Vertebrata (Vertebrates)

Abstract

The Vertebrata, or vertebrates, are all animals which possess a skull enclosing the brain and sensory organs. Most vertebrates (except for hagfish) also possess a vertebral column (hence their name).

Keywords: vertebrates; anatomy; characters; phylogeny; fossils; backbone

Figure 1.

The skull in the three major living vertebrate groups. (a) Hagfish (Hyperotreti); (b) Lamfrey (Hyperoartia); (c) Jawed vertebrates (Gnathostomata). Neurocranium (braincase) stippled; elements of the vertebral column in black. After Janvier, 1996.

Figure 2.

Two fundamental characters of the vertebrates: the neural crest (a) and the placodes (b). (a) Sections through a shark embryo showing the development of the neural crest cells (a1) and their subsequent ventrolateral migration (a2). (b) Head of a shark embryo in lateral view, showing the distribution of the placodes (thickenings of the external germ layer, or ectoderm) which will ultimately result in various sense organs (olfactory organ, eye lens, ear and lateral‐line system). (c) Two successive stages in the development of the olfactory organ from a placode.

Figure 3.

The vertebral column in a lamprey (a) and a jawed vertebrate (dogfish, b). The dorsal elements (arcualia) of the lamprey are assumed to be homologous to those of the dogfish. After Janvier 1996.

Figure 4.

Interrelationships of the vertebrates and their distribution through time. Actual range in black, presumed ‘ghost range’ (hypothetical range inferred from relationship) hatched. Living groups in grey. Thelodonts are of undecided affinity. Abbreviations for geological ages: Tr, Tremadoc; Ar, Arenig; Ln, Llanvirn; Lo, Llandeilo; C, caradoc; As, Ashgill; Ll, Llandovery; W, Wenlock; Lu, Ludlow; Pr, Pridoli; L; Lower; M, Middle; U, Upper. Major nested groups and their defining characters appearing at each node of the tree 1, Craniata (or Vertebrata in broad sense); skull, neural crests, placodes; 2, Vertebrata (in restricted sense); vertebral column, eye muscles, heart innervation, lymphocytes; 3, calcified exoskeleton; 4, sensory‐line system enclosed in canals or grooves, extensive exoskeleton; 5, anal fin, paired fin‐folds?; 6, perichondral bone or calcified cartilage in endoskeleton; 7, cellular bone, true pectoral fins with musculature, upwardly tapering tail, bony ring covering the eyeballs; 8, Gnathostomata: jaws, pelvic fins; 9, dental lamina (skin fold in which teeth develop); 10, Teleostomes; otoliths, narrow‐based braincase with ventral fissure, separate anterior and posterior nostrils on each side of the snout; 11, Osteichthyans: endochondral bone in endoskeleton, lepidotrichs on fins, tooth‐bearing bones lining the jaws.

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Further Reading

Donoghue PCY, Forey PL and Aldridge RJ (2000) Condont affinity and chordate phylogeny. Biological Reviews 75: 191–251.

Janvier P (1993) Patterns of diversity in the skull of jawless fishes. In: Hanken J and Hall BK (eds) The Skull, vol. 2, pp. 131–188. Chicago, IL: The University of Chicago Press.

Janvier P (1996) Early Vertebrates. Oxford, UK: Oxford University Press.

Janvier P (1996) The dawn of the vertebrates: characters versus common ascent in the rise of current vertebrate phylogenies. Palaeontology 39: 259–287.

Janvier P in Maddison D and Maddison W (eds)

[http//phylogeny.arizona.edu/tree/eukaryotes/animals/chordata/vertebrata.html].

Long JA (1995) The Rise of Fishes. Baltimore, MD: John S Hopkins University Press.

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How to Cite close
Janvier, Philippe(May 2001) Vertebrata (Vertebrates). In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0001531]