Monographis thatsonensis, Huynh, 2022

Huynh, Cuong, 2022, Four new species of Monographis Attems, 1907 (Diplopoda, Polyxenida, Polyxenidae) from Vietnam, Zootaxa 5214 (3), pp. 393-420 : 411-413

Monographis thatsonensis new species

Figures 2 , 18–23

Material examined: Holotype, adult male (IEBR-Myr 993) and paratypes: Adult, two males (IEBR-Myr 994) two females (IEBR-Myr 995) and subadults, three females with 12 pairs of legs (IEBR-Myr 996) were collected from Cam Mountain , 10.496944N, 104.981389E; elevation 662 m, in the Seven Mountain Ranges (That Son), located in Tri Ton and Tinh Bien districts, An Giang Province, Vietnam. All types were deposited in the Institute of Ecology and Biological Resources, Vietnam. Specimens were collected by author CH on 8 th July 2017.

Diagnosis: Body length 2.0–3.0 mm. Antennal article VI with 15–16 bacilliform sensilla forming crescent shape, setiform sensillum located in anterior position, conical sensillum present near centre of crescent. Labrum asetose, long slender anterior setae on anterior margin. Telotarsus with anterior and posterior lateral processes equal in length and shorter than half-length of claw, lamella processes present, anterior setiform process longer than claw.

Description:

Holotype male body 2.0 mm; paratypes: males 2.0– 2.2 mm, females 2.4–3.0 mm; caudal bundle 0.5 mm, nest trichomes 0.2 mm.

Head: Arrangement of post vertex trichomes as for Monographis cattienensis with the holotype having 12 sockets on both sides in anterior rows, posterior rows with 4 sockets (L) and 3 sockets ( R) ( Figures 18A & 18B , 22A ). Paratype showed anterior rows with 12–16 sockets, posterior rows with 3–4, these setae shorter in length than labrum width (Paratype with 8–10 setae). Clypeo-labrum: Holotype, labrum surface asetose (l), labrum posterior margin has a row of minute backward-pointing setae (sb). Lateral lamella (Ll) and single broad lamella each side median cleft (mc), 12 (L) and 8 ( R) slender setae (sa) present on anterior margin of labrum ( Figures 18C & 22C & 22D ) .

Antennae: Antennal article VI with 15–16 bacilliform sensilla. Holotype with 15 bacilliform sensilla forming a crescent shape with 3 thick ( T), 3 thin bacilliform sensilla (t), 3 medium-length thin bacilliform sensilla (tm), and 6 short thin bacilliform sensilla (ts), setiform sensillum (S) located in anterior position, conical sensillum (C) present near centre of crescent ( Figures 19C , 21B & 21D ).

Telotarsus: Claw slender, anterior (a) and posterior lateral (p) processes equal in length and shorter than halflength of claw (c), lamella processes (la) present, anterior setiform process (s) longer than claw ( Figures 20B & 23D ).

Telson: Arrangement of dorsal ornamental trichome sockets similar to M. cattienensis with 14 trichome sockets a left side and 15 sockets on right side of the telson in the holotype (paratype with 14–18 sockets). ( Figures 20C , 23A & 23B ).

Remarks: Monographis thatsonensis sp. n. showed a distinctive pattern of sensilla on antennal article VI, labrum structures, anterior and posterior lateral processes equal in length and shorter than half-length of claw, anterior setiform process longer than claw.

Etymology: Monographis thatsonensis is named after the Seven Mountain Ranges, derived from Sino-Vietnamese, meaning: That Son, in An Giang Province, Vietnam.

Figures

FIGURE 2. Live specimen of Monographis thatsonensis sp. n., its appearance is typical of Monographis species (Diplopoda, Polyxenida)—commonly yellowish brown in colour, darker on the latero-posterior rosette trichomes, forming two dark lateral bands contrasting with a light-yellow medial band.

FIGURE 18. Holotype male Monographis thatsonensis sp. n.. A. A head capsule showing eye patterns with eight ommatidia and trichobothria (a, b, and c) each side, vertex region (v), anterior vertex (av), posterior vertex trichome sockets (pv); B. Enlarged images of posterior vertex (pv) trichome sockets on left (pv (L)) and right (pv (R)). C. Clypeo-labrum showing labrum (l) with asetose surface, lateral labrum (Ll), anterior setae (sa), backward-pointing setae (sb), and posterior setae (Se, 4 setae and 6 sockets of missing setae).

FIGURE 19. Holotype male Monographis thatsonensis sp. n.. A. Antennal articles V, VI, VII and VIII with sensory cones (sc), and patterns of sensilla on article VI and VII; B. Article VII showing two thick bacilliform sensilla (Ta: anterior & Tp: posterior), setiform (S), and a conical sensillum (C); C. Article VI showing three thick bacilliform sensilla (T), three thin bacilliform sensilla (t), three medium-length thin bacilliform sensilla (tm), and six short thin bacilliform sensilla (ts), a conical sensillum (C).

FIGURE 20. Holotype male Monographis thatsonensis sp. n.. A. Second leg showing seven articles: coxa (co), prefemur (pf), femur (f), postfemur (pof), tibia (tib), tarsus 1 (T1), tarsus 2 (T2); claw (c) and penis (p). B. Telotarsus showing claw (c) and all processes: anterior (a), posterior (p), setiform (s) and the lamella (la). C. Ornamental trichome sockets showing the arrangements on both sides: trichome sockets a, b, c, and indentation d.

FIGURE 21. SEM images of Monographis thatsonensis sp. n.. A. Head capsule showing left antenna with eight articles, eye pattern with eight ommatidia, and the trichobothria. B. Antennal articles VI–VIII, showing the arrangement of sensilla. C. Antennal articles VII showing the typical pattern of sensilla and VIII with sensory cones (sc). D. Arrangement of sensilla on article VI.

FIGURE 22. SEM images of Monographis thatsonensis sp. n.. A. The head—right side showing the posterior vertex (pv) trichome sockets and trichobothria (a, b, and c). B. Coxal glands on legs VIII and IX (pointed arrows). C. Clypeo-labrum showing structure of labrum (l) with asetose surface, lateral labrum (Ll), medial cleft (mc), anterior setae (sa), posterior setae (Se), backward-pointing setae (sb). D. Gnathochilaria (g): lateral palps (Lp) and median palps (Mp), the frons (f), labrum (l).

FIGURE 23. SEM images of Monographis thatsonensis sp. n.. A. Male’s caudal bundle with ornamental trichome sockets (ots) a, b, c and d; and telson (Te), and the bundle with caudal bundle trichome sockets (cbts), barbate trichome sockets (bts); the last pleural projection (pp). B. Female’s caudal bundle structure showing the same dorsally, except the presence of two bundles of nest trichome sockets ventrally (nts). C. Presence of two spines—Tarsus 1 and 2, typical of Monographis species. D. Telotarsus showing a claw (c) and all processes: anterior (a), posterior (p), anterior setiform process (s) and lamella (la).