Presentation on theme: "Chondrichthyes: sharks, skates, rays and chimeras Craig Kasper, Ph. D"— Presentation transcript:
1 Chondrichthyes: sharks, skates, rays and chimeras Craig Kasper, Ph. D Chondrichthyes: sharks, skates, rays and chimeras Craig Kasper, Ph. D. Zoology Chapter 12What’s a chimera??
2 Sharks: the beginning…or the end?? Existence of elasmobranchs with little change is a testament to their evolutionary success and durabilityAppear in fossil record in late Devonian, 500 mybp (perhaps earlier)Last class of fishes to appear in fossil recordElasmobranch…plate or strap gill
3 Classification of Chondrichthyes Class Chondrichthyes (~850 spp.)Subclass Elasmobranchi (~820 spp.)sharks, skates and raysSubclass Holocephali (~30 spp.)chimaeras, ratfishes
4 Distinguishing Elasmobranch Traits cartilaginous skeletonabsence of swim bladderheterocercal tailplacoid denticles - scales and teethspiracle present with 5-7 gill slits (no operculum)urea retained for osmoregulationspiral valve in intestinemales have clasper organs for internal fertilizationembryonic development with physiological careoviparous, ovoviviparous, viviparousjaw hyostylic (single connection of upper jaw to neurocranium - adds protrusibility) or amphistylic (two connection points - anterior and posterior)teeth in rows, are constantly replacedeyes small
5 Holocephali: traitsjaw holostylic (= autostylic = fused to neurocranium)spiracle absent; gills covered by single operculumall oviparouscloaca lacking - separate urogenital poreskin lacking scales; placoid spinesmales with head claspersteeth are plate-like, non-deciduouseyes large
6 Chondrichthian success story? Buoyancy control: fatty liver, no swim bladder and no energy requiredSwimming adaptations: rigid fins instead of raysBody covering: placoid scales, reduce drag (see Helfman, fig. 12.3)Osmoregulation adaptationsReproductive adaptations: self-sufficient youngFeeding adaptationsSensory system: tapetum lucetum, ampullae of LorenziniRespiration effectivenessHey, if it ain’t broke…
8 Elasmobranch classification Carcharhiniformes - requiem sharks (ground sharks) (blacktip, whitetip, reef, bull), tiger sharks, basking sharksGround sharks feature an anal fin, two dorsal fins, an elongated snout, and a long mouth that reaches behind the eyes, with teeth ranging from small and cuspidate to large and bladelike. They have a third eyelid as well.
20 Superorder Squalomorphi smaller, pelagic and benthic sharks, feed on smaller prey, some with pointed teeth, some with pavement teethSqualiformes - dogfish sharksHexanchiformes - six & seven-gill sharks (cow sharks)Pristiophoriformes - saw sharks
27 Skate or Ray...what’s the difference? Skates (order Rajiformes)pelvic fin divided into two lobes stocky tail w/o stinging spine enlarged, thorn-like scales ('bucklers') along the midline of backmales have rows of enlarged scales near the eyes and wingtipsRays (order Myliobatiformes):one-lobed pelvic fin whip-like tail, usually with stinging spine no bucklers along back or tail
30 Spotted ratfish Hydrolagus colliei Family: chimaeridaeIdentification: Broad, flat, duckbill shaped snout containing incisor shaped teeth. Prominent, venomous spine at leading edge of dorsal fin. Tapering tail constitutes almost half overall length. Coloration brown or grey with white spots. Skin smooth and scaleless. Can give off an iridescent, silvery sheen. Fins grey or dark.Size: up to 97cm in length.