Taxonomy and Distribution
Within the world of taxonomy the stable 'Classical System' of Michaelsen (1900) and Stephenson (1930) was gradually eroded with considerable controversy over how to classify earthworms such that Fender and McKey-Fender (1990) went so far as to say "The family-level classification of the megascolecid earthworms is in chaos." Over the years, many scientists developed their own classification systems for earthworms, which led to confusion, and these systems have been and still continue to be revised and updated. The classification system used here, developed by Blakemore (2000), is a modern reversion back to the Classical System that is historically proven and widely accepted.
Categorization of a megadrile earthworm into one of its taxonomic families under suborders Lumbricina and Moniligastrida is based on such features as the makeup of the clitellum, the location and disposition of the sex features (pores, prostatic glands, etc.), number of gizzards and body shape. There are currently over 6,000 named species of terrestrial earthworms, as provided in an species name database, but the number of synonyms is unknown.
The families, with their known distributions or origins:
- Acanthodrilidae - (Gondwanan or Pangaean?)
- Ailoscolecidae - Pyrenees and southeast USA
- Almidae - Tropical equatorial (South America, Africa, Indo-Asia)
- Benhamiinae - Ethiopian, Neotropical (a possible sub-family of Octochaetidae)
- Criodrilidae - Southwestern Palaearctic: Europe, Middle East, Russia and Siberia to Pacific coast; Japan (Biwadrilus); mainly aquatic
- Diplocardiinae/-idae - Gondwanan or Laurasian? (a sub-family of Acanthodrilidae)
- Eudrilidae - Tropical Africa south of the Sahara
- Exxidae - Neotropical: Central America and Caribbean
- Glossoscolecidae - Neotropical: Central, S. America, Caribbean
- Hormogastridae - Mediterranean
- Kynotidae - Malagasian: Madagascar
- Lumbricidae - Holarctic: North America, Europe, Middle East, Central Asia to Japan
- Lutodrilidae - Louisiana southeast USA
- Megascolecidae - (Pangaean?)
- Microchaetidae - Terrestrial in Africa especially South African grasslands
- Moniligastridae - Oriental and Indian sub-region
- Ocnerodrilidae - Neo-Tropics, Africa; India
- Octochaetidae - Australasian, Indian, Oriental, Ethiopian, Neotropical
- Octochaetinae - Australasian, Indian, Oriental (sub-family if Benhamiinae is accepted)
- Sparganophilidae - Nearctic, Neotropical: North and Central America
- Tumakidae - Columbia, South America
Read more about this topic: Earthworm
Famous quotes containing the word distribution:
“The man who pretends that the distribution of income in this country reflects the distribution of ability or character is an ignoramus. The man who says that it could by any possible political device be made to do so is an unpractical visionary. But the man who says that it ought to do so is something worse than an ignoramous and more disastrous than a visionary: he is, in the profoundest Scriptural sense of the word, a fool.”
—George Bernard Shaw (1856–1950)