Description of Aclis aurisparva n. sp. (Gastropoda, Aclididae) from the Pliocene of Emilia Romagna (N Italy)

August 29, 2017 | Autor: Vittorio Garilli | Categoria: Gastropods, Cenozoic
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15 Bollettino della Società Paleontologica Italiana, 48 (1), 2009, 15-19. Modena, 15 maggio 2009

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 Garilli & Messina (2006) recently discussed the occurrence of the eulimid gastropod genus Chileutomia Tate & Cossmann in Tate, 1898 in the Pliocene to Recent Mediterranean area and described a possible new species, reported as Chileutomia (?) sp., from the Pliocene of North Italy (Emilia Romagna, Campore). In the present paper we rediscuss the systematic attribution of this taxon on the basis of new well preserved shells from the same area and a new species of the family Aclididae is described. MATERIALS AND METHODS The study material consists of six shells, collected in the last two decades by one of us (L.B.) from the Pliocene sediments of Emilia Romagna, Northern Italy. In particular, five shells (L. Bertolaso collection) were recovered from the Lower Pliocene (Piacenzian) clayey beds cropping out at the Campore quarry (Salsomaggiore Terme, Parma, N Italy), the same locality where the broken shell of Garilli & Messina (2006) was collected (see Raffi & Taviani, 1985; Bianucci, 1997; Bertolaso & Palazzi, 1997, and Channel et al., 1994 for geographical location, paleoecological and stratigraphic information on this outcrop). One shell (L. Bertolaso collection) was recovered from the clays cropping out near Ca’ de Fii, about 3.5 Km N of Castellarano (Reggio Emilia). As far as we are aware, no detailed stratigraphic information is available for the deposit of Ca’ de Fii which belongs to ISSN 0375-7633

the Lower Pliocene-Lower Pleistocene “Argille Azzurre” (Vai, 1988) or “Argille di Lugagnano” (Arrigoni et al., 1965) formation (Losacco et al., 1964; Cita et al., 2006; Bosellini et al., 2003). The lower circalittoral to epibathyal molluscan assemblage from this outcrop is comparable with that from the Piacenzian of Campore (as described by Raffi & Taviani, 1985), though the former has a lower diversity. Anyway a prudent approach suggests that an Early to early Middle Pliocene age could be assigned to the deposit of Ca’ de Fii, as supported by the occurrence of Mitrella compta (Bronn, 1831) and, subordinately, Cerithiella genei (Bellardi & Michelotti, 1840) (see Marasti & Raffi, 1976 and 1977 for their stratigraphic meaning). Actually these species are representative of the Mediterranean Upper Neogene molluscs of tropical affinities, whose extinction occurred in the early Piacenzian, approximating the Mammoth Subchron (Raffi & Marasti, 1982). Four shells (holotype and paratypes 1-3) were studied by the scanning electron microscope using a Philips XL 30 ESEM. Particular attention was given to protoconch and teleoconch microsculpture as possible taxonomic characters at species level. The number of protoconch whorls was counted according to Verduin’s method (1977). SYSTEMATICS The systematics of the family Aclididae, as well as other supposed Ptenoglossa (see Collin, 2002 and 2004 for a short overview on this suborder), is still uncertain.

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According to Warén (in Giannuzzi-Savelli et al., 1999, p. 7) most part of the genera and species traditionally included in this family could be placed in the Heterobranchia, as suggested by some data from living species. For the moment being, we maintain the placement in the Ptenoglossa, following the systematic proposed by Giannuzzi-Savelli et al. (1999). Class GASTROPODA Cuvier, 1797 Order NEOTAENIOGLOSSA Haller, 1882 Suborder PTENOGLOSSA Gray J.E., 1853 Superfamily JANTHINOIDEA Lamarck, 1810 Family ACLIDIDAE Sars G.O., 1878 Genus Aclis Lovén, 1846 Type species - Alvania supranitida Wood S.V., 1842 by monotypy. Aclis aurisparva n. sp. (Pl. 1, figs. 1-15) 2006 Chileutomia (?) sp. GARILLI & MESSINA, pp. 198-199, Fig. 1c, Pl. 1, figs. 6-7, 9-10.

