PREHISTORIC FARM WIKI
How to Get Mosasaurus in Prehistoric Farm
Get 
Mosasaurus from Panthalassa fossils, a fishing Sea Egg or the Mosasaurus Hunt egg drop. Compare the requirements and chances.
Three ways to get Mosasaurus
Mosasaurus is a Legendary swimmer in the Panthalassa collection. You can work toward its fossil DNA set, fish for its Sea Egg, or roll an egg reward from the Mosasaurus Hunt boss.
This guide covers normal Mosasaurus. True Mosasaurus belongs to 
Late Cretaceous and requires the Forgotten Shovel route instead.
| Route | Requirement | Chance |
|---|---|---|
| Panthalassa fossils | Three matching Mosasaurus fossils | Individual fossil chance not confirmed |
| Fishing Sea Egg | Catch a Mosasaurus Sea Egg | 0.03% listed base chance; 3% of the Sea Egg pool |
| Mosasaurus Hunt | Defeat the boss and qualify for its egg roll | 1% per eligible player; exact damage cutoff unconfirmed |
Complete the Panthalassa fossil set
Unlock Panthalassa through Kai's quest at the Devonian whirlpool, then use its underwater fossil collection. The Mosasaurus collection panel uses three matching fossils for a completed DNA set.
Take the completed set to the DNA Lab on Home Island for a Mosasaurus egg. Individual Mosasaurus fossil odds are not confirmed.
On the map: Below-left of 
Devonian Island, inside the green circle. View on map
Fish for a Mosasaurus Sea Egg
Fishing has a listed 1% base Sea Egg chance. Mosasaurus accounts for 3% of that Sea Egg pool, giving a listed base Mosasaurus fishing chance of 0.03%.
These figures describe the fishing helper's base chances. A boss egg reward uses a separate roll. Check the Fishing guide for rods, depth ranges and the other Sea Eggs.
Fight the Mosasaurus Hunt boss
The recorded Mosasaurus Hunt starts with 9,800 HP and becomes enraged at half health, 4,900 HP. Harpoons deal 30 damage, and players can work together on the encounter.
The wiki records an approximately 500-damage contribution, about 5% of boss health, for egg eligibility. The exact cutoff is not confirmed. Eligible players have a listed 1% chance of receiving a Mosasaurus egg.
Listed defeat rewards are 700 XP and 3,000 coins. Mosasaurus boss fights also supply the Lock Fragments used in the Raptor X questline. The spawn schedule is not confirmed.
Hatch and ride Mosasaurus
Mosasaurus is Legendary, with a listed 20-minute hatch timer. Its calculated normal-growth chart reaches Subadult at 3 hours 12 minutes, Adult at 8 hours and Elder at 16 hours from hatching.
Rideability starts at Subadult. Keep Belly above 50% for growth and use the swimming speed chart to compare Mosasaurus with other swimmers.
Mosasaurus questions
Is the fishing chance also 1%?
The total Sea Egg chance is 1%. Mosasaurus has a 3% share of that pool, producing a listed 0.03% base fishing chance. The boss egg roll is separately listed at 1% for eligible players.
How many Mosasaurus fossils do I need?
Three matching fossils complete the normal Mosasaurus DNA set.
Is True Mosasaurus obtained the same way?
No. True Mosasaurus uses the Late Cretaceous fossil route, with the Forgotten Shovel and a five-fossil set.