Dinosaurs, among other prehistoric creatures such as pterodactyls, were trapped alive in tree sap in the abandoned mines in the Gravity Falls Forest. The summer heat is causing the tree sap to melt, slowly releasing the dinosaurs and others from the sap.
At the end of the Gravity Falls Main Title Theme, the pterodactyl makes an appearance in a photograph.
In "The Time Traveler's Pig," when Blendin Blandin's wrist-worn device malfunctions, a scene from "Land Before Swine" with dinosaurs trapped in tree sap is shown on his jacket. Later, when Dipper and Mabel go back to the past, they are attacked by a Allosaurus.
In "Land Before Swine," the pterodactyl escapes from the tree sap and begins terrorizing the town and ends up stealing Waddles. It retreats to the abandoned mines, where other dinosaurs are seen trying to escape. It also had an egg which hatched into a baby pterodactyl that ate Old Man McGucket. In the end, the pterodactyl and dinosaurs were trapped in the abandoned mines.
Mabel gave Dipper a dinosaur sticker saying "Ext-Roar-Dinary" in "The Golf War."
In "Weirdmageddon 3: Take Back The Falls," the Tyrannosaurus is attached to the Shacktron's left arm, its head and arms freed to use as a weapon against Bill Cipher and his henchmaniacs. The Tyrannosaurus succeeds in ripping out Bill's eye while in combat with him, temporarily disabling the demon and allowing the rescue team to parachute past him to the Fearamid, but is prevented from fighting Bill further once Bill dismantles the rest of the Shacktron.
A number of species are seen trapped in tree sap in the abandoned mines. They are all from different periods of the Mesozoic. Some of them are:
- Tyrannosaurus Rex
- Unknown dinosaur (only its tail was visible, it was possibly a Spinosaurus)
- Intro: "Gravity Falls Main Title Theme"
- 203. "The Golf War" (pictured)
- 207. "Society of the Blind Eye" ( )
- 218. "Weirdmageddon Part 1"
- 220. "Weirdmageddon 3: Take Back The Falls"
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