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The extinct jawless fish of the Class 'Thelodonti' ("Nipple teeth") were very similar to the fish of the classes Heterostraci and Anaspida, though the thelodonts were covered with distinctive, small, spiny scales, which are their most common fossils. They lived in both freshwater and marine environments during the Silurian and Devonian periods.
The scales of the thelodonts, like the dermal denticles of sharks, were uniquely ornamented, with each scale having its own pulp. Thelodonts were also among the first vertebrates to have a digestive tract with a stomach, as some of the fossils of whole thelodonts show a box-like stomach. Other contemporary jawless fishes are not known to have stomachs, as those whole fossils that show the digestive tract (such those of Anaspids) show the esophagus connecting directly with the intestines.

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See also

References

External links

See also

★ Thelodontidae

References

★ Donoghue and Smith (2001) The anatomy of Turinia pagei (Powrie), and the phylogenetic status of the Thelodonti, Transactions of the Royal Society of Edinburgh: Earth Sciences, 92, p.15-37

★ Janvier, Philippe. ''Early Vertebrates'' Oxford, New York: Oxford University Press, 1998. ISBN 0-19-854047-7

★ Long, John A. ''The Rise of Fishes: 500 Million Years of Evolution'' Baltimore: The Johns Hopkins University Press, 1996. ISBN 0-8018-5438-5

External links

★ A NEW EARLY DEVONIAN THELODONT FROM CELTIBERIA (SPAIN)