Sophie Sanchez

• PhD
• Lecturer at Uppsala University

Malgré leur rareté dans le registre fossile, en particulier pour les vertébrés du Paléozoïque, les restes de tissus mous sont essentiels pour révéler des aspects clés de la paléobiologie et de l'écologie des taxons éteints. Nous présentons ici des occurrences de restes de tissus mous de la peau et des yeux chez des amphibiens du Carbonifère et du P...

Despite a scarce fossil record, particularly for Palaeozoic vertebrates, soft tissue remains are crucial for revealing key aspects of palaeobiology and ecology. We present here unprecedented occurrences of both skin and eye soft tissue remains in both Carboniferous and Permian amphibians from France. This discovery sheds new light on the evolution...

Cartilaginous fishes (chondrichthyans: chimaeras and elasmobranchs -sharks, skates and rays) hold a key phylogenetic position to explore the origin and diversifications of jawed vertebrates. Here, we report and integrate reference genomic, transcriptomic and morphological data in the small-spotted catshark Scyliorhinus canicula to shed light on the...

Ankylosaurs were a group of heavily armored non‐avian dinosaurs (Dinosauria, Ankylosauria), represented by a relatively abundant fossil record from the Cretaceous of North and South America. Their dermal skeleton was characterized by large osteoderms whose development and functional role have been largely investigated. However, interstitial small o...

Cartilaginous fishes (chimeras and elasmobranches -sharks, skates and rays) hold a key phylogenetic position to explore the origin and diversifications of jawed vertebrates. Here, we report reference genomic, transcriptomic and phenotypic data in the small spotted catshark Scyliorhinus canicula , and integrate these data to shed light on the evolut...

Our study shows that the von Mises stress, induced by external load on the humerus of Eusthenopteron, dissipates through the cortex, trabeculae and the muscles of the pectoral appendage involved in elevation and protraction. As Eusthenopteron's microanatomy is similar to that of Devonian tetrapods, we expect them to share the same process of load d...

Fossil amphibians from the Carboniferous–Permian period are diverse and well-studied: within the temnospondyls, the dissorophoids and eryopoids have been studied in depth in terms of anatomy and skeletal ontogeny. However, soft tissue analyses are rare. Here we describe in detail the skeletal and soft tissue anatomy of an exceptionally preserved ea...

Les amphibiens fossiles du Carbonifère-Permien sont divers et bien étudiés : au sein des temnospondyles, les dissorophoïdes et les éryopoïdes ont fait l'objet d'études approfondies en termes d'anatomie et d'ontogenèse du squelette. Cependant, les analyses des tissus mous sont rares. Nous décrivons ici en détail l'anatomie du squelette et des tissus...

Jensen et al. (1) question evidence presented of a chambered heart within placoderms, citing its small size and apparently ventral atrium. However, they fail to note the belly-up orientation of the placoderm within one nodule, and the variability of heart morphology within extant taxa. Thus, we remain confident in our interpretation of the minerali...

Osteostracans are stem-gnathostomes with bony tissues that represent an important link between living jawed and jawless vertebrates, the latter of which lack skeletal hard tissues. In this study, a number of skeletal microremains from a diverse group of osteostracans called thyestiids have been investigated using propagation phase-contrast X-ray sy...

The temnospondyl Onchiodon belongs to the family Eryopidae, which includes among the largest Carboniferous and Permian amphibians with Eryops (~2 to 3 meters long). Onchiodon, recovered in Germany and Czech Republic, was only mentioned in France until now. Here we provide the first description of a larval/early juvenile specimen of Onchiodon from t...

Detailed histological analyses are desirable for zebrafish mutants that are models for human skeletal diseases, but traditional histological techniques are limited to two-dimensional thin sections with orientations highly dependent on careful sample preparation. On the other hand, techniques that provide three-dimensional (3D) datasets including µC...

The origin and early diversification of jawed vertebrates involved major changes to skeletal and soft anatomy. Skeletal transformations can be examined directly by studying fossil stem gnathostomes; however, preservation of soft anatomy is rare. We describe the only known example of a three-dimensionally mineralized heart, thick-walled stomach, and...

The Cretaceous–Palaeogene mass extinction around 66 million years ago was triggered by the Chicxulub asteroid impact on the present-day Yucatán Peninsula1,2. This event caused the highly selective extinction that eliminated about 76% of species3,4, including all non-avian dinosaurs, pterosaurs, ammonites, rudists and most marine reptiles. The timin...

