Description of Aclis Aurisparva N. Sp. (Gastropoda, Aclididae) from the Pliocene of Emilia Romagna (N Italy)
Total Page：16
File Type：pdf, Size：1020Kb
Bollettino della Società Paleontologica Italiana, 48 (1), 2009, 15-19. Modena, 15 maggio 200915 Description of Aclis aurisparva n. sp. (Gastropoda, Aclididae) from the Pliocene of Emilia Romagna (N Italy) Luca BERTOLASO & Vittorio GARILLI L. Bertolaso, Via Manzotti 35, I-42015 Correggio (Reggio Emilia), Italy. V. Garilli, APEMA Research and Educational Service, Via Alla Falconara 34, I-90136 Palermo, Italy; [email protected] KEY WORDS - Gastropoda, Aclididae, Aclis new species, Pliocene, N Italy. ABSTRACT - A new species of the family Aclididae is described from the Pliocene of Emilia Romagna (Northern Italy) as Aclis aurisparva n. sp. This species was formerly reported as Chileutomia (?) sp. (family Eulimidae) but the finding of new, well preserved material has allowed a correct systematic placement. This new species and other similar Mio-Pliocene congeners, with apparently-polished-shells (Italian and Turkish material, under study) close to the A. attenuans - A. walleri group, allow us to hypothesise that the Aclis species with smooth shells (or with a spiral microsculpture) from the Mediterranean Upper Neogene are more numerous than expected. RIASSUNTO - [Descrizione di Aclis aurisparva n. sp. (Gastropoda, Aclididae) dal Pliocene dell’Emilia Romagna (N Italia)] - Sulla base di nuovi ritrovamenti di materiale ben preservato, proveniente dal Pliocene (presumibilmente Zancleano-primo Piacenziano) dell’Emilia Romagna, viene ridiscussa la posizione sistematica del taxon precedentemente riportato come Chileutomia (?) sp. (famiglia Eulimidae). Tale taxon, qui descritto come Aclis aurisparva n. sp., è caratterizzato da una minuta ornamentazione spirale sulla teleoconca e da un marcato processo labiale varicoso il quale forma una caratteristica espansione del labbro esterno, particolarmente sviluppata negli esemplari subadulti. Aclis aurisparva n. sp. è confrontabile con A. attenuans e A. walleri, rispettivamente viventi in Mediterraneo ed Atlantico orientale, e con alcune specie fossili congeneriche ad esse particolarmente affini (in studio). La descrizione di questo taxon, e l’osservazione di altro materiale inedito, utilizzato per confronto, consentono di suggerire che le Aclis spp. lisce (o provviste di una fine microscultura spirale) del Neogene mediterraneo costituiscano un gruppo più numeroso di quanto desumibile dalla letteratura malacologia. INTRODUCTION the Lower Pliocene-Lower Pleistocene “Argille Azzurre” (Vai, 1988) or “Argille di Lugagnano” (Arrigoni et al., Garilli & Messina (2006) recently discussed the 1965) formation (Losacco et al., 1964; Cita et al., 2006; occurrence of the eulimid gastropod genus Chileutomia Bosellini et al., 2003). The lower circalittoral to Tate & Cossmann in Tate, 1898 in the Pliocene to Recent epibathyal molluscan assemblage from this outcrop is Mediterranean area and described a possible new species, comparable with that from the Piacenzian of Campore reported as Chileutomia (?) sp., from the Pliocene of (as described by Raffi & Taviani, 1985), though the former North Italy (Emilia Romagna, Campore). In the present has a lower diversity. Anyway a prudent approach suggests paper we rediscuss the systematic attribution of this taxon that an Early to early Middle Pliocene age could be on the basis of new well preserved shells from the same assigned to the deposit of Ca’ de Fii, as supported by the area and a new species of the family Aclididae is occurrence of Mitrella compta (Bronn, 1831) and, described. subordinately, Cerithiella genei (Bellardi & Michelotti, 1840) (see Marasti & Raffi, 1976 and 1977 for their stratigraphic meaning). Actually these species are MATERIALS AND METHODS representative of the Mediterranean Upper Neogene molluscs of tropical affinities, whose extinction occurred The study material consists of six shells, collected in in the early Piacenzian, approximating the Mammoth the last two decades by one of us (L.B.) from the Pliocene Subchron (Raffi & Marasti, 1982). sediments of Emilia Romagna, Northern Italy. In Four shells (holotype and paratypes 1-3) were studied particular, five shells (L. Bertolaso collection) were by the scanning electron microscope using a Philips XL recovered from the Lower Pliocene (Piacenzian) clayey 30 ESEM. Particular attention was given to protoconch beds cropping out at the Campore quarry (Salsomaggiore and teleoconch microsculpture as possible taxonomic Terme, Parma, N Italy), the same locality where the characters at species level. The number of protoconch broken shell of Garilli & Messina (2006) was collected whorls was counted according to Verduin’s method (see Raffi & Taviani, 1985; Bianucci, 1997; Bertolaso & (1977). Palazzi, 1997, and Channel