Description - Shell conical, macroscopically polished, rather thin and minute, 2.5 mm in height and 0.95 mm in width (in holotype). Protoconch multispiral, conical and elongated, 0.6 mm in height (paratype 1), with a rather immersed nucleus and slightly convex whorls. Protoconch I consisting of little less than one smooth whorl; protoconch II formed by about 2.3 whorls, with

numerous growth scars running from suture to suture and irregularly spaced. Growth scars sinuous, prosocirte and opisthocirte in the abapical and in the adapical portion of the whorl respectively. Protoconch/ teleoconch boundary marked by a sinuous scar. Teleoconch formed by 2.5-5 strongly convex whorls often bearing expanded varicose labial processes and forming a moderately pronounced subsutural ramp in the area near the varicose processes. Labial processes are evident from the penultimate whorl and may be well to moderately expanded adapically and clearly halfdetached, or reduced to very few detached prominent scars. Angular distance between them of about 90° and 180°. Teleoconch microsculpture consisting of numerous (35-40 on the penultimate whorl of paratype 2), fine and moderately raised spiral threads, somewhat discontinuous, becoming coarser and more closely spaced on subsutural area. Teleoconch is crossed by irregularly spaced, moderately marked and slightly curved, opisthocline growth lines, and few rough and very irregular raised scars. Sutures slightly inclined and moderately deep. Last whorl making up little more than one half of the total shell height. Aperture ovate, higher than broad, extended in its lower part, making up about two thirds of last whorl height and one third of total shell height. Outer lip flattened in the lower part, and folded in the remaining part, where a sort of slight concavity occurs along the edge. This concavity appears deeper on the uppermost area, close to the contact with the body whorl, where the lip expansion may form a short wing-shaped extension, making the peristoma ear-shaped. Inner lip curved and with a thin 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 Emilia, N Italy.

Scale bars = 100 μm in figs. 1-4, 10-11; = 50 μm in figs. 5, 7, 15.

L. Bertolaso, V. Garilli - A new Pliocene aclidid gastropod

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Bollettino della Società Paleontologica Italiana, 48 (1), 2009

Narrow umbilical chink, partially covered by the expansion of the inner lip. Type material - Holotype and paratypes 1-4 are housed in the Museo di Zoologia of the University of Bologna (MZB), paratypes 5 and 6 are housed in the Dipartimento di Geologia e Geodesia of the University of Palermo (DGUP), coll. V. Garilli. Holotype (2.5 mm x 0.95 mm, catalogue number MZB45642), paratype 1 (1.3 mm x 0.6 mm, catalogue number MZB45638), paratypes 2 (1.2 mm in height, catalogue number MZB45639), 4 (1,2 mm in height, catalogue number MZB45641), 5 (catalogue n° CAPA001/536, ex F75A coll. S. Palazzi, the broken shell illustrated by Garilli & Messina, 2006, pl. 1, figs. 6-7, 910 and Fig. 1c) and 6 (1.05 mm x 0.5 mm, catalogue number DGUP CAPA002/537) are from the Pliocene deposit at the Campore quarry, Salsomaggiore Terme, Parma, Emilia Romagna, North Italy; paratype 3 (1.3 mm in height, catalogue number MZB45640) is from the Pliocene clays cropping out at an abandoned quarry next to Ca’ de Fii, about 3.5 Km N of Castellarano, Reggio Emilia, North Italy (44°32’16”N 10°45’00”E). Type locality - The Pliocene bluish clay cropping out in the Campore quarry, Salsomaggiore Terme, Parma, North Italy. Etymology - After the Latin auris (ear) and parva (small), referring to the ear-shaped peristoma, more clearly shown by paratype 1. Distribution - Aclis aurisparva n. sp. is only known from the Pliocene (possibly Zanclean to early Piacenzian) lower circalittoral to epibathyal deposits from Campore and Ca’ de Fii, Emilia Romagna (N Italy). Comparisons and remarks - The general shell shape, the characters of protoconch and aperture, and the fine spiral sculpture exclude the placement of this species in Chileutomia Tate & Cossmann in Tate, 1898. This genus is characterized by more markedly varicose shell with an almost pyriform aperture provided with a sinus in the upper part of the outer lip. Admittedly, the characteristic incremental scars (also forming varicose labial processes) occurring in Aclis aurisparva n. sp. are quite common in the families Muricidae, Cymathiidae and Epitoniidae, and even vetigastropods show similar processes (A. Warén, 2008, personal communication). Expanded labial processes also occur in the genus Hoplopteron Fischer, 1876, tentatively assigned to Eulimidae (Warén, 1984). However this genus (as illustrated by Warén, 1984, fig. 108) shows markedly expanded varices, its aperture is almost pyriform, and the teleoconch whorls lacks ornamentation and are less convex, particularly when comparing with the Eocene type species of Ptereulima (a synonym of Hoplopteron according to Warén, 1984, p. 68, fig. 161). The general teleoconch and protoconch shape, and the ovate aperture of the new species indicate a strong affinity with Aclididae, though all these characters may also occur with similar patterns in the families Epitoniidae and Eulimidae (A. Warén, 2008, pers. comm.). As an

