Iamarra 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
Iamarra

description: Genus Iamarra, gen. nov.
Figures 6, 56–60
TYPE SPECIES: Iamarra multitheca.
DIAGNOSIS: The only species included in Iamarra builds dense horizontal orb webs between tree buttresses (fig. 6A, B) that resemble those of Dolichognatha O. Pickard-Cambridge, 1869, and has the lateral eyes nonjuxtaposed, on separated tubercles, a feature it shares with Diphya Nicolet, 1849. Iamarra differs from both those genera by having all eyes of equal size (fig. 56G, I) and by lacking the leg I spination pattern of Diphya and from all other tetragnathids by the presence of the following unique features: embolus very large (the largest palpal sclerite), lamelliform and coiling around a slender conductor (figs. 56B, 57A–C, 59A), apically divided in a sclerotized lamella and a membranous sac where the spermatic duct opens (figs. 57C, 58D, 59B); conductor base thin and translucent, tip sclerotized and hook shaped (figs. 57A, 59A, C–D). The epigynum morphology is also unique and diagnostic, flat and trapezoidal in shape (figs. 56F, 59E), with the genital openings inside the epigastric furrow, slit shaped within a partially sclerotized triangular plate (figs. 56D, 58A, 59F), and with the spermathecae divided in clusters (figs. 56H, 58B, C, 59G).
DESCRIPTION: Male total length 3.92. Cephalothorax length 1.82, width 1.44. Carapace glabrous, pale yellow with dark-gray markings over fovea, extending to dorsal surface of ocular area and two patches over legs I and II. Ocular area dark brown under clypeus and laterally (fig. 56G). Fovea longitudinal, between two bulges of thoracic area. Clypeus height 0.42 AME diameter. Eyes subequal in size. Lateral eyes not juxtaposed, separated more than one lateral eye diameter. Chelicerae brown, glabrous, distal part divergent and fangs enlarged (fig. 56G), without ventral stridulatory ridges, with two pro- and one retromarginal teeth and three denticles between margins. Endites brown, internal margins pale yellow, longer than wide. Labium rectangular, wider than long, same color as endites. Sternum pale yellow with two anterior dark-gray markings, trapezoidal, wider between the first three legs. Abdomen dorsum covered with guanine white patches intercalated with dark-brown transverse bands over a gray background; laterally with diffused brown vertical stripes and white guanine patches; ventral surface dark brown without guanine patches. Booklung covers without striae. Spinnerets brown, lighter pattern on internal surfaces. Leg formula 1-2-4-3, Femur I length 3.29. All femora, patella, and tibia brown-yellow, with dark-brown annuli. All leg segments apically dark brown. All femora without trichobothria. Macrosetae few and present on all segments except metatarsi and tarsi. Male pedipalpal tibia triangular, as long as wide, apical margin wider and bordered with a translucent cuticle rim. CEBP and CEMP reduced and without macroseta. Paracymbium contiguous with cymbium, slender, with few basal setae, slightly curved apically (figs. 57D, 58E, 59C–D). Embolic basal apophysis small and triangular (fig. 59 C–D). Conductor fused to the tegular margin. Spermatic duct spiral without switchbacks (fig. 59B).
Female same as male except as noted. Total length 3.77. Cephalothorax length 1.68, width 1.35. Clypeus height 0.49 AME diameter. Chelicerae smaller than male, distal part straight, fangs not enlarged (fig. 56I), with three promarginal and two retromarginal teeth, and two denticles between margins. Ultrastructure of abdomen and spinnerets observed with SEM. Abdomen cuticle flat reticulated, all tracheae tubular, median tracheae restricted to abdomen, tracheal atrium glands present. ALS with one major ampullate, one nubbin, and ca. 45 piriform spigots. PMS with one minor ampullate, one nubbin, and one cylindrical and three central aciniform spigots. PLS araneoid triplet with base clustered together, aggregate and flagelliform tips not separated, ca. 12 aciniform distributed at the center, and two peripheral cylindrical spigots. Femur I length 2.85. Spermathecae membranous and covered with small sclerotized globular clusters with accessory gland ducts, duct bases flat (figs. 58B, C, 59G). Copulatory ducts reduced to a sclerotized rim that opens directly into the membranous spermathecae. Fertilization ducts sclerotized, following a straight path under the accessory gland clusters, apically bent 90° (fig. 59G).
COMPOSITION: Monotypic.
SYSTEMATICS: Autapomorphies of Iamarra include the massive embolus, with its apical region divided into a sclerotized lamella and a membranous sac where the spermatic duct opens (figs. 58D, 59B) and the spermathecae with small, sclerotized globular clusters with accessory gland ducts (fig. 58B, C). The phylogenetic placement of this genus is weakly supported in our analyses (figs. 61–63).
ETYMOLOGY: The genus name is derived and modified from the Ngadjon word for a spider web (jamarra). The Ngadjonji people are one the aboriginal inhabitants of what is now known as the Atherton Tablelands, in North Queensland, Australia. Their language is part of the Dyirbal group. Iamarra is indeclinable and feminine in gender.
DISTRIBUTION: This genus is found in northern Queensland (fig. 60B).
NATURAL HISTORY: The web of Iamarra multitheca is described in the section 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