GEOL 104 Dinosaurs: A Natural History
Fall Semester 2006
Systematics I: Taxonomy
Taxon (pl. taxa): a named group of organisms.
Carl Linne' (Linnaeus) developed a universal set of rules in the Systema Natura ("Natural
System") in 1758; later workers added and modified the system (primarily with the addition
of new "ranks").
Some of the Linnean rules:
- All names are in Latin or Greek, or are modified into Latin form;
- Each name must be unique;
- All names are fit into a nested hierarchy (species into genera, genera into families,
and so forth);
- In traditional Linnean taxonomy, there is a set of official ranks (from smallest to
largest, species, genus, family, order, class, phylum) (later workers added additional
intermediate ranks, such as tribes, subfamilies, superfamilies, subphyla, etc.);
- The primary unit is the species (pl. species):
- Definition of a "species" varies from biologist to biologist; some definitions
("naturally occurring interbreeding populations") cannot be tested for fossils!
- Each species has a type specimen accessioned in an appropriate institution (
museum, zoological or botanical garden, or other such collection);
- Whoever describes the type specimen of a new species has the right to name that
new species (following the rules below);
- The next higher unit, the genus (pl. genera) is composed of one or more
- Definition of a "genus" is problematic as well, since it is composed of one or more
- Each genus has a type species: all other species are assigned to the
genus based on their similarity to the type species;
Linnean taxonomy has its own special set of grammatical rules:
- Genera have one word names (e.g., Panthera, Homo,
- The genus name is always Capitalized and italicized (or
underlined if you don't have access to italics);
- Species have two word names, the first part of which is the same as the
genus name (e.g., Panthera leo, Homo sapiens, Ginkgo biloba,
- The genus name is ALWAYS capitalized, the second part ("trivial nomen") is
ALWAYS in lower case, and the name is ALWAYS italicized or underlined;
- Species names can be abbreviated by using only the first letter of the genus name,
followed by a period (NEVER by a hyphen): H. sapiens and T. rex are correct;
H. Sapiens or T-Rex are WRONG!! (Subtle hint: do not
use the incorrect form on your homework or tests);
- Some taxon names for groups composed of multiple genera ("families" in the old sense)
have special formal endings, described in the Farlow & Brett-Surman textbook. We won't be
going over those details in this class;
- All taxon names other than species have one word names, which are capitalized;
all taxon names other than genera and species are in roman letters (i.e., they are
never italicized/underlined): Dinosauria, Tyrannosauridae, Animalia; not Dinosauria,
tyrannosauridae, or animalia.
Splitters: Taxonomists who consider a particular set of specimens to represent many taxa;
Lumpers: those who consider a particular set to represent few taxa.
Rule of Priority: whichever validly formed name for a species or genus was
published first, even if only by days, is the name that must be used.
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Last modified: 14 July 2006