Dolerocypris sisaketensis, Savatenalinton, Sukonthip & Suttajit, Maitree, 2016

Savatenalinton, Sukonthip & Suttajit, Maitree, 2016, A checklist of Recent non-marine ostracods (Crustacea: Ostracoda) from Thailand, including descriptions of two new species, Zootaxa 4067 (1), pp. 1-34 : 27-28

Dolerocypris

Within the genus Dolerocypris , the taxonomic position of D. marina Hartmann, 1965 is equivocal, belonging to either Dolerocypris s.s. or Tanycypris s.s. Hartmann (1965) described this species based on specimens from Chile and placed it in the genus Dolerocypris . Subsequently, it was transferred to Tanycypris ( Broodbakker 1984) , which belongs to the subfamily Cypricercinae McKenzie, 1971 . However, this species was not included in the recent revision of Tanycypris ( Nagler et al. 2014) due to loss of type material. In his original description, Hartmann (1965) did not characterize the caudal rami attachment, and thus the presence of Triebel’s loop as a unique character of the Cypricercinae cannot be verified. On the other side, no character allowed for an unquestionable characterization as a member of the genus Dolerocypris . Its taxonomic position thus remains uncertain and we here exclude this species from our discussion on the genus Dolerocypris . Dolerocypris fasciata (O.F.Müller, 1776) presented here is the first record for Thailand, and Dolerocypris sisaketensis n. sp. described in the present contribution brings the world's total species number of the genus to six. Dolerocypris belongs to Dolerocypridinae, a monogeneric subfamily. Although this genus has thus far been recorded from many zoogeographical regions, the Palaearctic, Nearctic, Neotropical and Oriental regions ( Martens & Savatenalinton 2011, present study), it occurs in specific areas.

At present, there seems to be two lineages of Dolerocypris : the South American and the Eurasian lineages. The former comprises two species: D. opesta Brehm, 1932 and D. tenuis ( Daday, 1905) , while the latter contains four species ( D. fasciata (O.F.Müller, 1776) , D. sinensis Sars, 1903 , D. ikeyai Smith & Kamiya, 2006 , and D. sisaketensis n. sp.). Dolerocypris opesta , which was described based on material from Guatemala ( Brehm 1932), has thus far been considered endemic to the Neotropical region. Dolerocypris tenuis was described from Paraguay by Daday (1905). The occurrence of this species in the Philippines ( Tressler 1937) is comparatively doubtful as the information and illustrations on its morphology were insufficient in the publication and this hampers confirmation of the species occurrence.

In the Eurasian lineage, two species appear to be endemic, one to the Palaearctic ( D. ikeyai ) and one to the Oriental ( D. sisaketensis n. sp.) region. The former species has so far been recorded from Japan ( Smith & Kamiya 2006) and Korea (Smith et al. 2014), while the latter species is here described from Thailand. The other two species of this lineage have wide-ranging distributions: the Palaearctic, Oriental and Nearctic. Dolerocypris sinensis was considered a Palaearctic species, often reported from the Mediterranean vicinity (see overview of distribution in Meisch 2000). It has also been reported from Japan ( Okubo 1972), Korea ( Kim & Min 1991a, Smith et al. 2014), North America ( Gray et al. 2010), Macedonia, Albania ( Lorenschat et al. 2014) and Turkey ( Akdemir & Kulkoyluoglu 2014). The records of this species in the Oriental region were from the Philippines ( Victor & Fernando 1981e) and India ( Singh 1969, Harshey & Shrivastav 1983). The presence of D. sinensis in Pakistan ( Mahar & Jafri 2012) was possibly a misidentification because the shape and morphology of the valves of Pakistani specimens are not congruent with the diagnostic characters of D. sinensis (see Meisch 2000). Thus, this record is here not taken into account. Dolerocypris fasciata was found in several countries in the Palaearctic region, e.g. Norway, Sweden, Poland, Russia, China, Japan ( Meisch 2000), Korea ( Kim & Min 1991a) and Turkey ( Akdemir & Kulkoyluoglu 2014), whereas in the Oriental region it was encountered in Sumatra ( Sars 1903, Klie 1932), Kalimantan ( Victor & Fernando 1981e, k) and Thailand (present study). According to the considerable records of D. sinensis and D. fasciata from the Palaearctic and Oriental regions as mentioned above and also to the minor occurrences of these two species in the Nearctic region, it could be interpreted that these taxa originated in the Palaearctic and/or Oriental regions and subsequently were introduced to the Nearctic region. Dolerocypris sinensis was considered a native Asian species that was introduced to European countries ( McKenzie & Moroni 1986, Garcia-Berthou et al. 2007). As it was frequently found in rice fields on the Iberian peninsula ( Rossi et al. 2003, Oscoz et al. 2010), it is supposed to be an exotic species in this region, and a reasonable hypothesis is that it was transported there with agricultural plants, e.g. rice ( McKenzie & Moroni 1986, Garcia-Berthou et al. 2007).

Fossils of Dolerocypris species are known from the Palaearctic and Neotropics regions. The oldest known extinct Dolerocypris fossils are from the Late Cretaceous of Brazil ( Almeida & Carmo 2013), whereas fossils of Palaearctic Dolerocypris are more recent: Early Miocene to Holocene ( Griffiths et al. 1993, Hajek-Tadesse et al. 2009, Tunoğlu et al. 2012). Therefore, the South American lineage is older than the Palaearctic representatives, based on fossil records at present, while to date the evolution in the Eurasian lineage cannot be judged because fossils of Dolerocypris have not been reported from the Oriental region yet.