- sabinensis
- Sacalia
- sacculus
- sagittal
- saharica
- salvinii
- San Cristóbal Island
- Santa Cruz Island
- Santa Maria Island
- Santiago Island
- savanna
- scale
- schlegelii
- scorpioides
- scripta
- scutata
- scutellate
- scutes
- seam
- secondary spermatocytes
- seminiferous tubule
- senegalensis
- sensu lato
- sensu stricto
- septate
- septum
- seriei
- serology
- serpentina
- serrata
- serrate
- Sertoli cells
- Sertoli nuclei
- Sertoli plumes
- sextuberculata
- sexual dichromatism
- sexual dimorphism
- seychellensis
- sheath
- shiui
- Siebenrockiella
- signata
- silvatica
- sinensis
- sinuatus
- skin sterols
- smithii
- somatic
- sonoriense
- spekii
- spengleri
- spermatids
- spermatocytogenesis
- spermatogenesis
- spermatogenic cycle
- spermatogonia
- spermatozoa
- spermiogenesis
- spinifera
- spinosa
- spixii
- splenial
- spooneri
- squamosal bones
- stapedial artery
- stapedio-temporale foramen
- stapedius
- stapes
- Staurotypus
- steindachneri
- stejnegeri
- steppe
- Sternotherus
- sternum
- striae
- subglobosa
- submarginals
- submetacentric
- subniger
- subocular
- subplana
- subrubrum
- subtelocentric
- subtrijuga
- sulcata
- sulcus
- supraangular
- supracaudal scutes
- supramarginal scutes
- supranasal scales
- supraoccipital bone
- suprapygal
- supratemporal
- surangular bones
- suture
- suwanniensis
- swinhoei
- sylhetensis
- symbiosis
- sympatric
- symphysial ridge
- symphysis
- synonym
- syntype
- systematics