Cryptaulax damboreneae, Ferrari, 2009

Ferrari, S. Mariel, 2009, Cosmopolitan Early Jurassic marine gastropods from west-central Patagonia, Argentina, Acta Palaeontologica Polonica 54 (3), pp. 449-461 : 452-454

Cryptaulax damboreneae sp. nov.

Fig. 3B–D .

Etymology: Dedicated to Susana E. Damborenea.

Type material: Holotype, MPEF−PI 1878 a and b (part and counterpart); well preserved teleoconch; paratypes, MPEF−PI 1877 and MPEF−PI 1872 a and b; poorly preserved teleoconch fragments.

Type horizon: Osta Arena Formation, Lower Toarcian, Jurassic .

Type locality: PA 06 site, “ El Córdoba ” fossiliferous locality .

Other material.—MPEF−PI 1875, MPEF−PI 1868, MPEF−PI

1876, MPEF−PI 1880, MPEF−PI 1865, MPEF−PI 1884, and MPEF−PI 1864; poorly preserved teleoconchs.

Diagnosis.—Anomphalous and turriculate shell. Ornament predominantly axial, with spiral and nodose elements. Two weak spiral ribs of second order appear on adult teleoconch between three strong primary spiral ribs. Circular and holostomatous aperture.

Description.—Dextral, small−sized and high−spired shell, anomphalous, slender and turriculate. Protoconch is not preserved. Teleoconch comprises eight whorls with gradate outline. Deeply incised sutures. Ornament with nodose, spiral and axial elements. Axial elements are predominant and consist of orthocline and narrow axial ribs that run from suture to suture. Axial ribs regularly spaced, 8–9 per whorl. Axial ornament intercepts spiral elements. The latter comprises three strong spiral ribs; two of which are situated somewhat above and below the suture; the third spiral rib is median. On the sixth teleoconch whorl two weak secondary spiral ribs appear between the primary ribs. At the intersection of axial and spiral elements, strong conspicuous and acute nodes are present; nodes are strongest on primary spiral ribs. Base is strongly convex with five acute spiral ribs. The aperture is holostomatous and oval.

Dimensions.— See Table 1.

Remarks.—The present material shows the characters which are typical of Cryptaulax (compare Gründel 1999; Kaim, 2004). Most representatives of the genus are characterized by mode of occurrence of the weak secondary spiral ribs during ontogeny. The presence of two such spiral ribs on sixth teleoconch whorl separates Cryptaulax damboreneae sp. nov. from other species of the genus.

Cryptaulax variformatum Bandel, 1994 from the Early Jurassic of Peru ( Bandel 1994: 140, pl. 3: 16, 17, 19), is similar to C. damboreneae sp. nov. but is more high−spired than the Argentinean species, has a stronger spiral ornament, and its aperture is quadrangular rather than oval. Cryptaulax ? sp. of Gründel (2001: 54, pl. 3: 10) from the Bathonian of Chile resembles C. damboreneae sp. nov. in having a dominant axial ornament with at least one abapical spiral rib.

