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Edaphosauridae
| Edaphosauridae Fossil range: Late Pennsylvanian - Early Permian | |
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 Edaphosaurus | |
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The Edaphosaurids are a family of mostly large (up to 3 meters or more) derived, Late Pennsylvanian to Early Permian pelycosaurs. They were the earliest known herbivorous amniotes, and along with the Diadectidae the earliest known herbivorous tetrapods. The head is small in relation to the bulky body, and there is a tall sail along the back, which may have functioned as a thermoregulatory device. Advanced edaphosaurids were ecologically quite different from their contemporaries, the sphenacodontids. Unlike most basal synapsids, some edaphosaurids were herbivores, as is shown by the structure of the skull and teeth. Like many of their carnivorous sphenacodontid cousins, edaphosaurs were often equipped with a large “sail” along the back, formed by a great elongation of the neural spines of the vertebrae. This striking features, exhibited by several early synapsid lineages, is often said to have functioned as a temperature control device and perhaps also for sexual display. Their fossils have been recovered from North America and Europe only so far.
The derived genus Edaphosaurus was unique in that its "sail" possessed short bony cross bars. Edaphosaurus, Ianthasaurus, and probably Glaucosaurus, can be placed with confidence in this family, but a number of lesser-known forms, like Lupeosaurus and Nitosaurus, may belong here as well. Ianthasaurus, Lupeosaurus, and Edaphosaurus are characterized by the presence of greatly elongated neural spines that are rounded in cross-section. Glaucosaurus is known only from a partial skull. Although it seems probable that Glaucosaurus had spines like those of Edaphosaurus, no remains have been found that support this position. The neural spines of Edaphosaurus and Ianthasaurus (but not Lupeosaurus) also bear well-developed lateral tubercles or crossbars. On the lower (proximal) part of the spine looks like the mast of a square-rigged sailing ship. Distally, the tubercles on the two sides become less regular and go out of register, so that the right and left tubercles emerge at different vertical levels. The tubercles also become shorter with increasing distance up the "mast". The arrangement of these tubercles along the height of the spines is similar in the two taxa, as is the loss of contact between the postorbital and supratemporal bones of the skull.
References 
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- Carroll, R. L. (1988), Vertebrate Paleontology and Evolution, WH Freeman & Co.
- Reisz, R. R., 1986, Handbuch der Paläoherpetologie – Encyclopedia of Paleoherpetology, Part 17A Pelycosauria Verlag Dr. Friedrich Pfeil, ISBN 3-89937-032-5
External linksEdit
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