Rhipidomella michelini ( Léveillé, 1835 )

Sun, Yuanlin & Baliński, Andrzej, 2008, Silicified Mississippian brachiopods from Muhua, southern China: Lingulids, craniids, strophomenids, productids, orthotetids, and orthids, Acta Palaeontologica Polonica 53 (3), pp. 485-524 : 519-521

publication ID	https://doi.org/ 10.4202/app.2008.0309
persistent identifier	https://treatment.plazi.org/id/1B17B006-D451-971F-2EC8-02424149FCBF
treatment provided by	Felipe
scientific name	Rhipidomella michelini ( Léveillé, 1835 )
status

Treatment

Rhipidomella michelini ( Léveillé, 1835)

Fig. 26 View Fig .

1835 Terebratula Michelini View in CoL ; Léveillé 1835: 39, pl. 2:14–17.

1968 Rhipidomella michelini (L’Eveillé) 1835 ; Brunton 1968: 17–21, pl. 3: 1–25, text−fig. 5.

cf. 1971 Rhipidomella michelini? (Léveillé) ; Roberts 1971: 41–42; pl. 1: 1–5; pl. 2: 1–5.

2006 Rhipidomella michelini ( Léveillé, 1835) ; Bassett and Bryant 2006: 502–504; pl. 1: 1–4; pl. 6: 11–17.

Material.—140 complete shells and more than three hundred well preserved isolated dorsal and ventral valves representing wide range of growth stages.

Description.—Shell medium sized, gently dorsibiconvex, rounded in outline, slightly wider than long, very weakly unisulcate, with straight and narrow hinge line. Ventral valve with apsacline, concave interarea and wide, open delthyrium with apical angle of about 89 °. Dorsal interarea lower than ventral, concave, notothyrium closed.

Interior of the ventral valve with strong teeth supported by sub−vertical dental plates; small triangular pedicle callist developed apically; slightly elongate suboval diductor scars weakly impressed, bounded laterally with low ridges running from bases of dental plates. Dorsal valve interior with prominent cardinal process; chilidial plates very short, enclosing cardinal process postero−laterally ( Fig. 26H View Fig ); brachiophores widely divergent at about 116 °, supported by more or less vertical plates; adductor scars poorly differentiated but in some specimens a low median ridge extends from near cardinal process to about one−third of the valve length ( Fig. 26F, H View Fig ). Anterior internal surface of both valves bears long radial grooves which are the deepest at the anterior margin ( Figs. 26A View Fig 2, B, C 2, D 2, F 2, H 2 View Fig ; see also discussion in Brunton 1968: 18–19).

Shell ornamentation costellate with 18–22 costellae in 5 mm at 5 mm distance from valve apex, increasing by bifurcation; rib apertures at variable frequency, usually every 0.7–1.3 mm of the rib length.

Remarks.—Morphological characteristic of the species from the Muhua Formation suggests close relationship with Rhipidomella michelini . In comparison with the specimens of the species described from Ireland and Belgium by Brunton (1968) the Chinese specimens differ in having slightly larger apical angle of delthyrium. However, this difference is rather minor and general external aspect of both valves and details of shell ornamentation are the same.

Stratigraphic and geographic range.—This is rather common Mississippian species in Europe, but was also reported from China and Australia. The present material was found in samples D1, MH 1, MH 2, and Mu−42.