Here's a list of the Dinosaurs from the Monster Manual: (exactly as listed)

Well, I don't know exactly for all of these (can probably be checked with some effort in Wikipedia or elsewhere), but I can add the general intervals Triassic (ca. 250 to 200 MA), Jurassic (ca. 200 to 145 MA), and Cretaceous (ca. 145 to 65 MA) quickly, plus upper/younger and lower/older in some cases:
Apatosaurus (Trachodon): That's strange, since 'Trachodon' is the old name for 'Anatosaurus', an ornithopode (Upper Cretaceous), while 'Apatosaurus' is the correct name for 'Brontosaurus' (Upper Jurassic)
Ankylosaurus: Upper Cretaceous
Antrodemus (Allosaurus): Upper Jurassic
Apatosaurus (Brontosaurus): (Upper Jurassic) So, above it is probably Anatosaurus.
Archelon: Giant Turtle from Upper Cretaceous
Ischyros: Ah! Wikipedia says it is an Archelon species - I did not know that...

Brachiosaurus: Upper Jurassic
Camarosaurus: Upper Jurassic
Ceratosaurus: Upper Jurassic
Cetiosaurus: Jurassic
Dinichtys: Probably Dunkleosteus (Dinichthys), Giant armoured fish, Upper Devonian, ca. 370 MA
Diplodocus: Upper Jurassic
Elasmosaurus: Upper Cretaceous
Gorgosaurus: Upper Cretaceous
Iguanadon: Cretaceous
Lambeosaurus: Upper Cretaceous
Megalosaurus: May be a mixture of several carnivorous dinosaurs from the Jurassic
Monoclonius: Upper Cretaceous
Mosasaurus: Upper Cretaceous (a varan/lizard)
Paleoscincus: Upper Cretaceous (Palaeoscincus)
Pentaceratops: Upper Cretaceous
Plateosaurus: Upper Triassic (The 'Swabian Wyvern'

)
Plesiosaurus: Jurassic
Pteranodon: Upper Cretaceous
Stegosaurus: Upper Jurassic
Styracosaurus: Upper Cretaceous
Teratosaurus: Upper Triassic (not a dinosaur, but similar)
Triceratops: Upper Cretaceous
Tyrannosaurus Rex: Upper Cretaceous
from Monster Manual II:
Ankisaurus: probably Anchisaurus from the Lower Jurassic
Camptosaurus: Upper Jurassic
Compsognathus: Upper Jurassic
Dacentrurus: Upper Jurassic
Deinonychus:

Lower Cretaceous
Dilophosaurus: Lower Jurassic
Dimetrodon: Pelycosaur from the Permian, 270 MA
Euparkeria: Triassic
Kentrosaurus: Jurassic
Mamenchisaurus: Jurassic
Massopondylus: Lower Jurassic
Nothosaurus: Triassic
Ornitholestes: Hmm...Lower Jurassic? Well, Wikipedia says Upper Jurassic

Phororhacos: probably Phorusracos, Miocene, 10 MA (see above)
Podokesaurus: Lower Jurassic
Pterosaur, Giant: Well, that can be anything. Pteranodon, Quetzalcoatlus, but all the big species come from the Upper Cretaceous, I think.
Struthiomimus: Upper (?) Cretaceous
Tanystropheus: Triassic
Tennodontosaurus: Temnodontosaurus is an ichthyosaur from the Lower Jurassic, Tenontosaurus is an ornithopode from the Lower Cretacous...