Annales de Paleontologie最新文献

We report on a significant fossil collection of five isopod crustaceans that belong to five families from three suborders. These fossils were discovered in Le Mans (western part of Paris Basin, France) during the second half of the nineteenth century by the French paleontologist Edouard Guéranger. The historical quarry has been studied a few years before by the French paleontologist Alcide d’Orbigny and used as part of his Cenomanian stratotype (Leach, 1814). The collection consists of two species in the Cymothooidea Dana, 1852 (Cirolanidae Dana, 1852; Lantoceramiidae fam. nov.), two Valvifera G. O. Sars, 1883 (Chaetiliidae Dana, 1853; Idoteidae Samouelle, 1819) and one Asellota Latreille, 1802 (Stenetriidae Hansen, 1905), which were previously unknown from Upper Cretaceous strata as old as the Cenomanian age (roughly 93–99 ma). Although phylogenetic dating based on extant taxa has assigned Permian to Triassic age of origin for the Asellota, the Stenetriidae Hansen, 1905 specimen is the first fossil record for this family. Another asellotan, Fornicaris calligarisi Wilson and Selden, 2016, is known from the Triassic (Norian) dating from approximately 210–215 ma. The valviferans were unknown from Mesozoic strata, previously being found in the Oligocene of Romania and the Fur Formation, Upper Paleocene/Lowermost Eocene of Denmark (Polz, 2007). This diverse assemblage of fossils with taxa assignable to extant families and one new family provides evidence for the presence of a substantially modern isopod fauna as early as the Cenomanian.

Ramageoptera platycephala gen. et sp. nov., a new protopristocerine wasp, is described and figured from a female individual preserved in mid-Cretaceous amber from Tanai, northern Myanmar. Ramageoptera platycephala gen. et sp. nov. shows most of the known characters used to circumscribe the extinct subfamily Protopristocerinae, and highlights the putative status of stem-Pristocerinae that may occupy the Protopristocerinae. Ramageoptera platycephala gen. et sp. nov. is unique among the Protopristocerinae, at least, for possessing a flat and square shaped head; eyes glabrous and small; mandibles with four conspicuous sharp teeth; antenna with short scape; forewing with Rs + M vein absent; vein M straight; cell 2R1 distally opened; cell 1Cu closed, sub-equal to R cell; cell 2Cu open.

Sedimentologic and palaeontological investigation of the Upper Pliocene Slama Formation in the Lower Chelif Basin (NW Algeria) led us to collect important bivalve assemblages for taxonomic and taphonomic purposes. A rather comprehensive inventory list of Upper Pliocene bivalves from northwestern Algeria is now available and consists of 30 species, 17 of which are extinct ones. Four principal taphonomic attributes were analysed: bioerosion, encrustation, fragmentation, and abrasion. Physical and biogenic sedimentary structures are used for palaeoenvironmental interpretations. The taphonomic, sedimentologic and ichnological characteristics of most of the deposits suggests they originated from discontinuous processes of winnowing and bypassing of sediments, probably due to the action of storms in shallow waters, mainly in the shoreface depositional environment. The bivalve assemblage is dominated by disarticulated valves and displays significant taphonomic alteration in the shells. Sclerobionts traces in shells particulary affect the oyster shells. Bioerosion traces are predominately those of clionid sponges (Entobia isp.), polychaetes (Maeandropolydora isp. and Caulostrepsis isp.), bivalves (Gastrochaenolites isp.), and of predatory gastropods (Oichnus isp.). Among the sclerobionts, the identified encrusters were juvenile oyster recruits, barnacles, polychaetes (serpulid tubeworms), bryozoans (Microporella sp. and Acanthodesia sp.), and vermetid gastropods (Petaloconchus intortus).

The micropaleontological study of the Upper Miocene diatomites of the Dahra massif at Ouillis and Sidi Lakhdar sections (Lower Chelif Basin, Algeria), allowed for the first time in Algeria, the identification of 36 species and 22 genera of radiolarians dominated by families Actinommidae, Spongodiscidae and Theoperidae. The qualitative and quantitative analyses of the assemblages show significant specific and generic diversification in the first members. Towards the top of the sections, the progressive decrease in diversity and finally, the disappearance of siliceous microfauna are linked to a reoxygenation of the environment. Respect to the biostratigraphy, the radiolarian assemblage identified confirms a Messinian age (Biozone Stichocorys peregrina).

In the order of Holasteroida, the fossil record highlights a contradiction between the genus Pseudholaster that appears in the Aptian, whose plastron is prostostern close to the Jurassic ancestors and the genus Holaster, which appears in the Valanginian, whose meridostern plastron appears more derived. This inconsistency can be explained by the ignorance of the plastronal architecture on the part of the early authors. A review of the species of Pseudholaster from the Cretaceous period of France was therefore carried out. The objective was to statistically determine the discriminating morphological characters, and to study the modifications of the architecture of the interambulacrum 5 of the French species belonging to this genus, as well as to the species included in the genus Holaster incorrectly by earlier authors. This review of the species of the genus Pseudholaster begins with a study of the ontogeny of the species Holaster intermedius Münster in Goldfuss, 1826–1833, first representative of the genus Pseudholaster, which appears in the Hauterivian in the Parisian and Rhodano-vocontian basins. The modifications during growth concern the overall shape, but also the plastron architecture: the number of plastron plates increases while the number of plates located between the peristome and the periproct remains fixed. The plastron of this species is protosternal and not meridosternal as Lambert pointed out. The labrum is cupuliform in contact with the second sternal 5a2 by a narrow digitation. However, this arrangement differs from that observed on a protosternal breastplate. This apomorphism of the plastron plate pattern, called “labrotaxienne”, is found in all the Pseudholaster studied, and the study of the architecture of the interambulacrum 5 also reveals a gradual decrease in the number of preanal plates between the oldest (Hauterivian) and the younger (Cenomanian-Lower Turonian) species studied. Most of the French species have been revised, with some synonyms. A new species, P. neraudeaui, is the last known Pseudholaster dated from the upper Cenomanian and lower Turonian of southwestern France. Our study illustrates the evolution of the genus Pseudholaster between the Hauterivian and the early Turonian in France. The interest of the study is to show that the appearance of the genus Pseudholaster is older than that of the genus Holaster. Pseuholaster intermedius, of Hauterivian age, possesses a derived protostern plastron called here “labrotaxien” and not meridostern as defined historically by Lambert, and to reveal that the number of preanals decreases over geological time. This data is essential for future phylogenetic studies. On a palaeobiogeographical level, the study reveals the expansion of the genus Pseudholaster during early Cretaceous in western Europe, with diversification during t