Abstract

The Nemesiidae are the second most speciose family of Mygalomorphae, comprising 374 species in 44 genera (Platnick 2014Platnick NI (2014) The world spider catalog. The American Museum of Natural History, version 15.0, available online at: http://research.amnh.org/iz/spiders/catalog [Accessed: 27/IX/2014] doi: 10.5531/db.iz.0001
http://research.amnh.org/iz/spiders/cata... ). The Nemesiidae include medium sized spiders, for example Prorachias bristowei Mello-Leitão, 1924 (length 38.7 mm) and Lycinus caldera Goloboff, 1995 (35.9 mm), and small ones, e.g., Hermacha anomala (Bertkau, 1880) (8.6 mm) and Flamencopsis minima Goloboff, 1995 (10.7 mm) (Bertkau 1880Bertkau P (1880) Verzeichniss der von Prof. Ed. van Beneden auf seiner im Auftrage der Belgischen Regierung unternommen wissenschaftlichen Reise nach Brasilien und La Plata im Jahren 1872-73 gensammelten Arachniden. Mémoires Couronnes de la Academie Royale des Sciences, Lettres et Beaux-Arts de Belgique 43: 1-120., Goloboff 1995Goloboff PA (1995) A revision of the South American spiders of the family Nemesiidae (Araneae, Mygalomorphae). Part I: species from Peru, Chile, Argentina, and Uruguay. Bulletin of the American Museum of Natural History 224: 1-189., Lucas et al. 2005Lucas SM, Indicatti RP, Fukami CY (2005) Redescrição de Prorachias bristowei Mello-Leitão 1924 (Araneae, Mygalomorphae, Nemesiidae). Biota Neotropica 5(1a): 1-6. doi: 10.1590/S1676-06032005000200019
https://doi.org/10.1590/S1676-0603200500... ). The Nemesiidae are distributed world-wide and are divided into six subfamilies (Raven 1985Raven RJ (1985) The spider infraorder Mygalomorphae (Araneae): Cladistics and systematics. Bulletin of The American Museum of Natural History 182: 1-180.). Of these, four occur in the Neotropical region: Anaminae, with three genera: Acanthogonatus Karsch, 1880, Longistylus Indicatti & Lucas, 2005 and Hermacha Simon, 1889; Diplothelopsinae, with five genera: Chaco Tullgren, 1905, Chilelopsis Goloboff, 1995, Diplothelopsis Tullgren, 1905, Flamencopsis Goloboff, 1995 and Lycinus Thorell, 1894; Nemesiinae with one genera: Mexentypesa Raven, 1987; and Pycnothelinae with nine genera: Bayana Pérez-Miles et al., 2014, Hermachura Mello-Leitão, 1923, Neostothis Vellard, 1925, Prorachias Mello-Leitão, 1924, Psalistopoides Mello-Leitão, 1934, Pselligmus Simon, 1892, Pycnothele Chamberlin, 1917, Rachias Simon, 1892 and Stenoterommata Holmberg, 1881 (Raven 1985Raven RJ (1985) The spider infraorder Mygalomorphae (Araneae): Cladistics and systematics. Bulletin of The American Museum of Natural History 182: 1-180., 1987Raven RJ (1987) A new mygalomorph spider genus from Mexico (Nemesiinae, Nemesiidae, Arachnida). Jounal of Arachnology 14: 357-362., Goloboff 1995Goloboff PA (1995) A revision of the South American spiders of the family Nemesiidae (Araneae, Mygalomorphae). Part I: species from Peru, Chile, Argentina, and Uruguay. Bulletin of the American Museum of Natural History 224: 1-189., Indicatti & Lucas 2005Indicatti RP, Lucas SM (2005) Description of a new genus of Nemesiidae (Araneae, Mygalomorphae) from the Brazilian Cerrado. Zootaxa 1088: 11-16., Lucas & Indicatti 2006Lucas SM, Indicatti RP (2006) On the genus Psalistopoides Mello-Leitão (Araneae, Mygalomorphae, Nemesiidae). Revista Brasileira de Zoologia 23(2): 547-549. doi: 10.1590/S0101-81752006000200030
https://doi.org/10.1590/S0101-8175200600... , Lucas et al. 2008Lucas SM, Passanha V, Janini CRV, Indicatti RP (2008) On the genus Neostothis Vellard (Araneae, Nemesiidae). Jounal of Arachnology 36: 472-475. doi: 10.1636/CA07-107.1
https://doi.org/10.1636/CA07-107.1... , Passanha et al. 2014Passanha V, Indicatti RP, Brescovit AD, Lucas SM (2014) Revision of the spider genus Pycnothele Chamberlin, 1917 (Araneae, Nemesiidae). Iheringia 104(2): 228-251. doi: 10.1590/1678-476620141042228251
https://doi.org/10.1590/1678-47662014104... , Pérez-Miles et al. 2014Pérez-Miles F, Costa FG, Oca LM (2014) Bayana labordai, new genus and species of Nemesiidae (Araneae: Mygalomorphae) from Northern Uruguay and Southern Brazil. Journal of Natural History 48: 1937-1946. doi: 10.1080/00222933.2014.908970
https://doi.org/10.1080/00222933.2014.90... ). In this study we deal with species that belong to Acanthogonatus and Chaco.

