Fishes

Question 1

What are the 6 Gnathostome synapomorphies?

Answer 1

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

Question 2

What did Gnathostome jaws evolve from?

Answer 2

2 pharyngeal (branchial) arches - first arch becomes mandibular arch, 2nd arch becomes hyoid arch

Question 3

What are placoderms?

Answer 3

extinct group of jawed fishes (430-359 Ma)

Question 4

Where is placoderm armor located?

Answer 4

cranial and thoracic bony armor

Question 5

T/F: Placoderms have teeth

Answer 5

False: jaws lined with self-sharpening occluding bony plates (no teeth)

Question 6

What is donkleosteus?

Answer 6

predatory placoderm found in North America, Poland, Belgium, Morocco
- massive: 10m long, 4 tonnes

Question 7

what is materpiscis (mother fish)

Answer 7

oldest known vertebrate to show matrotrophic viviparity (nutrition from mother and birth to live young). bears unborn embryo and mineralized umbilical cord

Question 8

what are Acanthodians?

Answer 8

extinct group of paleozoic jawed fishes (450-290 Ma)

Question 9

What are some features of acanthodians(spiny sharks)?

Answer 9

prominent spines at leading edges of fins, body covered in small non-overlapping rhomboid scales, single or multiple gill covers (operculum), large eyes

Question 10

what are chondrichthyans?

Answer 10

cartilagenous fishes, fossil record extends back to paleozoic

Question 11

what kind of jaw suspension do sharks have?

Answer 11

hyostylic jaw suspension; upper jaw has a weak ligamentous attachment to braincase and is mostly supported by the hyoid arch

Question 12

what is the benefit of hyostylic jaw suspension

Answer 12

produces greater mobility of jaws and development of a protractile bite (increases ability to tear off large pieces of flesh or provide effective suction)

Question 13

what are some features of sharks (chondrichthyans)?

Answer 13

active predators, cartilagenous endoskeleton, dermal skeleton composed of placoid scales (protection and reduce friction), fins composed of keratinized ceratotrichia

Question 14

T/F: all extinct and extant male sharks have claspers

Answer 14

true

Question 15

what function does the rectal gland serve?

Answer 15

osmoregulation: removes excess salt

Question 16

what function does the liver serve in sharks?

Answer 16

replaces swim bladder, produces and stores squalene that reduces body density.
lighter than water - specific gravity of 0.85

Question 17

what is dynamic lift?

Answer 17

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

Question 18

what kind of jaw suspension do Batoids (rays) have?

Answer 18

euhyostylic jaw suspension (suspended solely by the hyoid arch)

Question 19

what are some features of batoids?

Answer 19

dorsoventrally flattened
expanded pectoral fins fused to head
eyes and enlarged spiracle are placed dorsally, mouth and gill slits placed ventrally

Question 20

what kind of jaw suspension do holocephalans have?

Answer 20

hyostylic (palatoquadrate fused to chondrocranium and not supported by hyomandibular)

Question 21

What are some features of holocephalans?

Answer 21

cartilaginous endoskeleton (males have claspers)
tooth plates
operculum covering gill arches
narrow whip-like tail
swim via rowing action of pectoral fins

Question 22

what are actinopterygians?

Answer 22

ray-finned fishes: fins fully “rayed” from base with bony lepidotrichia
fossil record dates back to Paleozoic

Question 23

what are chondrosteans?

Answer 23

primitive actinopterygians
used to be large group now only paddlefish and sturgeons

Question 24

what are some features of chondrosteans?

Answer 24

mostly cartilaginous endoskeleton, ganoid scales, unconstricted notochord, heteroceral tail, vascularized physostomous swim bladder

Question 25

what are holosteans?

Answer 25

intermediate actinopterygians dated back to late permian

Question 26

what are some features of holosteans

Answer 26

heavily armored with ganoid scales, elongated body with heteroceral tail, posterior dorsal and anal fins, physostomous swim bladders, moderate ossification of endoskeleton

Question 27

what are teleosts?

Answer 27

derived actinoperygians 95% of all living fishes (more species than all other vertebrate classes combined) first appeared in mid triassic - explosive radiation during jurassic

Question 28

what is the feeding mechanism for teleosts?

Answer 28

highly mobile upper jaw rapid mouth opening creates negative pressure in the oral cavity drawing food items into mouth

Question 29

what function does the heteroceral tail serve?

Answer 29

provides dynamic lift for heavy primitive actinopterygians

Question 30

how is vertical movement accomplished by primitive actinopterygians?

Answer 30

primarily by pectoral fins

Question 31

what function does the teleost homoceral tail serve?

Answer 31

pushes water posteriorly producing a reaction force with anterior thrust component only

Question 32

what are some advantages of the homoceral tail?

Answer 32

increased efficiency in horizontal swimming (thrust is purely horizontal) increased versatility (pectoral fins can take on other locomotory functions other than planing)

Question 33

what are sarcopterygians?

Answer 33

lobe-finned fishes fossil record extends back to the Paleozoic only 8 extant species

Question 34

what are some features of sarcopterygians?

Answer 34

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

Question 35

what is the structure of cosmoid sclaes?

Answer 35

complex dentin-layer (cosmine) and an outer coating of enamel

Question 36

what are choanae?

Answer 36

paired internal openings into the oropharyngeal cavity

Question 37

what is Tiktaalik roseae?

Answer 37

transitional fishapod (intermediate between fish and amphibians late devonian (375 Ma)

Question 38

what are some features of tiktaalik roseae?

Answer 38

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