Lamellosathyris lamellosa ( Léveillé, 1835 )

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 : 24-30

Lamellosathyris lamellosa ( Léveillé, 1835)

Figures 4 , 20-24 , Table 3

* 1835 Spirifer lamellosus Léveillé , p. 39, pl. 2, figs. 21-23.

1836 Spirifer squamosa Phillips , p. 220, pl. 10, fig. 21.

1843 Terebratula lamellosa Léveillé ; de Koninck, p. 299, pl. 20, fig. 5.

1868 Athyris (Spirifer) lamellosa (sic) Lév.; Dewalque, p. 333.

v 1887 Athyris lamellosa Léveillé ; de Koninck, p. 79, pl. 21, figs. 1-5.

v 1887 Athyris vittata de Koninck , p. 81, pl. 21, fig. 6-8.

v 1887 Athyris squamosa Phillips ; de Koninck, p. 80, pl. 21, figs. 9-10.

1980 Actinoconchus lamellosus (Léveillé) ; Brunton, p. 225, figs. 16-17.

Neotype. Specimen BMNH B20138 selected by Brunton (1980: p. 225, fig. 16).

Material. RBINS: besides the three specimens illustrated as Athyris lamellosa by de Koninck (1887, pl. 21, figs. 1-5), namely RBINS a5468 (pl. 21, figs. 1-3) ( Figure 20.11-15 ), RBINS a5469 (pl. 21, fig 4), and RBINS a5470 (pl. 21, fig. 5) ( Figure 21.19-23 ), complemented by those identified as Athyris vittata ( de Koninck,1887, pl. 21, figs. 6-8; RBINS a5472) ( Figure 23.8-12 ) and Athyris squamosa ( de Koninck, 1887, pl. 21, figs. 9-10; RBINS a5471) ( Figure 23.1-5 ), the RBINS material investigated includes 126 articulated specimens, six ventral and one dorsal valves; ULg.PA: 31 articulated specimens, one ventral and one dorsal valves.

Description. Shell large-sized (up to 51 mm in width), wider than long, transversely oval in outline, generally dorsibiconvex to rarely convexo-plane; hinge line shorter than maximum width; cardinal extremities rounded; anterior margin variably emarginate; anterior commissure uniplicate (rectimarginate to vaguely undulose in juveniles).

Ventral valve with prominent umbo; beak slightly overhanging hinge line, incurved; foramen small, permesothyrid ( Figure 21.1 ); palintropes well-developed, concave; sulcus originating inconspicuously in the posterior part of the valve, illdefined, shallow to deep (only in largest specimens), round-bottomed at front; tongue high, round to subrectangular in outline, perpendicular to commissural plane or bent dorsally.

Dorsal valve inflated with maximum convexity at anterior margin or near midlength and then decreasing near anterior margin; fold low to high, originating near midlength, and only well perceptible near the anterior margin, exceptionally with a very shallow, median groove ( Figure 21.13 ).

Shell covered by broad rugae, each about 3.5–4.5 mm wide at midlength (about 5–9 on 15 mm from the tip of the ventral umbo), but more crowded near the lateral and anterior commissures, and bearing thin to sometimes thickened growth lines (exact number unknown); radially corrugated shell flanges extending from rugae on both valves.

Ventral interior ( Figure 21.4-8 , 10-12 ) with thin, short dental plates converging dorsally then becoming subparallel anteriorly; teeth cyrtomatodont, stout, ovate; umbonal cavity large; lateral apical cavities poorly developed; muscle field clearly excavated posteriorly, large, subrounded in outline, with posteromedian elongate heart-shaped adductor scar enclosed laterally and anterolaterally by flabellate diductor scars extending up to 60 % of the unrolled length of the valve; posterolateral parts of the valve markedly pitted; mantle canals observed close to the anterior and lateral commissures.

Dorsal interior ( Figures 21.14-23, 22.2-4 ) with cardinal plate extending anteriorly ca. 13% (n = 2) of the valve length, subtrapezoidal in outline, pierced apically by a foramen; inner hinge plate wide, flat to convex; crural bases well-developed; dental sockets delimited by inner socket ridges clearly more developed than outer socket ridges; posterior bilobate cardinal flanges developed; adductor muscle scars variably excavated posterolaterally according to the specimens, but more obscure anteriorly, and medially divided by a low myophragm extending to 57 % of the valve length in the largest available specimen; spiral cones with at least 16 whorls (this number is slightly underestimated due to their poor preservation), with fimbriae; jugum composed anteriorly by a jugal saddle and posteroventrally by a thin jugal stem bifurcating into short accessory jugal lamellae ( Figure 22.5-13 ).

