Craniates & Vertebrates

Craniates

Overview of Craniates

• Chordates with a head
• Cranium = "Skull"
• Allows for greater movement coordination and complex feeding behavior
• Habitats
• Marine
• Freshwater
• Terrestrial
• Includes the largest animals that ever existed Examples: Sauropods, blue whales
• Most are vertebrates
• Craniate Derived Character State
• 2+ clusters of Hox genes
• Neural crest
• Temporary embryonic cells
• Endoskeleton and cephalization
• Modified circulatory system
• Pharyngeal clefts

Jawless Craniates

• Two classes lack jaws
• Lack teeth and paired limbs
• Mouth like an open tube
• Long, flexible tubular bodies

Class Myxini

• Only living vertebrate that lack vertebrae
• But does have developed notochord
• Cartilaginous cranium
• Tiny eyes, lack lenses
• Mouth surrounded by tentacles
• Feeds on soft bodied worms / corpses
• Corpses
• Grip on flesh using Keratinous plates in the mouth
• Ties body into knot
• Slides knot forward until it braces against flesh
• Pulls off chunk
• Protective slime for defense
• Myxo = "slime"

Subphylum Vertebrata

Vertebrate Characteristics

• Vertebral Column: backbone
• Chain of skeletal elements surrounding and protecting fragile nerve chord
• Complex nervous system
• Replaces the notochord
• Increased rigidity
• Allows for attachment of skeletal muscles / other bones

Class Petromyzontida

• Lampreys
• Eyes lack lens
• No jaw or paired limbs
• Skeleton made of cartilage
• Notochord surrounded by cartilaginous tube
• Paired dorsal spines protect nerve chord
• Primitive vertebral column
• Parasites of fish
• Adults in lakes or ocean
• Clamp onto fish and rasp flesh
• Holds onto rocks when not feeding