The Therizinosaurus is an enemy that appears in Serious Sam: Double D. It is a large, blue feathered dinosaur that walks on two legs. It has very long claws, which it uses to attack enemies. Its back can be jumped on to reach higher areas.
Normally, the Therizinosaurus's only attack is to swat at the target with its claws. However, when it becomes modified by Mental, the Therizinosaurus obtains a machine that constantly fires light blue fireballs at the target. It will also try to get close to the target in order to slice the target with it's claws. The modified Therizinosaurus wears a mask, which can be destroyed. If the mask is destroyed, the Therizinosaurus will help whomever destroyed the mask and attack nearby enemies.
- Normal Therizinosauruses are completely harmless as long as the player doesn't shoot them or let an enemy hit them.
- It is highly recommended to shoot the modified Therizinosaurus in the face. With enough shots, the mask on it will break, which will stop the Therizinosaurus from firing at the player and instead focus on other enemies. This makes the Therizinosaurus a very useful distraction so that the player can focus on other enemies or kill the enemy the Therizinosaurus is attacking without fear that the enemy will attack back.
- Strong weapons, such as the LM32 Rocket Launcher and 12 Gauge Shotgun, work best against the Therizinosaurus. These weapons let the player quickly either kill it or get its facemask off thanks to how powerful they are.
- When paired with other enemies, the Therizinosaurus is a high threat. Its constant barrage of fireballs makes it difficult to dodge other enemy's attacks. Defeating or destroying its mask as soon as possible give the player much more breathing room to dodge other enemy projectiles and enemies themselves.