the neurocranium (Nelson et al. 2016). There is no nictitating membrane and the cornea attaches directly to the skin around the eyes. The cranial vertebrae are fused with the pectoral girdle (synarcual). There is no anal fin. Most have one or more venomous spines (barbs) along the tail. Some key aquarium families are listed below.
Aetobatidae, Myliobatidae, Mobulidae, Rhinopteridae: eagle rays, mobulids, cownose rays. These have a small dorsal fin on the base of the tail. The head is elevated above the pectoral fins and the eyes and spiracles are lateral on head. Tooth‐plates are made up of six‐sided teeth in a horizontal arrangement. They are capable of leaping into the air. The mobulids, which include manta rays (Manta spp.), have cephalic lobes that are cranial extensions of the pectoral fins and assist in feeding. These animals also have gill rakers. Mobulids lack venomous barbs.
Dasyatidae: whiptail stingrays. These inhabit freshwater and saltwater habitats. They have a long and slender tail.
Potamotrygonidae: river stingrays. These are all freshwater species and show a reduced rectal gland. Their venom is more potent than saltwater species.
Torpediniformes (Electric Rays)
These are rays with strong electric organs derived from branchial musculature. They are dorsoventrally flattened with rounded pectoral fins. They are slow‐moving, and do not use their pectoral wings much for locomotion. The skin is soft with no denticles or thorns. Their eyes are very small. There is a well‐developed caudal fin (Nelson et al. 2016).
Pristiformes (Guitarfish and Sawfish)
Guitarfish (Rhinobatidae) have a stout tail, with two dorsal fins, and a caudal fin without a barb. Bowmouth guitarfish (Rhina ancylostoma) are similar but their tail is bilobed and their rostrum is unique. The sawfish (Pristidae), also known as carpenter sharks, have a rostrum shaped like a flat blade with non‐replaceable “teeth” (modified dermal denticles) embedded on the sides (Nelson et al. 2016). The mouth and nares are ventral. Oral dentition varies but teeth are mostly blunt‐edged “cobblestones” in rows. Spiracles are prominent. There are no anal fins.
Acknowledgments
Many thanks go to individuals who were instrumental in the management of this document: Carlos Rodriguez, Charlene Burns, Kevin Maxson, Shane Boylan, Jennifer Dill‐Okubo, and Catharine Wheaton.
References
1 Ali, M.A. and Anctil, M. (2012). Retinas of Fishes: An Atlas. New York: Springer Science and Business Media.
2 Anderson, G. (2015). Endocrine systems in elasmobranchs. In: Physiology of Elasmobranch Fishes: Internal Processes, vol. 34B (eds. E. Shadwick, A. Farrell and C. Brauner), 457–530. Amsterdam: Elsevier, Inc.
3 Anderson, P.A., Huber, D.R., and Berzins, I.K. (2012). Correlations of capture, transport, and nutrition with spinal deformities in sandtiger sharks, Carcharias taurus, in public aquaria. Journal of Zoo and Wildlife Medicine 43: 750–758.
4 Angelidis, P., Vatsos, N.I., and Karagiannis, D. (2009). Surgical excision of skin folds from the head of a goldfish Carassius auratus (Linnaeus 1758). Journal of the Hellenic Veterinay Medical Society 58: 299–305.
5 Ashhurst, M.E. (2004). The cartilaginous skeleton of an elasmobranch fish does not heal. Matrix Biology 23: 15–22.
6 Ashley, L.M. and Chiasson, R.B. (1988). Laboratory Anatomy of the Shark. California: W.C. Brown Co. Publishers.
7 Atkinson, C.J. and Collin, S.P. (2012). Structure and topographic distribution of oral denticles in elasmobranch fishes. The Biological Bulletin 222: 26–34.
8 Awruch, C.A. (2016). Reproduction strategies. In: Fish Physiology, vol. 34A (eds. A.P. Farell and C.J. Brauner), 255–310. Amsterdam: Elsevier, Inc.
9 Ballantyne, J.S. and Robinson, J.W. (2010). Freshwater elasmobranchs: a review of their physiology and biochemistry. Journal of Comparative Physiology B 180 (4): 475–493.
10 Berkovitz, B.K. and Shellis, R.P. (2016). The Teeth of Non‐mammalian Vertebrates. Amsterdam: Academic Press, Elsevier, Inc.
