Cincinnetina meeki

Classification
Phylum: Brachiopoda
Class: Rhynchonellata
Order: Orthida
Family: Dalmanellidae
Genus: Cincinnetina
Species: Cincinnetina meeki (Miller, 1875)

http://i1.wp.com/www.ordovicianatlas.org/wp-content/uploads/2013/11/C.meeki_paleoeco.png?resize=300%2C300

Taxonomic Details

Formerly named: Onniella meeki, Dalmanella meeki

Stratigraphic Occurrences

c.meeki_strat

Geographic Occurrences

Map point data provided by iDigBio.

Stratigraphic Distribution

  • C5 Sequence (Waynesville)
  • C4 Sequence (Arnheim)

Identificiation in Hand Sample
C.meeki_identifier2

  • Outline subcircular
  • Average size of 18 mm long and 22 mm wide
  • Fold on ventral valve
  • Small beak
  • Radiating striae

Cincinnetina meeki from Waynesville formation of Warren County, Ohio (OUIP 1636)

Published Descriptions

Davis (1998):

  • Articulate brachiopod. Differs from O. multisecta, by rectangular outline, and greater size and thickness. Waynesville; peaks in Ft. Ancient. (Walker, 1982, has referred to both O. meeki and O. multisecta to the genus Dalmanella. Onniella and Dalmanella are difficult to tell apart, and it may well be that these two species actually belong in a separate genus, as yet unnamed)

Walker (1982): (Under Dalmanella meeki)

  • Collections of D. meeki used herein come from the Bull Fork Formation, 23 to 111 ft above the base of the unit, at the County Line Section in the Orangeburg and Maysville East Quadrangles. The Bull Fork is mainly Richmondian in age (Peck, 1966), and the collections would correspond to Hall’s (1962) designation of D. meeki as being of Richmondian Age. However, earlier workers, including Foerste (1909a), thought that D. meeki occurred as low as the “Fairmount” (equivalent to part of the Fairview Formation of Peck, 1966), which is Maysvillian in age. Hall (1962) gave the range of D. multisecta as Edenian- Maysvillian and that of D. meeki as Richmondian, without discussing the reasons for his disagreement with earlier workers. Only a thorough study of taxonomy and stratigraphic distribution based on many collections can resolve the problem.
  • Medium to large size, generally less than 18 mm long, 22 mm wide; outline subcircular to transverse. Dorsal valve commonly more convex and sulcate. Cardinalia extremely thickened in mature specimens, cardinal process greatly inflated and filling space between brachiophore bases.

Miller (1875): (Under Orthis meeki)

  • Shell small, plano-convex, rather depressed, transversely truncatosuboval , the length being about five sixths its breadth; hinge line, perhaps, always a little shorter than the greatest breadth of the valves; lateral margins generally rounding to the hinge, most prominent at, or a little behind, the middle, and rounding to the front, which is usually somewhat straightened, or very faintly sinuous at the middle; or, presents a regular semi-circular outline.
  • Dorsal valve nearly flat, or slightly convex on each side of a shallow, mesial sinus, that commences very narrow at the beak, and usually widens rather rapidly to the front; beak very small, scarcely projecting beyond the edge of the area, and not incurved; area low at the middle, and narrowing off to nothing at the lateral extremities of the hinge, slightly arched and directed obliquely backward; foramen very small, and filled by the cardinal process. Interior very shallow, and provided with a slender mesial ridge that extends about halfway forward from the hinge, between the muscular impressions, which are not usually well defined; scars of posterior pair of adductor muscles smaller, and usually deeper, than the anterior, and situated close back under the brachial processes; those for the anterior pair three or four times the size of the posterior, suboval in form, and extending to near the middle of the valve; cardinal process very small and trifid; brachial process, comparatively, rather stout and prominent; internal surface having the radiating striae of the exterior rather distinctly impressed through, as it were, in consequence of the thinness of the shell, and finely granular, the granules being apparently connected with the punctuate structure of the shell.
  • Ventral valve compressed convex, the greatest convexity being near, or a little behind, the middle, along a more or less prominent undefined ridge, that sometimes, but not always, imparts a subcarinate appearance to the central and umbonal regions; beak small, projecting somewhat beyond that of the other valve, and with its sharply defined edges sloping to the lateral extremities of the hinge, directed and archedobliquely backward with the beak; foramen having near the form of an equilateral triangle, but rather narrowed upward to the apex of the beak, and partly occupied by the cardinal process of the other valve. Interior showing the teeth to be moderately prominent; concavity for the muscular impressions very shallow, small, somewhat bifid anteriorly, and not defined by a very distinct marginal ridge; scars of divaricator muscles apparently narrow, and situated on each side of shallow mesial depression, which seems to include, far back at its posterior end, those of the very small adductors, merely separated from each other by a hairline; impressions of ventral adductor muscles apparently wider and shorter than those of the divaricators; striae and fine granules of the interior as in the other valve.
  • Surface of both valves ornamented by numerous, distinct, radiating striae, that usually bifurcate about three times between the beak and free margins; [posterior lateral striae so strongly curved that a part of them run out on the hinge line. Numerous, very minute, regularly disposed, concentric lines may also be seen by the aid of a magnifier, most distinctly defined in the furrows between the much larger radiating striae; while a few distant, sub-imbricating, stronger marks of growth are usually seen in adult shells. Length medium sized, mature specimen, 0.60 inch; breadth, 0.75 inch; convexity, 0.25 inch.

McFarlan (1931): (Under Dalmanella meeki)

  • This species is a larger and more robust form than D. multisecta. Muscular impressions deep set. Dorsal sinus well marked. Striae variable in coarseness, measuring as low as 6 or 7 in 5 mm. along the anterior margin to twice that many. Width typically about 18mm, length about 0.8 width.
  • Cumings lists this species (1908, faunal chart) from as low as the upper part of the McMillan. It is common in the Arnheim and Waynesville.