The Latin-derived scientific names are capitalized except for the specific and subspecific names. The generic, specific, and subspecific names are underlined or italicized.
The names of the following are capitalized: kingdom, phylum, subphylum, class, subclass, superorder, order, suborder, superfamily, family, subfamily, tribe, genus, subgenus.
The names of the following are not capitalized: superspecies, species, subspecies.
Names of superspecies, species, and subspecies always appear with the name of the genus (or at least the genus abbreviated) so that the full specific name begins with a capital letter.
The full specific name, genus plus species (and superspecies and subspecies, if used), is italicized or underlined.
Examples: Birds are in the class Aves, subphylum Vertebrata, and phylum Chordata.
The American Robin is in the family Turdidae, superfamily Muscicapidae, suborder Oscines, and order Passeriformes.
The American Robin is Turdus migratorius.
The Dark-Backed Robin, a northern-nesting subspecies, is known as T. m. nigrideus.
(Note the use of capitalization and italics.)
The genus or species name is abbreviated only when the name has already been used, and it is clear what the letters stand for. The last word in a species name is never abbreviated. So if we were to once again refer to the Robin species, we could write Turdus migratorius or T. migratorius but never simply T.m. unless it were followed by a subspecific name as was done above.