Revision of the Vietnamese millipede genus Annamina Attems, 1937, with descriptions of three new species (Diplopoda, Polydesmida, Paradoxosomatidae)

Abstract The hitherto monotypic diplopod genus Annamina contains now four species, including the revised type-species A. xanthoptera Attems, 1937, as well as A. attemsi sp. n., A. irinae sp. n. and A. mikhaljovae sp. n., all from central or southern Vietnam. The genus is rediagnosed and a key to its constituent species given.


Introduction
The monotypic millipede genus Annamina Attems, 1937, and its type species A. xanthoptera Attems, 1937, were described twice nearly simultaneously from Vietnam, first in a global review of the family Paradoxosomatidae (= Strongylosomatidae) (Attems 1937) and the second time in a large paper on the Myriapoda of Indochina (Attems 1938). Although the designation of Annamina xanthoptera as a new genus and species appeared in 1938, the actual publication date was 1937.
The genus Annamina belongs to the tribe Sulciferini Attems, 1898 and differs from the other, mostly Asian genera by a remarkably short flagelliform solenomere and an even shorter, chitinous, tooth-shaped solenophore devoid of membranous elements (Jeekel 1968). Annamina xanthoptera, the only hitherto known species of the genus, was described from near Danang, central Vietnam (Attems 1937(Attems , 1938 and has never been recorded since. Recently, three new Annamina species were discovered in southern and central Vietnam. One of these, A. attemsi sp. n., was incidentally found by NA when documenting the type material of A. xanthoptera in the Naturhistorisches Museum Wien (NHMW). In this work, we redescribe A. xanthoptera, based on the type material, and select a lectotype to stabilize the species' taxonomy. We also describe three new species: A. attemsi sp. n., A. irinae sp. n. and A. mikhaljovae sp. n., as well as refine the diagnosis of the genus and provide a key to all four species known to date.

Material and methods
New material that contained two new species of Annamina was taken in 2015 and 2016 during field trips of I. I. Semenyuk (Moscow, Russia) to southern Vietnam in the framework of the research activities of the Joint Russia-Vietnam Tropical Centre. The types of both are deposited in the Zoological Museum of the Moscow State University, Russia (ZMUM). The ZMUM types are preserved in 75% ethanol. Pictures were taken with a Canon EOS 5D digital camera and stacked using Zerene Stacker software.
The NHMW types are preserved in 75% alcohol. Measurements and photographs were taken with a Nikon DS-F2.5 camera mounted on a Nikon SMZ25 stereo microscope, using NIS-Elements Microscope Imaging Software with an Extended Depth of Focus (EDF) patch. All images were processed with Adobe Photoshop CS6 and assembled in Adobe InDesign. For taking SEM micrographs, the gonopods of A. xanthoptera and A. attemsi sp. n. were dehydrated in 96% ethanol and acetone, then air dried, mounted on aluminium stubs, coated with platinum and examined using a JEOL JSM 6610 scanning electron microscope.
Several paralectotypes of A. xanthoptera, preserved in 70% alcohol, are housed in the Muséum national d'Histoire naturelle, Paris (MNHN). They were only measured and checked for their species identity.
Gonopod mostly stout, prefemoral (= densely setose) region small, much shorter than femorite, the latter usually with evident, sometimes hyline, mesal and/or ventral lobes, clearly set off by sulci from both pre-and postfemoral parts; seminal groove mostly dorsal, not mesal, running onto a short flagelliform solenomere on mesal face near distal (= postfemoral) sulcus; acropodite consisting of a prominent central spine sometimes flanked by a mesal and/or a lateral process/outgrowth and carrying parabasally or near midway an inconspicuous, short, dentiform, ventral solenophore devoid of membranous elements and subtending the distal part of solenomere.
Type species. Annamina xanthoptera Attems, 1937 Other species included. A. attemsi sp. n., A. irinae sp. n. and A. mikhaljovae sp. n. Lectotype designation was necessary so that the species is based on a complete male that fully matches the original description of A. xanthoptera by Attems (1937). Gonopods were removed and newly examined using one of the NHMW paralectotypes.

