New contributions to the taxonomy of urostylid ciliates (Ciliophora, Hypotrichia), with establishment of a new genus and new species.

Hypotrichia, one of the most complex and highly differentiated groups in Ciliophora, has been the object of extensive studies, especially in recent years. Nevertheless, methodological difficulties and insufficient faunistic studies have limited our understanding of their biodiversity and phylogeny. In this study, one novel urostylid ciliate, Pseudoholosticha zhaoi nov. gen., nov. spec. and two populations of Anteholosticha monilata (Kahl, 1928) Berger, 2003, type species of the latter genus, are studied using an integrative approach (live observation, protargol impregnation, scanning electron microscopy, and phylogenetic analysis) to provide further insights into the diversity, classification, and phylogeny of this group of ciliates. Pseudoholosticha nov. gen. can be separated from other morphologically similar genera mainly by the absence of buccal and caudal cirri. A key to 12 morphologically similar genera and illustrations of their cirral patterns are provided. The validation of the new genus and new species is supported by both morphological and phylogenetic analyses. The first 18S rRNA gene sequence of A. monilata, with detailed morphological data, provided a reliable clarification of A. monilata populations and corroborated the phylogenetic position of the type species of the polyphyletic genus Anteholosticha.

Molecular phylogeny of a new gonostomatid ciliate revealing a discrepancy between interphasic and cell divisional patterns (Ciliophora, Hypotricha).

The morphology, ontogenesis, and molecular phylogeny of a new ciliate, Gonostomum koreanum n. sp., discovered in a terrestrial moss sample from South Korea, were investigated. Morphologically, it is characterized by a gonostomatid oral apparatus, two macronuclear nodules, six frontoventral rows, the two rightmost of which (frontoventral rows V and VI) extend posteriorly to near pretransverse and transverse cirri, and three dorsal kineties each with a single caudal cirrus posteriorly. The new species is easily confused with members of the genus Metagonostomum because of the long frontoterminal cirral row but differs mainly in the de novo (vs. intrakinetal) origin of anlage VI, a character found only in Gonostomum and Paragonostomum. To solve the discrepancy between the interphasic and ontogenetic patterns, we additionally performed morphological and multigene analyses on three gonostomatid species, namely Gonostomum koreanum n. sp. and its morphologically (M. gonostomoida) and ontogenetically (G. kuehnelti) most similar species. The multigene analyses show that the new species is closely related to G. kuehnelti and the core gonostomatids consists of five groups based on the origin of the frontoventral rows.

Morphology, ontogenesis and molecular phylogeny of a new saline soil ciliate, Uroleptoides salina nov. spec. (Ciliophora, Hypotrichia).

The morphology, morphogenesis and molecular phylogeny of a new saline soil hypotrich ciliate, Uroleptoides salina nov. spec., discovered from China, was investigated. The new species is characterized as follows: body 150-215 × 40-50 µm in vivo, slender and highly flexible; usually four ellipsoidal macronuclear nodules; contractile vacuole absent; cortical granules absent; endosymbiotic algae present; amphisiellid median cirral row consists of 14-25 cirri and terminates about 47% down length of body; usually three buccal cirri and 3-13 cirri left of anterior portion of amphisiellid median cirral row; 3-5 transverse cirri. Morphogenesis during binary fission is characterized by: (1) the parental adoral zone of membranelles is retained completely, parental paroral contributes to the formation of the undulating membranes anlage for the proter; (2) the oral primordium of the opisthe is formed apokinetally; and (3) the amphisiellid median cirral row is formed from two anlagen. Phylogenetic analyses based on SSU rDNA sequence data show that Uroleptoides salina nov. spec. has a close relationship with its morphologically similar species, U. longiseries, U. magnigranulosus, Orthamphisiella breviseries, and Parabistichella variabilis.

Morphology, Morphogenesis and Phylogenetic Position of the Soil Hypotrichous Ciliate, Parabistichella dieckmanni (Foissner, 1998) Foissner, 2016 (Ciliophora, Hypotrichia), with Notes on the Phylogeny of Parabistichella.

