L’équipe de recherche « Formations squelettiques » est un regroupement d’enseignants–chercheurs et de chercheurs qui ont développé leurs activités sur une bonne quarantaine d’années, soit de 1968 à 2008. Leurs travaux scientifiques concernent essentiellement l’étude comparative des tissus squelettiques des Vertébrés, dans des perspectives fonctionnelles et évolutionnistes.

The research group known as “Formations squelettiques” team was composed of University professors and of full-time research scientists (CNRS) who have dedicated their research to the study of vertebrate mineralized tissues for more than 40 years, starting in 1968.

To tell the story of this research group without proper historical and scientific background would be meaningless, because scientists are influenced by these two factors. On one hand, they work within their own time in connection with other scientists spread among various laboratories of numerous countries all over the world. On the other hand, they set their activities within a knowledge derived from the works of their predecessors over several generations, sometimes very remote in time (Schmitt, 2006).

Without attempting to provide a historical survey of the “mother discipline” from which the team comes, namely Comparative Anatomy, it is useful to offer some historical landmarks.

Without going back to Aristotle, nor attempting a detailed historical review, it seems nevertheless useful to recall some steps in the long history of comparative anatomy (Schmitt, 2006), a rich and fascinating scientific domain of which we are heirs and followers.

Before the French Revolution, scientists had to rely almost exclusively on the sponsorship of the King and aristocracy. Apart from the Academy of Sciences (founded in 1666), two well-structured scientific institutions were the Collège Royal (King's College, established in 1530) and the Jardin du Roi (King's Garden, established in 1639), which would evolve respectively into the Collège de France (named as such during the Restauration in 1815–1830) and the Museum National d’Histoire Naturelle (National Museum of Natural History, in 1793). It was mostly the second institution that gave the impetus to the Paris University in natural sciences, in research as well as in teaching, during the beginning of the 19th century; the University (La Sorbonne) then quickly took its scientific destiny into its own hands.

With the Revolution, the situation of scientists quickly changed as science became more and more institutionalized during the first half of the 19th century. Let us go back to those early post-revolutionary years: the Opening of the Science Faculty of the Paris University took place in 1811. Because the teaching and scientific skills were located at the Museum and at the Collège de France, the authorities thus appealed to the Professors of those institutions to provide the lectures. Georges Cuvier, then already a famous anatomist and paleontologist at the Museum, was appointed vice-rector of the Faculty by the Academy of Sciences. He created the chair in “Comparative anatomy and physiology”, first held by his friend and collaborator Étienne Geoffroy Saint-Hilaire (Le Guyader, 1998). At the beginning, because the Faculté des sciences had no dedicated building, the lectures were given in the Museum's lecture halls in the Jardin des Plantes. The Faculty of Sciences settled in its own buildings at the Sorbonne in 1821–1822, but there were no research laboratories in the Faculty until 1855.

After several decades and name changes caused by the development of natural history and biological sciences, the original chair of the early 19th century was split into two in 1847. The first of these two resulting chairs, entitled “Zoology, Anatomy, and Comparative Physiology”, first held by Henri Milne Edwards, mostly focused on the anatomy and physiology of metazoans, and resulted in the creation of the still active Marine Biological Station in Roscoff (Brittany). Many prominent zoologists held the chair, including Yves Delage, Charles Pérez, and Georges Teissier, who made a significant contribution to the development of the concept of allometry. ¹ 1

Teissier used the allometry equation in his studies on the growth of insects (Teissier, 1931) and reached an agreement with Julian Huxley to develop a common terminology on relative growth: they coined the terms allometry and isometry in two papers published simultaneously in English and in French (see a review in Gayon, 2000). Beyond the terminological issues, a conceptual disagreement existed between them: for Julian Huxley, the intercept of the allometry equation is only a statistical parameter, which depends on the measurement units, whereas for Georges Teissier this parameter may have a biological significance (Gayon, 2000). According to the results obtained by Katz (1980), Teissier was right: the intercept of the allometric equation describing the relative growth of two parts of an organism may correspond to the relative number of cell division centers of these parts.

