52+, see text Diplocardia is a genus of North American (USA, Mexico) earthworms with 52-57 known species that is remarkably similar to Australian Diplotrema Spencer, 1900.

Species include Diplocardia pettiboneae (Gates 1977)[1] and Diplocardia longa (Moore 1904), with bioluminescent mucus.

The second largest earthworm in North America is Diplocardia meansi (Gates 1977) and is endemic to Rich Mountain in the Ouachita Mountains.

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