11 Bernal, D., Carlson, J.K., Goldman, K.J., and Lowe, C.G. (2012). Energetics, metabolism, and endothermy in sharks and rays. In: Biology of Sharks and their Relatives, 2e (eds. J.C. Carrier, J.A. Musick and M.R. Heithaus), 211–237. Boca Raton, FL: CRC Press.
12 Bertin, L. (1958). Organes de la respiration aquatique. In: Traité de Zoologie, vol. XIII (ed. P. Grassé), 1301–1341. Paris: Masson Publishing.
13 Blaxter, J.H.S. and Batty, R.S. (1990). Swimbladder “behaviour” and target strength. Rapports et Proces‐verbaux des Réunions du Conseil International pour l’Exploration de la Mer 189: 233–244.
14 Block, B.A. and Finnerty, J.R. (1994). Endothermy in fishes: a phylogenetic analysis of constraints, predispositions, and selection pressures. Environmental Biology of Fishes 40: 283–302.
15 Borucinska, J.D., Harshbarger, J.C., Reimschuessel, R., and Bogicevic, T. (2004). Gingival neoplasms in a captive sand tiger shark, Carcharias taurus (Rafinesque), and a wild‐caught blue shark, Prionace glauca (L.). Journal of Fish Diseases 27: 185–191.
16 Bowden, T.J., Cook, P., and Rombout, J.H.W.M. (2005). Development and function of the thymus in teleosts. Fish & Shellfish Immunology 19: 413–427.
17 Bradbury, M. (1979). Why a blood‐brain barrier? Trends in Neurosciences 2: 36–38.
18 Branson, E.J. (ed.) (2008). Fish Welfare. Ames, IA: Wiley.
19 Bruton, M.N. (1996). Alternative life‐history strategies of catfishes. Aquatic Living Resources 9: 35–41.
20 Buddington, R.K. and Diamond, J.M. (2016). Aristotle revisited: the function of pyloric caeca in fish. Proceedings of the National Academy of Sciences 83: 8012–8014.
21 Bundgaard, M. and Abbott, N.J. (2008). All vertebrates started out with a glial blood‐brain barrier 4‐500 million years ago. Glia 56: 699–708.
22 Burgess, S.C., Wang, J., Etoundi, A. et al. (2011). A functional analysis of the jaw mechanism in the sling‐jaw wrasse. International Journal of Design & Nature and Ecodynamics 6: 258–271.
23 Butler, P. (1999). Respiratory system. In: Sharks, Skates, and Rays: The Biology of Elasmobranch Fishes (ed. W.C. Hamlett), 174–197. Baltimore, MD: JHU Press.
24 Camhi, M.D., Pikitch, E.K., and Babcock, E.A. (eds.) (2008). Sharks of the Open Ocean: Biology, Fisheries & Conservation. Ames, IA: Blackwell Publishing.
25 Carrier, J.C., Musick, J.A., and Heithaus, M.R. (eds.) (2012). Biology of Sharks and Their Relatives II: Biodiversity, Adaptive Physiology, and Conservation. Baton Raton, FL: CRC Press.
26 Caruso, M.A. and Sheridan, M.A. (2011). Pancreas. In: Encyclopedia of Fish Physiology: From Genome to Environment (ed. A.P. Farrell), 1286–1293. Amsterdam: Academic Press, Elsevier, Inc.
27 Castro, J.I., Sato, K., and Bodine, A.B. (2016). A novel mode of embryonic nutrition in the tiger shark, Galeocerdo cuvier. Marine Biology Research 12: 200–205.
28 Colicchia, G. (2007). Vision of fish in air. Physics Education 42: 1876–1883.
29 De Iuliis, G. and Pulerà, D. (2011). The Dissection of Vertebrates: A Laboratory Manual, 2e. Amsterdam: Academic Press, Elsevier, Inc.
30 Dean, M.N. and Summers, A.P. (2006). Mineralized cartilage in the skeleton of chondrichthyan fishes. Zoology 109: 164–168.
31 Didier, D.A. (2004). Phylogeny and classification of extant Holocephali. In: Biology of Sharks and Their Relatives, 1e (eds. J.C. Carrier, J.A. Musick and M.R. Heithaus), 115–138. Boca Raton, FL: CRC Press.
32 Douglas, R. and Djamgoz, M. (eds.) (2012). The Visual System of Fish. New York: Springer Science