Upper Frasnian Tornoceratidae (Ammonoidea) from the Sand Formation (Bergisch Gladbach-Paffrath Syncline, Rhenish Massif)

Excavations in the Sand district of Bergisch Gladbach (Rhenish Massif, Germany) yielded a rich ammonoid fauna of the upper Frasnian “Archoceras” varicosum Zone (Upper Devonian I-K, interval between the two Kellwasser levels). The previously unknown assemblages include six tornoceratid genera with 20 species, including seven new species (Aulatornoceras steinhauseni sp. nov., Aul. frenklerae sp. nov., Aul. ventrosulcatum sp. nov., Crassotornoceras nudum sp. nov., Cr. hetzeneggeri sp. nov., Retrotornoceras juxi sp. nov., Tornoceras aequilobum sp. nov.) and taxa described in open nomenclature. There are five associated gephuroceratid genera with nine species. The unexpectedly high genus- and species-level diversity at Sand, supported by statistical indices, is unprecedented compared to other contemporaneous ammonoid faunas. It highlights the currently fragmentary knowledge of top-Frasnian ammonoid faunas on a global scale. Phoenixites frechi, the dominant tornoceratid of hypoxic and organic-rich Kellwasser facies of Europe and North Africa, is completely missing at Sand. The local assemblage structure is analyzed statistically and interpreted in terms of palaeoecology. The occurrence of a new type of “Housean Pits”, probably caused by parasitism, is found in nine species of five genera, mostly in tornoceratids. The Sand fauna indicates that the species origination rate in tornoceratids remained high after the Lower Kellwasser Event.

Foraminiferal Biochronology of the Triassic Hoang Mai Formation, Central Vietnam

Foraminiferal biostratigraphy was investigated for the first time in the Triassic Hoang Mai Formation distributed in the southeastern part of the Sam Nua Basin which was developed along the northeastern margin of the Indochina Block during the Permian–Triassic. The formation consists entirely of carbonates and is embedded within the underlying volcano-sedimentary Dong Trau Formation and overlying fine-siliciclastic Quy Lang Formation. We examined an approximately 300 m-long core section drilled in the northeastern part of Nghe An province of north Central Vietnam. Based upon the stratigraphic distributions of 24 foraminiferal taxa, including Citaella dinarica, Citaella? deformata, Endotriada tyrrhenica, Endotriadella wirzi, Endotriadella pentacamerata, Pilamminella grandis, Pilammina cf. densa, and Triadodiscus cf. praecursor, we assigned a Pelsonian age for the main part of the Hoang Mai Formation, with its lower/basal part of the core section probably extending down into the Bithynian. Thus, the Hoang Mai Formation is referred to the middle Anisian (early Middle Triassic). We also attempted taxonomic reexamination of foraminifera reported previously from the formation and confirmed the probable occurrence of Aulotortus eotriasicus. This and other taxonomic revision executed on formerly reported foraminifera resulted in further strengthening a middle Anisian appraisal for this formation. In ascending order, the three Middle Triassic lithostratigraphic units distributed in the Sam Nua Basin are the Dong Trau, Hoang Mai, and Quy Lang formations; they have been considered to overlie each other with simple superposition. Elsewhere in the Sam Nua Basin in north Central Vietnam, however, the Balatonites ammonoid fauna, which is considered to be coeval with the present foraminiferal fauna from the Hoang Mai Formation, is known in the uppermost part of the “underlying” Dong Trau Formation and the lowermost part of the “overlying” Quy Lang Formation. This strongly implies heteropic facies development of these three formations in the Sam Nua Basin during Middle Triassic time.

A new Griesbachian–Dienerian (Induan, Early Triassic) ammonoid fauna from Gujiao, South China

Bed-by-bed sampling of the lower portion of the Daye Formation at Gujiao, Guizhou Province, South China, yielded new Griesbachian–Dienerian (Induan, Early Triassic) ammonoid faunas showing a new regional Induan ammonoid succession. This biostratigraphic scheme includes in chronological order the late GriesbachianOphiceras mediumandJieshaniceras guizhouensebeds, and the middle DienerianAmbites radiatusbed. The latter is recognized for the first time as a separate biozone in South China. Eight genera and 13 species are identified, including one new species,Mullericeras gujiaoensen. sp. The new data show that a relatively high level of ammonoid taxonomic richness occurred rather rapidly after the Permian/Triassic mass extinction in the late Griesbachian, echoing similar observations in other basins, such as in the Northern Indian Margin.UUID:http://zoobank.org/a24a3387-f3dd-4da4-a134-84372352a63d