1,720,982 research outputs found
Phyletic relationships and ecological implications between Pagodula vaginata (De Cristofori & Jan, 1832) and Pagodula echinata (Kiener, 1840) (Gastropoda, Muricidae)
No full textTwo closely related species, Pagodula vaginata (De Cristofori & Jan, 1832) and Pagodula echinata (Kiener, 1840), have been recently distinguished (Bauchet & Warén, 1985) on the grounds of larval shell morphology. The former has a multispiral protoconch, indicating a planktotrophic development, whilst the latter has a paucispiral protoconch, referable to a non-planktotrophic development. Both species occur in the Pleistocene deposits from Southern Italy. At that time, the two species lived in ecologically segregated populations, Pagodula vaginata being linked to deep-shelf and upper-slope bottoms, and Pagodula echinata to deeper bathyal bottoms. The extinction of Pagodula vaginata, in the upper part of the Lower Pleistocene or in the Middle Pleistocene, was probably caused by the Quaternary cooling. Pagodula echinata could then spread upward to about 100 m, attaining its present bathymetric range. The origin of Pagodula echinata is referred to Pagodula vaginata through a process involving the larval development, known as «loss of planktotrophy». Such a process probably occurred in the Mediterranean during the Middle- Upper Pliocene, within a general development of deep-sea benthos
Dyolia N. gen. from the European Miocene-Pleistocene (Protobranchia : Nuculanidae)
No full textThe nuculanids Leda mendax Meneghini in Appelius, 1871, from the Plio-Pleistocene of Italy and Leda reussi Hörnes, 1865, from the Middle Miocene of Austria, are almost equilateral in shape, not rostrate, with a very shallow pallial sinus and a posterior radial swelling terminating in a rounded postero-ventral projection. Such a combination of shell characters is known only in these two species. For them, Dyolia n. gen. is proposed, with Leda mendax as type species. Relations with other nuculanids and the origin of Dyolia n. gen. are unclear. Taphonomic and morphofunctional observations on Dyolia mendax and D. reussi point to a specialization for muddy, soupy bottoms of the inner shelf, as shallow borrowers
Some quaternary bathyal eulimids from the Mediterranean, with descriptions of two new species (Gastropoda, Eulimidae)
No full textThree bathyal species of the family Eulimidae are reported from the Pleistocene of Southern Italy, Eulima bilineata Alder, 1848, Melanella seguenzai n. sp. and Campylorhaphion famelicum (Watson, 1883). M. seguenzai n. sp. is markedly close to the Recent Mediterranean Melanella glypta Bouchet & Warén, 1986. Haliella tyrrhena n. sp., possibly from the Pleistocene as well as from the Holocene, is described from bathyal bottoms in the Tyrrhenian Sea. It is notably close to H. canarica Bouchet & Warén, 1986 from the Canary Islands. Other incompletely known deep-sea eulimids from the Mediterranean Pleistocene are briefly discussed
Homalopoma emulum (Seguenza, 1876), a bathyal cold stenothermic gastropod in the Mediterranean Pleistocene
No full textHomalopoma emulum (SEGUENZA, 1876) is a poorly known gastropod from the bathyal deposits of the Mediterranean Lower Pleistocene (Strait of Messina area). Its affinity with Homalopoma globuloides (DAUTZENBERG & FISCHER, 1896), living on the bathyal bottoms of the Northeast Atlantic Ocean (Azores and Gulf of Biscay), is very high and the two species are more closely related than two simply congeneric species. Homalopoma emulum belongs to a category of Mediterranean Plio-Pleistocene deep-water species characterized by remarkable taxonomic, morphologic and ecologic affinities with deep-water species from the Atlantic Ocean, or extra-Mediterranean areas in general. Such affinities seem to indicate a cold-stenothermic character, incompatible with the present deep homothermy in the Mediterranean Sea. The reason for the extinction of these species is referred to homothermic episodes which took place cyclically during the interglacial phases of the Upper Pleistocene. A progressive and selective extinction of these species led to the present lack of cold-stenothermic species in the Mediterranean deep benthos
Ledella Verrill and Bush 1897
No full textGenus Ledella Verrill and Bush, 1897 Type-species Ledella bushae Warén, 1978. Warén (1978, 1981) contributed to the definition of the genus Ledella and its type-species (ICZN, 1985), referring to this genus species with a rather solid shell and hinge, a well-developed blunt rostration and a posteriorly inclined umbo. Warén (1978) also stated that ' Yoldiella may be separated [from Ledella] by having a less rounded shell which is more compressed and has a less solid hinge'. However, there is a group of fossil and living European species which differs from the typical Ledella species in having a less inclined umbo and a slightly keeled and markedly pointed rostrum. These species should be more properly attributed to Ledella, rather than the confused genus Yoldiella. This group includes the living Ledella messanensis (Jeffreys, 1870), L. folini (Warén, 1878), probably also L. pustulosa (Jeffreys, 1876), and the Pleistocene L. rectidorsata (Seguenza, 1877), the Pliocene L. seminulum (Seguenza, 1877) and the Miocene L. peraffinis (Seguenza, 1877) and L. glabra Laghi and Palazzi, 1989.Published as part of La Perna, R., 2004, The identity of Yoldia micrometrica Seguenza, 1877 and three new deep-sea protobranchs from the Mediterranean (Bivalvia), pp. 1045-1057 in Journal of Natural History 38 on page 105
Distribution pattern of macrobenthic assemblages along the Ideale Section of the Montalbano Jonico succession (southern Italy)
No full textLa collezione Cerulli-Irelli e la diversità malacofaunistica del Pleistocene inferiore mediterraneo.
