Rhynchonkos
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Rhynchonkos Temporal range: Early Permian Cisuralian |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Subclass: | †Lepospondyli |
| Order: | †"Microsauria" |
| Family: |
†Goniorhynchidae Carroll and Gaskill, 1978 |
| Genus: |
†Rhynchonkos Schulze and Foreman, 1981 |
| Type species | |
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†Rhynchonkos stovalli (Olson, 1970) (originally Goniorhynchus stovalli) |
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| Synonyms | |
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Rhynchonkos is an extinct genus of microsaur. It is the only known member of the family Rhynchonkidae. Originally known as Goniorhynchus, it was renamed in 1981 because the name had already been given to another genus; the family, likewise, was originally named Goniorhynchidae but renamed in 1988. The type and only known species is R. stovalli, found from the Early Permian Fairmont Shale in Cleveland County, Oklahoma.Rhynchonkos shares many similarities with Eocaecilia, an early caecilian from the Early Jurassic of Arizona. Similarities between Rhynchonkos and Eocaecilia have been taken as evidence that caecilians are descendants of microsaurs. However, such a relationship is no longer widely accepted.
Rhynchonkos has an elongated body with at least 37 presacral vertebrae. Most vertebrae have ribs. Unlike other microsaurs, the atlas of Rhynchonkos lacks ribs. Both Rhynchonkos and Euryodus have atlases that bear a strong resemblance to those of nectrideans. Like nectrideans, the arch of the atlas is attached to the centrum, although this is likely the result of convergence.
The skull is triangular in dorsal view. The limbs are very small. It has a pointed, overhanging snout that extends beyond the tooth row. There are five or six premaxillary teeth and sixteen maxillary teeth, all of which are narrow and peg-shaped. The palate also has teeth, with rows on the ectopterygoid, palatine, and vomer. The bones of the skull roof are similar to those of gymnarthrids. There are two rows of teeth adjacent to one another in the lower jaw, with a marginal row on the dentary and an inner row on the coronoid.
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