Acanthogonatus was established by Karsch (1880), with the type species, A. francki Karsch, 1880, based on a female from Chile. The genus currently includes 28 species, distributed mostly in the Occidental portion of South America, mainly in Chile and Argentina, and includes 25 species (Goloboff 1995Goloboff PA (1995) A revision of the South American spiders of the family Nemesiidae (Araneae, Mygalomorphae). Part I: species from Peru, Chile, Argentina, and Uruguay. Bulletin of the American Museum of Natural History 224: 1-189.). In the Oriental portion, only A. ericae Indicatti et al., 2008 and A. tacuariensis (Pérez-Miles & Capocasale, 1982) are recorded, both in southern Brazil and the second also in Uruguay (Pérez-Miles & Capocasale 1982Pérez-Miles F, Capocasale RM (1982) Arañas del Uruguay, IV. Hallazgo de una tercera especie del genero Pycnothelopsis: Pycnothelopsis tacuariensis sp. nov. (Araneae, Pycnothelidae). Comunicaciones Zoologicas del Museo de Historia Natural de Montevideo 147: 1-7., Goloboff 1995Goloboff PA (1995) A revision of the South American spiders of the family Nemesiidae (Araneae, Mygalomorphae). Part I: species from Peru, Chile, Argentina, and Uruguay. Bulletin of the American Museum of Natural History 224: 1-189., Indicatti et al. 2008Indicatti RP, Lucas SM, Ott R, Brescovit AD (2008) Litter dwelling mygalomorph spiders (Araneae: Microstigmatidae, Nemesi idae) from Araucaria forests in Southern Brazil, with the description of five new species. Revista Brasileira de Zoologia 25: 529-546. doi: 10.1590/S0101-81752008000300021
https://doi.org/10.1590/S0101-8175200800... ).

Chaco was established by Tullgren (1905Tullgren A (1905) Aranedia from the Swedish expedition through the Gran Chaco and the Cordilleras. Arkiv for Zoologi 2(19): 1-81.), with the type species, C. obscura Tullgren, 1905, based on a male from Salta, Argentina. The genus currently includes 11 species, six from Argentina, two from Chile, two from Uruguay and one from Brazil (Goloboff 1995Goloboff PA (1995) A revision of the South American spiders of the family Nemesiidae (Araneae, Mygalomorphae). Part I: species from Peru, Chile, Argentina, and Uruguay. Bulletin of the American Museum of Natural History 224: 1-189., Montes de Oca & Pérez-Miles 2013Montes de Oca L, Pérez-Miles F (2013) Two new species of Chaco Tullgren from the Atlantic coast of Uruguay (Araneae, Mygalomorphae, Nemesiidae). ZooKeys 337: 73-87. doi: 10.3897/zookeys.337.5779
https://doi.org/10.3897/zookeys.337.5779... , Ferretti 2014Ferretti N (2014) Chaco ansilta new species from Mendoza province, Western Argentina (Araneae: Nemesiidae). Anais da Academia Brasileira de Ciências 2014: 1-12. doi: 10.1095/0001-3765201420140226
https://doi.org/10.1095/0001-37652014201... ).

In an inventory using Winkler extractors in leaf litter in the Reserva Biológica do Tinguá, Rio de Janeiro, Brazil, representatives of two new Nemesiidae species were collected and are herein described: Acanthogonatus minimussp. nov. and Chaco tinguasp. nov. In addition, data on the phenology of C. tinguasp. nov. is provided.

MATERIAL AND METHODS

The material examined is deposited in the following institutions (abbreviation and curator in parentheses): Instituto Butantan, São Paulo (IBSP, A.D. Brescovit), Museu Nacional do Rio de Janeiro, Rio de Janeiro (MNRJ, A.B. Kury), Museu de Zoologia da Universidade de São Paulo, São Paulo (MZSP, R. Pinto da Rocha), and Museu de Ciências Naturais, Fundação Zoobotânica do Rio Grande do Sul, Porto Alegre (MCN, R. Ott). The format of the descriptions follows Lucas & Indicatti (2010Lucas SM, Indicatti RP (2010) Description of two new species of Lycinus (Araneae: Nemesiidae). Zoologia 27(3): 425-430. doi: 10.1590/51984-46702010000300015
https://doi.org/10.1590/51984-4670201000... ). The terminology for general structures follows Goloboff (1995Goloboff PA (1995) A revision of the South American spiders of the family Nemesiidae (Araneae, Mygalomorphae). Part I: species from Peru, Chile, Argentina, and Uruguay. Bulletin of the American Museum of Natural History 224: 1-189.). Spine notation follows Petrunkevitch (1925Petrunkevitch A (1925) Arachnida from Panamá. Transactions of the Connecticut Academy of Arts and Sciences 27: 51-248.). All measurements are in millimeters (mm) and were taken with a stereomicroscope equipped with a millimetric ocular lens. The lengths of leg segments were measured between joints, in dorsal view. Total body length includes the chelicerae but not the pedicel and spinnerets. Spermathecae were dissected and immersed in enzyme (Ultrazyme^(r)) during 72 hours for soft tissue digestion to allow observation of internal structures. The material for scanning electronic microscopy (SEM) was cleaned in an ultrasonic cleaner USC 700, Thornton Unique, for six minutes, and was gradually dehydrated through immersion in increasingly concentrated (from 80 to 100%) ethanol for approximately eight hours. After dehydration it was critical-point dried. All the material used in SEM was fixed to stubs with double-faced adhesive copper tape and sputter-coated with gold. Images were taken under high vacuum with a FEI Quanta 250 SEM at the Instituto Butantan. Pictures were taken with a Leica DFC500 digital camera mounted on a Leica MZ16A stereomicroscope, the extended focal range images were composed with Leica Application Suite version 2.5.0. Abbreviations: (AME) anterior median eyes, (ALE) anterior lateral eyes, (PLE) posterior lateral eyes, (PME) posterior median eyes, (PMS) posterior median spinnerets, (PLS) posterior lateral spinnerets, (STC) superior tarsal claws, (ITC) inferior tarsal claw; spines: (d) dorsal, (v) ventral, (p) prolateral, (r) retrolateral, (ap) apical, (VP) ventro-prolateral, (VR) ventro-retrolateral.