No full textYoldiella micrometrica
No full textYoldiella micrometrica (Seguenza, 1877) (figure 1 a–d) Yoldia micrometrica sp. n., Seguenza, 1877a: 96. Yoldia micrometrica, Seguenza, 1877b: 21, pl. 4, figure 22–22c. Type material. The type material is lost and a neotype is here designated (left valve, MZB 40659). Type locality. Vallone Catrica (southern Calabria), Pleistocene bathyal muddy beds. Material examined. Four vs from the neotype locality. Description. Shell small, slightly inequilateral, ovate-trigonal, elongated, shortly and bluntly rostrated, moderately inflated, rather sturdy for size. Umbo at midline, small and moderately projecting from shell outline, slightly opisthogyrate. Anterodorsal margin slightly convex, rapidly and smoothly sloping to form a broadly rounded anterior margin. Postero-dorsal margin straight, sloping to form a short, well-rounded rostrum, slightly below shell height midline. Ventral margin wide, evenly curved to faintly straight near midline. Surface with fine growth lines, becoming well incised, and irregularly spaced lines towards ventral margin. Hinge plate moderately thick, making a 130 ° angle, anterior row a little longer than posterior one. Dentition taxodont with chevron-shaped teeth, numbering seven anteriorly and six posteriorly in neotype. Ligament pit elliptic, shallow. Muscle scars roundish, well impressed. Pallial line fairly well impressed, forming a shallow, hardly distinct posterior sinus. Prodissoconch D-shaped, ca 300 µ m long. Neotype 2.08 mm in length, 1.31 mm in height, 0.50 mm in breadth. Distribution. Only known from Pleistocene bathyal beds in southern Italy (Messina Strait area). The species was originally reported from a locality near Messina, where the type horizon is no longer exposed. The neotype is from a nearby locality on the Calabrian side of the Messina Strait, where beds of the same age and bathyal environment outcrop (Di Geronimo and La Perna, 1997). Remarks. Yoldiella micrometrica has a somewhat 'triangular' outline, because of the rather low position of the rostrum and the weak convexity of the ventral margin. This shape was described as ' trigona ' (triangular) by Seguenza (1877a) in the brief original description. Later, when it was more extensively described, Seguenza (1877b) wrote: ' oblonga-subtrigona ', 'This very small species is well distinct by the trigonal shape…'. A well-distinct small living species has been up to now misidentified as Y. micrometrica (see below) and a neotype is here designated in order to fix the identity of the fossil species.Published as part of La Perna, R., 2004, The identity of Yoldia micrometrica Seguenza, 1877 and three new deep-sea protobranchs from the Mediterranean (Bivalvia), pp. 1045-1057 in Journal of Natural History 38 on pages 1047-104
Ledella marisnostri La Perna 2004, n. sp.
