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Myxozoa represent a diverse group of microscopic cnidarian endoparasites alternating between invertebrate and vertebrate hosts. Of the approximately 2,600 species described predominantly from teleost fish, only 1.8% have been reported from cartilaginous fishes (Elasmobranchii). As ancestral vertebrate hosts of myxozoans, elasmobranchs may have played an important role in myxozoan evolution, however, they are also some of the largest vertebrate hosts known for this group of parasites. We screened 50 elasmobranchs belonging to nine species and seven families, from various geographical areas, for myxozoan infection. We found a 22% overall prevalence of myxozoans in elasmobranchs and describe five species new to science. We investigated, for the first known time, the evolution of spore size within three phylogenetic clades, Ceratomyxa, Sphaerospora sensu stricto and Parvicapsula. We found that spores from elasmobranch-infecting myxozoans were on average 4.8× (Ceratomyxa), 2.2× (Parvicapsula clade) and 1.8× (Sphaerospora sensu stricto except polysporoplasmic Sphaerospora spp.) larger than those from teleosts. In all analysed clades, spore size was correlated with phylogenetic position. In ceratomyxids, it was further strongly positively correlated with fish body size and habitat depth, independent of cellular composition of the spores and phylogenetic position in the tree. While in macroparasites a host size-correlated increase in parasite size occurs on a large scale and is often related to improved exploitation of host resources, in microscopic parasites size ranges vary at the scale of a few micrometres, disproportionate to the available additional space in a large host. We discuss the ecological role of these changes with regard to transmission under high pressure and an invertebrate fauna that is adapted to deeper marine habitats.

We present comparative analysis of the micro- and macro-morphology of the olfactory organ of six neoselachians living in different habitats: two freshwater benthopelagic batoids, Potamotrygon motoro and Potamotrygon hystrix (Potamotrygonidae) as well as four species of sharks occupying the outer continental shelves and upper slopes Mustelus mustelus (Trikidae) and Scyliorhinus canicula (Scyliorhinidae), and deep-water Galeus melastomus (Scyliorhinidae) and Etmopterus spinax (Etmopteridae). Our research used light and electron (TEM, SEM) microscopes as well as macroscopic observations. The position of the nostrils in relation to the mouth varied in these species but all of them possessed elongate olfactory rosettes with primary lamellae arranged over two rows. The types of primary lamellae were distinguished based on their arrangement on the opposite sides of the median raphe as well as morphology of secondary lamellae and distribution of sensory and non-sensory regions of olfactory epithelium lining the lamellae; these were different between batoids and sharks. Analysis of olfactory epithelium revealed the presence of microvillous olfactory sensory neurons as the only type of receptor cells in all studied species whereas ionocytes were recognized only in sharks. All species possessed one type of goblet cells (Alcian Blue or Periodic Acid Schiff positives) except for P. motoro in which both types of goblet cells were present. Moreover, apical parts of non-sensory microvillous cells that lined the basal parts of the primary lamellae, possessed PAS-positive mucous granules; these were present in both species of batoids. This analogous region was abundant in goblet cells in the species of sharks studied here. Results indicated that differences between freshwater and marine species as well as between marine species occupying various habitat zones include mainly nostrils position, density of occurrence of ionocytes and goblet cells within olfactory epithelium as well as biochemical character of mucus.

Malformations are common in trilobites, but the majority of described specimens are from Europe and North America. Only a few abnormal trilobites have been reported from China. Ten abnormal trilobites from Cambrian, Ordovician and Silurian strata in central and eastern China are documented. The abnormal Ordovician trilobites are found for the first time in China. All malformations occur in the thoraxes and pygidia, and were caused by a sub-lethal predatory attack, genetic or embryological malfunction, or injury sustained during molting. It is difficult to identify the predators of the six injured trilobites, but potential predators include Cambrian non-trilobite arthropods, Ordovician cephalopods, and Silurian eurypterids, chondrichthyes or cephalopods, even cannibalistic trilobites. Abnormal specimens caused by sub-lethal predatory attacks mainly occur in Cambrian strata in China and other areas in the world, and are very rare in post-Cambrian strata. This pattern may reflect the rise of predators and increased predation in the post-Cambrian, which led to an increased trilobite fatality rate, thus reducing the probability that injured specimens would become fossilized.

The visual sense of elasmobranch fishes is poorly studied compared to their bony cousins, the teleosts. Nevertheless, the elasmobranch eye features numerous specialisations that have no doubt facilitated the diversification and evolutionary success of this fascinating taxon. In this review, I highlight recent discoveries on the nature and phylogenetic distribution of visual pigments in sharks and rays. Whereas most rays appear to be cone dichromats, all sharks studied to date are cone monochromats and, as a group, have likely abandoned colour vision on multiple occasions. This situation in sharks mirrors that seen in other large marine predators, the pinnipeds and cetaceans, which leads us to reassess the costs and benefits of multiple cone pigments and wavelength discrimination in the marine environment.

In a seminal study on elasmobranch systematics, Maisey proposed the monophyly of a large lineage of sharks based primarily on the sharing of an orbitostylic jaw suspension. This group was later redefined as the Squalomorphi, which included Squatinidae but not Batoidea. Subsequent morphological analyses, however, rejected Maisey’s scheme, which was left aside for nearly two decades until the first molecular phylogenies began to cluster again the orbitostylic sharks into a monophyletic group. In a broad comparative investigation of the anatomy of the appendicular skeleton of cartilaginous fishes, we discovered new evidence supporting the monophyly of squalomorph sharks: the presence of a posterior process at the lateral region of the coracoid bar serving as a origin site for the depressor pectoralis II muscle. This feature would be the first strong morphological evidence in 40 years potentially supporting the monophyly of Squalomorphi.

