Rowellella sp.

Holmer, Lars E. & Biernat, Gertruda, 2002, Urban and Peri-urban small and medium-size Enterprise Development for sustainable Vegetable Production and Marketing Systems, Acta Palaeontologica Polonica 47 (1), pp. 141-156 : 143-144

Rowellella sp.

Fig. 1M–O .

Material.—Total of 1 dorsal valve and 2 indeterminate valves. Figured dorsal valve: RM Br133763 (W = 0.66, L = 1.10); indeterminate valve: RM Br133764.

Remarks.—The fragmentary preservation of the scant material makes exact taxonomic discrimination difficult. Biernat (1973) distinguished two unnamed species, based on differences in shape and size, but this cannot be confirmed based on the available material. The surface ornamentation consists of ridge−like fila, superposed on growth lamellae, but the typical pitted micro−ornamentation of Rowellella is not present presumably due to poor preservation. Popov and Holmer (1994) described similarly poorly preserved material of Rowellella from the Tremadoc of Sweden, as well as from the early Arenig of Kirgizia (Holmer et al. 2000). Some similar and poorly preserved specimens of Rowellella were also described by Bednarczyk (1986) from early Arenigian beds in northern Poland.

Figures

Fig. 1. A–L. Leptembolon cf. lingulaeformis (Mickwitz). A, E. Ventral valve RM Br133755, interior (A, × 18) and oblique lateral view of interior (E, × 32). B. Ventral valve RM Br133756, exterior; × 23. C, G, J. Ventral valve RM Br133757, interior (C, × 15), oblique lateral view (G, × 23) and detail of pseudointerarea (J, × 54). D, I. Dorsal valve RM Br133758, oblique lateral view of interior (D, × 30) and detail of pseudointerarea (I, × 46). E. Ventral valve RM Br133759, oblique lateral view of exterior; × 30. H. Dorsal valve RM Br133760, oblique lateral view of interior; × 26. K. Ventral valve RM Br133761, interior; × 37. L. Ventral valve RM Br133762, oblique lateral view of umbo; × 92. M–O. Rowellella sp. M. Dorsal valve RM Br133763, oblique lateral view of juvenile dorsal valve; × 41. N, O. Indeterminate valve RM Br133764, oblique lateral view (N, × 84) and detail of ornamentation (O, × 110). P–R. Orbithele ceratopygarum (Brøgger). P, Q. Ventral valve RM Br133765, exterior (P, × 37) and detail of larval shell (Q, × 100). R. Ventral valve RM Br133766, oblique lateral view of ventral valve exterior; × 80. All specimens from the Tremadoc chalcedonites, Wysoczki.