Three new species of the millipede genus Tylopus Jeekel, 1968 from Thailand, with additional notes on the species described by Attems (Diplopoda, Polydesmida, Paradoxosomatidae)

Abstract Tylopus currently comprises 55 species, including three new from Thailand: T. corrugatus sp. n., T. trigonum sp. n. and T. parahilaroides sp. n. A new distribution map and an updated key to all 29 species of Tylopus presently known to occur in Thailand are given. Illustrated redescriptions of all four Indochinese Tylopus species described by Carl Attems are also provided, based on type material.


Introduction
The Southeast Asian millipede genus Tylopus Jeekel, 1968 is one of the most speciose not only in the mainly Asian tribe Sulciferini, but also in the whole family Paradoxosomatidae. The latter is probably the largest in the entire class Diplopoda, dominating the millipede fauna of Indo-Australia (Jeekel 1968) and currently comprising nearly 200 genera and over 1,000 species (Nguyen and Sierwald 2013;authors' records). At the moment, all 52 constituent species of Tylopus range from southern China, through Laos, to Myanmar, western Thailand and southern Vietnam. Since the thorough reviews of the genus by Golovatch and Enghoff (1993) and Likhitrakarn et al. (2010), both of which focused on the fauna of Thailand, Nguyen (2012) provided a synopsis of and a key to all 18 species of Tylopus occurring in Vietnam, while Golovatch (2013Golovatch ( , 2014 summarized all six congeners recorded in southern China. The present paper is an updated review of all 29 Tylopus currently known from Thailand (Table 1), including three new congeners. In addition, all four Indochinese Tylopus species described by Carl Attems are redescribed and illustrated, based on the types kept in the collection of the Naturhistorisches Museum Wien, Austria.

Material and methods
New material was collected in northern Thailand and southern Laos from 2011 to 2013 by SP and members of the Animal Systematics Research Unit, Chulalongkorn University. Live animals were photographed in the laboratory shortly before fixing. Specimens were preserved in 75% ethanol, and morphological investigations were carried out in the laboratory using an Olympus stereomicroscope. Scanning electron micrographs (SEM) of gonopods coated with gold were taken using a JEOL, JSM-5410 LV microscope, and the gonopods removed from stubs and returned to alcohol after examination. Digital images of preserved specimens were taken in the laboratory and assembled using the "Cell D " automontage software of the Olympus Soft Imaging Solution GmbH package. In addition, line drawings of gonopod characters were also prepared. Type material of the Attemsian congeners housed in the Vienna Museum was photographed with a Dino-Eye Eyepiece USB Camera AM423X, the digital images assembled using the automontage software technique, and the gonopods redrawn. Holotypes of the three new species, as well as most of the paratypes are housed in the Museum of Zoology, Chulalongkorn University (CUMZ), Bangkok, Thailand, a single duplicate paratype being donated to the collection of the Naturhistorisches Museum Wien, Austria (NHMW), as indicated in the text.
Collecting site positions and elevations were determined by GPS using the WGS84 datum.
In the catalogue sections, D stands for the original description, subsequent descriptive notes or appearance in a key, R for a subsequent record or records, and M for a mere mention.  Hoffman 1973, Golovatch and Enghoff 1993.
Coloration of live animals dark castaneous brown (Fig. 4A); legs red-brown, venter and a few basal podomeres light brown to yellow-brown; coloration of alcohol material after a half year preservation faded to dark brown; antennae and epiproct light brown to pallid, venter and a few basal podomeres light brown to pallid ( Fig. 4B-H).

Tylopus trigonum
Diagnosis. This new species shows a peculiar colour pattern, much like that observed in T. schawalleri Golovatch, 2013, but differs in gonopod process h being rather short and coiled (versus high and strongly twisted), as well as by the presence of a process m (versus absent).
Coloration of live animals light brown (Fig. 6A); paraterga, legs and epiproct light brown, head and collum blackish, following terga with a light brown triangle and blackish collar covering both pro-and metazonae; coloration of alcohol material after three years of preservation faded to whitish with a pattern of a contrasting dark brown inverted triangle at anterior edge of metazonae and a light brown triangle at posterior edge of prozonae ( Fig. 6B-H).

