Journal articles on the topic 'Chondrichtyan'
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Liao, Jau-Chyn, Michal Ginter, and José Ignacio Valenzuela-Rios. "Chondrichthyan microremains from the Givetian of the Aragonian Pyrenees (Spain)." Bulletin de la Société Géologique de France 178, no. 3 (May 1, 2007): 171–78. http://dx.doi.org/10.2113/gssgfbull.178.3.171.
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Abstract A Lower and basal Middle varcus Zone (Givetian, Middle Devonian) vertebrate association consisting of chondrichtyan teeth and scales of the genus Phoebodus is documented for the first time from the Aragonian Pyrenees of Spain. This record suggests that different teeth morphologies that were previously treated as separate taxa could be grouped in Phoebodus fastigatus. Moreover, the teeth and scales association is in agreement with the previously reconstructed squamation pattern of this taxon.
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Coates, Michael I., John A. Finarelli, Ivan J. Sansom, Plamen S. Andreev, Katharine E. Criswell, Kristen Tietjen, Mark L. Rivers, and Patrick J. La Riviere. "An early chondrichthyan and the evolutionary assembly of a shark body plan." Proceedings of the Royal Society B: Biological Sciences 285, no. 1870 (January 3, 2018): 20172418. http://dx.doi.org/10.1098/rspb.2017.2418.
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Although relationships among the major groups of living gnathostomes are well established, the relatedness of early jawed vertebrates to modern clades is intensely debated. Here, we provide a new description of Gladbachus , a Middle Devonian (Givetian approx. 385-million-year-old) stem chondrichthyan from Germany, and one of the very few early chondrichthyans in which substantial portions of the endoskeleton are preserved. Tomographic and histological techniques reveal new details of the gill skeleton, hyoid arch and jaws, neurocranium, cartilage, scales and teeth. Despite many features resembling placoderm or osteichthyan conditions, phylogenetic analysis confirms Gladbachus as a stem chondrichthyan and corroborates hypotheses that all acanthodians are stem chondrichthyans. The unfamiliar character combination displayed by Gladbachus , alongside conditions observed in acanthodians, implies that pre-Devonian stem chondrichthyans are severely under-sampled and strongly supports indications from isolated scales that the gnathostome crown group originated at the latest by the early Silurian (approx. 440 Ma). Moreover, phylogenetic results highlight the likely convergent evolution of conventional chondrichthyan conditions among earliest members of this primary gnathostome division, while skeletal morphology points towards the likely suspension feeding habits of Gladbachus , suggesting a functional origin of the gill slit condition characteristic of the vast majority of living and fossil chondrichthyans.
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Richards, Kelly R., Janet E. Sherwin, Timothy R. Smithson, Rebecca F. Bennion, Sarah J. Davies, John E. A. Marshall, and Jennifer A. Clack. "Diverse and durophagous: Early Carboniferous chondrichthyans from the Scottish Borders." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 108, no. 1 (March 2017): 67–87. http://dx.doi.org/10.1017/s1755691018000166.
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ABSTRACTChondrichthyan teeth from a new locality in the Scottish Borders supply additional evidence of Early Carboniferous chondrichthyans in the UK. The interbedded dolostones and siltstones of the Ballagan Formation exposed along Whitrope Burn are interpreted as representing a restricted lagoonal environment that received significant amounts of land-derived sediment. This site is palynologically dated to the latest Tournaisian–early Viséan. The diverse dental fauna documented here is dominated by large crushing holocephalan toothplates, with very few, small non-crushing chondrichthyan teeth. Two new taxa are named and described. Our samples are consistent with worldwide evidence that chondrichthyan crushing faunas are common following the Hangenberg extinction event. The lagoonal habitat represented by Whitrope Burn may represent a temporary refugium that was host to a near-relict fauna dominated by large holocephalan chondrichthyans with crushing dentitions. Many of these had already become scarce in other localities by the Viséan and become extinct later in the Carboniferous. This fauna provides evidence of early endemism or niche separation within European chondrichthyan faunas at this time. This evidence points to a complex picture in which the diversity of durophagous chondrichthyans is controlled by narrow spatial shifts in niche availability over time.
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Brazeau, Martin D., and Valerie de Winter. "The hyoid arch and braincase anatomy of Acanthodes support chondrichthyan affinity of ‘acanthodians’." Proceedings of the Royal Society B: Biological Sciences 282, no. 1821 (December 22, 2015): 20152210. http://dx.doi.org/10.1098/rspb.2015.2210.
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Solving the evolutionary relationships of the acanthodians is one of the key problems in reconstructing ancestral anatomical conditions for the jawed vertebrates (gnathostomes). Current debate concerns whether acanthodians are an assemblage of stem chondrichthyans, or a more generalized grade encompassing some early stem osteichthyans. The skull anatomy of Acanthodes bronni has been pivotal in these debates, owing to tension between chondrichthyan- and osteichthyan-like models of reconstruction. We use computed tomography scanning and traditional palaeontological techniques to resolve the long-standing debate about the anatomy of the jaw suspension. We establish the correct length of the hyomandibula and show that it attaches to a process on the ventrolateral angle of the braincase below the jugular vein groove. This condition corresponds precisely to that in chondrichthyans. This character represents an unambiguously optimized synapomorphy with chondrichthyans given current gnathostome phylogenies, corroborating the growing consensus of the chondrichthyan affinity of acanthodians.
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Pimiento, Catalina, Gerardo González-Barba, Dana J. Ehret, Austin J. W. Hendy, Bruce J. MacFadden, and Carlos Jaramillo. "Sharks and rays (Chondrichthyes, Elasmobranchii) from the late Miocene Gatun Formation of Panama." Journal of Paleontology 87, no. 5 (September 2013): 755–74. http://dx.doi.org/10.1666/12-117.
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The late Miocene Gatun Formation of northern Panama contains a highly diverse and well sampled fossil marine assemblage that occupied a shallow-water embayment close to a purported connection between the Pacific and Atlantic (Caribbean) oceans. However, the diverse chondrichthyan fauna has been poorly documented. Based on recent field discoveries and further analysis of existing collections, the chondrichthyan fauna from this unit comprises at least 26 taxa, of which four species are extinct today. The remaining portion of the total chondrichthyan biodiversity has affinities with modern taxa and is therefore comprised of long-lived species. Based on known records of the modern geographic distribution range of the Gatun chondrichthyans, the fauna has mixed biogeographic affinities suggesting that around 10 million yr ago, a connection likely occurred between the Pacific Ocean and the Caribbean Sea. Given the known habitat preferences for modern chondrichthyans, the Gatun fauna was primarily adapted to shallow waters within the neritic zone. Finally, comparisons of Gatun dental measurements with other faunas suggest that many of the taxa have an abundance of small individuals, in agreement with previous studies that proposed this area as a paleonursery habitat for the species Carcharocles megalodon.
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Sabadin, D. E., L. O. Lucifora, S. A. Barbini, D. E. Figueroa, and M. Kittlein. "Towards regionalization of the chondrichthyan fauna of the Southwest Atlantic: a spatial framework for conservation planning." ICES Journal of Marine Science 77, no. 5 (May 15, 2020): 1893–905. http://dx.doi.org/10.1093/icesjms/fsaa064.
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Abstract Biogeographic regionalization identifies natural species assemblages of a given region. In this study, the geographic distribution of chondrichthyan species richness and species assemblages for the Southwest Atlantic were identified. The geographic distribution of 103 chondrichthyans was estimated through modelling. Based on the obtained binary maps, the distribution of chondrichthyan richness was obtained at four taxonomic levels: class Chondrichthyes (chondrichthyans), subclass Holocephali (chimaeras), division Selachii (sharks), and division Batomorphi (batoids). The continental shelf off Uruguay and southern Brazil presented the highest levels of chondrichthyan richness, and a smaller peak was found in El Rincón (northern Argentina). Shark richness concentrated mainly off Lagoa dos Patos (southern Brazil). Batoid richness was maximal off Uruguay and northern Argentina, including modes in El Rincón, San Jorge Gulf, and slope of the Argentinean shelf. Classification analyses revealed the presence of a hierarchical regionalization, with three main and six minor assemblages. Main assemblages are hierarchically identifiable as provinces and minor ones as ecoregions or districts. Two of the main assemblages correspond with the Argentinean and Magellanic Provinces; the third one is identified here for the first time, the Patagonian Slope Province. This regionalization provides the basis for the design of protected area networks for conservation or management purposes.