Ecological data were obtained at Reserva Biológica do Tinguá, located at Serra do Mar, municipality of Nova Iguaçu, state of Rio de Janeiro (southeastern Brazil). The Reserva has an area of 26,260 ha, and altitudinal gradient from 50-1600 m a.s.l. The climate there is classified as 'Cwb' in the Köppen system, temperate humid highland tropical (IBAMA 2006IBAMA (2006) Plano de Manejo da Reserva Biologica do Tinguá. Brasília, Ministério do Meio Ambiente, 102p. Available online at: http://www.icmbio.gov.br/portal/images/stories/imgs-unidades-coservacao/rebio_tingua.pdf. [Accessed: 27/VI/2014].
http://www.icmbio.gov.br/portal/images/s... ). This type of climate has a short, poorly defined dry season in July and August, averaging 20°C, and a rainy season in December, January and February averaging 27°C. The annual precipitation is 2,099.3 mm, with the wettest months in December and January (IBAMA 2006IBAMA (2006) Plano de Manejo da Reserva Biologica do Tinguá. Brasília, Ministério do Meio Ambiente, 102p. Available online at: http://www.icmbio.gov.br/portal/images/stories/imgs-unidades-coservacao/rebio_tingua.pdf. [Accessed: 27/VI/2014].
http://www.icmbio.gov.br/portal/images/s... ). The vegetation is classified as Dense Ombrophylous Forest (Atlantic Rainforest), with large structural variation due to its declivity (IBAMA 2006IBAMA (2006) Plano de Manejo da Reserva Biologica do Tinguá. Brasília, Ministério do Meio Ambiente, 102p. Available online at: http://www.icmbio.gov.br/portal/images/stories/imgs-unidades-coservacao/rebio_tingua.pdf. [Accessed: 27/VI/2014].
http://www.icmbio.gov.br/portal/images/s... ). The study location, known as Barrelão (22°34'28.9'S, 43°24'57.6'W), close to 400 m a.s.l. altitude is classified as Dense Ombrophylous Submontane Forest (Orsolon-Souza et al. 2011Orsolon-Souza G, Esbérard CEL, Mayhé-Nunes AJ, Vargas AB, Veiga-Ferreira S, Folly-Ramos E (2011) Comparison between Winkler's extractor and pitfall traps to estimate leaf litter ants richness (Formicidae) at a rainforest site in southest Brazil. Brazilian Journal of Biology 71(4): 873-880. doi: http://dx.doi.org/10.1590/S1519-69842011000500008
https://doi.org/10.1590/S1519-6984201100... : fig. 1 A-C).

Samples were collected in the middle of each of the four seasons of 2002: summer (February 02-04); autumn (May 15-17); winter (June 05-07); spring (October 20-22). During each field excursion 25 points were marked along a 1,200 m transect, and at each point we stretched two perpendicular, 25 m lines; one to the left and the other one to the right. At the end of each line we delimited a 1 m² plot, totaling 50 plots. Each sample refers to one square meter of leaf litter, which was removed and sieved in a 5 mm mesh and soon after placed into the Winkler extractor where it remained for 48 hours. This procedure was adapted from Delabie et al. (2000Delabie JHC, Agosti D, Nascimejnto IC (2000) Litter ant communities of the Brazilian Atlantic rain forest region, p. 1-17. In: Agosti D, Majer JD, Alonso LT, Schultz TR (Eds). Sampling ground-dwelling ants: case studies from the world's rain forests. Perth, Curtin University School of Environmental Biology, vol. 18.) and Orsolon-Souza et al. (2011Orsolon-Souza G, Esbérard CEL, Mayhé-Nunes AJ, Vargas AB, Veiga-Ferreira S, Folly-Ramos E (2011) Comparison between Winkler's extractor and pitfall traps to estimate leaf litter ants richness (Formicidae) at a rainforest site in southest Brazil. Brazilian Journal of Biology 71(4): 873-880. doi: http://dx.doi.org/10.1590/S1519-69842011000500008
https://doi.org/10.1590/S1519-6984201100... ). Since abundance data did not meet the assumptions of parametric tests, the Kruskal-Wallis (KW) non-parametric analysis of variance was used for detecting between-seasons differences in abundance of males, females and juveniles separately (Zar 1999Zar JH (1999) Biostatistical analysis. Upper Saddle River, Prentice-Hall, 4th, 912p.).

