''Archaeothyris'' is an extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of ophiacodontid

synapsid Synapsida is a diverse group of tetrapod vertebrates that includes all mammals and their extinct relatives. It is one of the two major clades of the group Amniota, the other being the more diverse group Sauropsida (which includes all extant rept ...

that lived during the

Late Carboniferous Late or LATE may refer to: Everyday usage * Tardy, or late, not being on time * Late (or the late) may refer to a person who is dead Music * Late (The 77s album), ''Late'' (The 77s album), 2000 * Late (Alvin Batiste album), 1993 * Late!, a pseudo ...

and is known from

Nova Scotia Nova Scotia is a Provinces and territories of Canada, province of Canada, located on its east coast. It is one of the three Maritime Canada, Maritime provinces and Population of Canada by province and territory, most populous province in Atlan ...

. Dated to 306 million years ago, ''Archaeothyris'', along with a more poorly known synapsid called '' Echinerpeton'', are the oldest undisputed synapsids known. The name means ''ancient window'' (Greek), and refers to the opening in the skull, the

temporal fenestra Temporal fenestrae are openings in the temporal region of the skull of some amniotes, behind the orbit (eye socket). These openings have historically been used to track the evolution and affinities of reptiles. Temporal fenestrae are commonly (al ...

, which indicates this is an early synapsid. '' Protoclepsydrops'' also from Nova Scotia is slightly older but is known by very fragmentary materials. Archaeothyris florensis

Description

''Archaeothyris'' was more advanced than the early sauropsids, having strong jaws that could open wider than those of the early

reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocepha ...

s. 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. ''Archaeothyriss 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 synapsids from the Carboniferous and Permian. '' Archaeothyris'', and '' Clepsydrops'' were among the earliest ophiacodontids, appearing in the Late Carboniferous. Ophiacodontids are among the most b ...

, a group of early pelycosaurs that evolved early in the

. It was one of the earliest and most basal synapsids (the group which includes

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

s). Below is a

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

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 during the Bashkirian stage of the Late Carboniferous. It is the earliest known crown group amniote and the oldest known unquestionable reptile, ...

'' 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 one of the earliest known reptiles with two temporal fenestrae (holes at the rear part of the ...

'' (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

coal forest Coal forests were the vast swathes of freshwater swamp and riparian forests that covered much of the lands on Earth's tropical regions during the late Carboniferous ( Pennsylvanian) and Permian periods.Cleal, C. J. & Thomas, B. A. (2005). "Pala ...

. The "trees" (actually giant club mosses) were very tall, some, such as ''

Lepidodendron ''Lepidodendron'' is an extinct genus of primitive lycopodian vascular plants belonging the order Lepidodendrales. It is well preserved and common in the fossil record. Like other Lepidodendrales, species of ''Lepidodendron'' grew as large-tree ...

'', 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 "Labyrinthodontia" (Greek, 'maze-toothed') is an informal grouping of extinct predatory amphibians which were major components of ecosystems in the late Paleozoic and early Mesozoic eras (about 390 to 150 million years ago). Traditionally conside ...

amphibian Amphibians are ectothermic, anamniote, anamniotic, tetrapod, four-limbed vertebrate animals that constitute the class (biology), class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all Tetrapod, tetrapods, but excl ...

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 Ophiacodontidae 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