Archaeothyris
{{Short description|Extinct genus of synapsids}}
{{Automatic taxobox
| fossil_range = Late Carboniferous, {{fossil_range|306}}
| image = Archaeothyris_BW.jpg
| image_caption = Life restoration of Archaeothyris
| taxon = Archaeothyris
| type_species = {{extinct}}Archaeothyris florensis
| type_species_authority = Reisz, 1972Reisz, R., 1972. [https://www.researchgate.net/publication/38430531_Pelycosaurian_reptiles_from_the_Middle_Pennsylvanian_of_North_America Pelycosaurian reptiles from the middle Pennsylvanian of North America. Harvard University].
}}
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 Echinerpeton, are the oldest undisputed synapsids known.Falcon-Lang, H.J., Benton, M.J. & Stimson, M. (2007): Ecology of early reptiles inferred from Lower Pennsylvanian trackways. Journal of the Geological Society, London, 164; no. 6; pp 1113-1118. [http://findarticles.com/p/articles/mi_qa3721/is_200711/ai_n21137484/?tag=content;col1 article] The name means ancient window (Greek), and refers to the opening in the skull, the temporal fenestra, which indicates this is an early synapsid. Protoclepsydrops also from Nova Scotia is slightly older but is known by very fragmentary materials.{{cite web|title=Archaeothyris florensis|url=http://www.palaeocritti.com/by-group/eupelycosauria/archaeothyris|website=Palaeocritti|access-date=13 December 2014}}
Description
Archaeothyris was more advanced than the early sauropsids, 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.{{cite book |editor=Palmer, D.|year=1999 |title= The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals|publisher= Marshall Editions|location=London|page= 186|isbn= 978-1-84028-152-1}}
Archaeothyris's legs were articulated laterally at its pelvis and shoulders, which gave it a sprawling stance.{{citation needed|date=October 2020}} The first toe is smaller than the second.{{citation needed|date=October 2020}}
Classification
Archaeothyris belonged to the family Ophiacodontidae, a group of early pelycosaurs that evolved early in the Late Carboniferous. It was one of the earliest and most basal synapsids (the group which includes mammals).
Below is a cladogram modified from the analysis of Benson (2012):{{cite journal |last=Benson |first=R.J. |year=2012 |title=Interrelationships of basal synapsids: cranial and postcranial morphological partitions suggest different topologies |journal=Journal of Systematic Palaeontology |volume=10 |doi=10.1080/14772019.2011.631042 |issue=4 |pages=601–624|s2cid=84706899 }}
{{clade| style=font-size:85%;line-height:100%
|1={{clade
|label3=Amniota
|3={{clade
|1={{clade
|1=Captorhinus spp.
|label2=Synapsida
|2={{clade
|1={{clade
|1=Caseasauria
|2={{clade
|2={{clade
|2=Sphenacodontia}} }} }}
|2={{clade
|1=Varanopidae
|label2=Ophiacodontidae
|2={{clade
|1=Archaeothyris florensis
|2={{clade
|2={{clade
|1=Ophiacodon spp.
|2=Stereophallodon ciscoensis }} }} }} }} }} }} }} }}
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 and Petrolacosaurus (both of which resemble Archaeothyris) were found.
Archaeothyris lived in what is now Nova Scotia, 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. The "trees" (actually giant club mosses) were very tall, some, such as Lepidodendron, up to {{convert|50|m|ft|0}} tall. Archaeothyris and the other early amniotes lived in the moist vegetation on the forest ground, together with the more terrestrially adapted labyrinthodont amphibians.
See also
{{Portal|Paleontology}}
References
{{Reflist|2}}
Further reading
- {{cite book |title=The Origin & Evolution of Mammals |last=Kemp |first=T. S. |year=2005 |publisher=Oxford University Press |location=Oxford |isbn=978-0-19-850761-1 }}
External links
- [http://www.talkorigins.org/faqs/faq-transitional/part1b.html Transitional Vertebrate Fossils] - includes description of important transitional genera from reptile to mammal (includes a little information about Archaeothyris)
{{Synapsida|H.}}
{{Taxonbar|from=Q133034}}
Category:Carboniferous synapsids
Category:Carboniferous synapsids of North America
Category:Taxa named by Robert R. Reisz