Maurizio Sosso

The examination of chitons (Polyplacophora) associated with sandy bioclastic sediments collected in the southwestern Adriatic Sea (Mediterranean Basin) revealed the presence of three previously undescribed species: Leptochiton elisabettae sp. nov., L. gaiae sp. nov., and Ischnochiton falkori sp. nov. The latter two species preserve dried soft parts, allowing preliminary anatomical observations, particularly of the girdle. In addition, the studied sediments yielded valves of rare and recently described taxa (Leptochiton antondhorni, L. salicensis and Ischnochiton sigwartae), enabling refinement of their shell morphological characters. Notably, some species identified in these submerged deposits known only from disarticulated valves (L. salicensis and I. sigwartae) had been previously recorded exclusively from onshore Pleistocene deposits of Italy. Their presence in the Recent Mediterranean fauna remains unconfirmed and has so far been interpreted as representing palimpsest late Pleistocene fossils within this basin. The Polyplacophoran fauna of the Mediterranean basin presently comprises approximately 50 species, including a few taxa known only from putative last-glacial fossil records. It is foreseeable that this number will increase further, owing to more in-depth investigation of previously poorly explored habitats, not only in deep-sea environments, and to the increasingly widespread use of molecular techniques.

The European Cenozoic Polyplacophora has been reviewed, with a focus on the Oligocene to Pleistocene paleontological record. Based upon literature records and institution and private collections, we have critically revised 171 taxa, 152 of which are considered taxonomically valid. Among these, 35 are extant species with a fossil record, and 19 are of unclear taxonomic position. Nineteen species are described as new: Lepidopleurus pseudocajetanus sp. nov. (Miocene/Pleistocene), Lepidopleurus reitanoi sp. nov. (Pleistocene), Leptochiton corticellii sp. nov. (Pleistocene), L. prudenzae sp. nov. (Pliocene), L. rumani sp. nov. (Miocene), Hanleya fratrum sp. nov. (Pleistocene), H. sirenkoi sp. nov. (Pleistocene), Ischnochiton cluzaudi sp. nov. (Miocene), I. krohi sp. nov. (Miocene), I. lesporti sp. nov. (Miocene), I. sigwartae sp. nov. (Pleistocene), Stenosemus juliuspisai sp. nov. (Pliocene-Pleistocene, Recent?), S. praedolii sp. nov. (Miocene/Pleistocene), S. rossoae sp. nov. (Pleistocene), S. vendrascoi sp. nov. (Miocene), Rhyssoplax garillii sp. nov. (Pliocene/Pleistocene), Lepidochitona kieli sp. nov. (Miocene), Lepidochitona saitoi sp. nov. (Pleistocene), and Acanthochitona mathiasi sp. nov. (Miocene). The stratigraphic distribution of the genus Lucilina Dall, 1882 is extended to the Lower Oligocene. One of the species introduced herein (Stenosemus juliuspisai sp. nov.) is likely still living in the Mediterranean Sea. This revision serves as a necessary step in establishing a foundational baseline for understanding the evolutionary and biogeographic patterns of Polyplacophora in European seas through time up to the present.

The Mediterranean Sea houses a rather diverse chiton fauna (Mollusca: Polyplacophora). Four are here described as new, all based upon loose valves recovered from biogenic sediments: Leptochiton freiwaldi sp. nov., Hanleya schwabei sp. nov., “Ischnochiton” luquei sp. nov., Acanthochitona barbarae sp. nov. The updated Mediterranean Sea chiton fauna comprehends as many as 47 species, distributed in the families Leptochitonidae (15 species), Hanleyidae (3 species), Ischnochitonidae (7 species), Callistoplacidae (1 species), Chaetopleuridae (1 species), Callochitonidae (3 species), Chitonidae (5 species), Lepidochitonidae (6 species), Tonicellidae (1 species), Acanthochitonidae (5 species). Seven taxa are only known from loose valves: Leptochiton antondohrni, L. freiwaldi sp. nov., Hanleya schwabei sp. nov., “Ischnochiton” luquei sp. nov., Lepidochitona marcoi, Boreochiton ruber and Acanthochitona barbarae sp. nov. Similarly to other deep-sea mollusks described from the Mediterranean basin, some of them could possibly belong to last glacial Pleistocene submerged assemblages. On the contrary, Hanleya schwabei sp. nov. and Acanthochitona barbarae sp. nov. occur also at shallower depths, and are assigned to the modern Mediterranean fauna. The presence of the Atlantic taxon Chaetopleura angulata could be an accidental introduction into the Mediterranean. The species Tegulaplax hululensis, considered a Lessepsian immigrant, is a potentially forerunner of a more massive introduction of tropical Polyplacophora via the Red Sea. This study set a baseline for a better understanding of the evolutionary and biogeographic patterns of the Mediterranean Polyplacophora.

Sea-bottom sampling at bathyal depths off the Apulian margin (southwestern Adriatic Sea) recovered shelly biogenic sediments rich in mollusk remains. Noteworthy is the occurrence in such taphocoenoses of loose chiton valves, rarely reported in these environments. We identified four species of Polyplacophora, Leptochiton asellus (Gmelin, 1791), Belknapchiton alveolus (M. Sars MS, Lovén, 1846), Hanleya hanleyi (Bean in Thorpe, 1844), and the new species Leptochiton antondohrni. L. asellus (Gmelin, 1791) and B. alveolus are primarily of North Atlantic (boreo-celtic) affinity and thus considered to belong to last Pleistocene glacial assemblages, whose presence in the study area has long been ascertained. The same could be true for the valves of H. hanleyi and, possibly, Leptochiton antondohrni n. sp. Finally, we updated the list of mollusks found thus far in the deep-sea taphocoenoses of this area, including new records of North Atlantic-type taxa considered at present extinct in the Mediterranean basin.

