Named By: John William Dawson - 1860.
Classification: Chordata, Reptilia, Captorhinida, Protorothyrididae.
Species: H. lyelli.
Size: 20 centimetres long.
Known locations: Canada, Nova Scotia.
Time period: Bashkirian of the Carboniferous.
Fossil representation: Several specimens, fossilised footprints found in New Brunswick.
has significance in the fossil record for being the first true
reptile. One particularly well presevered specimen was found in the
remains of a hollowed tree stump. It is thought that the Hylonomus
individual may have entered for either shelter or to feed on the
insects inside. It would seem however that the Hylonomus
trapped inside, the tree becoming its tomb. It’s probable that
because it was inside of the tree at the time, this particular
specimen was protected from the extremes of the fossilisation process
and underwent a more gentle fossilisation resulting in the animal being
The general morphology of Hylonomus is similar to modern day lizards. The teeth are adapted to be better suited to catching insects, with the front teeth being slightly longer than those at the back.