Parapleurota

Parapleurota is a clade of reptiles, characterized by the presence of a tympanic membrane in the ear. The crown reptile group Sauria is recognized as part of this clade. The earliest known member of the clade is the middle Permian genus Lanthanolania, classified as a member of the Millerettidae. Millerettids have previously been recognized as part of the Parareptilia, but this clade is likely polyphyletic, with millerettids more closely related to neodiapsids than previously recognized.^[1]

Parapleurota Temporal range: Middle Permian–present PreꞒ Ꞓ O S D C P T J K Pg N
Skull of the extinct Milleropsis pricei (a millerettid)
Skull of the modern rhinoceros iguana (Cyclura cornuta)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Diapsida
Clade:	Neoreptilia
Clade:	Parapleurota Jenkins et al., 2025
Subgroups
†Millerettidae Neodiapsida

Characteristics

Tympanic hearing

Diagram of middle ear evolution in amniotes

Members of the Parapleurota are distinguished by the presence of a tympanic membrane inside the ear. This allows airborne sounds to be efficiently transmitted through the ear, and is typically associated with heightened hearing ability.^[2][3] Developmental biology and the fossil record both indicate that the presence of a tympanic ear is ancestral to extant reptiles.^[4] Parapleurota displays stepwise evolution of the tympanic fossa, an opening in the back of the skull that holds the membrane. In basal members of the clade, the membrane is supported by the squamosal and quadratojugal, while in Neodiapsida it is mostly or entirely supported by the quadrate.^[1] Tympanic membranes also evolved independently in Procolophonia and stem-mammals.^[1][4]

Classification

Historically, the clade Millerettidae has been united with Mesosauridae and Procolophonomorpha within the group Parareptilia.^[5][6] However, reappraisal of millerettid anatomy has identified numerous features in the skull that are shared with neodiapsids and not parareptiles.^[7][8] The clade Parapleurota was first recovered phylogenetically and defined by Jenkins et al. (2025) as the clade containing the most recent common ancestor of Milleretta rubidgei and Youngina capensis, but not Petrolacosaurus kansensis, Orovenator mayorum, Procolophon trigoniceps, or Mesosaurus tenuidens.^[1]

This cladogram follows Jenkins et al. (2025). Traditional "parareptiles" are highlighted in orange:^[1]

Reptilia

†Araeoscelidia †Bolosauridae Neoreptilia †Ankyramorpha †Acleistorhinidae †Pareiasauromorpha †Procolophonoidea †Mesosauridae †Cabarzia †Ascendonanus †Orovenator Parapleurota †Millerettidae †Lanthanolania †Broomia †Milleropsis †Milleretta †Millerosaurus Neodiapsida †Younginidae †EAZ younginiform †Youngina †Tangasauridae †Acerosodontosaurus †Hovasaurus †Thadeosaurus †Weigeltisauridae †Claudiosaurus Sauria Lepidosauromorpha Archosauromorpha