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What is in the superclass agnatha?
lamprey and hagfish are living representatives
What are the tree characteristics of the phylum chordata?
- Hollow, dorsal nerve chord
- Pharyngeal slits
What types of fishes are in Gnathostoma?
Order Myxiniformes - modern hagfish
Order Petromyzontiformes - modern lamprey
‘Ostracoderm’ includes two important Classes:
Class Cephalaspidomorphi = ancestor to lamprey??
Class Pteraspidomorphi = ancestor to hagfish??
• Ostracoderms now extinct
What classes are found in the superclass Gnathostomata?
Class Placodermi - plate-skinned (extinct)
- Class Acanthodii - spiny sharks (extinct)
- Class Sarcopterygii – lobed-fin fishes
Class Chondrichthys - sharks, skates, rays
Class Actinopterygii - ray-finned fishes
What did this animal have on its head and shoulder?
Dunkleosteus- Head and shoulder girdles with dermal bony plates joined by Craniovertebral joint which allowed it to move.
Arthrodire- "jointed neck"
What is this and what is it most closely related to?
Acanthoidian- extict class of fish
More closely related to modern day bony fish than sharks, even though skeleton was mostly made of cartilage.
What are some of the features of the
- Terminal mouth
- Fins broad-based and stiff,long radial elements
- No anal find.
- Caudal fin is homocercal
- Body supported by notochord only
- Often spines in front ofdorsal, pectoral, and pelvic
Describe some Hybodont Features
- -Terminal mouth
- - Fins flexible and mobile
- -Anal fin
- -Caudal fin heterocercal
- -Body supported by notochord
- with neural arches
- - Spines on dorsal fin
What are the four things that the third elasmobranch radiation that allowed improved feeding and locomotion?
- 1. Jaws: ventral mouth with protrusible upper jaw
- 2. Dentition: tooth replacement system
- 3. Fins: ceratotrichia supporting the fins
- 4. Vertebrae: calcified vertebrae instead of notochord
What are the two subdivisions of Infraclass Euselachii?
Subdivision Selachii (sharks - 9 Orders)
Subdivision Batoidea (rays - 4 Orders)