Significance Some lineages of organisms have undergone major evolutionary radiations, while others have not. Establishing why is a central goal of evolutionary research. Whole-genome duplication (WGD) is often proposed as having caused the spectacular evolutionary radiation of teleost fishes. However, due to the absence of genetic data for fossil s...

Teleost fishes comprise one-half of all vertebrate species and possess a duplicated genome. This whole-genome duplication (WGD) occurred on the teleost stem lineage in an ancient common ancestor of all living teleosts and is hypothesized as a trigger of their exceptional evolutionary radiation. Genomic and phylogenetic data indicate that WGD occurr...

The Cretaceous-Paleogene (KPg) mass extinction ~66 million years ago (Ma) was triggered by the Chicxulub impact on the present-day Yucatán Peninsula. This event caused the extinction of circa 76% of species, including all non-avian dinosaurs, and represents one of the most selective extinctions to date. The timing of the impact and its aftermath ha...

Thyestiids are a group of osteostracans (sister‐group to jawed vertebrates) ranging in time from the early Silurian to Middle Devonian. Tremataspis is unique among thyestiids in having a continuous mesodentine and enameloid cover on its dermal elements, and an embedded pore‐canal system divided into lower and upper parts by a perforated septum. The...

The production of blood cells (haematopoiesis) occurs in the limb bones of most tetrapods but is absent in the fin bones of ray-finned fish. When did long bones start producing blood cells? Recent hypotheses suggested that haematopoiesis migrated into long bones prior to the water-to-land transition and protected newly-produced blood cells from har...

The ontogenetic trajectory of a marginal jawbone of Lophosteus superbus (Late Silurian, 422 Million years old), the phylogenetically most basal stem osteichthyan, visualized by synchrotron microtomography, reveals a developmental relationship between teeth and dermal odontodes that is not evident from the adult morphology. The earliest odontodes ar...

Growth plate and articular cartilage constitute a single anatomical entity early in development but later separate into two distinct structures by the secondary ossification center (SOC). The reason for such separation remains unknown. We found that evolutionarily SOC appears in animals conquering the land - amniotes. Analysis of the ossification p...

Growth plate and articular cartilage constitute a single anatomical entity early in development but later separate into two distinct structures by the secondary ossification center (SOC). The reason for such separation remains unknown. We found that evolutionarily SOC appears in animals conquering the land - amniotes. Analysis of the ossification p...

Growth plate and articular cartilage constitute a single anatomical entity early in development, but later separate into two distinct structures by the secondary ossification center (SOC). The reason for such separation remains unknown. We found that evolutionarily SOC appears in animals conquering the land - amniotes. Analysis of ossification patt...

Ontogenetic data obtained by synchrotron microtomography of a marginal jawbone of Lophosteus superbus (Late Silurian, 422 Million years old), the phylogenetically basalmost stem osteichthyan, reveal developmental relationships between teeth and ornament that are not obvious from the adult morphology. The earliest odontodes are two longitudinal foun...

Tetrapod life on land was the result of a lengthy process, the final steps of which resulted in full independence of amniotic tetrapods from the aquatic environment. Developmental strategies, including growth rate and the attainment of sexual maturity, played a major role in this transition. Early amniotes, such as Ophiacodon, tended to reach sexua...

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 mo...

Studies on living turtles have demonstrated that shells are involved in the resistance to hypoxia during apnea via bone acidosis buffering; a process which is complemented with cutaneous respiration, transpharyngeal and cloacal gas exchanges in the soft-shell turtles. Bone acidosis buffering during apnea has also been identified in crocodylian oste...

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 mo...

The growth of long bones occurs in narrow discs of cartilage, called growth plates that provide a continuous supply of chondrocytes subsequently replaced by newly formed bone tissue. These growth plates are sandwiched between the bone shaft and a more distal bone structure called the secondary ossification center (SOC). We have recently shown that...

Hyneria lindae is one of the largest Devonian sarcopterygians. It was found in the Catskill Formation (late Famennian) of Pennsylvania, USA. The current study focuses on the palaeohistology of the humerus of this tristichopterid and supports a low ossification rate and a late ossification onset in the appendicular skeleton. In addition to anatomica...

