Gnathostomes Flashcards
Developmental changes from Cyclostomata to Gnathostomata leads to
2 nostrils and jaws
Shift in head development also allows for
Elongation of forebrain
- Forebrain involved in processing and integration of info
- Shape changes seen in head due to space, allowing the forebrain to grow
How do Gnathostome pharyngeal arches differ from Cyclostome pharynx?
Cyclostomes:
- Branchial baskets without articulations
- Gill tissue on medial side
Gnathostomes:
- Arches with articulation (joints)
- Gill tissue on lateral side
Vertebrate skull is a composite structure
- Structural components
- From 2 germ layers: neural crest (ectoderm) and mesoderm
- Multiple types of bone: endochondral bone (cartilage precursor, cartilage first later becomes bone?) and dermal bone (forms between layers of dermis (deep skin))
Components of the vertebrate skull
1) Chondrocranium (neurocranium)
2) Splanchnocranium (visceral/branchial arches)
3) Dermatocranium
Chondrocranium
- Starts as nasal, optic, and otic capsule pairs on shelf
- Neural crest and mesoderm
- Endochondral bone
Splanchnocranium
- Neural crest
- Endochondral bone
Dermatocranium
- Overlays the other two, not in cyclostomes and sharks
- Neural crest and mesoderm
- Dermal bone (no cartilage precursor)
Paired fins arise from changes to trunk development
- Cells bud off from lateral somitic frontier
- Muscle precursor cells migrate into limb bind (turn into fins or limbs)
- Cells migrate from: ventral paraxial mesoderm and somatic lateral plate
Other changes between Cyclostomata and Gnathostomata
- Fully developed cerebellum
- Presence of myelin
- 3 semicircular canals
- Mineralized tissues like bone, true teeth
- Vertebrae have a centrum connecting to ribs or hemal spine
There are lots of extinct basal fish groups, often with
elaborate armour made of dermal bone
