''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 nom ...

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 modern ...

'' 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 specime ...

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

eureptile Eureptilia ("true reptiles") is one of the two major subgroups of the clade Sauropsida, the other one being Parareptilia. Eureptilia includes Diapsida (the clade containing all modern reptiles and birds), as well as a number of primitive Permo-C ...

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 lizards. 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 resu ...

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 ...

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

club moss Lycopodiopsida is a class of vascular plants known as lycopods, lycophytes or other terms including the component lyco-. Members of the class are also called clubmosses, firmosses, spikemosses and quillworts. They have dichotomously branching s ...

stumps in the

Joggins Formation The Joggins Formation is a geologic formation in Nova Scotia. It preserves fossils dating back to the Carboniferous period, including ''Hylonomus'', the earliest known reptile. In addition to fossils, the Joggins Formation was a valuable source of ...

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. Fossils of the basal

pelycosaur Pelycosaur ( ) is an older term for basal or primitive Late Paleozoic synapsids, excluding the therapsids and their descendants. Previously, the term ''mammal-like reptile'' had been used, and pelycosaur was considered an order, but this is ...

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 a ...

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. It is one of the three Maritime provinces and one of the four Atlantic provinces. It is the only province with both English and ...

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 Scotti ...

in the mid-19th century. The species' name was given it by Dawson's teacher, the geologist

Sir Charles Lyell Sir Charles Lyell, 1st Baronet, (14 November 1797 – 22 February 1875) was a Scottish geologist who demonstrated the power of known natural causes in explaining the earth's history. He is best known as the author of ''Principles of Geolo ...

. While it has traditionally been included in the group

Protorothyrididae Protorothyrididae is an extinct family of small, lizard-like reptiles belonging to Eureptilia. Their skulls did not have fenestrae, like the more derived diapsids. Protorothyridids lived from the Late Carboniferous to Early Permian periods, ...

, 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