example, the Mediterranean Aclis attenuans Jeffreys, 1883 and the Atlantic A. walleri Jeffreys, 1867 have a general shell shape very close to that of Aclis aurisparva n. sp., with which they also share the expansion of the lower part of the aperture, the shape of the umbilicus and the occurrence of numerous irregular scars, the last two features being common in the genus Aclis (see Bouchet & Warén, 1986, fig. 726-727 and 730-732 for Recent shells of A. attenuans and A. walleri and Di Geronimo & La Perna, 1997, pl. 4, fig. 10 for Pleistocene A. attenuans). Also the sinuous scars occurring on protoconch II are very similar to that shown by A. walleri. The extremely fine spiral striation shown by A. aurisparva n. sp. is another significant character. This microsculptural pattern is not found in the Epitonidae and scarcely represented in the Eulimidae, but seems widespread in the family Aclididae: e.g. Aclis crassilirata (Cossmann, 1900), Eocene of France, Bois Gouët; A. carolinensis Bartsch, 1911, North Carolina, Recent; A. thesauraria Melvill, 1904, Gulf of Oman, Recent (A. Warén, 2008, pers. comm.). Also the supposed Aclididae Hemiaclis hyalina (Watson, 1880), from the northeastern coasts of Brazil (Mello et al., 2003), shows a similar sculpture (see Mello et al., 2003, fig. 1e). A spiral microsculpture similar to that of Aclis is present in some eulimids, such as Pelseneeria Koeler & Vaney, 1908 (see P. striata Bouchet & Warén, 1986, figs. 994-995), whereas other genera of the same family (e.g. Amamibalcis Kuroda & Habe, 1950, Annulobalcis Habe, 1965, Arcuella Nevill, 1874 and Trochostilifer Warén, 1980) have different, much more pronounced spiral sculpture (see Warén, 1984 and Warén et al., 1984). Aclis aurisparva n. sp. shows a remarkable range of variation in shape. Whereas the paratype 1 shows a more slender, elongate shell, paratypes 2 and 3 have broader shells. Following Bouchet & Warén (1986), this variation, rather common in the genus Aclis, is likely due to sexual dimorphism (see Bouchet & Warén, 1986, pp. 726-727 and 730-732 for A. attenuans and A. walleri and Giannuzzi-Savelli et al., 1999, figs. 110 and 111 for A. attenuans and A. gulsonae (W. Clark, 1850)). We noted the same variation among some Mediterranean Mio-Pliocene (from North Italy and South Turkey, L. Bertolaso collection) apparently smooth Aclis spp., more or less related to the A. attenuans-A. walleri group or with a somewhat angulated base. CONCLUDING REMARKS Chileutomia miranda (Dautzenberg, 1925) remains the sole known representative of its genus in the Pliocene to Recent Mediterranean area, whereas Chileutomia (?) sp. of Garilli & Messina (2006) is proved to be an aclidid species, herein described. Aclis aurisparva n. sp. is well characterized by its ear-shaped peristoma and the presence of a microsculpture, and cannot be confused with congeners. It is noteworthy that among the recorded Aclis species from the Mediterranean Pliocene (Tabanelli, 1997, listed 14 Plio-Pleistocene species from Italy) only A. attenuans (including the Mediterranean citation of A.

L. Bertolaso, V. Garilli - A new Pliocene aclidid gastropod

walleri), A. brugnoniana De Stefani & Pantanelli, 1879 and A. gulsonae var. subappenninica Sacco, 1891 (the last two are poorly known, needing to be revised) have, at least apparently, no spiral sculpture. However the occurrences of the Pliocene A. aurisparva n. sp. and the above mentioned Mio-Pliocene undetermined Aclis spp. (our material from Italy and Turkey, under study) allows to suppose that more (macroscopically) polished aclidid species lived in the Mediterranean area during the Neogene. ACKNOWLEDGMENTS We would like to thank Anders Warén (Swedish Museum of Natural History, Stockholm) for the useful discussion and comments on the systematic placement of Aclis aurisparva n. sp. He also reviewed the submitted manuscript. Thanks are also due to Luca Galletti (APEMA, Research and Educational Service, Palermo) for the help in providing SEM images. We are grateful to Marina Cantelli and Bruno Sabelli (Museo di Zoologia, University of Bologna) who provided catalogue numbers. Rafael La Perna (Dipartimento di Geologia e Geofisica, University of Bari) reviewed the manuscript and provided valuable comments.

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