Sa
- Sacisaurus,
- Saichangurvel,
- Saltoposuchidae †
- Saltoposuchus †
- Saltopus,
- Sanchiaosaurus Young, 1965 †
- Saniwa australis,
- Santaisaurus,
- Santanadactylus de Buisonje, 1980 †
- Sapheosauridae,
- Sarcosuchus Broin & Taquet, 1966 †
- Sarmatosuchus,
- Sauranodonti,
- Sauria,
- Sauria,
- Sauroeidepus,
- Sauromalus,
- Sauropithecoides
- Sauropterygia †
- Sauropterygia,
- Saurosphargidae Li et al., 2011 †
- Saurosphargidae,
- Saurosphargis Frech, 1903 †
- Saurosphargis,
- Saurosternidae,
- Saurosternon
Sc
- Scandensia,
- Scaphognathidae,
- Scaphognathus Wagner, 1861 †
- Scarrisaurus,
- Sceloporus,
- Scincogekkonomorpha,
- Scleroglossa,
- Scleromochlidae
- Scleromochlidae Huene, 1914 †
- Scleromochlus Woodward, 1907 †
- Scleromochlus,
Se
- Sebecidae †
- Sebecus †
- Seemannia palaeotriadica,
- Seemannia,
- Serpianosaurus Rieppel, 1989 †
Sh
- Shamosuchus †
- Shansisuchidae,
- Shansisuchus heiyuekouensis,
- Shansisuchus,
- Sharivopterygia,
†Sharovipteryx Cowen 1981
- †Sharovipteryx mirabilis Sharov 1971
Animalia → Diapsida → Prolacertiformes → Podopterygidae
- Shastasauridae Merriam, 1895 †
- Shastasaurinae Merriam, 1908 †
- Shastasaurus Merriam, 1895 †
- Shenzhoupterus Lü et al., 2008 †
- Shimmelia,
- Shokawa
- Shonisaurus Camp, 1976 †
Si
- Sikannisuchus,
- Silesauridae
- Silesaurus,
- Simiosauria,
- Simoedosauridae,
- Simoedosaurus,
- Simolestes Andrews, 1909 †
- Simosauria
- Simosauridae Romer, 1965 †
- Simosaurus Meyer, 1842 †
- Simosuchus †
- Sinocyamodus
- Sinocyamodus Chun, 2000 †
- Sinopliosaurus G. Young, 1820 †
- Sinopterus Wang & Zhou, 2003 †
- Sinosaurosphargis
- Sinosaurosphargis Li et al., 2011 †
- Siroccopteryx Mader & Kellner, 1999 †
Sm
- Smilosuchus,
- Smok,
So
- Sokotosaurus †
- Sophineta
- Sordes Sharov, 1971 †
Sp
- Spathorhynchus
- Sphaerodactylus,
- Sphagesauridae †
- Sphagesaurus †
- Sphenocondor,
- Sphenodonta,
- Sphenodontia
- Sphenodontidae,
- Sphenosuchia †
- Sphenosuchidae †
- Sphenosuchus †
- Sphodrosaurus,
- Spinoaequalis
†Spinosuchus Huene 1932
- †Spinosuchus caseanus Huene 1932
Reptilia → Diapsida → Trilophosauridae
Sq
- Squamata
St
- Stagonolepididae Lydekker, 1887 †
- Stegomosuchus †
- Stellio,
- Steneosaurus †
- Stenocercus,
- Stenopterygiidae Kuhn, 1934 †
- Stenopterygius Jaekel, 1904 †
- Sthenarosaurus Watson, 1909 †
- Stomatosuchidae †
- Stomatosuchus †
- Stomerosuchus †
- Stratesaurus,
- Strigosuchus licinus,
- Strigosuchus,
- Styxosaurus Welles, 1943 †
Su
- Suchoprion,
- Sulcusuchus Gasparini & Spalletti, 1997 †
- Sulmosaurus,
- Suzanniwana,
Sw
- Swainiguanoides,
Sy
- Symptosuchus †