Sunday, April 12, 2020

[Diplopoda • 2020] Trachyjulus magnus • A Remarkable New Species of the Millipede Genus Trachyjulus Peters, 1864 (Diplopoda, Spirostreptida, Cambalopsidae) from southern Thailand, based both on Morphological and Molecular Evidence

Trachyjulus magnus 
Likhitrakarn, Golovatch, Jeratthitikul, Srisonchai, Sutcharit & Panha, 2020

A new, giant species of Trachyjulus from a cave in southern Thailand is described, illustrated, and compared to morphologically closely related taxa. This new species, Trachyjulus magnus sp. nov., is much larger than all other congeners and looks especially similar to the grossly sympatric T. unciger Golovatch, Geoffroy, Mauriès & VandenSpiegel, 2012, which is widespread in southern Thailand. Phylogenetic trees, both rooted and unrooted, based on a concatenated dataset of the COI and 28S genes of nine species of Cambalopsidae (Trachyjulus, Glyphiulus, and Plusioglyphiulus), strongly support the monophyly of Trachyjulus and a clear-cut divergence between T. magnus sp. nov. and T. unciger in revealing very high average p-distances of the COI gene (20.80–23.62%).

Keywords: cave, diplopod, molecular-based phylogeny, morphological character, taxonomy

Figure 1. Trachyjulus magnus sp. nov., habitus, live coloration.
A ♂ holotype B paratypes. Scale bars: 1 cm.

Family Cambalopsidae Cook, 1895
Genus Trachyjulus Peters, 1864

Trachyjulus magnus sp. nov.

Name: To emphasize the largest body size of this species compared to all other species known in the genus.

Diagnosis: This new species differs from all other Trachyjulus spp. by the largest body size (43.5–64.2 mm long, 2.1–2.8 mm wide), and also from the particularly similar and grossly sympatric T. unciger (23–42 mm long, 1.2–2.0 mm wide) in having the tegument of rings 2 and 3 nearly smooth (vs evidently carinate), carinotaxic formulae of typical rings (11–8/11–8+I/i+2/2+m/m vs 8–6/8–6+I/i+2/2+m/m), combined with the number of ommatidia (5–6+5–6 vs 4+4), and the posterior gonopods showing medial coxosternal processes (mcp) subtrapezoid (vs shorter and lobe-shaped).

 Natdanai Likhitrakarn, Sergei I. Golovatch, Ekgachai Jeratthitikul, Ruttapon Srisonchai, Chirasak Sutcharit and Somsak Panha. 2020. A Remarkable New Species of the Millipede Genus Trachyjulus Peters, 1864 (Diplopoda, Spirostreptida, Cambalopsidae) from Thailand, Based both on Morphological and Molecular Evidence.  ZooKeys. 925: 55-72. DOI:  10.3897/zookeys.925.49953