Agnathans (Jawless fish) Flashcards
when does agnathans mean
jawless fish
what does Agathan’s include (the clads)?
- cyclostomes (hagfish & lampreys)
- conodonts
- ostracoderms
Defining hagfish features
- teeth made by keratin
- lacking a lateral line
- poorly developed eyes
they are scavengers
Defining Lamprey features (how they differ from ancestor cephalochordate)
- parasitic
- well developed eyes
- tidal ventilation ( gil slits)
- kertainous teeth
differences between hagfish and lamprey?
- hagfish are scavengers so they have their Gil slits further back so they can still breathe while they eat, lampreys have the gil slits closer to the front
- the vertebral elements are ventral in the hagfish but dorsal in the lampreys
how many chambers does a cyclostome heart have and what are they?
2 chambers (atrium and ventricle), 1 assessory chamber called the sinus venosus
what are euphaneropids
they are a close relative to lampreys but have evidence of having endoskeletal elements and an anal tail
What are Conodonts
they are animals that have left mineralized microfossils (mostly feeding stucurtures
what are Ostracoderms? (features)
- shell skinned jawless fish
boney head held and smaller bony scales - suction feeders
- true gills
- caudal and pectoral gils
- internal cartilaginous skeleton
what are arandaspida and astrasida?
type of ostracoderm
- half of body armoured
- Doral armour was smooth
- gils were in middle of body
what is herteostaci
type of ostracoderm
- armour has spikes
what are anaspida
type of ostracoderm
- lacked shell but had some spikes
what are thelodonti
types of ostracoderm
- notable stomach
- durable scales
what are galeaspida
type of ostracoderm
- first appearance of paired appendages
- pituriaspida closely resemble
what are osterostaci?
type of osteracoderm
- calcified skeleton
- paired pectoral fin
- evidence of electric organs
what evolutionary changes do you see in the group of Agathan’s, specifically ostracoderms?
They started to
- develop calcified armour that is used for bodily support and protection
- the development of paired fins helps with movement
- they are breathing more efficiently in water meaning that they are using more energy
- stomach developing means they are eating to get more energy
what 2 groups use odontodes?
conodonts as their teeth and ostracoderms armour
what are odontodes?
they are the first evidence of tooth like structures made from hydroxyapatite (calcium and phosphate)