The second chair, entitled “Anatomy and Comparative Physiology”, focused more on vertebrates, and was held by many followers of Georges Cuvier and Étienne Geoffroy Saint-Hilaire for Comparative Anatomy. Among them were Henri-Marie Ducrotay de Blainville, Isidore Geoffroy Saint-Hilaire (Étienne's son), Louis Pierre Gratiolet, Paul Gervais, Henri de Lacaze-Duthiers, George Pruvot, and Paul M.J. Wintrebert. Special mention should be made of Paul Gervais (1816–1879) who, through his numerous works on the hard tissues of extant and extinct vertebrates, turned out to have paved the way that we followed a century later (e.g. de Ricqlès et al., 2009, Meunier and Herbin, 2014 and Taquet, 2001), and to Paul Wintrebert (1867–1966), who famously coined the term “cytoskeleton” in 1931, and changed the name of the chair to “Comparative Anatomy and Histology”, thus starting the tradition of histological preparation and teaching that would later shape the origin of our group.

Lectures, practical classrooms and research took place at La Sorbonne up to the early 1960s, when the Faculté des Sciences was relocated to the brand new Jussieu campus, which was better adapted to its duties of university teaching and basic research. The Laboratory of Comparative Anatomy and Histology was among the first to move from the old Sorbonne to the new facilities in 1961.

Let us go back to the Chair of Comparative Anatomy and Histology: headed by Marcel Prenant since 1937, it led the Laboratory of Comparative Anatomy and Histology set on two floors (levels 2 and 3) at 7, quai Saint-Bernard (Building A) of the new campus, and of a third level (on the first floor) devoted to practical classrooms, teaching, and an extensive collection of anatomical and zoological specimens used for teaching, and organized in part as a pedagogical Museum of Zoology.

One of the great contributions of M. Prenant is to have developed, after a first try by P. Wintrebert and M. Parat before the war (Prenant, 1966), an intensive teaching program of histological techniques, following a path set by his father, Auguste Prenant (1861–1927), at the Faculty of Medicine at the beginning of the 20th century. During the second half of the 20th century, this specialized practical cursus in histology was taken by a large number of scientists.

In Marcel Prenant's laboratory, research was not organized in research groups or teams devoted to a common research goal. Each student, or scientist, had his own research subject on an animal model (some of which were vertebrates), that “belonged” to him (or her). Its main tool for research remained topographical histology with its histochemical extensions, to describe the animal's general organization, its development and/or its biological peculiarities, sometimes associated with various experimental approaches. As Professor Prenant put it during his valetudinary lecture: “In my Laboratory, I have been watchful that the research goals remained based, in priority, on the use of histological techniques […]. Histology is merely a means, but put in service of diversified problems and models depending of the scientists’ orientation, histology is also a rallying point, a way of thinking, and a common language.” (Prenant, 1980, p. 324). The only link among scientists, as far as research was involved, actually remained the use of histology techniques, through what would now be called a technical platform. The close links that Marcel Prenant kept with the Marine Biological station in Roscoff (Devillers, 1966 and Teissier, 1966), of which he had been the director for several years, allowed marine animals to hold a large place in the theses defended during those years.

Nevertheless, vertebrates were not absent from the research activities of the Laboratory of Comparative Anatomy and Histology, as demonstrated in two noteworthy theses defended respectively by Charles Devillers (1947) on the development of the dermal bones of the skull, and by Yves François (1958) on the development of vertebrae and fins, both on teleostean models (Meunier, 2000). The contributions of Devillers to the great Traité de Zoologie (Devillers, 1954a, Devillers, 1954b and Devillers, 1958), as well as numerous pedagogical handbooks published by both authors for the Paris students (notably seven illustrated booklets on Agnathans, Chondrichthyans, Osteichthyans, Amphibians, Reptiles, Birds, and Mammals), firmly established the vertebrate comparative anatomy developed at the Sciences faculty within the long lineage of heirs of Cuvier and Geoffroy Saint-Hilaire. It was in Marcel Prenant's laboratory, and more especially within the fertile milieu of actinopterygian comparative and developmental anatomy, that the “Équipe Formations squelettiques” found its roots.

