Galeaspida, Halstead Tarlo, 1967

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 : 10-11

Galeaspida? gen. et sp. indet. ( Fig. 2 )

Locality 4 has yielded an assemblage of strange, tuberculate fragments, which recall the lateral margin of a galeaspid head shield. Each of the tubercles seem to correspond to an individual unit and there is a clear suture line between adjacent units, as in some galeaspids. The tubercles are generally costulate, slightly spiniform near the natural margin of the fragments and some of them, which are broken, seem to be hollow but crossed by scarce, thin fibres. In fact, thin sections reveal that the hard tissue itself is not preserved and that the fibres are probably internal casts of thin canals, filled with iron oxide. The aspect of this specimen recalls that of the tessellate exoskeleton fragment from the Lower Devonian of Qujing (Yunnan) referred to as an “asterosteid” rhenanid by Wang (1991), and which is more likely a fragment of a very large galeaspid. It is also strikingly similar to the exoskeleton of the unnamed Famennian galeaspid from Ningxia ( China), figured by Pan (1987: pl. 2:2). However, the specimen from Ly Hoa differs from the latter two by its slightly costulate tubercles. At any rate, the structure and aspect of these fragments rule out any Palaeozoic arthropod known to date.

Class GNATHOSTOMATA Gegenbaur, 1874 Subclass PLACODERMI McCoy, 1848 Order ANTIARCHA Cope, 1885 Suborder YUNNANOLEPIDOIDEI Zhang, 1978 Family YUNNANOLEPIDIDAE Zhang, 1978 Genus Vukhuclepis Janvier, Tong-Dzuy, Ta Hoa & Doan Nhat, 1997

Figures

FIG. 2. —?Galeaspida gen. et sp. indet., Ly Hoa Formation,?Lower Devonian, Ly Hoa, Quang Binh Province, Vietnam, fragmentary head shield (BT 207a). Scale bar: 10 mm.