Vinlandostrophia annieana

• Medium to large in size for the genus, subquadrate to subrectangular outline
• Cardinal extremities vary from rounded to right angle to acute
• Specimens have 4 plications on fold and 3 in sulcus, flanks have 6 to 11. Plications broad with well rounded tops
• Inner faces of brachiophores concave with inward projecting ledges
• P. annieana is easily differentiated from P. ponderosa by its smaller size, slightly more subrectangular outline compared to a more quadrate outline in P. ponderosa

• Species medium to large for the genus, subquadrate to subrectangular outline, cardinal extremities vary from rounded to right angle to acute. Lateral margins more typically curved leading smoothly into curved anterior margin. Biconvex in lateral profile with brachial valve slightly deeper, some specimens almost twice as deep; rate of curvature decreases in anterior half of shell and is distinctly less than in posterior half. Most specimens have 4 plications on fold and 3 in sulcus; flanks have 6 to 11. Plications broad with well rounded tops, interplication troughs well rounded also; plications tend to “flare out” in anterior parts of shell. Growth lines absent in most specimens.

  Brachial interarea orthocline to slightly anacline, curved and about one half as long as pedicle inter-area. Notothyrium open, triangular. Cavity deep, some elevated high above valve floor. Inner faces of brachiophores concave with inward projecting ledges along lower parts, helping to form floor of cavity. Cardinal process a low ridge that extends full length of cavity, slightly thicker anteriorly. Brachiophores thick, curved upward and outward, pointed. Sockets triangular pits, poorly defined in most. Inside of valve crenulated throughout. Posterior adductor scars circular in outline, anterior scars somewhat triangular with gently curved margins. Pedicle interarea apsacline, curved. Delthyrium triangular, open; walls of cavity sloping slightly outward. Dental plates thin to thick, join margins of ellipsoidal muscle field; field extends about one fourth length of valve and defined by thin to moderately thick rim. Interior of valve crenulated. The largest specimens of this species slightly resemble intermediate size of P. ponderosa . However P. annieana is easily differentiated from P. ponderosa by its smaller size, slightly more subrectangular outline compared to a more quadrate outline in P. ponderosa. Internally P. annieana lacks a cruralium-like structure so characteristic of the brachial valves P. ponderosa.

  Platystrophia annieana Foerste is an abundant species in the uppermost part of the Kentucky Ordovician. Almost all of the large collections in the area are from the Preachersville Member of the Drakes Formation in Kentucky and from Dillsboro Formation of Indiana. Well preserved specimens and suites also occur in the lower parts of the Drakes.

McEwen (1919):

• In the Bulletin of the Dension University (vol. 16, 1910, pl. 6, fig. 14 a, b, c) Doctor Foerste has figured a species to which Mr. U.P. James had given the catalogue name Platystrophia annieana. Figure a shows a form in which the hinge line forms the greatest width; figure c shows one in which the length of the hinge line about equals the width across the middle. Figure b shows a ventricose form with a rounded fold so little elevated as to hardly disturb the even convexity of the brachial (dorsal) valve.
• I have before me about 70 specimens from the Waynesville and Liberty formations of Ohio, Indiana, and Kentucky, which undoubtedly belong to the species which he figured. In most specimens the hinge line about equals the width across the middle. I have, however, many in which the hinge line is longer than this width.
• The low rounded fold is occupied by four and the sinus by three nearly equal plications. The sinus is moderately deep. The slopes are occupied by 10 and 11 plications. Those of the brachial (dorsal) valve are convex with a slight concavity next to the cardinal angles. The slopes of the pedicle (ventral) valve are concave.
• Measurements. 33.5 mm along the hinge line, 28.4 mm wide across the middle, 18.5 mm high, 14.6 mm thick, 14 mm sinal width, 8.4 mm sinal depth, 2.5 mm fold depth.
• Occurrence. Richmond group: Waynesville Formation: Clarksville, Fort Ancient, Waynesville, Ohio; Bardstown, Kentucky. Liberty Beds: Jefferson County, Kentucky, and Clark County, Indiana. Whitewater Formation: Richmond, Indiana.
• Plesiotypes. Cat. Nos. 39041, 65651, 65664, U.S.N.M.

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