ZOOSYSTEMATICA ROSSICA, 20(1): 161–173 28 JULY 2011 Three new species, two new genera, and new family Biphragmosagittidae (Сhaetognatha) from Southwest Pacific Ocean Три новых вида, два новых рода и новое семейство Biphragmosagittidae (Сhaetognatha) из юго-восточной части Тихого океана A.P. KASSATKINA А.П. КАСАТКИНА A.P. Kassatkina, Pacific Institute of Oceanography, Far East Division, Russian Academy of Sciences, 43 Baltiyskaya St., Vladivostok 690041, Russia. E-mail: [email protected] Resuming published and own data, a revision of classification of Chaetognatha is presented. The family Sagittidae Claus & Grobben, 1905 is given a rank of subclass, Sagittiones, charac- terised, in particular, by the presence of two pairs of sac-like gelatinous structures or two pairs of fins. Besides the order Aphragmophora Tokioka, 1965, it contains the new order Biphrag- mosagittiformes ord. nov., which is a unique group of Chaetognatha with an unusual combi- nation of morphological characters: the transverse muscles present in both the trunk and the tail sections of the body; the seminal vesicles simple, without internal complex compartments; the presence of two pairs of lateral fins. The only family assigned to the new order, Biphragmo- sagittidae fam. nov., contains two genera. Diagnoses of the two new genera, Biphragmosagitta gen. nov. (type species B. tarasovi sp. nov. and B. angusticephala sp. nov.) and Biphragmofas- tigata gen. nov. (type species B. fastigata sp. nov.), detailed descriptions and pictures of the three new species are presented. На основе литературных и собственных данных проведена ревизия типа Chaetognatha. Ранг семейства Sagittidae повышен до подкласса, Sagittiones, который охарактеризо- ван, в частности, наличием двух пар мешковидных желеобразных структур или двух пар плавников. Помимо отряда Aphragmophora Tokioka, 1965, этот подкласс содержит новый отряд Biphragmosagittiformes ord. nov., который является уникальной группой Chaetognatha с необычным сочетанием морфологических признаков: 1) поперечная му- скулатура имеется в полости туловищного и хвостового отделов, простые семенные ме- шочки без внутренних сложных камер; 2) две пары боковых плавников. Единственное семейство нового отряда, Biphragmosagittidae fam. nov., содержит два новых рода. При- ведены их диагнозы, а также диагнозы включенных видов – Biphragmosagitta gen. nov. (типовой вид B. tarasovi sp. nov. и B. angusticephala sp. nov.) и Biphragmofastigata gen. nov. (типовой вид B. fastigata sp. nov.) с детальными описаниями и изображениями. Key words: classification, Сhaetognatha, Eukrohniones, Sagittiones, Biphragmosagittiformes, Biphragmosagittidae, new subclasses, new order, new family, new genera, new species Ключевые слова: классификация, Сhaetognatha, Eukrohniones, Sagittiones, Biphragmo- sagittiformes, Biphragmosagittidae, новые подклассы, новый отряд, новое семейство, но- вые роды, новые виды © 2011 Zoological Institute, Russian Academy of Scienсes 162 A.P. KASSATKINA. NEW CHAETOGNATH FAMILY, GENERA AND SPECIES FROM PACIFIC OCEAN INTRODUCTION tive organs. Based on these descriptions he subdivided the phylum Chaetognatha, the While the phylogenetic position of class Sagittoidea, into two subclasses – Syn- Chaetognatha has became central to the gonata (with the ducts connecting the ova- question of early bilaterian evolution, the ries in the trunk section of the body and the internal systematics of the phylum are still testes in the tail section) and Chorismogo- not clear (Papillon et al., 2006). The history nata (with no ducts connecting the genitals of taxonomy of Chaetognatha was reviewed present). The Syngonata thus included only in details in some in early publications (e.g. a single order Biphragmophora Casanova, á Ritter-Z hony, 1911; Kuhl, 1938; Hyman, 1985 with a single family Heterokrohniidae 1959; Beauchamp, 1960). Tokioka (1965a, Casanova, 1985, and the Chorismogonata – 1965b) revised the classification based two orders, Monophragmophora Casanova, on the data on presence/absence of the 1985 (with families Spadellidae Tokioka, transverse coelomic muscles (the so-called 1965 and Eukrohniidae Tokioka, 1965) phragmes, or phragma). He considered that, and Aphragmophora Tokioka, 1965 (with from a morphological point of view, the most families Sagittidae Claus & Grobben, 1905, fundamental character was the presence or Pterosagittidae Tokioka, 1965, Krohnittidae absence of the phragmes, and thus defined Tokioka, 1965). However, the morphological the established orders, Phragmophora and data presented by Casanova (1985) were not Aphragmophora. Since then, Chaetognatha well supported by illustrative materials, and, has been typically divided into two orders, in some case, contradict to earlier known Phragmorphora and Aphragmorphora, each