Thrixopelma nadineae, a New Theraphosine from Ecuador (Araneae: Theraphosidae) ^†

Abstract

Thrixopelma nadineae sp. nov. is described from Loja, Ecuador, based on the male, which possesses distinctive palpal bulb, metatarsal and tibial apophysis morphology. The new species represents the second species of Thrixopelma to be recorded from Ecuador.

1. Introduction

The theraphosid spiders of Ecuador are poorly known; presently, 20 valid species are recognized by the World Spider Catalog [1]: Amazonius elenae (Schmidt, 1994), Avicularia hirschii Bullmer, Thierer-Lutz & Schmidt, 2006, Avicularia juruensis Mello-Leitão, 1923, Avicularia lynnae Fukushima & Bertani, 2017, Avicularia purpurea Kirk, 1990, Avicularia rufa Schiapelli & Gerschman, 1945, Cyclosternum gaujoni Simon, 1889, Cyclosternum janthinum (Simon, 1889), Cyclosternum schmardae Ausserer, 1871, Cymbiapophysa velox (Pocock, 1903), Megaphobema velvetosoma Schmidt, 1995, Neischnocolus yupanquii (Pérez-Miles, Gabriel & Gallon, 2008), Pamphobeteus augusti (Simon, 1889), Pamphobeteus petersi Schmidt, 2002, Pamphobeteus ultramarinus Schmidt, 1995, Pamphobeteus vespertinus (Simon, 1889), Psalmopoeus ecclesiasticus Pocock, 1903, Reversopelma petersi Schmidt, 2001, Tapinauchenius cupreus Schmidt & Bauer, 1996, Thrixopelma longicolli (Schmidt, 2003), and one further species may possibly be distributed in Ecuador: Cymbiapophysa yimana Gabriel & Sherwood, 2020. Many Ecuadorian theraphosid taxa need modern redescription (pers. obs.).

The genus Thrixopelma Schmidt, 1994, is currently only represented by T. longicolli in Ecuador and was recently revised by Sherwood et al. [2]. Whilst working through undetermined mygalmorph material loaned to DS from the Zoologisches Museum, Universität Hamburg, we discovered a new species of the genus. A second male was subsequently located by DS whilst working through undetermined mygalomorph material at the Natural History Museum, London.

In this work, we describe a new species of Thrixopelma from Loja, Ecuador, based on the male, which possesses a unique combination of palpal bulb and tibial apophysis morphology in conjunction with a strongly curved metatarsus I.

2. Materials and Methods

The specimens were examined under a binocular microscope. Photographs of the palpal bulb and tibial apophysis of the holotype were made using a Leica M125C auto-montage. Description style follows Sherwood et al. [3]. Abbreviations for museum collections follow Evenhuis [4]. Abbreviations, Institutes: BMNH = Natural History Museum, London, United Kingdom; ZMH = Zoologisches Museum, Universität Hamburg, Germany. Structures: ALE = anterior lateral eyes, AME = anterior median eyes, PLE = posterior lateral eyes, PME = posterior median eyes; PB = prolateral branch (of tibial apophysis), RB = retrolateral branch (of tibial apophysis). Other: coll. = collector; det. = determined by. Leg spine terminology follows Petrunkevitch [5] with the modifications proposed by Bertani [6]: d = dorsal, v = ventral, r = retrolateral, p = prolateral. Palpal bulb terminology follows Bertani [7] and Gabriel [8]: A = apical keel, PI = prolateral inferior keel, PS = prolateral superior keel, RI = retrolateral inferior keel, RS = retrolateral superior keel, SA = subapical keel, TH = tegular heel; with the additions proposed by Gabriel & Sherwood [9]: ER = embolic ridge, PR = prolateral ridge, PAR = prolateral apical ridge, PC = prolateral crease. Leg formulae start with the longest leg to the shortest in order of decreasing size, e.g., 4, 1, 2, 3. Urticating setae terminology follows Cooke, Roth & Miller [10]. All measurements are in mm. Podomeres were measured from the femur to tarsus and do not include coxa or trochanter measurements. Percentages for metatarsal scopulae show their comparative extent of length to that of the total length of the ventral aspect of the metatarsus. The map was made using SimpleMappr (Shorthouse [11]). In accordance with Article 8 of the International Code of Zoological Nomenclature, this work was registered in ZooBank (urn:lsid:zoobank.org:pub:995014E5-91F0-42A2-9A1A-1F9760617BD9) prior to publication. A map of the type locality is given in the Supplementary Information.

