Search results for "Phylloceratina"
showing 2 items of 2 documents
Existe-t-il une crise au passage Lias-Dogger chez les ammonites? Approche morphometrique par quantification de la disparite morphologique
2001
Abstract Morphological changes observed in ammonites at the Lias-Dogger (Toarcian-Aalenian) boundary are analyzed here. The study covers all known ammonites worldwide over some 2 m.y. (the last two biozones of the Toarcian: Pseudoradiosa and Aalensis and the first biozone of the Aalenian: Opalinum). Ammonite taxonomy at this boundary is still open to question, the main disagreements being over groupings at family or super-family level. The evolutionary schema developed by Tintant and Mouterde [1981] shows two main sets of Ammonitina for the time: (1) the dominant Hammatocerataceae (Graphoceratidae+Hammatoceratidae) and (2) the final representatives of the Hildocerataceae. Two conservative a…
An unusual conchorhynch from the upper Maastrichtian of the southeast Netherlands and the distinction between nautiloid and ammonoid conchorhynchs (M…
2022
Abstract A single, atypical conchorhynch (calcitic tip of a cephalopod lower jaw), recovered from the uppermost Meerssen Member (Maastricht Formation, upper Maastrichtian) at the former ENCI-HeidelbergCement Group quarry, south of Maastricht, is described as a new parataxon, Conchorhynchus illustris sp. nov. The specimen can be differentiated from all previous conchorhynch records on account of its large size, elongated shape and, in particular, of the structure of its apical part which is smooth and forwardly elongated. During the Late Cretaceous, conchorhynchs formed part of the jaw apparatus of nautilids and of two ammonoid suborders, Phylloceratina and Lytoceratina. Since conchorhynchs …