Corbicularia noongdensis, Racheboeuf & Phuong & Hung & Feist & Janvier, 2006

Racheboeuf, Patrick, Phuong, Ta Hoa, Hung, Nguyen Huu, Feist, Monique & Janvier, Philippe, 2006, Brachiopods, crustaceans, vertebrates, and charophytes from the Devonian Ly Hoa, Nam Can and Dong Tho formations of Central Vietnam, Geodiversitas 28 (1), pp. 5-36: 26-28

publication ID

http://doi.org/10.5281/zenodo.5376089

persistent identifier

http://treatment.plazi.org/id/038E87AE-E77C-8322-FF58-E2E9FE7175F5

treatment provided by

Marcus

scientific name

Corbicularia noongdensis
status

n. sp.

Corbicularia noongdensis   n. sp. ( Fig. 18 View FIG A-I)

HOLOTYPE. — External mould of a ventral valve ( BT 231 b; Fig. 18B View FIG ).  

ETYMOLOGY. — From the name of the type locality, the

Noong De Pass. LOCALITY AND AGE. — Noong De (Bactelemi) Pass, Ky

Son district, Nghe An Province, Central Vietnam. Middle part of the Nam Can Formation, Givetian-Frasnian ( MX 1, Fig. 17A View FIG ).

MATERIAL EXAMINED. — More than 50 decalcified isolated internal and external moulds of both valves, and external moulds of articulated shells, most of them tectonically distorted. Some specimens are illustrated in Figure 18A View FIG , C-I.

DIAGNOSIS. — Small shell with a maximum of 32 ventral costellae, increasing by intercalation only, with 6-7 costellae per mm along anterior margin; two pairs of orthomorph, high-angled spines.

DESCRIPTION

Very small shell (maximum length: 2.4 mm; corresponding width: 3.2 mm), weakly transverse in outline, with moderately and regularly convex ventral valve, and weakly concave dorsal valve. Maximum width at hinge line. Ventral interarea flat, apsacline with small, prominent pseudodeltidium; dorsal interarea low and hypercline with small chilidium. Ornament of low, rounded costellae with a maximum of 32 costellae along the commissure; six to seven costellae per mm along anterior margin. Costellae increasing by intercalation only in ventral valve, and by bifurcation only in dorsal one. Radial ornament crossed by very thin concentric fila.Two orthomorph, high-angled, and symmetrically displayed spines on each side of beak, respectively at about 0.7 mm and 1.8 mm from beak.

Ventral valve interior with myophragm not extending anteriorly beyond one third the valve length. Diductor scars poorly impressed; adductor scars oval to semi-elliptical in outline, well limited.Teeth not observed. Periphery of the valve impressed by the outer ornament.

Dorsal valve interior with a very short breviseptum originating anteriorly to a narrow, elongate cardinal process pit. Cardinal process not observed. Two radial rows of stouter endospines, spinose accessory septa, on each side of the breviseptum, and reaching anterior margin of the valve. Inner socklet ridges long and narrow, extending laterally parallel to hinge line. Anderidia very small but well defined, anteriorly divergent at about 90°. Muscle scars indistinct. Surface of the valve covered with relatively coarse, spaced and radially arranged endospines.

COMPARISON

By its external morphology, and its internal features as well, this new species from Vietnam is close to Corbicularia parisi ( Racheboeuf, 1981)   and C. goasquellouensis ( Racheboeuf, 1981)   , both from the Frasnian of the Massif Armoricain, France. However, C. noongdensis   n. sp. exhibits a smaller shell, with thinner radial ribs (6 to 7 per mm). C. parisi   has four costellae per mm along the anterior margin, and Corbicularia goasquellouensis   five costellae in the same interval. Corbicularia noongdensis   n. sp. has two spines on each side of the beak, like C. parisi   , but the ventral costellae increase by intercalation only in C. noongdensis   n. sp., instead of increasing by bifurcation, with rare intercalations towards the shell margin, in C. parisi   . The ornament is quite similar to that of C. goasquellouensis   , but the radial ribs are thinner, and the Armorican species has only one pair of spines instead of two.

DISTRIBUTION

To date, Corbicularia noongdensis   n. sp. is only known from the Givetian-Frasnian of Central Vietnam. Other species of the genus Corbicularia   are all late Givetian or Frasnian. In North Timan and the Volga-Ural region of Russia, Corbicularia menneri (Lyaschenko, 1958)   occurs in the upper part of the lower Frasnian. C. cracoviensis Balinski, 1979   has been described from the lower Frasnian (Lower asymmetricus zone) of the Debnik Anticline, in southern Poland. In the western Massif Armoricain, C. parisi   is restricted to the upper part of the Kergarvan Formation (uppermost Givetian, hermanni-cristatus zone), while C. goasquellouensis   ranges through the Traonliors Formation (lower Frasnian, asymmetricus zone).