Sauria is the clade of diapsids containing the most recent common ancestor of Archosauria (which includes crocodilians and birds) and Lepidosauria (which includes squamates and the tuatara), and all its descendants. Since most molecular phylogenies recover turtles as more closely related to archosaurs than to lepidosaurs as part of Archelosauria, Sauria can be considered the crown group of diapsids, or reptiles in general. Depending on the systematics, Sauria includes all modern reptiles or most of them (including birds, a type of archosaur) as well as various extinct groups.

Sauria lies within the larger total group Sauropsida, which also contains various stem-reptiles which are more closely related to reptiles than to mammals. Prior to its modern usage, "Sauria" was used as a name for the suborder occupied by lizards, which included crocodilians in 18th century classifications.

Systematics

Sauria was historically used as a partial equivalent for Squamata (which contains lizards and snakes). The redefinition to cover the last common ancestor of archosaurs and lepidosaurs was the result of papers by Jacques Gauthier and colleagues in the 1980s.

Genomic studies and comprehensive studies in the fossil record suggest that turtles are closely related to archosaurs as part of Sauria, and not to the non-saurian parareptiles as previously thought.

Synapomorphies

The synapomorphies or characters that unite the clade Sauria also help them be distinguished from stem-saurians in Diapsida or stem-reptiles in clade Sauropsida in the following categories based on the following regions of the body.

  • Cephalad region Dorsal origin of temporal musculature Loss of caniniform region in maxillary tooth row External nares close to the midline Postparietal absent Squamosal mainly restricted to top of skull The occipital flange of the squamosal is little exposed on the occiput Anterior process of squamosal narrow Quadrate exposed laterally Unossified dorsal process of stapes Stapes slender
  • Trunk region Sacral ribs oriented laterally Ontogenetic fusion of caudal ribs Trunk ribs mostly single headed
  • Pectoral region Cleithrum absent
  • Pelvic region Modified ilium
  • Limb region Tubular bone lost Entepicondylar foramen absent Radius as long as ulna Small proximal carpals and tarsal Fifth distal tarsal absent Short and stout fifth or hooked metatarsal Perforating foramen of manus lost

However, some of these characters might be lost or modified in several lineages, particularly among birds and turtles; it is best to see these characters as the ancestral features that were present in the ancestral saurian.

Phylogeny

The cladogram shown below follows the most likely result found by an analysis of turtle relationships using both fossil and genetic evidence by M.S. Lee, in 2013. This study found Eunotosaurus, usually regarded as a turtle relative, to be only very distantly related to turtles in the clade Parareptilia.

Diapsida †Araeoscelidia Neodiapsida †Claudiosaurus †Younginiformes Sauria Lepidosauromorpha Archelosauria Pantestudines †Eosauropterygia †Placodontia †Sinosaurosphargis †Odontochelys Testudinata †Proganochelys Testudines Archosauromorpha †Choristodera †Prolacertiformes †Rhynchosauria †Trilophosaurus Archosauriformes
Diapsida†Araeoscelidia Neodiapsida †Claudiosaurus †Younginiformes Sauria Lepidosauromorpha Archelosauria Pantestudines †Eosauropterygia †Placodontia †Sinosaurosphargis †Odontochelys Testudinata †Proganochelys Testudines Archosauromorpha †Choristodera †Prolacertiformes †Rhynchosauria †Trilophosaurus Archosauriformes
†Araeoscelidia
Neodiapsida†Claudiosaurus †Younginiformes Sauria Lepidosauromorpha Archelosauria Pantestudines †Eosauropterygia †Placodontia †Sinosaurosphargis †Odontochelys Testudinata †Proganochelys Testudines Archosauromorpha †Choristodera †Prolacertiformes †Rhynchosauria †Trilophosaurus Archosauriformes
†Claudiosaurus
†Younginiformes Sauria Lepidosauromorpha Archelosauria Pantestudines †Eosauropterygia †Placodontia †Sinosaurosphargis †Odontochelys Testudinata †Proganochelys Testudines Archosauromorpha †Choristodera †Prolacertiformes †Rhynchosauria †Trilophosaurus Archosauriformes
†Younginiformes
SauriaLepidosauromorpha Archelosauria Pantestudines †Eosauropterygia †Placodontia †Sinosaurosphargis †Odontochelys Testudinata †Proganochelys Testudines Archosauromorpha †Choristodera †Prolacertiformes †Rhynchosauria †Trilophosaurus Archosauriformes
Lepidosauromorpha
ArchelosauriaPantestudines †Eosauropterygia †Placodontia †Sinosaurosphargis †Odontochelys Testudinata †Proganochelys Testudines Archosauromorpha †Choristodera †Prolacertiformes †Rhynchosauria †Trilophosaurus Archosauriformes
Pantestudines†Eosauropterygia †Placodontia †Sinosaurosphargis †Odontochelys Testudinata †Proganochelys Testudines
†Eosauropterygia
†Placodontia †Sinosaurosphargis †Odontochelys Testudinata †Proganochelys Testudines
†Placodontia
†Sinosaurosphargis †Odontochelys Testudinata †Proganochelys Testudines
†Sinosaurosphargis
†Odontochelys Testudinata †Proganochelys Testudines
†Odontochelys
Testudinata†Proganochelys Testudines
†Proganochelys
Testudines
Archosauromorpha†Choristodera †Prolacertiformes †Rhynchosauria †Trilophosaurus Archosauriformes
†Choristodera
†Prolacertiformes †Rhynchosauria †Trilophosaurus Archosauriformes
†Prolacertiformes
†Rhynchosauria †Trilophosaurus Archosauriformes
†Rhynchosauria †Trilophosaurus
†Rhynchosauria
†Trilophosaurus
Archosauriformes