In 1966, Marcel Prenant retired and his laboratory was split into two entities (Prenant, 1966): the Laboratory of Comparative Anatomy (second floor) with Professor Charles Devillers as Director, and the Laboratory of Cytology (third floor) under the Directorship of Professor René Couteaux, who worked on the “motor plate” or neuromuscular junction. Strengthened by the tradition left by former generations of great teachers, the lectures on Comparative Anatomy and Zoology given in the Paris Faculté des Sciences by competent teachers shaped new generations of post-war students. Those high-level lectures stimulated some of them to begin doctoral studies in histology.

Thanks to the creation, during the 1960s, of a fair amount of positions for teaching and research, as the University trained numerous students from the post-war “baby boom” generation, the Parisian laboratories recruited young assistant professors, well motivated for teaching and scientific research. These were happy days when recruitment could take place after a Master's degree or roughly equivalent titles!

Because those younger teachers had received a strong training in Zoology and Comparative Anatomy, the time was ripe for a restructuring of research and new scientific endeavors. Gone were the solitary scientists of the fifties with individual and disparate research subjects, only united by the same techniques of histology: now came the time of research teams focused on a scientific subject that became the target of research programs. Paraffin histological techniques were no longer the ultimate tool; they remained useful, inescapable, but became extensively associated with new, specialized tools, especially in our field of skeletal hard tissues (see below).

Following the turmoil of the May–June 1968 events that led to the “Law of orientation of higher education” (known as Loi Edgar Faure), the Science Faculty of the Paris University was dismantled and replaced by two new pluridisciplinary Universities: Paris-6 (Pierre-et-Marie-Curie) and Paris-7 (Denis-Diderot), oddly intermingled on the Jussieu Campus, which had expanded following the final departure of the last “pinardiers” (wine traders: the Jussieu campus was built on the former “Halle aux vins”, Paris’ gross wine market facilities, and is sometimes still known under this nickname).

In the Laboratory of Comparative Anatomy, five research teams were organized around their respective scientific leaders: •

developmental biology (C. Devillers, 1914–1998);

All the University staff (teachers, researchers, and technicians) were requested to choose between one of the new Universities. Like most of the staff in the aforementioned five research teams, the team led by Yves François chose University Paris-7 and got the name of “Formations squelettiques”. It remained in Building A, second floor (Laboratoire d’anatomie comparée), with some extra-technical rooms on the eighth floor. However, all teaching facilities on the first floor were used by Paris-6, and the teaching for Paris-7 had to be performed elsewhere; in the end, lectures and practical classrooms were hosted in an “Animal Biology” teaching facility set far away on the Campus, at the third floor of towers 23–33. Similarly, former collections and libraries were split through a time-consuming and expensive process. Nevertheless, a constant will animated the teachers and researchers: to maintain a close link in their activities between research and teaching.

The team “Formations squelettiques” was organized by Yves François (Professor) and Armand de Ricqlès (Assistant), with the recruitment of “new assistants” François Meunier and Jacqueline Géraudie in 1967, and Jacques Castanet and Hélène Francillon in 1969. The team was completed by two technicians: Mrs. Paulette Koechlin (administration, secretary) and Yvette Rupaud (histology, animal facilities). Some years later, in 1981, Françoise Allizard (CNRS) brought to the group her masterful practice of ultrathin sectioning for the TEM. In 1977–1979, the team increased its staff with the arrival of Dr. Louise Zylberberg (CNRS) and two doctoral students: Vivian de Buffrénil for a thesis on varanid squamate histology, and Jean-Yves Sire for a thesis on the scales of Cichlid teleosts. de Buffrénil subsequently got a position in the Paris Museum, and Sire in the CNRS, and both remained with the team for their postdoctoral research (Fig. 1 and Fig. 2).

