palæospondylns

from The Century Dictionary.

• noun A genus of primitive fish-like vertebrates considered to be related to the lampreys, but having the cartilages calcified and the vertebral centra represented by rings in the sheath of the notochord. There is no evidence of true jaws. The largest examples were a little under two inches in length. Their remains occur in the Lower Old Red Sandstone (Devonian) of Scotland. The only known species is P. gunnii.