Wortheniopsis rakusi, 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 : 9-12

Wortheniopsis rakusi n. sp.

( Figs 4–10 )

Type specimen – GBA 2017/001/0002.

Type locality – Hierlatz Alpe , Hallstatt ( Austria).

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

Derivation of name – Dedicated to Milos Rakús, late Slovakian colleague.

Material – Single specimen that consists of four fragmentary whorls; protoconch and the earliest teleoconch whorls are lacking, just like the latest, near peristome parts of the last whorl.

Dimensions – Width: 11.5 mm; spiral angle: 45°.

Diagnosis – High turbiniform, thin walled shell; slightly convex whorls, shallow impressed suture, last whorl somewhat inflated. Early whorls rounded-angular at both sides of suture, last whorl turning into base along wide, even arch. Last whorl with obscure angulation and slightly concave ramp below adapical suture. Base as whole subconoidal, its wall convex;?narrowly phaneromphalous. Selenizone rather narrow, concave and bordered by two threads above midwhorl on latest whorls. Ornament of spiral threads above selenizone, crossed by collabral threads with granules at intersecting points. Sparse, asymmetrical, weak spiral ridges below selenizone and on base. Growth lines fine, prosocyrt and just gently prosocline above and below selenizone on whorls, feebly opisthocline on base with shallow opisthocyrt part abaxially. Selenizone with sparse lunulae on early whorls, with growth lines only on last whorl.

Description – A high turbiniform, very thin walled shell represents the species. It is composed of slightly convex whorls, which are separated by a slightly impressed, almost flush suture. The earliest preserved whorls are rounded-angular at both sides of the suture but the last whorl turns into the base without angulation along a wide, even arch. The spire whorls are slightly convex and there is no angulation on their surface but the belt between the selenizone and the adapical suture becomes feebly concave on the last whorl; actually a concave ramp develops. Along the abapical boundary of the ramp, which coincides with the abapical rim of the selenizone, an angulation with the outer face is just observable. The selenizone itself seems flat on the early whorls but concave on the last one; its width is rather narrow, about 12% of the sutures distance on the penultimate whorl. The outer face itself is wider than the ramp and has flat surface that bends into the base along a wide, unbroken arch. The base is convex, subconoidal as a whole and it has convex wall that evenly turns into an axial deepening. Its matrix infilling seems to hide a narrow umbilicus. The selenizone is narrow, concave and two threads border it well above the midwhorl on all preserved whorls.

Several equally spaced spiral threads ornament the whole surface adapically from the selenizone that are crossed by collabral threads and granules are at their intersecting points. Towards the last whorl, the number of the growth lines increases. Sparse, asymmetrical, weak spiral ridges, belonging to the type which has been first observed in Wortheniopsis quirinii (Stoppani, 1858) , see in KITTL (1899, p. 14, Fig. 2 .), ornament the whorls below the selenizone and on the base. Lunulae are present on the selenizone of the early whorls but they are missing on the last whorl. The growth lines are very fine and have a peculiar arrangement; they are prosocyrt and just gently prosocline above and below the selenizone on the whorls and feebly opisthocline on the base with a shallow opisthocyrt part on the abaxial half of the base.

Remarks – The only specimen of Wortheniopsis rakusi n. sp. is exceptionally well preserved compared to the syntypes of the Middle Triassic type species. In spite of the considerable age difference, their comparison shows only slight differences in the shell shape and the details of the ornament. W. rakusi n. sp. has about 10° wider spiral angle, less impressed suture, less convex whorls, so more conoidal outline, and a network ornament with granules at the crossings between the selenizone and the adapical suture.

W. rakusi n. sp. clearly shows that the growth lines and the collabral ornamental elements terminate at the threads, delimiting the anal fasciole, which indicate a true selenizone, not a sinuszone. Lunulae on the penultimate whorl and lunuliform growth lines on the last whorl endorse this assumption. Both species have quirinii type ridges between the selenizone and the axial region of the base.

For distinction from Wortheniopsis bakonyensis n. sp. see the next description.

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

Figures

Figs 4–14.Wortheniopsisspecies fromtheHierlatz LimestoneFormation.– 4–10.Wortheniopsisrakusi n.sp.from the Sinemurian to lowermost Pliensbachian interval (Lower Jurassic) of the Hierlatz Limestone in the Hierlatz Alpe,Hallstatt, Austria,GBA 2017/001/0002,all ×4.– 4. Dorsal view.– 5. Peristomal view.– 6. Basal view. – 7–9. Same views as 4–6 but in natural (×1) size. – 10. Details of the ornament on thespire whorls,×7.– 11–14.Wortheniopsis bakonyensis n. sp.,?Lower Sinemurian (Lower Jurassic) Hierlatz Limestone variety with rich micrite content, Csárdahegy, Úrkút, Bakony Mts, Hungary, GGIH J.08.3.1. – 11. Peristomal view of the holotype, ×4. – 12. Lateral view to show the best preserved outline part, ×4.– 13–14. The same views as in figures 11–12 but in natural (×1) size

Figs 1–3. The peculiar “quirinii type” ridges, occurring in Wortheniopsis Böhm, 1895, Foveolaria n. gen. and some probably related forms. – 1. Copy of KITTL’s (1899, p. 14, Fig. 2) sketch. – 2. The ridges on the outer face and on the base of Wortheniopsis rakusi n. sp. – 3. The ridges on the base of Foveolaria conoidea n. sp.