3. p. 43Jawless Vertebrates and the Origin of Gnathostomes
- F. Harvey Pough, F. Harvey PoughProfessor Emeritus, Rochester Institute of Technology
- William E. Bemis, William E. BemisProfessor of Ecology and Evolutionary Biology and Faculty Curator of Ichthyology, Cornell University
- Betty McguireBetty McguireSenior Lecturer, Cornell University
- , and Christine M. JanisChristine M. JanisProfessor Emerita of Biology, Brown University, USA, Honorary Professor of Earth Sciences, University of Bristol, UK
Abstract
This chapter discusses early vertebrates. These were more complex and more active animals than the nonvertebrate chordates. Novel vertebrate anatomical features included a tripartite brain enclosed by a cranium, and a muscular pharynx for using the gills for respiration rather than for filter feeding. The chapter mentions gnathostomes, jawed vertebrates which represent an increase in complexity in the vertebrate body plan and reflects the vertebrate mode of life as an active predator. Soft-bodied vertebrates were known to derive from the early Cambrian and the earliest known vertebrates with bone or ostracoderms from the Late Ordovician. The chapter looks at the earliest evidence of bone in vertebrates. This is covered in the odontodes of the dermal head shield of ostracoderms and their bony tissues included bone, dentine, and enamaloid.