No full textLedella marisnostri n. sp. (figure 4 a–e) Type material. Holotype (right valve, MZB 40663) and five paratypes (loose valves, author's collection). Type locality. Cruise ' Interreg Italia-Albania', southern Adriatic, st. 55, 40 ° 00 ∞ 59 ◊ N, 19 ° 08 ∞ 55 ◊ E, 976 m. Material examined. Only the type material. Description. Shell small, ovate, moderately convex and elongated, inequilateral, thin-walled. Umbo rather large, weakly projecting from shell outline. Antero-dorsal margin sloping, slightly convex, smoothly curving into a well-rounded anterior margin. Postero-dorsal margin sloping, longer than antero-dorsal one, slightly convex, curving into a moderately developed blunt rostrum at shell height midline. Ventral margin wide, strongly convex, evenly rounded except for an obscure posterior sinuosity marking out rostrum. Hinge plate moderately thick, making a 130 ° angle, with rows of similar length. Dentition taxodont, with chevron-shaped teeth, numbering seven anteriorly and six posteriorly in holotype. Ligamental pit rather deep, somewhat triangular. Muscle scars and pallial line indistinct. Surface with fine growth striae, some of them more incised. Periostracum thin, shiny, yellowish. Prodissoconch elliptic, ca 250 µ m long. Holotype 2.08 mm in length, 1.53 mm in height, 0.50 in breadth. Paratypes 1.65–2.27 mm in length. Etymology. After Mare nostrum, Latin name for the Mediterranean Sea. Distribution. Only known from the type locality. Remarks. The sole species of Ledella so far known from the Mediterranean is L. messanensis, with a wide latitudinal distribution through the European Atlantic (Warén, 1978, 1989; Allen and Hannah, 1989; Salas, 1996). However, it differs markedly from the present species by being bigger (up to ca 5 mm), much more solid, and with a longer and sharper rostrum. Also, the juveniles of L. messanensis are somewhat pointed posteriorly and thick-shelled. A North Atlantic species, Ledella confinis (Smith, 1885), revised by Warén (1978), may be somewhat reminiscent of L. marisnostri n. sp., but it is larger, more solid, with a more pointed rostrum and with a strongly oblique umbo. The present species seems close to the L. messanensis group, although it is not particularly similar to any of the European species.Published as part of La Perna, R., 2004, The identity of Yoldia micrometrica Seguenza, 1877 and three new deep-sea protobranchs from the Mediterranean (Bivalvia), pp. 1045-1057 in Journal of Natural History 38 on pages 1052-105
MARGINELLIFORM GASTROPODS FROM THE EARLY PLEISTOCENE OF GALLINA (REGGIO CALABRIA, SOUTHERN ITALY)
No full textMarginelliforms are an informal group of marine gastropods including two families: Marginellidae Fleming, 1828 and Cystiscidae Stimpson, 1865. They are convergent families, mainly distributed in warm to warm-temperate waters, particularly difficult to be identified at species level, because of the their smooth, featureless shell. The present-day Mediterranean hosts a fairly diverse marginelliform fauna, but the genera with stronger tropical affinity, such as Marginella Lamarck, 1799, are missing since the Early-Middle Pliocene.
Gallina is a fossiliferous locality on the Calabrian side of the Messina Strait. Its rich fossil fauna was studied by Seguenza (1879), who reported hundreds of species, mainly molluscs. He also remarked the unusual character of this “Astian” deposit as “facies misto”, as its rich assemblage consists of a mixture of shallow- and deep-water species. For this locality, Seguenza reported six species of marginelliforms.
A small, poorly exposed outcrop, was recently discovered near Gallina. The outcrop contains a richly fossiliferous bed, 20 cm thick, consisting of clayey sands (level B), whose fauna corresponds to that studied by Seguenza. It overlays a clayey sandy bed with the Boreal Guest Pseudamussium septemradiatum (level A), and is overlaid by a poorly fossiliferous silty-sandy bed (level C). The nannoplankton assemblage from level A points to the large Gephyrocapsa Zone, while the assemblage from level C is indicative of the small Gephyrocapsa Zone (Early Pleistocene). The nannoplankton assemblage from the richly fossiliferous level B turned out to be totally reworked. All the three levels, particulalry the intermediate one (B), are interpreted as formed via gravitative flows.
The marginelliform fauna from the “Seguenza level” (B) consists of some specie of the genus Granulina Jousseaume, 1888, two species of Gibberula Swainson, 1840 and one species of Marginella. One of these species corresponds to Marginella ovulaeformis Seguenza, 1879, described from Gallina. It seems a valid species, as Granulina ovulaeformis (Seguenza), but further studies are needed.
The occurrence of a Marginella species at Gallina was quite unexpected, as none of the species reported by Seguenza can be actually referred to such a genus (widely used in the past literature). Furthermore, the species is relatively large (ca 10 mm in shell height) and fairly frequent in the assemblage. The abundant material (about 70 shells) is well preserved and reworking from older sediments is excluded. Most probably, it is an undescribed species, markedly different from the large sized M. aurisleporis (Brocchi, 1814), the last representative of Marginella in the Mediterranean Pliocene. It is worth remarking that several species of Marginella were reported from the Early-Middle Pliocene of Estepona, near the Gibraltar Strait (Landau et al., 2006). The Marginella species from Gallina testifies the local survival of this thermofilic genus through the Early Pleistocene in a Mediterranean “sanctuary”. Indeed, since the Pleistocene at least, the Messina Strait accommodates a high abundance and diversity of species, with many endemisms and primarily Atlantic species forming rich populations
- …
