- 1909 Platystrophia ponderosa Foerste, Bull, Sci. Lab., Denison Univ., vol. 14, p. 225, pl. 4, fig. 14.
- 1912 Platystrophia ponderosa Foerste, Ohio Naturalist, vol. 12, p. 453, pl. 22, fig. 11.
- 1919 Platystrophia ponderosa McEwen, Proceedings of the National Museum, vol. 56, p. 427-428, pl. 49, figs. 1-5, pl. 50, figs. 4-7; pl. 51, figs. 1-5; pl. 52, fig. 1-3, 7-10.
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Map point data provided by iDigBio.
- C4 Sequence (Arnheim)
- C3 Sequence (Mount Auburn, Corryville)
- C2 Sequence (Bellevue, Fairmont)
- C1 Sequence (McMicken)
Identification in Hand Sample:
V. ponderosa is the among the most distinctive species in the Upper Ordovician in the Cincinnati area. It has a distinctly large size, quadrate (rectangular) outline, and crural cavity in the brachial valve. Its valves are distinctly thickened. The central plications number 4, with the plications numbering 7-9 on the lateral slopes.
- Large size, thick shell
- 7-9 plications on either side
- 4 plications on fold
- Quadrangular outline
Vinlandostrophia ponderosa from McMillan Formation of Brown County, Ohio (OUIP 874)
- Vinlandostrophia ponderosa (Foerste, 1909) Plate II, figures 17-20; Figure 2A,B; Table 7
- Holotype: USNM 78814, Pl. II, figs 17, 18, complete shell, Maysvillian, Upper Ordovician, Indiana, USA.
- Diagnosis: Vinlandostrophia species having shells quadrate to subquadrate in outline, with maximum width in anterior third of shell; radial ornament of angular costate, three costae in sulcus, four on fold and six to eight costae on flanks of both valves; ventral sulcus and dorsal fold prominent, shallow to moderately deep; septalium V-shaped.
- Remarks: This species is the most abundant brachiopod taxon amongst Upper Ordovician shelly faunas in the Cincinnati area; it is also represented by numerous specimens in Upper Ordovician brachiopod collections in museums in North America and Europe. Alberstadt (1979, p. 17) stated that specimens are easily recognizable because of their distinctively large size, quadrate outline, and presence of a cruraliumlike structure in the brachial valve. He also noted that the presence of a V-shaped cross-section for the sessile septalium as illustrated in Fig. 2B and Pl. II, fig. 20 (see also discussion above) in some specimens is not obvious. This question also arises with comparison of individuals assigned to this species and illustrated in some publications (e.g. Schuchert & Cooper 1932, pl. XII, figs 25, 27). We investigated this uncertainty with reference to numerous specimens from collections in the USGS. We conclude that this is due to the different preservation modes of the studied specimens. Specimens showing a strong degree of shell dissolution of the dorsal internal surface (interiors of such valves aresharply crenulated and adductor scars are invisible) are characterized by a clearly visible V-shaped sessile septalium (Pl. II, fig. 20). Whereas in specimens (both old and young individuals) showing low amounts of shell dissolution, the features of the cardinalia are covered by additional secondary shell (Pl. II, fig. 19) and thus are less visible. However, in another species of Vinlandostrophia, the U-shaped form in the cross-section of the sessile septalium is clearly recognizable (Fig. 2G; Pl. III, fig. 2).
- Articulate brachiopod. This form differs from all other species of Platystrophia in the Cincinnatian by the size and thickness of the shell. Interior pedicle shows deep muscle impression and triangular pedicle opening.
- Large size; greatly thickened valves; quadrangular outline; fold prominent, rounded, with usually 4 plications; 7-9 plications on lateral slopes.
- Foerste describes his species as follows: Platystrophia ponderosa is characterized by large size, thick valves, and quadrangular outline; the brachial (dorsal) valve has a prominent, though rather rounded, median fold, usually occupied by four plications. The sinus on the pedicle valve is broad, not very deep, and is occupied usually by three plications. The lateral plications vary from seven to nine. Sometimes six occupy the median fold. The shell is greatly thickened interiorly, especially around the deep muscular scar in the pedicle (ventral) valve.
- Occurrence. Maysville group: Bellevue, Madison, and numerous other localities in Indiana; Oldham County, Kentucky. Leipers: Stockett Hill, White Creek post office. Leipers Creek, etc., Tennessee, Bellevue, Cincinnati, and numerous localities in Ohio.