Early morphological studies regarding the evolutionary history of elasmobranchs suggested sharks and batoids (skates and rays) were respectively monophyletic. More modern morphological cladistic studies, however, have tended to suggest that batoids are derived sharks, closely related to sawsharks and angelsharks, a phylogenetic arrangement known as the Hypnosqualea hypothesis. Very few molecula...

AIM To apply dual-source multidetector computed tomography (DSCT) scanning technology in conjunction with computationally assisted segmentation in order to explore and document skeletal variation that has occurred over the course of evolution. METHODS We examined 4 divergent species of elasmobranchs with high-resolution 3rd generation DSCT. The formalin prepared species examined were: Aptycho...

Multi-species groups are potentially mutualistic interactions that have garnered relatively little scientific attention. This study examines three batoids (skates and rays), Dasyatis thetidis, Pastinachus sephen, and Rhinobatos typus that regularly form resting aggregations in the intertidal sand flats of Heron Island, Australia. The defensive role of these aggregations is assessed with the aim...

Newly discovered fossils from the Silurian and Devonian periods are beginning to challenge embedded perceptions about the origin and early diversification of jawed vertebrates (gnathostomes). Nevertheless, an explicit cladistic framework for the relationships of these fossils relative to the principal crown lineages of the jawed vertebrates (osteichthyans: bony fishes and tetrapods; chondrichth...

Meeting the challenge of sampling an ancient aquatic landscape by the early vertebrates was crucial to their survival and would establish a retinal bauplan to be used by all subsequent vertebrate descendents. Image-forming eyes were under tremendous selection pressure and the ability to identify suitable prey and detect potential predators was thought to be one of the major drivers of speciatio...

Chondrichthyes, which include Elasmobranchii (sharks and batoids) and Holocephali (chimaeras), are a relatively small group in the Mediterranean Sea (89 species) playing a key role in the ecosystems where they are found. At present, many species of this group are threatened as a result of anthropogenic effects, including fishing activity. Knowledge of the spatial distribution of these species i...

An analysis on the species richness distribution of marine sharks and batoids for Colombian Caribbean Pacific regions was carried out. A total 138 documented in nearby waters off Colombia, including 76 62 batoids; 20 occurred both coasts with generally having a higher observed than Pacific. The had high values insular as well northern region. However, highest per spatial unit islands Gorgona Ma...

The shapes of vertebrate teeth are often used as hallmarks of diet. Here, however, we demonstrate evidence of frequent piscivory by cartilaginous fishes with pebble-like teeth that are typically associated with durophagy, the eating of hard-shelled prey. High-resolution micro-computed tomography observation of a jaw specimen from one batoid species and visual investigation of those of two addit...

Elasmobranchs are one of the most diverse groups in the marine realm represented by 18 orders, 55 families and about 1200 species reported, but also one of the most vulnerable to exploitation and to climate change. Phylogenetic relationships among main orders have been controversial since the emergence of the Hypnosqualean hypothesis by Shirai (1992) that considered batoids as a sister group of...