Pseudoceros cf. dimidiatus (von Graff, 1893)
"Divided Flatworm" "Tiger Flatworm"
photo 1: Kona, Hawai`i. 30 ft.
photo 2: Lana`i Lookout, O`ahu. 40 ft.
photo 3: Honokohau, Hawai`i. 50 ft.

One of the two most commonly-seen flatworms in Hawai`i (the other being Pseudoceros ferrugineus). It grows to almost 3 inches and is active in the open by day. Keoki Stender gives this spectacular worm the common name Tiger Flatworm. This is better than the name I used in my book: Divided Flatworm. The reason for "divided" is that the first edition of the book classified this worm as a color variant of Pseudoceros dimidiatus, which lacks the transverse markings and is divided lengthwise by a long continuous stripe (dimidiatus means "divided"). When she published her book in 2003 Leslie Newman added the "cf" to indicate that it is a different species, as yet undescribed. I followed suit in my book, but neglected to change the common name to something more appropriate.

Newman & Cannon list this species as occurring from the Red Sea to Hawai`i, but note that there are major geographic color differences. They note that DNA studies will likely split this into several full species.

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