Kyrtatrypa barnimi, Halamski, 2013

Halamski, Adam T., 2013, Frasnian Atrypida (Brachiopoda) from Silesia (Poland) and the age of the eo-Variscan collision in the Sudetes, Geodiversitas 35 (2), pp. 289-308 : 294-295

Kyrtatrypa barnimi n. sp.

( Figs 2-4 )

Atrypa reticularis – Dames 1868: 496, 497. —? Gunia 1966: 310, pl. 8: 9.

Atrypa ex gr. reticularis – Grocholski 1969: 246 (e.p.), non pl. 5: 2.

TYPE MATERIAL. — Articulated shell MB.B.2425, holotype. 58 paratypes: MB. B 2416-2418 , 2419 c, 2420, 2422, 2426, 2427 ; PIG 139.II.35-37; MGUWr 191s, 323s, 5361s.1-7 and fragments MGUWr 5359s, 5361s, 5363s.

ETYMOLOGY. — In honour of Wilhelm Barnim Dames (1843-1898), collector of a large part of the type material.

TYPE HORIZON. — Pogorzała Formation, Late Frasnian.

TYPE LOCALITY. — Abandoned quarry “Lake Daisy”, Mokrzeszów (Oberkunzendorf), Świebodzice Depression, Sudetes, Poland.

STRATIGRAPHIC AND GEOGRAPHIC RANGE. — Only type locality and horizon.

DIAGNOSIS. — Kyrtatrypa with slightly to markedly dorsibiconvex shell and moderately fine ornamentation. Spiralia of about eight whorls.

DESCRIPTION

Shell approximately as wide as long (width to length ratio from 0.86 to 1.15; mean value 1.01, N=23), rounded through subrectangular to subtriangular in outline, slightly to markedly dorsibiconvex, up to 35.7 mm wide and to 27.0 mm thick. Maximum width and thickness at ⅓ to ½ of the shell length from the umbo. Anterior commissure rectimarginate in young specimens to uniplicate in adults, its deflexion rounded to triangular in outline, very low to low, occupying ⅓ to ½ of the shell width. Ventral interarea anacline; ventral beak strong, incurved, appressed to the dorsal valve. Dorsal interarea and beak not visible. Ribs undulose, relatively fine, straight, 5-6(-7) per 5 mm at anterior commissure, new ones arising by bifurcation on both valves. Growth lamellae fine. Frills ( Fig. 3 ) up to 16 mm long.

Interior ( Fig. 4 ): shell relatively thick walled, with a thick tertiary layer. Ventral valve: pedicle callist thick and continuing anteriorly for about 5 mm; teeth stout, with strong lateral lobes; dental nuclei absent. Dorsal valve: median septum moderately strong; a weak cardinal process in form of a pad, enclosed within the cardinal pit; hinge plates stout; socket plates thin, arcuate; crural base strong, jugal process rather long and stout; spiralia of about 8 thin whorls.

DISCUSSION

This species is assigned to Kyrtatrypa Struve, 1966 on account of its dorsibiconvex to aequibiconvex shell and presence of frills. Its internal structures are very similar to those of Kyrtatrypa culminigera Struve, 1966 ( Copper 2002: fig. 947e-g), except for a higher number of spiralia whorls (11) in the latter. The internal structures of Kyrtatrypa balda Havlíček, 1987 ( Havlíček 1987: fig. 2) are also similar to those of the described species.

Kyrtatrypa barnimi n. sp. differs from K. brandonensis ( Stainbrook, 1938) from the Lower Frasnian Cedar Valley beds of Iowa in its finer ornamentation ( Stainbrook 1938). Kyrtatrypa ? teicherti ( Coleman, 1951) , a poorly known taxon from the Frasnian of Western Australia, has a flatter ventral valve and finer ornamentation ( Coleman 1951; Grey 1977); the generic assignment of this species is uncertain ( Ma et al. 2006: 798). The nearest species seems to be the early Givetian Kyrtatrypa n. sp. from Błonia Sierżawskie near Świętomarz (see Halamski & Segit 2006) in the northern part of the Holy Cross Mountains ( K. pauli , nomen nudum, Halamski 2004:text-fig.31-33; pl. 6: 8, 7: 1-4; = Kyrtatrypa sp. sensu Zapalski 2005) from which the species described here differs in less convex dorsal valve and more convex ventral one, smaller apical angle, and more dense ornamentation.

The genus Kyrtatrypa was once supposed to occur up to the end of the Frasnian stage ( Copper 1998: fig. 1); however, its Late Frasnian occurrences have appeared doubtful ( Copper 2002: 1396) due to imprecise biostratigraphic dating (Racki 1998: 396) and uncertain taxonomy ( Ma et al. 2006: 798). As a matter of fact, Frasnian representatives of Kyrtatrypa are scarce, including only K. brandonensis from Iowa and K. teicherti from the Canning Basin (see above for details); both taxa come from lower parts of the Frasnian. Consequently, K. barnimi n. sp. from the Late Frasnian represents probably the last known representative of the genus and, additionally, the first Frasnian species from Europe.

It may be noted that this species is distinguished from co-occurring Pseudogruenewaldtia tschernyschewi Rzhonsnitskaya, 1960 by the presence of frills (present in several representatives of the subfamily Atrypinae Gill, 1871 , absent in the Pseudogruenewaldtiinae Rzhonsnitskaya, Yudina & Sokiran, 1997; see Copper 2002).

Genus Pseudogruenewaldtia

Rzhonsnitskaya, 1960

TYPE SPECIES. — Pseudogruenewaldtia tschernyschewi Rzhonsnitskaya, 1960 . Timan, Late Frasnian.

Figures

FIG. 2.— Kyrtatrypa barnimi n.sp.,Mokrzeszów (Oberkunzendorf),Late Frasnian:A-E, paratype,articulated shell MB.B 2417.2;F-J, paratype, articulated shell MB.B 2422.5; K-O, holotype,articulated shell MB.B 2425;P-T, paratype,articulated shell MB.B 2422.2;U-Y, paratype, articulated shell MB.B 2422.6; Z-DD, paratype, articulated shell MB.B 2422.1. A, F, K, P, U, Z, dorsal views; B, G, L, Q, V, AA, ventral views; C, H, M, R, W, BB, lateral views; D, I, N, S, X, CC, posterior views; E, J, O, T, Y, DD, anterior views. Scale bar: 1 cm.

FIG. 3. — Kyrtatrypa barnimi n. sp. Specimen with preserved frills in ventral view.MB.B.2418.1.Mokrzeszów (Oberkunzendorf),Late Frasnian. Scale bar: 5 mm.

FIG. 4. — Kyrtatrypa barnimi n. sp., serial sections of the specimen MB.B.2422.10; Mokrzeszów (Oberkunzendorf), Late Frasnian. Internal structures: c, pedicle callist; cp, cardinal pit; cb, crural base; j, jugal plate; pc, cardinal process; s, spiralium; sp, socket plate; t, tooth. Scale bar: 5 mm.