Many of the animals featured in the book were criticized by paleontologists and science writers, particularly in that so many of the animals are entirely convergent with actual modern-day animals. In this capacity, the "lank", a four-legged, terrestrial and grazing pterosaur derived from the Cretaceous family Azhdarchidae, has been seen by some writers as perhaps the worst offender. In a 1990 review of the book, researcher Gregory S. Paul called the creature "perhaps the worst beast in the book" and "unbelievable", pointing out that he thought it was infeasible that pterosaurs would evolve into giraffe-like animals before the more dominant and already terrestrial dinosaurs.