Dimensions ( Figure 24 , Table 3). The increasing of the shell length is proportional to the increasing of the shell width, and these parameters are quite stable through growth. The increasing of the thickness of the shell is a more variable parameter. The length/width ratio is significantly decreasing during growth indicating that the width increases quite more than the length in this species. On the contrary, the relation thickness/width to width is not significant. The very slight increasing of this ratio is due to the variability of the thickness variation through growth.

Remarks. Differences between Lamellosathyris lamellosa and other L. species (see Chen et al., 2003) have been discussed in detail by Carter (1967), Brunton (1980, 1984), Chen et al. (2003), and Sour-Tovar et al. (2005). However, contrary to Brunton’s opinion reported in Chen et al. (2003), L. lamellosa reaches a size similar to that of L. qaidamensis Chen et al., 2003 .

Athyris vittata de Koninck, 1887 from the Tournaisian Waulsort Formation is here considered as a synonym of Léveillé’s (1835) species. Only some specimens assigned to this species have been recovered from the de Koninck collection curated at the RBINS. The single specimen illustrated by de Koninck (1887, pl. 21, figs. 6-8) is here selected as the lectotype (RBINS a5472) ( Figure 23.8-12 ). Among the four additional specimens identified as A. vittata by de Koninck (1887) but not illustrated by him, only two are identical to the lectotype and thus have to be considered as paralectotypes RBINS a13132 ( Figure 23.13-17 ) and RBINS a13133 (a juvenile not illustrated herein). According to Demanet (1958), the macrofaunas from the Waulsortian mounds from southern Belgium were studied by de Koninck (e.g., 1885, 1887) at the request of the Belgian geologist Edouard Dupont, who wanted to show that the Waulsortian calcareous facies corresponded to an autonomous stage of the Dinantian as the Tournaisian and the Visean (see Lees [2006] and Groessens [2006]), and thus characterized by a distinct fauna. That is why almost all the brachiopods and bivalves recovered from these massive carbonate bodies were assigned to new species by de Koninck.

The material from Visé (Visé Formation) identified as Athyris squamigera ( Phillips, 1836) by de Koninck (1887) is illustrated here ( Figure 23.1-5 ) as well as another specimen ( Figure 23.6-7 ) from the same locality. Phillips’ species has been considered for a long time as a synonym of L. lamellosa (see Brunton, 1984).

Occurrence. Among the athyridide species recognized from the Tournaisian succession of the Tournai area, Lamellosathyris lamellosa seems to have the most extensive distribution worldwide. It is notably known from the Mississippian succession of Western Europe (e.g., Brunton, 1980, 1984; Mottequin, 2010), North Africa (e.g., Massa et al., 1974; Havlíček and Röhlich, 1987; Mergl and Massa, 1992; Mottequin et al., 2017), Mexico ( Sour-Tovar et al., 2005), the USA ( Carter, 1999), and Iran ( Gaetani, 1968; Bahrammanesh et al., 2011). In the Tournai area, Demanet (1958) reported L. lamellosa from the Orient Formation to the Vaulx Member of the Tournai Formation, i.e., from the latest Hastarian to the Ivorian. Demanet (1958) also reported its presence in various levels of the Tournaisian succession of southern Belgium, notably in the Yvoir and Waulsort formations, but the species is rare in the Visé Formation (Visean).

Superfamily NUCLEOSPIROIDEA Davidson, 1881

Family NUCLEOSPIRIDAE Davidson, 1881

Genus NUCLEOSPIRA Hall in Davidson, 1858

Type species. Spirifer ventricosus Hall, 1857 ; from the Lower Helderberg Group, Lochkovian, New York, USA.

Figures

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 10. Leptagonia cf. caledonica Brand, 1972 from Visé, Visé Formation (Visean, Warnantian). 1-5, 19-20, ULg.PA.2016.12.25/3, internal mould in ventral, dorsal, lateral, posterior and anterior views, and detail (SEM) of the muscular platform (latex cast). 6-10, 21-22, ULg.PA.2016.12.25/4, internal mould in ventral, dorsal, lateral, posterior, and anterior views, and detail (SEM) of the muscular platform (latex cast). 11-15, 23-24, ULg.PA.2016.12.25/5, internal mould in ventral, dorsal, lateral, posterior, and anterior views, and detail (SEM) of the muscular platform (latex cast). 16-18, ULg.PA.2016.12.25/6, distorted internal mould in dorsal view and close-up (SEM) of the muscular platform (latex cast). Scale bars equal 5 mm.

