Phyllocarida, Packard, 1879

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 : 22

Phyllocarida gen. et sp. indet. ( Fig. 16A )

A single probable phyllocarid representative has been collected at Ly Hoa, in an isolated block near locality 4 ( Fig. 1C ). Despite its questionable taxonomic assignment and its poor preservation, it is mentioned here in order to call the attention of future investigators. The specimen ( Fig. 16A ) was found on the bedding plane of a white, silty level, interbedded with sandstone beds. It was possibly complete initially, yet disarticulated, and its carapace, as well as its abdomen and appendages are strongly weathered. Its assignment to phyllocarid crustaceans rests on the ornament preserved on a small part of the carapace, which exhibits only narrow, undulating and anastomosing longitudinal ridges (a, Fig. 16A ), of either ceratiocaridid or rhinocaridid type ( Rolfe 1969; Racheboeuf 1994). Another carapace fragment of the same specimen, which may possibly belong to the posterior margin of the carapace, looks like a rounded margin and bears two short, laterally flattened spines, suggestive of the carapace margin of several representatives of the genus Echinocaris . Two, flattened fragments with a possibly spinose margin (b, Fig. 16A ) may be abdominal segments.

Figures

FIG. 16. — Arthropoda,Ly Hoa Formation,?Lower Devonian,Ly Hoa,Quang Binh Province,Vietnam:A, Phyllocarida gen. et sp. indet. (BT 207r); a, carapace fragment; b, possible abdominal segments; B, C, Sinocaris-like carapace; B, camera lucida drawing of BT 203q; C, camera lucida drawing of BT 203s (C1, part; C2, counterpart). Scale bars: 5 mm.

FIG. 1. — Locality map of the Ly Hoa area, Central Vietnam: A, location of the Ly Hoa area; B, geological map of the Ly Hoa area (from Janvier et al. 1997, modified); C, detailed map of the outcrops and quarries in the vicinity of the Ly Hoa pass. 1, “locality 1”, near the Da Nhay natural monument; 2, “locality 2”, bomb impact crater along the Ha Tinh-Quang Binh road; 3, outcrop along the roadcut of the Ly Hoa Pass; 4, active quarries, yielding notably Vukhuclepis? galeaspid, petalichthyid, and phyllocarid remains; 5, abandoned quarries, with ferruginous layers yielding antiarch and youngolepidid remains.