Two surveys using a combination of midwater trawl and acoustics were undertaken in October 2014 and June 2015 to investigate species composition and biomass density of mesopelagic nekton over the continental slope of the South China Sea (CSSCS). In two surveys, diversity and dominant species of nektons (Chondrichthyes, Osteichthyes and Cephalopoda) showed obviously diel and depth–dependent difference. In 2014, in general species richness and diversity of nektons in the 0–100 m at night were greater than that in the 350–650 m during the day and 350–650 m at night. In Jun. 2015, species richness and diversity of nektons in the 350–650 m during the day were much greater than that in the 350–650 m at night and 0–100 m at night. Myctophidae and Diaphus are the most common fishes in the CSSCS mesopelagic zone. Jellyfishes could cause the nautical area scattering coefficient (NASC) to increase, but the effect of jellyfishes on NASC could vary over the light–night cycle and trawl depth. Catch rates of different nektonic categories varied by time of day and depth. Night–time catch rate at trawl depths

A new species of “guitarfish" from the Lower Cretaceous Tlayua Formation of Puebla, Mexico is here described as †Tlalocbatos applegatei gen. et sp. nov. The new species is based on a nearly complete articulated specimen and represents the first chondrichthyan from this formation. The inclusion of a new character and two additional taxa into a phylogenetic analysis based on previous studies generates a novel phylogenetic hypothesis of batoid phylogeny. Paraphyly of the “guitarfishes” is corroborated, although a new clade was recovered comprising the modern Platyrhinidae plus †Britobatos primarmatus as the sister group of the node formed by †Stahlraja, †Tlalocbatos, plus the Trygonorrhinidae. †Tlalocbatus differs from other batoids by the following combination of characters: nasal capsules with horn-like anterior processes; homodont dentition; presence of a well-developed median uvula; lateral uvulae not differentiated; pectoral propterygium, extending as far as the anterior part of the nasal capsules; two radials articulating directly with the scapulocoracoid, between the mesopterygium and the metapterygium; two dorso-lateral nuchal cartilages, unfused with the synarcual; and an elevated number of post-synarcual centra (115–118). The distribution of †Stahlraja (†Tlalocbatos (trygonorrhinids)), suggests that this clade originated in the western part of the Tethys-Caribbean region with a later dispersion westward towards the Pacific.

While post-release mortality estimates have been conducted on a range of shark species, the short-term sub-lethal effects of capture, handling and release are poorly known and have been mostly investigated in controlled conditions. In addition, the widely accepted notion that immediate post-release active swimming is an indicator of shark condition has never been tested. This study assessed the effects of deck exposure by analysing post-release behaviour of two species of shark, the draughtboard ( Cephaloscyllium laticeps) and the piked spurdog ( Squalus megalops ) in-situ using a remote-operated-vehicle and in a replicated experiment in controlled conditions. In total, 67 sharks were caught with demersal fish trawls and commercial longlines and subjected to different deck exposures and release environments. Tailbeat rates of deck-exposed sharks were significantly lower than the control sharks, but this effect differed between in-situ and experimental environments. Results indicate that capture has species-specific effects, that post-release effects may last longer than 5 min, and that controlled experiments may not be reliable indicators of post-release effects. Immediate post-release swimming was not a good predictor of post-release behaviour, suggesting capture and release fisheries may have significant sub-lethal effects on some species of shark, and that limiting capture or handling time may reduce post-release effects.

This study reports the first occurrence of a varied xenacanth assemblage from the Upper Triassic Tiki Formation of India, based on multiple well-preserved isolated teeth. Based on distinct tooth morphology, two species of the genus Mooreodontus are described: M. indicus and a new species, M. jaini. The new species is diagnosed based on a tricuspid crown containing two stout, slightly diverging lateral cusps pointing in the same direction, a high median cusp, crown-base angle almost at 90°, large, rounded, apical button with several foramina and multiple, 8–9 coarse vertical cristae on all the cusps. Dental anomaly in the form of a partial quadri-cuspidate xenacanthid tooth is present in the collection. Another group of xenacanthid teeth have bicuspid crowns with two upright, asymmetric cusps, where the mesial cusp is thicker than the distal one, and consistently lack a median cusp. Such distinct bicuspid tooth morphology is usually present in Palaeozoic forms and is reported for the first time from the Late Triassic. It is considered to belong to a new taxon, Tikiodontus asymmetricus nov. gen., nov. sp., of indeterminate family. Distinctive tooth histology also differentiates the two Indian genera Mooreodontus and Tikiodontus nov. gen. from other xenacanthid taxa. In addition, the Tiki assemblage has yielded multiple chondrichthyan dermal denticles, which may be subdivided into two morphotypes based on their robustness and presence/absence of linear ridges on the fused cusps. India holds a unique position in terms of its Late Triassic freshwater shark fauna, as it exhibits distinct Laurasian affinities. These freshwater sharks had restricted occurrences in other parts of the Gondwanan landmass.

Early Cretaceous elasmobranchs still are very insufficiently known despite all progress that has been accomplished in recent years. Here, a small elasmobranch assemblage is presented from the Valanginian of Austria that contributes significantly to a better understanding of early Cretaceous elasmobranch diversity. The new assemblage comprises two new carcharhiniform sharks, Altusmirus triquetrus gen. et sp. nov. and Fornicatus austriacus gen. et sp. nov., a new orectolobiform shark, Similiteroscyllium iniquus gen. et sp. nov., and a galeomorph shark tooth of uncertain affinities. The recent identification of Similiteroscyllium gen. nov. has shown that it has strong similarities with Ornatoscyllium rugasimulatum from the Lower Cretaceous of France. Significant differences of the tooth morphology of O. rugasimulatum and the type specimen O. freemani justify full reconsideration of the systematic position of O. rugasimulatum and require it to be reassigned to Similiteroscyllium gen. nov. described in this paper. The new assemblage described here, and those from the Valanginian of France and Poland comprising 30 additional taxa, indicates that Early Cretaceous elasmobranch diversity was significantly higher than previously assumed. Consequently, the supposed diversity decline of elasmobranchs across the Jurassic-Cretaceous boundary represents a collecting bias rather than a real pattern.

Rhaetian bone beds have been described from many locations in south-west England, around Bristol. One site that has never been reported is Stowey Quarry, some 13 km south of Bristol. This quarry yielded Lias, and revealed thin Rhaetian units in the quarry floor, including two bone beds, the basal Rhaetian bone bed, and a second, higher bone bed, also within the Westbury Formation. The fossil fauna of both includes elements typical of Rhaetian bone beds elsewhere, but showing differences in faunal composition between the two. The basal bone bed yielded more specimens and more species, with three taxa (Sargodon tomicus, Rhomphaiodon minor and Hybodus cloacinus) exclusive to this bed and eleven identified in total. Severnichthys acuminatus accounts for more than 50% of the countable teeth from the basal bone bed, followed by Gyrolepis albertii with 20%, Lissodus minimus with 14% and Rhomphaiodon minor with 9%. The basal bone bed, as ever, is dominated by chondrichthyans, whereas the upper bone bed is dominated by osteichthyans, which form 90% of the non-dental remains. The only unique taxon is Dapedium, and Gyrolepis albertii is the most abundant species with 45% of countable teeth, followed by Severnichthys acuminatus with 38% and Duffinselache holwellensis with 11%. These faunal differences, and the equally good condition of specimens between both samples confirms that the upper bone bed is independent of the basal bone bed, and is not a reworked subsample.

