Foveolaria conoidea, Szabó, 2016

Szabó, János, 2016, Gastropods of the Lower Jurassic Hierlatz Limestone Formation, part 2. Some new archaic type slit-bearing components from the fauna of the Hierlatz Alpe (Hallstatt, Austria) and the Bakony Mts (Hungary), Fragmenta Palaeontologica Hungarica 33, pp. 3-30 : 17-20

Foveolaria conoidea n. sp.

( Figs 19–22 )

Type specimen – GBA 2017/001/0004.

Type locality – Hierlatz Alpe , Hallstatt ( Austria).

Type strata – Sinemurian to lowermost Pliensbachian (Lower Jurassic) Hierlatz Limestone .

Derivation of name – Referring to the conoidal shell outline.

Diagnosis – Conoidal shell outline with slightly convex whorls with obscure angulation feebly below midwhorl. Ramp flattish with narrow convex belt subsuturally and concavity along selenizone. Selenizone concave and angled to ramp and outer face so blunting angulation of whorl. Outer face concave, limited by markedly swollen abapical belt, providing periphery of shell and rim of base. Base low conoidal as whole and having slightly convex wall; anomphalous or minutely phaneromphalous. Spiral threads and collabral riblets on whorls except in selenizone, spiral ones vanishing from later whorl. Base covered with almost evenly spaced quirinii type ridges.

Material – Single specimen, composed of remains of three latest whorls.

Dimensions – Width: 9.4 mm.

Description – The only shell has conoidal, just slightly gradate outline with an obscure angulation feebly below the midwhorl. The rather steep ramp is flattish with a narrow convex belt subsuturally and some concavity along the selenizone. The selenizone itself is concave and angled both to the ramp and the outer face obscuring the angulation of the whorls. The outer face is concave; a markedly swollen belt limits it abapically, providing also the periphery of the shell and outer rim of the base that joins with angulation to the whorl surface. The slightly impressed suture does not follow the periphery but a line slightly adaxially from it on the base. As a whole, the base is low conoidal with slightly convex wall; the shell is anomphalous or minutely phaneromphalous.

Spiral threads and collabral ribs/riblets ornament the whorls apart from the selenizone; granules at the intersections are frequently preserved. The spiral threads are sparse and much weaker than the ribs on the ramp and gradually vanish for the last growth phase. The ribs of this area start from the suture and almost vanish before reaching the selenizone; their subregularly repeated interspaces gradually increase on the last half whorl. On the outer face, spiral and collabral threads form a dense network; first the collabral ones change into short riblets, crossing the spiral threads, then they fully disappear for the last whorl. The spiral threads also vanish from the adapical belt of the outer face but remain in the swollen peripheral belt. On the selenizone of the preserved shell parts, no lunulae are found. The base is covered with almost evenly spaced moderately dense quirinii type ridges. The growth lines are rather strongly prosocline and prosocyrt on the ramp, prosocyrt-orthocline on the outer face and slightly prosocline-opisthocyrt on the base.

Remarks – The vanishing ornament of the latest whorl resembles the last whorl of Foveolata bicarinata n. sp. The steeper ramp, the less impressed suture, consequently less gradate outline, and the selenizone, blunting the angulation of the whorl surface distinguish Foveolaria conoidea n. sp. from F. bicarinata . Besides, the latter species has a rather broad umbilicus but F. conoidea seems anomphalous or very narrowly phaneromphalous.

The subglobular shell, the more convex surfaces (ramp, outer face and base wall) and the presence of a quite wide umbilicus in Foveolaria globosa n. sp. distinguish it from F. conoidea .

Foveolaria suemegensis n. sp. has similarly steep ramp like F. conoidea but their ornaments at identical size are strongly different; marked in F. conoidea but scarce in F. suemegensis . Their selenizones are also in different position.

Distribution – Within the Sinemurian to lowermost Pliensbachian interval (Lower Jurassic) of the Hierlatz Limestone Formation in Hierlatz Alpe, Hallstatt, Austria.

Figures

Figs 15–29. New species of Foveolaria n. gen. from the Sinemurian to lowermost Pliensbachian interval (Lower Jurassic) of the Hierlatz Limestone in the Hierlatz Alpe, Hallstatt, Austria. – 15–18. Holotype of Foveolaria bicarinata n. sp., GBA 2017/001/0003, all ×3.8. – 15. Dorsal view. – 16. Apical view. – 17. Basal view. – 18. Peristomal view. – 19–22. Holotype of Foveolaria conoidea n. sp., GBA 2017/001/0004, all ×4. – 19. Dorsal view. – 20. Apical view. – 21. Basal view. – 22. Peristomal view.– 23–26. Holotype of Foveolaria globosa n. sp., GBA 2017/001/0005, all ×4. – 23. Dorsal view. – 24. Apical view. – 25. Basal view. – 26. Peristomal view. – 27–29. Foveolaria sp., GBA 2017/001/0006, all ×4. – 27. Apertural view. – 28. Basal view. – 29. Dorsal view