Orphnaecus libmanan Acuña & Guevarra, 2025

Acuña, Darrell C., Ragasa, Lorenz Rhuel P., Santiago-Bautista, Myla R., von Wirth, Volker & Guevarra Jr, Leonardo A., 2025, Revisiting and rediscovering the tarantulas (Araneae, Theraphosidae) of Culapnitan (Libmanan) Caves in the Philippines: troglomorphism, taxonomy, phylogeny and ecological niche, Subterranean Biology 52, pp. 143-186 : 143-186

publication ID	https://doi.org/10.3897/subtbiol.52.142334
publication LSID	lsid:zoobank.org:pub:C990F793-3677-4A43-AE8E-F8CB7552B138
DOI	https://doi.org/10.5281/zenodo.15604099
persistent identifier	https://treatment.plazi.org/id/CDA18664-36CB-5E36-8862-4859A7BC6AAF
treatment provided by	Subterranean Biology by Pensoft
scientific name	Orphnaecus libmanan Acuña & Guevarra
status	sp. nov.

Treatment

Orphnaecus libmanan Acuña & Guevarra sp. nov.

Figs 5 View Figure 5 , 6 View Figure 6 , 7 View Figure 7 , 8 View Figure 8

Orphnaecus sp. “L 3” Acuña et al., 2025.

Type material.

Holotype • ♂ PNM 18867 View Materials UST-ARC 0133 , field # CSL 02-04 , Paratype • ♀ UST-ARC 0132 (field # CSL 02 -03); Philippines: Luzon Island, Bicol Peninsula, Camarines Sur Prov., Libmanan, Brgy. Sigamot, Libmanan Caves National Park; burrows under and inside rotten logs on forest slope near Kalangkawan Cave , 20 Jul 2023, LA Guevarra, DC Acuña, JD Fornillos leg. Paratypes • ♂ ♀, UST-ARC 0130 –0131 (field # CSL 02 -01 – 02); [same locality and natural history data as for holotype]; 20 Apr 2023, LA Guevarra, DC Acuña, CN Noriega, JD Fornillos leg. Paratype • ♀ PNM 18868 View Materials UST-ARC 0134 . field # CSL 04 -01; [same general locality as for holotype], Brgy. Malinao, Sitio Guimbal , burrow under limestone rock; 20 Apr 2023, LA Guevarra, DC Acuña, CN Noriega, JD Fornillos leg. Paratypes • 3 ♂♂ 3 ♀♀, UST-ARC 0135 –0140 (field # CSL 04 -02 – 07); [same locality data as for the latter], 20 Jul 2023, burrows under piles of coconut husks; LA Guevarra, DC Acuña, JD Fornillos leg. ( DCA examined) .

Type gene sequence.

GenBank accessions: PP 778307 – PP 778312 (paratypes).

Diagnosis.

O. libmanan sp. nov. belongs to the genus Orphnaecus for having reniform lyrate morphology with a row of club-shaped stridulatory setae (Figs 5 G, H, I View Figure 5 , 7 H View Figure 7 ), palpal organ with embolus having basal lobe and PS keel from tip to base (Fig. 6 B – F View Figure 6 ), presence of palpal scale brush on patellae in males (Fig. 6 A View Figure 6 ). Females of O. libmanan sp. nov. differ from those of O. kwebaburdeos , O. pellitus , and O. tangcongvaca sp. nov. in having a relatively narrower apex than the base of the spermathecal lobe (SI ~ 44, n = 6; SI> 55 in the mentioned congeners) (Fig. 8 C View Figure 8 ), in having a greater number of mesoventral denticles with> 100 (n = 6) (<60 in mentioned congeners), and in having relatively longer tarsus I than IV (TI ~ 118, n = 6; T <112 in mentioned congeners). The females further differed from O. kwebaburdeos and O. tangcongvaca sp. nov. in having relatively shorter tibia I than IV (TBI ~ 90, n = 6; TBI> 104 in the mentioned congeners). The females also differed from O. kwebaburdeos in having a relatively shorter leg I than IV (RF ~ 95, n = 6; slightly longer leg I than IV in O. kwebaburdeos females, RF ~ 101). Mature males of O. libmanan sp. nov. differ from mature males of O. adamsoni , O. kwebaburdeos , and O. pellitus in having a relatively shorter embolus than the tegulum (EMI ~ 112, n = 5; EMI> 120 in the mentioned congeners) and longer leg I than IV (RF ~ 102, n = 5; shorter leg I than IV in the mentioned congeners, RF ~ 99). The mature males further differed from O. adamsoni and O. kwebaburdeos in having relatively longer tarsus I than IV (TI ~ 108, n = 5; shorter tarsus I than tarsus IV in the mentioned congeners, TI <93). O. libmanan sp. nov. also differs from O. pellitus and O. tangcongvaca sp. nov. in that it does not exhibit troglomorphism and dwarfism, respectively.