The material reported herein comes from the Lower Cretaceous Agrio Formation (Neuquén Basin, west-central Argentina). These fishes dwelled in a Pacific Ocean embayment in southwestern Gondwana before the establishment of the Andean Cordillera. The material consists of an incomplete dorsal fin spine of the widespread Hybodontoidea clade (from upper Valanginian beds) and a partial tooth of one of the earliest known lamniforms (from upper Hauterivian beds)., Facultad de Ciencias Naturales y Museo

The ichthyofauna of the Lower Cretaceous Quirico Formation (Sanfranciscana Basin), Minas Gerais, Brazil, comprises so far taxa like Hybodontiformes (Chondrichthyes), Dastilbe, Laeliichthys, Mawsonia, and isolated Amiidae teeth and Semionotiformes scales. Here we report new remains of a dipnoan tooth plate and its associated pterygopalatine and Lepisosteidae material comprising isolated scales, a hyoid arch, and a partially preserved individual including several scales, vertebrae, neural and haemal spines, pterygiophores, and associated anal fin. Although isolated or incomplete, these new fossils, collected from upper sandstone levels of fluvio-lacustrine deposits, increase the diversity of the ichthyofauna of the Quirico Formation. This discovery adds important information to the understanding of the relationships of Brazilian and African faunas during the initial stages of the opening of the Atlantic Ocean.

Fish are reported to exhibit chitinase activity in the stomach. Analyses of fish stomach chitinases have shown that these enzymes have the physiological function of degrading chitinous substances ingested as diets. Osteichthyes, a group that includes most of the fishes, have several chitinases in their stomachs. From a phylogenetic analysis of the chitinases of vertebrates, these particular molecules were classified into a fish-specific group and have different substrate specificities, suggesting that they can degrade ingested chitinous substances efficiently. On the other hand, it has been suggested that coelacanth (Sarcopterygii) and shark (Chondrichthyes) have a single chitinase enzyme in their stomachs, which shows multiple functions. This review focuses on recent research on the biochemistry of fish stomach chitinases.

Blood flukes (Aporocotylidae) of actinopterygians (bony fishes) have been shown to infect freshwater gastropods and marine polychaetes as intermediate hosts. However, no life cycle is known for any aporocotylid of chondrichthyans (cartilaginous fishes) and no adult aporocotylid has been linked to a cercaria infecting a bivalve. Here we report two novel infections that fill these gaps. Cercariae consistent with the family Aporocotylidae were found developing in sporocysts in the gonad of the surf pipi, Donax deltoides Lamarck, 1818 (Bivalvia: Donacidae), from Stockton Beach, central New South Wales, Australia. Adult aporocotylids were found in the heart of the giant shovelnose ray, Glaucostegus typus (Anonymous [Bennett], 1830), from Moreton Bay, southeastern Queensland, Australia. Phylogenetic analyses of the 28S rDNA region generated from the new specimens resulted in phylograms in which the two parasites form a strongly supported clade with Chimaerohemecus trondheimensis van der Land, 1967, the only aporocotylid known from a holocephalan and the only other chondrichthyan-infecting aporocotylid for which sequence data are available. Most marine aporocotylids of actinopterygians also form a strongly supported clade. These findings lead us to hypothesise that the aporocotylids of chondrichthyans are distinct from all other blood flukes in infecting bivalves as intermediate hosts. Putative cophyly between three major blood fluke clades and both definitive and intermediate host groups is consistent with diversification of the Schistosomatoidea over 400 million years ago. (C) 2017 Australian Society for Parasitology. Published by Elsevier Ltd. All rights reserved.

We describe isolated shark teeth collected from levels of the Calafate Formation at the SE coast of the Argentino Lake, Calafate city, Santa Cruz province, Argentina (Atlantic Ocean), and from the Algarrobo coast at the Valparaíso Region in central Chile (Pacific Ocean). The teeth belong to a new species of the echinorhiniform genus Echinorhinus. Echinorhinus maremagnum n. sp. was a taxon distributed in both the southwestern Atlantic and the southeastern Pacific. This new taxon constitutes the oldest record of echinorhiniforms from South America and one of the few Mesozoic records at a worldwide scale. Fil: Bogan, Sergio. Fundación de Historia Natural Félix de Azara; Argentina. Universidad Maimónides; Argentina Fil: Agnolin, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina. Fundación de Historia Natural Félix de Azara; Argentina. Universidad Maimónides; Argentina Fil: Otero, Rodrigo A.. Universidad de Chile; Chile Fil: Brissón Egli, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina Fil: Suárez, Mario E.. Universidad de Chile; Chile Fil: Soto Acuña, Sergio. Universidad de Chile; Chile Fil: Novas, Fernando Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina

The very small teeth of a new petalodont chondrichthyan are described from the Lower Carboniferous Eyam Limestone Formation (Peak Limestone Group, Carboniferous Limestone Supergroup; Brigantian, Early Carboniferous) of Derbyshire. Cypripediodens cristatus gen. et sp. nov. belongs to the Family Janassidae on the basis of the angle formed between the base and the crown. Presumed lower symphyseal teeth are Fissodus -like, possessing two labial cusps, whilst the rest of the dentition is relatively homodont. Individual crowns measure up to 1.3 mm labiolingually and possess a single labial cusp with virtually circular cross-section, separated from a prominent lingual cusp with circumferential cristae from which it is separated by a central trough.

Fish remains from over 100 localities in the Upper Silurian to Lower Devonian (traditional Lower Old Red Sandstone: LORS: Přidoli–Pragian) of Wales and the Welsh Borderland Anglo-Welsh Basin, southwest Britain have been investigated. Work on microfossils of fish (‘microvertebrates’, generally

Mediterranean young-fish oriented experimental bottom trawl surveys represent a precious source of information on both past and current standing stocks and their life history traits and exploitation state. In the present note, taking the occasion of the same vessel employed in the South of Sicily (Central Mediterranean), an indirect approach has been implemented to compare MEDITS (Mediterranean International Bottom Trawl Survey) and GRUND (Gruppo Nazionale Demersali) abundance and biological features of the blackmouth catshark Galeus melastomus Rafinesque, 1810 to highlight gear and season effects if any. Data were gathered between 1994 and 2006, in spring-summer (MEDITS) and autumn (GRUND). The density and biomass indexes and occurrences were substantially lower in spring than in autumn. On the contrary, the biological traits were more similar, although significant differences were detected in the length frequency distribution. The homogeneity of life traits between seasons and the critical features showed in this study demonstrate that an annual experimental trawl survey can be enough to monitor G. melastomus. Similar analysis could be useful to highlight seasonal and gear effects on the other demersal stocks to better figure out limits and possibility of Mediterranean young-fish oriented experimental bottom trawl surveys data.