Tylopus nodulipes (Attems, 1953) Figs 8, 9
Agnesia nodulipes Attems, 1953: 174 (D). Lectotype designation proposed herewith is necessary to ensure the species is based on a complete ♂ coming from a certain locality, because (1) Attems (1953) provided no information on the number and sex of syntypes, and (2) he stated their provenance to have been both from Luang Prabang, Laos and Mount Fan-Si-Pan, Lao Cai Province, Vietnam. No paralectotype material could be traced in the Vienna Museum.
Redescription. Lectotype ca 24 mm long, width of midbody pro-and metazonae 2.1 and 2.9 mm (vs 3.0 in width, as given in the available description (Attems 1953)). Coloration of alcohol material after long preservation rather uniformly light reddish brown (Fig. 8A-G) with light yellow antennae, paraterga, epiproct and legs (versus dark maroon with light yellowish brown mid-dorsal parts of prozonae, paraterga a little lighter, antennae light chestnut brown and legs yellow brown, as given in the original description (Attems 1953)).
Remarks. This is the type species of Tylopus Jeekel, 1968, originally recorded from two localities: Luang Prabang Province, Laos and Mount Fan-Si-Pan, Lao Cai Province, Vietnam (Attems 1953). Golovatch (1984) redescribed and illustrated only a gonopod, but the locality remained unclear. So the lectotype is herewith selected for the sole type specimen still kept in the Vienna Museum.
This species has recently been reported from Nam Xay Commune (

Tylopus sigma (Attems, 1953) Figs 12-13
Sundanina sigma Attems, 1953: 171 (D). Lectotype designation proposed herewith is necessary to ensure the species is based on a complete ♂, because Attems (1953) provided no information on the number and sex of syntypes.

Tylopus mutilatus (Attems, 1953)
Remark. This species was described both from Luang Prabang, Xieng Kuang, Laos and Pic de Langbiang (Mount Langbian), Lamdong Province, Vietnam (Attems 1953). Golovatch (1984) redescribed and illustrated only a gonopod, but the locality remained unclear. As all our attempts at locating a torso of T. sigma in the collection of the Naturhistorisches Museum Wien, Austria had failed, we could only revise the very same right gonopod mounted on a slide. Fortunately, the gonopod is easily distinguished from congeners.
Key to the species of Tylopus currently known to occur in Thailand, chiefly based on ♂ characters: 1 Most ♂ prefemora clearly swollen laterally (Fig. 5C)  Sternal lamina between ♂ coxae 4 fully divided into paramedian knobs (Fig. 1I, J)

Conclusions
Of a total of 55 species of Tylopus known now, Thailand supports as many as 29, followed by Vietnam (18 species), southern China (six species), Laos and Myanmar (two species each). The distributions of Tylopus spp. in Thailand, most of which are endemic to the country, are shown in Map 1.
Almost all Tylopus species appear to be confined to montane forest habitats. In Thailand, Tylopus have only been taken from localities exceeding 500 m in elevation, except for Tham Pha Nang Khoi (275 m a.s.l) which solely supports the especially widespread T. perarmatus. In contrast, Doi Inthanon and Doi Suthep mountains each harbour as many as 10 species (Table 1), one of the highest values for congeners per local faunule among all Diplopoda, following perhaps the madeirae-group of Cylindroiulus endemic to Madeira, Portugal (29 spp., Enghoff 1982, Read 1989 or Dolichoiulus on Teneriffe, Canary Islands, Spain (21 spp., Enghoff 1992Enghoff , 2012.
There is no doubt that more species of Tylopus will be found in the future, as at least the faunas of southern China, Myanmar, Laos and even Vietnam seem to be quite underrepresented compared to Thailand, while Cambodia is a completely blank area.