Hynerpeton bassetti

Hynerpeton is an extinct genus of early four-limbed vertebrate that lived in the rivers and ponds of Pennsylvania during the Late Devonian period, around 365 to 363 million years ago. The only known species of Hynerpeton is H. bassetti, named after the describer's grandfather, city planner Edward Bassett. Hynerpeton is known for being the first Devonian four-limbed vertebrate discovered in the United States, as well as possibly being one of the first to have lost internal gills.

The fact the remains of Hynerpeton were recovered from the US state of Pennsylvania makes Hynerpeton the first amphibian tetrapod known from the USA, and North America if you don't count the other species recovered from Greenland. The discovery of Hynerpeton in the US has altered the perception of how Tetrapods colonised the land, but the exact ramifications will not be easy to establish without significant further material, either of Hynerpeton, or other early amphibians. What can be established from the sparse fossil material is thatHynerpeton was one of the more primitive amphibians to have a terrestrial as well as aquatic lifestyle.