The morphology, morphogenesis and molecular phylogeny of Parabistichella dieckmanni (Foissner, 1998) Foissner, 2016, isolated from north China, were investigated. The Chinese population was characterized as having five to seven frontal cirri in corona, four to seven buccal cirri arranged in a row, two to four short frontal rows and two long frontoventral rows, three to seven transverse cirri, four macronuclear nodules, three dorsal kineties following a Gonostomum-pattern, and caudal cirri absent. Morphogenetic research reveals that the main characteristics during binary fission are as follows: (1) the long left frontoventral row is formed by two or three anlagen; (2) the posterior part of the parental adoral zone of membranelles is renewed, and the oral primordium of the opisthe is formed intrakinetally; (3) FVT-anlagen I to VI (or V, VII) produce each a frontal cirrus to form the frontal corona; (4) development of dorsal kineties follows the Gonostomum-pattern. Phylogenetic analyses showed that P. dieckmanni does not group with other Parabistichella species. Therefore, the genus Parabistichella is polyphyletic. Additionally, Parabistichella variabilis n. comb. (basionym: Bistichella variabilis He & Xu, 2011) and Parabistichella cheni n. nom. (basionym: Parabistichella variabilis Jiang et al., 2013) were suggested.

Morphology and molecular phylogeny of two new soil ciliates, Hemiurosomoida warreni nov. spec. and Hemiurosoma clampi nov. spec. (Ciliophora, Hypotrichia) from Tibet.

Two novel hypotrichous ciliates, Hemiurosomoida warreni nov. spec. and Hemiurosoma clampi nov. spec., isolated from soil in the Lhalu Wetland and Motuo Virgin Forest in Tibet, respectively, were investigated using live observation and protargol staining. Hemiurosomoida warreni nov. spec. strongly resembles the type species H. longa but can be distinguished by its body size in vivo (110-145 × 30-40 µm vs. 50-100 × 18-40 µm), number of adoral membranelles (25-38 vs. 15-22), and numbers of right (29-39 vs. 14-23) and left (26-35 vs. 13-23) marginal cirri, transverse cirri (3 vs. 4 or 5) and macronuclear nodules (4-8 vs. 2). Hemiurosoma clampi nov. spec. is characterized by its vermiform body shape, colourless cortical granules distributed in irregular rows, two macronuclear nodules, three frontal cirri, one buccal cirrus, four frontoventral cirri ranged in a line, two transverse cirri, lacking postoral ventral and pretransverse ventral cirri, and marginal rows that are not posteriorly confluent. Phylogenetic analyses based on SSU rDNA gene sequences suggest that Hemiurosomoida is not monophyletic. A close relationship is revealed between Hemiurosomoida warreni nov. spec., Parakahilella macrostoma, Hemiurosoma clampi nov. spec., and the type species Hemiurosoma terricola. As expected, all these species are classified within the "non-oxytrichid Dorsomarginalia".

Morphology and ontogenesis of two new Hemiholosticha species (Ciliophora, Hypotrichia, Hemiholostichidae nov. fam.).

The morphology and ontogenesis of two new hypotrich ciliates, Hemiholosticha solitaria and Hemiholosticha germanica, were studied using live observation, protargol impregnation, and scanning electron microscopy. Both species share a medium-sized, almost globular body with a short anterior projection; two macronuclear nodules with a single micronucleus in between; a central contractile vacuole; three or four ventral, one postoral, one right and one left marginal cirral row; and three dorsal kineties extending along ribs. However, H. germanica is distinguished from congeners by a higher number of cirri in ventral rows R1 and R2 (3-6 vs. 2 cirri in each row). Hemiholosticha solitaria differs from congeners by having four (vs. three) ventral cirral rows and by the lack (vs. presence) of intracellular green algae. The ontogenesis of H. solitaria follows the H. pantanalensis mode in that (i) the oral primordium develops in a deep pouch and generates the first two cirral streaks in addition to adoral membranelles and undulating membranes, (ii) the undulating membrane anlage does not produce any cirri, and (iii) the longitudinal ventral cirral row R3 originates from two anlagen. The ontogenetic peculiarities along with the 18S rRNA gene phylogenies suggest classification of Hemiholosticha, Psilotrichides, and Urospinula into a new family, Hemiholostichidae.

Morphology, morphogenesis and molecular phylogeny of a novel soil ciliate, Afrokahliella paramacrostoma n. sp. (Ciliophora, Hypotrichia).

