Tawhai Álvarez-Padilla & Kallal & Hormiga 2020, gen. nov.
Creators: name: Álvarez-Padilla, Fernando
name: Kallal, Robert J.
name: Hormiga, Gustavo
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Araneae
Tetragnathidae
Tawhai

description: Genus Tawhai, gen. nov.
Figures 51–55
TYPE SPECIES: Tetragnatha arborea Urquhart, 1891.
DIAGNOSIS: In Tawhai the epigynum protrudes ventrally and its posterior margin extends beyond the epigastric furrow, like in Taraire (figs. 51D, 53A), but differs from the latter genera by the following characters: spermathecae cuticle covered with sclerotized clusters that bear the accessory glands openings (figs. 51H, 53C, D), copulatory ducts absent (the spermatheca opens directly in the epigynum plate as in Meta) and long and straight fertilization ducts enclosed by a membrane that communicates with the uterus externus (figs. 53F, 54F). Externally the epigynum bears several holes (observed only with SEM fig. 53A, B) that resemble those of Pinkfloydia (Dimitrov and Hormiga, 2011: figs. 15D, E, G); however, it differs from this Australian genus in the eyes, which are organized in two lines, and in having the spermathecae cuticle heavily sclerotized (figs. 51H, 53C). The CEBP is similar to that of Allende species in having a finger-shaped paracymbium with a sclerotized apical keel, an L-shaped long apophysis between the paracymbium and the basal part of the CEBP and the presence of short and thick macrosetae on the CEMP (figs. 52D, 54A–C). Tawhai differs from Allende by the lack of teeth on the cymbial apophysis and the CEBP base, the separation of the CEBP base from the cymbium by a membranous section (figs. 52D, 54C) and the CEMP contiguous with the cymbium margin (fig. 54A– C). Tawhai has a large and heavily sclerotized embolic apophysis similar to that of Taraire species, but it differs from the latter genus in the shape of this embolic apophysis (fig. 52C). In addition, the following features are unique to Tawhai: a short, rectangular, and membranous conductor separated from the embolus except at the apex (figs. 52A, C, 54A), embolus the largest sclerite with a hook shape in ventral view and bearing a subterminal spine observed in apical or mesal view (figs. 52B, 54A).
DESCRIPTION: Female total length 8.4. Cephalothorax length 3.6, width 2.7. Carapace glabrous, pale yellow with dark-brown markings over the fovea, extending to the dorsal surface of the ocular area and two patches over the chelicerae (fig. 51A). Ocular area dark brown, fovea longitudinal. Clypeus height 0.4 AME diameter. Eyes subequal in size. Chelicerae dark brown, glabrous cuticle smooth (fig. 51G). Three prolateral, two retromarginal teeth, and ca. two denticles between margins. Endites brown, internal margins pale-yellow, longer than wide. Labium rectangular, wider than long, same color as the endites. Sternum pale yellow, trapezoidal, wider between the first two legs (fig. 51E). Abdomen dorsum with scattered guanine white patches intercalated with dark-brown transverse bands against a light-brown background (fig. 51A); lateral surface with intercalated diffused brown stripes and white guanine patches (fig. 51C); ventral surface light brown with scattered guanine patches flanked by dark-brown irregular lines (fig. 51E). Booklung covers without stridulatory organs. Spinnerets brown, lighter pattern on internal surfaces. Ultrastructure of abdomen, tracheae and spinnerets observed with SEM. Abdomen cuticle flat reticulated, all tracheae not ramified, median tracheae tip leaf shaped. ALS one major ampullate, one nubbin, ca. 80 piriform, tartipores present. PMS one minor ampullate, one nubbin, and one cylindrical and three central aciniform. PLS aggregate and flagelliform spigot tips clustered together, ca. 18 aciniform spigots distributed in two parallel rows, two cylindrical gland spigots at periphery (fig. 51B). Leg formula 1-2-4-3, Femur I length 4.9. Background of legs yellow on the basal segments, becoming dark brown toward the apex, basal segments decorated with dark-brown annuli. All femora without trichobothria. Macrosetae few and present on all segments except metatarsi and tarsi. Spermathecae heavily sclerotized, covered with small sclerotized globular clusters with accessory gland ducts (figs. 51H, 53C, D, 54F). Copulatory ducts reduced, opening directly into the epigynal plate. Fertilization ducts sclerotized, long, narrow and inside a membranous sac that connects with the uterus externus (figs. 53E, F, 54F). Genital openings on the median posterior surface, median plate membranous (fig. 54E).
Male same as female except as noted. Total length 8.2. Cephalothorax length 4.4, width 3.2. Clypeus height 0.6 AME diameter. Chelicerae longer than female (fig. 51G, I), distal part with three promarginal, two retromarginal teeth and one denticle between margins. Femur I length 8.9. Male pedipalpal tibia three times as long as wide, apical margin bordered with a cuticlar rim (the male palpal morphology is described in Diagnosis; see figs. 52, 54).
COMPOSITION: Monotypic.
SYSTEMATICS: Tawhai is sister to Taraire (figs. 61–63), but the placement of the two genera together is unstable. Autapomorphies of Tawhai include the concavity of the ectal cymbial margin (figs. 52D, 54B), bearing macrosetae and the sclerotized globular clusters with accessory gland ducts that cover the spermathecae (figs. 53C, D, 54F).
ETYMOLOGY: The genus is named after the Māori word (tawhai) for the New Zealand endemic tree Nothofagus menziesii (Hook.f.) Oerst. (Nothofagaceae), the silver beech. It is indeclinable and feminine in gender.
DISTRIBUTION: Tawhai is found only in the North Island of New Zealand (fig. 55).
NATURAL HISTORY: The web of Tawhai arborea is given under the species description below.
description: Published as part of Álvarez-Padilla, Fernando, Kallal, Robert J. & Hormiga, Gustavo, 2020, Taxonomy And Phylogenetics Of Nanometinae And Other Australasian Orb-Weaving Spiders (Araneae: Tetragnathidae), pp. 1-107 in Bulletin of the American Museum of Natural History 2020 (438) on pages 1-107, DOI: 10.1206/0003-0090.438.1.1, http://zenodo.org/record/4613901