3. Results

Thrixopelma nadineae sp. nov.

Figure 1 and Figure 2, (urn:lsid:zoobank.org:act:82274AB5-473D-41D2-A1B2-0001C33B0524).

Type material: Holotype ♂ (ZMH-0000888), Loja, Ecuador, E. W. Witt leg., ded.16.I.1898; paratype ♂ (BMNH), Ecuador: Loja, Zamora Huico, in house at 2000 m, 1997, coll. P. Lewis & B. Klitgaard, Mygalomorphae det. P. Hillyard, NHM London.

Diagnosis: Thrixopelma nadineae sp. nov. can be distinguished from all known male congeners by the absence of a palpal tibial apophysis (present in all known congeners), the presence of a basal crest on the PS (unknown in all known congeners), the absence of a basal crest on the PI (present in all known congeners), the position of the medial crest of the PI (comparatively more anterior than in all other known congeners), the developed PS (PS weakly developed in all known congeners) (Figure 1), the strongly curved metatarsus I (slightly curved in all known congeners), the elongate and finger-like RB (not so in all known congeners) (Figure 2) and its diminutive size. T. nadineae sp. nov. is further distinguished from the male of T. longicolli by the developed PI (PI well-developed in T. longicolli) (see Figure 1).

Etymology: The epithet is a matronym honouring Nadine Dupérré (Collections Manager, Zoologisches Museum, Universität Hamburg), our friend and colleague, in recognition of her numerous contributions to arachnology, especially on the taxonomy of spiders from Ecuador.

Description of holotype male (ZMH-0000888): Total length including chelicerae: 24.2. Carapace: length 11.4, width 4.1. Caput: slightly raised. Ocular tubercle: slightly raised, length 0.9, width 1.3. Eyes: AME > ALE, ALE > PLE, PLE > PME, anterior eye row procurved, posterior row slightly recurved. Clypeus: narrow; clypeal fringe: medium. Fovea: deep, recurved. Chelicera: length 2.5, width 1.8. Abdomen: length 10.3, width 7.1. Maxilla with 130–150 cuspules covering approximately 60% of the proximal edge. Labium: length 1.2, width 1.1, with 35–40 cuspules mostly separated by 0.5–1.0 times the width of a cuspule. Labio-sternal mounds: separate. Sternum: length 4.8, width 3.8, with three pairs of sigilla. Tarsi I–IV divided by line of setae. Metatarsal scopulae: I 86%; II 42%; III 30%; IV 24%. Lengths of legs and palpal segments: see

Table 1. Thrixopelma nadineae sp. nov. holotype male (ZMH-0000888), podomere lengths.

	I	II	III	IV	Palp
Femur	9.3	8.8	7.5	10.0	6.0
Patella	5.2	4.8	3.9	4.4	3.2
Tibia	8.5	6.8	5.6	8.7	4.3
Metatarsus	7.5	7.5	8.0	11.5	–
Tarsus	5.1	4.5	3.5	5.3	1.3
Total	35.6	32.4	28.5	39.9	14.8