A soil hypotrich ciliate, Afrokahliella paramacrostoma n. sp., was discovered in China. Its morphology, morphogenesis and molecular phylogeny were investigated using standard methods. The new species is characterized as follows: body about 140-180 × 60-70 µm in vivo, cortical granules absent, contractile vacuole positioned about 40% down length of body, 5-9 macronuclear nodules, 34-49 adoral membranelles, 3-5 buccal and 3-6 parabuccal cirri, usually two frontoventral rows, three or four left and two or three right marginal rows, three dorsal kineties and one dorsomarginal kinety; 1-3 and one or two caudal cirri located at the ends of dorsal kineties 1 and 2, respectively. The ontogenetic process is characterized by: (1) the marginal anlagen on each side develop in the outer right and the inner left marginal rows, respectively; (2) five frontoventral-transverse cirral anlagen, anlagen II-IV develop in secondary mode; (3) dorsal morphogenesis follows a typical Urosomoida-pattern, no parental dorsal kineties are retained; (4) caudal cirri are generated at the ends of dorsal kineties 1 and 2. Phylogenetic analyses based on SSU rDNA sequence data reveals that Afrokahliella paramacrostoma n. sp. is closely related to Parakahliella macrostoma and Hemiurosomoida longa.

Morphology and taxonomy of Pseudokeronopsis rubra (Ehrenberg, 1836) and Pseudokeronopsis parasongi sp. nov. (Ciliophora, Hypotrichia, Urostylida) from the Yellow Sea.

Pseudokeronopsis rubra (Ehrenberg, 1836), type species of Pseudokeronopsis, is a widely reported but taxonomically confused species with most available sequences either misidentified or dubious. Based on the Yellow Sea population, of which the molecular data have been analyzed in a previous work, we redescribe P. rubra and try to clarify the identifications of the populations designated as P. rubra or those allocated to this species. Nonetheless, there is still a need of integrated investigation of the species combing both morphological and molecular data based on specimens from its type locality. Recent molecular analyses indicate a Yellow Sea population of Pseudokeronopsis (marked as P. cf. songi) likely represents a new species. Here we describe it as P. parasongi sp. nov. based on the specimens from the same population. The new species possesses a yellow-brownish body with both pigmented cortical granules and colorless blood cell-shaped structures underneath the body surface, invariably one contractile vacuole at 66% of body length and occasionally a second one at 25%, and the midventral complex terminating 2-23 µm ahead of 2-4 transverse cirri. It differs from closely related species by its yellow-brownish body color and separates from them in the ITS1-5.8S-ITS2 and COI genetic distances.

The insights into the systematic relationship of Gastrostyla-affinitive genera, with report on a new saline soil ciliate genus and new species (Protozoa, Ciliophora).

BACKGROUND: Hypotrichia are a group with the most complex morphology and morphogenesis within the ciliated protists. The classification of Gastrostyla-like species, a taxonomically difficult group of hypotrichs with a common ventral cirral pattern but various dorsal and ontogenetic patterns, is poorly understood. Hence, systematic relationships within this group and with other taxa in the subclass Hypotrichia remain unresolved. RESULTS: 18S rRNA gene sequence of a new Gastrostyla-like taxon was obtained. Phylogenetic analyses based on the 18S rRNA gene sequences indicate that this ciliate represents a new genus that is closely related to Heterourosomoida and Kleinstyla within the oxytrichid clade of the Hypotrichia. However, the position of this cluster remains unresolved. All three genera deviate from the typical oxytrichids by their incomplete (or lack of) dorsal kinety fragmentation during morphogenesis. Morphology and morphogenesis of this newly discovered form, Heterogastrostyla salina nov. gen., nov. spec., are described. Heterogastrostyla nov. gen., is characterised as follows: more than 18 fronto-ventral-transverse cirri, cirral anlagen V and VI develop pretransverse cirri, and dorsal ciliature in Urosomoida-like pattern. CONCLUSIONS: Similar to the CEUU-hypothesis about convergent evolution of urostylids and uroleptids, we speculate that the shared ventral cirral patterns of Gastrostyla-like taxa might have resulted from convergent evolution.

A new species of Uronychia (Spirotrichea: Euplotida) from Argentina.

Uronychia clapsae sp. n. was discovered in an artificial channel that drains an endorheic area from the "sandy Pampa" into the upper basin of Salado River, Buenos Aires, Argentina. This euplotid measures 56-112 µm × 42-70 µm in vivo, is oval in shape and the buccal field is enormous, occupying ca. 80% of body length. It is characterized by having two macronuclear nodules and one micronucleus; usually 10 anterior and invariably three posterior membranelles; right end of paroral hook-like; buccal cirrus base about 3.5-6.0 µm long; invariably four frontal, two ventral, three left marginal, four transverse, and three caudal cirri; six dorsal kineties, kinety 1 with 15-22 dikinetids. Most Uronychia species were recorded in marine habitats, while this new isolate was found in a slightly saline, inland water body. Taxonomic and nomenclatorial concerns on some species assigned to Uronychia are also discussed.

