New record of the trimerellid brachiopod Gasconsia, a rare Silurian lazarus taxon

Abstract

Gasconsia Northrop, 1939, is a rare trimerellid that appears in the Upper Ordovician (Ashgill) and then reappears in the Upper Silurian (Wenlock/Ludlow) (Hanken and Harper, 1985; Popov and Holmer, 2000). This note is the first documented report of Gasconsia from the type Ludlow of the Welsh Borderland. Gasconsia transversus (Salter) occurs in the Lower Bringewood beds (upper part of Gorstian stage) in a small quarry on the north side of the Holloway to Upper Millichope road, directly opposite the entrance to Millichope Park (grid ref. SO 52748911). The material consists of internal and external molds of one brachial valve and one articulated individual (Fig. 1). This species was described as Obolus Davidsoni var. transversus [Salter MS] by Davidson (1866) from the Wenlock (Homerian stage) of the Dudley and Woolhope areas of the English Midlands and Welsh Borderland. Davidson and King (1874) subsequently referred to it as Dinobolus transversus (Salter), and Cocks (1978), in selecting a lectotype of transversus, retained its assignment to Dinobolus. However, illustrations of transversus in Davidson (1866, pl. 5, figs. 1-6) and Davidson and King (1874, pl. 18, fig. 12) clearly show that it belongs in Gasconsia rather than Dinobolus.