Researcher may study dinosaurs from a cretaceous period.Logical formLearned from1 sentences. Amber can be from a cretaceous period.Logical formLearned from1 sentences. (Killing machines) can be cretaceous.Logical formLearned from1 sentences. A (period adventure) can be cretaceous.Logical formLearned from1 sentences. Rocks may date from a cretaceous period.Logical formLearned from1 sentences. Species may swim in seas of a cretaceous period.Logical formLearned from1 sentences. Pterosaurs may pertain-to a cretaceous period.Logical formLearned from1 sentences. A genus of pterosaurs of a cretaceous period can be pteranodon.Logical formLearned from1 sentences. Pterosaurs may pertain-to a cretaceous period.Logical formLearned from1 sentences. (Animal life) can be in a cretaceous period.Logical formLearned from1 sentences. Dinosaurs may disappear at an end of a cretaceous period.Logical formLearned from1 sentences. Placentals may originated in a late cretaceous period.Logical formLearned from1 sentences. Part may be marked by overthrust of cretaceous limestones.Logical formLearned from1 sentences. Triceratops can be cretaceous.Logical formLearned from1 sentences. Evidence can be from a late cretaceous period.Logical formLearned from1 sentences.