, legs 4,1,2,3. Spination: femur I d 0–2–2, II d 0–2–0, III d 2–2–2, IV d 0–0–2, palp d 0–0–3, patella I p 0–0–1, II p 0–1–0, III p 0–0–1, r 0–0–1, IV p 0–0–2, palp d 0–0–3, tibia I d 2–2–0, v 3–2–2, II d 1–1–0, v 3–2–3, III d 2–2–0, v 2–2–2, IV d 2–2–0, v 4–3–2, palp p 1–0–0, r 0–2–1, metatarsus I d 0–1–0, v 2–0–1 (apical), II d 0–2–0, v 1–1–2 (apical), III d 2–2–2, v 3–4–5 (3 apical), IV d 2–2–2, v 2–3–5 (3 apical). Femur IV with fine but firm spine-like setae aligned on dorsal face on lateral borders. Tibia I with paired tibial apophysis, RB almost twice as long as PB, RB finger-like in shape in apical third (Figure 2). Femur III: incrassate. Palpal tibia: slightly incrassate, retrolateral apophysis absent. Metatarsus I: strongly curved (see Figure 2). Posterior lateral spinnerets with three segments, basal 1.4, median 0.9, digitiform apical 1.1. Lateral median spinnerets with one segment. Palpal bulb with TH; embolus angular and wide, with slight tapering at the very apex; PS elongate, disjunct, originating ventrally at base of the bulb and running prolaterally towards the apex of the embolus, with developed basal crest, PI developed, elongate, disjunct, originating ventrally at the base of the bulb and running prolaterally towards the apex of the embolus, with a developed medial crest and lacking a basal crest (Figure 1;

Table 2. Bulb keel morphology of Thrixopelma nadineae sp. nov. and other species of Thrixopelma Schmidt, 1994, sensu Sherwood et al. [2] where males are properly known. Format follows Bertani [7] and Gabriel [8] with modifications based on the new palpal bulb features detailed by Gabriel & Sherwood [9]. Homologous keels present: weakly developed (+), developed (++), well-developed (+++), or absent (–).

Taxon	PS	PI	A	SA	RS	RI	Additional Comments
Thrixopelma lagunas Schmidt & Rudloff, 2010	+	++	+	–	–	–	PS non-elongate, without crest, PI elongate, medial crest well-developed, basal crest developed, ER, PR and PAR absent, PC present, somewhat widened in posterior third, constricted in anterior third.
Thrixopelma longicolli (Schmidt, 2003)	+	+++	+	–	–	–	PS non-elongate, without crest, PI elongate, medial crest developed, basal crest well-developed, ER, PR and PAR absent, PC present, somewhat widened in posterior third, constricted in anterior third.
Thrixopelma nadineae sp. nov.	++	++	+	–	–	–	PS elongate, disjunct, with developed basal crest, PI elongate, disjunct, medial crest developed, basal crest absent, ER, PR and PA absent, PC present, somewhat widened in posterior third, constricted in anterior third.

). Urticating setae: Type III present dorsally. Colour: alcohol preserved brown.

Female: Unknown.

Distribution: Known only from the type locality, Loja, Ecuador (Figure S1).

Remarks: The right-hand side palpal bulb of the holotype has some deformity and was thus not considered in more detail in the analysis. The left-hand and right-hand side palpal bulbs of the paratype male in BMNH were consulted to ensure that the characters found in the left-hand side palpal bulb of the holotype were uniform for the species and this was indeed the case.

4. Discussion

Thrixopelma nadineae sp. nov. is the second species of Thrixopelma known from Ecuador. We suspect more undescribed taxa exist in the country, given the high levels of endemism known for other spider groups (e.g., Dupérré & Tapia [12]; Dupérré et al. [13]) and its ecoregional structure. The discovery of T. nadineae sp. nov. is interesting as this species has many divergent traits in comparison to its recently redescribed male congeners T. lagunas and T. longicolli. Most notably, in this species the PS is developed and has a basal crest. Conversely, a basal crest has only been found on the PI in T. lagunas and T. longicolli (Sherwood et al. [2]) and the same is true for several other (presently undescribed) species (pers. obs.). The total body length of T. nadineae sp. nov. is also 10.6 millimetres less that of the next smallest known male congener (i.e., the holotype male of T. lagunas (SMF 66757-84), see Sherwood et al. [2]). These findings demonstrate that much is still to be discovered about South American theraphosines. It also demonstrates that interesting discoveries are still to be made when working through unsorted historical museum material, adding further weight to broader discussions about the value of natural history museums (e.g., Allmon [14]; Bradley et al. [15]; Mares [16]; Nudds & Pettitt [17]; Suarez & Tsutsui [18]).