Krivorotkin R.S.*, Timoshkin O.A. 2026. New and rare species of microturbellarians (Plathelminthes: Kalyptorhynchia) from Lake Baikal // Invert. Zool. Vol.23. No.2: 207–243 [in English].
Limnological Institute of the Siberian Branch of the Russian Academy of Sciences, Ulan-Batorskaya St., 3, Irkutsk 664033 Russia.
* Corresponding author
Roman Krivorotkin: roman_bio@mail.ru https://orcid.org/0000-0002-2567-6600
Oleg Timoshkin: tim@lin.irk.ru https://orcid.org/0000-0001-6476-0074
doi: 10.15298/invertzool.23.2.02
ABSTRACT: During a study of the microturbellarian fauna of the littoral zone of Lake Baikal, representatives of new and rare species were found. Illustrated descriptions of nine new species of microturbellarians (Kalyptorhynchia) are presented: Riedelella luzhanskayae sp.n., R. mirabilis sp.n., R. muriculata sp.n., Cohenella falcata sp.n., C. insolita sp.n., C. echinata sp.n., Mariareuterella lunaris sp.n., M. acutata sp.n. and Opisthocystis remotus sp.n. All the species are endemic to Lake Baikal and were found in the nearshore of the lake. Detailed and comprehensive knowledge on morphology and zoogeography of five rare and poorly studied Baikalian microturbellarians of genera Obolkinaella Timoshkin, 2004, Kawanabella Timoshkin, 2004 and Riedelella Timoshkin, 2004 is provided: Obolkinaella genkali Timoshkin, 2004, Kawanabella afanasyevae Timoshkin, 2004, Riedelella heaneyi Timoshkin, 2004, R. karabanovi Timoshkin, 2004 and R. tyleri Timoshkin, 2004. Descriptions of the specimens include new data on the morphology and variability as well as an overview of their distribution. Some rare species, previously known from isolated specimens from individual bays of Lake Baikal, turned out to be much more widespread and were found in other basins of this ancient lake. Moreover, the authors present new illustrations and descriptions of the hooks of Rhynchokarlingia zemskayae Timoshkin, 2004 holotype.
KEY WORDS: morphology, new species, endemics, Turbellaria, ancient lake, Baikal.