22 April 2010

World's smallest T. rex is a snail!

Carl C. Christensen, our correspondent in Honolulu, e-mailed this item of utmost importance yesterday:

A recent news item claims that a South American leach, Tyrannobdella rex, is the world's smallest "T. rex," with a body length of less than two inches*. In the interest of defending the honor of the Mollusca, it should be pointed out that Cowie, Evenhuis, & Christensen's 1995 "Catalog of the Native Land and Freshwater Molluscs of the Hawaiian Islands" includes on p. 118 an entry for Tropidoptera rex (Sykes, 1904), a species of the pulmonate family Amastridae endemic to the island of Oahu, Hawaii. Hyatt & Pilsbry (1911), on p. 126-127 of vol. 21 of the second series of the Manual of Conchology, give the maximum dimension of the shell of Pterodiscus rex Sykes, 1904, as 14.5 mm. As Pterodiscus Pilsbry, 1893, is now regarded as a synonym of Tropidoptera Ancey, 1889, it appears that the Hawaiian Islands have defeated South America for the honor of being home to the world's smallest T. rex. Snails RULE!

The shell of the snail Tropidoptera rex, the world's smallest "T. rex". Drawing from the Manual of Conchology, vol. 21, plate 24.

*The original description gives the preserved body length of the holotype as 44.5 mm. See: Phillips et al. 2010. Tyrannobdella rex N. Gen. N. Sp. and the Evolutionary Origins of Mucosal Leech Infestations". PLoS ONE 5(4): e10057.

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