Evolution and Diversity of Fishes Flashcards
T or F: Agnatha are considered the jawless fishes
True - have a mouth that opens but no biting apparatus
Which groups belong to the jawless agnathans?
- cyclostomes: lampreys and hagfishes (extant)
- conodonts and ostracoderms (extinct)
Briefly describe the characteristics of the hagfishes
- scavengers
- cartilaginous plate and skull
- no jaws, fins, image-forming eyes
- multiple hearts
- single nostril
- slime glands
- basic vertebrae
Briefly describe the characteristics of the lampreys
- metamorphosis: ammoecete larva into adult form
- cartilaginous skull and vertebrae
- no jaws
- has fins
- single nostril
- image-forming eyes
- parasitic
Briefly describe characteristics of the ostracoderms
- no jaw
- lateral line system
- dermal bone plates=exoskeleton
- appeared in Ordovician and extinct in Devonian
What structure did jaws evolve from?
Bonus: What are the upper and lower elements?
-evolved from first branchial arch
Bonus:
Upper: palatoquadrate
Lower: Meckel’s cartilage/mandible
What’s so significant about the evolution of jaws?
Allowed for:
- new diets
- new feeding techniques
- built on predatory lifestyle
- aided in respiration in more active lifestyles
What three groups make up the gnathostomes?
- placodermi
- chonrichthyes
- osteichthyes
What are some characteristics of chondrichthyes?
- cartilaginous fishes
- placoid scales
- internal fertilization
- spiracle -> highly specialized
What three groups are in chrondrichthyes?
- chimaeras
- sharks
- rays and skates
What are some characteristics of sharks?
- jaws not attached to skull
- vision, chemo and electroreception
- use liver instead of swim bladder for buoyancy
What group is referred to as the bony fishes?
the osteichthyes
Briefly describe the characteristics of the osteichthyes
- more bone in endoskeleton
- use swim bladder
- strengthened fins
What are the two main groups of bony fishes in osteichthyes and some examples of each?
Actinopterygii (ray fins)
-sturgeons, paddlefishes, bowfins, garpikes, teleosts**, carps, gobies, salmon, trout, charr, perch
Sacropterygii (lobe fins)
-lungfishes, coelancanth
What is the significance of the Ripidistian?
- intermediate between fish and tetrapods
- limb-like pectoral fins-standing?
- wrist joint, mobile neck
