Platychelone emarginata Dollo, 1909 is a large turtle from the Late Cretaceous (Maastrichtian) chalk sediments of Limburg, Belgium. Hitherto, only the name was given to this turtle without describing details or providing figures. A single well articulated carapace (IRScNB. Reg. 1681), lacking nuchal, peripherals, and pygal plates, is preserved. The distance from the first costal to the distal end of the eighth costal is 180 cm, indicating that the original carapace was about 210 cm long. Its gigantic size, flattened shell, reduction of distal half of costals, and loss of scute sulcus, indicate that Platychelone is a member of true marine turtles (superfamily Chelonioidea). Neurals are rectangular shape and inclination of the first thoracic vertebra is almost vertical, suggesting this turtle belongs to either Protostegidae or Dermochelyidae. Seventh and eighth costals are medially meeting due to the loss of neurals; this condition is shared with the genus Mesodermochelys from the Late Cretaceous (Santonian to Maastrichtian) of Japan. Thus, it seems most probable that Platychelone is a closest relative of Mesodermochelys among basal dermochelyids. Platychelone has presumed autoapomorphic characters such as very thickened distal ends of thoracic ribs and irregular sculptures on carapace, not seen in any other chelonioids. This genus is only known by the holotype, whereas Allopleuron hoffmanni, a very common cheloniid marine turtle from in the Maastrichtian deposits of Belgium and Netherland, is known from some hundred specimens. So far, there is no ancestral or related taxon of Platychelone from the Campanian deposits of Belgium. The occurrence of Platychelone is very rare but evokes a high taxonomic diversity of gigantic chelonioids in the Cretaceous Tethys.
Located in
Library
/
RBINS Staff Publications 2017
Small mammal faunas from the Pleistocene of Belgium are not well-known. Some have been studied from the second half of the Late Pleistocene and the Early Holocene. However, only a few sites from the first half of the Late Pleistocene (Marine Isotope Stage 3, MIS 3, ca. 60-30 ka) have yielded small mammal assemblages. Among them is the Marie-Jeanne Cave that is situated in the southeast of Belgium, in the Ardennes region. It is formed in the Early Carboniferous limestone deposits above the Meuse River, near the town of Hastière-Lavaux. The excavated deposits evidenced ten different layers but only the layers 6 to 2 yieldeda large collection of faunal remains. Recent dating of the stratigraphic sequence of the Marie-Jeanne Cave shows that these layers have a chronological range pertaining to MIS 3 (about 50-40 ka BP). During the first field campaign in 1943, about 40 m3 of sedimentswereextracted recovering a large collection of disarticulated bone fragments and several plant, mollusc and archaeological remains housed at the RBINS. A first study of this material underlined the presence of 29 taxa of insectivores, bats and rodents. The recent revision of the material revealed 9897 identified specimens, corresponding to a minimum of 4980 individuals. This permitted us to add to the previous list two vole species, the steppe lemming Lagurus lagurus and the European pine vole Microtus (Terricola) subterraneus. We also undertook new paleoenvironmental and paleoclimatic reconstructions based on alternative methods from those previously used for the MIS 3 sequence of the Marie-Jeanne Cave. Our results indicate that MIS 3 is characterized by dynamic alternations of forest expansion with semiarid area expansion in accordance with the warming and cooling, respectively, of the sea-surface temperatures. It was in this context of rapid fluctuations that the terrestrial sequence of the Marie-Jeanne Cave in north-western Europe was formed. The fossiliferous layers underwent cold and dry environmental and climatic conditions. This is indicated by lower temperatures and slightly higher precipitation than today, together with an environment dominated by open woodland formations and open dry meadows. Our results are consistent with the available chronological, large-mammal, herpetofaunal, and mollusc datasets for this lower part of the sequence. They are also consistent with regional loess studies in Belgium and with previous work performed on small mammals from MIS 3 in Belgium and elsewhere in Europe. Grant Information: Generalitat de Catalunya projects, Synthesis Grants, PhD grant of the Erasmus Mundus Programme - International Doctorate in Quaternary and Prehistory.
Located in
Library
/
RBINS Staff Publications 2017