Intensive sampling for vertebrate microfossils has yielded abundant fish remains in the Maastrichtian units of the Tremp Formation (southern Pyrenees, Catalonia, Spain). Samples were taken from eight new sites representing different palaeoenvironments including coastal wetlands and floodplains, in order to assess the fish diversity and to gain a better understanding of the last dinosaur-dominated ecosystems of northeastern Spain. The results suggest that a diverse ichthyofauna inhabited these transitional to inland fluvial settings throughout the Maastrichtian, comprising both marine and freshwater taxa. Three different chondrichthyans, eight basal neopterygians and at least seven teleostean species were found, the latter being more diverse than in other Maastrichtian localities in Europe. Fossil evidence from the studied late Maastrichtian assemblages suggests that teleosteans were present in all the trophic guilds. In addition, the oldest records for osteoglossids and perciforms in Europe, as well as for cypriniforms worldwide, are reported here. The findings from the southern Pyrenees also reveal ichthyofaunal turnover during the Late Cretaceous, with ‘holosteans’ being replaced by teleosteans. Moreover, Maastrichtian ichthyofaunas from the southern Pyrenees show Asian and North American biogeographical affinities.

We previously reported that the polysaccharide chitin, a key component of arthropod exoskeletons and fungal cell walls, is endogenously produced by fishes and amphibians in spite of the widely held view that it was not synthesized by vertebrates [1]. Genes encoding chitin synthase enzymes were found in the genomes of a number of fishes and amphibians and shown to be correspondingly expressed at the sites where chitin was localized [1,2]. In this report, we present evidence suggesting that chitin is prevalent within the specialized electrosensory organs of cartilaginous fishes (Chondrichthyes). These organs, the Ampullae of Lorenzini (AoL), are widely distributed and comprise a series of gel-filled canals emanating from pores in the skin (Figure 1A). The canals extend into bulbous structures called alveoli that contain sensory cells capable of detecting subtle changes in electric fields (Figure 1B) [3,4]. The findings described here extend the number of vertebrate taxa where endogenous chitin production has been detected and raise questions regarding chitin's potential function in chondrichthyan fishes and other aquatic vertebrates.

This paper aimed to study and compare the hematology of newborns, young, subadults, adult males, adult females and pregnant females of Potamotrygon wallacei (cururu stingray), Potamotrygon motoro and Paratrygon aiereba. Newborn cururu stingrays had lower red blood parameters than those of other development stages. Thrombograms and leukograms showed a conservative pattern between development stage, sexual dimorphism and pregnancy. In P. motoro and P. aiereba, variables relating to red blood parameters, biochemistry and leukograms showed little variation between the species' biological characteristics, thus showing that these variables are not good criteria for differentiating them within the same species. In conclusion, the development stage is an important factor for differentiating hematological properties in the cururu stingray, while this has not been observed in P. motoro and P. aiereba stingrays.

The Roughskin Dogfish Centroscymnus owstonii is a poorly known species with eventual records along the Western South Atlantic. Different dermal denticles have been historically reported for juveniles and adults, which presupposes changes from a juvenile denticle type to an adult denticle type during growth. The present study was based on a male neonate 324 mm in total length (TL) captured with crab pots on the northeastern continental slope of Brazil, between 400–450 meters. This was considered a newborn based on its small size, very similar to previously reported large embryo dimensions and close to the expected birth size in literature. Three different dermal denticles were observed, alternating from the rostrum to the branchial slits, where a tricuspidated denticle type extended covering the rest of the posterior portion of the body. Dermal denticle types and distribution suggest that the replacement process of dermal denticles begins before birth or early after birth, undergoing at least three changes until reaching the adult dermal denticle type. These different types may be related to uterine epithelial histotroph absorption or embryo movement within the mucous environment, which would be enhanced by largely spaced denticles. The reported fragmented distribution of this species along the Brazilian coast is probably related to insufficient sampling coverage.

Sharks and their relatives (Chondrichthyes) were an important food source for pre-European Māori. However, their skeletons, which are largely comprised of cartilage, are poorly preserved in the archaeological record, with only teeth and vertebrae routinely recorded. Furthermore, it is often difficult to identify Chondrichthyes by their vertebral morphology. Here we compare the morphological and ancient DNA identification of 180 Chondrichthyes vertebrae representing seven different morphotypes sampled from a large archaeological assemblage in Auckland, New Zealand. aDNA sequences were obtained from 87 vertebrae and indicated the presence of four Chondrichthyes species at the site: rig (Mustelus lenticulatus), school shark (Galeorhinus galeus), bronze whaler (Carcharhinus brachyurus) and New Zealand eagle ray (Myliobatis tenuicaudatus). The aDNA results indicated several instances where morphological identification of vertebrae had been incorrect, including the most common taxon found in the assemblage, rig, which had been identified morphologically as school shark. Overall, our results indicated that aDNA analysis of Chondrichthyes vertebrae is a valuable tool to distinguish between specimens with morphologically similar vertebrae and to verify morphological identifications.

The maintenance of natural capital and the stability of regulation services of marine ecosystems has proved to be linked to the conservation of key species supporting the ecosystems function. Chondrichthyes are key top-predators and their removal from marine ecosystems due to fishing exploitation could lead to changes in species interactions and biomass that can negatively influence the provision of ecosystems services. The ecological role of the demersal Chondrichthyes living in the marine food web of the Calabrian area in the Northern Ionian Sea (Central Mediterranean Sea) was analysed by means of ecological indicators derived from Ecopath mass-balance food web models estimated in their stationary states during the periods 1995–1997, 2003–2005 and 2013–2015. The trophic web model was described by 57 functional groups (7 of which representing the demersal Chondrichthyes), which were described by their Biomass (t/km2), Production and Consumption rate, Diet, Landings (t/km2) e Discards (t/km2). Remarkable changes in biomass were recorded for shark and rays, as a consequence of changes in fishing patterns and oceanographic regime shift named Bimodal Oscillating Systems (BiOS). Demersal Chondrichthyes occupy high trophic positions in the Calabria food web showing trophic levels higher than 4.1, with the D. licha identified as the main apex predators, while E. spinax and G. melastomus as meso‑predators. The pattern of the consumption flows highlighted a potential sensitivity of E. spinax and G. melastomus to the changes in deep waters circulation caused by the BiOS acting on the entire ecosystem of the Ionian Sea. D. licha was identified as the main keystone predators in all the investigated periods. The analysis of the trophic indirect and direct impacts shows the role of the demersal Chondrichthyes as beneficial predators, with positive effects on several preys. Results also showed that G. melastomus and the Shelf Elasmobranchs group (e.g. Raja asterias, Mustelus mustelus, etc.…) were overexploited in 1995 and that all groups of sharks and rays underwent to a decrease of exploitation rate over time. Chondrichthyes showed medium-low values of overlap with the fishing gears (

