Dagnachonetes sp.

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 : 30

? Dagnachonetes sp.

LOCALITY AND AGE. — Ba Nuong ( Fig. 17B ), Minh Hoa district, Quang Binh Province, Central Vietnam. Upper part of the Dong Tho Formation, Frasnian.

MATERIAL EXAMINED. — Some 30 isolated valves, all variably mineralized and distorted, but strongly weathered, have been collected from the Ba Nuong locality.

DISCUSSION

Due to the poor preservation of the available specimens, none of the internal features could be studied and described. The shell is transverse in outline, with its maximum width (about 15 mm) at mid-length. The longitudinal profile is weakly to moderately arched. Spines are not observed. Only the external ornament could be observed on some incomplete external moulds. It is composed of low, rounded, sinuous costellae, increasing mainly by bifurcation on the ventral valve; the costellae are crossed by very thin, undulating concentric fila. Such a kind of ornament strongly recalls that of the genus Dagnachonetes which is mainly known from Poland, Russia, France, Spain, and South China in Eifelian to lower Frasnian beds.

Phylum VERTEBRATA Linnaeus, 1778 Class GNATHOSTOMATA Gegenbaur, 1874 Subclass PLACODERMI McCoy, 1848 Order ANTIARCHA Cope, 1885 Suborder EUANTIARCHA Janvier & Pan, 1982 Family BOTHRIOLEPIDIDAE Cope, 1886 Genus Bothriolepis Eichwald, 1840

Figures

FIG. 17. — Locality map: A, Muong Xen area, Nghe An Province (MX 1, brachiopod locality of Noong De Pass); B, Quy Dat and Cau Rong areas, Quang Binh Province (CR1, antiarch and charophyte-bearing locality of Cau Rong; CR2, brachiopod-bearing locality of Cau Rong; BN1, brachiopod locality of Ba Nuong).