Sycidium haikouense Z. Wang, 1976

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 : 31-32

Sycidium haikouense Z. Wang, 1976 ( Fig. 20 )

The charophytes come from about 25 g of the matrix of the fish remains just described.It was impossible to extract well preserved specimens, because the fossils are extremely fragile and completely pyritized, but rubber cast of their external, natural mould allows a reconstruction of their shape ( Fig. 20 ). The form represented in this sample can be referred to Sycidium haikouense Z.Wang (Sycidiaceae) . This species is known from the Donggangling Formation of South China, which is correlated to the Givetian of Europe (Z. Wang 1976). The size range and overall morphology of the fructification of S. haikouense ( Table 1), which is ovoid in shape and slightly thinner in its upper part, as well as the number of its vertical elements (ribs) and of polygonal cells per rib, are also shared by the form described here from Cau Rong. Only the length/width ratio is higher by one tenth of units in the only specimen from Vietnam on which it could be measured, and this suggests for the latter a slightly more elongated overall shape of the fructification, yet this does not preclude its attribution to S. haikouense .

The presence of S. haikouense in the Dong Tho Formation increases the fossil record of Devonian charophytes along the northern margin of the Gondwana, which already included the floras from Queensland ( Australia; Feist et al. 2000), South China (S. Wang & Chang 1956; Z. Wang 1976; Zhang et al. 1978; Z. Wang & Lu 1980; Z. Wang et al. 1980; Hu & Zeng 1982; Li & Zhou 1982), Iran (Feist & Grambast-Fessard 1985; Mistiaen et al. 2000, and southern France ( Feist & Feist 1997). In addition, this is the first record of fossil charophytes from Vietnam, at any rate in the Palaeozoic.

Figures

FIG. 20. — Sycidium haikouense Z.Wang, 1976, lower part of the Dong Tho Formation,Givetian,Cau Rong,Minh Hoa District,Quang Binh Province,Vietnam,elastomer cast of an utricle (BT 208c);A, apical view; B, lateral view. Scale bars: 0.1 mm.