Riselloidea noszkyi Szabó, 1995

Szabó, János, 2018, Gastropods of the Lower Jurassic Hierlatz Limestone Formation, part 4. New eucycloidean, trochoidean, neritimorph, and caenogastropod taxa in the fauna of the Hierlatz Alpe (Hallstatt, Austria), Fragmenta Palaeontologica Hungarica 35, pp. 61-84 : 65

Riselloidea noszkyi Szabó, 1995

( Figs 10–14)

1995 Riselloidea noszkyi sp. n. – SZABÓ, p. 71, pl. 7, figs 1–3.

2009 Riselloidea noszkyi Szabó – SZABÓ, p. 83, Fig. 78.

Material – Two fragmentary shells (GBA 2019/009/0002–3).

Measurements – (GBA 2019/009/0002), D = 10.5 mm, whorl fragment (GBA 2019/009/0003), H = 7.2 mm.

Description – The available specimens have turbiniform-subgradate shell with convex whorls and flat, anomphalous base of feebly convex wall; the transition of the last whorl to the base is rounded angular. Surface of the whorls is composed of a few feebly concave belts between pairs of carinae or the peripheral carina and the suture, respectively. The number of these belts and carinae somewhat increases during the growth; the new carinae are added along the adapical suture. For the last whorl, five carinae develop; the lowermost one is overlapped by the suture on the spire whorls. The most prominent carina, providing also the periphery, runs adapically next to the suture. So the suture itself has an impressed position. Several sparsely but regularly distributed spiral cords are also on the base, they are similar in strength to the carinae of the whorl surface.

On the whorl surface, the carinae are sparsely spiny, riblets start from these spines collabrally towards the neighbouring carinae. The spines become strong, adaperturally open processes on the strongest carinae and follow each other scaly way. On the early whorls, the riblets frequently vanish within the interspace of the carinae but on the latest two whorls, they form a network ornament. Very thin, subregularly repeated growth threads occur between the riblets. Spines are lacking from the spiral cords of the base and they are gradually thinner and dens- er in adaxial direction. Dense, feebly opisthocyrt growth lines or growth threads between the peripheral and the axial parts cross them. On the whorl surface, the growth lines are prosocline, slightly on the early whorls but strongly on the last whorl with gradual change.

Remarks – This species has been established on poorly preserved specimens from the Bakony Mts (Sümeg, Hungary). Now some new characters can be added to the morphology from the Hierlatz finds; they have helped to recognise the scaly nature of the nodules on the peripheral and its adapically neighbouring keels. These nodules suggest crenulate undamaged form of the otherwise not preserved outer lip. The two Hierlatz Alpe specimens indicate that the density of the scaly nodules and the connected collabral threads are probably very much variable.

Occurrence – Within Sinemurian to lowermost Pliensbachian (Lower Jurassic) part of the Hierlatz Limestone Formation in Hierlatz Alpe, Hallstatt, Austria and Sümeg (Bakony Mts, Hungary) Upper? Sinemurian Hierlatz Limestone.