Fishes Flashcards
What are the 6 Gnathostome synapomorphies?
jaws (derived from gill arches), most have dentin-based teeth, complex endoskeleton, 3 semi-circular canals, paired fins/limbs, gill tissue external to gill arches
What did Gnathostome jaws evolve from?
2 pharyngeal (branchial) arches - first arch becomes mandibular arch, 2nd arch becomes hyoid arch
What are placoderms?
extinct group of jawed fishes (430-359 Ma)
Where is placoderm armor located?
cranial and thoracic bony armor
T/F: Placoderms have teeth
False: jaws lined with self-sharpening occluding bony plates (no teeth)
What is donkleosteus?
predatory placoderm found in North America, Poland, Belgium, Morocco
- massive: 10m long, 4 tonnes
what is materpiscis (mother fish)
oldest known vertebrate to show matrotrophic viviparity (nutrition from mother and birth to live young). bears unborn embryo and mineralized umbilical cord
what are Acanthodians?
extinct group of paleozoic jawed fishes (450-290 Ma)
What are some features of acanthodians(spiny sharks)?
prominent spines at leading edges of fins, body covered in small non-overlapping rhomboid scales, single or multiple gill covers (operculum), large eyes
what are chondrichthyans?
cartilagenous fishes, fossil record extends back to paleozoic
what kind of jaw suspension do sharks have?
hyostylic jaw suspension; upper jaw has a weak ligamentous attachment to braincase and is mostly supported by the hyoid arch
what is the benefit of hyostylic jaw suspension
produces greater mobility of jaws and development of a protractile bite (increases ability to tear off large pieces of flesh or provide effective suction)
what are some features of sharks (chondrichthyans)?
active predators, cartilagenous endoskeleton, dermal skeleton composed of placoid scales (protection and reduce friction), fins composed of keratinized ceratotrichia
T/F: all extinct and extant male sharks have claspers
true
what function does the rectal gland serve?
osmoregulation: removes excess salt
what function does the liver serve in sharks?
replaces swim bladder, produces and stores squalene that reduces body density.
lighter than water - specific gravity of 0.85
what is dynamic lift?
heteroceral tail pushes water posteriorly and ventrally producing a reaction forces with dorsal lift and anterior thrust components
flat ventral body and pectoral fins also produce lift
what kind of jaw suspension do Batoids (rays) have?
euhyostylic jaw suspension (suspended solely by the hyoid arch)
what are some features of batoids?
dorsoventrally flattened
expanded pectoral fins fused to head
eyes and enlarged spiracle are placed dorsally, mouth and gill slits placed ventrally
what kind of jaw suspension do holocephalans have?
hyostylic (palatoquadrate fused to chondrocranium and not supported by hyomandibular)
What are some features of holocephalans?
cartilaginous endoskeleton (males have claspers)
tooth plates
operculum covering gill arches
narrow whip-like tail
swim via rowing action of pectoral fins
what are actinopterygians?
ray-finned fishes: fins fully “rayed” from base with bony lepidotrichia
fossil record dates back to Paleozoic
what are chondrosteans?
primitive actinopterygians
used to be large group now only paddlefish and sturgeons
what are some features of chondrosteans?
mostly cartilaginous endoskeleton, ganoid scales, unconstricted notochord, heteroceral tail, vascularized physostomous swim bladder
what are holosteans?
intermediate actinopterygians
dated back to late permian
what are some features of holosteans
heavily armored with ganoid scales, elongated body with heteroceral tail, posterior dorsal and anal fins, physostomous swim bladders, moderate ossification of endoskeleton
what are teleosts?
derived actinoperygians
95% of all living fishes (more species than all other vertebrate classes combined)
first appeared in mid triassic - explosive radiation during jurassic
what is the feeding mechanism for teleosts?
highly mobile upper jaw
rapid mouth opening creates negative pressure in the oral cavity drawing food items into mouth
what function does the heteroceral tail serve?
provides dynamic lift for heavy primitive actinopterygians
how is vertical movement accomplished by primitive actinopterygians?
primarily by pectoral fins
what function does the teleost homoceral tail serve?
pushes water posteriorly producing a reaction force with anterior thrust component only
what are some advantages of the homoceral tail?
increased efficiency in horizontal swimming (thrust is purely horizontal)
increased versatility (pectoral fins can take on other locomotory functions other than planing)
what are sarcopterygians?
lobe-finned fishes
fossil record extends back to the Paleozoic
only 8 extant species
what are some features of sarcopterygians?
lobed fins resembling ancestral tertrapods
fin muscles external to the body wall
cosmoid scales, choanae, hinge like joint on top of skull, prominent notochord, diphyceral tail
what is the structure of cosmoid sclaes?
complex dentin-layer (cosmine) and an outer coating of enamel
what are choanae?
paired internal openings into the oropharyngeal cavity
what is Tiktaalik roseae?
transitional fishapod (intermediate between fish and amphibians
late devonian (375 Ma)
what are some features of tiktaalik roseae?
cosmoid scales, tetrapod-like limb bones and functional wrist joint, heavy endoskeleton with robust ribs, well-developed pectoral girdle separate from skull, hinge-like intracranial joint
