Arctic species of the cheilostome bryozoan Microporella, with a redescription of the type species Piotr Kuklinski a,b * and Paul D. Taylor b a Institute of Oceanology, Polish Academy of Sciences, Warszaw, Poland; b Natural History Museum, London, UK (Received 12 February 2008; final version received 6 March 2008) This investigation focuses on the diversity and taxonomy of species of Microporella found north of the Arctic Circle. Firstly, however, a neotype is chosen for the Mediterranean type species M. ciliata (Pallas) in order to stabilize the taxonomy of this ‘‘pseudocosmopolitan’’ species, which has been recorded in the past from the Arctic. Study of type and other material using scanning electron microscopy shows that only two Arctic species of Microporella can be recognized, M. arctica Norman and M. klugei sp. nov. The first of these is characterized by a large ascopore divided by thin radial septa and situated close to the proximal rim of the orifice. Microporella klugei sp. nov. differs in having a smaller, undivided ascopore situated in a more proximal position on the frontal shield. Both Arctic species are notable among Microporella species for having a high proportion of autozooids without associated avicularia. Keywords: Arctic; Bryozoa; Microporella; taxonomy; new species Introduction The ascophoran cheilostome bryozoan Microporella (Hincks 1877) is distributed in marine environments across all climatic zones. Over 100 species have been validly assigned to Microporella, most living, but some fossil (Taylor and Mawatari 2005). Although recognition of the genus of Microporella is relatively straightforward, identification at the species level can be problematic. This is mostly due to the fact that differences in skeletal morphology between species are very subtle and can be difficult to detect using an optical microscope. As with other cheilostomes, introduction of scanning electron microscopy (SEM) to taxonomic studies has greatly improved our knowledge of species richness in Microporella, resulting in a steady increase in the number of species that can be distinguished (e.g., Dick et al. 2005; Taylor and Mawatari 2005; Tilbrook 2006; Florence et al. 2007). The type species of Microporella, Eschara ciliata, was described in 1766 by the German naturalist Peter Simon Pallas (1741–1811) from an unspecified location in the Mediterranean Sea. Unfortunately, no type material of M. ciliata is known to exist and Pallas’s original description, which is unillustrated, fails to provide adequate morphological details by present standards to allow the species to be recognized. Since its first description M. ciliata has been recorded from a multitude of localities around the globe (Taylor and Mawatari 2005), including the Antarctic, Pacific and Indian Oceans, South and North Atlantic, Red Sea, and Arctic (e.g., *Corresponding author. Email: kuki@iopan.gda.pl Journal of Natural History Vol. 42, Nos. 27–28, July 2008, 1893–1906 ISSN 0022-2933 print/ISSN 1464-5262 online # 2008 Taylor & Francis DOI: 10.1080/00222930802126904 http://www.informaworld.com Downloaded By: [Natural History Museum] At: 19:34 15 September 2008