Belongs within: Stereospondylomorpha.
The Trematosauria are a clade of temnospondyls defined by Yates & Warren (2000) as including all species closer to Trematosaurus than Parotosuchus.
Synapomorphies (from Yates & Warren 2000): Interorbital space greater than 50% of skull width at mid orbital level; stapedial foramen absent; sharp rimmed depressions absent at posterior end of ventral surface of parasphenoid plate; denticle patches absent from all three coronoids; chorda tympanic foramen located on preaticular; hamate process absent.
<==Trematosauria [Trematosauroidei] YW00
| i. s.: Lyrocephalus euri CZ79
|–+–Luzocephalus YW00
| `–Trematosauroidea YW00
| |–Thoosuchus jakovlevi YW00
| `–Lyrocephaliscus [Trematosauridae] YW00
| `–L. euri YW00
`–+–Metoposauroidea YW00
| |–Almasaurus habbazi Dutuit 1972 YW00, CZ79
| |–Buettneria perfecta YW00
| |–Apachesaurus PI05
| `–Metoposaurus Lydekker 1890 D07
| |–M. bakeri D07
| |–M. diagnosticus YW00
| |–M. heimi D07
| |–M. krasiejowensis D07
| |–M. maleriensis DDL04
| |–M. santaecrucis D07
| `–M. stuttgartiensis D07
`–+–Plagiosauroidea YW00
| |–Laidleria [Laidleriidae] YW00
| | `–L. gracilis Kitching 1958 CZ79
| `–Plagiosauridae YW00
| |–Plagiosternum danilovi YW00
| `–Plagiosaurus YW00
`–+–Brachyopoidea YW00
| |–Keratobrachyops australis YW00
| `–+–Brachyopidae YW00
| | |–Xenobrachyops allos YW00
| | |–Brachyops laticeps S87
| | `–Batrachosuchus YW00
| | `–‘Blinasaurus’ henwoodi YW00
| `–Chigutisauridae YW00
| |–Siderops kehli YW00
| `–Pelorocephalus Cabera 1944 YW00, D07 [incl. Chigutisaurus YW00]
| |–P. cacheutensis D07
| |–P. ischigualastensis D07
| |–P. mendozensis D07
| `–P. tenax D07
`–Rhytidosteoidea CZ79
|–Indobrachyopidae CZ79
| |–Derwentia warreni Cosgriff 1974 CZ79
| `–+–Indobrachyops panchetensis Van Huene & Sahni 1958 CZ79
| `–+–Rewana quadricuneata Howie 1972 CZ79
| `–Mahavisaurus CZ79
| |–M. australis (Lehmann 1966) [=Lyrosaurus australis] CZ79
| `–M. dentatus Lehmann 1966 CZ79
`–Rhytidosteidae YW00
| i. s.: Arcadia myriadens YW00
| Trucheosaurus YW00
|–Deltasaurus CZ79
| |–D. kimberleyensis Cosgriff 1965 CZ79
| `–D. pustulatus Cosgriff 1965 CZ79
`–+–Pneumatostega Cosgriff & Zawiskie 1979 CZ79
| `–*P. potamia Cosgriff & Zawiskie 1979 CZ79
`–+–Rhytidosteus capensis Owen 1884 CZ79
`–Peltostega CZ79
|–P. erici Wiman 1916 CZ79
`–P. wimani Nilsson 1946 CZ79
*Type species of generic name indicated
REFERENCES
[CZ79] Cosgriff, J. W., & J. M. Zawiskie. 1979. A new species of the Rhytidosteidae from the Lystrosaurus Zone and a review of the Rhytidosteoidea. Palaeontologia Africana 22: 1–27.
[DDL04] Datta, P. M., D. P. Das & Z.-X. Luo. 2004. A Late Triassic dromatheriid (Synapsida: Cynodontia) from India. Annals of Carnegie Museum 73 (2): 12–24.
[D07] Dixon, D. 2007. The Complete Illustrated Encyclopedia of Dinosaurs & Prehistoric Creatures. Hermes House: London.
[PI05] Parker, W. G., R. B. Irmis, S. J. Nesbitt, J. W. Martz & L. S. Browne. 2005. The Late Triassic pseudosuchian Revueltosaurus callenderi and its implications for the diversity of early ornithischian dinosaurs. Proceedings of the Royal Society of London Series B—Biological Sciences 272: 963–969.
[S87] Stephens, W. J. 1887. On the Biloela labyrinthodont (second notice). Proceedings of the Linnean Society of New South Wales, series 2, 1 (4): 1113–1121, pl. 14.
[YW00] Yates, A. M., & A. A. Warren. 2000. The phylogeny of the ‘higher’ temnospondyls (Vertebrata: Choanata) and its implications for the monophyly and origins of the Stereospondyli. Zoological Journal of the Linnean Society 128: 77–121.