The Craniates

1
The Craniates

• Craniata
• Subphylum Hyperotreti-
• hagfish
• Subphylum Vertebrata-
• ostracoderms
• lamprey
• Gnasthostome fishes

2
Craniata

• Skull made of cartilage or fibrous tissue
• Surrounds brain
• Olfactory organs
• Eyes
• Inner ear

3
Subphylum Hyperoptreti

• Hagfish
• Most primitive of all craniates
• Brain
• Bone
• Both brain and bone key elements in evolution

4
Subphylum Vertebrata

• The hyperoartia-
• lamprey
• Gnathostomata
• Cartilaginous fishes
• Bony fishes

5
Survey of Fishes

• Subphylum Hyperotreti- Hagfish
• Subphylum Vertebrata-
• Ostracoderms
• Lampreys
• Gnathostome Fishes

6
Subphylum Hyperotreti

• Class Myxini
• Hagfish-
• Heads supported by cartilaginous bars
• Brains enclosed in fibrous sheath
• Lack vertebrae
• Retain notochord as axial support

7

• Four pairs of sensory tentacles surrounding
  mouths
• Ventrolateral slime glands

8

• Coldwater marine habitats
• Buried in sand and mud
• Feed on soft bodied invertebrates
• And scavenge on dying fish

9
Subphylum Vertebrata

• Vertebrae that serve as a primary axial support
• Include Jawless ostacoderms and Hyperoartia
  (Lamprey)
• Most part of a Superclass Gnathostomata
• Include jawed fish and tetrapods

10
Ostracoderms

• Extinct agnathans
• Bony armor
• Bottom dwellers
• Extracting annelids and other inverts from
  sediment
• Bony plates around mouth- jaw like structure

11
Hyperoartia

• Class Cephalaspidomorphi
• Lamprey (agnathas)
• Marine and freshwater
• Prey on other fish
• Larvae filter feeders
• Mouth is suckerlike
• Epidermal teeth, rasping tongue
• Glands secrete anticoagulant and feed on blood
• External fertilization

12
Gnathostomata

• Jaws evolved from anterior gill support arches
  that had acquired a new role, being modified to
  pump water over the gills by opening and closing
  the mouth more effectively.
• The mouth could then grow bigger and wider,
  making it possible to capture small prey.
• This close and open mechanism would with time
  become stronger and tougher, being transformed
  into real jaws.
• Modified dermal bones on the surface of the skin
  would migrate into the mouth and become primtive
  teeth.

13
Paired appendages

• Increased activity
• Increased stability
• Lateral steering
• Pectoral fins- usually just behind the head
• Pelvic fins- ventral and more posteriorly
• Modern bony fishes pelvic fins usually behind the
  pectoral fins

14

• Ability to feed efficiently
• Produced more offspring and exploit new habitat
• Fostered adaptive radiation
• Cartilaginous fishes
• Class Chondrichthyes
• Bony fish
• Class Osteichthyes

15
Class Chondrichthyes

• Sharks
• Skates
• Rays
• Ratfishes

16

• Most carnivores or scavengers
• Marine
• Biting mouthparts
• Paired appendages
• Placoid scales
• Cartilagious endoskeleton

17
Class Osteichthyes

• Bone in their skeleton
• and/or scales,
• bony operculum covering gill openings and
• lungs or swim bladder.