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WHITE, WILLIAM T., and ALFRED KO’OU. "An annotated checklist of the chondrichthyans of Papua New Guinea." Zootaxa 4411, no. 1 (April 19, 2018): 1. http://dx.doi.org/10.11646/zootaxa.4411.1.1.
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An annotated checklist of the chondrichthyan fishes (sharks, rays, and chimaeras) of Papua New Guinean waters is herein presented. The checklist is the result of a large biodiversity study on the chondrichthyan fauna of Papua New Guinea between 2013 and 2017. The chondrichthyan fauna of Papua New Guinea has historically been very poorly known due to a lack of baseline information and limited deepwater exploration. A total of 131 species, comprising 36 families and 68 genera, were recorded. The most speciose families are the Carcharhinidae with 29 species and the Dasyatidae with 23 species. Verified voucher material from various biological collections around the world are provided, with a total of 687 lots recorded comprising 574 whole specimens, 128 sets of jaws and 21 sawfish rostra. This represents the first detailed, verified checklist of chondrichthyans from Papua New Guinean waters.
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Martínez, Lidia Mayorga, Aurea Orozco, Patricia Villalobos, and Carlos Valverde-R. "Cloning and characterization of a type 3 iodothyronine deiodinase (D3) in the liver of the chondrichtyan chiloscyllium punctatum." General and Comparative Endocrinology 156, no. 3 (May 2008): 464–69. http://dx.doi.org/10.1016/j.ygcen.2008.02.012.
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Soldo, Alen, and Lovrenc Lipej. "An Annotated Checklist and the Conservation Status of Chondrichthyans in the Adriatic." Fishes 7, no. 5 (September 19, 2022): 245. http://dx.doi.org/10.3390/fishes7050245.
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Although there is a high number of publications listing fish species in the Adriatic, only a few have focused on chondrichthyans, while their conservation status has been investigated even less. Thus, this paper aims to provide an updated and annotated checklist of the chondrichthyans occurring in the Adriatic waters with their presence and conservation status. Each species is evaluated against the criteria defined in IUCN (International Union for Conservation of Nature) Red List Categories and Criteria and according to the guidelines for national and regional level assessments. In total, 60 chondrichthyan species from 27 families and 42 genera are listed. The list contains 33 species of sharks, 26 species of rays and one chimera. Assessment of the conservation status reveals that three species are now considered Regionally Extinct (namely Squatina oculata, Pristis pectinata and Rhinobatos rhinobatos). A total of 21 species are assessed as Critically Endangered, 8 are Endangered and 10 are Vulnerable. Of the remaining species, six are Near Threatened and the same number of species are Least Concern and Data Deficient. Considering that the principal driver of chondrichthyan decline and regional extinction is overfishing, it is recommended that the Adriatic countries adopt the same management measures and strengthen their coordination.
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Greif, Merle, Humberto G. Ferrón, and Christian Klug. "A new Meckel’s cartilage from the Devonian Hangenberg black shale in Morocco and its position in chondrichthyan jaw morphospace." PeerJ 10 (December 21, 2022): e14418. http://dx.doi.org/10.7717/peerj.14418.
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Fossil chondrichthyan remains are mostly known from their teeth, scales or fin spines only, whereas their cartilaginous endoskeletons require exceptional preservational conditions to become fossilized. While most cartilaginous remains of Famennian (Late Devonian) chondrichthyans were found in older layers of the eastern Anti-Atlas, such fossils were unknown from the Hangenberg black shale (HBS) and only a few chondrichthyan teeth had been found therein previously. Here, we describe a Meckel’s cartilage from the Hangenberg black shale in Morocco, which is the first fossil cartilage from these strata. Since no teeth or other skeletal elements have been found in articulation, we used elliptical Fourier (EFA), principal component (PCA), and hierarchical cluster (HCA) analyses to morphologically compare it with 41 chondrichthyan taxa of different size and age and to evaluate its possible systematic affiliation. PCA and HCA position the new specimen closest to some acanthodian and elasmobranch jaws. Accordingly, a holocephalan origin was excluded. The jaw shape as well as the presence of a polygonal pattern, typical for tessellated calcified cartilage, suggest a ctenacanth origin and we assigned the new HBS Meckel’s cartilage to the order Ctenacanthiformes with reservations.
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EBERT, DAVID A., SABINE P. WINTNER, and PETER M. KYNE. "An annotated checklist of the chondrichthyans of South Africa." Zootaxa 4947, no. 1 (March 17, 2021): 1–127. http://dx.doi.org/10.11646/zootaxa.4947.1.1.
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An annotated checklist of chondrichthyan fishes (sharks, batoids, and chimaeras) occurring in South African waters is presented. The checklist is the result of decades of research and on-going systematic revisions of the regional fauna. The chondrichthyan fauna of South Africa is one of the richest in the world with 191 species, comprising 50 families and 103 genera. It consists of 30 families, 64 genera, and 111 species of sharks; 17 families, 36 genera, and 72 species of batoids; and, 3 families, 5 genera, and 8 species of chimaeras. The most species-rich shark families are the whaler sharks Carcharhinidae with 20 species followed by the deepwater catsharks Pentanchidae with 13 species. The most species-rich batoid families are the hardnose stakes Rajidae with at least 21 species followed by the stingrays Dasyatidae with 13 species. This monograph represents the first detailed annotated checklist of chondrichthyans from South Africa in over 30 years.
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Becerril-García, Edgar Eduardo, Marcial Arellano-Martínez, Daniela Bernot-Simon, Edgar Mauricio Hoyos-Padilla, Felipe Galván-Magaña, and Céline Godard-Codding. "Steroid hormones and chondrichthyan reproduction: physiological functions, scientific research, and implications for conservation." PeerJ 8 (August 13, 2020): e9686. http://dx.doi.org/10.7717/peerj.9686.
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The study of the reproductive aspects of chondrichthyans through the analysis of steroid hormones has been carried out for more than five decades in several species around the world. This scientific knowledge constitutes the basis of the reproductive endocrinology of chondrichthyans, which has provided information regarding their sexual maturation, gametogenesis, mating seasons, gestation periods, and parturition. The present review summarises the existing literature on steroid hormones in chondrichthyan reproduction and identifies future research directions addressing critical knowledge gaps in the reproductive physiology of this taxon. A total of 59 peer reviewed scientific papers from 1963 to 2020 were reviewed and the following parameters analysed: species, steroid hormones, biological matrix, field sampling (year, location), and methodology (assays, sample size, precision, and recoveries). We provided a summary of the methods, biological matrices, and the functions of up to 19 hormones on the biology of 34 species of chondrichthyans that have been analysed to date. The majority of the studies used radioimmunoassay as the main methodology (76.3%; n = 45/49); while the most frequent biological matrix used was plasma (69.5%; n = 41/49). A Kernel’s heat map was generated to present the scientific effort according to geographic location and evidenced a lack of research in high biodiversity areas for chondrichthyans worldwide. The implications of the study of steroid hormones for the conservation of chondrichthyans are discussed, as only 2.9% of the species of this group have been analysed and most of the scientific effort (93.2%; n = 55/59 papers) has focused on the analysis of less than six hormones.
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Ruibal Núñez, J., N. D. Bovcon, P. D. Cochia, and M. E. Góngora. "Bycatch of chondrichthyans in a coastal trawl fishery on Chubut province coast and adjacent waters, Argentina." Journal of the Marine Biological Association of the United Kingdom 98, no. 3 (October 28, 2016): 605–16. http://dx.doi.org/10.1017/s0025315416001508.