Annamina xanthoptera
Diagnosis. Differs from other members of the genus primarily by showing both the median lobe and the lateral process of the gonopod telopodite strongly microdenticulate-serrate. See also Key below.
General coloration after many years of preservation in alcohol apparently somewhat faded, rather uniformly light to castaneous brown, without a distinct pattern, sides lighter; telson, legs and ventral parts light brown to yellowish (Fig. 1). Clypeolabral region setose, setae becoming scattered between antennae; vertigial region with 2+2 setae; epicranial suture thin, superficial.
Comments. Attems (1937Attems ( , 1938 failed to indicate the number of specimens in the type series of A. xanthoptera while the only measurements he gave in the descriptions (width of pro-and metazona 1.8 and 2.5 mm, respectively) may have misleadingly been taken as concerning a single specimen. However, the type series is quite large and presently divided between the MNHN and NHMW collections. Moreover, the NHMW type material actually houses two different species of Annamina, most of which truly represents A. xanthoptera. The minor admixture, however, is described below as still another new species, the types being deposited in the NHMW.
A complete catalogue of references to A. xanthoptera is available in Nguyen and Sierwald (2013 Diagnosis. Differs from other species of the genus primarily by an unusually slender telopodite of the gonopod which is only supplied with an apical process. See also Key below. Name. Honours the famous Austrian myriapodologist Carl Attems (1868Attems ( -1952, one of the most prominent taxonomists of Diplopoda of his time. Description. Measurements (mm): Body length ca 18.7 (holotype) or 21.6 (♂ paratype), width of midbody prozonae 1.2 (holotype) or 1.3 (♂ paratype), width of midbody metazonae 1.8 (holotype) or 2.0 (♂ paratype).
All other characters (see Figs 5-7) as in A. xanthoptera, except as follows.
Caudal corner of paraterga dentiform and acute-angled starting with segment 4, drawn behind rear tergal margin starting with segment 11 (♂); a second lateral denticle on paraterga completely absent from segments 18 and 19. Transverse sulci fully developed on metaterga 5-17, deep, beaded at bottom and almost reaching the bases of paraterga, weaker on segment 18, absent from 19 th .
Gonopods (Figs 6, 7) somewhat disjunct, especially intricate in structure; coxite (cx) moderately setose distoventrally; telopodite much more slender than in A. xanthoptera; femorite (fe) much narrower, distally especially so, showing an inconspicuous and less strongly granulated mesal lobe (ml), as well as a hypertrophied, hyaline, irregularly rounded, ventral lobe (vl) folded mesad; seminal groove running laterad along dorsal part of fe, passing distally onto a short flagelliform solenomere (sl); the latter subtended distally by a small, apically bilobulate, ventral tooth (t) (= solenophore) arising from about midway of a long, pointed, spiniform, apical process (a), this being equipped with a minute, subapical, hyaline ridge (r); lateral process (lp) rudimentary, lying a little distal to postfemoral sulcus (su), with a minute spike on top, placed just at base of a; no mesal process whatsoever.   Name. Honours Irina Semenyuk, the collector. Diagnosis. Differs from other species of the genus primarily by the presence of a small ventral lobe and a large mesal lobe on the gonopod femorite, coupled with a small, simple, mesal process, a long, spiniform, lateral process and a prominent, simple, unciform, acuminate, apical process in the postfemoral portion of the gonopod. See also Key below.
Description. Measurements (mm): Body length of all types ca 24, width of midbody pro-and metazona 1.5 and 1.9, respectively.
General coloration in alcohol light brownish to brown, but with a characteristic pattern of a vague, lighter, subtriangular, central spot on each postcollum metatergum flanked on each side by marbled brown patches fused into a complete transverse band in anterior 1/3; sides mostly brown to light brown, lighter closer to coxae; strictures between pro-and metazonae, paraterga both dorsally and ventrally, telson, legs and venter pale yellowish to whitish (Fig. 8). Antennae nearly pallid, only distal parts of antennomeres 2-5 slightly infuscate, light brown; entire antennomeres 6 and 7 brown; tip of antennae contrasting pallid.
All characters (see Figs 8,9) as in A. xanthoptera, except as follows.
Gonopods (Figs 8E,9) relatively complex; coxite (cx) moderately setose distoventrally; telopodite consisting of a short prefemoral (= densely setose) part set off from femorite (fe) by an oblique sulcus; femorite (fe) stout, distinctly flattened dorsoventrally, set off from acropodite by a subtransverse postfemoral sulcus (su), with a smaller, rounded, hyaline, ventral lobe (vl) and a much larger, parabasal, somewhat ear-shaped, mesal lobe (ml); seminal groove quickly moving laterad to mostly lie on dorsal side of fe before passing onto a short, free, flagelliform solenomere (sl) near su, with a small finger-shaped mesal process (mp) lying at base of sl; postfemoral part consisting of a large, spiniform, slightly curved, acuminate, apical process (a) flanked by a considerably shorter, likewise spiniform and slightly curved lateral process (lp) and a short, stout, ventral, trifid tooth (t) (= solenophore) subtending the basal half of sl. Diagnosis. Differs from other species of the genus primarily by the presence of a small ventral lobule and a large mesal lobe on the gonopod femorite, coupled with, much like in A. irinae sp. n., a small, simple, mesal process, a similarly short, but spiniform, clearly serrate lateral process and a prominent, lobe-shaped, apical process in the postfemoral portion of the gonopod. See also Key below.
All characters (see Figs 10, 11) as in A. xanthoptera, except as follows.

