping the matrix away from specimens the shell usually broke up as it was exposed. Samples of weathered limestone were boiled in a solution of water and Quaternary O which liberated numerous small specimens, mainly preserved as internal molds. Many of these were not well enough preserved to allow specific identification.

Specimens from the shale unit were all disarticulated valves. Shell material was preserved, although very thin and incomplete. These specimens were coated with a thin layer of Styrofoam dissolved in benzene to preserve the shell material and to protect the impression of the shell in the shale matrix.

All specimens were coated with a thin layer of magnesium oxide for photographic purposes to enhance the ornamentation. Photography was done with a Leica camera.

Collections made by the late M. T. Sturgeon and students, Ohio University, and the late A. S. Horowitz, Indiana University, were given to the author to supplement the collections at Bowling Green State University.

PREVIOUS WORK

The four species of bivalves described by Whitfield (1882, 1891, 1893) include: Pinna maxvillensis Whitfield = Pinna (Sulcatopinna) missouriensis Swallow, 1863; Schizodus chesterensis Meek and Worthen, 1860 = Schizodus sp; Allorisma andrewsi Whitfield = Wilkingia andrewsi (Whitfield, 1882); and Allorisma maxvillensis Whitfield = Wilkingia maxvillensis (Whitfield, 1882). To this list Morse (1911) added one species: Cypricardella oblonga Hall, 1858a = Edon oblonga (Hall, 1858a). A short note by Hoare and others (1988) added two species in describing color patterns on Aviculopecten winchelli Meek, 1875, and Streblopteria sp. from the shale near the top of the Maxville.

Hyde (1953) described numerous Mississippian bivalves from Ohio but did not include the Maxvillle Limestone.

EPIFAUNA

The lack of shell material on most bivalve specimens precludes the preservation of any epibionts that may have been attached. The brachiopods in the Maxville Limestone have a common and varied epibiont fauna present on the shells (Hoare, 2003). It is likely that specimens of bivalves also had attached epibionts.

In several instances pedicle valves of Orbiculoidea cf. O. keokuk (Gurley, 1884) were found preserved on the valves of Aviculopecten winchelli Meek, 1875, in the upper black shale unit (Fig. 2.1-2.3) It is possible that the larvae of these inarticulate brachiopods suvived by becoming attached to the firm substrate of the bivalve shell. A brachial valve of Oehlertella pleurites (Meek, 1875) was also found in the shale but not on a bivalve shell (Fig. 2.4). Several small fragments of brachial valves were also found in the shale.

RESULTS

The bivalve fauna of the Maxville Limestone is much more diverse than previously known. An additional 22 taxa are described herein including:

Nuculopsis aff. N. shumardana (Hall, 1858a)

Nuculopsis sp.

Polidevcia cf. P stevensiana (Girty, 1910)

Palaeoneilo sp.

Phestia cf. P pandoraeformis (Stevens, 1858)

?Solemya (Jania) sp.

Modiolus (Modiolus) fountainence Weller, 1916

M. (M.) waverliensis (Herrick, 1888)

?ambonychiid gen. and sp.

Myalinella sp.

Leptodesma (Leptodesma) rhysema n. sp.

L. (L.) cf. L. (L.) matheri Elias, 1957

Aviculopecten sp. A

Aviculopecten sp. B

Limipecten lamellus n. sp.

Limipecten sp.

Streblochondria sp.

Schizodus cf. S. chesterensis Meek and Worthen, 1860