Remarks.

The female of O. adamsoni Salamanes et al., 2022 was not distinguished from O. libmanan sp. nov. and all known Orphnaecus species because the paratype female is misidentified and misplaced in Orphnaecus . The allotype / paratype ♀ ( PNM 14888) used in the original description of the female ( Salamanes et al. 2022) is also misplaced in Orphnaecus . Rather, it belongs to Ornithoctoninae because of the presence of a plumose setal field on retrolateral chelicerae, rows of thorn stridulatory setae on the prolateral maxilla, conspicuous white bands on leg segments, and stripe patterns on the dorsal abdomen, which are characteristics absent in Selenocosmiinae but synapomorphic to Ornithoctoninae. This specimen probably represents an undescribed Melognathus species, but a new taxon cannot be assigned to this specimen owing to its poor condition. Other paratype females could potentially be available to the species authors’ institution, but no response has been received to date from our multiple enquiries sent to the first author.

Description holotype male.

PNM 18867 UST-ARC 0122 , field # CSL 02-04, body length 36.02. (Figs 5 View Figure 5 , 6 View Figure 6 ).

Prosoma. Carapace (Fig. 6 A View Figure 6 ): CL 14.45, CW 12.52, CH 4.72, CR 10.05 long, lateral profile low and flat, and integument matte black. Fovea (Fig. 6 A View Figure 6 ): width 1.55, curvature at 143 °, procurved. Ocular Tubercle: 1.99 long, 2.6 wide. Eyes (Fig. 6 C View Figure 6 ): AME round, ALE, PME, and PLE ovoid, clypeus almost absent. AE row almost straight at 176 °, PE row recurved at 139 °. Eye diameters, AME 0.64, ALE 0.67, PME 0.52, PLE 0.56. Interocular distances, AME – AME 0.21, ALE – ALE 1.72, PME – PME 1.31, PLE – PLE 1.87, AME – ALE 0.2, AME – PME 0.13, AME – PLE 0.48, ALE – PLE 0.23, ALE – PME 0.31, PME – PLE 0.07. Chelicerae (Fig. 6 D – F View Figure 6 ): length 8.32, width 5.20, fang curve length 6.28, teeth 10, mesoventral denticles ~ 40. Cheliceral strikers (Fig. 6 F View Figure 6 ): primary rows, ~ 13, 0.68–1.07 long, dark long spiniform with filiform ends. Secondary rows, ~ 30, 0.29–0.73 long, dark short spiniform with filiform ends. Tertiary rows, ~ 83, 0.20–0.75 long, pallid tiny needleform. Pseudostrikers, pallid and present ventrally. Maxillae (Fig. 6 G View Figure 6 ): prolateral maxilla 5.23 long, 3.74 wide laterally, 3.46 wide ventrally. Maxilla prolaterally planoconvex, anterior lobe well pronounced. Maxillary cuspules ~ 272. Lyra (Fig. 6 G, F View Figure 6 ): lyrate patch 2.33 long, 1.40 high, with a total of ~ 366 stridulatory setae, in 10 or 11 rows, surrounded by fine setae, denser above and distally. Short pointed stridulatory setae (Fig. 6 J, K View Figure 6 ) ~ 361, 0.12–0.41 long, forming reniform patch, proximally broad. The largest stridulatory setae nine (Fig. 6 H, I View Figure 6 ), 0.60–0.92 long, situated at the lowest row medially, with the median three are larger and with weakly pointed and well-defined paddle blades, and with stout shaft laterally. Labium: 2.10 long, 2.77 wide, integument reddish brown, anterior 1 / 3 with cuspules ~ 514. Sternum (Fig. 6 B View Figure 6 ): 7.47 long, 6.83 wide. Sternal corners mildly acuminate, posterior corner acuminate. Labiosternal sigilla 1.20 long, 0.50 wide, 0.40 apart. Sternal sigilla 3 pairs, anterior sigilla 0.33 long, 0.23 wide, 4.47 apart, and 0.40 away from sternal margin adjacent to coxa I, median sigilla 0.93 long, 0.30 wide, 3.57 apart, and 0.63 away from sternal margin adjacent to coxa II, posterior sigilla 1.40 long, 0.53 wide, 1.60 apart, and 1.27 away from sternal margin adjacent to coxa II.