Cryptaulax sp. cf. protortile Cox, 1969 from the Early and Middle Jurassic of New Zealand ( Bandel et al. 2000: 89, pl. 6: 9, 11–13), is very similar to C. damboreneae sp. nov. However, this species (a juvenile teleoconch) has stronger spiral ribs. Cryptaulax sp. 1 and Cryptaulax sp. 2 , both described by Gründel (2003: 26, 27, pl. 6: 8–12, pl. 7: 1) from the Sinemurian of Germany, share some features with C. damboreneae sp. nov. However, Cryptaulax sp. 1 has weakly prosocline axial ribs and two basal spiral ribs, and Cryptaulax sp. 2 has ten opistocline axial ribs on the last whorl. Kaim (2004) described several species from the Middle Jurassic of Poland which resemble C. damboreneae sp. nov. Cryptaulax quenstedti (Walther, 1951) (see: Kaim 2004: 36, fig. 21; Gründel 1974: 842, pl. 2: 9–15; Gründel 1999: 18; pl. 4: 8–12 identified as Cryptaulax ex. gr. bellayensis sp. 3) differs from the Argentinean species only in having a weak median spiral rib or, a second order of one additional spiral rib between the strong median and adapical spiral ribs. Cryptaulax sp. 1 of Kaim (2004: 34, fig. 19) differs from C. damboreneae sp. nov. in having a weak fourth spiral rib on the sixth teleoconch whorl, and an additional fifth, weak spiral rib on the tenth teleoconch whorl. Cryptaulax sp. 2 of Kaim (2004: 34, fig. 19) is larger than the Argentinean species and has a second order of two weak spiral ribs on ninth teleoconch whorl. Cryptaulax shiptonensis ( Cox and Arkell, 1950) is similar to C. damboreneae sp. nov. in shell morphology. However, this European species has a second order of two median spiral ribs on the fourth or fifth teleoconch whorls (Kaim 2004: 34, fig. 20). Cryptaulax armata (Goldfuss, 1844) differs from C. damboreneae sp. nov. in having a weaker median spiral rib on the mature teleoconch (Kaim 2004: 37, fig. 22). Cryptaulax muricata (Sowerby, 1825) is larger than C. damboreneae sp. nov., has four strong spiral ribs on the last teleoconch whorl, lacks secondary weak spiral ribs, and the nodes result from the intersection with weakly prosocline axial ribs (Kaim 2004: 32, fig. 17). Cryptaulax undulata (Eudes−Deslongchamps, 1842) is more elongated than the Argentinean species, has five strong spiral ribs intersecting the axial ribs, and the peristome has an anteriorly directed siphonal channel (Kaim 2004: 33, fig. 18). C. echinata (von Buch, 1831) differs from C. damboreneae nov. sp. in having two conspicuous and nodose ribs on all teleoconch whorls (Kaim 2004: 38, fig. 23). Cryptaulax sp. 3 of Kaim (2004: 43, fig. 27) and Cryptaulax? mutabilis (Gerasimov, 1955) are similar to the species here described, but the whorls of C. sp. 3 have a straighter outline and fewer axial ribs while C.? mutabilis has a more Bittium −like teleoconch (Kaim 2004: fig. 28).

Stratigraphic and geographic range.— PA−06 site, from “El Córdoba ” fossiliferous locality, Chubut province, Argentina. Osta Arena Formation, Lower Toarcian , Lower Jurassic .

Figures

Fig. 3. Early Jurassic gastropods from Argentina A. Zygopleuridae? gen. et sp. indet., “El Córdoba” fossiliferous locality, Chubut Province. MPEF−PI 1886, latex cast of external mold in lateral view. B–D. Cryptaulax damborenae sp. nov., “El Córdoba” fossiliferous locality, Chubut Province. B. MPEF−PI 1878b, holotype, latex cast of external mold in lateral (B1, B2) and basal (B3) views, ornament detail (B4). C. MPEF−PI 1877, paratype, latex cast of external mold of incomplete teleoconch in apertural view. D. MPEF−PI 1872b, paratype, latex cast of external mold of incomplete teleoconch in lateral view. E. Cryptaulax cf. damboreneae sp. nov., Cerro Puchenque locality, Mendoza Province. MLP 18742, latex cast of external mold of incomplete teleoconch; adult teleoconch in lateral view. F–H. Cryptaulax nulloi sp. nov., “El Córdoba” fossiliferous locality, Chubut Province. F. MPEF−PI 1870, holotype, latex cast of external mold. Adult teleoconch in lateral view (F1), juvenile teleoconch in lateral view (F2). G. MPEF−PI 1861, paratype, latex cast of external mold in lateral and apertural view. H. MPEF−PI 1871, latex cast of external mold of incomplete teleoconch in lateral view (H1), and its ornament detail (H2). Scale bars 1 mm.