Whether hydroxyapatite (HA) orientation in fossilised bone samples can be non-destructively retrieved and used to determine the arrangement of the bone matrix and the location of muscle attachments (entheses), is a question of high relevance to palaeontology, as it facilitates a detailed understanding of the (micro-)anatomy of extinct species with...

Archaeopteryx is an iconic fossil taxon with feathered wings from the Late Jurassic of Germany that occupies a crucial position for understanding the early evolution of avian flight. After over 150 years of study, its mosaic anatomy unifying characters of both non-flying dinosaurs and flying birds has remained challenging to interpret in a locomoto...

Fossils of juvenile Mesozoic birds provide insight into the early evolution of avian development, however such fossils are rare. The analysis of the ossification sequence in these early-branching birds has the potential to address important questions about their comparative developmental biology and to help understand their morphological evolution...

There are two types of dermal skeletons in jawed vertebrates: placoderms and osteichthyans carry large bony plates (macromery), whereas chondrichthyans and acanthodians are covered by small scales (micromery). Fin spines are one of the last large dermal structures found on micromeric taxa and offer a potential source of histology and morphology tha...

Thin section (S2368) of a dermal plate of Romundina, deposited at the Natural History Museum of Stockholm. Arrows mark the cell lacunae and arrowheads mark the dentine tubules. Note the different colors of the outer layer and the inner layer, both of which have dentine tubules and cell lacunae. (TIF)

Palaeospondylus gunni Traquair, 1890 is an enigmatic Devonian vertebrate whose taxonomic affinities have been debated since it was first described. Most recently, Palaeospondylus has been identified as a stem-group hagfish (Myxinoidea). However, one character questioning this assignment is the presence of three semicircular canals in the otic region of...

In order to understand the ecological dimension of the fish-tetrapod transition, which occurred within the tetrapod stem group during the Devonian Period (419-359 million years ago), we need life-history data from transitional forms. Only recently have serious attempts begun to utilize limb-bone histology as a source of such data. Here we present h...

Recently, attempts have been made to utilize limb-bone histology as a source of data for understanding the ecological dimension of the fish-tetrapod transition. Here we present histological life history data from a humerus (ANSP 21483) of Hyneria lindae, a fish member of the tetrapod stem group from the Late Devonian Catskill Formation (Pennsylvani...

The numerous cushion-shaped tooth-bearing plates attributed to the stem group osteichthyan Lophosteus superbus, which are argued here to represent an early form of the osteichthyan inner dental arcade, display a previously unknown and presumably primitive mode of tooth shedding by basal hard tissue resorption. They carry regularly spaced, recumbent...

Placoderms are considered as the first jawed vertebrates and constitute a paraphyletic group in the stem-gnathostome grade. The acanthothoracid placoderms are among the phylogenetically most basal and morphologically primitive gnathostomes, but their neurocranial anatomy is poorly understood. Here we present a near-complete three-dimensional skull...

Anatomical abbreviations used in the figures. (XLS)

Romundina stellina, MNHN.F.CPW1, filling of the internal structures and rotation around the specimen. (0400–0750 (Nouveau).avi: Maya Autodesk; 25 MB. (AVI)

Romundina stellina, MNHN.F.CPW1, rotation of the endocranial cavity. olaf_002: Mimics; 5,28 MB. (AVI)

Romundina stellina, MNHN.F.CPW1, rotation of the right inner ear. olaf_006: Mimics; 8,61 MB. (AVI)

Remark concerning the myodomes and the extrinsic muscles in the orbit. (DOC)

Romundina stellina, MNHN.F.CPW1, complete run-through (contrasted) (complete_runthrough_contrasted_avi.avi; 19,8 MB). ImageJ. (AVI)

Skull of Romundina stellina Ørvig, 1975. Specimen MNHN.F.CPW6. A. Dorsal view. B. Left lateral view. C. anterior view. D. posterior view. Scale bar 10 mm. Notice in B the light in the foramen for the pituitary vein indicating that it opens in a canal opening in the right orbit. (TIF)

Romundina stellina, MNHN.F.CPW1, rotation of the dermal bone and perichondral bone vasculature (vertical_rotation.avi; VG StudioMax, SS and PT). (AVI)

Romundina stellina, MNHN.F.CPW1, apparition of the 3D model emerging from below the photograph of the actual specimen. The dermal skull roof opens to reveal the internal perichondral structures. 0001–0125 (nouveau).avi: Maya Autodesk; 3,88 MB. (AVI)