Given that vertebrate skeletal hard tissues are strongly mineralized, the use of classical paraffin microtomy obviously requires removing the mineral component, hence the tissues lose their specific component in the process. Accordingly, a good part of their biological information is lost. One has thus to turn to petrographic techniques and adapt them to study bone and dental tissues. Those adaptations, first performed for the study of human (and more generally mammalian) hard tissues, were extended to other vertebrate groups. Polymerisable plastics replaced paraffin, and thin circular blades with diamond powder and polishing machines replaced the classic Minot's microtome. Finally, new “soft” X-ray generators, adapted to the characteristics of microscopical thin sections (100 μm or less) allow qualitative and quantitative studies of the mineral components in situ (Boivin and Baud, 1984). Those techniques, which quickly became part of the routine, also allowed the scientists of the team “Formations squelettiques” to explore the rich field of fossilized hard tissues which, under favorable taphonomic conditions, allow us to study the evolution of tissues in deep time (over 500 million years; e.g. Chinsamy et al., 1995, de Ricqlès, 1977, de Ricqlès, 2007, Meunier, 2011 and Steyer et al., 2004).

Quantification of growth dynamics and chronology were experimentally analyzed by the team on extant models thanks to vital dyes (e.g. de Margerie et al., 2004, Meunier, 1972, Meunier, 1974, Sire et al., 1993 and Trébaol et al., 1991). Three doctoral theses on this topic were defended in 1982 (J. Géraudie, J. Castanet, F. Meunier), following in the footsteps of A. de Ricqlès, who had defended his thesis in 1973. In 1982, the team leader Yves François retired, and Armand de Ricqlès took over.

During the 1980s and 1990s, some doctoral students joined the team before being employed to work on other research topics or in other teaching structures. Some of the youngest ones are now the heirs of this long tradition in comparative anatomy and histology of the vertebrate skeleton.

In order to thrive in the University environment, the team had to raise sufficient funding for its research and to train new doctoral students. To attract students, the team took part in the creation and daily operations of a new graduate program starting at the Master's degree level, the DEA “Structures and Functions in Vertebrates Evolution”, which opened in 1981.

We employed a few doctoral students from this program, notably Marina Alcobendas, Virginie Levrat and Frédérique Lecomte, who strengthened the group for several years. At the same time, we strengthened already strong links with laboratories of the Muséum National d’Histoire Naturelle, notably those of paleontology (Professor J.-P. Lehman) and comparative anatomy (Professor J. Anthony), especially with a group working on tetrapod locomotion, which was strongly involved within the DEA “Structures and Functions”, co-organized by the Museum and Paris-7 University. This DEA later gave birth to the Master's degree program “Systematics, Evolution, and Paleontology” (still operational), through which a few more students later contributed to several projects of the team between 2000 and 2008.

To fund our research, extramural financial support was needed, especially given that the University had seen its resources dwindle, and at best stabilized following the first oil crisis (1974). During the late 1970s/early 1980s, the best option for university research teams was to seek financial support from the CNRS, which would also enhance scientific visibility. Even though the CNRS normally supports fairly large research groups, we were recognized as a “Jeune équipe” (“young team”) in 1982, with Armand de Ricqlès as director. It was a major victory and the beginning of our long-lasting association with the CNRS. This was confirmed in 1985 with the creation of the URA (associated research unit) 1137 which, in order to reach its “critical mass”, included both our research team and the team “Animal Locomotion” led by Dr. Françoise Jouffroy in the Laboratory of Comparative Anatomy of the Museum. A long-lasting cooperation between the two teams followed, requiring diplomatic skills and flexibility in the administration of available funding, but above all allowing fertile discussions on our research themes and their evolution within the research and teaching structures (Fig. 3). Within the framework of the URA, we had the opportunity to recruit two new able technicians: Mrs Jacquie Bourguignon and Marie-Madeleine Loth who took the positions of P. Koechlin and Y. Rupaud after their retirements.

