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Introduction to the Vertebrata. And their relatives. 1. Animals with a hollow dorsal nerve cord, notochord, and pharyngeal gill slits.
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Introduction to the Vertebrata And their relatives
1. Animals with a hollow dorsal nerve cord, notochord, and pharyngeal gill slits. 2. Brain encapsulated, or at least partially so, by a cartilaginous or bony cranium. Vertebrae, associated with or replace notochord. First duplication of genome (1R). 3. Loss of vertebrae. 4. Mineralized bone. Second duplication of the genome (2R). 5. Head shield of dermal bone; bony scales. 6. Paired spines or fins. 7. Neurocranium encloses brain dorsally. 8. Mouth formed by articulated jaws. 9. Teeth erupt from dental lamina. 10. Paired fin radials barely extend beyond body. 11. Gills covered by an operculum. 12. Pectoral and pelvic girdles anchored to vertebral column. 13. Digits reduced to 5 or fewer; radius as long as the ulna. Operculum lost. 14. Premaxilla less than 2/3 skull width. 15. Egg with an outer amnion membrane. 16. One temporal fenestra formed by the squamosal and jugal bones. 17. Large post-temporal fenestra; suborbital foramen in palate. 18. Two temporal fenestrae; upper one formed by the squamosal and postorbital bones. 19. Trunk ribs single-headed, end of humerus robust.
Defining Vertebrates They posses the following characters at some point in their lives: • Pharyngial gill slits • Notochord • Hollow dorsal nerve cord • Vertebrae
Phylum Vertebrata • The minimal vertebrate • Hagfish, cyclostomes without vertebrae
Phylum Vertebrata • Petromyzontida
Phylum Vertebrata • Chondrichthyes
Phylum Vertebrata • Osteichthyes
Phylum Vertebrata • Osteichthyes
Phylum Vertebrata • Batrachomorpha
Phylum Vertebrata • Anapsida • Lepidosauromorpha • Archosauromorpha (in part)
Phylum Vertebrata • Aves (within Archosauromorpha)
Phylum Vertebrata • Mammalia
Vertebrates • OVER CLASSIFIED… • Why?
Vertebrates • OVER CLASSIFIED • Degree of difference between orders of birds DOES NOT APPROACH that observed between orders of insects!!!
Vertebrates group within Chordates • Hollow dorsal nerve cord • Notochord • Pharyngeal Gill Slits
Other Chordates: • Cephalochordates • Tunicates
Evo-Devo • Literally means evolution by means of changes in development • Discovery of HOX genes in the 1980s • These are genes that regulate the on-off switch for genes in development and determine timing • Arranged in linear arrays that correspond to anterior-posterior axis
Major Events in the Evolution of the Vertebrates • The evolution of jaws
Major Events in the Evolution of the Vertebrates • The evolution of a weight-bearing appendicular skeleton
Major Events in the Evolution of the Vertebrates • The evolution of the amniotic egg • This would be the point of transition between amphibians and reptiles