Aphilodon acutus

(Figs 5 – 6) Types. Holotype: ♀, from Parque Nacional de Itatiaia, Itatiaia, Rio de Janeiro, Brazil, 03 – 17 / 12 / 2017, V. Calvanese & A. Silva leg., deposited in IBSP 6451. Paratypes: 2 ♀ (IBSP 6453) and 2 ♂ (IBSP 6452), same data as holotype.

Description of holotype. Female (IBSP 6451). General aspect: 63 leg-bearing segments; body 18 long, maximum width (middle part of trunk) 0.4. Color (preserved specimen in alcohol): head and forcipular segment ferruginous, leg-bearing segments and post-pedal segments pale yellow (Fig. 6 A – G). Cephalic plate: longer than wide, 0.37 long, 0.3 wide (length / width ratio 1.2), without transverse suture, with setae mainly in three rows: anterior, medial and posterior (Fig. 6 B). Antennae: left antenna 0.93 long (2.5 times as long as cephalic plate); length / width ratio of articles II – XIII 0.6 – 1; length / width ratio of last article 1.9. Last article with ca. 13 claviform specialized setae on the external margin and ca. 10 on the internal margin. Morphology and chaetotaxy as in Fig. 6 B – C. Clypeus: 3 + 3 lateral setae; 2 + 2 post-antennal setae; 6 + 6 subclypeal setae. Mandible: pectinate lamellae with ca. 25 denticles. First maxillae: left telopodite length 0.036, width 0.033; distal article with 1 subapical sensillum; each medial projection of coxosternite with 3 subapical sensilla (Fig. 5 A). Second maxillae: 10 little setae distributed in a row along the anterior margin between the telopodites; coxosternite shortened in the middle part (middle 0.32 times as long as lateral margins), maximum length / maximum width ratio 0.7; left telopodite length 0.06 (1.6 times as long as the telopodite of first maxillae), maximum width (basal margin) 0.024; right telopodite with one apical sensillum and two subapical setae on article 3, left telopodite with one apical sensillum and one subapical seta on article 3 (Fig. 5 A). Forcipular segment: metatergite sub trapezoidal, length 0.13 (0.35 times as long as cephalic plate), width 0.35 (length / width ratio 0.37), with 12 scattered setae; coxosternite length 0.28, width 0.38 (length / width ratio 0.73); telopodites length 0.25, not reaching the anterior margin of the cephalic plate, trochanteroprefemur + femur with 2 denticles, tibia with 1 denticle, all relatively large; denticle distal of trochanteroprefemur with 1 apical seta, denticle corresponding to the vestigial femur bilobed, with 2 apical and 1 subapical setae, denticle of tibia bilobed, with 3 setae; tarsungulum 0.9 as long as trochanteroprefemur + femur, with a large denticle (Figs 5 B, 6 B – C). Tergites from the first to penultimate leg-bearing segment: metatergites rectangular, with two rows of 6 – 7 setae; in segment 50 metatergite length 0.15, width 0.4 (length / width ratio 0.37); in segment 50 pretergite 0.4 times as long as previous metatergite, with one row of 6 setae (Fig. 6 D). Walking legs: first leg 0.6 times as long as second leg, procoxae extended to the body midline; leg of segment 50 length 0.5 (Fig. 6 A – G). Sternites from the first to penultimate leg-bearing segment: first metasternite semicircular, the other metasternites rectangular or subquadratic, with scattered setae; in segment 50 metasternite length 0.18, width 0.16 (length / width ratio 1.1); presternite tiny throughout body, not visible in some segments (Fig. 6 C, E). Ultimate leg-bearing segment: metasternite wider than long, trapezoidal, length 0.1, maximum width 0.17 (length / width ratio 0.6); presternite not evident (Figs 5 C, 6 G). Ultimate legs straight, length 0.9 (1.8 times as long as penultimate leg); each coxopleuron with ca. 12 coxal pores, most part opening close to the membrane between the coxopleuron and the metasternite, but some pores are scattered; tarsus 1.5 times as long as tibia (Figs 5 C, 6 G). Postpedal segments: gonopods with 4 + 4 distal setae. Sexual dimorphism. Males with ultimate legs thickened (Fig. 6 F), gonopods biarticulated, article 1 with 2 – 3 setae, article 2 with 3 – 4 scattered setae. Variation. N = 9, including 7 ♀ and 2 ♂ (from a single locality): total body length: 18 – 22 mm. Leg-bearing segments: ♀ 63, 65; ♂ 61, 63. Coxal pores in each coxopleuron: 8 – 12. Natural history. The specimens were sampled at about 2 – 5 cm deep, in the humus or under logs or rocks, in the high and low part of the Parque Nacional de Itatiaia.

Diagnosis. Aphilodon acutus n. sp. resembles A. micronyx and A. rectitibia n. sp. by having the coxosternite of the second maxillae distinctly shortened in the middle part (Fig. 5 A). Aphilodon acutus n. sp. differ from the other two species by having the cephalic plate longer than wide and without visible transverse suture (Fig. 6 B) (the other two species have a cephalic plate wider than long and with a visible transverse suture), and the denticle of tarsungulum is remarkably large (Figs 5 B, 6 C) (relatively short in A. micronyx and A. rectitibia n. sp.).

Distribution. Brazil, state of Rio de Janeiro (Fig. 13).

Etymology. The specific epithet “ acutus ” means “ sharp ” in Latin, and refers to the large and sharpened denticle of tarsungulum, characteristic of this species.

Other material examined. 4 ♀ (IBSP 6454), same data as types.