The heart of our research topic is the comparative study of skeletal tissues among vertebrates, set in an explicit evolutionary framework. The main focus was first put on extant and extinct ectothermic vertebrates, mostly actinopterygians and reptiles, with emphasis on ontogeny, differentiation, growth, maturation, function, and evolution. Later on, we added mammals and birds to our biological models, using the opportunities offered by collaborative projects or the arrival of new doctoral students. The comparative study of vertebrate hard tissues (mainly bone) became a crossroad, the center of a transdisciplinary web spreading towards numerous other topics (Fig. 1) that stimulated the team and paved the way to numerous national and international collaborations. This created close links with Professor Melvin J. Glimcher (1925–2014) of Harvard Children's Hospital, Boston, who came several times to work with the team and contributed much to our efforts to decipher the intimate relationships between the organic and mineral components of fossil and extant hard tissues (Cohen-Solal et al., 1987). Other long-term collaborators include Professors J.R. Horner (Museum of the Rockies, Bozeman University, Mt.) and K. Padian (University of California, Berkeley), who worked with us on the paleohistology of archosaurs and related taxa (Horner et al., 1999).

We used both classical histological and cytological techniques with light (Francillon, 1974 and Francillon, 1977) and electron transmission microscopy (Quilhac et al., 2014, Sire, 1988, Sire and Géraudie, 1983, Sire and Géraudie, 1984, Sire and Huysseune, 1993, Zylberberg, 2004 and Zylberberg and Meunier, 1996), topographic and histochemical colorations (Géraudie, 1974), experimental embryology (Géraudie, 1981), raising animals at the laboratory and monitoring in the wild. We have developed various techniques: thin sections, vital dyes (de Margerie et al., 2004 and Francillon and Castanet, 1985), qualitative and quantitative micro X-rays (Alcobendas and Castanet, 1985 and Meunier, 1984), ultrathin sections of extant and fossil non-demineralized tissues (Rimblot-Baly et al., 1995 and Zylberberg and Laurin, 2011), MEB (Géraudie and Singer, 1981), electron microscope (Zylberberg and Meunier, 1984)…

Mineralized hard tissues can be somewhat viewed as “black boxes” as far as they are persistent in the organisms. Deciphering the “message” recorded in those tissues yields functional clues about the skeleton and the organisms. The results gained on extant organisms (where experimental data can be recorded) can be extended, mutatis mutandis, to extinct vertebrates, whenever preservation of the tissue fine structure is sufficiently good (de Buffrénil et al., 1987, de Buffrénil et al., 1990, de Ricqlès, 2000, Horner et al., 1999 and Meunier and Laurin, 2012). Within a Darwinian-evolutionary framework, we moved from a “traditional approach” in comparative anatomy and histology, set within the synthetic theory, to research endeavors set within a cladistic framework beginning in the early 1970s.

The creation of the “Groupe d’étude pratique de squelettochronologie” (GEPS; group for the pratical study of skeletochronology) in December 1977 enhanced the visibility of the team. This organization sought to meet a strong demand for the understanding of growth dynamics and age structure of populations from the scientific community, especially ecologists. This is explained in the original catalog presenting this technical support structure:

