Inferring the physiological regimes of extinct vertebrates: methods, limits and framework.

What can we know of the physiological regimes of ancient vertebrates? Essential to the exploration of this question are several epistemological tools: (i) a phylogenetic framework for interpreting whole animals and individual tissues, (ii) reliable knowledge of variation in populations and among climates and geographies, (iii) an understanding of phenotypic variation during ontogeny and between sexes, and (iv) a sense of the patterns of body size change, both phyletically and ontogenetically. Palaeobiologists are historically bound to a dichotomous set of terms developed long ago to describe the relatively depauperate living vertebrate fauna. This system sees only binary categories of five major groupings: the 'cold-blooded' fishes, amphibians, and reptiles, and the 'warm-blooded' birds and mammals.

Globuli ossei in the long limb bones of Pleurodeles waltl (Amphibia, Urodela, Salamandridae).

To date, little is known about the structure of the cells and the fibrillar matrix of the globuli ossei, globular structures showing histochemical properties of an osseous tissue, sometimes found in the resorption front of the hypertrophied cartilage in many tetrapods, and easily observed in the long bones of the Urodele Pleurodeles waltl. Here, we present the results obtained from the appendicular long bones of metamorphosed juveniles and subadults using histological and histochemical methods and transmission electron microscopy. The distal part of the cone-shaped cartilage contains a heterogeneous cell population composed of the typical "light" hypertrophic chondrocytes and scarce "dark" hypertrophic chondrocytes.

Developmental plasticity of limb bone microstructural organization in Apateon: histological evidence of paedomorphic conditions in branchiosaurs.

Apateon, a key genus among Branchiosauridae from the Carboniferous--Permian of Europe, is often considered closely related to salamanders on the basis of developmental similarities, anatomical features, and life history. The current work deals with recognition of heterochronies among three "time-averaged populations" of Apateon based on inference from histological features already studied in extant urodeles. Our study is performed on the long bones of 22 specimens of Apateon pedestris and Apateon caducus.

On Darwin's palaeontology in The origin of species.

I investigate the role of palaeontology within Darwin's works through an analysis of the two chapters of The Origin of Species most especially devoted to this science. Palaeontology may occupy several places within the structure of the argumentative logic of Darwinism, but these places have remained to some extent ancillary. Indeed, palaeontology could well document evolutionary patterns, showing the actual occurrence of evolution as a general "historical fact", but it was poorly adapted to demonstrate the main point of Darwinism: the actual evolutionary process: natural selection acting among individuals.

Bone growth marks reveal protracted growth in New Zealand kiwi (Aves, Apterygidae).

The presence of bone growth marks reflecting annual rhythms in the cortical bone of non-avian tetrapods is now established as a general phenomenon. In contrast, ornithurines (the theropod group including modern birds and their closest relatives) usually grow rapidly in less than a year, such that no annual rhythms are expressed in bone cortices, except scarce growth marks restricted to the outer cortical layer. So far, cyclical growth in modern birds has been restricted to the Eocene Diatryma, the extant parrot Amazona amazonica and the extinct New Zealand (NZ) moa (Dinornithidae).

Phylogenetic, functional, and structural components of variation in bone growth rate of amniotes.

The biological features observed in every living organism are the outcome of three sets of factors: historical (inherited by homology), functional (biological adaptation), and structural (properties inherent to the materials with which organs are constructed, and the morphogenetic rules by which they grow). Integrating them should bring satisfactory causal explanations of empirical data. However, little progress has been accomplished in practice toward this goal, because a methodologically efficient tool was lacking.