The daggernose shark, Isogomphodon oxyrhynchus is endemic to the northern of South America from Trinidad and Tobago to Tubarao bay in Maranhao state (Brazil) where collapsed since the 1990’s, due to several gillnet fisheries for teleost fishes, fisheries targeting sharks, including the daggernose shark, itself, and trawling for shrimp. Based on gillnets with meshes 80– > 200 mm, we analyzed the intrinsic and extrinsic vulnerabilities of the species through different scenarios investigating the species’ resilience. Samples were collected from December 1989 to September 1991, off the coast of Maranhao. Mortalities were M = 0.188 and Z = 0.653 for males and 0.725 in females. Only a scenario without fishing allowed for the population to remain in equilibrium. The survival of young specimens between 1 to 6 years was critical to sustainability according to elasticities that exceeded 70%. The intrinsic rebound ( r z ) of 0.039, demonstrated the species low resilience. An unsustainable exploitation was revealed for different ages at first capture ( t c ) when the maximal yield per recruit ( YPR ) provided F m a x (0.15), below the actual F = 0.47 in 1991 when an exploitation rate E = 0.72 was obtained. Using data collected in 1980/1990 the species was globally categorized in 2006 as critically endangered (CR) similar to assessments in Brazil in 2004. After a three-generation period the species, which did not recover, is now collapsed matching the predicted quasi-extinction condition which claims for urgent and effective conservation measures.

Fatty acid (FA) analysis can provide an effective, non-lethal method of elucidating the trophic ecology of fish. One method utilised in the field is to collect biopsied muscle tissue, but this can be problematic in live sharks due to a thick dermal layer with extensive connective tissue. The aim of this research was to determine whether fin and muscle tissue yield similar FA profiles in three species of tropical euryhaline sharks: Carcharhinus leucas, Glyphis garricki and Glyphis glyphis. Fatty acid profiles were detectable in fin clips as small as 20 mg (~ 5 mm × 6 mm) and muscle biopsies > 10 mg mass. Overall profiles in relative (%) FA composition varied significantly between fin and muscle tissues for C. leucas and G. garricki (global R-values = 0.204 and 0.195, P

Microvertebrates are common in the basal bone bed of the Westbury Formation of England, documenting a fauna dominated by fishes that existed at the time of the Rhaetian Transgression, some 206 Myr ago. Two sites near Chipping Sodbury, south Gloucestershire, Barnhill Quarry and Chipping Sodbury railway cutting, show differing faunas. Top predators are the large bony fish Severnichthys and the shark Hybodus cloacinus, which preyed on smaller sharks such as Lissodus and Rhomphaiodon. These fishes in turn may have fed on a mixed diet of other fishes and invertebrates, and Lissodus was a shell crusher. Comparisons of these faunas with others described recently from the Bristol region, and from Devon, indicate remarkable faunal similarities in the Rhaetian basal Westbury Formation bone bed over a wide area, based on a variety of ecological statistics that document species diversities and relative abundances. Only the fauna from the Chipping Sodbury railway cutting differs significantly.

Due to an incomplete fossil record, little is known about lamniform shark life history from the Early Cretaceous of North America. Recent discoveries have shown that during this time, some lamniformes reached gigantic sizes (>6–8 m in total length) not seen in earlier species. Given the importance of life history to understand how organisms reach such sizes, we conducted an ontogenetic analysis on three very large shark vertebrae, representing a single individual from the Lower Cretaceous (Albian) Duck Creek Formation of Texas. Using three different techniques (computed tomography, histological sectioning, and surface texture analysis), we were able to show that this individual was born at a relatively small size and subsequently grew at rapid rate, achieving a total length of over 6.3 m in approximately 18 years; a rate not observed in any other Cretaceous species. Comparison of the different aging techniques yielded complementary results; however, surface texture analysis produced the most complete ontogenetic record for this specimen. More work is needed to determine broad patterns in the life history evolution of giant Early Cretaceous lamniform sharks.

The recently described Squalus albicaudus is a mesopredator shark and, as such, exposed to mercury biomagnification processes. Therefore, this study aimed to assess total Hg (THg) concentrations in S. albicaudus, a deep-water species, sampled off Southeastern Brazil and discuss ecological, reproductive, human consumption and conservation implications. Thirty-two individuals were sampled off the coast of Rio de Janeiro, including 13 gravid females carrying 34 embryos. Muscle THg concentrations were higher in all sex classes compared to liver, gonads and brain. The last three, in turn, presented THg concentrations above toxic biota thresholds. Significant correlations were observed between muscle and brain and liver, indicating systemic Hg contamination and inter-organ transport and distribution. In addition, correlations observed between organs strongly support efficient Hg blood-brain barrier crossing and maternal transfer. Maternal THg transfer was observed, with embryo THg also above toxic thresholds for fish. THg levels in muscle and liver, as well as embryos, were higher compared to other Squalus species worldwide. Hg contamination off the coast of Rio de Janeiro is of significant concern and should be further assessed. Potential human consumption risks are noted, as muscle THg concentrations were above maximum permissible levels set by regulatory agencies.

Schroederichthys saurisqualus is a small shark endemic to the southwestern Atlantic, with known distribution on the upper continental slope of southern Brazil, ranging between 122 and 435 m in depth, where it is a trawling bycatch component. In the present study, 124 S. saurisqualus specimens collected between 280 and 500 m in depth from September to October 2002 were analyzed concerning reproductive and feeding aspects. Specimen sizes ranged from 252 to 610 mm total length (TL) for males and 280 to 602 mm TL for females. All males larger than 550 mm TL presented calcified claspers, while seven females (524 to 602 mm TL) presented forming eggs. The data reported herein indicate a first maturity size of about 500 mm TL for both males and females. Stomach content analysis identified the squid Illex argentinus as the most frequent prey, observed in 76.86% of the examined stomachs. The results indicate that S. saurisqualus displays a mate-finding strategy during the reproductive season, when squid predation ocurrs. However, this behavior puts this small catshark population in a vulnerable situation, since intense squid trawling activities are noted during the same period in the same area, exposing the local juvenile S. saurisqualus population to higher fishing pressures.

