AnimaliaSiphonophoridaSiphonorhinidaeMarekPaul E.KrejcaJean K.ShearWilliam A.A new species of Illacme Cook & Loomis, 1928 from Sequoia National Park, California, with a world catalog of the Siphonorhinidae (Diplopoda, Siphonophorida)Zookeys20102016201662614310.3897/zookeys.626.9681 Illacme Cook & Loomis, 1928Family 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. 2A–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; 5A–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. 2C–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 2A–F; 3C, D). Labrum with a deep medial slit, margins lined with teeth (Figs 6C–F; 7A–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; 8C–F; 9A–F). Anterior gonopod thick, bulkier than posterior gonopod (Figs 4C, D; 8C–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; 9A–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. 5A–D). Ventral-most, shortest article acuminate distally, spike-like.

A Dorsal view of head, antennae and rings 1–5 of Illacme tobini sp. n. (scale bar 300 µm) B the same of Illacme plenipes (scale bar 300 µm) C Lateral (right) view of head and rings 1–5 of Illacme tobini sp. n. (scale bar 300 µm) D the same of Illacme plenipes (scale bar 300 µm). Illacme tobini sp. n.: E anterolateral (right) view of head and first leg pair (scale bar 100 µm) F lateral (left) view of head and first leg pair, antennae broken off at base (scale bar 100 µm). (Catalog #s: Illacme tobini sp. n. MPE00735, Illacme plenipes SPC000932.)

A Lateral (right) view of antenna of Illacme tobini sp. n. (scale bar 100 µm) B the same of Illacme plenipes (scale bar 100 µm). Illacme tobini sp. n.: C ventral view of head and rings 1–5 (scale bar 300 µm) D the same of head and rings 1–3, magnified view (leg pairs 2–6 broken off at prefemur-femur joint) (scale bar 200 µm) E Ventral view of rings 6 and 7 with sternites, pleurites and leg bases of Illacme tobini sp. n. (scale bar 100 µm) F the same of Illacme plenipes (scale bar 100 µm). (Catalog #s: Illacme tobini sp. n. MPE00735, Illacme plenipes SPC000932.)

A Anterior view of ring 6 sterna of Illacme tobini n. sp (scale bar 50 µm) B anterolateral (left) view of the same of Illacme plenipes (scale bar 50 µm) C Lateral (right) view of gonopods (leg pairs 9 and 10) of Illacme tobini sp. n. (scale bar 100 µm) D the same of Illacme plenipes (scale bar 100 µm) E Ventral view of gonopods of Illacme tobini sp. n. (centered on right posterior gonopod, leg-pair 10) (scale bar 50 µm) F the same of Illacme plenipes (scale bar 50 µm). (Catalog #s: Illacme tobini sp. n. MPE00735, Illacme plenipes SPC000932.)

A Lateral (right) view of gonopods of Illacme tobini sp. n. (centered on right posterior gonopod) (scale bar 50 µm) B the same of Illacme plenipes (scale bar 50 µm) C Lateral (right) view of right posterior gonopod apex of Illacme tobini sp. n. (scale bar 25 µm) D the same of Illacme plenipes (scale bar 25 µm) E Lateral (right) view of head, collum, and rings 2, 3 of Illacme tobini sp. n. (scale bar 200 µm) F the same of Illacme plenipes (scale bar 200 µm). (Catalog #s: Illacme tobini sp. n. MPE00735, Illacme plenipes SPC000932.)

A Dorsolateral (left) view of tenth prozonite and metatergite of Illacme tobini sp. n. (scale bar 100 µm) B the same of Illacme plenipes (scale bar 100 µm) C Dorsal view of anterior region of head and labrum of Illacme tobini sp. n. (scale bar 10 µm) D the same of Illacme plenipes (the gnathochilarial apices can be seen projecting beneath the medially split labrum) (scale bar 10 µm). Illacme tobini sp. n.: E anterolateral (left) view of head and first leg pair (scale bar 50 µm) F anterior view of head with gnathochilarium open showing flabellate mandibles (scale bar 50 µm). (Catalog #s: Illacme tobini sp. n. MPE00735, Illacme plenipes SPC000932.)

Illacme tobini sp. n.: A anterior view of head with gnathochilarium open showing flabellate mandibles (scale bar 30 µm) B anterolateral (right) view of head with gnathochilarium open showing mandibles and pectinate lamella with numerous rows of jagged ventrally projecting serrulae (scale bar 20 µm) C dorsal view of V-shaped endochilarial frontal body with fringed lobes (spatulae) protruding through gnathochilarial stipes (scale bar 20 µm) D anterolateral (right) view of open mouth and keel-shaped pectinate lamella of the mandible nested in V-shaped groove of the endochilarium (scale bar 30 µm) E dorsal view of labrum with deep medial incision (scale bar 10 µm) F anterior view of labrum with heavily porous surface (scale bar 10 µm). (Catalog #: Illacme tobini sp. n. MPE00735.)

A Dorsal view of anterior region of head and labrum of Illacme tobini sp. n. (scale bar 20 µm) B the same of Illacme plenipes (scale bar 20 µm) C Ventrolateral (right) view of gonopods of Illacme tobini sp. n. (scale bar 200 µm) D the same of Illacme plenipes (scale bar 200 µm) E Anteroventral view of gonopods of Illacme tobini sp. n. (scale bar 50 µm) F the same of Illacme plenipes (scale bar 50 µm). (Catalog #s: Illacme tobini sp. n. MPE00735, Illacme plenipes SPC000932.)

A Ventral view of gonopods of Illacme tobini sp. n. (scale bar 50 µm) B the same of Illacme plenipes (scale bar 50 µm) C Lateral (right) view of right anterior gonopod (leg-pair 9) of Illacme tobini sp. n. (scale bar 50 µm) D the same of Illacme plenipes (scale bar 50 µm) C Ventral view of gonopods of Illacme tobini sp. n. (centered on right anterior gonopod) (scale bar 50 µm) D the same of Illacme plenipes (scale bar 50 µm). (Catalog #s: Illacme tobini sp. n. MPE00735, Illacme plenipes SPC000932.)

 ShelleyRM (1996b) The milliped order Siphonophorida in the United States and northern Mexico. Myriapodologica 4: 21–33. http://www.vmnh.net/content/uploads/PDF/Research_and_Collections/Myriapodologica/Myriapodologica_v4_n4.pdf MarekPShearWBondJ (2012) A redescription of the leggiest animal, the millipede Illacme plenipes, with notes on its natural history and biogeography (Diplopoda, Siphonophorida, Siphonorhinidae). ZooKeys 241: 77–112. doi: 10.3897/zookeys.241.3831 EnghoffHGolovatchSShortMStoevPWesenerT (2015) Diplopoda—Taxonomic Overview. In: MinelliA (Ed.) Treatise on Zoology - Anatomy, Taxonomy, Biology. The Myriapoda, 2. Brill, Leiden, 363–453. ShelleyRMHoffmanRL (2004) A contribution on the South African millipede genus, Nematozonium Verhoeff, 1939 (Siphonophorida: Siphonorhinidae). African Entomology 12: 217–222. WesenerT (2014) First records of the order Siphonophorida from Madagascar and Mauritius (Diplopoda). Revue suisse de Zoologie 121: 415–423.