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Chondrichthyans are usually caught incidentally in fisheries for species of high commercial value and then discarded on board or landed as by-products. On the coast of Chubut province and adjacent waters (43°00′S–44°56′S) a bottom trawl fishery has developed targeted at the Patagonian shrimp (Pleoticus muelleri) and common hake (Merluccius hubbsi). Since 2005, this fishery has been monitored by the On-board Observers Program of Chubut province (POBCh). With the aim of advancing towards an ecosystem approach, POBCh not only collects information about target species but also about all the species caught by the trawl nets of the province fisheries. From the information collected by this programme it was possible to identify and record the chondrichthyan species vulnerable to the fishing gear used by the coastal fleet that operates from Puerto Rawson. The composition of the fleet catch was characterized according to the target species during the 2005–2014 period. In the analysis of 3786 hauls, 23 species of chondrichthyans (seven species of sharks, 15 species of batoids and a single species of Holocephali) were identified. Seven species showed a frequency of occurrence greater than 10% (Callorhinchus callorynchus, Discopyge tschudii, Mustelus schmitti, Sympterygia bonapartii, Psammobatis normani, Squalus acanthias and Zearaja chilensis). Species spatial distribution was evaluated and five areas of species assemblages were established. Besides the aspects related to bycatch, these analyses have contributed to the knowledge of the chondrichthyan biodiversity in the provincial coast where the fleet operates, a region with incomplete and mostly dispersed and outdated information.
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Johanson, Zerina, Moya Smith, Sophie Sanchez, Tim Senden, Kate Trinajstic, and Cathrin Pfaff. "Questioning hagfish affinities of the enigmatic Devonian vertebrate Palaeospondylus." Royal Society Open Science 4, no. 7 (July 2017): 170214. http://dx.doi.org/10.1098/rsos.170214.
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Palaeospondylus gunni Traquair, 1890 is an enigmatic Devonian vertebrate whose taxonomic affinities have been debated since it was first described. Most recently, Palaeospondylus has been identified as a stem-group hagfish (Myxinoidea). However, one character questioning this assignment is the presence of three semicircular canals in the otic region of the cartilaginous skull, a feature of jawed vertebrates. Additionally, new tomographic data reveal that the following characters of crown-group gnathostomes (chondrichthyans + osteichthyans) are present in Palaeospondylus : a longer telencephalic region of the braincase, separation of otic and occipital regions by the otico-occipital fissure, and vertebral centra. As well, a precerebral fontanelle and postorbital articulation of the palatoquadrate are characteristic of certain chondrichthyans. Similarities in the structure of the postorbital process to taxa such as Pucapampella , and possible presence of the ventral cranial fissure, both support a resolution of Pa. gunni as a stem chondrichthyan. The internally mineralized cartilaginous skeleton in Palaeospondylus may represent a stage in the loss of bone characteristic of the Chondrichthyes.
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Giovos, Ioannis, Fabrizio Serena, Dimitra Katsada, Athanasios Anastasiadis, Adi Barash, Charis Charilaou, Jason M. Hall-Spencer, et al. "Integrating Literature, Biodiversity Databases, and Citizen-Science to Reconstruct the Checklist of Chondrichthyans in Cyprus (Eastern Mediterranean Sea)." Fishes 6, no. 3 (July 26, 2021): 24. http://dx.doi.org/10.3390/fishes6030024.
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Chondrichthyans are apex predators influencing the trophic web through a top-down process thus their depletion will affect the remaining biota. Notwithstanding that, research on chondrichthyans is sparse or data-limited in several biogeographic areas worldwide, including the Levantine Sea. We revise and update the knowledge of chondrichthyans in Cyprus based on a bibliographic review that gains information retrieved from peer-reviewed and grey literature, Global Biodiversity Information Facility (135 records of at least 18 species) and the Ocean Biodiversity Information System (65 records of at least14 species), and the citizen science project Mediterranean Elasmobranchs Citizen Observations (117 records per 23 species). Our updated checklist reports 60 species that account for about 70% of the Mediterranean chondrichthyan biota. The list includes 15 more species than the previous checklist and our study reports three new species for Cyprus waters, namely the blackmouth catshark Dalatias licha, the round fantail stingray Taeniurops grabatus, and the sawback angelshark Squatina aculeata. Our research highlights the need for conservation measures and more studies regarding the highly threatened blackchin guitarfish Glaucostegus cemiculus and the devil ray Mobula mobular, and stresses the importance for training a new generation of observers to strengthen the knowledge and conservation of elasmobranchs in the region.
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Freitas, Mafalda, Luísa Costa, João Delgado, Sebastián Jiménez, Viriato Timóteo, Joana Vasconcelos, and José A. González. "Deep-sea sharks as by-catch of an experimental fishing survey for black scabbardfishes (Aphanopus spp.) off the Canary Islands (NE Atlantic)." Scientia Marina 82, S1 (December 20, 2018): 151. http://dx.doi.org/10.3989/scimar.04793.03a.
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The deep-sea sharks associated as by-catch of the Madeiran midwater drifting longline fishery for scabbardfishes (Aphanopus spp.) were investigated by means of an experimental survey at 800-1200 m depth within the Canary Islands Exclusive Economic Zone, whose fishing grounds have been exploited during the past 15 years. Nine species of chondrichthyans were identified, belonging to five families: Pseudotriakidae, Centrophoridae, Etmopteridae, Somniosidae and Chimaeridae. Data on length, weight and sex ratio for the 436 chondrichthyan individuals caught in the March 2009 survey are given. Several voucher specimens of each species caught were deposited in the collections of the Natural History Museum of Funchal.
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García-Salinas, Pablo, Victor Gallego, and Juan F. Asturiano. "Reproductive Anatomy of Chondrichthyans: Notes on Specimen Handling and Sperm Extraction. II. Sharks and Chimaeras." Animals 11, no. 8 (July 23, 2021): 2191. http://dx.doi.org/10.3390/ani11082191.
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The chondrichthyan fishes, which comprise sharks, rays, and chimaeras, are one of the most threatened groups of vertebrates on the planet. Given this situation, an additional strategy for the protection of these species could be the ex situ conservation projects developed in public aquaria and research centers. Nevertheless, to increase sustainability and to develop properly in situ reintroduction strategies, captive breeding techniques, such as sperm extraction and artificial insemination, should be developed. These techniques are commonly used in other threatened species and could be also used in chondrichthyans. However, the different reproductive morphologies found in this group can complicate both processes. Therefore, a comparison of the reproductive anatomy of eight distinct chondrichthyans, with an emphasis on those important differences when performing sperm extraction or artificial insemination, is carried out herein. Sharks and chimaeras belonging to the Scyliorhinidae, Carcharhinidae, Centrophoridae, Etmopteridae, Hexanchidae, and Chimaeridae families were obtained from commercial fisheries, public aquaria, and stranding events. In addition, the process of obtaining viable sperm samples through cannulation, abdominal massage, and oviducal gland extraction is described in detail for both living and dead animals.
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Johanson, Zerina, Mikiko Tanaka, Natalie Chaplin, and Moya Smith. "Early Palaeozoic dentine and patterned scales in the embryonic catshark tail." Biology Letters 4, no. 1 (December 4, 2007): 87–90. http://dx.doi.org/10.1098/rsbl.2007.0502.
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Regular scale patterning, restricted to the caudalmost tail and organized into two opposing rows on each side of the tail, is observed in few chondrichthyans. These evenly spaced scales, in dorsal and ventral rows, develop in an iterative sequence from the caudal tip, either side of the notochord. They are subsequently lost as a scattered pattern of placoid scales develops on the body and fins. An identical organized pattern is observed in tail scales of Scyliorhinus canicula (catshark), where the expression of sonic hedgehog signal is restricted to the epithelium of developing scales and remains localized to the scale pocket. Regulation of iterative scale position by sonic hedgehog is deeply conserved in vertebrate phylogeny. These scales also reveal an archaic histological structure of a dentine type found in the oldest known shark scales from the Ordovician and Silurian. This combination of regulated pattern and ancient dentine occurs only in the tail, representing the primary scalation. Scattered body scales in elasmobranchs such as S. canicula originate secondarily from differently regulated development, one with typical orthodentine around a central pulp cavity. These observations emphasize the modular nature of chondrichthyan scale development and illustrate previously undetected variation as an atavism in extant chondrichthyan dentine.
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Ivanov, Alexander O., Aleksandr S. Bakaev, Merlynd K. Nestell, and Galina P. Nestell. "Fish Microremains from the Cutoff Formation (Roadian, Middle Permian) of the Guadalupe Mountains, West Texas, USA." Micropaleontology 67, no. 4 (2021): 365–402. http://dx.doi.org/10.47894/mpal.67.4.03.
