Alexandra Houssaye

CNRS / Museum National d'Histoire Naturelle · Adaptations du Vivant

In amniote vertebrates that transitioned from land to sea, bone mass typically increases and later decreases as active swimming evolves. A new study now has found that heavy bones re-evolved in some fossil marine mammals, suggesting that this trajectory can be reversed.

In quadrupeds, limb bones are strongly affected by functional constraints linked to weight support, but few studies have addressed the complementary effects of mass, size and body proportions on limb bone shape. During their history, Rhinocerotoidea have displayed a great diversity of body masses and relative size and proportions of limb bones, fro...

The patella is the largest sesamoid bone of the skeleton. It is strongly involved in the knee, improving output force and velocity of the knee extensors, and thus plays a major role in locomotion and limb stability. However, the relationships between its structure and functional constraints, that would enable a better understanding of limb bone fun...

From its first small representatives to its later giant species, the Order Proboscidea evolved increasingly large forms. Limb long bones are heavily affected by shifts in body mass, and this is especially true in proboscideans, in which an increase in body mass is associated with a reorientation of the limb into the parasagittal plane, reducing the...

In mammals, the patella is the biggest sesamoid bone of the skeleton and is of crucial importance in posture and locomotion, ensuring the role of a pulley for leg extensors while protecting and stabilizing the knee joint. Despite its central biomechanical role, the relation between the shape of the patella and functional factors, such as body mass...

The functional signal of bone internal structure has been widely studied. Isolated form‐function relationships have often been assumed from the observation of presumed morphofunctional relationships, but have never been truly tested. Indeed, distinct bone microanatomical feature co‐evolve in response to various constraints that are difficult to det...

Citation: Allemand, R.; Polcyn, M.J.; Houssaye, A.; Vincent, P.; López-Aguirre, C.; Bardet, N. First Virtual Reconstruction of a Mosasaurid Brain Endocast: Description and Comparison of the Endocast of Tethysaurus nopcsai with Those of Extant Squamates. Diversity 2024, 16, 548. https://doi. Abstract: Paleoneurological studies of mosasaurids are few...

The patella is the largest of the sesamoid bones and a central component of the knee joint in mammals. This bone acts like a pulley and enhances the forces of the knee extensor muscles, reinforcing limb stability during locomotion and stance phases. To date, the relationship between patella shape and functional constraints, such as body mass and lo...

Aquatic birds represent diverse ecologies and locomotion types. Some became flightless or lost the ability for effective terrestrial locomotion, yet, certain species excel in water, on land, and in air, despite differing physical characteristics associated with each medium. In this exploratory study, we intend to quantitatively analyze the morpholo...

Theropods are obligate bipedal dinosaurs that appeared 230 Ma and are still extant as birds. Their history is characterized by extreme variations in body mass, with gigantism evolving convergently between many lineages. However, no quantification of hindlimb functional morphology has shown whether these body mass increases led to similar specializa...

Heavy animals incur large forces on their limb bones, due to the transmission of body weight and ground reaction forces, and the contractions of the various muscles of the limbs. This is particularly true for rhinoceroses, the heaviest extant animals capable of galloping. Several studies have examined their musculoskeletal system and the forces the...

Bone is an economical material. Indeed, as moving a heavy skeleton is energetically costly, the vertebrate skeleton is adapted to maximise resistance to the stresses imposed with a minimum amount of material, so that bone tissue is deposited where it is needed. Using bone as a source of inspiration should therefore reduce the manufacturing cost (bo...

Various terrestrial tetrapods convergently evolved to gigantism (large body sizes and masses), the most extreme case being sauropod dinosaurs. Heavy weight‐bearing taxa often show external morphological features related to this condition, but also adequacy in their limb bone inner structure: a spongiosa filling the medullary area and a rather thick...

