A survey of osteoderm histology and ornamentation among Crocodylomorpha: A new proxy to infer lifestyle?

Osteoderms of eight extant and extinct species of crocodylomorphs are studied histologically and morphologically. Most osteoderms display the typical "crocodilian" structure with a woven-fibered matrix surrounded by an upper and a lower parallel fibered matrix. The dorsal ornamentation of those specimens consists of a pit-and-ridge structure, with corresponding remodeling mechanisms.

Bony pseudoteeth of extinct pelagic birds (Aves, Odontopterygiformes) formed through a response of bone cells to tooth-specific epithelial signals under unique conditions.

Modern birds (crown group birds, called Neornithes) are toothless; however, the extinct neornithine Odontopterygiformes possessed bone excrescences (pseudoteeth) which resembled teeth, distributed sequentially by size along jaws. The origin of pseudoteeth is enigmatic, but based on recent evidence, including microanatomical and histological analyses, we propose that conserved odontogenetic pathways most probably regulated the development of pseudodentition. The delayed pseudoteeth growth and epithelium keratinization allowed for the existence of a temporal window during which competent osteoblasts could respond to oral epithelial signaling, in place of the no longer present odontoblasts; thus, bony pseudoteeth developed instead of true teeth.

Structure and growth pattern of the bizarre hemispheric prominence on the rostrum of the fossil beaked whale Globicetus hiberus (Mammalia, Cetacea, Ziphiidae).

The rostrum of most ziphiids (beaked whales) displays bizarre swollen regions, accompanied with extreme hypermineralisation and an alteration of the collagenous mesh of the bone. The functional significance of this specialization remains obscure. With the voluminous and dense hemispheric excrescence protruding from the premaxillae, the recently described fossil ziphiid Globicetus hiberus is the most spectacular case.

Body location and tail regeneration effects on osteoderms morphology-are they useful tools for systematic, paleontology, and skeletochronology in diploglossine lizards (squamata, anguidae)?

Although diploglossine osteoderms were mentioned in several systematic and paleontological studies, their morphological variability in single specimens or within species remains paradoxically undescribed. This is mainly the effect of the lack of attention paid hitherto to the morphological and histological characteristics of the tail osteoderms. This study demonstrated that a previously undescribed morphological variability exists in these osteoderms, especially in those resulting from tail regeneration.

A quantitative assessment of bone area increase due to ornamentation in the Crocodylia.

Bone ornamentation, in the form of highly repetitive motives created by pits and ridges, is a frequent feature on vertebrate skull roofs and osteoderms. The functional significance of this character remains a matter of controversy and speculation. The many diverging hypotheses proposed to explain it all share a common logical prerequisite: bone ornamentation should increase significantly the surface area of the bones that bear it.

Fine-scale genetic analysis of the exploited Nile monitor (Varanus niloticus) in Sahelian Africa.

Background: Overexploitation of wildlife populations results in direct consequences, such as extinction and local extirpation, as well as indirect effects including genetic diversity loss and changes in genetic structure. A clear understanding of the underlying genetic patterns of harvested species is necessary for sustainable management. The Nile monitor (Varanus niloticus) is a commercially valuable species in the international leather industry, with the highest levels of exploitation concentrated throughout Sahelian Africa.

Structure and growth pattern of pseudoteeth in Pelagornis mauretanicus (Aves, Odontopterygiformes, Pelagornithidae).

The extinct Odontopterygiformes are the sole birds known to possess strong and sharp bony pseudoteeth, the shape and location of which are closely mimetic of real teeth. The structure of the pseudoteeth is investigated here in a late Pliocene/early Pleistocene species, Pelagornis mauretanicus, using X-ray microtomography and thin sections. The results are interpreted with regard to the pseudotooth mode of growth, and have implications concerning aspects of Pelagornis ecology.

Inner architecture of vertebral centra in terrestrial and aquatic mammals: a two-dimensional comparative study.

Inner vertebral architecture is poorly known, except in human and laboratory animals. In order to document this topic at a broad comparative level, a 2D-histomorphometric study of vertebral centra was conducted in a sample of 98 therian mammal species, spanning most of the size range and representing the main locomotor adaptations known in therian taxa. Eleven variables relative to the development and geometry of trabecular networks were extracted from CT scan mid-sagittal sections.

Experimental exposure of juvenile savannah monitors (Varanus exanthematicus) to an environmentally relevant mixture of three contaminants: effects and accumulation in tissues.

Using varanids as indicators of pollution in African continental wetlands was previously proposed. The present study aimed at understanding experimentally how monitors absorb and accumulate pollutants and how they are affected. The relevance of non-destructive sampling was also evaluated.

Assessing environmental contamination around obsolete pesticide stockpiles in West Africa: using the Nile monitor (Varanus niloticus) as a sentinel species.

Environmental contamination caused by obsolete pesticide stocks was assessed using the Nile monitor (Varanus niloticus) as a sentinel species. Organochlorines and organophosphates were quantified by gas chromatography in abdominal fat and the liver, respectively. Results were compared to those obtained from three other sites, characterized by different histories of contamination.

The Nile monitor (Varanus niloticus; Squamata: Varanidae) as a sentinel species for lead and cadmium contamination in sub-Saharan wetlands.

Wetland pollution is a matter of concern in sub-Saharan Africa. Though regularly exploited, the Nile monitor (Varanus niloticus), a large amphibious lizard, is not threatened. This work aims at assessing the value of this varanid as a sentinel species in surveys of environmental contamination by metals.

Vertebral microanatomy in squamates: structure, growth and ecological correlates.

The histological study of vertebrae in extant squamates shows that the internal vertebral structure in this group differs from that of other tetrapods. Squamate vertebrae are lightly built and basically composed of two roughly concentric osseous tubes--one surrounding the neural canal and the other constituting the peripheral cortex of the vertebra--connected by few thin trabeculae. This structure, which characteristically evokes that of a tubular bone, results from a peculiar remodelling process characterised by an imbalance between local bone resorption and redeposition; in both periosteal and endosteo-endochondral territories, bone is extensively resorbed but not reconstructed in the same proportion by secondary deposits.

The histological structure of glyptosaurine osteoderms (Squamata: Anguidae), and the problem of osteoderm development in squamates.

Glyptosaurinae, a fossil clade of anguid lizards, possess robust osteoderms, with granular ornamentation. In this study, the structural and histological features of these osteoderms were described in order to reconstruct their developmental pattern and further document the degree of homology that could exist between vertebrate integumentary skeletons. Glyptosaurine osteoderms have a diploe architecture and display an unusually complex structure that includes four tissue types: a core of woven-fibered bone intensely remodeled; a peripheral formation of the same tissue containing dense bundles of long Sharpey fibers; a thick basal layer of lamellar bone; and a superficial layer of a non-osseous material that belongs to the category of hypermineralized tissues such as ganoine, or enameloid and enamel tissues.

Bone vascular supply in monitor lizards (Squamata: Varanidae): influence of size, growth, and phylogeny.

Bone vascular canals occur irregularly in tetrapods; however, the reason why a species has or lacks bone canals remains poorly understood. Basically, this feature could depend on phylogenetic history, or result from diverse causes, especially cortical accretion rate. The Varanidae, a monophyletic clade that includes species with impressive size differences but similar morphologies, is an excellent model for this question.