The cladogram below follows the most likely result found by another analysis of turtle relationships, this one using only fossil evidence, published by Rainer Schoch and Hans-Dieter Sues in 2015. This study found Eunotosaurus to be an actual early stem-turtle, though other versions of the analysis found weak support for it as a parareptile.

SauriaAnkylopoda Lepidosauromorpha †Kuehneosauridae Lepidosauria Rhynchocephalia Squamata Pantestudines †Sauropterygia †Eosauropterygia †Placodontia †Sinosaurosphargis †Eunotosaurus †Pappochelys †Odontochelys Testudinata †Proganochelys Testudines Archosauromorpha
AnkylopodaLepidosauromorpha †Kuehneosauridae Lepidosauria Rhynchocephalia Squamata Pantestudines †Sauropterygia †Eosauropterygia †Placodontia †Sinosaurosphargis †Eunotosaurus †Pappochelys †Odontochelys Testudinata †Proganochelys Testudines
Lepidosauromorpha †Kuehneosauridae Lepidosauria Rhynchocephalia Squamata Pantestudines †Sauropterygia †Eosauropterygia †Placodontia †Sinosaurosphargis †Eunotosaurus †Pappochelys †Odontochelys Testudinata †Proganochelys Testudines
Lepidosauromorpha†Kuehneosauridae Lepidosauria Rhynchocephalia Squamata
†Kuehneosauridae
LepidosauriaRhynchocephalia Squamata
Rhynchocephalia
Squamata
Pantestudines†Sauropterygia †Eosauropterygia †Placodontia †Sinosaurosphargis †Eunotosaurus †Pappochelys †Odontochelys Testudinata †Proganochelys Testudines
†Sauropterygia†Eosauropterygia †Placodontia †Sinosaurosphargis
†Eosauropterygia
†Placodontia †Sinosaurosphargis
†Placodontia
†Sinosaurosphargis
†Eunotosaurus †Pappochelys †Odontochelys Testudinata †Proganochelys Testudines
†Eunotosaurus
†Pappochelys †Odontochelys Testudinata †Proganochelys Testudines
†Pappochelys
†Odontochelys Testudinata †Proganochelys Testudines
†Odontochelys
Testudinata†Proganochelys Testudines
†Proganochelys
Testudines
Archosauromorpha

The cladogram below follows the analysis of Li et al. (2018). It places turtles within Diapsida but outside of Sauria (the Lepidosauromorpha + Archosauromorpha clade).

