A New Genus of Pennsylvanian Fish (Crossopterygii, Coelacanthiformes) from Kansas

BY

JOAN ECHOLS

University of Kansas
Lawrence
1963


University of Kansas Publications, Museum of Natural History

Editors: E. Raymond Hall, Chairman, Henry S. Fitch,
Theodore H. Eaton, Jr.


Volume 12, No. 10, pp. 475-501, 7 figs.
Published October 25, 1963

University of Kansas
Lawrence, Kansas

PRINTED BY
JEAN M. NEIBARGER, STATE PRINTER
TOPEKA, KANSAS
1963

New Genus of Pennsylvanian Fish (Crossopterygii, Coelacanthiformes) from Kansas

BY

JOAN ECHOLS

INTRODUCTION

In 1931 and 1932, H. H. Lane, C. W. Hibbard and W. K. McNown collected the specimens that Hibbard (1933) described and made the basis of two new species. These were from the Rock Lake shale member of the Stanton formation, six miles northwest of Garnett, Anderson County, Kansas. In 1954, from a locality (KAn-1/D, see page 480) approximately one fourth mile southwest of the first locality, specimens were quarried by F. E. Peabody, R. W. Wilson and R. Weeks. In 1955 R. R. Camp collected additional blocks of Rock Lake shale from this second locality. Study of all of the materials from the above mentioned localities reveals the existence of an hitherto unrecognized genus of coelacanth. It is named and described below.

I wish to thank Prof. Theodore H. Eaton, Jr., for suggesting the project and for much helpful advice. I am indebted to Dr. E. I. White of the British Museum (Natural History) for furnishing a cast of the endocranium of Rhabdoderma elegans (Newberry) for comparison, and to Drs. Donald Baird (Princeton University), Bobb Schaeffer (American Museum of Natural History) and R. H. Denison (Chicago Natural History Museum) for loans and exchanges of specimens for comparison. I am grateful to Dr. Bobb Schaeffer for advice on the manuscript. Mr. Merton C. Bowman assisted with the illustrations. The study here reported on was made while I was a Research Assistant supported by National Science Foundation Grant G-14013.

SYSTEMATIC DESCRIPTIONS

Subclass CROSSOPTERYGII

Superorder Coelacanthi

Order Coelacanthiformes

Suborder DIPLOCERCIDOIDEI

Family Diplocercidae

Subfamily Rhabdodermatinae, new subfamily

Discussion.—Because of the great differences in endocranial structure between the Devonian and Pennsylvanian coelacanths, they are here placed in new subfamilies. The two proposed subfamilies of the family Diplocercidae are the Diplocercinae and the Rhabdodermatinae. The Diplocercinae include those coelacanths having two large unpaired bones in the endocranium (at present this includes Diplocercides Stensiö, Nesides Stensiö and Euporosteus Jaekel). The subfamily Rhabdodermatinae is composed of coelacanths having reduced endocranial ossification, as described in detail above, and now including Rhabdoderma Reis and Synaptotylus n. g.

Members of this subfamily differ from those of the subfamily Diplocercinae in having several paired and unpaired elements in the sphenethmoid region of the endocranium, instead of only one larger ossification. They differ from those of the suborder Coelacanthoidei in the retention of basipterygoid processes.

Synaptotylus is more closely related to Rhabdoderma than to the Diplocercines because the anterior portion of the endocranium contains only a basisphenoid, parasphenoid, and probably ethmoids. The sphenethmoid region was certainly not a large, unpaired unit as in the Diplocercines. Probably the posterior part, the otico-occipital region (not known in Synaptotylus), was much more nearly like that of Rhabdoderma, which consisted of unpaired basioccipital and supraoccipital, and paired prootics, exoccipitals, and anterior and posterior occipital ossifications (Moy-Thomas, 1937: figs. 3, 4). Moy-Thomas (1937:389) points out that in Rhabdoderma the occipital region is "considerably more ossified" than in any coelacanths other than the Devonian forms. Berg (1940:390) thought that the Carboniferous coelacanths should be placed in a separate family because they did not have two large, unpaired bones in the endocranium. Rhabdoderma and Synaptotylus represent another stage in evolution of the endocranium in coelacanths, and, if classification is to be based on endocranial structure, then this stage (represented by the two genera) may later be given family rank as Berg suggested. Because Rhabdoderma and Synaptotylus have only part of the sphenethmoid region ossified and because they retain basipterygoid processes, they are considered to be related and are included in the subfamily Rhabdodermatinae.

Synaptotylus, new genus

Diagnosis.—Late Pennsylvanian fishes of small size, having the following combination of characters: on basisphenoid, knoblike antotic processes connected by a low ridge to basipterygoid processes; entire ventral surface of parasphenoid toothed; anterior margin of parasphenoid notched and no evidence of hypophyseal opening. Dermal bones of skull smooth or with low, rounded tubercles and striae; fronto-ethmoid shield incompletely known but having one pair of large rectangular frontals with posterolaterally slanting anterior margins; intertemporals large, the lateral margins curving laterally; postorbital triangular, apex downward; subopercular somewhat triangular; squamosal carrying sensory canal that curves down posteriorly and extends onto a ventral projection; opercular generally triangular; supratemporals elongate, curving to fit lateral margin of intertemporals; circumorbital plates lightly ossified. Palatoquadrate complex consisting of endopterygoid and ectopterygoid (both toothed on medial surface), quadrate, and metapterygoid, the latter smooth and having widened border for articulation on anterodorsal margin. Pectoral girdle consisting of cleithrum and clavicle (supracleithrum not seen); small projection on medial surface of posterior portion of cleithrum; horizontal medial process on clavicle. Pelvic plate bearing three anteriorly diverging apophyses, and one denticulate ventromedian process for articulation to opposite plate. Lepidotrichia jointed distally, but not tuberculated. Scales oval, having posteriorly converging ridges on posterior exposed parts.

The name refers to the most distinctive