Sexual dimorphism is challenging to detect among fossils due to a lack of statistical representativeness. The Angeac-Charente Lagerstätte (France) represents a remarkable ‘snapshot’ from a Berriasian (Early Cretaceous) ecosystem and offers a unique opportunity to study intraspecific variation among a herd of at least 61 coeval ornithomimosaurs. Her...

Diverses lignées de vertébrés terrestres présentant des morphologies et des capacités locomotrices variées ont engendré des taxons à très forte masse corporelle. Leur squelette, et notamment le squelette appendiculaire, a dû s'adapter pour supporter un poids élevé. Cette adaptation s'est faite par une association de spécialisations morphologiques e...

During the Mesozoic era, 252 to 66 million years ago, dinosaurs ruled the land, but the ocean deeps were roiling with equally spectacular reptiles—including giant predators. This richly illustrated, authoritative, and accessible book introduces readers to the world of these fascinating marine animals, whose predecessors returned to the seas a few m...

Secondarily aquatic birds encompass diverse ecologies and locomotion types, which are associated with distinct anatomical adaptations. Those taxa that are most adapted to water have lost their ability to fly and, in some cases, their ability for an effective terrestrial locomotion; conversely, there are species that are excellent swimmers or divers...

During evolution, several vertebrate lineages have shown trends towards an increase in mass. Such a trend is associated with physiological and musculoskeletal changes necessary to carry and move an increasingly heavy body. Due to their prominent role in the support and movement of the body, limb long bones are highly affected by these shifts in bod...

Reduced mobility associated with captivity induces changes in biomechanical stress on the skeleton of domesticated animals. Due to bone plasticity, bone's morphology and internal structure can respond to these new biomechanical stresses over individuals' lifetime. In a context where documenting early process of animal domestication is a real zooarc...

Being the largest sesamoid bone, the patella is a central element of the knee joint in most mammals. This bone acts as a pulley and improves the forces of the knee extensors, reinforcing the stability of the limb during locomotion and stance phases. To date, the relationship between the shape of the patella and functional constraints, such as body...

Sexual dimorphism is challenging to detect among fossils, due to a lack of statistical representativeness. The Angeac-Charente Lagerstatte (France) represents a remarkable snapshot from a Berriasian (Early Cretaceous) ecosystem and offers a unique opportunity to study intraspecific variation among a herd of at least 61 coeval ornithomimosaurs. Here...

In mechanical design, it is a common challenge to design parts with high strength-to-weight ratio. Throughout evolution, natural organisms have faced the same challenge and developed a variety of solutions. One of these is the endoskeleton, composed of bones linked by joints. In long bones, near joints, Nature uses an anisotropic porous material, t...

Ichthyopterygia is a major clade of reptiles that colonized the ocean after the end-Permian mass extinction, with the oldest fossil records found in early Spathian substage (late Olenekian, late Early Triassic) strata in the western USA. Here, we describe reptilian remains found in situ in the early Spathian Neocolumbites insignis ammonoid zone of...

Perissodactyls present a great diversity of skeletal morphologies, notably reflecting adaptations to body support and locomotion. Cursorial equids exhibit gracile morphologies favourable for running, graviportal rhinos display massive morphologies suitable for heavy weight-bearing, and mediportal tapirs are characterised by more versatile morpholog...

Weight support is a strong functional constraint modelling limb bones in heavy quadrupeds. However, the complex relations between bone shape, mass, size and body proportions have been poorly explored. Rhinocerotoidea is one of the groups showing the highest body mass reached by terrestrial mammals through time. Here, we explore the evolutionary var...

The long bones and associated musculature play a prominent role in the support and movement of the body and are expected to reflect the associated mechanical demands. But in addition to the functional response to adaptive changes, the conjoined effects of phylogenetic, structural and developmental constraints also shape the animal's body. In order...

In this study, we suggest a method adapted to the retrodeformation of asymmetrical objects – such as limb bones – by quantitatively estimating the eff ectiveness of the Th in-Plate Splines (TPS) interpolation function as a retrodeformation tool. To do so, taphonomic deformations were fi rst simulated on a single horse femur. Th e original bone was...