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A new assemblage of diverse fish microremains from the Roadian Williams Ranch Member of the Cutoff Formation in the Guadalupe Mountains, West Texas is described. The chondrichthyan remains comprise symmoriiforms Stethacanthulus decorus, Kungurodus sp. and indeterminate taxa; ctenacanthiform Glikmanius myachkovensis; euselachian Sphenacanthus sp. and Hybodontiformes indet.; anachronistids Cooleyella amazonensis, Cooleyella sp. and Reifella lata Ivanov, n. gen., n. sp.; jalodontids Adamantina foliacea, Isacrodus marthae and Isacrodus sp.; indeterminate euchondrocephalian and chondrichthyans. Actinopterygian remains include the elonichthyid Alilepis texasensis Bakaev, n. sp., indeterminate platysomids and acrolepidids, indeterminate taxa and other osteichthyans. The assemblage includes the widely geographically distributed taxa Cooleyella amazonensis, Stethacanthulus decorus and Adamantina foliacea. The occurrence of last two species in the Cutoff Formation represents their youngest record in the world. Possible migration paths are proposed for Alilepis.
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Križnar, Matija. "Lower Permian (Artinskian) chondrichthyan tooth remains (Petalodontidae) from Dovje (Karavanke Mts., NW Slovenia)." Geologija 65, no. 2 (December 21, 2022): 217–24. http://dx.doi.org/10.5474/geologija.2022.012.
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Fossil remains of chondrichthyan tooth bases (roots) were found in Lower Permian beds exposed along the forest road between Dovje and Plavški Rovt. These layers are part of the clastic development of the Trogkofel Group beds. They are composed of an alternation of dark to light-grey shales, siltstone, and sandstone with rare beds of the conglomerate. Within the clastic succession, layers or lenses of dark-grey to black limestones (biosparitic, biomicritic and oolitic) and limestone breccias occur. The limestone consists remains of algae, fusulinids, brachiopods, and mostly crinoids (Palermocrinus and Entrochus). Detail study has shown that two remains of tooth bases belong to the genus Petalodus, one of them to the species Petalodus ohioensis. The bases are tongue-shaped and come to a rounded point in the distal (base end) edge. On the surface of the base, the typical oval-shaped foramina are visible. In addition, the osteodentine is visible on the cross-section of one specimen. Teeth of Petalodus are often the most common chondrichthyan fossil vertebrate remains reported from the Carboniferous and Permian rocks of the USA, Europe, and Russia. In Slovenia, Petalodus ohioensis has been recorded only from Upper Carboniferous beds. The new record of Lower Permian remains contributes to the knowledge of this cosmopolitan but still common genus of Late Paleozoic chondrichthyans.
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Caraguel, Jean-Marie, Thomas Barreau, Sarah Brown-Vuillemin, and Samuel P. Iglésias. "In vivo staining with alizarin for ageing studies on chondrichthyan fishes." Aquatic Living Resources 33 (2020): 1. http://dx.doi.org/10.1051/alr/2020002.
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Age determination for stock assessments and conservation of cartilaginous fishes is mainly obtained by counting the annual growth bands in vertebrae. Recent studies show numerous inconsistencies and the need for systematic validation. We assessed the effectiveness of the fluorochrome alizarin red S, a common skeleton vital marker used as a time stamp for teleost fishes, on chondrichthyan. Twenty-five captive small-spotted catsharks (Scyliorhinus canicula) were marked by alizarin red S intraperitoneal injections. The fluorochrome produced a wide fluorescent mark on sectioned vertebral centra of all injected fish. Alizarin red S did not have a deleterious effect on growth during three months monitoring. The marks obtained remained stable in vivo for more than four years after injections and were resistant to fading during the observation under the microscope excitation light. Our results suggest that alizarin red S is an effective tool for long time vital marking of chondrichthyans.
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Smith, JD, and PH Towler. "Polonium-210 in cartilaginous fishes (Chondrichthyes) from south-eastern Australian waters." Marine and Freshwater Research 44, no. 5 (1993): 727. http://dx.doi.org/10.1071/mf9930727.
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A study was made of the concentration of the naturally occurring radionuclide polonium-210 in the livers of cartilaginous fishes (chondrichthyans) caught in the waters of Port Phillip Bay, Victoria, Australia in 1991. Five elasmobranch species had 210Po concentrations in the range 1-31 Bq kg-1 (wet weight) and one holocephalian species, the elephant fish (Callorhynchus milii), was exceptional with a 210Po range of 60-270 Bq kg-1 (n=3, mean 180 Bq kg-1). Lead-210 was present at 0.1- 1.1 Bq kg-1 and activity concentration ratios of 210Po:210Pb were all greater than 1, indicating that the 210Po could not all have grown in from in situ decay of 210Pb within the chondrichthyan liver. The concentration of 210Po in the livers appeared to be species related. Concentrations of the trace metals Cu, Fe and Zn showed no correlation with the 210Po and were not species-related. The mean concentration of 210Po measured in Port Phillip Bay water was 0.32 mBq kg-1. This yields concentration factors of 3.2 × 103 to 8.4 × 105 for unsupported 210Po in the livers of the chondrichthyans. The total 210Po (using Q=20) exposes the livers to a weighted absorbed dose of up to 140 mGy year-1 (16�Gy h-1), which is >99% of the total internal dose and three orders of magnitude greater than the external dose based on estimated levels of 40K.
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RIGBY, CASSANDRA L., WILLIAM T. WHITE, and PETER M. KYNE. "Description of the egg cases of Dentiraja polyommata (Rajiformes: Rajidae) and Asymbolus pallidus (Carcharhiniformes: Scyliorhinidae) from Queensland, Australia." Zootaxa 4294, no. 3 (July 19, 2017): 329. http://dx.doi.org/10.11646/zootaxa.4294.3.3.
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Descriptions of the egg cases of Dentiraja polyommata (n = 16) and Asymbolus pallidus (n = 44) are provided from egg cases collected from a commercial trawl fishery off Swain Reefs, central Queensland, Australia. Egg cases of D. polyommata are rectangular, convex and golden-tan in colour and those of A. pallidus elongate, vase-shaped and golden. To determine if a comparative statistical non-metric multi-dimensional scaling approach could identify egg cases of species taken in the same region and fishery, egg cases were compared with the skate D. endeavouri and catsharks A. analis, A. rubiginosus and Figaro boardmani. The statistical approach clearly discriminated the species based on five proportional measurements and identified the morphometrics that separated genera and species. This approach is valuable in a fisheries context for accurate identification of visually similar egg cases that can assist management of oviparous chondrichthyans. A rare incidence of intraspecific chondrichthyan cannibalism was noted for A. pallidus males that consumed egg cases of their own species.
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Pears, Jacob B., Carley Tillett, Rui Tahara, Hans C. E. Larsson, Kate Trinajstic, and Catherine A. Boisvert. "The Development of the Chimaeroid Pelvic Skeleton and the Evolution of Chondrichthyan Pelvic Fins." Journal of Developmental Biology 10, no. 4 (December 12, 2022): 53. http://dx.doi.org/10.3390/jdb10040053.
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Pelvic girdles, fins and claspers are evolutionary novelties first recorded in jawed vertebrates. Over the course of the evolution of chondrichthyans (cartilaginous fish) two trends in the morphology of the pelvic skeleton have been suggested to have occurred. These evolutionary shifts involved both an enlargement of the metapterygium (basipterygium) and a transition of fin radial articulation from the pelvic girdle to the metapterygium. To determine how these changes in morphology have occurred it is essential to understand the development of extant taxa as this can indicate potential developmental mechanisms that may have been responsible for these changes. The study of the morphology of the appendicular skeleton across development in chondrichthyans is almost entirely restricted to the historical literature with little contemporary research. Here, we have examined the morphology and development of the pelvic skeleton of a holocephalan chondrichthyan, the elephant shark (Callorhinchus milii), through a combination of dissections, histology, and nanoCT imaging and redescribed the pelvic skeleton of Cladoselache kepleri (NHMUK PV P 9269), a stem holocephalan. To put our findings in their evolutionary context we compare them with the fossil record of chondrichthyans and the literature on pelvic development in elasmobranchs from the late 19th century. Our findings demonstrate that the pelvic skeleton of C. milii initially forms as a single mesenchymal condensation, consisting of the pelvic girdle and a series of fin rays, which fuse to form the basipterygium. The girdle and fin skeleton subsequently segment into distinct components whilst chondrifying. This confirms descriptions of the early pelvic development in Scyliorhinid sharks from the historical literature and suggests that chimaeras and elasmobranchs share common developmental patterns in their pelvic anatomy. Alterations in the location and degree of radial fusion during early development may be the mechanism responsible for changes in pelvic fin morphology over the course of the evolution of both elasmobranchs and holocephalans, which appears to be an example of parallel evolution.
