Here's why:
* Proper Nouns: "Diplodocus" is the name of a specific genus of dinosaur. Like all genus names in biology, it is considered a proper noun.
* Scientific Naming Conventions: Scientific names for organisms follow specific rules. Genus names are always capitalized, while species names are not.
* Example: The full scientific name for a specific type of Diplodocus is "Diplodocus longus," with only the genus ("Diplodocus") capitalized.
So, when referring to the dinosaur, use "Diplodocus" with a capital "D."