Hoarepora parrishi (Worthen, 1890)

Hoarepora parrishi (Worthen, 1890)

( Figs 2, 3)

Conocardium parrishi Worthen, 1890: 112 , pl. 20, fig. 7; Keyes, 1894: 124, pl. 46, fig. 6a, b; Beede, 1900: 164, pl. 20, fig. 9; Sayre, 1930: 109, pl. 9, figs. 20, 20a–20c; Bird, 1968: 144, pl. 13, fig. 3.

not Pseudoconocardium parrishi – Hoare, Sturgeon, Kindt, 1978: 1033, pl. 2, figs. 1–7.

not Pseudoconocardium parrishi – Hoare, Sturgeon, Kindt, 1979: 60, pl. 17, figs. 1–6, pl. 18, fig. 1.

Oxyprora parrishi – Hoare, Mapes, Yancey, 2002: 9, fig. 7.1; Rogalla, Amler, 2006d: 44.

Conocardium missouriensis Roundy in Girty, 1915: 353, pl. 28, figs. 3, 3a–3c; Sayre, 1930: 109; Bird, 1968: 144

Pseudoconocardium missouriensis – Hoare, Sturgeon, Kindt, 1978: 1033, pl. 2, figs. 8, 9; Hoare, Sturgeon, Kindt, 1979: 61, pl. 18, figs. 2, 3.

Oxyprora missouriensis – Hoare, Mapes, Yancey, 2002: 13, figs. 7.2–7.17

Type material. Holotype ISGS 13284 .

Type locality. Locality unknown, Missourian Drum ? Limestone, Pennsylvanian; Kansas City, Missouri, USA .

Material examined. Russian Federation: (1) Ryazan’ Region, Kasimov district, Akishino quarry, base of section, locality PIN 4471 View Materials /85, Middle Pennsylvanian , Moscovian Stage , Myachkonian Substage , Korobcheevo Formation , eight specimens; (2) Moscow Region, Schelkovo quarry, base of limestone section, locality PIN 4471 View Materials /2, Upper Pennsylvanian, Gzhelian Stage , Rusavkinian Substage , Amerevo Formation , one specimen .

Distribution. Morrowan – Missourian interval in the North American Midcontinent Basin. Myachkovian – Rusavkinian interval on the Russian Platform.

Description. Rostrum subparallel to dorsal axis. The aperture in the region of the frontal segment is wide, evenly narrowing in the region of the intermediate segment. The right and left edges of the aperture bear at least eight marginal denticles. The frontal segment is separated from the intermediate segment by a shallow and relatively wide depression; the ventral segment differs in the type of ornamentation, sometimes ventral segment slightly elevated above the intermediate segment. Primary carina cord­like, slightly curved. On most specimens with the outer surface of the shell preserved, the primary carina is broken off, and in its place, there is a lunulazone of moderate width with rough, transverse, almost straight growth lines. The rostral area is triangular, generally slightly concave. The edge of the rostral field is sharply wavy, and deep U­shaped bends are formed between the ends of the radial ribs. The contour line along the sharply protruding ends of the radial ribs is almost straight. The ornamentation on the frontal and intermediate segments is the same, the radial and commarginal ribs are high and narrow, forming rectangular cells. Radial ribs are taller and more massive. The number of radial ribs is at least 10; second­order additional radial ribs may be present. The ventral segment has at least four radial ribs. The radial ribs on the ventral segment are massive, noticeably higher than the comarginal ones. The commarginal ribs are thin and frequent, hence, the cells on the ventral segment are narrower than on the intermediate and frontal segments. Primary carina is ornamented with commarginal ribs of the ventral segment. The rostral field is ornamented with massive cord­like radial ribs. The ribs are separated by wide U­shaped intercostal spaces. The external surface of the inner layer of the shell on the frontal and intermediate segments is ornamented with at least 11 wide radial ribs separated by narrow grooves. On the ventral segment, the width of the grooves is comparable to the width of the ribs. The number of ribs, at least four, increases with growth. On the rostral field, the radial ribs are low, narrow, without clear boundaries, covered with low tubercles, and grouped in pairs. Each pair is separated by a wide intercostal space. The increase in the number of radial ribs on the rostral field and ventral segment occurs along the primary carina.

Dimensions. Measurement methods and designa- tions are shown in Fig. 1 View FIG , pr – type of preservation: ol – external surface of outer layer. Dimensions in mm: ( Table 1).

Remarks. The external outlines of the shells of H. parrishi and H. tschernyschewi (Licharew, 1931) almost coincide. To compare the shells of the two species, measurements were taken of specimens of H. tschernyschewi : ( Table 2).

The similarity of these species in the proportions of the shell, in the sculptural elements of the outer and inner layers of the shell (with the exception of the ventral segment), may indicate a close or even direct relationship of the two species. Some specimens of both species exhibit scalloped varices [ Bird, 1968, pl. 13, fig. 3; Mazaev, 2015, figs. 2, a1, b2].

L p/ No. pr L p L vo L u L am L vm H W L vo K shl L u/ H K ahl L am/ L vm α

4471/85­257 ol 6.8 5.5 4.5 6.1 1.8 5,5 4.2 1.24 1.12 0.82 1.01 3.39 101º 4471/85­258 ol 5.5 4.0 3.5 4.4 1.3 4.0 – 1.38 1.19 0.88 1.08 3.38 97º 4471/85­264 ol 7.5 6.6 5.3 – – 5.5 4.0 1.14 1.28 0.96 – – 97º L p/

No. Pr L p L vo L u L am L vm H W L vo K shl L u/ H K ahl L am/ L vm α

5538/25­10 ol 11.4 10.4 7.9 10.4 3.5 8.8 9.3 1.10 1.24 0.90 1.05 3.0 107º 5538/25­11 ol 11.6 9.5 7.7 9.8 3.1 10 9.7 1.22 1.06 0.77 1.08 3.2 100º

H. parrishi superficially strongly resembles H. tschernyschewi , but differs in the Lam / Lvm ratio (3.38­3.39 and 3.0­3.2, respectively), the closer position of the commarginal ribs on the outer surface of the outer layer of the anterior part of the shell, espe- cially on the ventral segment, as well as wider paired radial ribs, separated by wide intercostal spaces on the outer surface of the inner layer.

H. parrishi differs from H. uralica Mazaev, 2023 in the Lam / Lvm ratio (3.38­3.39 and 1.94­2.29, respectively), the Kahl elongation coefficient (1.01­ 1.08 and 1.17­1.29, respectively), the wavy shape of the margin of the rostral field, almost cord­like paired radial ribs with pronounced tubercles on the rostral field of the outer surface of the inner layer.