TAXONOMY

Nemesiidae Simon, 1889

Anaminae Simon, 1889

Acanthogonatus Karsch, 1880

Identification key for Acanthogonatus updated from Goloboff (1995Goloboff PA (1995) A revision of the South American spiders of the family Nemesiidae (Araneae, Mygalomorphae). Part I: species from Peru, Chile, Argentina, and Uruguay. Bulletin of the American Museum of Natural History 224: 1-189.)

Males

Male of A. alegre Goloboff, 1995, A. brunneus (Nicolet, 1849), A. incursus (Chamberlin, 1916), A. juncal Goloboff, 1995, A. mulchen Goloboff, 1995, A. parana Goloboff, 1995, A. peniasco Goloboff, 1995, A. tolhuaca Goloboff, 1995 and A. vilches Goloboff, 1995 are unknown.

Females

Female of A. birabeni, A. chilechico and A. patagallina are unknown.

Acanthogonatus minimus sp. nov. Figs. 1-30

Types. Male holotype from Brazil, Rio de Janeiro: Nova Iguaçu (Reserva Biológica do Tinguá, 22°34'28.9'S, 43°24'57.6'W, 400 m a.s.l.), 2002, E. Folly Ramos et al. coll. (IBSP 166089). Paratypes with the same data as holotype, female (IBSP 166090); one male (IBSP 166091); female (IBSP 166092); female (MNRJ 6803); female (MZSP 67296); female (MCN 52059).

Diagnosis. Acanthogonatus minimussp. nov. differs from remaining species of the genus by the male palpal bulb with very long and twisted embolus ca. of 2/3 length of palpal tibia (Figs. 1-4, 13) and spermatheca with long and twisted duct (Fig. 6), anterior eyes row recurved and T-shaped fovea (Figs. 7, 11).

Description. Male (holotype). Carapace dark yellow, with light pubescence, legs light yellow (Fig. 7). Abdomen dorsally light yellow with two groups of anterior stains, with brown chevron and ventrally light yellow, with light pubescence (Fig. 7). Total length 4.22. Carapace 1.85 long, 1.45 wide, with very short 0.10 and slightly procurved fovea. Abdomen 1.95 long, 1.10 wide. Thoracic region flat. Clypeus absent. Eye tubercle weakly elevated, wider than long (Fig. 7). Eye group trapezoidal. Anterior and posterior eye rows recurved (Fig. 7). Eye sizes: AME 0.10, ALE 0.14, PME 0.09 and PLE 0.12. Chelicerae with seven teeth in prolateral row, with ca. 20 basal smaller teeth (Figs. 9, 16) and rastellum weak, formed by thin setae (Figs. 8, 9, 16). Intercheliceral tumescence very small, pale yellow, covered by ca. nine thin, short, sparse setae (Figs. 9, 16, 17). Labium 0.14 long, 0.30 wide, with no cuspules (Fig. 8). Maxilla subquadrate with 18 blunt cuspules on internal basal angle (Figs. 8, 19, 20). Serrula poorly developed, with ca. 15 teeth (Fig. 18). Sternum slightly circular 1.04 long, 0.85 wide, slightly domed. Six sternal sigilla small, oval, very shallow, inconspicuous (Fig. 8). Palp: measurements: femur 0.85/patella 0.55/tibia 0.70/cymbium 0.40/total 2.50; spination: femur d0-1-1-1-1-0, tibia r0-0-0-1p-1p. Legs: measurements: I: femur 1.35/patella 0.80/tibia 1.00/metatarsus 0.90/tarsus 0.60/total 4.55; II: 1.05/0.75/0.75/0.70/0.50/3.75; III: 1.05/0.60/1.10/0.95/0.55/4.25; IV: 1.35/0.75/1.05/1.20/0.57/4.92; spination: I: femur d1-1-1-1-0, tibia v1r megaspine (Fig. 5), metatarsus v0-1r-0-2ap; II: femur d1-1-1-1, tibia v0-1-0, metatarsus v0-1r0-2ap; III: femur d1-1-1-2, patella p0-1-1, r0-1-0, tibia d0-0-1-0, v0-1r-0, p0-1-0, r0-1-0, metatarsus d1r-1p-0-2-0, v2-0-1r-1p-0-3ap, p0-1-0-1-0, r0-1-0-0; IV: femur d1-1-1-0, patella r0-1-0, tibia p0-1-0-1-0, rp0-1-0-1-0, metatarsus d2-1p-0-2, v1p-1p-0-3ap, p0-1-0-1-0, r0-1-0-0-0. Slightly thickened femora III (Fig. 7). Metatarsal preening combs: III: 4 VR, 5 VP; IV: 4 VR, 3 VP. Tarsi I-IV not flexible. Scopula on tarsi I-II and 1/4 of metatarsi I-II. Scopula on tarsi I-II undivided, very light (Fig. 24) and symmetric. Scopula on tarsi III-IV absent. STC large with double row of teeth. Teeth on tarsal claws: I-II: 13, 10, 10, 9; III: 5, 5, 4, 5; IV: 6, 4, 5, 6. ITC on all legs (Figs. 5, 24, 25). Trichobothria with rounded, broad, elevated base and 14-16 developed ridges (Figs. 22, 23). Tarsal organ rounded, slightly elevated with two concentric ridges (Fig. 21). Book-lung openings with long narrow slit. Four spinnerets, PLS: basal segment 0.35, median segment 0.45, apical segment domed 0.50 long (Figs. 7, 8, 10). PMS with articulate spigots (Figs. 10, 26) and PLS with sparse and enlarged pumpkiniform spigots along inner edge of spinning field and elsewhere covered with articulate spigots (Figs. 10, 27, 28). Cymbium with thin setae, resembling tarsal scopula setae (Figs. 29, 30). Palpal tibia short, narrow (Fig. 1) and with shallow ventral excavation. Palpal bulb almost piriform (Figs. 1-4) with rounded ridges (Figs. 13-15).

