Cleiothyridina tenuilineata ( Rowley, 1900 )

Sun, Yuanlin & Baliński, Andrzej, 2011, Silicified Mississippian brachiopods from Muhua, southern China: Rhynchonellides, athyridides, spiriferides, spiriferinides, and terebratulides, Acta Palaeontologica Polonica 56 (4), pp. 793-842 : 815-816

Cleiothyridina tenuilineata ( Rowley, 1900)

Figs. 4D–F, J , 16B, 17 .

1900 Athyris tenuilineata ; Rowley 1900: 264, pl. 5: 31–33.

1967 Cleiothyridina tenuilineata (Rowley) ; Carter 1967: 344–347, pl. 16: 8a–13e; text−fig. 21.

1979 Cleiothyridina tenuilineata ( Rowley, 1900) ; Nalivkin 1979: 155, pl. 64: 5.

1987 Cleiothyridina tenuilineata (Rowley) ; Carter 1987: 60, pl. 20: 1–12.

Material.—69 complete shells and nearly 200 separate valves from sample MH 1.

Remarks.—The specimens are characterised by their almost equally biconvex, lenticular shell, usually circular to slightly pentagonal outline, and rectimarginate anterior commissure. The shell width is equal to or slightly less than the shell length, but slightly wider specimens can also be found. The largest specimens attain about 14–15 mm in width. They have no evident median fold or sulcus. The ventral interior shows well developed sub−parallel dental plates ( Fig. 17C ). The dorsal median myophragm extends more than one−third to one−half of the valve length and divides two pairs of well marked, subovate adductor scars (see Figs. 16B, 17H ). The anterior margin of the adductor scars is very close to the mid−point of the dorsal valve. The triangular outer hinge plates are postero−laterally bounded by thickened, postero−ventrally projecting cardinal flanges. The conjunct inner hinge plates are subtrapezoidal and pierced apically by a relatively small dorsal foramen. However, the median ridge on the cardinal plate, which is well developed in Cleiothyridina deroissyi described above, is usually absent in the present species or weakly marked in the most posterior region of the plate ( Fig. 17F ). Spiralium, jugum, and jugal stem are preserved in a broken shell shown on Fig. 17N . The external ornamentation consists of dense concentric, partly overlapping growth lamellae which on better preserved specimens may also be fringed with flattened spine−like outgrowths ( Fig. 17E, K, O ); the latter seem more closely but less regularly spaced than in C. deroissyi described above. It is noteworthy that generally the spine−like outgrowths are rarely observable in our specimens whereas short concentric lamellae are the most common.

The general lenticular shell shape and proportion of its external dimensions strongly suggest that the specimens belong to Cleiothyridina tenuilineata ( Rowley, 1900) , described from the Mississippian of North America ( Carter 1967, 1987). Externally the specimens from Muhua are also almost identical with Cleiothyridina fimbriata (Phillips, 1836) described from late Tournaisian and Viséan strata of the British Isles (see Brunton 1984: 58–59). As Brunton (1984: 58) noted the strikhttp://dx.doi.org/10.4202/app.2010.0106

ing feature of the shell of C. fimbriata is its spinose ornamentation which consists of very long “spines” attaining up to 5 mm in length. Although the spines on our specimens may be also quite long (up to about 2 mm in specimen shown on Fig. 17K ) they seem to be less regularly spaced than in the species from the British Isles.

Stratigraphic and geographic range.—According to Carter (1967, 1987) Cleiothyridina tenuilineata is widely distributed in the late Kinderhookian and early Osagian of the central and southwestern USA, as well as in the Banff Formation (Early Carboniferous) of Canada. This species was also recorded from Kynov horizon (lower Tournaisian) of the Urals ( Nalivkin 1979). Comparable specimens were recorded as C. cf. tenuilineata by Sour−Touvar et al. (2005) from lower Mississippian of northeastern México. Tournaisian of Muhua section, southern China.