Opisthosoma. Abdomen: 13.02 long, 3.97 wide, ovular elongated, integument pale brown. Spinnerets: PMS 2.00 long, 0.59 wide, PLS basal segment 3.15 long, 1.36 wide, median segment 2.05 long, 1.12 wide, apical segment 3.17 long, 0.83 wide.

Genitalia. Palpal organ (Fig. 7 View Figure 7 ): length almost 1 / 2 of palp tibia length (POI 46.32). Tegulum 1.96 long, globular, widest medially, prolaterally pronounced, subtegular projection (StR) weakly pronounced. Embolus length 2.19, basal width 0.69, median width 0.21, tip 0.13 wide. Embolus length ~ 1.12 times longer than tegulum length (EMI 111.74), base broad, tapering distally, and curved retrolaterally. Embolus has a long prolateral superior keel (PS) from base to tip, broad basally and at the tip (Fig. 6 B – F View Figure 6 ); has short and stout prolateral inferior keel (PI), emerged from the tip to rear at around apical 1 / 4, located below PS and embolic opening (Op) (Fig. 6 F View Figure 6 ); apical keel (A) very short, emerged at the tip (Fig. 6 F View Figure 6 ); embolic opening (Op) located between PS and PI near the tip (Fig. 6 F View Figure 6 ). Basal lobe is pronounced and broad (Fig. 7 B – F View Figure 7 ).

Legs. Leg formula 1423. Leg lengths (fem. pat., tib., met., tar. / cym.): palp 26.12 (9.12, 4.84, 8.96, n / a, 3.20), leg I 49.44 (13.19, 7.11, 12.84, 9.73, 6.57), leg II 42.69 (11.94, 5.43, 10.87, 8.96, 5.49), leg III 36.72 (9.43, 4.36, 8.12, 9.08, 5.73), leg IV 48.42 (12.36, 5.43, 11.70, 12.84, 6.09). Leg widths (fem. pat., tib., met., tar. / cym.): palp (2.68, 2.48, 2.76, n / a, 3.24), leg I (3.52, 2.99, 2.51, 1.73, 1.19), leg II (3.22, 2.69, 2.21, 1.31, 1.13), leg III (2.93, 2.39, 1.97, 1.49, 1.19), leg IV (2.87, 2.69, 2.09, 1.31, 1.08). Tarsi III and IV with transverse weakening (cracked or bent), tarsi I and II with no visible weakening. Spines: Metatarsal spines (dorsal-ventral), met. I and II absent, met. III and IV 2, 3. Claws: all tarsal claws with 2 or 3 teeth, tarsus IV with unpaired inferior third claw.

Setation. Tactile setae (TS) — carapace entirely with rows of very short brownish-white TS (Fig. 6 A View Figure 6 ). Carapace margin, dorsal and upper 1 / 2 retrolateral surface of chelicerae, ventral prosoma, opisthosoma, and legs covered with dark and grayish brown, long and short TS, denser on abdomen and all ventral tibiae. Mesoprolateral surface of chelicerae with intercheliceral setae in arcuate strip of rows of setae basally spiniform and anteriorly filiform (Fig. 6 D View Figure 6 ). Above maxillary suture with rows of short spiniform setae, retrolateral surface smooth with vertical striation on distal 1 / 4 and with rows of fine pallid setae ventrolaterally, and proximal end of prolateral surface with sparse very short spiniform setae. Femoral setation, dark and needleform, intermixed with regular TS. Scales َ — carapace, basodorsal surface of chelicerae, coxae, trochantera, and femora dorsally with pale beige to pale brown cottony and wavy fine scales, proximally grayish-brown on dorsal femora (Fig. 6 A, B, E View Figure 6 ). Chelicerae, dorsal and upper retrolateral surface, dorsal maxilla, sternum, abdomen, dorsal PLS legs, covered with grayish-brown to grayish white lanceolate flat scales, which reflect purplish blue sheen, except on ventral abdomen and prolateral femora. Palpal scale brush, grayish white, present on patella and tibia, dorsally, very long and dense on patellae (Fig. 6 A View Figure 6 ). Trichobothria — clavate trichobothria present on all leg tarsi and cymbium, intermixed with epitrichobothria. Epitrichobothria clusters were present on all metatarsi, tarsi, and tibiae. Filiform trichobothria were sparsely present on all dorsal legs. Chemosensory sensilla — present sparsely all over the body and legs except on the carapace and chelicerae, dense on the scopulae field. Scopulae: cymbium entire; tar. I – III entire, undivided but intermixed with one or two rows of short stiff setae; tar. IV, entire, divided by four or five rows of long stiff setae; met. I – III, almost entire, undivided but sparsely intermixed with long TS; met. IV, covering 3 / 4, divided by two or three rows of long setae.

