Arboriticus spinosissimus (Mello-Leitao, 1923) Borges & Abegg & Paladini & Bertani, 2025

Borges, Leandro Malta, Abegg, Arthur Diesel, Paladini, Andressa & Bertani, Rogério, 2025, A new genus and five new species of arboreal tarantulas (Araneae: Theraphosidae) from Brazil, Zootaxa 5679 (4), pp. 521-551 : 529-530

Arboriticus spinosissimus gen. nov. comb. nov.

( Figs 1 , 15 –18)

Eupalaestrus spinosissimus Mello-Leitão, 1923: 221 , figs 104, 105; Pérez-Miles, 1992: 34 (nomen dubium); Bertani, 2001: 283, figs 19, 56,57 (removed from nomen dubium, syn. senior of Eupalaestrus tarsicrassus and Pamphobeteus holophaeus , misidentifications).

Diagnosis. Females resemble those of A. tarsicrassus gen. nov. comb. nov., A. giganteus gen. nov. sp. nov. and A. celsoi gen. nov. sp. nov. by the incrassate metatarsus IV with stiff setae ( Figs 15 , 18). They can be distinguished from all the species above by the presence of spiniform setae on the maxilla retroventral edge (Fig. 16).

Type material. Holotype female from BRAZIL, state of Rio de Janeiro, Pinheiro (now Pinheiral) [22º31’S, 44º00’W, 377 m a.s.l.], MZUSP 130 (See remarks below on the type identity).

Redescription. Holotype female ( Figs 15 –18) MZUSP 130 . Carapace 19.43 long, 15.96 wide, chelicerae 9.33. Legs (femur, patella, tibia, metatarsus, tarsus, total): I: 13.15, 7.48, 9.67, 8.96, 5.96, 45.22. II: 11.93, 7.08, 8.79, 8.65, 5.87, 42.32. III: 11.19, 6.63, 8.05, 9.14, 5.44, 40.45. IV: 14.00, 7.85, 11.85, 13.51, 5.65, 52.86. Palp: 9.98, 5.27, 6.98, –, 6.64, 27.87. Midwidths: femora I– IV = 2.60, 2.47, 2.83, 2.75, palp = 1.88; patellae I– IV = 2.83, 3.12, 3.24, 3.74, palp = 2.44; tibiae I– IV = 2.54, 2.29, 2.77, 3.83, palp = 2.30; metatarsi I– IV = 2.11, 2.15, 2.17, 3.35; tarsi I– IV = 2.16, 2.06, 2.01, 2.02, palp = 2.10. Abdomen 27.35 long, 22.46 wide. Spinnerets: PMS, 2.30 long, 1.04 wide, 1.59 apart; PLS, 2.64 basal, 2.61 middle, 3.36 distal; midwidths 1.72, 1.42, 1.09, respectively.

Carapace: 1.21 longer than wide; cephalic area noticeably raised. Fovea: Straight, 2.71 wide. Eyes and eye tubercle: Tubercle 2.08 long, 3.16 wide. Eye sizes and inter-distances: AME 0.59, ALE 0.57, PME 0.0.39, PLE 0.57, AME–AME 0.37, AME–ALE 0.32, AME–PME 0.18, ALE–ALE 1.91, ALE–PME 0.53, PME–PME 1.60, PME–PLE 0.14, PLE–PLE 2.23, ALE–PLE 0.47, AME–PLE 0.62. Maxillae: Length 6.12, width 3.22. Cuspules: ca. 242 spread over ventral inner heel. Labium: 2.33 long, 2.96 wide, with 111 cuspules spaced by ca. one diameter from each other on the anterior third center. Chelicerae: Basal segment with 13 teeth on promargin and denticles on basal area. Sternum: 9.24 long, 6.89 wide. Sigilla: first pair barely visible, second rounded, third oval.

Legs: formula IV I II III. Length leg IV to leg I: 1.17. Scopula: Tarsi I – IV fully scopulate. Metatarsi I – II fully scopulate; III 1 /2, IV 1 /5 distal scopulate. Metatarsus IV divided by a row of 2–3 setae. Spination: palp: femur 0, patella 0, tibia v4 (3ap), p0-1-1; leg I: femur p0-0-1, patella 0, tibia v0-0-2ap, metatarsus v0-0-1ap; leg II: femur 0, patella 0, tibia v0-0-2ap, metatarsus v0-0-3; leg III: femur 0, patella 0, tibia v0-0-2ap, p0-1-1, r0-1-1, metatarsus v0- 3-4ap, p1-0-1, r1-0-1; leg IV: femur 0, patella 0, tibia v0-2-4 (3ap), r1-1-1, metatarsus v18 (3ap), p1-0-1, r0-1-1ap. Spiniform setae on retrolateral maxillae and coxae I– III, and prolateral coxae I– IV. Tibia IV thickened, especially at distal end, metatarsus IV thickened at base, tibia and metatarsus covered with stiffed setae (Fig. 18). Urticating setae: Type I only .