Chondrichthyan species are considered highly susceptible to fishing activities and as “indicator species” for overfishing and ecosystem stability. In European waters, chondrichthyes have become a focus of conservation actions due to the abundance declines of several species. In the present study, fishery independent data obtained from the Mediterranean International Trawl Surveys (MEDITS) in the Aegean and E. Ionian Seas (eastern Mediterranean) were coupled with bottom trawl fishing effort data obtained from vessel monitoring systems (VMS) in order to evaluate the effect of fishing on biomass variations of demersal chondrichthyan species. The study focused on commonly captured species such as Raja clavata, Galeus melastomus, Scyliorhinus canicula and Squalus spp, as well as to the total chondrichthyan biomass. The effect of fishing effort on biomass indices, expressed in terms of kg per square km of swept area, was examined by means of Generalized Additive Model techniques, using also the sampling position, year and depth as co-variates. Overall findings suggested a biomass decline of chondrichthyan species with increasing fishing effort. Nevertheless, it was also found that certain species (e.g G. melastomus in both areas and S. canicula in the Aegean Sea) can withstand fishing pressure and it is likely that discard survival rates, depth preferences and fisheries exploitation patterns, are the main drivers explaining variations regarding the impact of fishing on the different stocks.

The early Miocene is characterized by warm conditions until the middle Miocene when temperatures dropped significantly. The presence of tropical to subtropical invertebrate faunas in early Miocene sediments of Chile supports the hypothesis of warm temperatures. The Neogene fossil record of chondrichthyans (holocephalans, sharks, rays and skates) has been well established for Chile. However, most studies focused on middle Miocene to Pliocene records, whereas early Miocene chondrichthyans have been rather poorly investigated up to now. The aim of this study is to describe early Miocene chondrichthyans from Chile and to discuss their paleobiogeographic and ecological implications. Here, we report seventeen chondrichthyan taxa from the early Miocene of Chile. The fauna includes the first fossil record of Mustelus from the Pacific coast of South America, the first oral tooth of Pristiophorus humboldti nov. sp. from the Neogene of South America and the first fossil record of Alopias from the Neogene of Chile. We are able to increase the total number of taxa from the early Miocene of Chile from 13 to 21. Faunal shifts in the marine waters of Chile between the early Miocene and the present reveal different biogeographical dynamics: three taxa decreased their southern latitudinal range, seven increased their southern latitudinal range, six went globally extinct and one went regionally extinct. The extinction and latitudinal changes observed in chondrichthyans can be best explained by climatic fluctuations during the Neogene and Holocene along the Pacific coast of South America. However, studies to evaluate the effect of ecological traits should be considered in the future.

This article will review current knowledge on CXCR in fish, that represent three distinct vertebrate groups: Agnatha (jawless fishes), Chondrichthyes (cartilaginous fishes) and Osteichthyes (bony fishes). With the sequencing of many fish genomes, information on CXCR in these species in particular has expanded considerably. In mammals, 6 CXCRs have been described, and their homologues will be initially reviewed before considering a number of atypical CXCRs and a discussion of CXCR evolution.

INTRODUCTION ach year, millions pursue work and leisure activities in the ocean. Thousands of people Eunknowingly step into the ocean for wading or swimming and receive a barbed sting from a normally docile, frightened stingray. This wellcamouflaged creature from the Chondrichthyes class, which includes sharks and skates, lives in temperate oceans around the world. Stingrays are also found in freshwater river systems. In the coastal waters of the United States there are approximately 11 species of stingrays and about 150 worldwide, which are divided into 2 superfamilies, the Dasytoidea, or true stingrays, and the Myliobatoidea. Their sizes range from the size one’s palm to 6.5 feet (2 meters) and weigh up to 800 pounds (350 kg). The longer the stingray spine and the more distally located the spine is on the whiplike tail, the greater the danger to humans from stingray spine injuries. Stingrays are not to be confused with the Manta Ray, which is harmless and does not have a barbed tail. Of these 2 families, the majority of venomous marine stings are from 2 species. From the West Coast there is the Urolophus halleri, also commonly known as the round stingray, with an average length of up to 24 inches, and along the South-East coast there is the southern stingray, Dasyatis Americana, with lengths up to 79 inches. Scuba divers and snorkelers are fortunate when they come across the beautiful stingray. This creature is easily identifiable as it glides through the water while gently moving its dorsoventrally flattened body to feed on shrimp and small fish. Well adapted to its habitat, the stingray can blend easily into the sand. When the stingray is stepped on or encounters danger, it raises its tail, and “strikes” with its sharp pointed spine. This spine is composed of a bonelike cartilaginous material with unique histologic architecture and a venom-delivery system that can be seen on X-ray (Figure 1). On the underside of the spine are venom-secreting glandular cells. The stingray’s sheath covering breaks apart as it enters the

The Rhaetic Transgression, 210 Myr ago, which marked the end of continental conditions in the European Triassic, and the arrival of marine deposition, may have been heralded by the arrival of burrowing shrimps. Here we document an unusual taphonomic situation, in which classic basal Rhaetic bone bed is preserved inside a Thalassinoides burrow system at the base of the Westbury Mudstone Formation, in the highest part of the Blue Anchor Formation, at Charton Bay, Devon, UK. The fauna comprises four species of sharks and five species of bony fishes. The sharks, Rhomphaiodon (‘ Hybodus ’), Duffinselache , Lissodus , and Pseudocetorhinus are small, and include predatory and crushing/opportunistic feeders. The top predator was the large Severnichthys , typical of Rhaetian ichthyofaunas, and Gyrolepis was a smaller predator. Late Triassic bony fishes generally included many shell-crushers, and the Charton Bay assemblage is no exception, with teeth of Sargodon , ‘ Lepidotes ’, and Dapedium , the last being a rare record for the British Rhaetic. This kind of burrowed and filled contact occurs elsewhere at the base of the Westbury Mudstone Formation, and so may be a typical marker of the early phases of the Rhaetic Transgression.

