Science magazines
- Sonoran Pronghorn
- South Texas Ambrosia
- Southeastern Beach Mouse, Anastasia Island Beach Mouse
- Southern Acornshell
- Southern Clubshell
- Southern Combshell
- Southern Mountain Wild-buckwheat
- Southern Pigtoe
- Southern Sea Otter
- Southwestern Willow Flycatcher
- Speckled Pocketbook
- Spectacled Eider
- Spermolepis Hawaiiensis
- Spikedace
- Spotfin Chub
- Spreading Avens
- Spreading Navarretia
- Spring Creek Bladderpod
- Spring-loving Centaury
- Springville Clarkia