Gordenella Gründel, 1990

Gründel, Joachim & Nützel, Alexander, 2013, Evolution and classification of Mesozoic mathildoid gastropods, Acta Palaeontologica Polonica 58 (4), pp. 803-826 : 811-813

Genus Gordenella Gründel, 1990

Fig. 6A, B .

Type species: Cerithium? pommeranum Schmidt, 1905 , original designation; Oxfordian ; Poland .

Included species: Turritella fahrenkohli Rouillier, 1848 , Callovian–Oxfordian; Turritella krantzi Rouillier, 1848 , Oxfordian; Turritella schlumbergi Eudes−Deslongchamps, 1866 , Bajocian; Cerithium? pommeranum

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

Schmidt, 1905, Oxfordian;? Procerithium (Cosmocerithium) kunceviense Gerasimov, 1992 , Tithonian; Gordenella wehrlandia Gründel, 2000 ; Gordenella sp. , cf. wehrlandia Gründel, 2000 sensu Gründel 2003a , Bathonian; Clathrobaculus inconstantiplicatus Guzhov, 2007 , late Callovian?, Oxfordian;? Gordenella ? sp. sensu Schubert et al. 2008, Pliensbachian. According to Guzhov (2007), Turritella sauvagei Buvignier, 1852 , Turritella divisa Ilovaisky, 1904 , Turritella complanata Brösamlen, 1909 , and Promathildia bigoti Cossmann, 1913 are synonyms of Turritella fahrenkohli ; Turritella bicostata Ilovaisky, 1904 and probably also Turritella praecursor Andreae, 1887 are synonyms of Gordenella krantzi .

Emended diagnosis.—Shell slender, large, with many whorls; protoconch heterostrophic, transaxial, distinctly emerged, detached or almost detached from initial teleoconch whorl; early teleoconch whorls with two strong and often several weaker spiral ribs as well as numerous opisthocyrt axial ribs; strong abapical spiral rib moves down towards the abapical suture until it is positioned slightly above the abapical suture; this spiral becomes stronger during ontogeny; at the same time, strong adapical spiral is weakening and may fade entirely; below adapical suture one or two spiral ribs become increasingly stronger; whorl face straight to concave (the latter in most species); axial ribs are reduced to strong growth lines on the last whorls of adult specimens.

Remarks.—The name Clathrobaculus , as cited in older literature, is replaced in the following discussion with Promathildia according to its new definition. Guzhov (2007) described the characteristic type of protoconch for several species representing Gordenella . The same type is also present in Promathildia . When Gründel (2000) introduced the family Gordenellidae , he considered Clathrobaculus as being closely related to Gordenella Gründel, 1990 . However, he decided that the separation line between Mathildidae and Gordenellidae runs between both genera because Clathrobaculus lacks an important character of the Gordenellidae , namely the conspicuous ontogenetic change of the teleoconch sculpture which can even result in a complete reduction of the ornament in mature teleoconch whorls. Clathrobaculus and Gordenella share the relatively large size (for mathildoids), the very slender multiwhorled shell and especially the transaxial protoconch which is widely elevated and not covered by the initial teleoconch whorl. Therefore, Clathrobaculus (= Promathildia ) is assigned to Gordenellidae . All genera of the Gordenellidae have an early ontogenetic “ Clathrobaculus ”−stage, which has also been identified by Guzhov (2007).

Guzhov (2007) assumed a fluent transition from Clathrobaculus sensu stricto in his sense (= Promathildia herein) and species of Gordenella sensu Gründel (2000) . Therefore, he considered Gordenella to represent a synonym of Clathrobaculus . Clathrobaculus medidilatatus Guzhov, 2007 has a relatively weak ontogenetic change of the teleoconch ornament i.e., rounded whorl flanks, minor displacement of the strongest spiral rib in an abapical direction, weakening of the axial ornament associated with an increase in the number of axial ribs per whorl. Even if this species is included in the genus Clathrobaculus , there are still pronounced differences between Clathrobaculus sensu stricto = group 1 according to Guzhov (2007) and groups 2+3 as defined by Guzhov (2007) (= Gordenella sensu Gründel 2000 ): (i) Clathrobaculus has convex and keeled/angulated teleoconch whorls and its teleoconch ornament does not change during ontogeny (or only minor changes occur); (ii) groups 2+3 as defined by Guzhov (= Gordenella sensu Gründel 2000 ) has mostly a concave whorl face (or it is straight) and a pronounced ontogenetic change of the teleoconch ornament which was described in detail by Gründel (2000). The morphological differences between groups 1 and 2+3 sensu Guzhov are much more pronounced than the differences between groups 2 and 3 (subgenera of Gordenella ?). Therefore we consider Gordenella to represent a valid genus, separate from Clathrobaculus (= Promathildia ).

Stratigraphic and geographic range.—Certain Gordenella − species with known protoconch and first teleoconch whorls including an early Promathildia −like stage are known from the Callovian and Oxfordian. Specimens with typical Gordenella −like mature teleoconch whorls were reported from the Bathonian by Gründel (2000) and from the Bajocian by Eudes−Deslongchamps (1866). It is very likely that this material represents Gordenella . The generic assignment of Gordenella ? sp. from the Late Pliensbachian as reported by Schubert et al. (2008) remains doubtful. Procerithium (Cosmocerithium) kunceviciense Gerasimov, 1992 is also insufficiently known. Thus, Gordenella ranges from the Bajocian to the Oxfordian according to the current state of knowledge. The genus is known from Germany, France, Luxembourg, Poland, Russia.

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).