Caecilians are enigmatic limbless amphibians that, with a few exceptions, all have an at least partly burrowing lifestyle. Although it has been suggested that caecilian evolution resulted in sturdy and compact skulls as an adaptation to their head-first burrowing habits, no relationship between skull shape and burrowing performance has been demonstrated to date. However, the unique dual jaw-closing mechanism and the osteological variability of their temporal region suggest a potential relationship between skull shape and feeding mechanics. Here, we explored the relationships between skull shape, head musculature and in vivo bite forces. Although there is a correlation between bite force and external head shape, no relationship between bite force and skull shape could be detected. Whereas our data suggest that muscles are the principal drivers of variation in bite force, the shape of the skull is constrained by factors other than demands for bite force generation. However, a strong covariation between the cranium and mandible exists. Moreover, both cranium and mandible shape covary with jaw muscle architecture. Caecilians show a gradient between species with a long retroarticular process associated with a large and pennate-fibered m. interhyoideus posterior and species with a short process but long and parallel-fibered jaw adductors. Our results demonstrate the complexity of the relationship between form and function of this jaw system. Further studies that focus on factors such as gape distance or jaw velocity will be needed in order to fully understand the evolution of feeding mechanics in caecilians.
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RBINS Staff Publications 2021
A re-description of the little-known holothurian species Holothuria (Lessonothuria) lineata Ludwig, 1875 is given. It is based on the single recovered type specimen and an individual recently collected on Glorioso Islands, near Madagascar. A key to separate three closely related and commonly confused species, i.e., Holothuria (Lessonothuria) pardalis Selenka, 1867, Holothuria (Lessenothuria) verrucosa Selenka, 1867 and Holothuria (Lessonothuria) insignis Ludwig, 1875, is presented.
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RBINS Staff Publications 2019
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.
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RBINS Staff Publications 2017
