Chilodonta, Kaim, Andrzej, Jenkins, Robert G., Tanabe, Kazushige & Kiel, Steffen, 2014

Kaim, Andrzej, Jenkins, Robert G., Tanabe, Kazushige & Kiel, Steffen, 2014, Mollusks from late Mesozoic seep deposits, chiefly in California, Zootaxa 3861 (5), pp. 401-440 : 410

Chilodonta ? reticulata sp. nov.

( Fig. 3 B–D)

Diagnosis. Shell thick, low-turbiniform with strong orthocline axial ribs, weaker spiral ribs and knobs at the intersections. Shell flank convex. Peristome almost circular with wide callus around the peristome; no denticles or plaits.

Holotype: GZG.INV.84971, the only specimen available, H = 7.6 mm, W = 6.3 mm.

Type locality and strata: Bear Creek, Colusa County, California, USA; locality # 4 in Kiel et al. (2008b). Great Valley Group, Grizzly Canyon member of Crack Canyon Formation; Valanginian (Early Cretaceous).

Description. Protoconch unknown. Shell turbiniform with three whorls preserved. Number of spiral ribs increasing during ontogeny from four to eight. Approximately 15 axial ribs per whorl. Base ornamented by six spiral ribs. Shell evenly convex with no angulation. Shell wall thick. Generating curve circular, aperture tangential, and peristome uninterrupted. Outer, inner and parietal lips wide and smooth; no umbilicus.

Remarks. Chilodonta ? reticulata is most similar to Chilodonta cureti ( Cossmann, 1900) from the Early Cretaceous of southern France ( Cossmann 1900, 1918). That latter species was originally described as Amberleya by Cossmann (1900) and later moved to Eucyclus ( Cossmann 1915b, 1918). Recently Gründel & Kollmann (2013) assigned the species to Chilodonta arguing that clathrate sculpture and spirals on the base are more characteristic to chilodontids, though the latter character is present even in the type species of Eucyclus (e.g., Ferrari et al. in press). On the other hand, neither Chilodonta ? cureti nor Cantrainea ? reticulata possess denticles or plaits on the peristome, features that are characteristic for chilodontids. The aperture of C.? reticulata resembles those of other colloniins from Cretaceous chemoautotrophy based communities ( Kaim et al. 2008b, 2009 and herein) e.g., Cantrainea and Hikidea . The Recent species of Cantrainea ( Warén & Bouchet 1993; Sasaki et al. 2005), however, have low spiral ridges but no axials. Chilodonta ? reticulata may actually represent a new, yet undescribed genus of seep-related colloniins or chilodontids. We refrain from introducing a new generic name for it due to the scarcity and imperfection of the available material. A somewhat similar shell has been described by Ascher (1906) as Littorina dictyophora Ascher, 1906 from the locality Koniakauer Schloss (Koňákov “Castle”) in Czech Republic, which allegedly represents an Early Cretaceous seep locality ( Kiel & Peckmann 2008; Kaim et al. 2013b). The material of Ascher (1906) is apparently lost precluding detailed comparisons. Also similar are specimens referred to as Calliotropis sp. from Eocene and Miocene seep deposits of Barbados ( Gill et al. 2005).

Distribution. Type locality only.

Etymology. From Latin rēticulātus, made like a net.

Figures

FIGURE 3. A. Limpet gastropod indet. from Valanginian (Early Cretaceous) seep carbonates at Bear Creek, Colusa County, California, USA; GZG. INV. 84967. B – D. Chilodonta? reticulata sp. nov. from Valanginian (Early Cretaceous) seep carbonates at Bear Creek, Colusa County, California, USA; holotype (GZG. INV. 84971). E – I. Hikidea osoensis sp. nov. from Valanginian (Early Cretaceous) seep carbonates at Bear Creek, Colusa County, California, USA. E – G. Holotype (GZG. INV. 84968). H. Paratype (GZG. INV. 84969). I. Juvenile (GZG. INV. 84970) displaying ornamentation of the early ontogenetic stage of the shell. J – O. Phanerolepida onoensis sp. nov. from Late Barremian (Early Cretaceous) seep site at Eagle Creek, Shasta County, California, USA; holotype (CAS 73130). J – K. Lateral views. L. Apical view. M. External prismatic shell layer. N. Internal nacreous shell layer. O. Detail of rhombohedric ornament pattern.