Biology subjects

Davesne, D.

Publications and source records attributed to Davesne, D..

3 recordsLinked to original sources

bioRxiv2024

An extraordinary larval-like teleost fish from the Eocene of Bolca

"Pegasus" volans is a highly unusual fossil teleost fish from the celebrated Eocene Bolca Lagerstatte. The fossil, known on the basis of two specimens, has been historically assigned to seamoths (Pegasidae), then to oarfish and relatives (Lampriformes). We describe its enigmatic skeletal anatomy in detail, and provide a new genus name. "Pegasus" volans is an extremely elongate and slender animal, with long anal and dorsal fins and a very well-developed first dorsal-fin ray reminiscent to the vexillum of some modern teleost larvae. Most striking is its extreme ventral projection of the pelvic girdle (basipterygium), associated with an element of the pectoral girdle (a long process of the coracoid) and developed pelvic-fin rays. The strongly reduced abdominal region suggests that "Pegasus" volans had an external gut, once again reminiscent of those of certain larval teleosts. The unique character state combination displayed by "Pegasus" volans make it impossible to assign it to a specific subclade within perch-like spiny-rayed fishes (Percomorpha). Nevertheless, it offers a valuable perspective on the diversity of morphologies and ecological niches occupied by teleost fishes of the early Eocene Bolca fauna.

paleontology↗

bioRxiv2023

Three-dimensional anatomy of the early Eocene {dagger}Whitephippus (Teleostei: Lampriformes) documents parallel conquests of the pelagic environment by multiple teleost lineages

The early Eocene fossil assemblage of the London Clay (Southeastern England) is a key window to the early Paleogene diversification of teleost fishes in the open ocean. Despite their three-dimensional preservation that offers unique insight into skeletal anatomy, the London Clay fossils are still poorly described for the most part. {dagger}Whitephippus tamensis is a fossil teleost from this assemblage, known by several well-preserved specimens. Based on a complete description of the known material, including previously hidden structures (braincase, hyoid and branchial arches) revealed through 3D microtomography, we reinterpret {dagger}Whitephippus as an early member of the teleost group Lampriformes. More specifically, the anatomy of {dagger}Whitephippus indicates that it is likely a member of the so-called pelagic clade including modern opahs and oarfishes. This redescription of {dagger}Whitephippus provides the earliest definitive evidence of lampriforms conquering the pelagic environment, alongside numerous other teleost lineages.

paleontology↗

bioRxiv2019

Three-dimensional characterisation of osteocyte volumes at multiple scales, and its relationship with bone biology and genome evolution in ray-finned fishes

Osteocytes, cells embedded within the bone mineral matrix, inform on key aspects of vertebrate biology. In particular, a relationship between volumes of the osteocytes and bone growth and/or genome size has been proposed for several tetrapod lineages. However, the variation in osteocyte volume across different scales is poorly characterised, and mostly relies on incomplete, two-dimensional information. In this study, we propose to characterise the variation of osteocyte volumes in ray-finned fishes (Actinopterygii), a clade including more than half of modern vertebrate species in which osteocyte biology is poorly known. We use X-ray synchrotron micro computed tomography (SRCT) to achieve a three-dimensional visualisation of osteocytes and direct measurement of their volumes. Our specimen sample is designed to characterise osteocyte variation at three scales: within a bone, between the bones of one individual and between taxa spanning actinopterygian phylogeny. At the intra-bone scale, we find that osteocytes vary noticeably in volume between zones of organised and woven bone (being larger in the latter), and across cyclical bone deposition. This is probably explained by differences in bone deposition rate, with larger osteocytes contained in bone that deposits faster. Osteocyte volumes vary from one bone to another, for unclear reasons. Finally, we find that genome size is the best explanatory variable of osteocyte volume at the inter-specific scale: actinopterygian taxa with larger genomes (polyploid taxa in particular) have larger osteocytes. Our findings corroborate previous two-dimensional observations in tetrapods, and open new perspectives for actinopterygian bone evolution, physiology and palaeogenomics.

zoology↗