Based on extensive new material, 2088 valves resulting from search sampling of ~500 kg of sediment, the Pliocene chiton biodiversity of the Mondego Basin (Portugal) is reassessed. Twelve species were identified, assigned to seven genera. Eight species are new for the Pliocene of Portugal, as well as two of the genera:Hanleya, Acanthochitona. Two taxa are described as new:Ischnochiton loureiroin. sp. andLepidochitona rochaen. sp. Until now, the polyplacophoran European Neogene record was too poorly known to be of help in generating a clear picture of the Miocene to present-day biogeography of the group. This new wealth of data from western Iberia, in conjunction with recent data from the Loire Basin Upper Miocene assemblages (France), allows clarification the Late Miocene to Recent eastern Atlantic and Mediterranean biogeography of the Polyplacophora. The northern range of warm-water northeast Atlantic and Mediterranean Polyplacophora experienced a sharp contraction since, at least, Late Miocene to Early Pliocene times. Warm-water chiton species represented in the Upper Miocene of the Loire Basin of NE France (European-West African Province) and the Pliocene of the Mondego Basin of central-west Portugal (Pliocene French-Iberian Province) are today confined to the southern Mediterranean-Moroccan Molluscan Province.UUID:http://zoobank.org/a2a550c0-caed-449a-aa45-9492c45f882e

This study describes the chiton fauna (Mollusca, Polyplacophora) from the marine Pleistocene coral reef deposits bordering the Red Sea coast and dating to the last interglacial epoch (Marine Isotopic Substage 5e, MIS5e). Twenty-one species were identified, of which only three were previously known from the Pleistocene of the Red Sea (Lucilina sueziensis, Acanthopleura vaillantii and Acanthochitona penicillata). Eight are recorded as fossil for the first time. Six are described as new (Lucilina confusa n. sp., L. aqabaensis n. sp., L. aegyptiaca n. sp., L. colantonii n. sp., “Onithochiton” vandingeneni” n. sp., and Acanthochitona interglacialis n. sp.) and two are assigned at generic level (Callochiton sp. and Craspedochiton sp.). Four of these new species (Lucilina confusa n. sp., L. aegyptiaca n. sp., L. colantonii n. sp. and “Onithochiton” vandingeneni n. sp.) are still living in the Red Sea, bringing to 28 the number of extant species known from the Red Sea. These Pleistocene Red Sea assemblages represent the most diverse chiton fauna yet reported from any interglacial deposit worldwide.

The paper covers 11 species of naticid gastropods occurring in the lower Serravallian (Upper Badenian) strata of western Ukraine (Central Paratethys). The studied material (over 1,700 naticids) represents six genera and 11 species, of which eight are new: Cochlis odovychenorum, Cochlis ukrainensis, Tectonatica anistratenkorum, Tectonatica pseudoprietoi, Euspira sirenkoi, Payraudeautia ermesi, Payraudeautia sabrinae and Payraudeautia varovtsiana. Additionally, we have also identified Euspira protracta (Eichwald, 1830), Polinices staszici (Friedberg, 1923) and Sinum affinis (Eichwald, 1830). A lectotype of Sinum affinis is designated (ZISP 1/62208). Detailed descriptions of the protoconch and teleoconch morphology of the taxa involved, including SEM images, are presented.

The genus Diodora Gray, 1821 is widely represented in the Middle Miocene of the Central Paratethys with specimens usually attributed to D. graeca (Linnaeus, 1758) or D. italica (Defrance, 1820), well-known recent species of the Atlantic / Mediterranean Basin. In samples from the Upper Badenian of Western Ukraine we found two clusters of Diodora specimens, showing a similarity with these species, but a review of shell diagnostic characters using a statistical approach has revealed their clear conchological separateness. The first species from Varovtsi and Horodok is attributed herein to D. nodosa (Eichwald, 1830), whereas the second species from Maksymivka is described as a new species, D. stalennuyi sp. nov. We consider that these molluscs inhabited the Polish-Ukrainian marginal part of the Late Badenian Basin. Detailed descriptions of the protoconch and teleoconch morphology of the taxa involved, including SEM images, are presented.

A new Miocene deep-sea chiton and early evidence for Teredinidae-sustained wood-fall communities

This paper focuses on five species of Polyplacophora (Mollusca) collected from Lavanono, southern Madagascar. Ischnochiton sirenkoi is described as a new species and is compared with the two Ischnochiton species known from Madagascar, I. yerburyi (E.A. Smith, 1891) and I. sansibarensis Thiele, 1909, and with all known Indian Ocean Ischnochiton species. Findings for the other species here discussed provide a significant extension of previously known geographical range. Chaetopleura chelazziana Ferreira, 1983 is reported for the first time in the chiton fauna of Madagascar. The taxonomic status of Callistochiton ashbyi (Barnard, 1963), previously considered a synonym of C. crosslandi Sykes, 1907, is discussed. This taxon, which was described from a unique intermediate valve from South Africa, is re-evaluated and recognized as a valid species, differing from C. crosslandi in several significant characters. We also present an unusual feature detected in almost all the specimens of Cryptoplax dupuisi Ashby, 1931, which are characterized by the absence of dorsal girdle spicules on the first four valves, a feature never reported in other chiton species. Type material of Callistochiton madagassicus Thiele, 1909, Chiton ashbyi (Barnard, 1963) is figured.