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Szabó, Márton, László Kocsis, Mariann Bosnakoff, and Krisztina Sebe. "A diverse Miocene fish assemblage (Chondrichthyes and Osteichthyes) from the Pécs-Danitzpuszta sand pit (Mecsek Mts, Hungary)." Földtani Közlöny 151, no. 4 (December 4, 2021): 363–409. http://dx.doi.org/10.23928/foldt.kozl.2021.151.4.363.
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Chondrichthyans and osteichthyans are widely reported from marine sediments of the Central Paratethys, not only by sporadic occurrences, but also by complex, diverse fish assemblages. Here we present a rich fish fauna from the upper Miocene (Pannonian, Tortonian) lacustrine sediments exposed in the Pécs-Danitzpuszta sand pit, in the SW Pannonian Basin. Altogether 22 227 specimens were investigated, and they could be classified into 17 chondrichthyan and 16 osteichthyan taxa. Among the chondrichthyans Odontaspididae (55.51%) and Myliobatidae (14.4%) are the most abundant, while the bony fishes are dominated by the Sparidae (77.07%). The limonitic, yellow, coarse-grained, gravelly sands yielded an extremely large amount of isolated fish fossils. A considerable part of the vertebrate material of the sands is likely reworked from older, middle Miocene (Badenian and Sarmatian, i.e. Langhian and Serravallian) sediments. The late Miocene calcareous marls underlying the sands also yielded a variety of fish remains. From these remains, associated and articulated latid bones are coeval with the sediment and suggest freshwater and brackish conditions in the area, in accord with other biotic data. Other, isolated fossils, namely teeth, otoliths, cycloid scales and jaw elements of Gadidae, Gobiidae, Sparidae and Latidae could be reworked and thus have a very limited paleoecological significance. Based on habitat preferences of extant relatives, all chondrichthyans and most osteichthyan taxa found in the sands must be of Badenian origin. The abundant remains allow for some conclusions on the environmental conditions during the Badenian. They refer to a shallow, coastal environment with tropical-subtropical climate with connection to more open water habitats. Remains of some osteichthyan taxa were found in coprolites, showing that these taxa were part of the food chain as prey items. Sirenian ribs and odontocete limb bones bearing tooth marks refer to trophic relations between marine mammals and large sized macropredatory sharks. The Pécs-Danitzpuszta record of shark-attributed bite marks on bones of marine mammals is the second of the Badenian of the Central Paratethys. Acipenserids and latids of the sands, linked to brackish and/or freshwater environments, could originate from any Miocene stratigraphic units.
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Turner, Marian. "Chondrichthyan crisis." Nature Ecology & Evolution 5, no. 11 (October 7, 2021): 1471. http://dx.doi.org/10.1038/s41559-021-01567-0.
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Frey, Linda, Michael Coates, Michał Ginter, Vachik Hairapetian, Martin Rücklin, Iwan Jerjen, and Christian Klug. "The early elasmobranch Phoebodus : phylogenetic relationships, ecomorphology and a new time-scale for shark evolution." Proceedings of the Royal Society B: Biological Sciences 286, no. 1912 (October 2, 2019): 20191336. http://dx.doi.org/10.1098/rspb.2019.1336.
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Anatomical knowledge of early chondrichthyans and estimates of their phylogeny are improving, but many taxa are still known only from microremains. The nearly cosmopolitan and regionally abundant Devonian genus Phoebodus has long been known solely from isolated teeth and fin spines. Here, we report the first skeletal remains of Phoebodus from the Famennian (Late Devonian) of the Maïder region of Morocco, revealing an anguilliform body, specialized braincase, hyoid arch, elongate jaws and rostrum, complementing its characteristic dentition and ctenacanth fin spines preceding both dorsal fins. Several of these features corroborate a likely close relationship with the Carboniferous species Thrinacodus gracia , and phylogenetic analysis places both taxa securely as members of the elasmobranch stem lineage. Identified as such, phoebodont teeth provide a plausible marker for range extension of the elasmobranchs into the Middle Devonian, thus providing a new minimum date for the origin of the chondrichthyan crown-group. Among pre-Carboniferous jawed vertebrates, the anguilliform body shape of Phoebodus is unprecedented, and its specialized anatomy is, in several respects, most easily compared with the modern frilled shark Chlamydoselachus . These results add greatly to the morphological, and by implication ecological, disparity of the earliest elasmobranchs.
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Burrow, Carole J., Susan Turner, John G. Maisey, Sylvain Desbiens, and Randall F. Miller. "Spines of the stem chondrichthyan Doliodus latispinosus (Whiteaves) comb. nov. from the Lower Devonian of eastern Canada." Canadian Journal of Earth Sciences 54, no. 12 (December 2017): 1248–62. http://dx.doi.org/10.1139/cjes-2017-0059.
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The higher taxonomic affinities of fin spines from the Lower Devonian (Emsian) Atholville beds, Campbellton Formation, near Campbellton, New Brunswick, Canada, originally identified as Ctenacanthus latispinosus, have been uncertain since they were first described by Whiteaves in the late 19th century. Woodward subsequently referred the species to Climatius, because the isolated Canadian fin spines were similar to those preserved in articulated specimens of Climatius reticulatus from the Lower Old Red Sandstone (Lochkovian) of Scotland. Spines of the same form as the Atholville beds specimens are also found in Emsian mudstones on the Gaspé Peninsula, Québec. One of the fin spine forms appears identical to the pectoral fin spines on an articulated specimen from the Campbellton Formation that has been assigned to the stem chondrichthyan Doliodus problematicus, a taxon erected for isolated diplodont teeth. By comparison with median and paired fin spine morphology on the climatiiform Climatius reticulatus from the Scottish Lower Old Red Sandstone and the spines preserved on the articulated Doliodus, isolated fin spines from Campbellton and several localities on the Gaspé Peninsula are now identified as belonging to Doliodus latispinosus comb. nov. The variety of spine morphotypes recognized—pectoral, prepelvic, prepectoral, and median—support a phylogenetic position within the “acanthodians” rather than “conventionally defined chondrichthyans”.
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Verde, Cinzia, M. Cristina De Rosa, Daniela Giordano, Donato Mosca, Donatella De Pascale, Luca Raiola, Ennio Cocca, Vitale Carratore, Bruno Giardina, and Guido Di Prisco. "Structure, function and molecular adaptations of haemoglobins of the polar cartilaginous fish Bathyraja eatonii and Raja hyperborea." Biochemical Journal 389, no. 2 (July 5, 2005): 297–306. http://dx.doi.org/10.1042/bj20050305.
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Cartilaginous fish are very ancient organisms. In the Antarctic sea, the modern chondrichthyan genera are poorly represented, with only three species of sharks and eight species of skates; the paucity of chondrichthyans is probably an ecological consequence of unusual trophic or habitat conditions in the Southern Ocean. In the Arctic, there are 26 species belonging to the class Chondrichthyes. Fish in the two polar regions have been subjected to different regional histories that have influenced the development of diversity: Antarctic marine organisms are highly stenothermal, in response to stable water temperatures, whereas the Arctic communities are exposed to seasonal temperature variations. The structure and function of the oxygen-transport haem protein from the Antarctic skate Bathyraja eatonii and from the Arctic skate Raja hyperborea (both of the subclass Elasmobranchii, order Rajiformes, family Rajidae) is reported in the present paper. These species have a single major haemoglobin (Hb 1; over 80% of the total). The Bohr-proton and the organophosphate-binding sites are absent. Thus the haemoglobins of northern and southern polar skates appear functionally similar, whereas differences were observed with several temperate elasmobranchs. Such evidence suggests that, in temperate and polar habitats, physiological adaptations have evolved along distinct pathways, whereas, in this case, the effect of the differences characterizing the two polar environments is negligible.
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Fahmi. "SHARKS AND RAYS IN INDONESIA." Marine Research in Indonesia 35, no. 1 (September 17, 2014): 43–54. http://dx.doi.org/10.14203/mri.v35i1.5.
