extant jawless fish

Cyclostomes

• [hagfish, lampreys], conodonts

• round math, lacks jaws

• notochord persists through life

- lamprey (dorsal) and hagfish (ventral) have arculia on notochord

cylostomes body

• no paired appendages

• muscular “tongue” and keratinized teeth

• no mineralized tissue

• single median nostril

• tubular heart w/ 3 chambers

hagfish

• entirely marine an live in deep ocean

• one nostril in front help vent gills and smell water

• number of gills varies

• sensory tentacles surround head

• lack developed eyes

• mucus on body

lampreys

• well developed eyes

• marine and freshwater

• teeth below oral hood

• attach and suck blood - endoparasitic

• 7 pairs gill slits

• simple gut tube; no stomach, absorbative intestines w/ spiral valve

conodonts

• mineralized teeth found in pharynx not homo to verts teeth

• large eyes

• notochord

• no jaws or paired fins

• v shaped myomeres

osteognathostomes

• ondontodes, ostracoderms , osteostacans, gnathostomes

• dermal bones present

• synapomorphies: dermal bones, odontodes, paired nasal sacs

• derived ones gain jaws and endochondral bone

ostracoderms

(paraphyletic)

• jawless, extinct

• one dorsal find with long body

• lacked paired fins

• hypo cercal tail (bottom lobe of tail longer than top)

  paired nostrils, true stomachs, mineralized cartilage

osteostracans

• sister taxa gnathostomes, group w/i ostracoderms, most derived

• pectoral fins

• heterocercal tail (upper lob longer than bottom)

• two dorsal fins

Gnathostomes

• have jaws, evolution indicates more active animals

• synapomorphies: jaws w/ teeth, horizontal septum w/ lateral line, two sets of paired fins

• not synapomorphies: 3rd semicirrcular canal in inner ear

  • 4 heart chambers: conus artenourus ( reduces blood pressure b4 pumping)

  • 2 nostrils, 2 nasal sacs

  • 2 dorsal fins

• 3 semicirrcular canals in inner ear

Development jaws

• mandibular arch : forms jaw, bears teeth

• hyoid: suspends jaw

• pharyngeal slit: pouches from gills slits

• branchial: skeletal bars- open gills

placoderms

• armored fish

• district joint between head and torso to move head

• true jaw w/ tooth plate

• heterocercal tail

Devonian extinction

• ostracoderms, placoderms, early gnathostomes

• shallow water or competition w/ chondrites, Osteichthyes