Avonia sp.

Carniti, Alessandro P., Porta, Giovanna Della, Banks, Vanessa J., Stephenson, Michael H. & Angiolini, Lucia, 2022, Brachiopod fauna from uppermost Visean (Mississippian) mud mounds in Derbyshire, UK, Acta Palaeontologica Polonica 67 (4), pp. 865-915 : 882-883

Avonia sp.

Fig. 8I .

Material.—One ventral valve internal cast: MPUM11872 RCC128-4a) from mud mound complex of Ricklow

Quarry, Monyash, Derbyshire, UK, Monsal Dale Limestone Formation, Brigantian, upper Visean.

Remarks.—The specimen is an internal cast of a small, elongated ventral valve. The valve is enrolled, with no fold or sulcus. The trail bears faint delayed costation; costae are low and narrow (3–4 per 5.0 mm anteriorly), with wide, rounded interspaces. The shell morphology, dimensions and ornamentation are that typical of species of Avonia , but because of the poor preservation the specimen is left under open nomenclature.

Genus Quasiavonia Brunton, 1966

Type species: Productus aculeatus Sowerby, 1814 , from Asbian– Brigantian , upper Visean, of Derbyshire, England .

Quasiavonia aculeata (Sowerby, 1814) Fig. 8J–N .

1809 Conchyliolithus Anomites ( aculeatus ); Martin 1809: 8, pl. 37: 9–10.

1814 Productus aculeatus ; Sowerby 1814: 156, pl. 68: 4.

1862 Productus aculeatus Sowerby, 1814 ; Davidson 1862 a: 166, pl. 33: 16–17,?18, non 19,?20. (cum syn.)

1914 Pustula aculeata Sowerby, 1814 ; Thomas 1914: 320, pl. 19: 9–10,?11. (cum syn.)

1951 Productus (? Krotovia ) aculeatus Sowerby, 1814 ; Muir-Wood 1951: 101, pl. 3: 3.

non 1966 Avonia (Quasiavonia) aculeata (Sowerby, 1814) ; Brunton 1966: 220, pl. 10: 8–17; pl. 11: 1–21.

1991 Quasiavonia aculeata (Sowerby, 1814) ; Brunton and Tilsley 1991: 292.

2000 Quasiavonia aculeata (Sowerby, 1814) ; Brunton et al. 2000, fig. 284: 2a–e.

Material.—Twenty articulated specimens: MPUM 11873 ( RCC 32-28a); MPUM 11874 ( RCC 49-28); MPUM 11875 ( RCK 17-2); MPUM 11876 ( RCC 1-8e, 25; RCC 2-12; RCC 32- 11; RCC 41-24; RCC 42-4a; RCC 43-73; RCC 48-13; RCC 49-1, 42; RCC 54-1; RCC 65G-15a, 15b; RCC 73-6, 23g; RCC 85-3d; RCK 15-55). Sixteen dorsal valves: MPUM 11877 ( RCC 49- 24); MPUM 11878 ( RCK 15-51); MPUM 11879 ( RCC 128-4b); MPUM 11880 ( RCC 1-8d; RCC 1B-20b; RCC 10-13; RCC 32-2, 17; RCC 42-12a; RCC 49-8,10a, 10b; RCC 68-51a,51b; RCC 85- 2); MPUM 11881 ( WI 1-27). Eight fragments: MPUM 11882 ( RCC 10-39b; RCC 14-8; RCC 49-11; RCC 65G-8c; RCC 68-9; RCC 128-23; RCC 300-12; RCK 15-35). All from mud mound complex of Ricklow Quarry, Monyash, Derbyshire, UK, Monsal Dale Limestone Formation, Brigantian (RCC-, RCK-), and Wensley Dale, Matlock, Derbyshire, UK, Eyam Limestone Formation, upper Brigantian, upper Visean ( WI 1).

