Turritelloidea Walther, 1951

Gründel, Joachim & Nützel, Alexander, 2013, Evolution and classification of Mesozoic mathildoid gastropods, Acta Palaeontologica Polonica 58 (4), pp. 803-826 : 813-814

Genus Turritelloidea Walther, 1951

(= Turrithilda Schröder, 1995 ; =? Costacolpus Marwick, 1966 )

Fig. 6C .

Type species: Turritella opalina Quenstedt, 1852 , original designation; Toarcian to Aalenian; South Germany .

Included species: Turritella minuta Koch and Dunker, 1837 , Kimmeridgian–Tithonian; Turritella opalina Quenstedt, 1852 , late Toarcian– early Aalenian; Cerithium? decipiens Hébert and Eudes−Deslongchamps, 1860 , Callovian;? Turritella anomala Moore, 1867 , Pliensbachian;? Turritella (Mathilda) abbas Hudleston, 1892 , Toarcian– Aalenian; Turritella (Mathilda) strangulata Hudleston, 1892 , Aalenian;? Turritella solitaria Wilckens, 1922 , Late Cretaceous;? Promathildia turritella ( Dunker, 1847) sensu Meier and Meiers 1988 , Hettangian; gen. nov. terquemi ( Bistram, 1903)? sensu Gründel 2003b, Hettangian;? Turritelloidea sp. sensu Schubert et al. 2008, Pliensbachian.

Diagnosis.—Shell median−sized to large and highly conical. The heterostrophic protoconch of the Mathilda − type is nearly coaxial. On the first teleoconch whorl two strong keel−like spiral ribs and numerous axial ribs are developed. The last whorls have 6–7 spiral ribs of almost the same strength. In this part of the shell, the ribs are very broad (broader than the spiral furrows between them). The axial ribs become also broader and at the same time weaker. The ornament of the last whorls of adults consists only of broad spiral ribs (the base included).

Remarks.—The protoconch is only known for the type species. Hudleston (1892: 230) made the following remark for T.? abbas : “Indications of a sinistral apex have been observed on one specimen ”. However, T.? abbas lacks the broadened, band−like spiral ribs and therefore is placed in Turritelloidea only tentatively (see also Gründel et al. 2011). The protoconch and the early teleoconch whorls of most of the species listed above are unknown and therefore, the generic assignment of these species is not beyond doubt. These species are placed in Turritelloidea because their mature teleoconch resembles that of the type species. The protoconch is also unknown for the type species of the genus Costacolpus Marwick, 1966 ( Turritella solitaria Wilckens, 1922 , Late Cretaceous). Its early teleoconch whorls have an ornament of axial and spiral ribs whereas the mature whorls have exclusively spiral ribs. The spiral ribs become very broad and are separated from each other by narrow furrows. The base has sometimes varix−like thickenings. Costacolpus solitaria closely resembles Turritelloidea opalina in general shape and ornament. Thus, it seems to be likely that Costacolpus represents a junior synonym of Turritelloidea .

In Fig. 6D a yet undescribed genus close to Turritelloidea is illustrated. It is from the Late Pliensbachian of Germany and will be described in the near future in the frame of a larger monograph. Because this genus is important for this work, we give a preliminary description herein. The shell is high−spired with numerous whorls. The early teleoconch whorls are ornamented with few, widely spaced, strong axial ribs. The earliest preserved teleoconch whorls show two median spiral ribs which somewhat angulate the whorl profile. In addition a weaker subsutural spiral is present. The intersections of axial and spiral ribs are nodular in early whorls. The position of the primary spiral ribs remains approximately stable during ontogeny. The spiral and axial ribs become weaker during ontogeny and intersections are not nodular any longer. Numerous additional spiral striae are added on mature teleoconch whorls and axial ornament consists of numerous densely spaced strengthened growth lines. The base is flat and is ornamented with narrow spiral ribs and broader furrows. The protoconch is unknown.

This yet undescribed new genus resembles Turritelloidea . However, Turritelloidea has broad spiral ribs separated by narrow furrows on mature teleoconch whorls. The type species of Gordenella ( Fig. 6A, B ) has a straight whorl profile; its mature teleoconch whorls does not show numerous spiral striae. The relatively large size, the high number of whorls and the suppression of axial ribs during ontogeny suggest that the new genus belongs to Gordenellidae .

Stratigraphic and geographic range.— Turritelloidea is certainly as old as Late Toarcian. It is likely that the genus ranges from the Hettangian to the Bajocian and even to the Late Jurassic or to the Late Cretaceous (e.g., T. minuta from the latest Jurassic and Costatrochus solitaria from the Late Cretaceous).

http://dx.doi.org/10.4202/app.2012.0052

The genus is known from Germany, England, France,? Luxembourg.

Figures

Fig. 6. Type species and examples for Jurassic genera of the family Gordenellidae. A, B. Gordenella pommerana (Schmidt, 1905), Kłęby (formerly Klemmen), Poland, late Oxfordian. A. From Gründel (2000: pl. 1: 8). B. From Gründel (2000: pl. 1: 11). C. Turritelloidea opalina (Quenstedt, 1852), Mistelgau, Germany, late Toarcian, see also Gründel (2005: figs. 2/1, 3). D. New genus, new species to be described elsewhere, Buttenheim, Germany, late Pliensbachian; whole specimen (D1), early whorls (D2).