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Indonesia is considered to have a high diversity of sharks and rays due in part to its position in the equatorial line, between two continents and two oceans. According to recent studies and various publications, the number of chondrichthyan species known to date is 207 species of 44 families, comprised of 109 species of sharks, 96 species of batoids, and two species of ghost sharks (chimaera). The Dasyatidae (stingrays) is the most speciose family of chondrichthyans occurring in Indonesia, followed by the Carcharhinidae (whaler sharks). Most species of elasmobranchs commonly occur on the continental or insular shelves and rays are more commonly found than sharks. This type of habitat can be found mostly in the western part of Indonesia (the Java Sea, Karimata Strait, South China Sea, Malacca Strait, and Macassar Strait). Due to the separation by the Wallace Line, there are some differences in species diversity between western and eastern region. The shark and ray fauna of the eastern region is more similar to the Australian fauna, while the fauna in the western region is more similar to the Asian fauna. There are also some endemic species known to occur in Indonesian waters. The endemicity of some species can be restricted in a certain area or in a regional area such as the Indo-West Pacific.
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Becker, Martin A., Robert W. Wellner, Christopher S. Mallery, and John A. Chamberlain. "Chondrichthyans from the Lower Ferron Sandstone Member of the Mancos Shale (Upper Cretaceous: Middle Turonian) of Emery and Carbon Counties, Utah, USA." Journal of Paleontology 84, no. 2 (March 2010): 248–66. http://dx.doi.org/10.1666/09-053r.1.
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The Lower Ferron Sandstone Member of the Mancos Shale in southeastern Utah preserves a chondrichthyan assemblage of at least 13 taxa that include:Hybodussp.,Ptychoduscf.P. mammillarisAgassiz, 1843,Ptychodus whippleiMarcou, 1858, cf.Chiloscylliumsp.,Scapanorhynchus raphiodon(Agassiz, 1843),Cretodus crassidens(Dixon, 1850), cf.Leptostyraxsp., cf.Cretalamna appendiculata(Agassiz, 1835),Squalicoraxsp.,Pseudohypolophus mcnultyi(Thurmond, 1971),Protoplatyrhina hopiiWilliamson, Kirkland and Lucas, 1993,Ischyrhiza schneideri(Slaughter and Steiner, 1968), andPtychotrygon triangularis(Reuss, 1844). Although this assemblage is typical of other Turonian chondrichthyan faunas in North America, fossil teeth are preserved in two unique facies associations that consist of arenitic sandstones with mud interclasts and rounded chert, feldspar, and quartz pebbles. the coarser beds within these facies associations are previously interpreted to represent storm events and turbidity flows associated with a sea level lowstand. Chondrichthyan teeth occurring within these coarser beds are indicative of extensive transport and reworking and attest to the durable nature of chondrichthyan teeth for biostratigraphic and paleoecological interpretations. Similar studies of chondrichthyan teeth in shelf marine settings may also provide new insights for facies interpretations related to sequence stratigraphy and regional stratigraphic correlations.
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Andreev, Plamen, Michael I. Coates, Valentina Karatajūtė-Talimaa, Richard M. Shelton, Paul R. Cooper, Nian-Zhong Wang, and Ivan J. Sansom. "The systematics of the Mongolepidida (Chondrichthyes) and the Ordovician origins of the clade." PeerJ 4 (June 16, 2016): e1850. http://dx.doi.org/10.7717/peerj.1850.
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The Mongolepidida is an Order of putative early chondrichthyan fish, originally erected to unite taxa from the Lower Silurian of Mongolia. The present study reassesses mongolepid systematics through the examination of the developmental, histological and morphological characteristics of scale-based specimens from the Upper Ordovician Harding Sandstone (Colorado, USA) and the Upper Llandovery–Lower Wenlock Yimugantawu (Tarim Basin, China), Xiushan (Guizhou Province, China) and Chargat (north-western Mongolia) Formations. The inclusion of the Mongolepidida within the Class Chondrichthyes is supported on the basis of a suite of scale attributes (areal odontode deposition, linear odontocomplex structure and lack of enamel, cancellous bone and hard-tissue resorption) shared with traditionally recognized chondrichthyans (euchondrichthyans, e.g., ctenacanthiforms). The mongolepid dermal skeleton exhibits a rare type of atubular dentine (lamellin) that is regarded as one of the diagnostic features of the Order within crown gnathostomes. The previously erected Mongolepididae and Shiqianolepidae families are revised, differentiated by scale-base histology and expanded to include the generaRongolepisandXinjiangichthys, respectively. A newly described mongolepid species (Solinalepis levisgen. et sp. nov.) from the Ordovician of North America is treated as familyincertae sedis, as it possesses a type of basal bone tissue (acellular and vascular) that has yet to be documented in other mongolepids. This study extends the stratigraphic and palaeogeographic range of Mongolepidida and adds further evidence for an early diversification of the Chondrichthyes in the Ordovician Period, 50 million years prior to the first recorded appearance of euchondrichthyan teeth in the Lower Devonian.
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Pose-Méndez, Sol, Isabel Rodríguez-Moldes, Eva Candal, Sylvie Mazan, and Ramón Anadón. "A Developmental Study of the Cerebellar Nucleus in the Catshark, a Basal Gnathostome." Brain, Behavior and Evolution 89, no. 1 (2017): 1–14. http://dx.doi.org/10.1159/000453654.
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The output of the cerebellar cortex is mainly released via cerebellar nuclei which vary in number and complexity among gnathostomes, extant vertebrates with a cerebellum. Cartilaginous fishes, a basal gnathostome lineage, show a conspicuous, well-organized cerebellar nucleus, unlike ray-finned fishes. To gain insight into the evolution and development of the cerebellar nucleus, we analyzed in the shark Scyliorhinus canicula (a chondrichthyan model species) the developmental expression of several genes coding for transcription factors (ScLhx5,ScLhx9,ScTbr1, and ScEn2) and the distribution of the protein calbindin, since all appear to be involved in cerebellar nuclei patterning in other gnathostomes. Three regions (subventricular, medial or central, and lateral or superficial) became recognizable in the cerebellar nucleus of this shark during development. Present genoarchitectonic and neurochemical data in embryos provide insight into the origin of the cerebellar nucleus in chondrichthyans and support a tripartite mediolateral organization of the cerebellar nucleus, as previously described in adult sharks. Furthermore, the expression pattern of ScLhx5,ScLhx9, and ScTbr1 in this shark, together with that of markers of proliferation, migration, and early differentiation of neurons, is compatible with the hypothesis that, as in mammals, different subsets of cerebellar nucleus neurons are originated from progenitors of 2 different sources: the ventricular zone of the cerebellar plate and the rhombic lip. We also present suggestive evidence that Lhx9 expression is involved in cerebellar nuclei patterning early on in gnathostome evolution, rather than representing an evolutionary innovation of the dentate nucleus in mammals, as previously hypothesized.
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Welten, Monique, Moya Meredith Smith, Charlie Underwood, and Zerina Johanson. "Evolutionary origins and development of saw-teeth on the sawfish and sawshark rostrum (Elasmobranchii; Chondrichthyes)." Royal Society Open Science 2, no. 9 (September 2015): 150189. http://dx.doi.org/10.1098/rsos.150189.
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A well-known characteristic of chondrichthyans (e.g. sharks, rays) is their covering of external skin denticles (placoid scales), but less well understood is the wide morphological diversity that these skin denticles can show. Some of the more unusual of these are the tooth-like structures associated with the elongate cartilaginous rostrum ‘saw’ in three chondrichthyan groups: Pristiophoridae (sawsharks; Selachii), Pristidae (sawfish; Batoidea) and the fossil Sclerorhynchoidea (Batoidea). Comparative topographic and developmental studies of the ‘saw-teeth’ were undertaken in adults and embryos of these groups, by means of three-dimensional-rendered volumes from X-ray computed tomography. This provided data on development and relative arrangement in embryos, with regenerative replacement in adults. Saw-teeth are morphologically similar on the rostra of the Pristiophoridae and the Sclerorhynchoidea, with the same replacement modes, despite the lack of a close phylogenetic relationship. In both, tooth-like structures develop under the skin of the embryos, aligned with the rostrum surface, before rotating into lateral position and then attaching through a pedicel to the rostrum cartilage. As well, saw-teeth are replaced and added to as space becomes available. By contrast, saw-teeth in Pristidae insert into sockets in the rostrum cartilage, growing continuously and are not replaced. Despite superficial similarity to oral tooth developmental organization, saw-tooth spatial initiation arrangement is associated with rostrum growth. Replacement is space-dependent and more comparable to that of dermal skin denticles. We suggest these saw-teeth represent modified dermal denticles and lack the ‘many-for-one’ replacement characteristic of elasmobranch oral dentitions.