An Integrative Investigation of Parabistichella variabilis (Protista, Ciliophora, Hypotrichia) Including Its General Morphology, Ultrastructure, Ontogenesis, and Molecular Phylogeny.

Hypotrichs are a highly differentiated and very diverse group of ciliated protists. Their systematics and taxonomy are challenging and call for detailed investigations on their general morphology, ultrastructure, ontogenesis, and molecular phylogeny. Here, a comprehensive study is conducted on a brackish water population of Parabistichella variabilis using light and electron microscopy and phylogenetic analyses based on small subunit ribosomal DNA sequence data. Its morphology, including the infraciliature, pellicle, nuclei, buccal seal, and extrusomes, is documented. The present findings indicate that in P. variabilis: (i) the cortical granules are extrusomes, which differ from those of other hypotrichs; (ii) the buccal seal is bounded by the plasma membrane and contains a single layer of longitudinal microtubules; (iii) two contractile vacuoles might be present rather than one; and (iv) the pharyngeal disks are bounded by a single membrane. Early-to-middle stages of ontogenesis are described for the first time, enabling the complete characterization of this process. Phylogenetic analyses indicate that Parabistichella variabilis is closely related to several species from different genera, such as Orthoamphisiella breviseries, Uroleptoides magnigranulosus, and Tachysoma pellionellum. However, ultrastructural and gene sequence data for more taxa are needed in order to resolve the systematics of Parabistichella.

Reevaluation of the 'well-known' Paraurostyla weissei complex, with notes on the ontogenesis of a new Paraurostyla species (Ciliophora, Hypotrichia).

Two hypotrichous ciliates, Paraurostyla wuhanensis nov. spec. from Wuhan (China) and a new North American population of the Paraurostyla weissei complex, were studied based on live observations and protargol impregnation. Paraurostyla wuhanensis nov. spec. differs from the congeners by the combined features of having six or seven frontal cirri, 2-4 frontoventral cirri, 5-7 ventral rows, and yellow-greenish cortical granules. Ontogenesis proceeds as in the type species, except that fewer frontoventral cirri are formed in the new species. The morphology of the new population of the Paraurostyla weissei complex corresponds well with other American populations. In the phylogenetic trees based on the 18S rRNA gene, Paraurostyla sequences nest in a large clade together with Apoamphisiella and Notohymena. Monophyly of Paraurostyla is rejected by the results of the approximately unbiased test analyses. Morphological, morphogenetic, and phylogenetic analyses show a close relationship between the North American populations of the Paraurostyla weissei complex and Apoamphisiella, indicating that the taxonomic position of the former needs to be reassigned. A new combination, viz. Apoamphisiella polymicronucleata (Merriman, 1937) comb. nov., a reevaluation of the Paraurostyla weissei complex, and emended diagnoses of Paraurostyla and Apoamphisiella, are provided.

Morphology, morphogenesis, and molecular phylogeny of a novel saline soil ciliate, Heterourosomoida sinica n. sp. (Ciliophora, Hypotrichia).

The living morphology, infraciliature, morphogenesis and phylogenetic position of a new hypotrichous ciliate, Heterourosomoida sinica n. sp., discovered in saline soil in Northwest of China, were investigated. Heterourosomoida sinica n. sp. is characterized as follows: body size about 70-95 × 20-30 µm in vivo, ellipsoid or elongate; cortical granules dark green, 0.5 µm across, arranged around dorsal cilia and in short irregular rows on ventral side; consistently 18 frontoventral-transverse cirri; left and right marginal rows composed of 17-24 and 13-21 cirri, respectively; two macronuclear nodules and one or two micronuclei. The detailed morphogenesis of a species of Heterourosomoida is reported for the first time. The ontogenesis on dorsal side is basically similar to that in Urosomoida-species and the process on ventral side is characterized by: 18 frontoventral-transverse cirri develop from six anlagen with the anlagen V and VI formed in the primary mode. Phylogenetic analyses based on SSU rDNA sequence data reveal that Heterourosomoida sinica n. sp. clusters with Kleinstyla dorsicirrata and forms a clade with the type species H. lanceolata.

