''Hylonomus'' (; ''hylo-'' "forest" + ''nomos'' "dweller") is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

of reptile that lived 312

million years ago The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago). ...

during the Late Carboniferous period. It is the earliest unquestionable reptile (''

Westlothiana ''Westlothiana'' ("animal from West Lothian") is a genus of reptile-like tetrapod that lived about 338 million years ago during the latest part of the Visean age of the Carboniferous. Members of the genus bore a superficial resemblance to mod ...

'' is older, but in fact it may have been an amphibian, and ''

Casineria ''Casineria'' is an extinct genus of tetrapod which lived about 340-334 million years ago in the Mississippian epoch of the Carboniferous period. Its generic name, ''Casineria'', is a latinization of Cheese Bay, the site near Edinburgh, Scotla ...

'' is rather fragmentary). The only species is the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen( ...

''Hylonomus lyelli''. Despite being amongst the oldest known reptiles, it is not the most primitive member of group, being a eureptile more derived than either

parareptiles Parareptilia ("at the side of reptiles") is a subclass or clade of basal sauropsids (reptiles), typically considered the sister taxon to Eureptilia (the group that likely contains all living reptiles and birds). Parareptiles first arose near t ...

or captorhinids.

Description

''Hylonomus'' was long (including the tail). Most of them are 20 cm long and probably would have looked rather similar to modern

lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia al ...

s. It had small sharp teeth and it likely ate small invertebrates such as

millipede Millipedes are a group of arthropods that are characterised by having two pairs of jointed legs on most body segments; they are known scientifically as the class Diplopoda, the name derived from this feature. Each double-legged segment is a re ...

s or early

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs ...

s. Fossils of ''Hylonomus'' have been found in the remains of fossilized club moss stumps in the

Joggins Formation The Joggins Formation is a Formation (geology), geologic formation in Nova Scotia. It preserves fossils dating back to the Carboniferous Period (geology), period, including ''Hylonomus'', the earliest known reptile. In addition to fossils, the Jog ...

Joggins, Nova Scotia Joggins is a rural community located in western Cumberland County, Nova Scotia, Canada. On July 7, 2008 a 15-km length of the coast constituting the Joggins Fossil Cliffs was officially inscribed on the World Heritage List.p39 Other organisms ...

, 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. An alternative hypothesis is that the animals made their nests in the hollow tree stumps. Fossils of the basal pelycosaur ''

Archaeothyris ''Archaeothyris'' is an extinct genus of ophiacodontid synapsid that lived during the Late Carboniferous and is known from Nova Scotia. Dated to 306 million years ago, ''Archaeothyris'', along with a more poorly known synapsid called '' Echinerpe ...

'' and the basal

diapsid Diapsids ("two arches") are a clade of sauropsids, distinguished from more primitive eureptiles by the presence of two holes, known as temporal fenestrae, in each side of their skulls. The group first appeared about three hundred million years ...

Petrolacosaurus ''Petrolacosaurus'' ("rock lake lizard") is an extinct genus of diapsid reptile from the late Carboniferous period. It was a small, long reptile, and the earliest known reptile with two temporal fenestrae (holes at the rear part of the skull) ...

'' 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 New Brunswick (french: Nouveau-Brunswick, , locally ) is one of the thirteen Provinces and territories of Canada, provinces and territories of Canada. It is one of the three Maritime Canada, Maritime provinces and one of the four Atlantic Canad ...

have been attributed to ''Hylonomus'', at an estimated age of 315 million years. Hylonomus Scale

This animal was discovered by

John William Dawson Sir John William Dawson (1820–1899) was a Canadian geologist and university administrator. Life and work John William Dawson was born on 13 October 1820 in Pictou, Nova Scotia, where he attended and graduated from Pictou Academy. Of Scot ...

in the mid-19th century. The species' name was given it by Dawson's teacher, the geologist Sir Charles Lyell. While it has traditionally been included in the group Protorothyrididae, it has since been recovered outside this group. ''Hylonomus lyelli'' was named the Provincial Fossil of Nova Scotia in 2002.

References

External links

Fossils of Nova Scotia - The Tree Stump Animals

Early Researchers & Finds of the Joggins Fossil CliffsHylonomus: Provincial Fossil of Nova ScotiaA photograph of the disarticulated skeleton, credited to J. CalderAnother photo of the specimen, from Dr. Melissa Grey's twitter account
{{Taxonbar, from=Q132458 Prehistoric romeriids Carboniferous reptiles of North America Transitional fossils Prehistoric reptile genera Paleozoic life of Nova Scotia Pennsylvanian genus first appearances Pennsylvanian genus extinctions