Factual error: Carnotaurus and Brachiosaurus didn't exist at the same time. (Brachiosaurus 157-145 million years ago and Carnotaurus 72-69 million years ago). The show talks about taking place 85 million years ago, and Carnotaurus lived in what's now South America. Brachiosaurus lived in North America and Africa.
Factual error: The frequency which is used to attract the dragon fly is said to be "sub-sonic" and therefore can't be heard by humans, but the exact frequency is stated to be 38.2 Hz. This is well above 20 Hz, the lowest frequency an average human can hear.
Chosen answer: Because that's where the rift led. They don't have a time-travel machine, capable of taking them wherever they please - all they have is a hole in time leading to one single time period.
Tailkinker ★