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Johri, Shaili, Michael Doane, Lauren Allen, and Elizabeth Dinsdale. "Taking Advantage of the Genomics Revolution for Monitoring and Conservation of Chondrichthyan Populations." Diversity 11, no. 4 (March 29, 2019): 49. http://dx.doi.org/10.3390/d11040049.
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Chondrichthyes (sharks, rays, skates and chimaeras) are among the oldest extant predators and are vital to top-down regulation of oceanic ecosystems. They are an ecologically diverse group occupying a wide range of habitats and are thus, exploited by coastal, pelagic and deep-water fishing industries. Chondrichthyes are among the most data deficient vertebrate species groups making design and implementation of regulatory and conservation measures challenging. High-throughput sequencing technologies have significantly propelled ecological investigations and understanding of marine and terrestrial species’ populations, but there remains a paucity of NGS based research on chondrichthyan populations. We present a brief review of current methods to access genomic and metagenomic data from Chondrichthyes and discuss applications of these datasets to increase our understanding of chondrichthyan taxonomy, evolution, ecology and population structures. Last, we consider opportunities and challenges offered by genomic studies for conservation and management of chondrichthyan populations.
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Leonetti, Francesco Luigi, Emilio Sperone, Andrea Travaglini, Angelo R. Mojetta, Marco Signore, Peter N. Psomadakis, Thaya M. Dinkel, and Massimiliano Bottaro. "Filling the Gap and Improving Conservation: How IUCN Red Lists and Historical Scientific Data Can Shed More Light on Threatened Sharks in the Italian Seas." Diversity 12, no. 10 (October 10, 2020): 389. http://dx.doi.org/10.3390/d12100389.
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Chondrichthyans are one of the most threatened marine taxa worldwide. This is also the case in the Mediterranean Sea, which is considered an extinction hotspot for rays and sharks. The central position of the Italian peninsula makes it an ideal location for studying the status and changes of this sea. There is a lack of biological, ecological and historical data when assessing shark populations, which is also highlighted in the Red List of Threatened Species compiled by the International Union for the Conservation of Nature (IUCN). Historical data can provide important information to better understand how chondrichthyan populations have changed over time. This study aims to provide a clearer understanding of the changes in distribution and abundance of eight shark species in the Italian seas that are currently classified as at risk of extinction by the IUCN. In this respect, a bibliographic review was conducted on items from the 19th century to the first half of the 20th century, focusing on the selected species. The results show that all sharks were considered common until the beginning of the 20th century but have declined since, with a clear negative trend, mainly in the past 70 years. The strong local decline has been attributed to overexploitation, bycatch, habitat loss, depletion of prey items and environmental pollution. Furthermore, historical data also allow us to avoid the issue of a ‘shifting baseline’, in which contemporary abundances are assumed to be “normal”. Using historical data to further our knowledge of the marine environment is becoming increasingly common, and is fundamental in understanding human impact and evaluating mitigation measures to manage and conserve marine species and environments.
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Ward, Robert D., Bronwyn H. Holmes, William T. White, and Peter R. Last. "DNA barcoding Australasian chondrichthyans: results and potential uses in conservation." Marine and Freshwater Research 59, no. 1 (2008): 57. http://dx.doi.org/10.1071/mf07148.
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DNA barcoding – sequencing a region of the mitochondrial cytochrome c oxidase 1 gene (cox1) – promises a rapid and accurate means of species identification, and of any life history stage. For sharks and rays, it may offer a ready means of identifying legal or illegal shark catches, including shark fins taken for the profitable shark fin market. Here it is shown that an analysis of sequence variability in a 655 bp region of cox1 from 945 specimens of 210 chondrichthyan species from 36 families permits the discrimination of 99.0% of these species. Only the two stingarees Urolophus sufflavus and U. cruciatus could not be separated, although these could be readily distinguished from eight other congeners. The average Kimura 2 parameter distance separating individuals within species was 0.37%, and the average distance separating species within genera was 7.48%. Two specimens that clustered with congeners rather than with their identified species-cluster were noted: these could represent instances of hybridisation (although this has not be documented for chondrichthyans), misidentification or mislabelling. It is concluded that cox1 barcoding can be used to identify shark and ray species with a very high degree of accuracy. The sequence variability characteristics of individuals of five species (Aetomylaeus nichofii, Dasyatis kuhlii, Dasyatis leylandi, Himantura gerrardi and Orectolobus maculatus) were consistent with cryptic speciation, and it is suggested that these five taxa be subjected to detailed taxonomic examination to confirm or refute this suggestion. The present barcoding study holds out great hope for the ready identification of sharks, shark products and shark fins, and also highlights some taxonomic issues that need to be investigated further.
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Mull, Christopher G., Kara E. Yopak, and Nicholas K. Dulvy. "Does more maternal investment mean a larger brain? Evolutionary relationships between reproductive mode and brain size in chondrichthyans." Marine and Freshwater Research 62, no. 6 (2011): 567. http://dx.doi.org/10.1071/mf10145.
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Chondrichthyans have the most diverse array of reproductive strategies of any vertebrate group, ranging from egg-laying to live-bearing with placental matrotrophy. Matrotrophy is defined as additional maternal provisioning beyond the yolk to the developing neonate; in chondrichthyans, this occurs through a range of mechanisms including uterine milk, oophagy, uterine cannibalism and placentotrophy. Chondrichthyans also exhibit a wide range of relative brain sizes and highly diverse patterns of brain organisation. Brains are energetically expensive to produce and maintain, and represent a major energetic constraint during early life in vertebrates. In mammals, more direct maternal–fetal placental connections have been associated with larger brains (steeper brain–body allometric scaling relationships). We test for a relationship between reproductive mode and relative brain size across 85 species from six major orders of chondrichthyans by using several phylogenetic comparative analyses. Ordinary least-squares (OLS) and reduced major axis (RMA) regression of body mass versus brain mass suggest that increased maternal investment results in a larger relative brain size. Our findings were supported by phylogenetic generalised least-squares models (pGLS), which also highlighted that these results vary with evolutionary tempo, as described by different branch-length assumptions. Across all analyses, maximum body size had a significant influence on the relative brain size, with large-bodied species (body mass >100 kg) having relatively smaller brains. The present study suggests that there may be a link between reproductive investment and relative brain size in chondrichthyans; however, a more definitive test requires a better-resolved phylogeny and a more nuanced categorisation of the level of maternal investment in chondrichthyans.
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Perez, Victor J., Catalina Pimiento, Austin Hendy, Gerardo González-Barba, Gordon Hubbell, and Bruce J. MacFadden. "Late Miocene chondrichthyans from Lago Bayano, Panama: Functional diversity, environment and biogeography." Journal of Paleontology 91, no. 3 (April 11, 2017): 512–47. http://dx.doi.org/10.1017/jpa.2017.5.
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AbstractThis newly described chondrichthyan fauna from the late Miocene Chucunaque Formation of Lago Bayano reveals a prolific and highly diverse assemblage from Panama, and one of the richest shark faunas from the Neotropics. Strontium geochronology indicates an age of 10–9.5 Ma for the chonrichthyan-bearing strata. Field efforts resulted in 1429 identifiable specimens comprising at least 31 taxa, of which at least eight are new to the documented fossil record of Panama. With this information an analysis of functional diversity was conducted, indicating ecosystems dominated by generalist species feeding upon a wide range of organisms, from plankton to marine mammals. A probabilistic approach of paleobathymetric estimation suggests a neritic environment. Previous studies based on foraminifera have suggested that the Chucunaque Formation had a greater Pacific Ocean affinity, making this the first Miocene chondrichthyan fauna described from the Pacific shelf of Panama. However, our geographic comparisons show that this fauna has mixed Caribbean and Pacific biogeographic affinities, which likely supports the previously purported connection between chondrichthyan faunas during the late Miocene.