data on gonadal structure (e.g. Elpat’evskiy, comprising three families (Pierrot-Bults, 1910, 1913, 1914) and some new discoveries 2004). However Tokioka (1965a, 1965b) Kassatkina & Stolyarova, 2008). did not take into consideration morpho- Molecular data showed (Papillon et al., logical features of Krohnittella Germain & 2004, 2006) that there are three main mono- Joubin, 1912, a rare genus that does not phyletic groups: Sagittidae/Krohnittidae, have a transverse musculature but, by most Spadellidae/Pterosagittidae, and Eukroh- other characters, displays a clear similarity niidae/Heterokrohniidae. In this scheme, to Heterokrohnia Ritter-Záhony, 1911. This the group of Aphragmophora without is why, later, Bieri (1974) did not accept the Pterosagittidae (Sagittidae/Krohnittidae) Tokioka’s scheme (Tokioka, 1965a, 1965b) is monophyletic, the Spadellidae/Pterosag- with the two orders, Phragmorphora and ittidae and Eukrohniidae/Heterokrohni- Aphragmorphora. Dallot and Ibanez (1972) idae families are very likely clustered, the analysed 32 characters and received dif- Krohnittidae and Pterosagittidae groups ferent conclusions on taxonomic relation- should no longer be considered as families ships within the phylum: the order Aphrag- as they are included in other groups desig- mophora Tokioka, 1965 contained a single nated as families, and the Syngonata/Cho- family, Sagittidae, with two pairs of fins rismogonata and the Monophragmophora/ while genera with one pair of lateral fins, Biphragmophora hypotheses were thus Pterosagitta Costa, 1869 and Krohnitta Rit- rejected. More recent data (Jennings et al. ter-Záhony, 1910, that had been given rank 2010) also support the main divergence be- of families of their own by Tokioka (1965a) tween the Eukrohniidae+Heterokrohniidae were excluded. and Spadellidae s.l. further supporting the Casanova (1985, 1986) published on main scheme of Tokioka (1965a, 1965b) findings of new genera and species Archet- based on the transverse muscles presence/ erokrohnia rubra Casanova, 1986 and a new absence data. species Heterokrohnia murina Casanova, Salvini-Plawen (1986) gave reasons to 1986 with a description of their reproduc- consider Spadellidae as quite specialised © 2011 Zoological Institute, Russian Academy of Scienсes, Zoosystematica Rossica 20(1): 161–173 A.P. KASSATKINA. NEW CHAETOGNATH FAMILY, GENERA AND SPECIES FROM PACIFIC OCEAN 163 coastal chaetognaths rather than a group Yunnan, China (Eognathacantha ercainella ancestral for all other Chaetognatha. Tel- Chen & Huang, 2002 and Protosagitta spi- ford and Holland (1997) confirmed a dis- nosa Hu, 2005) and the Middle Cambrian tinct position of Spadella from all groups Burgess Shale of British Columbia (Oe- of Chaetognatha based on molecular data. sia disjuncta Walcott, 1911) (Szaniawski, Salvini-Plawen (1986) established three 2005; Vannier et al., 2007). A more recent species groups and proposed two new gen- chaetognath, Paucijaculum samamithion era based on the number of pairs of fins and Schram, 1973 has been described from the the locations and presence/absence of the Mazon Creek biota from the Pennsylva- digitate adhesive organs. While Bowman & nian of Illinois (Schram, 1973). As it can be Bieri (1989) agreed that the presence of ad- seen from the published pictures (e.g. that hesive organs is taxonomically important, of Protosagitta spinosa in Vannier et al., they questioned the importance of the num- 2007: fig. 1a), the chaetognaths from the ber of lateral fin pairs. They point out that Cambrian possessed the transverse muscles immature individuals of Paraspadella have (phragmes). only a single pair of fins, but, with sexual de- In general, the chaetognath locomotory velopment, the fins become separated into muscles exhibit astonishing variations. As anterior and posterior parts by the lateral described by Casanova and Duvert (2002), growth of the vagina. the transverse muscle, present in the less The Von Salvini-Plawen’s (1986) opin- evolved genera living near or on the bottom, ion on the ancestral state of the absence of has two forms: either classical cross-striated the phragmes was not confirmed by palae- or, in more or less benthic species, supercon- ontological data. There was published a de- tracting. Supercontraction is supposed to scription of the genus Parmia Gnilovskaya, be a derived character. The peculiarities of 1998 from southern Timan, northeast of the primary, secondary and transverse mus- the Russian Platform, – worm-like crea- cles of the truly benthic chaetognaths are tures inhabiting the ocean during the Late different from those of all the planktonic or Riphean of an approximate age of about 1 benthoplanktonic chaetognaths. These data Ga (Gnilovskaya et al., 2000, cited by Fe- confirm well the importance of