What is "hylonomus"

Hylonomus (; hylo- "forest" + nomos "dweller") is an extinct genus of reptile that lived 312 million years ago during the Late Carboniferous period. It is the earliest unquestionable reptile ( Westlothiana is older, but in fact it may have been an amphibian, and Casineria is rather fragmentary). The only species is the type species Hylonomous lyelli.