pterichthyodes

The winged fish, Pterichthyodes (1859)

Phylum : Chordata
Class : Placodermi
Genus : Pterichthyodes
Species : P. milleri

  • Middle Devonian (450 Ma)
  • 25 cm long (size)
  • England (map)

Pterichthyodes is a genus of antiarch placoderm fishes from the Devonian period. Its fossils have been discovered in Scotland. They were one of the first species recognized for what they were, as their fossils are common in the Old Red Sandstone formation studied by geologists in the early 19th century. Due to their extreme divergence from modern-day fish, they were a puzzle unsolved until Charles Darwin brought forward his theories on evolution.

Pterichthyodes had heavily armored heads and front bodies, while their tail ends were uncovered. Specimen length ranges from 20 cm to 30 cm. As placoderms, they were members of one of the first group of animals to possess jaws, though they had grinding plates rather than teeth. The Pterichthyodes are distinguished easily from other placoderms by their odd wing-like appendage where fins would be found on a modern fish (“pterichthys” is Ancient Greek for “wing-fish”)–strictly speaking, these are not fins as we normally think of them, which evolved in another group of fish, the Actinopterygii. Fossils of Pterichtyodes showing eyes positioned on the top of the head and a “ventrally flattened trunk shield” suggest that it was a “bottom dweller”, living at the bottom of lakes, where it might have crawled using its pectoral appendages. It has also been theorized that Pterichthyodes used these appendages to bury itself.

Pterichthyodes illustration by F. John