†Parareptilia
Eureptilia†Captorhinidae †Paleothyris Diapsida †Araeoscelidia †Hovasaurus †Youngina crown‑group Pantestudines †Acerosodontosaurus †Claudiosaurus †Eunotosaurus †Pappochelys †Eorhynchochelys †Odontochelys Testudinata Sauria Lepidosauromorpha †Kuehneosauridae †Saurosphargidae †Eosauropterygia †Placodus Lepidosauria Rhynchocephalia Squamata Archosauromorpha †Rhynchosauria †Trilophosaurus †Prolacerta Archosauriformes
†Captorhinidae
†Paleothyris Diapsida †Araeoscelidia †Hovasaurus †Youngina crown‑group Pantestudines †Acerosodontosaurus †Claudiosaurus †Eunotosaurus †Pappochelys †Eorhynchochelys †Odontochelys Testudinata Sauria Lepidosauromorpha †Kuehneosauridae †Saurosphargidae †Eosauropterygia †Placodus Lepidosauria Rhynchocephalia Squamata Archosauromorpha †Rhynchosauria †Trilophosaurus †Prolacerta Archosauriformes
†Paleothyris
Diapsida†Araeoscelidia †Hovasaurus †Youngina crown‑group Pantestudines †Acerosodontosaurus †Claudiosaurus †Eunotosaurus †Pappochelys †Eorhynchochelys †Odontochelys Testudinata Sauria Lepidosauromorpha †Kuehneosauridae †Saurosphargidae †Eosauropterygia †Placodus Lepidosauria Rhynchocephalia Squamata Archosauromorpha †Rhynchosauria †Trilophosaurus †Prolacerta Archosauriformes
†Araeoscelidia
†Hovasaurus †Youngina crown‑group Pantestudines †Acerosodontosaurus †Claudiosaurus †Eunotosaurus †Pappochelys †Eorhynchochelys †Odontochelys Testudinata Sauria Lepidosauromorpha †Kuehneosauridae †Saurosphargidae †Eosauropterygia †Placodus Lepidosauria Rhynchocephalia Squamata Archosauromorpha †Rhynchosauria †Trilophosaurus †Prolacerta Archosauriformes
†Hovasaurus
†Youngina crown‑group Pantestudines †Acerosodontosaurus †Claudiosaurus †Eunotosaurus †Pappochelys †Eorhynchochelys †Odontochelys Testudinata Sauria Lepidosauromorpha †Kuehneosauridae †Saurosphargidae †Eosauropterygia †Placodus Lepidosauria Rhynchocephalia Squamata Archosauromorpha †Rhynchosauria †Trilophosaurus †Prolacerta Archosauriformes
†Youngina
crown‑groupPantestudines †Acerosodontosaurus †Claudiosaurus †Eunotosaurus †Pappochelys †Eorhynchochelys †Odontochelys Testudinata Sauria Lepidosauromorpha †Kuehneosauridae †Saurosphargidae †Eosauropterygia †Placodus Lepidosauria Rhynchocephalia Squamata Archosauromorpha †Rhynchosauria †Trilophosaurus †Prolacerta Archosauriformes
Pantestudines†Acerosodontosaurus †Claudiosaurus †Eunotosaurus †Pappochelys †Eorhynchochelys †Odontochelys Testudinata
†Acerosodontosaurus †Claudiosaurus
†Acerosodontosaurus
†Claudiosaurus
†Eunotosaurus †Pappochelys †Eorhynchochelys †Odontochelys Testudinata
†Eunotosaurus
†Pappochelys †Eorhynchochelys †Odontochelys Testudinata
†Pappochelys
†Eorhynchochelys †Odontochelys Testudinata
†Eorhynchochelys
†Odontochelys Testudinata
†Odontochelys
Testudinata
SauriaLepidosauromorpha †Kuehneosauridae †Saurosphargidae †Eosauropterygia †Placodus Lepidosauria Rhynchocephalia Squamata Archosauromorpha †Rhynchosauria †Trilophosaurus †Prolacerta Archosauriformes
Lepidosauromorpha†Kuehneosauridae †Saurosphargidae †Eosauropterygia †Placodus Lepidosauria Rhynchocephalia Squamata
†Kuehneosauridae †Saurosphargidae †Eosauropterygia †Placodus
†Kuehneosauridae
†Saurosphargidae †Eosauropterygia †Placodus
†Saurosphargidae
†Eosauropterygia †Placodus
†Eosauropterygia
†Placodus
LepidosauriaRhynchocephalia Squamata
Rhynchocephalia
Squamata
Archosauromorpha†Rhynchosauria †Trilophosaurus †Prolacerta Archosauriformes
†Rhynchosauria †Trilophosaurus
†Rhynchosauria
†Trilophosaurus
†Prolacerta Archosauriformes
†Prolacerta
Archosauriformes

The following cladogram was found by Simões et al. (2022):

