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Regional differences in vertebral shape along the axial skeleton in caecilians (Amphibia: Gymnophiona)
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Abstract Caecilians are elongate, limbless and annulated amphibians that, as far as is known, all have an at least partly fossorial lifestyle. It has been suggested that elongate limbless vertebrates show little morphological differentiation throughout the postcranial skeleton. However, relatively few studies have explored the axial skeleton in limbless tetrapods. In this study, we used ?CT data and three-dimensional geometric morphometrics to explore regional differences in vertebral shape across a broad range of caecilian species. Our results highlight substantial differences in vertebral shape along the axial skeleton, with anterior vertebrae being short and bulky, whereas posterior vertebrae are more elongated. This study shows that despite being limbless, elongate tetrapods such as caecilians still show regional heterogeneity in the shape of individual vertebrae along the vertebral column. Further studies are needed, however, to understand the possible causes and functional consequences of the observed variation in vertebral shape in caecilians.
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RBINS Staff Publications 2022
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The relationship between head shape, head musculature and bite force in caecilians (Amphibia: Gymnophiona)
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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
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Description of a new species of the genus Anomophysis Quentin & Villiers, 1981 from Wetar Island (Contribution to the knowledge of Indonesian Prioninae-2) (Coleoptera, Cerambycidae, Prioninae)
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RBINS Staff Publications 2024
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4th International Meeting of Anthracology, Brussels, 8-13 September 2008. Charcoal and microcharcoal: Continental and Marine Records. Programme and Abstracts
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Is vertebral shape variability in caecilians (Amphibia: Gymnophiona) constrained by forces experienced during burrowing?
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Caecilians are predominantly burrowing, elongate, limbless amphibians that have been relatively poorly studied. Although it has been suggested that the sturdy and compact skulls of caecilians are an adaptation to their head-first burrowing habits, no clear relationship between skull shape and burrowing performance appears to exist. However, the external forces encountered during burrowing are transmitted by the skull to the vertebral column, and, as such, may impact vertebral shape. Additionally, the muscles that generate the burrowing forces attach onto the vertebral column and consequently may impact vertebral shape that way as well. Here, we explored the relationships between vertebral shape and maximal in vivo push forces in 13 species of caecilian amphibians. Our results show that the shape of the two most anterior vertebrae, as well as the shape of the vertebrae at 90% of the total body length, is not correlated with peak push forces. Conversely, the shape of the third vertebrae, and the vertebrae at 20% and 60% of the total body length, does show a relationship to push forces measured in vivo. Whether these relationships are indirect (external forces constraining shape variation) or direct (muscle forces constraining shape variation) remains unclear and will require quantitative studies of the axial musculature. Importantly, our data suggest that mid-body vertebrae may potentially be used as proxies to infer burrowing capacity in fossil representatives.
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RBINS Staff Publications 2022
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Phylogenomics of Psammodynastes and Buhoma (Elapoidea: Serpentes), with the description of a new Asian snake family
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Asian mock vipers of the genus Psammodynastes and African forest snakes of the genus Buhoma are two genera belonging to the snake superfamily Elapoidea. The phylogenetic placements of Psammodynastes and Buhoma within Elapoidea has been extremely unstable which has resulted in their uncertain and debated taxonomy. We used ultraconserved elements and traditional nuclear and mitochondrial markers to infer the phylogenetic relationships of these two genera with other elapoids. Psammodynastes, for which a reference genome has been sequenced, were found, with strong branch support, to be a relatively early diverging split within Elapoidea that is sister to a clade consisting of Elapidae, Micrelapidae and Lamprophiidae. Hence, we allocate Psammodynastes to its own family, Psammodynastidae new family. However, the phylogenetic position of Buhoma could not be resolved with a high degree of confidence. Attempts to identify the possible sources of conflict in the rapid radiation of elapoid snakes suggest that both hybridisation/introgression during the rapid diversification, including possible ghost introgression, as well as incomplete lineage sorting likely have had a confounding role. The usual practice of combining mitochondrial loci with nuclear genomic data appears to mislead phylogeny reconstructions in rapid radiation scenarios, especially in the absence of genome scale data.
