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
Sea urchin with just six species known from the Permian period. Only two lineages survived this period's massive extinction and into the Triassic: the genus "Miocidaris", which gave rise to modern cidaroida (pencil urchins), and the ancestor that gave rise to the euechinoids. By the upper Triassic, their numbers increased again. Cidaroids have changed very little since the Late Triassic, and are the only Paleozoic echinoid group to have survived. The euechinoids diversified into new lineages in the Jurassic and Cretaceous periods, and from them emerged the first irregular echinoids (the Atelostomata) during the early Jurassic. Some echinoids, such as "Micraster" in