Neoreptilia†Procolophonomorpha Neodiapsida †Younginiformes †Eunotosaurus †Weigeltisauridae Sauria Lepidosauromorpha Rhynchocephalia (tuatara and their extinct relatives) Squamata (lizards and snakes) Archelosauria Pantestudines (turtles and extinct relatives) Archosauromorpha †Ichthyosauromorpha †Sauropterygia †Thalattosauria †Protorosauria †Protorosaurus †Tanystropheidae †Drepanosauromorpha †Kuehneosauridae †Allokotosauria †Rhynchosauria Archosauriformes (crocodiles, birds, and their extinct relatives)
†Procolophonomorpha
Neodiapsida†Younginiformes †Eunotosaurus †Weigeltisauridae Sauria Lepidosauromorpha Rhynchocephalia (tuatara and their extinct relatives) Squamata (lizards and snakes) Archelosauria Pantestudines (turtles and extinct relatives) Archosauromorpha †Ichthyosauromorpha †Sauropterygia †Thalattosauria †Protorosauria †Protorosaurus †Tanystropheidae †Drepanosauromorpha †Kuehneosauridae †Allokotosauria †Rhynchosauria Archosauriformes (crocodiles, birds, and their extinct relatives)
†Younginiformes
†Eunotosaurus †Weigeltisauridae Sauria Lepidosauromorpha Rhynchocephalia (tuatara and their extinct relatives) Squamata (lizards and snakes) Archelosauria Pantestudines (turtles and extinct relatives) Archosauromorpha †Ichthyosauromorpha †Sauropterygia †Thalattosauria †Protorosauria †Protorosaurus †Tanystropheidae †Drepanosauromorpha †Kuehneosauridae †Allokotosauria †Rhynchosauria Archosauriformes (crocodiles, birds, and their extinct relatives)
†Eunotosaurus
†Weigeltisauridae Sauria Lepidosauromorpha Rhynchocephalia (tuatara and their extinct relatives) Squamata (lizards and snakes) Archelosauria Pantestudines (turtles and extinct relatives) Archosauromorpha †Ichthyosauromorpha †Sauropterygia †Thalattosauria †Protorosauria †Protorosaurus †Tanystropheidae †Drepanosauromorpha †Kuehneosauridae †Allokotosauria †Rhynchosauria Archosauriformes (crocodiles, birds, and their extinct relatives)
†Weigeltisauridae
SauriaLepidosauromorpha Rhynchocephalia (tuatara and their extinct relatives) Squamata (lizards and snakes) Archelosauria Pantestudines (turtles and extinct relatives) Archosauromorpha †Ichthyosauromorpha †Sauropterygia †Thalattosauria †Protorosauria †Protorosaurus †Tanystropheidae †Drepanosauromorpha †Kuehneosauridae †Allokotosauria †Rhynchosauria Archosauriformes (crocodiles, birds, and their extinct relatives)
LepidosauromorphaRhynchocephalia (tuatara and their extinct relatives) Squamata (lizards and snakes)
Rhynchocephalia (tuatara and their extinct relatives)
Squamata (lizards and snakes)
ArchelosauriaPantestudines (turtles and extinct relatives) Archosauromorpha †Ichthyosauromorpha †Sauropterygia †Thalattosauria †Protorosauria †Protorosaurus †Tanystropheidae †Drepanosauromorpha †Kuehneosauridae †Allokotosauria †Rhynchosauria Archosauriformes (crocodiles, birds, and their extinct relatives)
Pantestudines (turtles and extinct relatives)
Archosauromorpha†Ichthyosauromorpha †Sauropterygia †Thalattosauria †Protorosauria †Protorosaurus †Tanystropheidae †Drepanosauromorpha †Kuehneosauridae †Allokotosauria †Rhynchosauria Archosauriformes (crocodiles, birds, and their extinct relatives)
†Ichthyosauromorpha †Sauropterygia †Thalattosauria
†Ichthyosauromorpha
†Sauropterygia †Thalattosauria
†Sauropterygia
†Thalattosauria
†Protorosauria †Protorosaurus †Tanystropheidae †Drepanosauromorpha †Kuehneosauridae †Allokotosauria †Rhynchosauria Archosauriformes (crocodiles, birds, and their extinct relatives)
†Protorosauria†Protorosaurus †Tanystropheidae †Drepanosauromorpha †Kuehneosauridae
†Protorosaurus
†Tanystropheidae †Drepanosauromorpha †Kuehneosauridae
†Tanystropheidae
†Drepanosauromorpha †Kuehneosauridae
†Drepanosauromorpha
†Kuehneosauridae
†Allokotosauria †Rhynchosauria Archosauriformes (crocodiles, birds, and their extinct relatives)
†Allokotosauria †Rhynchosauria
†Allokotosauria
†Rhynchosauria
Archosauriformes (crocodiles, birds, and their extinct relatives)

External links

  • Media related to Sauria at Wikimedia Commons
  • Data related to Sauria at Wikispecies