Jurilda Gründel, 1973

Gründel, Joachim & Nützel, Alexander, 2013, Evolution and classification of Mesozoic mathildoid gastropods, Acta Palaeontologica Polonica 58 (4), pp. 803-826 : 805-806

Genus Jurilda Gründel, 1973

Fig. 1C .

Type species: Mathilda (Jurilda) crasova Gründel, 1973 (= subjective junior synonym of Promathilda (Teretrina) concava Walther, 1951 ); original designation: Bajocian to Bathonian, Poland.

Included Jurassic species: The genus is present with numerous Jurassic species. Some examples are: Promathildia angularis lineata Jamničenko, 1987 , Toarcian–Aalenian; Mathilda wonwalensis Schröder, 1995 , Valanginian; Promathildia conoidea Gründel, 1997 , Bajocian; Promathildia naricata Gründel, 1997 , Bathonian–Callovian; Promathildia pommerana Gründel, 1997 , late Bathonian–early Callovian.

Emended diagnosis.—Shell slender to moderately broad; protoconch transaxial to almost coaxial, smooth or with radial folds; teleoconch with two primary spiral ribs; abapical rib may be strong, keel−like; few secondary spiral ribs can occur; spiral ribs intersected by strengthened growth lines; intersections are not or only slightly nodular; strengthened growth lines prosocline, straight to weakly prosocyrt between adapical suture and abapical spiral rib and nearly orthocline from the abapical spiral rib to the abapical suture; backmost point of growth lines on abapical primary spiral rib; faint micro−ornament of spiral striae present in some species; base more or less convex; aperture oval, rounded, sometimes (always?) with anterior siphonal canal.

Stratigraphic and geographic range.—Possible Triassic representatives of Jurilda are still doubtful and may belong to the genus Teretrina Cossmann, 1912 (AN and JG personal observations). The type species, Turritella bolina Münster, 1841 , from the Late Triassic Cassian Formation has growth lines

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

which are distinctly opisthocyrt between the adapical suture and the abapical spiral rib, i.e., their cenit is situated above the abapical primary spiral rib. However, other species which have been described as Promathildia species by Bandel (1995) have a course of the growth lines including axial ornaments similar to that of the Jurassic species. The first certain members of Jurilda are of Hettangian age. For instance Chapuis and Dewalque (1854), Terquem and Piette (1868), and Piette (1855) reported species which according to their descriptions and illustrations should be classified to Jurilda . Jurilda is at least present until the Early Cretaceous ( Schröder 1995; Kaim 2004). The last occurrence of the genus is unclear. The genus is known from Germany, Poland, Italy, Ukraine.

Figures

Fig. 1. Type species and examples for Jurassic genera of the family Mathildididae. A. Mathilda angulata (Gründel, 1997), erratic boulder from Hohendorf near Wolgast 3/96/3, Germany, Callovian; from Gründel (1997: pl. 5: 73). B. Tangarilda subturritella (d’Orbigny, 1850), Kanonenberg near Halberstadt, Germany, Hettangian; from Gründel (2010: pl. 3: 3). C. Jurilda concava (Walther, 1951), borehole Kłęby (formerly Klemmen) 1/37, Poland, Bathonian; from Gründel (1997: pl. 1: 1). D. Tricarilda plana (Gründel, 1973), bore Kłęby (formerly Klemmen) 1/37, Poland, Callovian; from Gründel (1997: pl. 3: 41). E, F. The group of Turritella binaria (Jurilda or Tricarilda). These species were also originally included in Promathildia; see also Fig. 4. E. Alaria clathrata Terquem and Jourdy, 1871, Les Clapes, Bathonian; from Terquem and Jourdy (1871: pl. 4: 7). F. Turritella binaria Hébert and Eudes−Deslongchamps, 1860, La Motte Bourbon, early Callovian, Bayerische Staatssammlung für Paläontologie BSPG 2012 I 22.