Pelagic tunicates (Appendicularia and Thaliacea) of Sri Lanka: two first records with an annotated checklist Author Karunarathne, Krishan D. 0000-0003-1780-9749 Department of Aquaculture and Fisheries, Faculty of Livestock, Fisheries and Nutrition, Wayamba University of Sri Lanka, Makandura, Gonawila, 60170, Sri Lanka. & krishankarunarathne @ gmail. com; krishan. dk @ wyb. ac. lk; https: // orcid. org / 0000 - 0003 - 1780 - 9749 krishankarunarathne@gmail.com Author Croos, M. D. S. T. De 0000-0003-4449-6573 Department of Aquaculture and Fisheries, Faculty of Livestock, Fisheries and Nutrition, Wayamba University of Sri Lanka, Makandura, Gonawila, 60170, Sri Lanka. & dileepa _ dc @ yahoo. com; dileepad @ wyb. ac. lk; https: // orcid. org / 0000 - 0003 - 4449 - 6573 dileepa_dc@yahoo.com text Zootaxa 2021 2021-11-11 5067 3 352 376 journal article 3575 10.11646/zootaxa.5067.3.2 9b8d33b9-c9df-4f9d-abeb-de1c7b84f3e0 1175-5326 5681899 AF3DF45F-B248-4BDD-904F-F55D735DC867 Key to the Appendicularia species of Sri Lanka (based on Tokioka 1960 ; Bückmann 1969 ; Fenaux 1993 , 1998; Aravena & Palma 2002 ) 1 Usually trunk flattened or spindle-shaped; endostyle curved upwards; tail orientated at the right angle to body: Family Fritillaridae............................................................................................. 11 - Trunk oval in shape and on the same axis as tail; endostyle straight: Family Oikopleuridae ........................... 2 2 Digestive tract incompletely developed; no oral glands and subchordal cells....................... Megalocercus huxleyi - Digestive tract completely developed..................................................................... 3 3 Digestive tract forms a loop broadly open to the front; oral glands and subchordal cells present......... Stegosoma magnum - Digestive tract compactly coiled into a nucleus.............................................................. 4 4 Oral glands and subchordal cells present................................................................... 8 - Oral glands and subchordal cells absent.................................................................... 5 5 Ceacum developed upwards and backwards............................................... Oikopleura fusiformis - Ceacum directed either upward or backward only............................................................ 6 6 Small ceacum directed backwards......................................................... Oikopleura gracilis - Finger-shaped ceacum directed upwards................................................................... 7 7 Ceacum close to the cardial region....................................................... Oikopleura longicauda - Ceacum separated from the cardial region by a wide bight.................................... Oikopleura intermedia 8 Numerous subchordal cells, arranged in two rows............................................. Oikopleura albicans - Subchordal cells few, arranged in a single row.............................................................. 9 9 With small postcardial ceacum on the left stomach lobe..................................... Oikopleura cophocerca - Without postcardial ceacum on the left stomach lobe........................................................ 10 10 One spindle-shaped cell................................................................ Oikopleura rufescens - Two spindle-shaped cells.................................................................. Oikopleura dioica 11 Anterior ovaries......................................................................... Tectillaria fertilis - Posterior ovaries..................................................................................... 12 12 Distal end of the tail acuminate......................................................................... 15 - Distal end of the tail notched........................................................................... 13 13 Amphichordal cells absent................................................................ Fritillaria borealis - Amphichordal cells present............................................................................ 14 14 Testis trapezoidal and laterally encircled by the ovary in a string.................................. Fritillaria venusta - Testis Y-shaped and ovary spherical........................................................ Fritillaria pellucida 15 Ciliated rings of the branchial passages oval and elongated...................................... Fritillaria fraudax - Ciliated rings of the branchial passages circular............................................................ 16 16 Trunk oval, compressed dorsoventrally...................................................... Fritillaria gracilis - Trunk elongate, bent upwards in the digestive nucleus region..................................... Fritillaria formica