This is the Jurassic dimension. The portal block needed to get here and the biomes included are listed below. To open a portal click on it with the bone wand, which has been enchanted with the Enchantment of Time Reversal. The Enchantment of Time Reversal can be obtained from a Palaeobotanist villager, or as a rare chance on the crafting table. Note that the biomes in these dimensions are able to be extremely large, up to several thousand blocks across. Travelling 10 blocks in the overworld will move you 100 in a custom dimension though, and the main mod's config has an option to allow you to increase that if you felt the need. There are achievements for finding all biomes (biomes listed on the same line are regarded as equally valid for those achievements):
Jurassic: Portal block: Ginkgo Planks
- Jurassic Deep Ocean
- Jurassic Shallow Ocean
- Jurassic Coral Nursery
- Jurassic Glass Sponge Reef
- Jurassic Driftwood Rafts
- Jurassic Volcanic Beach
- Jurassic Beach
- Jurassic Boulders
- Jurassic Coniferous Forest/Forest Hills/Mountains
- Jurassic Desert
- Jurassic Desert Gulley
- Jurassic Desert Islands
- Jurassic Desert Edge
- Jurassic Fern Pasture
- Jurassic Floodplain
- Jurassic Forested Floodplain
- Jurassic Garrigue
- Jurassic Copse
- Jurassic Cycad Thickets
- Jurassic Ginkgo Parkland
- Jurassic Ginkgo Woodland
- Jurassic Lakes
- Jurassic Caldera Island Cliffs
- Jurassic Caldera Island Interior
- Jurassic Horsetail Mire
- Jurassic Mudbanks
- Jurassic Mudflats
- Jurassic Outcrops
- Jurassic River
- Jurassic Riverbanks
- Jurassic Rough Hills
- Jurassic Sandy Atolls
- Jurassic Sandy Atolls Hillocks
- Jurassic Windswept Isles
- Jurassic Southern Taiga
- Jurassic Southern Taiga Forest
- Jurassic Southern Taiga Tors
- Creeks (regarded as subversions of their surrounding biome and not counted towards biome-discovery achievements)