Color. Bicolored: the legs and opisthosoma are dark, while the carapace, coxae, and trochantera are pale brown to pale beige dorsally. The microstructures of the scales on the legs and abdomen reflect a purplish-blue sheen, and the scales on the carapace reflect a pinkish sheen (Fig. 6 A View Figure 6 ). The integument of the carapace is matte black. As the exoskeleton aged, the specimen became entirely dark brown before ecdysis.

Indices. CI 86.64, CHI 32.66, CRI 69.55, EI (AME) 4.43, EI (ALE) 4.64, RF 102.11, LI 118.92, TBI 109.74, TI 107.88, EMI 111.74, POI 46.32.

Description paratype female.

PNM 18868 UST-ARC 0134 , field # CSL 04-01, body length 40.36. (Figs 8 View Figure 8 , 9 View Figure 9 )

Prosoma. Carapace (Fig. 8 A View Figure 8 ): CL 16.30, CW 13.05, CH 4.84, CR 11.25 long, lateral profile low and flat, and integument reddish brown. Fovea (Fig. 8 A View Figure 8 ): 2.12 wide, curvature 134 °, procurved. Ocular tubercle (Fig. 8 C View Figure 8 ): 2.04 long, 2.8 wide. Eyes (Fig. 8 C View Figure 8 ): AME round, while ALE, PME, and PLE ovoid, clypeus almost absent. AE row slightly procurved at 165 °, and PE row recurved at 146 °. Eye diameters, AME 0.60, ALE 0.66, PME 0.55, PLE 0.52. Interocular distances, AME - AME 0.34, ALE - ALE 1.77, PME - PME 1.42, PLE - PLE 2.11, AME - ALE 0.24, AME - PME 0.14, AME - PLE 0.61, ALE - PLE 0.29, ALE - PME 0.29, PME - PLE 0.07. Chelicerae (Fig. 8 D – G View Figure 8 ): length 9.16, width 6.8, fang curve length 7.96, teeth 14 (ten large, four small), mesoventral denticles dense ~ 122. Cheliceral strikers (Fig. 8 G View Figure 8 ): primary rows, ~ 9, 0.82–1.20 long, dark long spiniform with filiform ends. Secondary rows, ~ 46, 0.29–0.72 long, composed of dark long and short spiniform strikers, rows anteriorly with filiform ends. Tertiary rows, ~ 65, 0.22–0.62 long, pallid tiny needleform setae. Pseudostrikers, pallid and present ventrally. Maxillae (Fig. 8 H View Figure 8 ): 6.48 long, 4.40 wide laterally, 3.40 wide ventrally. Maxilla prolaterally planoconvex, anterior lobe well pronounced, maxillary cuspules ~ 337. Lyra: lyrate patch, 2.56 long, 1.36 high, total stridulatory setae ~ 390, surrounded by very fine setae, denser above and distally. Short stridulatory setae ~ 375, forming reniform patch. Largest stridulatory setae 10, situated at the lowest row medially, with the median three are larger and club-shaped with weakly pointed and well-defined paddle blades, and with stout shaft laterally. Labium (Fig. 8 B View Figure 8 ): 2.48 long, 3.28 wide, integument reddish brown, and anterior 1 / 3 with cuspules ~ 728. Sternum (Fig. 8 B View Figure 8 ): 7.88 long, 6.68 wide, sternal corners mildly acuminate, and posterior corner acuminate. Labiosternal sigilla 1.35 long, 0.50 wide, 0.49 apart. Sternal sigilla three pairs, anterior sigilla 0.44 long, 0.24 wide, 4.40 apart, and 0.27 away from sternal margin adjacent to coxa I, median sigilla 0.79 long, 0. 32 wide, 4.13 apart, and 0.63 away from sternal margin adjacent to coxa II, posterior sigilla 1.31 long, 0.57 wide, 1.70 apart, and 1.33 away from sternal margin adjacent to coxa III.