Spermathecae: Two short spermathecae separated by weakly sclerotized area, spermathecal stalk narrower than rounded spermathecal bulb (Fig. 17).

Color pattern (in alcohol): All spider homogeneous reddish brown.

Distribution. Known only from the type locality, Pinheiro, in the state of Rio de Janeiro, Brazil ( Fig. 1 ).

Remarks. Mello-Leitão (1923) described Eupalaestrus spinosissimus in detail based on a female from Pinheiro (now Pinheiral) in the state of Rio de Janeiro, Brazil, and emphasized the most characteristic features: “The posterior legs are thicker than the anterior legs”, “the tibia is thicker than the femur”, “the metatarsus is slightly curved and convex at the base”, “the posterior tibia and metatarsus are covered almost entirely with hirsute and stiff setae”, “the coxae of the first pair of legs have transverse rows of small black spines pointing forward”, “there are some spines on the distal end of the posterior face of the maxilla”, and “there are numerous black spines in dense areas on the anterior face of the posterior coxae and on the posterior faces of the second and third coxae”. This last character gives the species name, spinosissimus ( Mello-Leitão 1923) .

In the same publication, Mello-Leitão (1923) described P. holophaeus , also based on a female specimen from Piracicaba, state of São Paulo, Brazil. However, the author did not mention the remarkable features observed and detailed in the description of E. spinosissimus . Pérez-Miles (1992) later considered the type specimen of E. spinosissimus as lost, and considered the species as incertae sedis. Some years after, Bertani (2001) revalidated E. spinosissimus based on the analysis of other specimens having those unusual features. After examination of the supposed holotype of P. holophaeus, Bertani (2001) considered it as a junior synonym of E. spinosissimus , since it has most of the features mentioned by Mello-Leitão (1923) in that species.

Upon reexamining the type assigned to P. holophaeus , we confirm that all the features mentioned by Mello-Leitão for E. spinosissimus are present in this specimen. Particularly noteworthy are the spiniform setae at the distal end of the maxilla, which were observed only in this specimen (Fig. 16). It is astonishing that the same remarkable morphological features highlighted by Mello-Leitão (1923) for E. spinosissimus are not mentioned in the description P. holophaeus even though the putative holotype bears them, which lead us to suspect it might not be the real type. Inconsistencies in the descriptions, specimen details, and current findings lead us to conclude that the specimen MZUSP 130 corresponds to the previously presumed lost type specimen of E. spinosissimus . However, Mello-Leitão (1923) declared that the type of E. spinosissimus was deposited in “his own collection” which was later included in the MNRJ arachnological collection. Nevertheless, Silva-Moreira et al. (2010) stressed the difficulties in stablishing the actual collection, where the types of Mello-Leitão were deposited, and that there is a historical confusion as to whether some mygalomorph types were deposited at the MZUSP or MNRJ. Furthermore, Mello-Leitão (1923) stated in the description that the number of the holotype of Pamphobeteus holophaeus is MZUSP 129-A, whereas the specimen labeled as type has the number MZUSP 130, indicating that this is not the real type of P. holophaeus , which seems to be lost ( Fig. 15 ). Additionally, the type locality of Pamphobeteus holophaeus is Piracicaba, in the state of São Paulo, Brazil, which has very distinct phytophysiognomy and topography when compared to the mountainous areas where the species of Arboriticus gen. nov. are known to occur ( Fig. 1 ). Pamphobeteus holophaeus was described and keyed by Mello-Leitão together with other Pamphobeteus (now Vitalius ) species he described, and the type locality of this species is an area where the species Vitalius dubius ( Mello-Leitão, 1923) is very common ( Bertani 2001), and we have little doubt that they are conspecific. Therefore, we remove Pamphobeteus holophaeus Mello-Leitão, 1923 from the synonymy with Eupalaestrus spinosissimus Mello-Leitão, 1923 , transfer it to Vitalius holophaeus ( Mello-Leitão, 1923) comb. nov., and consider it a junior synonym of Vitalius dubius ( Mello-Leitão, 1923) n. syn.

Figures

FIGURE 1. Map of Brazil showing geographic records of Arboriticus gen. nov. species. Dots represent type localities, squares additional localities, and triangles correspond to records of undetermined collected specimens, which are likely undescribed species.

FIGURES 15─18. Arboriticus spinosissimus gen. nov. comb. nov., holotype female. 15, labels and habitus. 16, maxilla, retroventral, showing spiniform setae. 17, spermathecae, dorsal. 18, reproduction of the original drawings from Mello-Leitão’s 1923 description. Scale bar = 1 mm.