Lucas LegendreUniversity of Texas at Austin | UT · Jackson School of Geosciences
Lucas Legendre
PhD
About
34
Publications
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Introduction
My research focuses mainly on the evolution of biomineralized structures in vertebrates (e.g. bone, cartilage, eggshells), using histology and microscopy techniques. I use phylogenetic comparative methods on such microstructural traits to assess their life history correlates and reconstruct their evolutionary history.
I am currently a postdoc in the Clarke Lab at UT Austin, working on the evolution of the syrinx in modern birds, as well as reptile eggshell microstructure, among other projects.
Additional affiliations
July 2016 - June 2018
October 2011 - September 2014
October 2011 - September 2014
Education
October 2011 - September 2014
September 2009 - July 2011
September 2006 - July 2009
Publications
Publications (34)
Metabolic heat production in archosaurs has played an important role in their evolutionary radiation during the Mesozoic, and their ancestral metabolic condition has long been a matter of debate in systematics and palaeontology. The study of fossil bone histology provides crucial information on bone growth rate, which has been used to indirectly in...
The presence of a phylogenetic signal in the variation of osteohistological features has been recently debated in the literature. Previous studies have found a significant signal for some features, but these results were obtained on a small amount of characters and a reduced sample. Here we perform a comprehensive study in which we quantify the phy...
The study of bone growth rate and metabolic rate evolution in archosaurs (crocodiles, dinosaurs including birds, and pterosaurs) and close outgroups has become a subject of major interest among paleontologists in recent years. In this paper, we estimate the bone growth rate of Euparkeria using a new statistical inference model for the humerus. We m...
There is currently a debate about the presence of a phylogenetic signal in bone histological data, but very few rigorous tests have fuelled the discussions on this topic. Here, we performed new analyses using a larger set of seven histological traits and including 25 taxa (nine extinct and 16 extant taxa), using three methods: the phylogenetic eige...
The avian palaeognath phylogeny has been recently revised significantly due to the advancement of genome-wide comparative analyses and provides the opportunity to trace the evolution of the microstructure and crystallography of modern dinosaur eggshells. Here, eggshells of all major clades of Palaeognathae (including extinct taxa) and selected eggs...
Reptile eggshell ensures water and gas exchange during incubation and plays a key role in reproductive success. The diversity of reptilian incubation and life history strategies has led to many clade-specific structural adaptations of their eggshell, which have been studied in extant taxa (i.e. birds, crocodilians, turtles, and lepidosaurs). Most s...
Significance
The controversy over the taxonomic identity of the eggs exploited by Australia’s first people around 50,000 y ago is resolved. The birds that laid these eggs are extinct, and distinguishing between two main candidates, a giant flightless “mihirung” Genyornis and a large megapode Progura , had proven impossible using morphological and g...
The bone histology of non-avian theropods such as Troodon, early pygostylians such as Confuciusornis, and neornithines, is characterized by the post-hatching formation of fibrolamellar complex. In contrast, the cortex of enantiornithine birds, like Concornis and Iberomesornis, is made of poorly vascularized parallel-fibred tissue. The cortex of met...
Birds share an array of unique characteristics among extant land vertebrates. Among these, external and microstructural characteristics of extant bird eggs have been linked to changes in reproductive strategy that arose among non‐avian theropod dinosaurs. More recently, differences in egg proportions recovered in crown birds relative to other dinos...
A recent study by Norell et al. (2020) described new egg specimens for two dinosaur species, identified as the first soft-shelled dinosaur eggs. The authors used phylogenetic comparative methods to reconstruct eggshell type in a sample of reptiles, and identified the eggs of dinosaurs and archosaurs as ancestrally soft-shelled, with three independe...
For over a century, researchers have assumed that the plane of the lateral semicircular canal of the inner ear lies parallel to the horizon when the head is at rest, and used this assumption to reconstruct head posture in extinct species. Although this hypothesis has been repeatedly questioned, it has never been tested on a large sample size and at...
Egg size and structure reflect important constraints on the reproductive and life-history characteristics of vertebrates. More than two-thirds of all extant amniotes lay eggs. During the Mesozoic era (around 250 million to 65 million years ago), body sizes reached extremes; nevertheless, the largest known egg belongs to the only recently extinct el...