Evolutionary Origin and Host Range of Plagiotoma lumbrici (Ciliophora, Hypotrichia), an Obligate Gut Symbiont of Lumbricid Earthworms.

Four common earthworm species, the anecic Lumbricus terrestris, the endogeic Octolasion tyrteum as well as the epigeic Eisenia fetida and Dendrobaena veneta, were examined for the presence of the microbial gut symbiont Plagiotoma lumbrici. The evolutionary origin of this endobiotic microbe was reconstructed, using the 18S rRNA gene, the ITS1-5.8S-ITS2 region, and the first two domains of the 28S rRNA gene. Plagiotoma lumbrici was exclusively detected in the anecic Lumbricus terrestris. Multigene analyses and the ITS2 secondary structure robustly determined the phylogenetic home of Plagiotoma lumbrici populations within the oxytrichid Dorsomarginalia (Spirotrichea: Hypotrichia) as a sister taxon of the free-living Hemiurosomoida longa. This indicates that earthworms obtained their gut endosymbiont by ingesting soil/leaf litter containing oxytrichine ciliates that became adapted to the intestinal tract of earthworms. Interestingly, according to the literature data, Plagiotoma lumbrici was detected in multiple anecic and some epigeic but never in endogeic earthworms. These observations suggest that Plagiotoma lumbrici might be adapted to certain gut conditions and the lifestyle of anecic Lumbricidae, such as Lumbricus, Aporrectodea, and Scherotheca, as well as of some co-occurring epigeic Lumbricus species.

Morphology and molecular phylogeny of a new hypotrich ciliate, Anteholosticha songi nov. spec., and an American population of Holosticha pullaster (Müller, 1773) Foissner et al., 1991 (Ciliophora, Hypotrichia).

A new urostylid ciliate, Anteholosticha songi nov. spec., isolated from forest soil in Tibet, and an American population of Holosticha pullaster (Müller, 1773) Foissner et al., 1991, isolated from a freshwater pond in the USA, are investigated in terms of their morphology, ontogenesis, and molecular biology. Anteholosticha songi nov. spec. is characterized by a slender to ellipsoidal body measuring 160-205 × 40-55 µm in vivo; rod-shaped yellowish cortical granules arranged in irregular short rows; four dorsal kineties; adoral zone consisting of 35-40 membranelles; three frontal, one buccal, one parabuccal, two frontoterminal, two pretransverse, and four to six transverse cirri and 14-25 midventral pairs; 12-22 ellipsoidal macronuclear nodules longitudinally arranged in pairs left of cell mid-line. Supplemental information on morphogenesis in Holosticha pullaster is also presented. The phylogenetic relationship of Anteholosticha and Holosticha inferred from SSU rDNA sequence data are concordant with previous studies and showing that Holosticha is monophyletic whereas Anteholosticha is polyphyletic and should be split into two or more genera.

Two Urosoma species (Ciliophora, Hypotrichia): A multidisciplinary approach provides new insights into their ultrastructure and systematics.

The general morphology and ultrastructure of two soil hypotrichous ciliates, Urosoma emarginata and U. salmastra, were investigated using light microscopy, scanning electron microscopy and transmission electron microscopy. Phylogenetic analyses, based on the newly sequenced small subunit ribosomal (SSU) rRNA genes, were conducted on three U. emarginata populations and one U. salmastra population. Our findings support for the validity of Perilemmaphora Berger, 2008, a rankless taxon comprising spirotrich ciliates having a perilemma. The cortical granules of both species are extrusomes representing a new type of mucocyst in U. emarginata and possibly a new type of pigmentocyst in U. salmastra. Additionally, the lithosomes were revealed as subglobose structures composed of a low electron-dense, homogeneous inner part and an electron-dense outer part. The ultrastructural features of the cortical granules, together with ontogenetic and molecular phylogenetic data, suggest that the genus Urosoma might need to be divided. It is posited that ultrastructural features of hypotrichous ciliates in general may have important taxonomic value warranting further investigation.

Morphological and molecular characterization of Neogastrostyla aqua nov. gen., nov. spec. (Ciliophora, Hypotrichia) from River Yamuna, Delhi; comparison with Gastrostyla-like genera.

