Okay here are some Dinosaurs with names that start with the letter a.
List: Ankylosaurus, Acanthopholis, Acrocanthosaurus, Albertosaurus, Allosaurus, Abelisaurus, Achelousaurus, Actiosaurus, Adasaurus, Aegyptosaurus, Aeolosaurus, Aepisaurus, Afrovenator, Agathaumas, Agilisaurus, Agrosaurus, Alamosaurus, Alectrosaurus, Alioramus, Algosaurus, Aliwalia, Alocodon, Altirhinus, Altispinax, Alvarezsaurus, Apatosaurus, Alwalkeria, Alxasaurus, Amargasaurus, Ammosaurus, Ampelosaurus, Amphicoelias, Amtosaurus, Amphisaurus, Amygdalodon, Amurosaurus, Anchisaurus, Anatosaurus, Anatotitan, Anchisauripus, Anchiceratops, Andesaurus, Angaturama, Anodontosaurus, Anomoepus, Anoplosaurus, Anserimimus, Antarctosaurus, Apatodon, Aragosaurus, Aralosaurus, игрушка Araucanoraptor, Archaeoceratops, Archaeoraptor, Archaeornithoides, Archaeornithomimus, Archillobator, Argentinosaurus, Arctosaurus, Arkansaurus, Argyrosaurus, Arrhinoceratops, Arstanosaurus, Asiaceratops, Asiatosaurus, Atlascoposaurus, Atlantosaurus, Astrodon, Atreipus, Aublysodon, Austrosaurus, Avaceratops, Avimimus, Avipes, and Azendosaurus.