Endothermy, i.e. the endogenous production of metabolic heat, has evolved multiple times among vertebrates, and several strategies of heat production have been studied extensively by physiologists over the course of the twentieth century. The independent acquisition of endothermy by mammals and birds has been the subject of many hypotheses regardin...
As the largest and among the most behaviourally complex extant terrestrial mammals, proboscideans (elephants and their extinct relatives) are iconic representatives of the modern megafauna. the timing of the evolution of large brain size and above average encephalization quotient remains poorly understood due to the paucity of described endocranial...
Les méthodes phylogénétiques comparatives (PCM) sont devenues au cours de la dernière décennie une discipline majeure de la systématique et de la biologie de l'évolution, et un nombre croissant de publications dans ces domaines est consacré à l'application de ces méthodes à des problématiques liées à la systé-matique. Toutefois, la plupart de ces p...
Bone microstructure has long been known as a powerful tool to investigate lifestyle-related biomechanical constraints, and many studies have focused on identifying such constraints in the limb bones of aquatic or arboreal mammals in recent years. The limb bone microstructure of fossorial mammals, however, has not been extensively described. Further...
List of specimens and histological sections depicted in each panel of every histological figure in this paper (i.e. Figs. 2–7).
For each column, a given section number corresponds to that of the section of the bone mentioned in the first line of that column, for each corresponding specimen. For sections taken from specimen MVD-M1, for which bones f...
Phylogenetic comparative methods (PCM), i.e. methods designed to take into account the influence of phylogenetic relationships between species in statistical analyses of quantitative datasets, have grown to become an essential part of evolutionary biology in the last decade. These methods, along with the improvement of associated software and outre...
Phylogenetic comparative methods (PCM) have become an essential part of systematics and evolutionary biology for more than a decade, and an increasing number of communications in research conferences include entire sections dedicated to methodological considerations on this matter. Most of these communications, however, do not provide extensive inf...
Presentation on preliminary results on the histology of the aardvark, with emphasis on the link between burrowing activity and bone microstructure.
The furcula is a specialized bone in birds involved in flight function. Its morphology has been shown to reflect different flight styles from soaring/gliding birds, subaqueous flight to high-frequency flapping flyers. The strain experienced by furculae can vary depending on flight type. Bone remodeling is a response to damage incurred from differen...
Archosaurs are a clade of vertebrates that includes birds, crocodiles, and numerous fossil groups. This clade has been a matter of debate among paleontologists for decades concerning the evolution of its thermometabolism. The classical hypothesis considers that only modern birds are truly endotherms (i.e. able to produce their own body heat), where...
Aepyornis, a giant subfossil ratite from Madagascar, shows a well-preserved bone histology. Hindlimb bones exhibit an extensive histodiversity; the cortex is initially made of fibrolamellar, well-vascularized primary bone that modulates locally into plexiform or laminar patterns. Lines of arrested growth are generally weakly expressed. Haversian re...
The research group known as “Formations squelettiques” team, specialized in the study of mineralized tissues of vertebrates, has been active for 40 years, starting in 1968. In this paper, we review the history of this group from its most remote roots – the original chair of Comparative Anatomy at the Faculty of Sciences in Paris – and explain its s...
Archosaurs are a clade of vertebrates that includes birds, crocodiles, and numerous fossil groups. This clade has been a matter of debate among paleontologists for decades concerning the evolution of thermometabolism in its different lineages. The classical hypothesis considers that only modern birds are true endotherms, whereas all other archosaur...
Periosteal, endosteal, and intracortical blood vessels bring oxygen and nutrients to, and evacuate the metabolic by-products from, osteocytes. This vascular network is in communication with bone cells through a network of canaliculi containing osteocyte cytoplasmic processes. The geometric and physiological constraints involved in the relationships...
Ever since Eldredge and Gould proposed their model of punctuated equilibria, evolutionary biologists have debated how often this model is the best description of nature and how important it is compared to the more gradual models of evolution expected from natural selection and the neo-Darwinian paradigm. Recently, Cubo proposed a method to test whe...
Projects
Project (1)
This project aims to investigate the fossorial activity of modern mammals, using histological thin sections of limb bones to evaluate biomechanical and structural constraints associated with burrowing. Phylogenetic comparative methods will also be applied to microanatomical features to identify potential correlation between fossoriality and bone microstructure, as well as associated evolutionary trends.