Figures

Fig. 4. Shell damage in silicified brachiopods from the Tournaisian Muhua Formation, southern China. A. Drilled ventral valve of Subglobosochonetes gedongguensis Sun and Baliński, 2008, PKUM02−0390, in exterior (A1) and interior (A2) views. B, C. Two shells of Cleiothyridina deroissyi (Léveillé, 1835) with boreholes, PKUM02−0391 (B) and PKUM02−0392 (C), in dorso−lateral (B) and ventral (C) views, respectively. D, E. Two damaged shells of Cleiothyridina tenuilineata (Rowley, 1900) with boreholes, PKUM02−0393 (D) and PKUM02−0394 (E), in dorsal (D1, E1) and enlarged (D2, E2) views. F. Damaged ventral valve of Cleiothyridina tenuilineata (Rowley, 1900), PKUM02−0395, in general exterior (F1) and more detailed (F2) views. G, H. Two shells of Crurithyris cf. nastus Brunton and Champion, 1974 with boreholes, PKUM02−0396 (G) and PKUM02−0397 (H), in general dorsal (G1, H1) and detailed (G2, H2) views. I. Shell of Cleiothyridina deroissyi (Léveillé, 1835), PKUM02−0398, with a few small−sized boreholes in dorsal valve. J. Shell of Cleiothyridina tenuilineata (Rowley, 1900) with a series of small−sized boreholes, PKUM02−0399, in ventral (J1) and enlarged (J2) views. K, L. Two dorsal valves of Cesifornix carteri Baliński and Sun, 2010a, PKUM02−0400 (K) and PKUM02−0401 (L), bored from the exterior (K1, L1) and showing “blister” deposits in the interior (K2, L2) as a response to borings. M. Dorsal valve of Schellwienella sp., PKUM02−0317, showing numerous external borings of a barnacle (M1) and internal “blisters” sealing the damages (M2) (illustrated by Baliński and Sun 2008: fig. 21D; M2 new photograph). N. Koskinoid perforations in posterior region of ventral valve of Serratocrista sp., PKUM02−0402. Samples GB/GT (A, N), MH1 (B–G, I–L), and MH2 (H, M).

Fig. 17. Athyridoid brachiopod Cleiothyridina tenuilineata (Rowley, 1900) from the Tornaisian Muhua Formation, southern China. A. Complete juvenile shell, PKUM02−0451, in dorsal (A1), ventral (A2), lateral (A3), and anterior (A4) views. B. Dorsal valve, PKUM02−0452, exterior (B1) and interior (B2). C. Interior of ventral valve, PKUM02−0453, with preserved broken off umbonal region of the dorsal valve (cardinalia viewed from below), in general (C1) and enlarged (C2) views. D. Juvenile shell, PKUM02−0454, in dorsal (D1), ventral (D2), lateral (D3), anterior (D4), and posterior (D5) views. E. Comlete shell, PKUM02−0455, with adhered some silica deposits in dorsal view. F. Well preserved cardinalia, PKUM02−0456. G. Shell, PKUM02−0457, in dorsal (G1), ventral (G2), lateral (G3), and anterior (G4) views. H. Dorsal valve, PKUM02−0458, in interior (H1), the same slightly inclined anteriorly (H2), and enlarged (H3) views. I. Shell, PKUM02−0459, in dorsal (I1), ventral (I2), lateral (I3), anterior (I4), and posterior (I5) views. J. Complete shell, PKUM02−0460, in dorsal view. K. Shell, PKUM02−0461, with preserved spine−like outgrowths in dorsal (K1) and enlarged (K2) views. L. Complete shell, PKUM02−0462, in dorsal (L1), ventral (L2), lateral (L3), and posterior (L4) views. M. Complete shell, PKUM02−0463, in dorsal view. N. Damaged shell, PKUM02−0464, viewed from the anterior showing preserved spiralium with labelled details. O. Enlargement showing well preserved surface micro−ornamentation; note concentric lamellae desintegrating to spine−like outgrowths (arrowed), PKUM02−0399; see also Fig. 4J. All from sample MH1.