''Archaeothyris'' 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 ophiacodontid

synapsid Synapsids + (, 'arch') > () "having a fused arch"; synonymous with ''theropsids'' (Greek, "beast-face") are one of the two major groups of animals that evolved from basal amniotes, the other being the sauropsids, the group that includes reptil ...

that lived during the

Late Carboniferous Late may refer to: * LATE, an acronym which could stand for: ** Limbic-predominant age-related TDP-43 encephalopathy, a proposed form of dementia ** Local-authority trading enterprise, a New Zealand business law ** Local average treatment effect, ...

and is known from

Nova Scotia Nova Scotia ( ; ; ) 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. Nova Scotia is Latin for "New Scotland". Most of the population are native Eng ...

. Dated to 306 million years ago, ''Archaeothyris'', along with a more poorly known synapsid called ''

Echinerpeton ''Echinerpeton'' is an extinct genus of synapsid, including the single species ''Echinerpeton intermedium'' from the Late Carboniferous of Nova Scotia, Canada. The name means 'spiny lizard' (Greek). Along with its contemporary ''Archaeothyris'', ...

'', are the oldest undisputed synapsids known. The name means ''ancient window'' (Greek), and refers to the opening in the skull, the

temporal fenestra An infratemporal fenestra, also called the lateral temporal fenestra or simply temporal fenestra, is an opening in the skull behind the orbit in some animals. It is ventrally bordered by a zygomatic arch. An opening in front of the eye sockets ...

, which indicates this is an early synapsid. ''

Protoclepsydrops ''Protoclepsydrops'' is an extinct genus of early synapsids, found in Joggins, Nova Scotia. The name means 'first ''Clepsydrops, and refers to it being the predecessor of the other early synapsid ''Clepsydrops''. Description Like ''Archaeothyris ...

'' also from Nova Scotia is slightly older but is known by very fragmentary materials. Archaeothyris NT small

Description

''Archaeothyris'' was more advanced than the early

sauropsids Sauropsida ("lizard faces") is a clade of amniotes, broadly equivalent to the class Reptilia. Sauropsida is the sister taxon to Synapsida, the other clade of amniotes which includes mammals as its only modern representatives. Although early sy ...

, having strong jaws that could open wider than those of the early reptiles. While its sharp teeth were all of the same size & shape, it did possess a pair of enlarged canines, suggesting that it was a carnivore. Archaeothyris' legs were articulated laterally at its pelvis and shoulders, which gave it a sprawling stance. The first toe is smaller than the second.

Classification

''Archaeothyris'' belonged to the family

Ophiacodontidae Ophiacodontidae is an extinct family of early eupelycosaurs from the Carboniferous and Permian. '' Archaeothyris'', and ''Clepsydrops'' were among the earliest ophiacodontids, appearing in the Late Carboniferous. Ophiacodontids are among the mos ...

, a group of early pelycosaurs that evolved early in the

. It was one of the earliest and most basal synapsids (the group which includes mammals). Below is a

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...

modified from the analysis of Benson (2012):

Discovery and paleoecology

Fossils of ''Archaeothyris'' were first described in 1972 from the Joggins fossil cliffs, the same locality in which the early reptiles ''

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 ...

'' and ''

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 ...

'' (both of which resemble ''Archaeothyris'') were found. ''Archaeothyris'' lived in what is now

, about 306 million years ago in the Carboniferous Period ( Pennsylvanian).Hess J.C., Lippolt H.J. (1986): 40Ar/39Ar ages of tonstein and tuff sanidines: new calibration points for the improvement of the Upper Carboniferous time scale. ''Chem Geol'' no 59: pp 143–154 Nova Scotia at this time was a swamp, similar to today's

Everglades The Everglades is a natural region of tropical wetlands in the southern portion of the U.S. state of Florida, comprising the southern half of a large drainage basin within the Neotropical realm. The system begins near Orlando with the Kissim ...

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...

. The "trees" (actually giant

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 ...

es) were very tall, some, such as ''

Lepidodendron ''Lepidodendron'' is an extinct genus of primitive vascular plants belonging to the family Lepidodendraceae, part of a group of Lycopodiopsida known as scale trees or arborescent lycophytes, related to quillworts and lycopsids (club mosses). Th ...

'', up to tall. ''Archaeothyris'' and the other early amniotes lived in the moist vegetation on the forest ground, together with the more terrestrially adapted labyrinthodont amphibians.

References

External links

Transitional Vertebrate Fossils
- includes description of important transitional genera from reptile to mammal (includes a little information about ''Archaeothyris'') {{Taxonbar, from=Q133034 Ophiacodontids Prehistoric synapsid genera Carboniferous synapsids Carboniferous synapsids of North America Transitional fossils Taxa named by Robert R. Reisz Fossil taxa described in 1972 Paleozoic life of Nova Scotia

Description

Classification

Discovery and paleoecology

See also

References

Further reading

External links