Sauropodomorph dinosaurs include the largest terrestrial animals that ever lived on Earth. The early representatives of this clade were, however, relatively small and partially to totally bipedal, conversely to the gigantic and quadrupedal sauropods. Although the sauropod bauplan is well defined, notably by the acquisition of columnar limbs, the ev...

The evolutionary history of archosaurs and their closest relatives is characterized by a wide diversity of locomotor modes, which has even been suggested as a pivotal aspect underlying the evolutionary success of dinosaurs vs. pseudosuchians across the Triassic–Jurassic transition. This locomotor diversity (e.g., more sprawling/erect; crouched/upri...

In quadrupeds, the convergent evolutionary trend towards an increase of body mass through time involves changes in constraints linked to weight support. Limb bones are assumed to be particularly modified in heavy quadrupeds, but few studies tried to untangle the complementary effects of mass, size and body proportions on their shape. The superfamil...

The fourth trochanter is an attachment site for the caudofemoral musculature that is located on the posterior side of archosauriform femora. Its morphology is commonly used as a synapomorphy for various archosauriform clades such as its pendant shape in some ornithischian dinosaurs. The fourth trochanter presumably was subjected to strong mechanica...

Land mammals support and move their body using their musculoskeletal system. Their musculature usually presents varying adaptations with body mass or mode of locomotion. Rhinocerotidae is an interesting clade in this regard, as they are heavy animals potentially reaching three tons but are still capable of adopting a galloping gait. However, their...

Hippopotamoids are herbivorous mammals that originated in the late middle Eocene. This taxon includes animals with a great variety of sizes and body proportions, from small and gracile forms with slender limbs to heavy massive ones. Many hippopotamoids have previously been considered semi-aquatic but recent studies have highlighted a diversity of e...

In the transition from a terrestrial to an aquatic environment, sirenian marine mammals reduced and lost their hind limbs and developed a horizontal caudal fin, the main propulsive organ in extant sirenians. Quadrupedal forms are only known from the Eocene and are represented by three different clades: the amphibious “prorastomids,” the aquatic qua...

Limb long bones are essential to an animal's locomotion, and are thus expected to be heavily influenced by factors such as mass or habitat. Because they are often the only organs preserved in the fossil record, understanding their adaptive trends is key to reconstructing the paleobiology of fossil taxa. In this regard, the Bovidae has always been a...

The evolutionary history of archosaurs and their closest relatives is characterized by a wide diversity of locomotor modes. The locomotor superiority hypothesis suggests that this diversity was the main driver of early dinosaur success over pseudosuchians across the Triassic-Jurassic extinctions. The impacts of postural changes (e.g. more sprawling...

Sauropodomorph dinosaurs constitute a well-studied clade of dinosaurs, notably because of the acquisition of gigantism within this group. The genus Plateosaurus is one of the best-known sauropodomorphs, with numerous remains from various localities. Its tumultuous taxonomic history suggests the relevance of addressing its intrageneric shape variabi...

The appendicular skeleton of tetrapods is a particularly integrated structure due to the shared developmental origin or similar functional constraints exerted on its elements. Among these constraints, body mass is considered strongly to influence its integration but its effect on shape covariation has rarely been addressed in mammals, especially in...

Many tetrapod lineages show extreme increases in body mass in their evolutionary history, associated with important osteological changes. The ankle joint, essential for foot movement, is assumed to be particularly affected in this regard. We investigated the morphological adaptations of the astragalus and the calcaneus in Rhinocerotidae, and analys...

10.1016/j.crpv.2019.11.001

The nutrient arteries, located in the long bone diaphysis, are the major blood supply to long bones, especially during the early phases of growth and ossification. Their intersection with the central axis of the medullary area corresponds to the ossification center, and their opening on the outer bone surface to the nutrient foramen. Nutrient arter...

