Search results for "Scaphites"
showing 3 items of 3 documents
Distribution of late Maastrichtian pachydiscid and scaphitid ammonites in the Maastricht and Kunrade formations of the southeast Netherlands
2018
Abstract The pachydiscid Pachydiscus ( Pachydiscus ) gollevillensis (d'Orbigny, 1850), long held to be confined to the ‘Kunrade Limestone’ (nowadays Kunrade Formation) in the eastern part of southern Limburg (Kunrade–Benzenrade area, the Netherlands), is now recorded from the basal Nekum Member (Maastricht Formation) at the ENCI-HeidelbergCement Group quarry, Sint-Pietersberg (Maastricht). Here we review the stratigraphic distribution of pachydiscid and scaphitid ammonites in outcrops west of the River Maas (Maastricht Formation) and in the Kunrade–Benzenrade area (Kunrade Formation). The latter unit has been correlated with part of the Lanaye Member (Gulpen Formation) up to the basal Emael…
First record of the enigmatic coleoid genus Longibelus from Sakhalin (Far East Russia): a contribution to our understanding of Cretaceous coleoid hab…
2021
AbstractA newly collected specimen of the enigmatic coleoid genus Longibelus is recorded from lower Turonian strata along the River Shadrinka in Sakhalin (Russian Far East). To date, this is the first record of Late Cretaceous coleoid cephalopods from the island and, in fact, from the entire Pacific coast of the Russian Federation. Lithological characteristics, coupled with published geochemical analyses (δ13C and Corg content), suggest the habitat of this coleoid taxon to have been the middle to outer (i.e. distal) shelf. Its provenance from the stratigraphical level that is known as the Scaphites Event, characterised by a mass occurrence of Scaphites and Yesoites, may be indicative of occ…
The complex nature of progenetic species — examples from Mesozoic ammonites
1991
Several examples of progenetic species among Mesozoic ammonites are investigated. The ammonites are Middle Jurassic kosmoceratids, Upper Jurassic oppeliids, and Upper Cretaceous scaphites. As assessed through outgroup comparison, the progenetic species in each of these examples is characterized by small size at maturity and the presence of morphological features typical of those of the juveniles of more primitive species. However, in none of these examples is the progenetic species a duplicate form of the juvenile stage of more primitive species. There are at least three kinds of features of progenetic species that differ from those of the juveniles of more primitive species: (1) symplesiom…