Coveenia davidsoni ( de Koninck, 1887 )

Mottequin, Bernard & Simon, Eric, 2017, New insights on Tournaisian-Visean (Carboniferous, Mississippian) athyridide, orthotetide, rhynchonellide, and strophomenide brachiopods from southern Belgium, Palaeontologia Electronica 37 (3), pp. 1-45 : 35

Coveenia davidsoni ( de Koninck, 1887)

Figures 4 , 29.1-4

v* 1887 Retzia davidsoni de Koninck , p. 92, pl. 22, fig. 10.

? 1923 Retzia davidsoni de Koninck ; Demanet, p. 189, pl. 11, fig. 87.

Holotype. De Koninck (1887, p. 92) stressed on the fact that this species is based on a single poorly preserved specimen of the Dupont collection ( RBINS a5508; Figure 29.1-4 ) from Dréhance (Waulsort Formation, Ivorian), which has to be considered as the holotype by monotypy.

Remarks. The limited material available for study cannot permit to fully describe this species, which is currently only represented by the holotype and assigned to Coveenia on the basis of its external features. This incomplete specimen is small (ca. 11 mm in width), wider than long, biconvex, and bears height high, rounded costae on the dorsal valve, which are separated by similar grooves. De Koninck (1887) presumably assumed that the holotype was identical to the two specimens from England identified as Retzia ulothrix by Davidson (1861, pl. 18, figs. 14-15). Alvarez and Brunton (2000) assigned the first specimen illustrated by Davidson (1861, pl. 18, fig. 14) to their new species Coveenia tilsleia whereas the second (Davidson, 1861, pl. 18, fig. 15) may belong to another species (see Alvarez and Brunton’s (2000) synonymy list of C. tilsleia ). However, de Koninck’s (1887) species is less rostrate than C. tilsleia , but further material is required to provide a full description of this poorly known species and a detailed comparison with C. ulothrix . The specimen identified as Retzia davidsoni by Demanet (1923), originating from Sosoye (Waulsort Formation) has not been traced.

Occurrence. Coveenia davidsoni is only known from the Waulsortian mud mounds (Waulsort Formation, Tournaisian) in southern Belgium (Dinant sedimentation area).

Systematic position of Retzia intermedia de Koninck, 1887

Among the three new species briefly described by de Koninck (1887) and assigned to Retzia King, 1850 ( R. davidsoni (= Coveenia davidsoni , see above), R. multiplicata (= Hustedia multiplicata , see Mottequin et al., 2015), and R. intermedia ), the third is definitely not an athyridide, but a rhynchonellide on the basis of its external morphology. For purposes of nomenclatorial formality, the only specimen (RBINS a5510) illustrated by de Koninck (1887, pl. 22, figs. 11-15) from Furfooz ( Figures 2-3 ) is selected herein as the lectotype of Retzia intermedia de Koninck, 1887 ( Figure 29.5-9 ). The other specimens cited by de Koninck (1887) were not traced in the RBINS collections. The lectotype could be a juvenile, likely of one of the numerous costate rhynchonellide species occurring within the Waulsortian mudmounds from Belgium and illustrated by de Koninck (1887), Fraipont (1908), and Demanet (1923), but its precise identification requires their revision, which is well beyond the scope of this paper.

Figures

FIGURE 2. Schematic geological map of southern Belgium with location of the fossiliferous localities (modified from de Béthune, 1954). Abbreviations: D, Dréhance; F, Furfooz; G, Germany; HSMOTS, Haine-Sambre-Meuse Overturned Thrust Sheets; L, Grand Duchy of Luxemburg; N, The Netherlands; S, Sosoye.

FIGURE 3. Late Tournaisian sedimentation areas in the Namur-Dinant Basin (not palinspastically restored; modified from Hance et al., 2001; Poty et al., 2006; Poty, 2016) with location of the fossiliferous localities. Abbreviations: ASA, Avesnois sedimentation area; CSA, Condroz sedimentation area; D, Dréhance; DSA, Dinant sedimentation area; F, Furfooz; G, Germany; HSA, Hainaut sedimentation area; L, Grand Duchy of Luxemburg; N, The Netherlands; NSA, Namur sedimentation area; S, Sosoye; VSA, Visé–Maastricht sedimentation area.

FIGURE 4. Distribution of the athyridides, orthotetides and strophomenides described and/or discussed herein within the essentially carbonate Tournaisian and Visean succession of southern Belgium (see text). Stratigraphy, lithostratigraphy (incompletely represented here for the Hainaut and Visé–Maastricht sedimentation areas; formations and members are in roman and italic letters, respectively), and biostratigraphy are adapted from Poty et al. (2002, 2006, 2014). The lenticular Vignobles Member is not represented here as it is rarely developed (it is comprised between the Vaulx Member of the Tournai Formation and the Antoing Formation). Note that the “Grande Brèche” is an informal stratigraphic unit resulting from the dissolution of evaporitic levels in the Grands Malades Formation; other brecciated horizons occur in the Lives Formation.

FIGURE 29. 1-4, Coveenia davidsoni (de Koninck, 1887), RBINS a5508 (holotype), articulated specimen in ventral, dorsal, lateral and posterior views, from Dréhance, Waulsort Formation (Tournaisian, Ivorian). 5- 9, ‘Retzia’ intermedia de Koninck, 1887 (here considered as a rhynchonellide species), RBINS a5510 (lectotype), articulated specimen in ventral, dorsal, lateral, posterior and anterior views, from Furfooz, Waulsort Formation (Tournaisian, Ivorian). Scale bars equal 2 mm.