Saber-toothed Cat (Smilodon)
- When: Pleistocene
(2.5 million to 10,000 years ago) - Where: North and South America
- What: Mammal
- Weight: 160–280 kg
- Length: 1.6–2.2 meters
- Diet: Carnivorous
- Discovered: 1842
Saltasaurus
- When: Late Cretaceous
(70–66 mya) - Where: South America
- What: Sauropod
- Weight: 6–8 metric tons
- Length: 12 meters
- Diet: Herbivorous
- Discovered: 1980
Sarcosuchus
- When: Early Cretaceous
(133–112 mya) - Where: Africa
- What: Crocodyliform
- Weight: 3.5–8 tons
- Length: 9–12 meters
- Diet: Carnivorous
- Discovered: 1940s
Sauroposeidon
- When: Early Cretaceous
(112 mya) - Where: North America
- What: Sauropod
- Weight: 50–60 metric tons
- Length: 34 meters
- Diet: Herbivorous
- Discovered: 2000
Scelidosaurus
- When: Early Jurassic
(196–183 mya) - Where: Europe
- What: Thyreophoran
- Weight: 270–320 kg
- Length: 4 meters
- Diet: Herbivorous
- Discovered: 1861
Shantungosaurus
- When: Late Cretaceous
(70–66 mya) - Where: Asia
- What: Hadrosaur
- Weight: 16 metric tons
- Length: 15 meters
- Diet: Herbivorous
- Discovered: 1973
Shastasaurus
- When: Late Triassic
(210 mya) - Where: North America
- What: Ichthyosaur
- Weight: 25–75 metric tons
- Length: 20 meters
- Diet: Piscivorous
- Discovered: 1895
Shonisaurus
- When: Late Triassic
(225 mya) - Where: North America
- What: Ichthyosaur
- Weight: 30–40 metric tons
- Length: 15 meters
- Diet: Piscivorous
- Discovered: 1976
Spinosaurus
- When: Early to Late Cretaceous
(112–93 mya) - Where: Africa
- What: Theropod
- Weight: 7–20 tons
- Length: 15–18 meters
- Diet: Carnivorous
- Discovered: 1912