Pycnogonida (Arthropoda) from Uruguayan waters (Southwest Atlantic): annotated checklist and biogeographic considerations Author Scarabino, Fabrizio Author Lucena, Rudá Amorim Author Munilla, Tomás Author Soler-Membrives, Anna Author Ortega, Leonardo Author Schwindt, Evangelina Author López, Guzmán Author María, José Author Christoffersen, Martin Lidsey text Zootaxa 2019 2019-01-24 4550 2 185 200 journal article 27492 10.11646/zootaxa.4550.2.2 2c967830-701d-424c-a044-d61885a8c2c5 1175-5326 2625249 AB41359C-FDBB-483C-B538-BD8D51F42FA2 Genus Pallenopsis Wilson, 1881 Remarks : This genus has a long and complex taxonomic history in the southwest Atlantic, summarized by Stock (1973 , 1975 ). Weis et al . (2014) analysed the existence of a species-complex within the traditional concept of Pallenopsis patagonica ( Hoek, 1881 ) . In fact, they referred it as “one of the most taxonomically problematic and variable pycnogonid species known to date”. Böhm (1879) recorded Pallenopsis fluminensis (Kroyer, 1844) (as Phoxichilidium fluminensis ) from the Magellan Strait and Patagonia ( 54.9–76.8 m depth) based on material collected by the RV Gazelle in 1876, deposited in the Museum für Naturkunde der Humboldt-Universität zu Berlin. In the zoological report of the Gazelle expedition, Studer (1889) recorded that species (as Pallene fluminensis ) from three stations, adding a third and deeper ( 80.5 m ) record from the Uruguayan shelf. Schimkewitsch (1930) considered that Böhm’s specimens represent a new species: Pallenopsis boehmi . Stock (1973) redescribed this species, re-examining the material identified by Böhm as P. fluminensis (four specimens collected by the Gazelle ), but considered that one specimen belongs to P. patagonica . Stock (1973) nominated a female specimen from the Magellan Strait as the Lectotype of P. boehmi . Due to insufficient labelling, it was not possible to establish which locality the specimen of P. patagonica belongs; either it was station LVII, 38°10.1´S– 56°26. 6´W, 54.9 m depth, off Buenos Aires Province , Argentina , or it belongs to station LX, 34°43.7´S– 52°36.1´W , 80.5 m depth, Uruguayan shelf ( Stock 1973 ; Dunlop et al . 2007 ). Therefore, the records of Studer (1889) for both localities remain uncertain. According to Stock (1973 , 1992 ), P. boehmi has a geographical distribution extending from the Strait of Magellan to southeast Brazil ( ca. 23°10´S ). This distribution is biogeographically anomalous for a shelf species. Pallenopsis tumidula Loman, 1923 was recorded from the RV Calypso 1961 –1962 cruise station 172 off Buenos Aires Province , Argentina by Stock (1966) . Another specimen, from an unknown location due to mixing of materials, was collected at one of the following stations of the same expedition: 160, 161 (both in Uruguayan waters), 171 or 173 (off Buenos Aires Province , Argentina ) ( Stock 1966 ). Stock (1992) also reported this species for southeast and south Brazil ( 23°15´S– 30°20´S ); therefore, the Uruguayan shelf is within its geographic range, although there are no reliable records. Station 2 of the 1901–1903 Swedish Antarctic Expedition (off Buenos Aires Province , Argentina , 37°30´S– 56°11´W , 100 m ) is the type locality of P. tumidula ( Loman 1923 ) . Hedgpeth (1943) recorded, for the first time, P. fluminensis for Argentinean waters, off Buenos Aires Province ( 37°42'S– 56°20'W , 80.4 m depth, station 26 of Hassler Expedition). Later, Bremec et al . (1986) briefly described and illustrated one specimen of Pallenopsis collected in the littoral zone of the Buenos Aires Province ( 38°45´S ), identifying it as P. fluminensis . This species is otherwise known from the Brazilian coast ( Lucena et al. 2017 ).