A chondrichthyan tooth having a serrated edge, from the Late Pennsylvanian of Xinjiang Uyghur Autonomous Region, China, was identified as Edestus sp. [Cheng, Z., Lucas, S.G., Zidek, J., 1996. Neues Jahrbuch fur Geologie und Palaontologie, Monatshefte 1996 (11), 701-707]. Because of the lack of bilateral symmetry, the tooth does not belong to Edestus or any other known edestoid. It is too incomplete for a definite identification, but its features are consistent with Carcharopsis , which also has serrated teeth, and not with any other described late Paleozoic chondrichthyan genus. If it is Carcharopsis , it is the latest occurrence of the genus, which was previously known only from the Mississippian and the Early Pennsylvanian.

The ability of elasmobranchs to orient to weak electromagnetic fields is well documented. Recently, scientists have employed the use of strong electrosensory stimuli, such as permanent magnets, as a means to evaluate the repellent responses of elasmobranchs and assess the utility of these materials for bycatch repellent technologies. However, several studies have produced contrasting results both between and within species. To explain these results, we hypothesized that conditions leading to vision loss (i.e. turbid water) may be a factor affecting electrosensory repellent success. To simulate a visually deprived environment, the nictitating membranes of juvenile lemon sharks (Negaprion brevirostris) were temporarily sutured closed and the behavioral responses of sharks towards a magnetic apparatus were observed in a pen within the shallows of Bimini, Bahamas. Results demonstrate that the magnet-associated behavior of visually deprived sharks significantly differed from control sharks in regard to: (1) avoidance distance, (2) visit quantity prior to first entrance through the magnet zone, and (3) total entrances/total visits. These findings suggest context-dependent switching, where elasmobranchs may exhibit a heightened reliance on their electrosensory system when the extent of their visual range is reduced. These findings also provide insight into favorable environments (e.g. estuary or other coastal ecosystems) and applications (e.g. inshore fisheries and beach nets) that may yield more consistent and successful future implementations of electrosensory repellents for sharks.

The adult morphology of the tail varies greatly among extant fishes despite sharing both ontogenetic similarities and the functional need to propel the body through a fluid medium. Both sharks (Chondrichthyes) and ray-finned fishes (Actinopterygii) control caudal fin musculature independently of axial body myomere activity to modify the stiffness and shape of their tails. For example, sharks and bony fishes possess different structural elements and muscles and move their tails in different ways, resulting in different locomotory hydrodynamic effects and a range of performance variables including speed and maneuverability. The stiffness of the heterocercal, lobate tail of the shark can be modulated during the tail beat resulting in nearly continuous thrust production. In contrast, the highly flexible tail of ray-finned fishes can be manipulated into many different shape conformations enabling increased maneuverability for these fishes. Consequently, the developmental, morphological, and functional derivation of the tail from the axial trunk has resulted in a diversity of form, the attributes of which may be of ecological and evolutionary significance.

Here we present an ethnographic study on the practice of three butchering methods applied to 645 fish by traditional fishermen in Panama (Central America) and southern Sinai (Red Sea, Egypt). In Method A- the entire fish is gutted ventrally; in Method B- a lengthwise dorsal cut is performed (“Butterfly” fish); and in Method C- boneless strips of meat are produced from sharks (Chondrichthyes). The first two methods are similar to those depicted in several ancient Egyptian reliefs. The objectives of this study were to examine the traditional methods used for fish butchering and determine whether the method applied would generate a characteristic pattern of bone loss and damage (typical fragmentation pattern). For the 645 fish processed for immediate or long-term consumption, by traditional fishermen, we documented the tools used, the sequence of fish cutting, and the correlation between the butchering method applied and fish taxonomy, size, and morphological characteristics. For 171 fish butchered by either of two methods, we show a correlation between the method used and skeletal element presentation, fragmentation pattern, and fracture location. We also note that evidence of fish processing areas may be rare in the archaeological record, since the discarded parts are either consumed by local animals or thrown into the nearby aquatic habitats. The results presented contribute to our understanding of past processing methods, and to the methodology used for analyzing fish remains. We demonstrate the validity of the described butchering methods by providing examples of similarities observed in fragmentation patterns of fish remains recovered from archaeological sites.

Teeth of a new species of hybodont shark Vectiselachos (Chondrichthyes: Lonchidiidae) are described from the late Aptian (Early Cretaceous) of southern England. Vectiselachos gosslingi sp. nov. has very distinctive coarse striations that form raised ridges over the occlusal surfaces of the crown.

The chemistry of the luminous system in a shark is addressed for the first time. Assuming that many luminous species acquire their luminous substrate (luciferin) through the food chain, we investigated the feeding habits of a Norwegian population of the lantern shark Etmopterus spinax Linnaeus, 1758 in order to identify potential alimentary sources of luciferin in this species. Among the major groups of preys found in the diet of E. spinax, we identified three potential sources of luciferin: the euphausiid Meganyctiphanes norvegica Sars, 1857 (tetrapyrrole luciferin), the shrimp Pasiphaea multidentata Esmark, 1866 (coelenterazine) and the teleost Maurolicus muelleri Gmelin, 1789 (coelenterazine). Their luciferins were tested for their presence in the digestive tract and photogenic organs of E. spinax as well as for their cross-reaction with a putative shark catalyst. Although not detected in the diet, the cypridinid luciferin, the third most widespread marine luciferin, was also assayed. As a result, only the coelenterazine was unambiguously detected in the digestive tract of E. spinax and none of the tested luciferins reacted with the shark catalyst extract. Our results support the hypothesis of an unknown luminous system in this shark species, involving either a known luciferin in a specific active or storage form, or an unknown light-emitting molecule.

The faunal associations of the uppermost Jurassic and Early Cretaceous Villar del Arzobispo, El Castellar, and Camarillas formations of the Spanish town of Galve (Maestrazgo Basin of the Iberian Range) are composed of more than fifty taxa belonging to Chondrichthyes, bony fishes, lissamphibians, mammals, and reptiles. Although the presence of turtles has been recognized in these three formations, being very abundant, the published information is limited. The detailed study of these turtles allows us to recognize at least nine taxa, several of them previously not identified in the Spanish record. These taxa correspond to stem Testudines (Solemydidae), members of Paracryptodira (Pleurosternidae), several representatives of Plesiochelyidae and taxa closely related with this clade, representatives of the stem group of Cryptodira (Xinjiangchelyidae) and members of crown Cryptodira. The chelonian fauna of Galve increases the systematic, anatomical, biostratigraphic, and paleobiogeographic knowledge on several clades, represented by taxa shared with other European regions, clades also present in Early Cretaceous sites of North America or Asia, as well as taxa exclusive of the Iberian record.

