Johnsoniana oceani
Creators: name: Poletaev, Vladyslav
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Brachiopoda
Rhynchonellata
Spiriferida
Spiriferidae
Johnsoniana
Johnsoniana oceani

description: Johnsoniana oceani (d’Orbigny, 1850)
Fig. 6B–E
Spirifer oceani d’Orbigny, 1850: 149, pl. 38 fig. 29.
Spirifer cheiropteryx – de Koninck 1843: 245, pl. 15 fig. 9. — Quenstedt 1871: 510, pl 53 figs 71–73.
Spirifer oceani – de Koninck 1887: 132, pl. 28 figs 11–16.
Verneuilia oceani – Hall & Clarke 1893: 1–317. — Ivanova 1960, pl. 58 figs 14–15. — Nalivkin 1979: 143, pl. 62 figs 19–24. — Brunton 1984: 101, text-fig. 160. — Gourvennec 1994: 578, pl. 1 figs 7–31. — Mottequin & Poty 2022: text-fig. 11j.
Oceania oceani – Poletaev 2015: 17–18; 2018: 95, pl. 117 figs 1–7.
Diagnosis
As for genus.
Material examined
Neotype (Fig 6B) GREAT BRITAIN • Viséan, upper Warnantian (late Asbian); specimen from Davidson Coll., selected by Brunton (1984: 101, fig. 160); NHM B7923.
Paratypes FRANCE • 2 specs; Viséan; Office National des Collections Paléontologiques (ONCP), University C. Bernard, Lyon; ONCP D306a, ONCP D306e (Fig. 6D–E).
RUSSIA • 17 specs; Southern Urals (Bashkortostan), Ussuily River; upper Tournaisian, Kizelovskian Horizon; Nalivkin 1979 Coll.; CNIGR Museum 3085 (Fig. 6C).
Description
The shell is small with trapezoidal outline; the cardinal extremities are angular but not mucronate. The maximum width coincides with the hinge line. The convexity of the shell is regular but the ventral valve is slightly more convex than the dorsal. The ventral interarea is high, triangular, regularly curved, usually apsacline to catacline; beak is small and curved. The delthyrium is narrow and much higher than the width, the upper half is covered by a convex pseudodeltidium. The surface of the interarea bears strong vertical crenulations that are never branching. These crenulations produce a fine denticulation on the hinge, corresponding to equivalent cupules on the dorsal valve.
The dorsal interarea is very narrow, anacline. The angle between ventral and dorsal interareas is 90°– 120°. The ventral sulcus is shallow, widely rounded, tends to become deeper and wider towards the anterior margin. The dorsal sulcus corresponds to the ventral one. The sulci are bordered by low angular plications, that never become carina. The sulci widen regularly during the early stages of growth but bounding plications tend to become parallel or almost convergent. The anterior edge of the plications does not significantly protrude beyond the general anterior outline. The commissure is usually bent towards the ventral valve before abruptly turning towards the dorsal one near the sulci. In this case a more or less developed tongue is present. The flanks are smooth. The microornament consists of faint, regularly spaced growth lines coarser than in Verneuilia cheiropteryx. In the ventral valve are very long divergent dental flanges, bordering the inner side of the delthyrium (Gourvennec 1994: 580, fig. 2). The teeth are small. In the apical part of the ventral valve sometimes is a short, low, flat median ridge. In the dorsal valve, the very faint striated ctenophoridium is located on an elevated cardinal platform anteriorly and extended by a narrower median shelf at about ¼ of the length of the shell. The ctenophoridium is bounded by weakly developed very short and narrow sockets. Under the sockets are located the narrow, slightly oblique crural bases, supported by small “columnal” thickenings of the shell united the cardinal platform with crural bases and joining them at the floor of the valve. These very poorly developed thickenings do not properly constitute the crural plates or only rudimentary ones. The direction of the spires is approximately parallel to the plications (after Gourvennec 1994: 578).
Remarks
The external appearance of Johnsoniana oceani is similar to that of Verneuilia cheiropteryx (Fig. 6A), but the former can be distinguished by its smaller, less transverse shell outline, lack of mucronation of the cardinal extremities, denticulate hinge line, much narrower sulcus bordered by low angled but never carinate plications. The plications bordering the sulci of J. oceani tend to become parallel during adult growth, whereas they are regularly divergent in V. cheiropteryx. Johnsoniana oceani is distinguished from V. cheiropteryx by the absence of short dental plates in the ventral valve. Johnsoniana oceani is distinguished from Changshunella yangi by the much larger size, lack of prominent median plications in sulcus and opposite rib on dorsal valve, lack of sticks on anterior ends of ribs, bordered sulci. The type species of Verneuilia and Johnsoniana also differ in the micro-ornamentation of the shell surface: the presence of fine randomly arranged pits on V. cheiropteryx and obscure radial striae on J. oceani.
Dіstribution
Calcaire de Visé (Visean) in Belgium; late Tournaisian of the South Urals (Bashkortostan), Russia.
description: Published as part of Poletaev, Vladyslav, 2024, New and revised taxa of Carboniferous spiriferides (Brachiopoda, Spiriferida) from the Donets Basin (Ukraine) and South Urals (Russia), pp. 132-155 in European Journal of Taxonomy 968 on pages 146-148, DOI: 10.5852/ejt.2024.968.2723, http://zenodo.org/record/14047314