Temporal range: Late Carboniferous
Hylonomus BW.jpg
An artist's illustration of Hylonomus lyelli
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Sauropsida
Genus: Hylonomus
Dawson, 1860
Type species
Hylonomus lyelli
Dawson, 1860
Hylonomus (pronounced /haɪˈlɒnəməs/, hylo- "forest" + nomos "dweller") was a very early reptile. It lived 312 million years ago during the Late Carboniferous period. It is the earliest unquestionable reptile (Westlothiana is older, but may in fact be an amphibian, and Casineria is rather fragmentary). Hylonomus lyelli was 20 centimetres (8 in) long (including the tail) and probably would have looked rather similar to modern lizards. It had small sharp teeth and likely ate small invertebrates such as millipedes or early insects. Fossils of Hylonomus have been found in the remains of fossilized club moss stumps in Joggins, Nova Scotia, Canada. It is supposed that, after harsh weather, the club mosses would crash down, with the stumps eventually rotting and hollowing out. Small animals such as Hylonomus, seeking shelter, would enter and become trapped, starving to death. Fossils of the basal pelycosaur Archaeothyris and the basal diapsid Petrolacosaurus are also found in the same region of Nova Scotia, although from a higher stratum, dated approximately 6 million years later. Fossilized footprints found in New Brunswick have been attributed to Hylonomus, at an estimated age of 315 million years. his animal was discovered by John William Dawson in the mid-19th century. The species name comes from Dawson's teacher, the geologist Sir Charles Lyell. While it has traditionally been included in the group Protothyrididae, later studies have shown that it is probably more closely related to diapsids. It was discovered in 1851.