et al., 1994 for geographical location, paleoecological and stratigraphic information on this outcrop). One shell (L. Bertolaso collection) was SYSTEMATICS recovered from the clays cropping out near Ca’ de Fii, about 3.5 Km N of Castellarano (Reggio Emilia). As far The systematics of the family Aclididae, as well as as we are aware, no detailed stratigraphic information is other supposed Ptenoglossa (see Collin, 2002 and 2004 available for the deposit of Ca’ de Fii which belongs to for a short overview on this suborder), is still uncertain. ISSN 0375-7633 16 Bollettino della Società Paleontologica Italiana, 48 (1), 2009 According to Warén (in Giannuzzi-Savelli et al., 1999, numerous growth scars running from suture to suture p. 7) most part of the genera and species traditionally and irregularly spaced. Growth scars sinuous, included in this family could be placed in the prosocirte and opisthocirte in the abapical and in the Heterobranchia, as suggested by some data from living adapical portion of the whorl respectively. Protoconch/ species. For the moment being, we maintain the placement teleoconch boundary marked by a sinuous scar. in the Ptenoglossa, following the systematic proposed Teleoconch formed by 2.5-5 strongly convex whorls by Giannuzzi-Savelli et al. (1999). often bearing expanded varicose labial processes and forming a moderately pronounced subsutural ramp in the area near the varicose processes. Labial processes Class GASTROPODA Cuvier, 1797 are evident from the penultimate whorl and may be Order NEOTAENIOGLOSSA Haller, 1882 well to moderately expanded adapically and clearly half- Suborder PTENOGLOSSA Gray J.E., 1853 detached, or reduced to very few detached prominent Superfamily JANTHINOIDEA Lamarck, 1810 scars. Angular distance between them of about 90° and Family ACLIDIDAE Sars G.O., 1878 180°. Teleoconch microsculpture consisting of Genus Aclis Lovén, 1846 numerous (35-40 on the penultimate whorl of paratype 2), fine and moderately raised spiral threads, somewhat Type species - Alvania supranitida Wood S.V., 1842 discontinuous, becoming coarser and more closely by monotypy. spaced on subsutural area. Teleoconch is crossed by irregularly spaced, moderately marked and slightly curved, opisthocline growth lines, and few rough and Aclis aurisparva n. sp. very irregular raised scars. Sutures slightly inclined and (Pl. 1, figs. 1-15) moderately deep. Last whorl making up little more than one half of the total shell height. Aperture ovate, higher 2006 Chileutomia (?) sp. GARILLI & MESSINA, pp. 198-199, Fig. than broad, extended in its lower part, making up about 1c, Pl. 1, figs. 6-7, 9-10. two thirds of last whorl height and one third of total shell height. Outer lip flattened in the lower part, and Description - Shell conical, macroscopically folded in the remaining part, where a sort of slight polished, rather thin and minute, 2.5 mm in height and concavity occurs along the edge. This concavity 0.95 mm in width (in holotype). Protoconch multispiral, appears deeper on the uppermost area, close to the conical and elongated, 0.6 mm in height (paratype 1), with contact with the body whorl, where the lip expansion a rather immersed nucleus and slightly convex whorls. may form a short wing-shaped extension, making the Protoconch I consisting of little less than one smooth peristoma ear-shaped. Inner lip curved and with a thin whorl; protoconch II formed by about 2.3 whorls, with expansion which is narrower along the columellar side. EXPLANATION OF PLATE 1 figs. 1-5 - Aclis aurisparva n. sp. Pliocene of Campore, Salsomaggiore Terme, Parma, N Italy. 1 - Protoconch of paratype 1 (MZB45638), showing the sinuous scars. 2 - Protoconch of paratype 1 (MZB45638), showing the sinuous scars, the protoconch I/protoconch II (black arrow) and protoconch/teleoconch boundaries (white arrows). 3 - Protoconch of paratype 1 (MZB45638), showing the sinuous scars and protoconch/teleoconch boundary (white arrows). 4 - Protoconch of paratype 2 (MZB45639), showing the sinuous scars. 5 - Protoconch of paratype 1 (MZB45638), showing the sinuous scars and the protoconch I/protoconch II boundary (black arrow). figs. 6-7 - Aclis aurisparva n. sp. Holotype (H = 2.5 mm, MZB45642). 6 - Apertural view of the shell. 7 - Detail of teleoconch microsculpture. figs. 8-10 - Aclis aurisparva n. sp. Paratype 1 (H = 1.3 mm, MZB45638). 8 - Apertural view of the shell. 9 - Dorsal view of the shell. 10 - Detail of the upper part of the outer lip. figs. 11, 13-15 - Aclis aurisparva n. sp. Paratype 2 (H = 1.2 mm, MZB45639). Pliocene of Campore, Salsomaggiore Terme, Parma, N Italy. 11 - Detail of the umbilical chink. 13 - Apertural view of the shell. 14 - Dorsal view of the shell. 15 - Detail of the spiral microsculpture. fig. 12 - Dorsal view of paratype 3 (H=1.3 mm, MZB45640), Pliocene of Ca’ de Fii, Castellarano, Reggio