Cleiothyridina obmaxima (McChesney, 1861)
brachiopod
originally placed in Athyris

Mississippian
Warsaw Formation
Meramecian Series
St. Louis County, Missouri

   

Note the round predator boring (drill hole) on the pedicle
valve near the umbro which was probably formed by the
radula of a carnivorous snail.

Special thanks to Dr. Thomas W. Kammer
for his identification and the following text.

Athyris and Cleiothyridina are closely related. Athyris has sheet-like
extensions of the growth lamellae that are widely spaced, whereas
Cleiothyridina has fringe-like extensions (or flat spines) of the
growth lamellae that are closely spaced. In both these genera the
growth lamellae extensions are often broken off, but the spacing of the
lamellae is distinctive for each genus. This specimen appears to be a
good match for Cleiothyridina.

Cleiothyridina obmaxima was originally described as Athyris obmaxima
McChesney, 1861. In 1914 Stuart Weller (IL State Geol. Survey,
Monograph 1, The Mississippian Brachiopoda of the Mississippi Valley
Basin) assigned this species to Cleiothyridina.

Dr. Thomas W. Kammer

References:

The Mississippian Brachiopoda of the Mississippi Valley Basin
(Monograph 1 - Plates), Plates by Stuart Weller, Illinois State
Geological Survey, Urbana - 1914
      Plate LXXIX pages 176-177
The Mississippian Brachiopoda of the Mississippi Valley Basin
(Monograph 1 - Text), Text by Stuart Weller, Illinois State
Geological Survey, Urbana - 1914
      Pages 475-476

Williams, A. et al. 2002. Treatise on Invertebrate Paleontology, Part H,
Brachiopoda, Revised. Volume 4: Rhynchonelliformea (part). The Geological
Society of America Inc. and the University of Kansas. 1688 pp. Genus
Cleiothyridina BUCKMAN pp. 1510.

Classification

PHYLUM BRACHIOPODA
SUBPHYLUM RHYNCHONELLIFORMEA
CLASS RHYNCHONELLATA
ORDER ATHYRIDIDA
SUBORDER ATHYRIDIDINA
SUPERFAMILY ATHYRIDOIDEA
FAMILY ATHYRIDIDAE
SUBFAMILY CLEIOTHYRIDININAE
GENUS CLEIOTHYRIDINA BUCKMAN, 1906, nom. nov. pro Cleiothyris KING, 1850
CLEIOTHYRIDINA OBMAXIMA (MCCHESNEY, 1861)

Thanks to Dr. Steven R. Hill for the Treatise reference and classification.

Viewer Comments:

Note the fine spines which are a characteristic of this genus.

Note the round predator boring (drill hole) on the pedicle
valve near the umbro which was probably formed by the
radula of carnivorous snail seeking a nice brachiopod morsel.

Alan Goldstein

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