Megalosaurus
Pride of place must go to Megalosaurus bucklandi "Buckland’s big reptile" - because it proved to be the earliest discovered and scientifically described dinosaur.
Its remains, though incomplete, began to be collected from quarries at the village of Stonesfield in Oxfordshire in about 1815. The bones, teeth, and jaws were passed to Oxford University Museum, where they still reside, and were studied by the greatest living anatomist of the time Georges Cuvier, who visited Oxford (and its custodian William Buckland) from Paris to see the material.