Female (paratype IBSP 112980). Coloration as in male (Figs. 11, 12). Total length 5.40. Carapace 2.35 long, 1.75 wide, with very short 0.22 and slightly procurved fovea. Abdomen 2.50 long, 1.55 wide. Thoracic region as in male. Clypeus absent (Fig. 11). Eye tubercle weakly elevated, wider than long. Eye group trapezoidal. Anterior and posterior eye rows recurved (Fig. 11). Eye sizes: AME 0.10, ALE 0.18, PME 0.10 and PLE 0.15. Chelicerae with nine teeth in prolateral row, with ca. 15 basal smaller teeth and rastellum weak, formed by thin setae. Labium 0.24 long, 0.56 wide, without cuspule. Maxilla subquadrate with 30 cuspules on internal basal angle. Serrula as in male. Sternum slightly oval 1.30 long, 1.10 wide. Six sternal sigilla small, oval, very shallow, inconspicuous (Fig. 12). Palp: measurements: femur 1.00/patella 0.60/tibia 0.70/tarsi 0.70/total 3.00; spination: femur d1-1-1-1-1, tibia v3ap. Legs: measurements: I: femur 1.50/patella 1.10/tibia 1.05/metatarsus 0.85/tarsus 0.60/total 5.10; II: 1.30/0.90/0.80/0.85/0.60/4.45; III: 1.15/0.75/0.70/1.00/0.65/4.25; IV: 1.45/0.90/1.15/1.40/0.70/5.60; spination: I: femur d1-1-1-1, metatarsus v0-1r-0-2ap; II: femur d1-1-1-1-1, metatarsus v0-2-0-3ap; III: femur d1-1-1-1-1, patella p0-0-1-1, r0-1-0, tibia d0-0-1, v0-1r-0-2ap, p0-1-0-1-0, r0-1-0, metatarsus d1r-2-0-0-2, v1r-0-2-0-3ap, p0-1-0-1-0; IV: femur d1-1-1-1, tibia v2ap, p0-1-0-1-0, r0-1-0-1-0 metatarsus d2-0-1r-0-2-0, v20-2-0-3ap, p0-1-0-1-0-0-1, r0-1-0-0. Slightly thickened femora III. Metatarsal preening combs: III: 4 VR, 3 VP; IV: 3 VR, 2 VP. Tarsi I-IV not flexible. Scopula on tarsi I-II undivided, very light and symmetric. Scopula on distal half of metatarsi I. Scopula on tarsi III-IV absent. STC large with double row of teeth. Teeth on tarsal claws: I-II: 10, 10, 10, 10; III: 6, 6, 5, 6; IV: 5, 5, 5, 5. ITC on all legs. Trichobothria and tarsal organ as in male. Book-lung openings as in male. Four spinnerets, PLS: basal segment 0.30, median segment 0.30, apical segment domed 0.55 long. Spigots as in male.

Variation. Males (n = 3): total length 4.22-4.40; carapace 1.85-1.90 long; maxillae with 15-18 cuspules. Females (n = 11): total length 4.00-5.40; carapace 1.80-2.35 long; maxillae with 25-30 cuspules.

Additional material examined. Brazil, Rio de Janeiro: Nova Iguaçu (Reserva Biológica do Tinguá, 22°34'28.9'S; 43°24'57.6'W, 400 m a.s.l.), 2002, E. Folly Ramos et al. coll., 1 female, 5 juveniles (IBSP 166093); male (IBSP utilized in SEM); 5 females (IBSP 166094-166098); 2 females (MNRJ 6804).

Distribution. Known only from the type locality.

Etymology. The specific name is a Latin adjective (= the smallest) referring to the small size of this species.

Figures 13-21.
Acanthogonatus minimussp. nov., male: (13-15) left palpal bulb, retro-ventral view: (14-15) detail of rounded ridges; (16-17) left chelicera, prolateral view: (17) detail of intercheliceral tumescence; (18) serrula on maxilla, dorsal view; (19-20) cuspules on maxilla: (20) detail of a cuspule, lateral view; (21) tarsal organ, leg IV, dorsal view.

Diplothelopsinae Schiapelli & Gerschman, 1967

Chaco Tullgren, 1905

Identification key for Chaco updated from Goloboff (1995)Goloboff PA (1995) A revision of the South American spiders of the family Nemesiidae (Araneae, Mygalomorphae). Part I: species from Peru, Chile, Argentina, and Uruguay. Bulletin of the American Museum of Natural History 224: 1-189. and Ferretti (2014)Ferretti N (2014) Chaco ansilta new species from Mendoza province, Western Argentina (Araneae: Nemesiidae). Anais da Academia Brasileira de Ciências 2014: 1-12. doi: 10.1095/0001-3765201420140226
https://doi.org/10.1095/0001-37652014201...

Males

Male of C. patagonica Goloboff, 1995 and C. tecka Goloboff, 1995 are unknown.

