Sphaerobelum meridionalis Bhansali & Wesener 2022, new species

Sphaerobelum meridionalis Bhansali & Wesener, new species

Figures 2A, 3, 4, 5, 6A.

Diagnosis. Differs from all other species of the genus Sphaerobelum aside from S. aesculus in the shape of the posterior telopod, where there is a swelling at the tip of the immovable finger, but the swelling does not extend above the margin (Fig. 5B). Both species also share numerous other characteristics, such as general size and color, the glabrous, leather-like surface of the tergites and the shape of the anal shield, the low number of ventral spines on the legs, as well as the absence of apical spines on leg 3. S. meridionalis sp. nov. differs from S. aesculus in several characters, such as the presence of a distinct mesal process on the prefemur of midbody legs (Fig. 4B, arrow) (absent in S. aesculus), a mesal coxal process on the first coxae (Fig. 4A) (absent in S. aesculus), the telopoditomeres 3 and 4 of the anterior telopods being clearly separated (Fig. 4F) (being almost fused in S. aesculus) as well as some minor characters such as the lower number of ventral spines on the first tarsi (1 versus 4 in S. aesculus) and the slightly higher number of apical cones on the antenna (68–73 versus 52–56 in S. aesculus) (Fig. 3B). S. meridionalis sp. nov. differs from S. aesculus by an uncorrected p-distance on the COI gene of 17% (Sup. file 1).

Derivatio nominis. meridionalis, Latin for southern, adjective used as noun. Noun in apposition.

Material examined (total: 1 ♂)

Holotype

THAILAND: 1 ♂ (fragmented), MHNG 4 B-2, Yala Province Yala, Bannang Sata District, Bang Lang National Park, near Than To Waterfall, [probably 6°11'47.50"N, 101° 9'50.90"E], 150 m, 1.II.1991, leg. P. Schwendinger.

Description (based on holotype)

Size. Length 26.8 mm. Width of thoracic shield 13.3 mm, of widest segment 14.4 mm. Height of thoracic shield 7.9 mm, Height of highest segment (8) 8.8mm.

Color. Faded after 30 years in 75% ethanol. Head medium brown. Antenna pale light brown with traces of green and a brown border. Last antennomere distinctly light green. Legs pale brown, tarsi greenish. Tergites and anal shield medium brown with green color, ventral side light green. Posterior margin of tergites medium brown. Thoracic shield-like tergites but groove greenish.

Head. Number of ommatidia low, 61–65. Tömösváry organ located in antennal groove. Antennae short, reaching to center of head, antennomere lengths: 6>1>3=4>2=5. Last antennomere apically slightly swollen (Fig. 3A), number of apical cones 73/68 (Fig. 3B).

Mandible. Not dissected.

Gnathochilarium. Lingual lamella with numerous long setae. Palpi with sensory cones arranged in single field.

Collum. Setae distributed towards borders, more concentrated at lateral ends. Glabrous on posterior and median region.

Thoracic shield. Grooves wide and deep, with 5 or 6 sclerotized ledges along inner ridge. Surface like tergites.

Tergites. Paratergite tips on posterior half projecting backwards. Tergites glabrous with dull leather-like surface.

Endotergum (Fig. 6A). With a regular flat margin. Outer zone with three rows of irregular marginal setae, not extending beyond posterior margin, but reaching 4/5 of outer area. Middle section with a single row of distant, oval cuticular impressions. Distance between impressions twice the diameter. Inner area with numerous rows of setae, widely distributed, shorter than marginal setae.

First stigmatic plate (Fig. 4A). Large, larger than coxa, with a well-rounded apex.

Pleurites. Pleurite 1 weakly projecting posteriorly with a sharp apex. Pleurite 2 short with well-rounded apex, not projecting.

Legs. Ventral spines on leg 1 1/1, on 2 2/2, on 3 4/4. Apical spine absent on leg 3. Three apical and 6 or 7 ventral spines on midbody legs (Fig. 4B). Inner margin of femur with up to 20 small teeth, but not excavated. Femur 1.7, tarsus 3.8 times longer than wide. Prefemur with conspicuous mesal process (Fig. 4B arrow). First coxae with conspicuous mesal process (Fig. 4A).

Anal shield. Well-rounded and glabrous. Ventral side with single medium length locking carina, placed close to margin.

Male sexual characters. Gonopore (Fig. 4C) large, consisting of large membranous opening located directly at mesal margin of second coxa, covered posteriorly by a single semicircular sclerotized plate.

Anterior telopods (Figs 4D–G). Syncoxite with few setae. Podomere 1 rectangular 1.2 times longer than wide, more densely covered with setae in apical half than at basal margin, with longer setae medially, basal margin glabrous. Podomere 2 with wide process visible in anterior view, protruding to half-length of podomere 3. Process curved, well-rounded, apically slightly tapering (Fig. 4D). Podomere 3 cylindrical, almost twice as long as wide, latero-apical process juxtaposed to process of podomere 2. One spine visible in lateral view. Podomere 4 clearly separated from podomere 3, cylindrical, of half-length of podomere 3, with one spine below apex visible in posterior and lateral view.

Posterior telopods (Fig. 5). Syncoxite inner horns (not drawn): well-rounded, apically tapering. Podomere 1 rectangular, as long as wide, with moderately long setae. Podomere 2 with a single, large triangular membranous lobe at base of immovable finger. Immovable finger wide, straight, slightly wider anteriorly and apex tapering towards movable finger in a small process. Process with sclerotized round spots in anterior view. Single large oval membranous spot visible in posterior view. Surface of finger glabrous except for margins. Podomere 3 circa 3 times longer than wide. Membranous ledge with a single spine, Posterior side with a row of 7 small crenulated teeth. Glabrous except for several long setae clustered at lower inner margin. Podomere 4 short, apically tapering, slightly curved towards immovable finger, ca. 2.5 times longer than wide. Membranous ledge and 2 spines present mesal margin. Glabrous.

Distribution

Only known from the area near the Than To Waterfall in the very south of Thailand (Fig. 2A).