Protorothyrididae is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

of small, lizard-like reptiles belonging to

Eureptilia Sauropsida (Greek for "lizard faces") is a clade of amniotes, broadly equivalent to the class Reptilia, though typically used in a broader sense to also include extinct stem-group relatives of modern reptiles and birds (which, as theropod dinos ...

. Their skulls did not have

fenestra A fenestra (fenestration; : fenestrae or fenestrations) is any small opening or pore, commonly used as a term in the biology, biological sciences. It is the Latin word for "window", and is used in various fields to describe a pore in an anatomy, ...

e, like the more derived diapsids. Protorothyridids lived from the Late Carboniferous to

Early Permian 01 or 01 may refer to: * The year 2001, or any year ending with 01 * The month of January * 1 (number) Music * '01 (Richard Müller album), ''01'' (Richard Müller album), 2001 * 01 (Urban Zakapa album), ''01'' (Urban Zakapa album), 2011 * ''01011 ...

periods, in what is now

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

. Many genera of primitive reptiles were thought to be protorothyridids. ''

Brouffia ''Brouffia'' is an extinct genus of Late Carboniferous (late Westphalian stage) basal reptile known from Plzeň of Czech Republic. It is known from a single partial skeleton, the holotype ČGH III B.21.C.587 and MP 451 (part and ...

'', ''

Coelostegus ''Coelostegus'' is an extinct genus of Late Carboniferous (late Westphalian stage) basal reptile known from Plzeň of Czech Republic. It is known from the holotype ČGH 3027, a partial skeleton of an immature individual. It was collected i ...

'', ''

Paleothyris ''Paleothyris'' was a small, agile, anapsid romeriidan reptile which lived in the Moscovian (Carboniferous) age of the Late Carboniferous in Nova Scotia. Description ''Paleothyris'' had sharp teeth and large eyes, meaning that it was likely ...

'' and ''

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, ...

'', for example, were found to be more basal

eureptile Sauropsida (Greek for "lizard faces") is a clade of amniotes, broadly equivalent to the class Reptilia, though typically used in a broader sense to also include extinct stem-group relatives of modern reptiles and birds (which, as theropod dinosaur ...

s in Muller and Reisz (2006), making the family as historically defined

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

, though three genera, ''

Protorothyris ''Protorothyris'' is an extinct genus of Early Permian protorothyridid known from Texas and West Virginia of the United States. It was first named by Llewellyn Ivor Price in 1937 and the type species is ''Protorothyris archeri''. ''P. archeri'' ...

Anthracodromeus ''Anthracodromeus'' is an extinct genus of Late Carboniferous (late Westphalian (stage), Westphalian stage) "Protorothyrididae, protorothyridid" tetrapods known from Ohio. It is known from the holotype American Museum of Natural History, AMNH&nbs ...

,'' and ''

Cephalerpeton ''Cephalerpeton'' is an extinct genus of " protorothyridid" tetrapods known from the Late Carboniferous (late Westphalian stage) of Illinois. It is known from the holotype YPM 796, a partial skeleton. It was collected in the Mazon Creek s ...

'', were recovered as a

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

group. ''Anthracodromeus'', ''Paleothyris'', and ''Protorothyris'' were recovered as a monophyletic group in Ford and Benson (2020) (who did not sample ''Cephalerpeton''), who recovered them as more derived than

captorhinids Captorhinidae is an extinct family of tetrapods, traditionally considered primitive reptiles, known from the late Carboniferous to the Late Permian. They had a cosmopolitan distribution across Pangea. Description Captorhinids are a clade of sm ...

and ''Hylonomus'', but less so than araeoscelidians. ''Anthracodromeus'' is the earliest known reptile to display adaptations to

climbing Climbing is the activity of using one's hands, feet, or other parts of the body to ascend a steep topographical object that can range from the world's tallest mountains (e.g. the eight thousanders) to small boulders. Climbing is done for locom ...

. The majority of phylogenetic studies recover protorothyridids as basal members of Eureptilia; however, Simões ''et al.'' (2022) recover them as

stem Stem or STEM most commonly refers to: * Plant stem, a structural axis of a vascular plant * Stem group * Science, technology, engineering, and mathematics Stem or STEM can also refer to: Language and writing * Word stem, part of a word respon ...

amniote Amniotes are tetrapod vertebrate animals belonging to the clade Amniota, a large group that comprises the vast majority of living terrestrial animal, terrestrial and semiaquatic vertebrates. Amniotes evolution, evolved from amphibious Stem tet ...

s instead.

References

Prehistoric reptile families Paraphyletic groups Taxa named by Llewellyn Ivor Price {{paleo-reptile-stub