Females

Chaco tingua sp. nov. Figs. 31-62

Types. Male holotype from Brazil, Rio de Janeiro: Nova Iguaçu (Reserva Biológica do Tinguá, 22°34'28.9'S; 43°24'57.6'W, 400 m a.s.l.), 2002, E. Folly Ramos et al. leg. (IBSP 166099). Paratypes with the same data as holotype, female (IBSP 166100); female (IBSP 166101); male (IBSP 166102); male and female (MNRJ 6805); male and female (MZSP 67297); male and female (MCN 52060).

Diagnosis. Chaco tinguasp. nov. differs from remaining species of the genus by the retrolateral megaspine on tibia I (Figs. 35, 53), palpal embolus tip hook-shaped (Fig. 34), ITC on all legs, absence of pubescence on the carapace and legs (Figs. 38, 40).

Description. Male (holotype). Carapace brown, legs brownish yellow, with no pubescence (Fig. 38). Abdomen dorsally brown with one anterior stain and five median-posterior yellow bands and ventrally yellow, with light pubescence (Fig. 38). Total length 4.20. Carapace 2.00 long, 1.60 wide, with short 0.11 and procurved fovea (Fig. 38). Abdomen 1.90 long, 1.20 wide. Thoracic region slightly raised. Clypeus absent. Eye tubercle weakly elevated, wider than long (Fig. 38). Eye group trapezoidal. Anterior and posterior eye rows recurved (Fig. 38). Eye sizes: AME 0.16, ALE 0.16, PME 0.11 and PLE 0.10. Chelicerae with five teeth in prolateral row (Figs. 36, 49), with ca. 12 basal smaller teeth and strong rastellum, formed by four very thick short setae, without on raised mound (Figs. 36, 39, 49). Intercheliceral tumescence small, pale yellow, covered by ca. 10 thin, long, sparse setae (Figs. 36, 49, 50). Labium 0.08 long, 0.16 wide, with no cuspules (Fig. 39). Maxilla subquadrate with ca. 20 pointed and elongated cuspules on internal basal angle. Serrula very poorly developed, with ca. five teeth (Fig. 48). Sternum circular 0.48 long, 0.42 wide, domed. Six sternal sigilla small, oval, very shallow, inconspicuous (Fig. 39). Palp: measurements: femur 0.85/patella 0.45/tibia 0.55/cymbium 0.30/total 2.15; spination: femur d0-0-0-0-1-1, tibia r0-0-0-1p-0. Legs: measurements: I: femur 1.55/patella 0.90/tibia 1.15/metatarsus 0.90/tarsus 0.65/total 5.15; II: 1.35/0.85/0.90/1.00/0.65/4.75; III: 1.30/0.75/0.90/1.10/0.50/4.55; IV: 1.80/0.75/1.50/1.75/0.90/6.70; spination: I: femur d0-1-1-1, patella v1ap, tibia v1r-0-2-0-2-(1r megaspine, Figs. 35, 53), metatarsus v2ap; II: femur d0-1-1-1, patella 0, tibia v0-1r-0-2ap, p0-1-0-1-0, metatarsus v2ap; III: femur d0-1p-2-1r, patella p0-1-1-1, tibia d0-1-0, v2ap, p1-1-0, metatarsus d1r-1p-1r-1p-0-2, v3ap, p0-1-0-0; IV: femur d0-1-1-1-0, patella 0, tibia v3ap, p1-0-1-0, r0-1-0-1, metatarsus d1r-1r-0-1p-0-0-2, v0-0-1r-0-3ap, r1-0-1-0-0-0. Thickened femora III (Fig. 38). Group of ca. 10 thickened setae on apical prolatero-dorsal femur IV. Metatarsal preening combs absent. Tarsi I-IV not flexible (Figs. 35, 38-41, 51, 54). Scopula on tarsi I-II and 2/3 of metatarsi I-II (Figs. 35, 51). Scopula on tarsi I-II undivided, very light and symmetric. Scopula on tarsi III-IV absent (Figs. 38, 54). STC large with double row of teeth (Fig. 52). Teeth on tarsal claws: I and II: 7, 4, 4, 6; III: 6, 4, 4, 6; IV: 6, 4, 5, 6. ITC on all legs (Figs. 52, 55). Trichobothria with oval, broad, elevated base and 10-13 developed ridges (Figs. 51, 55, 57). Tarsal organ oval, slightly elevated with two concentric ridges (Fig. 56). Book-lung openings with long narrow slit. Four spinnerets, PLS: basal segment 0.10, median segment 0.11, apical segment domed 0.05 long (Figs. 39, 58). PMS with 3-4 articulate spigots only on apex. PLS covered with sparse articulate spigots, one enlarged on apex of medial article (Fig. 58). Cymbium with thin setae, resembling tarsal scopula setae (Figs. 45, 59). Palpal tibia short, wide (Fig. 31) and with lightly deep ventral excavation (Figs. 31, 45). Palpal tibia excavation and basal region of tegulum with grooves, evidencing a possible stridulatory apparatus (Fig. 45). Palpal bulb piriform with six keels and short and curved embolus (Figs. 32-34, 45-47).