FIGURE 12. Schellwienella radialiformis Demanet, 1934 from the Tournai area, Tournai Formation (Tournaisian). 1-5, RBINS a5924, articulated specimen, almost complete, in ventral, dorsal, lateral, posterior, and anterior views. 6-10, RBINS a5928, articulated specimen, almost complete, in ventral, dorsal, lateral, posterior, and anterior views. 11-15, RBINS a5929, articulated specimen, almost complete, in ventral, dorsal, lateral, posterior and anterior views. 16-20, RBINS a5930 (lectotype), articulated specimen, almost complete, in ventral, dorsal, lateral, posterior, and anterior views. 21-25, RBINS a5926, almost complete articulated specimen (with a microconchid attached to the ventral valve, close to the anterior margin) in ventral, dorsal, lateral, posterior, and anterior views. Scale bars equal 10 mm.

FIGURE 20. Lamellosathyris lamellosa (Léveillé, 1835) from the Tournai area, Tournai Formation (Tournaisian). 1-5, RBINS a13119, juvenile articulated specimen in ventral, dorsal, lateral, posterior and anterior views. 6-10, RBINS a13120, articulated specimen in ventral, dorsal, lateral, posterior, and anterior views. 11-15, RBINS a5468, articulated specimen in ventral, dorsal, lateral, posterior, and anterior views. 16-20, RBINS a13121, articulated specimen in ventral, dorsal, lateral, posterior, and anterior views. 21-25, RBINS a13122, articulated specimen (with two microconchids attached to the right dorsal flank) in ventral, dorsal, lateral, posterior and anterior views. 26-30, RBINS a13123, articulated specimen in ventral, dorsal, lateral, posterior, and anterior views. Scale bars equal 10 mm.

FIGURE 21. Lamellosathyris lamellosa (Léveillé, 1835) from the Tournai area, Tournai Formation (Tournaisian). 1-2, RBINS a13124, partial posterior view of an articulated specimen showing the foramen and detail of the lamellose ornamentation in the anterior part of the dorsal valve. 3-8, RBINS a13125, complete ventral valve (juvenile) in external and internal views and detail of the teeth and the dental plates. 9-11, RBINS a13126, complete ventral valve in external and internal views and detail of teeth supported by almost vertical dental plates. 12, RBINS a13127, incomplete internal mould of ventral valve. 13-18, ULg.PA.2016.12.25/8, complete dorsal valve (with two microconchids attached to its internal surface (arrows), close to the anterior margin) in external and internal view and detail of the cardinalia. 19-23, RBINS a5470, incomplete dorsal valve in internal view and detail of the cardinalia. Scale bars equal 5 mm (1-2, 3-4, 10, 11), 2 mm (5-8, 20-23), 2.5 mm (15-18), 10 mm (9, 12-14).

FIGURE 22. Lamellosathyris lamellosa (Léveillé, 1835) from the Tournai area, Tournai Formation (Tournaisian). 1-4, RBINS a13128, almost complete dorsal valve in external and internal views, with close-up of the cardinal plate in ventral and oblique lateral views. 5-6, RBINS a13129, incomplete ventral valve with partly preserved spiralia and detail of the jugal saddle and the primary lamella. 7-10, RBINS a13130, articulated specimen with top of the ventral valve removed and details of the crura, spiralia and fimbria. 11-13, ULg.PA.2016.12.25/9, articulated specimen with ventral valve partly removed in general view and details of the top of the jugal stem and the same in oblique view. Scale bars equal 10 mm (1, 7, 11), 5 mm (2, 5), 1 mm (3-4, 10), 2 mm (6, 9), 2.5 mm (8, 12-13).

FIGURE 23. 1-7, Lamellosathyris lamellosa (Lévéillé, 1835) from Visé, Visé Formation (Visean, Warnantian). 1-5, RBINS a5471, distorted specimen in ventral, dorsal, lateral, posterior and anterior views. 6-7, RBINS a13131, incomplete ventral valve in ventral view and anterior views. 8-17, Athyris vittata de Koninck, 1887 (here placed in synonymy with Lamellosathyris lamellosa [Léveillé, 1835]) from Furfooz, Waulsort Formation (Tournaisian, Ivorian). 8-12, RBINS a5472 (lectotype) distorted specimen in ventral, lateral, dorsal, posterior, and anterior views. 13-17, RBINS a13132 (paralectotype), distorted and incomplete specimen in ventral, dorsal, posterodorsal, posterior, and lateral views. Scale bars equal 10 mm.

FIGURE 24. Scatter diagrams of Lamellosathyris lamellosa (Léveillé, 1835). N: number of specimens measured, r²: coefficient of linear regression. 1, Relation between shell width and length. 2, Relation between shell width and shell width/shell length ratio. 3, Relation beween shell width and thickness. 4, Relation between shell width and shell thickness/shell width ratio.