Discussion
Even with such a considerable increase in species diversity as described above, Annamina remains a well-defined and quite homogeneous group within the paradoxosomatid tribe Sulciferini. The genus is remarkably uniform in most of the characters of its constituent species, both somatic and gonopodal, as well as in distribution which is confined to south-central and central Vietnam. Annamina is unique amongst the contribal genera in the high, well-developed, laterally mostly monodentate and caudally largely triangular (but never pointed) paraterga; the strongly ribbed strictures between pro-and metazonae; the microgranulate sides of metazonae; the inconspicuous, nearly missing pleurosternal carinae; the uniformly roundly subtriangular hypoproct; the unusually high, subtriangular, setose and apically truncate sternal lobe between ♂ coxae 4; the absence both of adenostyles and ventral brushes on remarkably long and slender legs; and, above all, the special conformation of the gonopodal telopodite.
It is the latter that provides most of the characters useful for a confident separation of species in Annamina (see Key below). The gonotelopodite always shows an enlarged basal part of the femorite which is clearly flattened dorsoventrally. The femorite is set off from the acropodite by a distinct subtransverse sulcus or cingulum (su) that marks a postfemoral region more distally, a trait that, together with the presence of a number of femoral and postfemoral outgrowths or processes, allows the placement of the genus in Sulciferini (cf. Jeekel 1968). In Annamina spp., the femorite (fe) shows no longitudinal mesal groove so characteristic of numerous Sulciferini (Oxidus Cook, 1911, Tylopus Jeekel, 1968, Sichotanus Attems, 1914, Cawjeekelia Golovatch, 1980, but instead it has two more or less distinct lobes: one hyaline, rounded and ventral in position (vl), often folded mesad and especially hypertrophied in A. attemsi sp. n., the other a mesal, typically papillate or microdenticulate bulge (ml) which is particularly prominent in A. xanthoptera and A. mikhaljovae sp. n. The seminal groove in Annamina, unlike that in the remaining sulciferines, runs along the femorite not so much mesally as dorsally, to follow onto a surprisingly short and flagelliform solenomere (sl) detached on the dorsomesal face about the level of the postfemoral sulcus. This condition seems to be apomorphic, as is the complete absence of significant membranous elements in the solenophore which is represented by a rather small and short tooth (t), sometimes subtruncate, bi-or trifid, that subtends the distal part of the solenomere, leaving only the latter's tip exposed beyond t. The solenophore tooth is located ventrally near the base (usually) or close to the midpoint (A. attemsi sp. n.) of a centro-apical process or spine (a), always hyaline, sometimes lobe-shaped, but more often acuminate, invariably the longest and largest of the postfemoral outgrowths. Process a can be flanked by two distinct, albeit shorter, processes: one lateral (lp), which is serrate in A. xanthoptera and A. mikhaljovae sp. n., but simple in A. irinae sp. n., the other mesal (mp) which is long in A. mikhaljovae sp. n., very short in A. irinae sp. n. and absent from the other two congeners. Process lp can also be rudimentary: A. attemsi sp. n.
Based on gonopodal structure alone, this latter species seems to be the most disjunct among congeners (see its diagnosis above and Key below). Since it seems to co-occur with A. xanthoptera near Danang, this observation agrees well with the general wisdom that two sympatric or even syntopic congeners tend to differ more strongly than others.
The above outline of the diversity of and variations in gonopodal characters in Annamina spp. helps us not only to better redefine the genus against the other Sulciferini, but also to key all of its four presently known species. Because the millipede fauna of Vietnam is the richest in Indochina, but still quite poorly known, it seems very likely that further Annamina species will be found in the future.