Romundina stellina, MNHN.F.CPW1, rotation around the internal perichondral bone ossification, revealing the lace pattern. 0125–400 (nouveau).avi: Maya Autodesk; 21,3 MB. (AVI)

Romundina stellina, MNHN.F.CPW1,: rotation of model with external perichondral bone opaque. olaf_004; Mimics;16,9 MB. (AVI)

Romundina stellina, MNHN.F.CPW1, rotation of model with external perichondral bone semitransparent. olaf_005; Mimics;16,9 MB. (AVI)

Romundina stellina, MNHN.F.CPW1, rotation of left inner ear. olaf_007; Mimics; 8,35 MB. (AVI)

Romundina stellina, MNHN.F.CPW1, rotation of opaque dermal bone of the skull roof. olaf_012; Mimics; 14 MB. (AVI)

Romundina stellina, MNHN.F.CPW1, endocranial cavity filled plus cranial nerves plus part of the sensory line system. olaf_020: Mimics; 7,73 MB. (AVI)

Romundina stellina, MNHN.F.CPW1, rotation of external perichondral bone semitransparent with internal vacularization opaque. olaf_021; Mimics; 12,1 MB. (AVI)

Romundina stellina, MNHN.F.CPW1, rotation of endocranial cavity, inner ears and right endolymphatic duct. olaf_019; Mimics; 10,5 MB. (AVI)

Romundina stellina, MNHN.F.CPW1, rotation of model without external perichondral and dermal bone. olaf_003; Mimics;11,4 MB. (AVI)

Romundina stellina, MNHN.F.CPW1, rotation of dermal bone vasculature, nerves, arteries and veins. olaf_010; Mimics; 12,5 MB. (AVI)

Romundina stellina, MNHN.F.CPW1, rotation of specimen semitransparent showing inner structures. olaf_018; Mimics; 16,3 MB. (AVI)

Lophosteus superbus is one of only a handful of probable stem-group osteichthyans known from the fossil record. First collected and described in the late 19th century from the upper Silurian Saaremaa Cliff locality in Estonia, it is known from a wealth of disarticulated scales, fin spines, and bone fragments. In this study we provide the first desc...

The teeth of gnathostomes (jawed vertebrates) show rigidly patterned, unidirectional replacement that may or may not be associated with a shedding mechanism. These mechanisms, which are critical for the maintenance of the dentition, are incongruently distributed among extant gnathostomes. Although a permanent tooth-generating dental lamina is prese...

The transition from fish to tetrapod was arguably the most radical series of adaptive shifts in vertebrate evolutionary history. Data are accumulating rapidly for most aspects of these events, but the life histories of the earliest tetrapods remain completely unknown, leaving a major gap in our understanding of these organisms as living animals. Sy...

Recent advances in synchrotron imaging allow us to study the three-dimensional (3D) histology of vertebrate fossils, including microfossils (e.g. teeth and scales) of early jawed vertebrates. These microfossils can often be scanned at submicron resolution (<1 µm) because of their small size. The resulting voxel (3D pixel) stacks can be processed in...

We used propagation phase contrast X-ray synchrotron microtomography to study the three-dimensional (3D) histology of scales of two osteostracans, Tremataspis and Oeselaspis, members of a jawless vertebrate group often cited as the sister group of jawed vertebrates. 3D-models of the canal systems and other internal structures are assembled based on...

Certain aspects of the fish-tetrapod transition are still incompletely known, especially those concerning the dermal skeleton, comprising certain skull bones, fin rays, and scales. Early tetrapods (limbed vertebrates) were extensively covered with dermal scales, inherited from their sarcopterygian (lobe-finned fishes) relatives. These scales were i...

Because of its close relationship to tetrapods, Eusthenopteron is an important taxon for understanding the establishment of the tetrapod body plan. Notably, it is one of the earliest sarcopterygians in which the humerus of the pectoral fin skeleton is preserved. The microanatomical and histological organization of this humerus provides important da...

Le réexamen du myxiniforme présumé Myxineidus gononorum du Carbonifère supérieur de Montceau-les-Mines au moyen de la microtomographie par rayonnement X synchrotron en contraste de phase de propagation confirme la présence de deux séries de denticules non minéralisés et disposés en chevrons dans la cavité orale. Il indique également la présence pos...