Recent work has shown that the outflow tract (OFT) of the chondrichthyan heart does not consist of a single component, the conus arteriosus, as has been classically accepted, but two, the myocardial conus arteriosus and the non-myocardial bulbus arteriosus. The aim of this study was to describe the embryonic development of the bulbus, under the assumption that the heart of extant chondrichthyans represents the primitive condition of this organ in jawed vertebrates. The study was carried out in Atlantic sawtail catshark embryos belonging to developmental stages 20–34 of Ballard et al. (1993) . They were examined using histochemical and immunohistochemical techniques for light and fluorescence microscopy. The entire OFT displays a myocardial character during early development. At stage 28, a new, non-myocardial segment forms at the distal end of the OFT. This segment, which is the precursor of the bulbus arteriosus, shows positive reactivity for 4,5-diaminofluorescein 2-diacetate throughout development from stage 31. Smooth muscle α-actin-positive cells appear in the prospective bulbus at stage 33; they markedly increase in number during stage 34. Subsequently, they extend backwards to overlap with the conal myocardium, giving rise to a myocardium and smooth muscle interface that has been described elsewhere as the middle component of the vertebrate OFT. Our embryological findings in a elasmobranch species are consistent with the notion that a second heart field has existed since the beginning of the jawed vertebrate radiation and that the bulbus arteriosus of chondrichthyans is a second heart field-derived structure.

There is general agreement that the presence of five melanocortin receptor genes in tetrapods is the result of two genome duplications that occurred prior to the emergence of the gnathostomes, and at least one local gene duplication that occurred early in the radiation of the ancestral gnathostomes. Hence, it is assumed that representatives from the extant classes of gnathostomes (i.e., Chondrichthyes, Actinopterygii, Sarcopterygii) should also have five paralogous melanocortin genes. Current studies on cartilaginous fishes indicate that while there is evidence for five paralogous melanocortin receptor genes in this class, to date all five paralogs have not been detected in the genome of a single species. This mini-review will discuss the ligand selectivity properties of the melanocortin-3 receptor of the elephant shark (subclass Holocephali) and the ligand selectivity properties of the melanocortin-3 receptor, melanocortin-4 receptor, and the melanocortin-5 receptor of the dogfish (subclass Elasmobranchii). The potential relationship of these melanocortin receptors to the hypothalamus/pituitary/interrenal axis will be discussed.

Long-term vital rate and life-history data essential for sustainable harvest management are rare in tropical fisheries. Two commercially important shark species, Australian blacktip ( Carcharhinus tilstoni ) and spot-tail ( C. sorrah ) sharks in northern Australia have changed in size and population status over the last 25 years. These populations were exploited heavily from the early 1970s to the mid-1980s by foreign fishers, and since then have been harvested by a relatively small domestic fishery. We examined the differences in fork length of these species caught in 1983–1985 and 2002–2006 using Bayesian forms of generalised linear and mixed-effects models. We found clear regional differences and changes in size over time. For blacktips, sharks from the Gulf of Carpentaria have become smaller, and those from the western Northern Territory, larger over time. For spot-tail sharks, average size increased from the 1980s in the Gulf of Carpentaria, but not in the western Northern Territory. On average, sharks from the Gulf of Carpentaria were larger than those on the west coast of the Northern Territory, and females were larger than males. We suggest that changes over time and between regions in the size of spot-tail sharks are most likely due to over-exploitation in the past and subsequent recovery of populations. We discuss the uncertainty in trends for blacktip sharks in relation to fishing effort, availability of resources and species identification errors.

Studies of the species composition, relative abundance and biomass of deep-sea assemblages are needed to create a knowledge base for the assessment of the resource potential and to advise ecosystem-based conservation and fisheries management strategies. This study attempts to create an initial knowledge base of the system by assessing the deep-sea fish assemblages of Colombian Caribbean Sea across a depth range of 200–550 m. A total of 102 species (13 Chondrichthyes and 89 Teleosteans) and 58 families (9 Chondrichthyes and 49 Teleosteans) of deep-sea fish were sampled. This study reveals the existence of three deep-sea fish assemblages and demonstrates that depth plays an important role in ichthyofaunal group differentiation. Most species of the shallower assemblage exhibited a narrow depth range, while species of middle depth assemblage showed the widest depth range. From the point of view of conservation and fisheries management strategies, we need to know the status of deep-sea fish assemblages more fully before initiating a new deep-sea fishery in the Colombian Caribbean Sea. Conservation and protection of the habitats is therefore fundamental to develop a rational and sustainable management of the deep-sea fishery resources of the Colombian Caribbean Sea.

Generalised Linear Models, combined with a Geographic Information System, were used to map the habitats of ten demersal elasmobranch taxa (five skates, four sharks and a stingray) in the eastern English Channel, based on an annual fishery-independent bottom trawl survey conducted each October, and covering 21 years. Habitat models showing mean density levels were developed for the most frequently occurring species, whilst binomial occurrence habitat models were built for less frequent species. The main predictors of elasmobranch habitats in the eastern English Channel were depth, bed shear stress and salinity, followed by seabed sediment type and temperature. Habitat maps highlighted contrasting habitat utilisation across species. Raja clavata, and to a lesser extent Scyliorhinus canicula, showed ontogenetic differences in habitat utilisation, with early life history stages found in shallow coastal waters, sheltered from strong tidal currents and typically with softer sediments. Spatial segregation by sex was also evident for S. canicula, with females found at higher densities on some harder grounds in the study area. An improved knowledge of habitat utilisation by elasmobranchs (particularly for important life history stages and all seasons) is required if spatial management is to be considered for these species. (C) 2012 Elsevier B.V. All rights reserved.

The ?Early Cretaceous (pre-Aptian) Missao Velha Formation of the Araripe Basin of North-East Brazil yields remains referred to two hybodontiform shark taxa: the hybodontid Planohybodus and the lonchidiid Parvodus . Paleoenvironmental analysis of this formation suggests freshwater or perhaps brackish deposition. The specimens described here were collected from a new locality and are found in association with actinopterygian and sarcopterygian fishes and rarer turtles, crocodylomorphs and theropod dinosaurs. The chondrichthyan assemblage is represented by isolated teeth, cephalic spines, and dorsal fin spines. This is the first record of Planohybodus in the Araripe Basin and the first record of Parvodus in the Cretaceous of Gondwana.