Female (paratype IBSP 166100). Coloration as in male (Figs. 40-41). Total length 5.80. Carapace 2.50 long, 2.00 wide, with short 0.20 and procurved fovea (Fig. 40). Abdomen 2.65 long, 1.90 wide. Thoracic region as in male. Clypeus absent. Eye tubercle weakly elevated, wider than long (Fig. 40). Eye group trapezoidal. Anterior and posterior eye rows recurved (Fig. 40). Eye sizes: AME 0.11, ALE 0.16, PME 0.10 and PLE 0.11. Chelicerae with seven teeth in prolateral row, with ca. 12 basal smaller teeth and strong rastellum formed by five very thick short setae, without on raised mound (Figs. 41, 42, 60). Labium 0.5 long, 0.6 wide, without cuspule. Maxilla with 28 blunt cuspules on internal basal angle (Figs. 41, 42, 61). Serrula absent. Sternum slightly oval 1.5 long, 1.25 wide. Six sternal sigilla small, oval, very shallow, inconspicuous (Fig. 41). Palp: measurements: femur 1.00/patella 0.62/tibia 0.65/tarsi 0.6/total 2.87; spination: tibia v3ap. Legs: measurements: I: femur 1.25/patella 0.85/tibia 0.95/metatarsus 0.70/tarsus 0.55/total 4.3; II: 1.25/0.80/0.75/0.65/0.55/4.00; III: 1.25/0.80/0.80/0.80/0.6/4.25; IV: 1.75/1.00/1.25/1.40/0.80/6.2; spination: I: metatarsus v2ap; II: femur metatarsus v0-1-0-2ap; III: patella p0-1-1-1, tibia d0-1-0, p0-1-0-0, metatarsus d1r-2-1p-0-2, v3ap, p0-1-0-0; IV: tibia p0-1-0, metatarsus d1r-1p-0-2, v4ap, p0-1-0-0. Thickened femora III (Fig. 40). Group of ca. 10 thickened setae on apical prolatero-dorsal femur IV (Figs. 40, 43). Metatarsal preening combs absent. Tarsi I-IV not flexible (Fig. 41). Scopula on tarsi I-II undivided, very light and symmetric. Scopula on distal half of metatarsi I. Scopula on tarsi II-IV absent. STC large with double row of teeth (Fig. 62). Teeth on tarsal claws: I: 9, 5, 5, 9; II: 6, 5, 5, 7; III: 6, 4, 4, 6; IV: 5, 3, 4, 5. ITC on all legs (Fig. 62). Trichobothria and tarsal organ as in male. Book-lung openings as in male. Four spinnerets, PLS: basal segment 0.20, median segment 0.16, apical segment domed 0.04 long (Figs. 41, 44). Spigots as in male. Spermathe ca with a single receptacula arising from prolateral border of the long basal dome (Fig. 37).

Variation. Males (n = 10): total length 3.85-4.20; carapace 1.60-2.00 long; maxillae with 18-20 cuspules. Females (n = 20): total length 4.50-5.80; carapace 1.00-2.50 long; maxillae with 22-28 cuspules.

Additional material examined. Brazil, Rio de Janeiro: Nova Iguaçu (Reserva Biológica do Tinguá, 22°34'28.9'S; 43°24'57.6'W, 400 m), 2002, E. Folly-Ramos et al. coll., 5 males (IBSP 166103-166107); 54 females, 7 juveniles (IBSP 166108); 6 females, pitfall traps (IBSP 166109-166112); 1 male and 4 females (MNRJ 6806); 2 females, pitfall traps (MZSP 67298); 2 females, pitfall traps (MCN 52061).

Distribution. Known only from the type locality.

Natural history. Two females were observed in captivity. They built a horizontal silk-lined burrow on surface of soil with depth of ca. 12 mm and closed by a thin trap-door.

Etymology. The specific name is a noun in apposition taken from the type locality.

Ecological data

A total of 1,613 spiders (1,163 Araneomorphae and 450 Mygalomorphae) were collected in leaf litter with Winkler extractor over the course of 12 months, during four field expeditions at the Reserva Biológica do Tinguá. Of these, 436 spiders (15 males, 84 females, 351 juveniles) belong to two new Nemesiidae species, Acanthogonatus minimussp. nov. and Chaco tinguasp. nov.

Were recorded 22 individuals of A. minimussp. nov., three males (registered in summer), 11 females (seven in the spring collections) and eight juveniles. Since we only collected a few specimens of A. minimussp. nov. it is not possible to draw conclusions on the fenology of the species, but that is sufficient data to compare it with what we know about other species of the genus. We observed that male and female specimens of Acanthogonatus ericae Indicatti et al., 2008 were collected with pitfall traps in the winter and the spring of southern Brazil (Indicatti et al. 2008Indicatti RP, Lucas SM, Ott R, Brescovit AD (2008) Litter dwelling mygalomorph spiders (Araneae: Microstigmatidae, Nemesi idae) from Araucaria forests in Southern Brazil, with the description of five new species. Revista Brasileira de Zoologia 25: 529-546. doi: 10.1590/S0101-81752008000300021
https://doi.org/10.1590/S0101-8175200800... ). In another study using pitfall traps (Ferretti et al. 2012Ferretti N, Pompozzi G, Copperi S, Pérez-Miles F, Gonzalez A (2012) Mygalomorph spider community of a natural reserve in a hilly system in central Argentina. Journal of Insect Science 12(31): 1-16. doi: 10.1673/031.012.3101
https://doi.org/10.1673/031.012.3101... ), males of Acanthogonatus centralis Goloboff, 1995 were recorded when temperatures were medium or low (autumn, end of winter and spring), while females and juveniles were collected when temperatures were high or low (summer and winter).

