Ongoing research

The adaptation of the tetrapods to a life on land was a great step in vertebrate evolution. Several fish groups have attempted to colonise the terrestrial environment (e.g. mudskippers among ray-finned fish; lungfish among lobe-finned fish) but only tetrapods were able to initiate a large-scale terrestrial radiation. This event, which occurred a bit less than 400 million years ago, has been a focus of interest for more than a century. Based on novel, non-destructive synchrotron-based techniques, we have imaged the detailed bone microstructure of extant and extinct taxa in three dimensions and aim to address the following questions:

• When did appendage elements acquire long bone features?
• How could limb bones adapt to terrestrial conditions?
• What can mineralised tissues tell us about the life history of early tetrapods?

When did appendage elements acquire long bone features?

A typical mammal long bone consists of a shaft terminated by articular condyles. Long-bone features were progressively acquired during the evolution of tetrapods. We want to determine this sequence through 3D imaging and modelling of fin and limb bones (from fish members of the tetrapod stem group and crown tetrapods). We want to study the time of appearance and original function of long-bone components and associated soft tissues. In collaboration with the European Synchrotron Radiation Facility (France), we have developed 3D virtual histology based on propagation phase-contrast synchrotron microtomography to investigate vertebrate bone histology in three dimensions. We are now characterising specific microanatomical and microstructural elements in three dimensions to obtain a comparative database in order to infer the palaeophysiology and palaeobiology of extinct taxa.

Selected publications:

Leyhr, Sanchez, Dollman, Tafforeau and Haitina. 2023. Enhanced contrast synchrotron X-ray microtomography for describing skeleton-associated soft tissue defects in zebrafish mutants. Frontiers in Endocrinology 14, 450.
DOI: https://doi.org/10.3389/fendo.2023.1108916

Estefa, Tafforeau, Clement, Klembara, Niedźwiedzki, Berruyer and Sanchez. 2021. New light shed on the early evolution of limb-bone growth plate and bone marrow. Elife 10, e51581.
DOI: https://doi.org/10.7554/eLife.51581

Sanchez , Tafforeau & Ahlberg. 2014. The humerus of Eusthenopteron: a puzzling organization presaging the establishment of tetrapod limb bone marrow. Proceedings of the Royal Society B 281-1782, 20140299.
DOI: https://doi.org/10.1098/rspb.2014.0299

How could limb bones adapt to terrestrial conditions?

We want to understand the adaptation of limb bones to terrestrial conditions. Because the microanatomy of early-tetrapod limb bones significantly differs from that of extant tetrapods, we focus on testing the resistance of early-tetrapod microanatomy to terrestrial loading stresses using 3D modelling and Finite Element Analysis (FEA).

We also aim to reconstruct the muscular architecture of early tetrapods through the development of new tomographic techniques in collaboration imaging experts and the European Synchrotron Radiation Facility (France).

Selected publications:

Clarac, Cornille, Bijl, Tafforeau & Sanchez. 2023. Early evolution of trabecular-bone resistance to terrestrial constraints in a fossil lobe-finned fish. International Congress of Vertebrate Morphology, Cairns, Australia.
Abstract volume hosted by the Anatomical Record:
https://anatomypubs.onlinelibrary.wiley.com/pb-assets/hub-assets/anatomypubs/rr-files/ICVM%202023%20Abstracts%20updated_8_14-1693344432.pdf

Mürer, Sanchez, Alvarez-Murga, Di Michiel, Pfeiffer, Bech, Breiby. 2018. 3D Maps of Mineral Composition and Hydroxyapatite Orientation in Fossil Bone Samples Obtained by X-ray Diffraction Computed Tomography. Scientific reports 8, 10052.
DOI: https://doi.org/10.1038/s41598-018-28269-1

Sanchez, Dupret, Tafforeau, Trinajstic, Ryll, Gouttenoire, Wretman, Zylberberg, Peyrin & Ahlberg. 2013. 3D microstructural architecture of muscle attachments in extant and fossil vertebrates revealed by synchrotron microtomography. PloS One 8-2, e56992.
DOI: https://doi.org/10.1371/journal.pone.0056992

What can mineralised tissues tell us about the life history of early tetrapods?

Given that the transition from water to land entailed a major ecological shift, ultimately affecting every aspect of the animal's life, it seems very likely that it also involved significant changes in life history and reproductive strategy. We aim to test this hypothesis using skeletochronology, i.e. quantifying the growth lines in long bones. Preliminary results have demonstrated a relatively slow bone skeletal development in stem tetrapods, a great development plasticity in the non-amniotic tetrapods (temnospondyls) to survive harsh environmental conditions during the Permian and Triassic (300-250 million years ago), and an extended and transitional shift towards a faster growth strategy in amniotes.

Selected publications:

Estefa, Klembara, Tafforeau & Sanchez. 2020. Limb-bone development of seymouriamorphs: implications for the evolution of growth strategy in stem amniotes. Frontiers in Earth Science 8, 97.
DOI: https://doi.org/10.3389/feart.2020.00097

Sanchez, Tafforeau, Clack & Ahlberg. 2016. Life history of the stem tetrapod Acanthostega revealed by synchrotron microtomography. Nature 537, 408-411.
DOI: https://doi.org/10.1038/nature19354

Sanchez & Schoch. 2013. Bone histology reveals a high environmental and metabolic plasticity as a successful evolutionary strategy in a long-lived homeostatic Triassic temnospondyl. Evolutionary Biology 40-4, 627-647.
DOI: https://doi.org/10.1007/s11692-013-9238-3

Sanchez, Steyer, Schoch & de Ricqlès. 2010. Palaeoecological and palaeoenvironmental influences revealed by long-bone palaeohistology: the example of the Permian branchiosaurid Apateon. In M. Vecoli, G. Clement and B. Meyer Berthaud, (eds.). The terrestrialization process: modelling complex interactions at the biosphere-geosphere Interface. The Geological Society, London 339-1, 139-149.
DOI: https://doi.org/10.1144/SP339.12