The Magic School Bus In the Time of the Dinosaurs to after he fought the T-Rex; which made Arnold leave the sneaker footprint from his shoe due to his giant size). When Ms. Frizzle says she wonders what giant creature left that footprint, this is what Carlos says in response. Carlos says "I'd say it was a 'Sneakersaurus'!". Ms. Frizzle is missing some photographs from her photo album of her last trip to the age of dinosaurs. As usual, the user has to find replacements. There are seven different places, including "Triassic Arizona", "Triassic Argentina", "Jurassic Colorado", "Jurassic Tethys Sea", "Jurassic Tanzania", "Cretaceous Alberta", and "Cretaceous Mongolia". Here in the
Cretaceous local subdivisions are still in use. As with other older geologic periods, the rock beds of the Cretaceous are well identified but the exact age of the system's base is uncertain by a few million years. No great extinction or burst of diversity separates the Cretaceous from the Jurassic. However, the top of the system is sharply defined, being placed at an iridium-rich layer found worldwide that is believed to be associated with the Chicxulub impact crater, with its boundaries circumscribing parts of the Yucatán Peninsula and into the Gulf of Mexico. This layer has been dated at 66.043 Ma.