“Because they are hard, vertebrate skeletal tissues behave in various ways as biological recorders. The most familiar use of this tissular peculiarity is scalimetry, used to assess age of fishes (but this method is only available, of course, among scale-covered bony fishes). […] More and more workers belonging to various scientific fields – Ecology, Demography, Prehistoric research and Archeology, Rythmology – are now becoming aware of the advantages that could be gained, for their particular studies, by making full practical use of the information recorded in the microscopic structure of bone, dentine, and cementum. Considering such information allows research into new directions. One of the most important and promising prospect in this field, but not the only one, is of course to evaluate individual age thanks to skeletal microstructure. […] Skeletochronology uses various hard tissues that are found among all vertebrates (bone, dentine, cementum…). Some of those hard tissues, among many vertebrates (and not only among poikilotherms with indefinite growth) are laid down in successive layers of varying aspect. Already available descriptive and experimental evidence now offers enough theoretical background, and instances of technical processing, to allow a widespread practical use: not only can individual age be reliably assessed, but other data like speed of growth, age of sexual maturity, and longevity, can be gained from skeletochronological surveys”. Such inferences are illustrated by several papers of the team (Castanet et al., 1996, de Buffrénil et al., 1994 and Meunier et al., 1997…).

Over a period of 25 years, several dozen scientists, experienced to beginners, from various countries (Canada, USA, Peru, Ivory Coast, Mali, South Africa, Tunisia, Morocco, Spain, Portugal, Poland, England, Greece) as well as from France, came to work with us to learn and use skeletochronological techniques. This fruitful scientific activity led to the organization of “roundtables” (Société zoologique de France, 1980), of symposia (Colloque de Bondy in 1991; see Baglinière et al., 1992) and to our contribution to several textbooks and specialized books and reviews, some of them likely to remain as references of the “state of the art” about the skeletal tissues of vertebrates at the end of the 20th century (Castanet et al., 1993, de Ricqlès et al., 1991, Francillon-Vieillot et al., 1990 and Zylberberg et al., 1992). In the foreword of Volume 7 of “Bone” series of which he was the Editor, Prof. Brian K. Hall, the noted Canadian embryologist, expressed this opinion of our chapter (Castanet et al., 1993): “… Chapter 9 completes a series of superb chapters produced for this series by the French workers in the Équipe de Recherche ‘Formations squelettiques’ of the Université Paris-7. In this chapter they provide a masterly synthesis of the use of growth marks preserved in bone to age individual organisms, the discipline of skeletochronology…”.

It is not possible here to record all the interesting results obtained by the team over the decades. The extensive works on the dermal skeleton of vertebrates allowed us to discover important new data. The peculiar “double twisted plywood” structures in the scales of Sarcopterygians, including extant Latimeria and Dipnoans, was deciphered and still offers fascinating models for further biophysical analyses. New mineralized tissues types, with either collagenous or non-collagenous matrices, which are neither dentine nor bone, were discovered and described in various actinopterygians and amphibians.

The implication of extracellular material of epidermal origin, as well as the metaplastic conversion of melanophore cells into bone forming cells, have been demonstrated in several models of osteichthyan scales.

TE microscopy of demineralized ultrathin sections of Mesozoic and Paleozoic skeletal tissues demonstrated the continuous occurrence of non-collagenic and collagenic matrices in very old fossils, including the fibrillar pattern and cross striation of Type 1 collagen. The extensive development of skeletochronology allowed us to decipher important life history traits in a large number of actinopterygians, amphibians, and reptiles, sometimes including histological evidence of sexual dimorphism during growth. Especially noteworthy was the demonstration of “double yearly growth cycles” in teleosts and amphibians living under peculiar ecological conditions. Cases of “Island gigantism” linked to the selection of “K growth strategies” among reptiles have been also deciphered. The discovery of Polypterid remains in South America thanks to palaeohistology exemplifies its usefulness even in paleobiogeography.

The decade-long involvement of the team in comparative paleohistology of archosaurs, with evidence for high growth rates in many dinosaurs, played a major role in the trend towards the “dinosaur renaissance” starting in the 1970s, and ultimately in the issue of the dinosaurian origin of birds. A complete bibliographical census of the team's publications will be attempted elsewhere.