Opisthosoma. Abdomen (Fig. 9 A View Figure 9 ): 14.87 long, 8.30 wide. ovular elongated, integument pale brown. Spinnerets (Fig. 9 A View Figure 9 ): PMS 2.21 long, 0.91 wide, PLS basal segment 3.17 long, 1.65 wide, median segment 1.87 long, 1.33 wide, and apical segment 2.99 long, 1.09 wide.

Genitalia. Spermathecae (Fig. 8 C View Figure 8 ): receptacle 1.40 long, 1.22 wide basally, 0.54 wide distally, lobes 0.31 apart at base. Receptacles unilobed, long, distally converging, apex very narrow, broad basally, apically slightly pointing inward, mesoprolaterally concave, and sclerotized entire.

Legs. Leg formula 4123. Leg lengths total (fem., pat., tib., met., tar.): palp 28.55 (10.55, 5.37, 6.73, n / a, 5.90), leg I 46.34 (13.41, 8.34, 9.76, 8.28, 6.55), leg II 40.23 (11.39, 6.80, 8.82, 8.14, 5.08), leg III 36.49 (9.84, 6.17, 6.80, 8.11, 5.57), leg IV 48.82 (13.56, 6.90, 10.84, 11.95, 5.57). Leg widths (fem., pat., tib., met., tar.): palp (3.32, 2.64, 2.72, n / a, 2.12), leg I (4.08, 3.52, 3.04, 2.20, 2.28), leg II (3.80, 3.00, 2.76, 1.92, 2.00), leg III (3.64, 3.12, 2.80, 2.00, 1.84), leg IV (3.84, 3.32, 3.00, 2.04, 1.88). Tarsi III and IV with transverse weakening (crack or bent), tarsi I and II with no obvious weakening. Spines: Metatarsal spines (dorsal-ventral), met. I 0–1, met. II 0–3, met. III 2–5 and met. IV 2, 3. Claws: palp with 1 claw, tarsi I – III with pair of claws, tarsus IV with unpaired inferior third claw, all claws have two or three teeth.

Setation. Tactile setae (TS) — carapace entirely with rows of very short yellowish-white TS. Carapace margin, dorsal and upper 1 / 2 retrolateral surface of chelicerae, ventral prosoma, opisthosoma and legs covered with dark and pale brown, long and short thick TS, longer on leg III, leg IV and abdomen. Mesoprolateral surface of chelicerae with intercheliceral setae in arcuate strip of rows of setae basally spiniform and anteriorly filiform. Above maxillary suture with rows of short spiniform setae, retrolateral surface smooth with vertical striation on distal 1 / 4 and with rows of fine pallid setae ventrolaterally, and proximal end of prolateral surface with sparse very short spiniform setae. Femoral setation, dense, dark and needleform TS. Scales َ (SC) — carapace, coxae, trochantera, and femora dorsally with white to pale brown cottony and wavy fine scales, grayish-brown on femora. Chelicerae, dorsal and upper retrolateral surface, dorsal maxilla, sternum, abdomen, dorsal PLS legs, covered with grayish-brown to grayish white lanceolate flat scales, which reflect purplish blue sheen (Fig. 8 B View Figure 8 ), except on ventral abdomen and prolateral femora. Trichobothria — clavate trichobothria present on all leg tarsi, intermixed with epitrichobothria. Clusters of epitrichobothria are present on all tarsi, metatarsi, and tibiae. Filiform trichobothria are present on all dorsal legs, sparsely. Chemosensory sensilla — long and short, pallid and tapering distally, present singly on the entire body except the carapace and chelicerae. Scopulae — palp tar. to tar. III entire, undivided but sparsely intermixed with one or two rows of short stiff setae, one to three rows on tar. III, and tar. IV, entire, divided by four or five rows of long stiff setae; met. I – III, almost entire, undivided but sparsely intermixed with long TS, less sparse on met. III, and met. IV, covering 3 / 4, divided by two or three rows of long setae and intermixed with long TS.

Color. Bicolored: the legs and opisthosoma are dark, while the carapace, coxae, and trochantera are brown to pale brown dorsally. The microstructures of scales on the legs and abdomen reflect a deep purplish-blue sheen (Fig. 8 B View Figure 8 ). The integument of the carapace is reddish brown. As the exoskeleton aged, the specimen became entirely dark brown before ecdysis.

Indices. CI 80.06, CHI 29.69, CRI 69.02, EI (AME) 3.68, EI (ALE) 4.05, RF 94.92, LI 107.39, TBI 90.04, TI 117.59, SI 44.26.

Etymology.

The specific epithet is a noun in apposition, named after the type locality, the Municipality of Libmanan in the Province of Camarines Sur, Philippines.