Promathildia cf. milierensis Zardini, 1980

Hausmann, Imelda M., Nützel, Alexander, Roden, Vanessa Julie & Reich, Mike, 2021, Palaeoecology of tropical marine invertebrate assemblages from the Late Triassic of Misurina, Dolomites, Italy, Acta Palaeontologica Polonica 66 (1), pp. 143-192 : 166-167

Promathildia cf. milierensis Zardini, 1980

Fig. 21C–H .

Material.— Twenty specimens, 19 from bulk samples, 1 from surface sample; all from Misurina Landslide ( PZO 12722–12727 , 6 figured specimens; PZO 12721 , 14 specimens); Italy, Carnian , Triassic .

Description.—Shell high-spired, slender; whorl face distinctly angulated low on the whorls; whorl ornamented with two spiral cords and ca. 10 axial ribs per whorl; adapical spiral cord weak to absent, in subsutural position; abapical spiral cord strong, forming angulation and periphery, somewhat above abapical suture but higher on whorl face in earlier whorls; nodes at intersections of spiral cords and axial ribs, strong on abapical spiral cord, weak on adapical cord; whorl face with fine spiral threads; protoconch consisting of somewhat more than one whorl with a diameter of the first whorl 0.24 mm; protoconch smooth except a very fine spiral striation; first teleoconch whorls angulated but without distinct ornament; teleoconch ornament develops from the third teleoconch whorl onward; base flat with spiral ornament and a spiral cord at angulation at border to whorl face.

Remarks.—The main characteristic of this species is the pronounced carina with strong, almost spiny nodules low on the whorls and a much weaker subsutural spiral cord. The protoconch with only about one whorl and a relatively large diameter suggest that this species had non-planktotrophic larval development. The specimens are more or less encrusted or fragmented making an identification difficult. They resemble Promathildia milierensis as illustrated by Zardini (1980: pl. 5: 12, 14, 15, but not 13) and Hausmann and Nützel (2015: fig. 8I) but these specimens have the knobby angulation higher on the whorls. Tofanella cancellata Bandel, 1995 , is similar but has more spiral cords and it lacks strong to almost spine-like nodes on the lower spirals. Promathildia colon ( Münster, 1841) and P. pygmaea ( Münster, 1841) as illustrated by Kittl (1894) and Zardini (1978) are similar but examination of Münster’s type specimens of these species showed that they are probably not conspecific with our specimens.

Promathildia cf. decorata (Klipstein, 1843)

Fig. 21A .

Material.—Two shells (PZO 12729, 12728) from Misurina Landslide bulk samples, Italy, Carnian, Triassic.

Description.— Two juvenile specimens with preserved protoconch show strongly angulated whorls; spiral carina below mid-whorl, additional spiral cord present below suture; additional spiral cords on base; protoconch coaxial heterostrophic with radial fold at the end of larval shell; axial ornament either weak or absent, obscured due to preservation.

Remarks.—These two juvenile specimens resemble the early whorls of Promathildia decorata (Klipstein, 1843) as reported by Bandel (1995) who also reported the same type of coaxial protoconch with folds. In addition, Bandel’s (1995) specimens have axial threads as teleoconch ornament which might be obscured due to preservation in our specimens.

Figures

Fig. 21. Heterobranch gastropods from Misurina Landslide, northern Italy, Cassian Formation, Carnian, Upper Triassic. A. Promathildia cf. decorata Klipstein, 1843), PZO 12729, in lateral (A1) and apical (A3) views; A2, close up to show heterostrophic protoconch, in lateral view. B. Promathildia subnodosa (Münster, 1841), PZO 12730, in apertural view. C. Promathildia cf. milierensis Zardini, 1980; PZO 12722, in apertural view (C1); C2, close up to show heterostrophic protoconch, in lateral view; C3, close up to show heterostrophic protoconch, transition to teleoconch well visible, in lateral view. D. Promathildia cf. milierensis Zardini, 1980, PZO 12725, in lateral view. E. Promathildia cf. milierensis Zardini, 1980, PZO 12723, in lateral view. F. Promathildia cf. milierensis Zardini, 1980, PZO 12726, in lateral view. G. Camponaxis lateplicata (Klipstein, 1843), PZO 12731, in lateral view. H. Promathildia cf. milierensis Zardini, 1980, PZO 12727, in lateral view. I. Promathildia cf. milierensis Zardini, 1980; PZO 12724, in lateral view.