In 2008, most of the “founding members” of the team had retired (some of them already for several years), the research team disappeared, and the remaining members split into two groups: J. Cubo, A. Quilhac, A. de Ricqlès and L. Zylberberg at the Paris-6 University, and V. de Buffrénil, M. Laurin and F. Meunier at the Muséum National d’Histoire Naturelle.

Nevertheless, the “know how” developed during the four decades of the research team has not been lost. Apart from the published scientific results, a generation of scientists trained by the “Formations Squelettiques” team has been recruited in Parisian institutions in recent years: Alexandra Quilhac (Quilhac et al., 2014), Sidney Delgado (Delgado et al., 2008), Damien Germain (Germain and Laurin, 2005) and Alexandra Houssaye (Houssaye, 2014). We also had the opportunity to recruit a new able technician in 2005: Mrs Hayat Lamrous.

The research group headed by Dr. J.-Y. Sire at the Paris-6 University can be viewed as a direct offshoot of the team, now with emphasis on the study of dental tissues with morphological, developmental, and molecular approaches (Delgado et al., 2008 and Sire et al., 2007).

The current development of “non-destructive” techniques of 3D modelingn, linked with tomography (Meunier et al., 2015 and Sanchez et al., 2010) or the “synchrotron light” (Sanchez et al., 2012), opens new prospects for dynamic studies of the anatomy and microanatomy of skeletal tissues. Extant or fossil material may be investigated through these non-destructive techniques and can still yield new data on the evolution, structure and function of vertebrates.

Michel Laurin and Jorge Cubo, educated respectively at the University of Toronto and the University of Barcelona, joined the research team in the late 1990s. Both were interested on analyzing bone osteohistological data using phylogenetic comparative methods (i.e. statistical methods that incorporate phylogeny). They and their PhD students produced paleobiological models to estimate the lifestyle (Canoville and Laurin, 2010 and Germain and Laurin, 2005) and bone growth rate (Cubo et al., 2012 and Legendre et al., 2013) of extinct tetrapods using bone histology. Michel Laurin, now head of the research team “Phylogeny and the diversification of Metazoa” at the Museum National d’Histoire Naturelle, and Jorge Cubo, who leads the Paleohistology research group at the University Paris-6, organized the symposium “Perspectives on vertebrate evolution: topics and problems” (Fig. 4) to celebrate the retirement of Armand de Ricqlès (Cubo and Laurin, 2011 and Laurin, 2011). Coffee break discussions at this symposium were at the origin of the creation of the biennial International Symposia of Paleohistology. The first two meetings, organized in Barcelona (Spain) in 2011 (Fig. 5) and Bozeman (Montana, USA) in 2013 (Fig. 6), were very successful both in terms of number of participants and quality of presentations. The third one is scheduled for July 2015 in Bonn (Germany). In a retrospective view, the research team “Formations squelettiques” can be viewed as a “nucleation point” at the origin of these symposia.

After the forthcoming retirement of the last long-term members of the research team “Formations squelettiques” (Vivian de Buffrénil in 2016 and Jean-Yves Sire in 2018), the community of Parisian comparative hard tissues histology will make a new start. Members of that generation of French bone histologists to which this special issue of C. R. Palevol is dedicated meet regularly with the younger generation and provide valuable input for emerging projects. Some of them have obtained emeritus status in their respective institutions and remain scientifically active (Louise Zylberberg: Emeritus CNRS researcher; Armand de Ricqlès: Honorary Professor at the Collège de France; François J. Meunier: Emeritus Professor at the Museum national d’histoire naturelle). The future looks bright for the new heirs of Georges Cuvier and Étienne Geoffroy Saint-Hilaire, under the leadership of Michel Laurin, at the Paris Museum, Jorge Cubo at the Paris-6 University, their younger Parisian colleagues Sidney Delgado, Damien Germain, Alexandra Houssaye et Alexandra Quilhac, and also in other laboratories in France and elsewhere (Fig. 7).