Polar Biol (2009) 32:907–914 DOI 10.1007/s00300-009-0591-8 123 ORIGINAL PAPER A new species of shallow-water sea pen (Octocorallia: Pennatulacea: Kophobelemnidae) from Antarctica Pablo J. López-González · Josep-Maria Gili · Verónica Fuentes Received: 19 November 2008 / Revised: 19 January 2009 / Accepted: 3 February 2009 / Published online: 27 February 2009  Springer-Verlag 2009 Abstract The pennatulacean genus Malacobelemnon has previously been considered to be distributed in the Western Indian and western PaciWc Oceans, with one described spe- cies and another possible undescribed species from South Africa. An undescribed shallow-water species attributable to this Kophobelemnidae genus has been collected from the Antarctic region (King George, South Shetland Islands). The present paper reports this discovery, providing the description and illustrations of the new species, Malacobe- lemnon daytoni n. sp. Some of the characters previously considered in the genus Malacobelemnon should be slightly modiWed to include the new Antarctic species. The general colony shape, the distribution of siphonozooids, number of longitudinal autozooids rows, and the length and shape of the section of axis are the main characters used to distin- guish the new species from the other in the genus M. ste- phensoni Tixier-Durivault 1965. From a bathymetric point of view, Malacobelemnon daytoni n. sp. is one of the shal- lowest pennatulacean species recorded, being an important contribution to the shallow-water Antarctic fauna. Keywords Antarctica · Sea pen · Pennatulacea · Octocorallia · Malacobelemnon · New species Introduction For many years, during regular diving surveys at Potter Cove (King George, South Shetland Islands, Antarctica) carried out by researchers from the Argentinean Polar Base of Jubany, a delicate shallow-water sea pen has been recorded and inventoried (Sahade et al. 1998, 2008). Fur- thermore, a dense population of this pennatulacean species was also illustrated in naturalist guides oriented to the gen- eral public interested in the biodiversity of Antarctic under- water environments (e.g., de la Vega 2000: 47). Thanks to the friendly collaboration between Argentinean and Spanish research groups in Antarctic matters, a set of colonies of this pennatulacean species, collected between 10 and 15 m depth during the austral summer of 2000, was placed in our hands for its taxonomic study in April 2002. The Wrst examination of these colonies identiWed the species as pre- viously unreported from Antarctic waters. A second set of colonies collected in February 2005 was available in March 2005. The goal of the present contribution is the description of these colonies. The material is considered an unde- scribed species of the kophobelemnid genus Malacobelem- non Tixier-Durivault 1965. Materials and methods The material studied here was collected by SCUBA diving in Potter Cove, just in front of the Argentinean Polar Base Jubany, on King George Island (South Shetland Islands), oV the Antarctic Peninsula (Fig. 1). Potter Cove (62°14'S, P. J. López-González (&) Biodiversidad y Ecología de Invertebrados Marinos, Departamento de Fisiología y Zoología, Facultad de Biología, Universidad de Sevilla, Reina Mercedes 6, 41012 Sevilla, Spain e-mail: pjlopez@us.es J.-M. Gili · V. Fuentes Departamento de Biología Marina y Oceanografía, Instituto de Ciencias del Mar, CMIMA (CSIC), Paseo Marítimo de la Barceloneta, 37-49, 08003 Barcelona, Spain e-mail: gili@cmima.csic.es V. Fuentes e-mail: vfuentes@cmima.csic.es