Werfenella, Nützel, 2005

Nützel, Alexander, 2005, A new Early Triassic gastropod genus and the recovery of gastropods from the Permian / Triassic extinction, Acta Palaeontologica Polonica 50 (1), pp. 19-24 : 20

Genus Werfenella nov.

Type species: Turbo rectecostatus Hauer, 1851

Derivation of the name: After the Early Triassic Werfen Formation.

Diagnosis.—Turbiniform, relatively low−spired purpurinid gastropods with angular, step−like whorl profile, gently sloping subsutural ramp; ornament of axial ribs and nodes where ribs and angulations intersect; aperture wide, oblique subrectangular to oval.

Discussion.— Werfenella is a characteristic gastropod genus with an angulated whorl profile and a rather strong ornament of axial ribs and nodes where ribs and angulations intersect. Its type species Turbo rectecostatus was placed in the modern genus Turbo Linnaeus, 1758 by Hauer (1851) and the systematic position of this species has not been changed subsequently. However, according to Hickman and McLean (1990) and Knight et al. (1960), the genus Turbo appears first in the Late Cretaceous while Sepkoski (2002) noted an Early Tertiary origin. The modern type species of the genus Turbo , Turbo petholatus Montfort, 1810 , is almost smooth to strongly ornamented but has no prominent angulations. The modern subgenus Turbo (Callopoma) has an angulation but is lacks the numerous pronounced axial ribs that are typical of Werfenella .

The Jurassic genus Purpurina d'Orbigny, 1850 and the Triassic purpurinid genus Angularia Koken, 1892 resemble Werfenella but are generally more high−spired and have only one angulation. In contrast to Werfenella , Purpurina has a cancellate ornament and Angularia lacks a nodular ornament. However, a close phylogenetic relationship between Werfenella and these purpurinids seems to be likely as is suggested by the shell shape and by the elongate aperture with an anterior outlet in Werfenella .

Even the vetigastropod genus Chartronella Cossmann, 1902 resembles Werfenella in shape and in the angular whorl profile but Chartronella lacks a prominent axial ornament and is generally more low−spired. Moreover, the aperture of Chartronella is almost circular ( Fig. 1I 2 ) while that of Werfenella is more elongate. The overall similarity of the type species of Chartronella ( Ch. diagonata Cossmann, 1902 from Hettangian, France, reproduced herein after Gründel’s 1997; Fig. 1I ) suggests a possible phylogenetic relationship to Werfenella while the aperture does not suggest such a relationship. Chartronella was placed in the Family Paraturbinidae , which ranges form the Triassic to the Cretaceous ( Knight et al. 1960). Two Chartronella species described by Batten and Stokes (1986) from the Olenekian Sinbad limestone (Moenkopi Formation, Utah) resemble Werfenella rectecostata in some respects: Chartronella? pagina ( Fig. 1G ) and Chartronella unicostata ( Fig. 1H ). Chartronella? pagina Batten and Stokes, 1986 resembles Werfenella in shell shape and in having carinations. Like Werfenella , Chartronella? pagina has axial ribs. However, the ribs are weaker, almost thread−like, and intersections with carinae are not nodular. Chartronella? pagina is known from a single specimen and was only tentatively assigned to Chartronella by Batten and Stokes (1986). The genus Guidonia Stefani, 1880 is similar to Werfenella but this genus lacks a prominent axial ornament.

In conclusion, Werfenella resembles genera of the caenogastropod family Purpurinidae and the archaeogastropod family Paraturbinidae . Therefore, the subclass assignment of Werfenella is not beyond doubt and can only be resolved with certainty if the protoconch of Werfenella is reported. However, given the relatively bad preservation of gastropods in the Werfen Formation, I do not expect that this protoconch will be reported in the near future. The shell shape and the aperture make it more likely that Werfenella is a purpurinid caenogastropod.

Figures

Fig. 1. A–F. Werfenella rectecostata from the Early Triassic (Olenekian) Werfen Formation. A. Reproduction of Frech's (1912: pl. 7: 7a–c) illustrations of exceptionally well−preserved specimens of Werfenella rectecostata from the Tirolites−Marls near Csopak (Iszkahegy, Hungary). B. Reproduction of Hauer's (1851: pl. 20: 10) original illustrations of “Turbo” rectecostatus. C–F. Werfenella rectecostata in typical preservation as more or less deformed steinkerns. Despite poor preservation species identity is strongly suggested by the characteristic shape and traces of the axial ornament. C. NHMW 1865 IX 22, Heilig Kreuz near St. Cassian, Südtirol. D. NHMW 1858 IX 3A, Heilig Kreuz near St. Cassian, Südtirol. E. NHMW 1884 D 475, Pitzberg, Südtirol. F. BMNH G 9059314A, Fachiade Monzoni. G. Chartronella? pagina Batten and Stokes, 1986, from Batten and Stokes (1986: fig. 10); this species from the Olenekian of Utah resembles Werfenella rectecostata. H. Chartronella unicostata Batten and Stokes, 1986, from Batten and Stokes (1986: fig. 8). I. Chartronella diagonata Cossmann, 1902, topotype material of the type species of Chartronella from the lowermost Jurassic (Hettangian) of France (from Gründel 1997: pl. 2: 1, 2).

Fig. 2. Limestone slab with several specimens of Werfenella rectecostata; Werfen Formation, Cencenighe Member, Bad Radein/Redgano, Italian Dolomites, Weisshorn (MHI 1819). The specimens show unusually wellpreserved shells with a pronounced nodular ornament at the carinations which cannot be seen in the steinkern−preservation which is usual for gastropods from the Werfen Formation.