most basal gnathostomes
fishes make up how much of phylum chordata
# species in chondrichthyes
when did elasmobranchii's appear
elasmobranchii # of species
sharks/rays body form
sharks=fusiform (tapers at both ends) rays=depressed
has spiral valve in intestine. name 2 functions
elasmobranchii, increases time food is in intestine and inc surface area for diffusion
elasmobranchii fertilization internal or external? organ?
diverged from earliest shark lineage
sister taxon to sharks
holocephali # of species
recessed groove w/ neuramasts make up which system? 2 uses?
lateral line system for mechanoreception (sensing environment). used to detect prey/predators and navigation
group w/o lateral line system
t/f all fish, some adult reptiles and some amphibian larvae have lateral line system
ampullae lorenzini are? function? found in?
specizlied sensory cells, function to detect electric currents in water. found in cartilaginous fish
electric potentials given off during? that function to?
neuromuscular activity, alert for prey
electrocytes 2 functions and which organisms has them
stun prey/protection from predators. electric rays have them
t/f all elasmobranchs are oviparous
false, ovi , viviparous, some release eggs into environment
some sharks/rays deposit eggs into
what do egg cases have to attach to objects
t/f elasmobranchs have diverse means of xferring nutrients to young including placenta, umbilical chord, milk and even live young/eggs!
elasmodbranch teeth are called? modified?
denticles, placoid scales
3 ways elasmobranch teeth resemble those of other vertebrates
pulp cavity, dentine, covered by enamel
elasmobranch teeth are tight/loosely attached? and constantly being
loosely, replaced (polyphodont)
skeleton and musculature of actinopterygii found within
#species in actinopterygii
chondrostei skeletal composition/tail shape
#species of chondrostei
gas bladder provides neutral buoyancy for which group?
teleosti scales term
clade teleostei tail shape
how does clade teleostei feed
expansion of buccal cavity in teleosts generates which type of pressure, function?
negative, draw in food
class w/ sturdy skeleton and musculature inside fins
# species in sarcopterygii
# of dipnoi species
coelocanths # species