Contrasting with A. minimus, C. tinguasp. nov. was abundant in the samples, totaling 12 adult males (2.89%), 59 females (14.2%) and 343 juveniles (83.5%). The phenology of C. tinguasp. nov. is illustrated in Fig. 63, which shows that the main activity period of males was during the winter (seven individuals), decreasing in the spring (three individuals). These values are statistically significant when the seasons are compared (KW = 9.173, GL = 3, p = 0.0270). However, the data obtained on male abundance are are not conclusive since the sample size is small. During the winter the lowest mean temperature and precipitation were recorded during the sampling period (Fig. 64), showing that the winter is probably the mating period of C. tinguasp. nov. If the same parameter is observed among females, an increase in the abundance curve is detected, but without clear activity peaks. A slight increase in activity was observed in the spring, when 22 females were collected, and during the summer, when 16 specimens were collected; these differences, however, are not statistically significance. Our dataset does not show clear activity peaks for females of C. tinguasp. nov., but there was a small and yet noticeable increase in activity in the spring and summer, when temperatures and precipitation were higher (Fig. 64).

During field captures in the autumn we observed a lack of males and a smaller number of females (N = 6) of C. tinguasp. nov. Juvenile specimens were numerous in samples from the four seasons, with significance values (KW = 10.902, GL = 3, p = 0.0122). We suggest that the autumn is the growing period, because newly born Nemesiidae spiders were found forming assemblages in the litter, making their detection easier using the Winkler extractor.

Another observation we have made while looking at the samples obtained with the Winkler extractor is the massive presence of females, five times greater than the number of males. This pattern could be explained by the selectivity of the Winkler trap compared with pitfall traps. The first favors the capture of spiders at an area of a square meter, whereas soil traps such as pitfall traps capture wandering spiders (Costa & Pérez-Miles 2002Costa FG, Pérez-Miles F (2002) Reproductive biology of Uruguayan theraphosids (Araneae, Theraphosidae). Journal of Arach nology 30: 571-587. doi: 10.1636/0161-8202(2002)030[0571:RBOUTA]2.0.CO;2
https://doi.org/10.1636/0161-8202(2002)0... , Candiani et al. 2005Candiani DF, Indicatti RP, Brescovit AD (2005) Composição e diversidade da araneofauna (Araneae) de serapilheira em três florestas urbanas na cidade de São Paulo, São Paulo, Brasil. São Paulo, Brasil. Biota Neotropica 5(1a): 1-13. doi: 10.1590/S1676-06032005000200010
https://doi.org/10.1590/S1676-0603200500... , Indicatti et al. 2005Indicatti RP, Candiani DF, Brescovit AD, Japyassú HF (2005) Diversidade de aranhas (Arachnida, Araneae) de solo na bacia do Reservatório do Guarapiranga, São Paulo, São Paulo, Brasil. Biota Neotropica 5(1a): 1-12. doi: 10.1590/S1676-06032005000200013
https://doi.org/10.1590/S1676-0603200500... ). In addition it is known that female mygalomorphs are more sedentary, whereas males wander a whole lot more (Costa & Pérez-Miles 2002Costa FG, Pérez-Miles F (2002) Reproductive biology of Uruguayan theraphosids (Araneae, Theraphosidae). Journal of Arach nology 30: 571-587. doi: 10.1636/0161-8202(2002)030[0571:RBOUTA]2.0.CO;2
https://doi.org/10.1636/0161-8202(2002)0... , Gonzalez-Filho et al. 2012Gonzalez-Filho HMO, Lucas SM, Paula FS, Indicatti RP, Brescovit AD (2012) On the taxonomy of Acanthoscurria Ausserer from Southeastern Brazil with data on the natural history of A. gomesiana Mello-Leitão (Araneae, Mygalomorphae, Theraphosidae). International Journal of Zoology 2012: 1-11., Ferretti et al. 2012Ferretti N, Pompozzi G, Copperi S, Pérez-Miles F, Gonzalez A (2012) Mygalomorph spider community of a natural reserve in a hilly system in central Argentina. Journal of Insect Science 12(31): 1-16. doi: 10.1673/031.012.3101
https://doi.org/10.1673/031.012.3101... , Paula et al. 2014Paula FS, Gabriel R, Indicatti RP, Brescovit AD, Lucas SM (2014) On the Brazilian Amazonian species of Acanthoscurria (Araneae, Theraphosidae). Zoologia 31(1): 63-80. doi: 10.1590/S1984-46702014000100008
https://doi.org/10.1590/S1984-4670201400... ).

ACKNOWLEDGMENTS

We wish to thank Alexander Bernhart for correcting the English in an earlier version of this manuscript; Ronaldo B. Francini Filho for the suggestions on the statistical analyses; three anonymous referees and the editor for their critical comments, which helped us to improve this manuscript; Instituto Chico Mendes de Conservação da Biodiversidade for the permits and the support with field work; Beatriz Maurício for her help with SEM images. This study was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (grants 2012/18287-1 to RPI; 2011/50689-0 to SML and ADB) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (grants 2009/12017-0 to ADB and 479377/2012-0 to RPI).

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