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Mulley, John F., Ying-Fu Zhong, and Peter WH Holland. "Comparative genomics of chondrichthyan Hoxa clusters." BMC Evolutionary Biology 9, no. 1 (2009): 218. http://dx.doi.org/10.1186/1471-2148-9-218.
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Stingo, Vincenzo, and Lucia Rocco. "Chondrichthyan cytogenetics: A comparison with teleosteans." Journal of Molecular Evolution 33, no. 1 (July 1991): 76–82. http://dx.doi.org/10.1007/bf02100198.
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Villafaña, Jaime A., and Marcelo M. Rivadeneira. "The modulating role of traits on the biogeographic dynamics of chondrichthyans from the Neogene to the present." Paleobiology 44, no. 2 (March 21, 2018): 251–62. http://dx.doi.org/10.1017/pab.2018.7.
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AbstractThe environmental transformations that occurred during the Neogene had profound effects on spatiotemporal biodiversity patterns, yet the modulating role of traits (i.e., physiological, ecological, and life-history traits) remains little understood. We tested this idea using the Neogene fossil record of chondrichthyans along the temperate Pacific coast of South America (TPSA). Information for georeferenced occurrences and ecological and life-history information of 38 chondrichthyan fossil genera in 42 Neogene sites was collected. Global georeferenced records were used to estimate present-day biogeographic distributions of the genera and to characterize the range of oceanographic conditions in which each genus lives as a proxy of their realized niche. Biogeographic range shifts (Neogene–present) were evaluated at regional and local scales. The role of traits as drivers of different range dynamics was evaluated using random forest models. The magnitude and direction of biogeographic range shifts were different at both spatial scales. At a regional scale, 34% of genera contracted their ranges, disappearing from the TPSA. At a local scale, a similar proportion of genera expanded and contracted their southern endpoints of distribution. The models showed a high precision at both spatial scales of analyses, but the relative importance of predictor variables differed. At a regional scale, disappearing genera tended to have a higher tolerance to salinity, lower sea surface temperature (SST) range, and smaller body sizes. At a local scale, genera contracting their ranges tended to live at greater depths, tolerate lower levels of primary productivity, and show a reduced tolerance to higher and lower SST ranges. The magnitude and direction of the changes in the range distribution were scale dependent and variable across the genera. Hence, multiple environmental exogenous factors interacted with taxon traits during the Neogene, creating a mosaic of biogeographic dynamics.
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Ginter, Michał, Sofie Gouwy, and Stijn Goolaerts. "A classic Late Frasnian chondrichthyan assemblage from southern Belgium." Acta Geologica Polonica 67, no. 3 (September 26, 2017): 381–92. http://dx.doi.org/10.1515/agp-2017-0017.
Full textAbstract:
AbstractSamples from the Upper Frasnian (Devonian) of Lompret Quarry and Nismes railway section in Dinant Synclinorium, southern Belgium, yielded several chondrichthyan teeth and scales. The teeth belong to three genera: Phoebodus, Cladodoides and Protacrodus. The comparison with selected Late Frasnian chondrichthyan assemblages from the seas between Laurussia and Gondwana revealed substantial local differences of taxonomic composition due to palaeoenvironmental conditions, such as depth, distance to submarine platforms, oxygenation of water, and possibly also temperature. The assemblage from Belgium, with its high frequency of phoebodonts, is the most similar to that from the Ryauzyak section, South Urals, Russia, and the Horse Spring section, Canning Basin, Australia.
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Gaudin, Timothy J. "A re-examination of Elasmobranch monophyly and Chondrichthyan phylogeny." Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen 182, no. 2 (June 10, 1991): 133–60. http://dx.doi.org/10.1127/njgpa/182/1991/133.
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Wyffels, Jennifer, Benjamin L. King, James Vincent, Chuming Chen, Cathy H. Wu, and Shawn W. Polson. "SkateBase, an elasmobranch genome project and collection of molecular resources for chondrichthyan fishes." F1000Research 3 (August 12, 2014): 191. http://dx.doi.org/10.12688/f1000research.4996.1.
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Chondrichthyan fishes are a diverse class of gnathostomes that provide a valuable perspective on fundamental characteristics shared by all jawed and limbed vertebrates. Studies of phylogeny, species diversity, population structure, conservation, and physiology are accelerated by genomic, transcriptomic and protein sequence data. These data are widely available for many sarcopterygii (coelacanth, lungfish and tetrapods) and actinoptergii (ray-finned fish including teleosts) taxa, but limited for chondrichthyan fishes. In this study, we summarize available data for chondrichthyes and describe resources for one of the largest projects to characterize one of these fish, Leucoraja erinacea, the little skate. SkateBase (http://skatebase.org) serves as the skate genome project portal linking data, research tools, and teaching resources.
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Hodnett, John-Paul M., and David K. Elliott. "Carboniferous chondrichthyan assemblages from the Surprise Canyon and Watahomigi formations (latest Mississippian–Early Pennsylvanian) of the western Grand Canyon, Northern Arizona." Journal of Paleontology 92, S77 (December 2018): 1–33. http://dx.doi.org/10.1017/jpa.2018.72.
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AbstractTwo chondrichthyan assemblages of Late Mississippian/Early Pennsylvanian age are now recognized from the western Grand Canyon of northern Arizona. The latest Serpukhovian Surprise Canyon Formation has yielded thirty-one taxa from teeth and dermal elements, which include members of the Phoebodontiformes, Symmoriiformes, Bransonelliformes, Ctenacanthiformes, Protacrodontoidea, Hybodontiformes, Neoselachii (Anachronistidae), Paraselachii (Gregoriidae, Deeberiidae, Orodontiformes, and Eugeneodontiformes), Petalodontiformes, and Holocephali. The euselachian grade taxa are remarkably diverse with four new taxa recognized here; the Protacrodontidae:Microklomax carrieaenew genus new species andNovaculodus billingsleyinew genus new species, and the Anchronistidae:Cooleyella plateranew species andAmaradontus santuciinew genus new species The Surprise Canyon assemblage also has the youngest occurrence of the elasmobranchClairina, previously only known from the Upper Devonian. The Surprise Canyon Formation represents a nearshore fluvial infilling of karstic channels, followed by a shallow marine bioherm reef, and finally deeper open water deposition. The early Bashkirian Watahomigi Formation represents open marine deposition and contains only two taxa: a new xenacanthiform,Hokomata parvanew genus new species, and the holocephalanDeltodus. The relationship between the Surprise Canyon and Watahomigi chondrichthyan assemblages and other significant coeval chondrichthyan assemblages suggests that there may have been eastern and western distinctions among the Euamerican assemblages during the Serpukhovian due to geographic separation by the formation of Pangea.UUID:http://zoobank.org/54a906b6-4873-4f84-92b5-ca0752de01aa
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Last, P. R., and W. T. White. "Biogeographic patterns in the Australian chondrichthyan fauna." Journal of Fish Biology 79, no. 5 (September 19, 2011): 1193–213. http://dx.doi.org/10.1111/j.1095-8649.2011.03095.x.
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Walker, Terence I. "The state of research on chondrichthyan fishes." Marine and Freshwater Research 58, no. 1 (2007): 1. http://dx.doi.org/10.1071/mf06223.
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Last, Peter R. "The state of chondrichthyan taxonomy and systematics." Marine and Freshwater Research 58, no. 1 (2007): 7. http://dx.doi.org/10.1071/mf07003.
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Derycke, Claire, Claudia Spalletta, Maria Cristina Perri, and Carlo Corradini. "Famennian chondrichthyan microremains from Morocco and Sardinia." Journal of Paleontology 82, no. 5 (September 2008): 984–95. http://dx.doi.org/10.1666/07-102.1.
Full textAbstract:
New material from the Famennian of Morocco in the southern Maider comprises chondrichthyan teeth(Thrinacodus, Cobelodus, Denaea, Stethacanthus), actinopterygian remains (scales, teeth and hemilepidotrichium) and one acanthodian scale. The absence of crushing teeth suggests deeper water environments for the Maider Basin than the Tafilalt Basin. Vertebrate microremains from the Famennian of Sardinia, includingSiamodusandJalodusteeth, are illustrated and described. Ichthyofaunal relationships of the North Gondwanan platform during the Famennian are examined.