Bone microanatomy appears strongly linked with the ecology of organisms. In amniotes, bone mass increase is a microanatomical specialization often encountered in aquatic taxa performing long dives at shallow depths. Although previous work highlighted the rather generalist inner structure of the vertebrae in snakes utilising different habitats, micr...

Among amniotes, numerous lineages are subject to an evolutionary trend toward body mass and size increases. Large terrestrial species may face important constraints linked to weight bearing, and the limb segments are particularly affected by such constraints due to their role in body support and locomotion. Such groups showing important limb modifi...

Many amniote lineages display convergent evolution towards high body mass through time, which strongly impact (among others) the appendicular skeleton. Species displaying adaptations to sustain a high body mass are said to be graviportal, a term defined alternately by the relative length of limb segments, osteological features, body mass, posture o...

Despite recent advances in noninvasive imaging, Plesiosauria remains one of the least explored clades of reptiles with respect to paleoneuroanatomy. Only partial endocasts, obtained from either latex casts or imprints left on the braincase, have been described. In this contribution, the digital endocasts of three plesiosaurian specimens were analyz...

Isolated ribs and vertebrae of Middle Triassic sauropterygians are studied. The vertebrae have a well‐defined large cavity in their centra, which is a unique feature and is without any modern analogue. The articular facets of vertebrae are made of endochondral bone including calcified as well as uncalcified cartilage. Vertebrae are pachyosteosclero...

Fossils are generally discovered with post-mortem deformations that unavoidably alter their biological information. Because digital visuali-zation allows paleontologists to perform high precision measurements, biomechanical models, 3D-reconstructions, and quantitative comparative analyses, it appears essential to estimate as accurately as possible...

Scholars have debated the taxonomic identity of isolated primate teeth from the Asian Pleistocene for over a century, which is complicated by morphological and metric convergence between orangutan (Pongo) and hominin (Homo) molariform teeth. Like Homo erectus, Pongo once showed considerable dental variation and a wide distribution throughout mainla...

Adaptation to an aquatic lifestyle has occurred independently in numerous amniote lineages. Such ecological shifts commonly engender adaptive changes in the musculoskeletal system. Semi-aquatic taxa highlight the compromises needed to enable locomotion both on land and in water and during the initial stages of the transition from land to water. Int...

A great variation of body sizes and shapes occurs among Perissodactyla and is associated with a diversity of locomotor modes and ecological habits. This variation is reflected in the proportions of the appendicular skeleton, with strong differences between cursorial, mediportal, and graviportal forms. Here we focused on Rhinocerotoidea and explored...

Phenotypic integration, defined as the coordinated co-variation of parts of an organism can be an important constraint on phenotypic diversification. Functional factors, by having an heterogeneous impact across the animal body, may reinforce the integration of some parts while causing a perturbation of the integration among other parts. The integra...

The first tuna-shaped amniotes evolved among ichthyosaurs, but this group exhibits in fact a wide diversity of morphologies and swimming modes. The histology and microanatomical features of vertebral centra of a diversity of ichthyosaur taxa from most basal to highly derived illustrating this variability were analyzed. The occurrence of unusual par...

Long bone inner structure and cross-sectional geometry display a strong functional signal, leading to convergences, and are widely analyzed in comparative anatomy at small and large taxonomic scales. Long bone microanatomical studies have essentially been conducted on transverse sections but also on a few longitudinal ones. Recent studies highlight...

Secondary marine adaptation is a major pattern in amniote evolution, accompanied by specific bone histological adaptations. In the aftermath of the end-Permian extinction, diverse marine reptiles evolved early in the Triassic. Plesiosauria is the most diverse and one of the longest-lived clades of marine reptiles, but its bone histology is least kn...

Brain endocasts obtained from computed tomography (CT) are now widely used in the field of comparative neuroanatomy. They provide an overview of the morphology of the brain and associated tissues located in the cranial cavity. Through anatomical comparisons between species, insights on the senses, the behavior, and the lifestyle can be gained. Alth...