Description.—Small, concavo-convex shell with subtriangular outline; cardinal margin wide; maximum width at shell mid-length. Ears small, convex; cardinal angles obtuse. Corpus cavity moderately deep. Anterior commissure rectimarginate. Ventral valve strongly and regularly convex. Dorsal valve concave. Fold-sulcus absent, trail long.

Ornamentation consists of irregular, imbricated lamellae, each 1.0–4.0 mm wide. Broad, faint delayed costae developed on ventral and dorsal trails, starting 8.0–9.0 mm from the umbo, with rounded interspaces. Lamellae cross ribs. Rounded spine bases roughly arranged in quincunx over ventral valve. Dorsal valve bearing similarly disposed rounded pits.

Remarks.—The specimens are close to the lectotype of Quasiavonia aculeata from the Brigantian, upper Visean, around Bakewell (Derbyshire), which was selected by Muir-Wood (1951: 102) and figured by Brunton et al. (2000). They are also similar to the specimens of Q. aculeata figured by Davidson (1862 a) and Thomas (1914) from the Visean of Derbyshire and the Isle of Man respectively. They differ from Quasiavonia minranensis Brunton in Brunton and Lazarev, 1997, in having spine bases arranged quincuncially, rather than concentrically.

Stratigraphic and geographic range.— Quasiavonia aculeata is recorded in the Asbian–Brigantian, upper Visean, of Great Britain and Ireland (e.g., Thomas 1914; Gutteridge 1990; Brunton and Tilsley 1991; this study). The species is also recorded in the Visean of Germany ( Winkler-Prins and Amler 2006).

? Quasiavonia sp.

Fig. 8O .

Material.—One articulated specimen: MPUM 11883 ( RCC 3- 11) from mud mound complex of Ricklow Quarry, Monyash, Derbyshire, UK, Monsal Dale Limestone Formation, Brigantian, upper Visean.

Remarks.—The specimen is similar to the specimens assigned to Quasivonia aculeata from the same localities, but it differs in having a quadrate anterior nasute extension of the ventral trail, starting at 10.0 mm from the umbo.

Figures

Fig. 8. Productellidae from the Brigantian (uppermost Visean) of Ricklow Quarry, near Monyash (localities RCC-, RCK-; see Fig. 3) and Wensley Dale, near Matlock (locality WI1; see Fig. 2), Derbyshire, UK. A–E. Alitaria aff. triquetra (Muir-Wood, 1928). A. MPUM11860 (RCC2-13) in anterior view. B. MPUM11861 (RCC12-2) in anterior (B1) and lateral (B2) views. C. MPUM11862 (RCC60-2) in antero-ventral view. D. MPUM11864 (RCC2-40), ventral valve in antero-ventral view.E. MPUM11866 (RCC128-13), dorsal valve in anterior view.F. Eomarginiferina trispina Brunton, 1966, MPUM11869 (WI1- 31) in ventral (F1), dorsal (F2), anterior (F3), and lateral (F4) views. G, H. Overtonia fimbriata (Sowerby, 1824). G. MPUM11870 (RCK15-1b) in ventral G1), dorsal (G2), and lateral (G3) views. H. MPUM11871 (RCK15-53) in ventral (H1) and dorsal (H2) views. I. Avonia sp., MPUM11872 (RCC128-4a), ventral valve in anterior view. J–N. Quasiavonia aculeata (Sowerby, 1814). J. MPUM11873 (RCC32-28a) in anterior view. K. MPUM11874 (RCC49- 28) in anterior (K1), postero-ventral (K2), and lateral (K3) views. L. MPUM11877 (RCC49-24) dorsal valve interior and external cast. M. MPUM11875 RCK17-2) in ventral view. N. MPUM11878 (RCK15-51) dorsal valve interior. O.?Quasiavonia sp., MPUM11883 (RCC3-11); anterior (O1), posterior O2), and lateral (O3) views. P, Q. Krotovia spinulosa (Sowerby, 1814). P. MPUM11884 (RCC54-17b) in ventral view. Q. MPUM11885 (RCC68-2) in ventral (Q1), anterior (Q2), posterior (Q3), and lateral (Q4) views.