A novel hypotrichous ciliate, Neogastrostyla aqua nov. gen., nov. spec. isolated from River Yamuna, Delhi, India, is described using morphological, morphometric and morphogenetic characters from live and stained cells supplemented with derivation of phylogenetic relationships using SSU rRNA gene. Neogastrostyla aqua nov. gen., nov. spec., is characterized by light yellow cortical granules present singly or in clusters of two to five, distributed randomly; parental adoral zone of membranelles retained unchanged for proter; Oxytricha-pattern of paroral and endoral; 25-27 frontal-ventral-transverse cirri including a distinct bipartite frontoventral row of composite origin; three dorsal kineties with no fragmentation of the third kinety, two dorsomarginal kineties, three caudal cirri, two macronuclear nodules and two or three micronuclei. Though Neogastrostyla aqua nov. gen., nov. spec. has a frontoventral row like Gastrostyla species, it differs distinctly in the combination of characters from Gastrostyla and other genera with Gastrostyla-like ventral ciliature (Protogastrostyla, Hemigastrostyla, Apogastrostyla and Pseudogastrostyla) particularly in the colour and distribution of cortical granules as well as arrangement and formation of ciliature. According to the phylogenetic analyses, Neogastrostyla aqua nov. gen., nov. spec. clustered consistently with Gastrostyla sp. Y2 (no description available), Oxytricha granulifera and Architricha indica as close neighbours.

Morphogenesis and Molecular Phylogeny of the Soil Ciliate Holostichides chardezi (Ciliophora, Hypotrichia, Bakuellidae), with Redefinition of Holostichides Foissner, 1987 and Establishment of a New Genus Anteholostichides.

Morphogenesis of the soil hypotrich ciliate, Holostichides chardezi Foissner, 1987, collected from southeastern China, was investigated using the protargol staining method. The main morphogenetic events follow a similar process with that of its congeners. Phylogenetic analyses based on the SSU rDNA sequence data indicate that Holostichides is nonmonophyletic; H. chardezi, the type species of Holostichides, clusters with H. heterotypicus, while H. terrae is distinctly separate from these species. H. terrae can be distinguished from H. chardezi (type species of Holostichides) and H. heterotypicus by undulating membranes relatively long and distinctly curved (vs. relatively short and straight), pharynx with (vs. without) rod-shaped structure, and two (vs. more than two) frontoterminal cirri. Therefore, a new genus, Anteholostichides nov. gen., has been proposed for H. terrae. Further, the diagnosis of the genus Holostichides is improved.

Morphogenesis and Molecular Phylogeny of a Soil Ciliate Uroleptoides longiseries (Foissner, Agatha and Berger, 2002) Berger 2008 (Ciliophora, Hypotrichia).

Morphogenesis of the hypotrich ciliate Uroleptoides longiseries, isolated from sandy soil beside the Yellow River, Suide, Yulin, Shaanxi Province, China, was investigated using protargol staining. The main events during binary fission are as follows: (1) the long frontoventral row is formed by a single anlage; (2) five frontoventral-transverse cirral anlagen are formed in primary mode; (3) only the posterior part of the parental adoral zone of the membranelles is renewed; and (4) the oral primordium of the opisthe is formed intrakinetally. This is the first detailed record of all stages of morphogenesis for Uroleptoides. We also provide the first record of the small subunit ribosomal DNA (SSU rDNA) sequences for U. longiseries. Phylogenetic analyses based on the SSU rDNA sequences data show that Uroleptoides longiseries clusters with U. magnigranulosa with moderate to high support which together form a clade with Orthoamphisiella breviseries. These three species share the morphogenetic feature of the long frontoventral row being formed by a single anlage.

Morphology and morphogenesis of a new soil urostylid ciliate, with the establishment of a new genus Caudiurostyla gen. nov. (Ciliophora, Hypotrichia).

The living morphology, infraciliature and morphogenesis of a new urostylid ciliate, Caudiurostyla sinensis gen. nov., spec. nov., isolated from a soil habitat in China, was investigated. The new, monotypic genus is defined by having frontal cirri arranged in a bicorona, distinct transverse cirri, midventral pairs only, buccal cirrus, frontoterminal cirri, multiple marginal cirral rows that replicate independently via within row anlagen formation, more than three dorsal kineties, and caudal cirri. The main morphogenetic features of the new species are: (1) the posterior part of the parental adoral zone is renewed in situ; (2) the marginal cirral rows and dorsal kineties develop intrakinetally; (3) a caudal cirrus is formed at the posterior end of each dorsal kinety; and (4) macronuclear nodules fuse into a single mass during the middle stage. Based on the morphology and morphogenesis, the new genus differs from Pseudourostyla and Hemicycliostyla by presence of caudal cirri.