This was a series of audio adventures we listened to in elementary school somewhen between 20 and 25 years ago, but I'm pretty sure they were quite a bit older than that. I think they may have been accompanied by filmstrips or slideshows or something like that, but my memory is hazy.
Anyway, there were two kids who (I think) were wandering through a museum and somehow actually ended up going back into the past, where they met all kinds of (intelligent, talking) dinosaurs. There were several installments in the series and each focused on a different dinosaur. IIRC, it ended on a cliffhanger; they ran into a Tyrannosaurus rex that said it could show them the way back home, but they didn't know if they could trust it, since it was, y'know, a damn T. rex that might just be trying to earn their trust and eat them. I think the series ended with them trying to decide if they should believe it or not.
Does this ring any bells? Thanks in advance.