A review of the taxonomy of spiny-backed orb-weaving spiders of the subfamily Gasteracanthinae (Araneae, Araneidae) in Thailand Author Macharoenboon, Kongkit Animal Systematics and Molecular Ecology Laboratory, Department of Biology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand Author Siriwut, Warut Animal Systematics and Molecular Ecology Laboratory, Department of Biology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand Author Jeratthitikul, Ekgachai https://orcid.org/0000-0002-3477-9548 Animal Systematics and Molecular Ecology Laboratory, Department of Biology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand ekgachai.jer@mahidol.edu text ZooKeys 2021 2021-04-16 1032 17 62 http://dx.doi.org/10.3897/zookeys.1032.62001 journal article http://dx.doi.org/10.3897/zookeys.1032.62001 1313-2970-1032-17 EBF7586A9EF748FEBFB53D8F1E372120 7E7EE68D2DB65E1680CC7E33B36AEC74 Genus Macracantha Simon, 1864 Type species. Aranea arcuata Fabricius, 1793 Diagnosis. Cephalic region highly elevated near the middle, abruptly sloped downward posteriorly. Median ocular quadrangle wider behind than in front. Cephalothorax overlapping anterior abdomen. Sternum heart-shaped, pointed posteriorly, concave anteriorly below labium. Abdomen octagonal with three pairs of spines, and sigilla on dorsal and ventral sides. Anterior edge of abdomen curved between median spines. Dorsal sigilla teardrop-shaped, subequal in size, arranged in three rows, and situated near the anterior edge, posterior edge, and behind the posterior edge. Four median sigilla arranged in a trapezoid. Median spines well developed, elongated. Ventral tubercle is absent. Spinnerets placed on elevated black sclerotized structure, forming a shape like a shield volcano. Legs elongated. Remarks. Macracantha was formerly classified as a subgenus of Gasteracantha , but later elevated to an independent genus by Emerit (1974) . This genus now consists of two species, M. arcuata ( World Spider Catalog 2020 ) and M. hasselti (this study). The latter species is currently transferred to Macracantha according to phylogenetic analyses and anatomical evidence in this study.