Sergio E. Miquel

Ichnology, Sedimentology and Paleontology of Eocene Calcareous Paleosols From a Palustrine Sequence, Argentina

Abstract Integrated analysis of the ichnology, sedimentology, geochemistry, and fossil content of three trace fossil-bearing calcareous paleosols from the early Eocene Gran Salitral Formation is used to reconstruct the detailed paleoenvironmental and paleoecological setting of this insect-dominated ichnofossil association. This continental sequence, located in southwestern La Pampa province (Argentina), is composed of palustrine marls and minor lacustrine mudstones and sandstones arranged in shallowing-upward cycles. The ichnologic association is the first comprehensively described from a palustrine sequence and could be used for future comparisons with other similar assemblages. The ichnofauna is dominated by bee cells, Celliforma germanica, C. roselli, and Rosellichnus isp.; Teisseirei barattinia, an insect trace fossil that is redescribed and recorded for the first time outside its type locality; Taenidium barretti; and Skolithos linearis. The ichnologic association also includes ovoid structures, ornamented burrow fillings, and plant trace fossils (rootlets, rhizoliths, and a tree / shrub stump). Abundant freshwater (Pomacea sp.) and terrestrial gastropods (Plagiodontes spp., Bostryx sp., and Bulimulus sp.) are used to characterize the paleoenvironmental setting. The weakly developed paleosols are interpreted as Inceptisols, developed in a low-gradient lake margin periodically exposed to pedogenesis with low (probably saline) vegetation and sparse shrubs. They developed under a semi-arid and warm climate (mean annual temperature higher than 20°C). Short saline / alkaline conditions were prevalent during lake lowstands, accompanied by incipient karst development. The association of trace fossils is attributed provisionally to the Coprinisphaera ichnofacies, although its distinctive features and recurrence in time and space may deserve recognition as a separate ichnofacies.

First Records of Four Exotic Slugs in Argentina

Abstract: This paper reports for the first time the occurrence of four exotic terrestrial slug species in Argentina: Lehmannia valentiana (Férussac, 1823) (Limacidae), Deroceras invadens Reise et al. 2011 (Agriolimacidae), Arion intermedius Normand, 1852 (Arionidae) and Meghimatium pictum (Stolyczka, 1873) (Philomycidae). The study is based on specimens deposited in museums in Argentina. Both the morphologic characteristics and the mitochondrial cytochrome oxidase I gene sequences were used to identify the exotic species. Phylogenetic analyses were also carried out in order to explore the location of their origins. Lehmannia valentiana had the oldest records and has been widely distributed in Argentina. Deroceras invadens and A. intermedius were found to be restricted to the southern portion of the country. Meghimatium pictum was recorded in the northwest and northeast Argentina, and the DNA sequences analyzed from this species were more closely related to specimens from the west of the Strait of Taiwan. A determination of the origin of the other species was impossible because either the sequences analyzed grouped with samples from different geographical origins or only few sequences were available for comparison. In view of the invasive potential of these slug species, the present work provides new and potentially useful DNA sequence data obtained from morphologically-confirmed specimens. Information provided from these analyses should assist in making a rapid identification of these exotic slugs by nonspecialists and governmental authorities who are responsible for managing and controlling the presence of exotic species.

New records of exotic land snails and slugs in Argentina

We announce the presence of two species of exotic terrestrial mollusks new for Argentina: Oxychilus draparnaudi (Oxychilidae) in Buenos Aires province and Opeas (O.) pumilum (Subulinidae) in Tucuman province. New records expand further the distributions of seven other species in Argentina: Paralaoma servilis (Punctidae) and Deroceras (Agriolimax) reticulatum (Limacidae) throughout the country; in northern tropical climates, O. (O.) pumilum and Bradybaena (B.) similaris (Helicidae); in the warm central area, Theba p. pisana (Helicidae) and O. draparnaudi; in Patagonia, Limax (L.) maximus (Limacidae); and Vertigo ovata (Vertiginidae) and Hawaiia minuscula (Pristilomatidae) in northern and central Argentina. The presence of Deroceras laeve and D. agrestis (Limacidae) could not be confirmed. It is not clear if Pupisoma (Ptychopatula) dioscoricola (Vallonidae) is a native or exotic species in Argentina.

A novel late Early Miocene assemblage of terrestrial gastropods from Santa Cruz (Patagonia, Argentina)

Abstract. A remarkable fossil assemblage composed of five gastropod taxa is described from the Early Miocene of Santa Cruz (Patagonia, Argentina) in southernmost South America. The assemblage includes extinct and living genera South America, and on geographic distributions and represent background new information on spatial and across time distributions as well as identification of new taxa. A new taxon, Patagocharopa enigmatica n. gen. n. sp., is tentatively assigned to Charopidae. Gastrocopta patagonica n. sp. (Vertiginidae) represents the oldest record of Gastrocopta in Argentina and the southernmost record for the Americas. Punctum patagonicum n. sp. (Punctidae) represents the first record of Punctum for continental South America, and characterized by a protoconch with traces of axial costulae and a teleoconch with strong radial ribs. Zilchogyra miocenica n. sp. is the first Miocene record of the charopid genus Zilchogyra. Fragments of a possible Scolodonta (Scolodontidae) are recorded. Overall, the assemblage represents an important and useful paleoenvironmental tool. This fauna suggests that a more temperate and humid environment than today—with a more dense vegetation cover—was prevalent at this site during the Early Miocene.