A new species of Illacme Cook & Loomis, 1928 from Sequoia National Park, California, with a world catalog of the Siphonorhinidae (Diplopoda, Siphonophorida) Author Marek, Paul E. Author Krejca, Jean K. Author Shear, William A. text ZooKeys 2016 626 1 43 http://dx.doi.org/10.3897/zookeys.626.9681 journal article http://dx.doi.org/10.3897/zookeys.626.9681 1313-2970-626-1 36E16503BC2B4D92982EFC2088094C93 Taxon classification Animalia Siphonophorida Siphonorhinidae Genus Illacme Cook & Loomis, 1928 Family placement. The genus Illacme is placed in the family Siphonorhinidae based on the following characters: Head pear-shaped (♂) or triangular (♀), not elongate or beak-shaped, as in the Siphonophoridae (Fig. 2 A-F ). Antennae elbowed between antennomeres 3, 4 (Figs 2B; 3A, B). Antennomeres 5, 6 with apical dorsal cluster of 7 or 8 basiconic sensilla (Bs2) in slight depression, not in defined circular pits, as in the Siphonophoridae (Figs 2B, D; 3A, B). Antennomere 1 set deep in cranium, not entirely visible dorsally as in Siphonophoridae (Figs 2A, B; 2E; 3C, D). Antennomere 2 longer than wide, conical, not doughnut-shaped and wider than long as typical in Siphonophoridae . Anterior margin of collum straight, not emarginate medially as in Siphonophoridae . Sterna with prominent midline triangular projections, oriented ventrally (Figs 3E, F; 4A, B). Posterior gonopods with distal podomere divided into 2-4 branches with one branch spike-like (Figs 4C, D, E, F; 5 A-D ). See also diagnoses of Illacme in Shelley (1996b , pg. 23), Marek et al. (2012 , pg. 85), and Enghoff et al. (2015 , pg. 386), and of Siphonorhinidae in Shelley and Hoffman (2004 , pg. 218), Wesener (2014 , pg. 417), and Enghoff et al. (2015 , pg. 386). Diagnosis. Adults of Illacme are distinct from other siphonorhinid genera (and commonly encountered millipedes co-occurring with Illacme tobini sp. n. and Illacme plenipes ) based on the combination of the following characters: Body light cream-colored, thread-like, extremely narrow and long (max. width: ♂ 0.55, ♀ 0.64; max. length: ♂ 28.16, ♀ 40.40). Adult individuals with 84-192 segments, and with 318-750 legs. Body covered with many long delicate setae, imparting a velvety appearance (Figs 5E, F; 6A, B). Antennae elbowed between antennomeres 3, 4 (Figs 2B; 3A, B). Antennomeres 5, 6 enlarged, appearing much larger relative to other articles (Figs 2B, D, 3A, B). Head pear-shaped in males or triangular or chevron-shaped in females, eyeless (Fig. 2 C-F ). Genae slightly convex (♂) or straight (♀), not concave (imparting a teardrop-shaped head) as in Nematozonium filum , Siphonorhinus sp. ( Wesener 2014 ), and the family Siphonophoridae (Shelley 1996, Shelley and Hoffman 2004 ). Mouthparts (gnathochilarium, mandibles) and labrum tightly appressed, tapered anteriorly to rounded apex-not beak-shaped, as in the Siphonophoridae (Figs 2 A-F ; 3C, D). Labrum with a deep medial slit, margins lined with teeth (Figs 6 C-F ; 7 A-F ). Denticulate shelf-like carina, projecting dorsally from labrum-epistome margin (Figs 6E, F; 7D; 8A, B). 9th and 10th leg pairs modified into gonopods, each comprising 7 podomeres (Figs 4C, D; 8 C-F ; 9 A-F ). Anterior gonopod thick, bulkier than posterior gonopod (Figs 4C, D; 8 C-F ). Anterior gonopodal apex (podomere 7, A7-Fig. 4C, D) spade-shaped; at rest, cupped sheath-like around posterior gonopodal stylets (podomere 7, P7-Figs 4E, F; 9 A-F ). Posterior gonopodal podomere 7 deeply divided, comprising a bundle of 3 ( Illacme plenipes ) or 4 ( Illacme tobini sp. n.) stylus-shaped articles; one article spike-shaped (Fig. 4E, F); other siphonorhinid taxa with 2 stylus-shaped articles and a small spine ( Nematozonium filum ) or 2 articles without spine ( Siphonorhinus species and Kleruchus olivaceus Attems, 1938). 2, 3 dorsal-most, longest articles laminate distally and recurved laterally, with denticulate posterior margins appearing saw-like (Fig. 5 A-D ). Ventral-most, shortest article acuminate distally, spike-like.