Coelostylina Kittl, 1894

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 : 82-83

Genus? Coelostylina Kittl, 1894

Type species – Melania conica Münster, 1841

Coelostylina ? sp1.

( Figs 68–69)

Material – Single specimen (GBA 2019/009/0044) from a box, labelled as Chemnitzia sp.

Measurements – D = ~ 16 mm, spiral angle: ~35°.

Description – The remnants represent a thin shelled species, having moderately turriculate spire with about 35° coiling angle in the latest growth phase. Three whorls are visible, which show a slightly ovate outline, so the apical angle must be considerably wider. The whorls are convex and an impressed suture separates them. A strongly rounded angulation is observable slightly above the suture on the earlier whorls, that is absent from the last whorl. The periphery nearly coincides with the midwhorl on the last whorl but it is nearer to the lower suture on the former whorls.

A little, eroded portion of the shell shows rather sparse, orthocline, and feebly opisthocyrt grooves on its surface and much wider, smooth, and flat bars in the interspaces under magnification. Regular corrugation of the margins of the bars may indicate dense, delicate spiral lineation in less damaged stage.

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

Coelostylina ? sp2.

( Figs 70–71)

Material – Two fragmentary specimens (GBA 2019/009/0045–46) from boxes, labelled as Chemnitzia sp.

Measurements – The figured one (GBA 2019/009/0045), D = 16.6 mm, spiral angle: ~20°.

Description – Last three whorls represent the figured specimen. They are remnants of a rather highly turriculate shell, consisting of moderately convex whorls with a narrow and shallow concavity along the adapical suture; top of the convexity lies nearer to the abapical suture. The suture itself is in a slightly impressed position and appears as a groove. In the latest growth phase, the convexity of the whorl surface enfeebles into almost flat. Concomitantly, the periphery shifts from the line of maximum convexity to the line in prolongation of the suture where a weak angulation also develops. The base is subconoidal with convex wall; no trace of an umbilicus is found. No intact part of the peristome is preserved; the shell cross-section in this area indicates an axially elongated aperture/peristome without siphonal outlet.

The last two whorls bear an ornament of obscure spiral threads; they are denser in a belt at the midwhorl and sparser abapically from the formerly mentioned ones. On the last whorl, a strong thread follows the angulation. Pieces of sharp cords are also visible in the periaxial area on the base. Growth lines are observable only on the last whorl; they are slightly prosocline and opisthocyrt between the suture and the periphery, and seem to be slightly prosocyrt and nearly orthocline on the base.

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