Cupaniella praebiplicata, Szabó, 2018

Cupaniella praebiplicata n. sp.

( Figs 15–19 View Figs 1–19 )

Type specimens – Holotype: (GBA 2019/009/0005); paratypes: (GBA 2019/ 009/0006–9).

Type locality – Hierlatz Alpe (Hallstatt, Austria).

Type strata – Lower Jurassic Hierlatz Limestone from the Semicostatum Zone (Lower Sinemurian) to Jamesoni Zone (Lower Pliensbachian) interval.

Derivation of name – Referring to probable ancestral relation to the Late Pliensbachian Cupaniella biplicata M. Gemmellaro, 1911 .

Diagnosis – Rather highly turriculate shell with acute early part. Subcylindrical shell part consisting of about last and penultimate whorls. Base subconoidal with feebly convex wall. Peristome clearly extending left from coiling axis. Columellar lip sharp and having two tooth-like processes on adapertural-adapical part. Parietal lip built as thin, smooth shell enamel. Near outer lip shell part outward reflecting and forming wide arch. From penultimate whorl shallow, subsutural depression appearing then becoming deeper and narrower and forming false fold internally. Network ornament of spiral threads and cords, crossed by collabral threads on whorls and base.

Material – Six fragmentary specimens (GBA 2019/009/0005–10) mostly embedded in strongly recrystallised, hard matrix. They represent almost all ontogenetic stages so the shell form can be quite well reconstructed.

Measurements – Holotype (GBA 2019/009/0005), W = 4.5 mm, paratype (GBA 2019/009/0006), H = 7.2 mm, paratype (GBA 2019/009/0007), H = 4.8 mm, paratype (GBA 2019/009/0008), W = 4.7 mm, paratype (GBA 2019/ 009/0009), H = 7.3 mm.

Description – The reconstructed shell is rather highly turriculate and pupiform. Its early parts, consisting of about seven whorls, are acute but the penultimate and latest whorls change into sub-cylindrically coiled with a base that is subconoidal. The early whorls are convex and bear a sharp spiral angulation just above the impressed suture. For the latest two whorls, the suture becomes similar to an incision and the angulation above it apparently vanishes. Almost simultaneously, a narrow and shallow spiral concavity appears in subsutural position that rapidly deepens and its edges gradually approach each other. For the last whorl, the two rims are closed, and the former furrow looks like the suture. This concavity forms a false spiral fold within the shell that is reflected on the inner mould as a furrow. The last half whorl tends downward and to adaxial direction in such degree that the peristome and the aperture get partly left from the coiling axis. The columellar lip has a sharp edge with two tooth-like processes on its adapertural-adapical part. The parietal lip is built as a thin, smooth shell enamel. The outer lip forms a wide arch between the suture and the foot of the columella and it is outward reflected.

The teleoconch has network ornament of spiral threads and cords, crossed by thin collabral threads equally on the whorls and the base. Granules or short spines are sitting at the intersections.

Remarks – Cupaniella biplicata M. Gemmellaro, 1911 differs from Cupaniella praebiplicata n. sp. in the lack of the marked inner fold – outer furrow complex. The shell outline is also different: the last three whorls have cyrtoconoidal, almost cylindrical outline in C. biplicata but more slender in C. praebiplicata n. sp. with feebly coeloconoidal earliest parts. The earliest shell parts are cyrtoconoidal in C. biplicata .

In more precisely dated localities, C. biplicata occurred in Late Pliensbachian strata while the Hierlatz Alpe specimens are most probably Sinemurian, or Early Pliensbachian; they seem to belong to the same evolutionary lineage.

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