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RBINS Staff Publications 2024
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Exploitation of squirrel fur in the 11th century in Huy, Belgium
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RBINS Staff Publications 2025
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A Paleocene occurrence of cornelian cherries Cornus subg. Cornus in the land-mammal site of Berru (Paris Basin, France)
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Cornus subgenus Cornus, also called cornelian cherries, is a relatively ancient clade of dogwoods with a complex biogeographic history. Their fossil record attests to a distribution in North America during the Late Cretaceous and Paleocene, whereas the earliest fossil record in Europe is dated as early as the Eocene. Here, we describe a new occurrence of cornelian cherries based on permineralized endocarps from the late Paleocene (ca. 58 Ma) land-mammal locality of Berru, in Northwest France. The 48 studied specimens possess characteristic cornelian cherry endocarp morphology with locules associated with a dorsal germination valve, no central vascularization, and the presence of numerous secretory cavities in the endocarp wall. In addition, the presence of (three)-four locules and a large apical depression strongly suggest affinities with the early Eocene species Cornus multilocularis from the London Clay Formation. This new occurrence expands the stratigraphic range of the species by approximately four to six million years and is the first unequivocal evidence of cornelian cherries in Europe during the Paleocene. The biogeographical history of cornelian cherries remains complex to explore because of its ancient distribution in the Cretaceous and a geographically and stratigraphically patchy Cenozoic record.
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RBINS Staff Publications 2025
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Bioerosional marks in the shells of two extinct sea turtle taxa from the Eocene of Belgium
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Bioerosional marks are frequently recognized as indicators of the dynamic interactions between the organisms and their surrounding environments. In the fossil record, these structures are frequently manifest in the skeletal remains of vertebrates, being commonly associated to predation activity, scavenging, or post-mortem degradation processes. In the case of the turtles, their shells offer a distinctive substrate, exposed for the development of bioerosional processes throughout the organism life, unlike other vertebrate osseous structures. These bioerosions can indicate the type of habitat in which the turtles live, their behavioral patterns, and even their state of health. Sea turtles, as other marine vertebrates, have been extensively studied in the realms of the biology, evolution, and conservation. However, relatively scarce information is available regarding the pathologies and infectious diseases affecting their shells, especially when extinct taxa are analyzed. The aim of this study is to analyze the diverse types of bioerosional marks on the shells of two sea turtle individuals, attributable to taxa, from the Lutetian (middle Eocene) of Belgium. One of them corresponds to the shell of the holotype of Eochelone brabantica (IRSNB R 0001). Its carapace exhibits multiple erosive anomalies on several costal plates. The second specimen is a carapace of Puppigerus camperi (IRSNB R 0004). It displays different typologies of shell deviations, also of erosive character. The analyses of these specimens have been performed through both the detailed macroscopic examination and the study of the cross-sectional images provided by CT scanning in the case of Eochelone brabantica, and a 3D model obtained through a surface scanner for Puppigerus camperi. As a result, insights into the shell modifications of these two turtle individuals induced by various external agents have been provided, enhancing our understanding of the physical stressors affecting these organisms in ancient marine environments and the organisms responsible for these changes.
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RBINS Staff Publications 2025
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First detailed study of the Belgian Eocene sea turtle ‘Oligochelone rupeliensis’
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In 1909, the famous palaeontologist Louis Dollo announced, in a paper about the Belgian fossil vertebrates, a new Oligocene (Rupelian) genus and species of sea turtle, ‘Oligochelone rupeliensis’. He indicated that it was established for a specimen that preserved the complete carapace and several appendicular bones, being characterized as “a typical marine turtle”. No further information, but neither photographs or drawings, were provided by him. He planned to publish the study of this species in the future, but this did not happen. Only a schematic drawing of the plastron of that specimen, as well as a photograph of a tibia attributed to this taxon without justification, were presented, by another author, seventy years later. The first-hand study of the specimen considered by Dollo allows us to observe that it does not preserve any tibia, so that attribution cannot be supported. Therefore, except for that imprecise drawing of the plastron published more than four decades ago, no additional information was available so far. In fact, ‘Oligochelone rupeliensis’ was recognized as a nomen nudum. After a preliminary analysis of the specimen considered by Dollo, one of us (APG) and other collaborators recently indicated, without justification, that, although ‘Oligochelone rupeliensis’ could be closely related to the Eochelone representatives, it differs from all defined members of Cheloniidae. Therefore, we point out that a detailed anatomical study of this form, as well as its comparison with other species, would be necessary to propose, for the first time, a diagnosis, if its specific validity can be confirmed. Taking this into account, that partial skeleton has been analyzed in detail by us. To improve the comparative framework, both the type material and additional individuals from all Eocene and Oligocene cheloniid taxa recognized for the Belgian record have also been analyzed first-hand. The preliminary results are presented here.
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RBINS Staff Publications 2025