Description

Description of holotype (♂) USNM TYPE NO. 976 - Counts and measurements: p = 143. a = 2. l = 562. (143 + 2 + T). HW = 0.30. HL = 0.34. ISW = 0.20. AW = [antennae missing]. CW = 0.42. W 1 = 0.53. W 2 = 0.55. W 3 = 0.55. L 1 = 0.20. L 2 = 0.20. L 3 = 0.18. H 1 = 0.31. H 2 = 0.30. H 3 = 0.33. AS 1 = 0.45. A 5 W = 0.05. P 5 W = 0.04. BL = 28.16. Head pear-shaped, tapered anteriorly to round point at a 160 ° angle anterior from antennal sockets; occipital area posterior from antennal sockets gradually curved medially towards neck (Figs 2, 3, Mb- 805574 - note: all SEMs herein are images of specimen # SPC 000932, not the holotype). Head pilose, covered with long, slender setae (Fig. 2, Mb- 805577). Mouthparts (gnathochilarium, mandibles) and labrum tightly appressed, tapered anteriorly to round point (Fig. 3, Mb- 805586). Gnathochilarium elements (stipes, promentum, etc.) indistinguishably fused, tightly appressed to the ventral surface of the head, leaving a small opening anteriorly. Lateral opening apparent between gnathochilarium and head capsule (Fig. 2 a, Mb- 805587). Mandibles thin, stylet-like, with heavily calcified apices (viewed dorsally through translucent head capsule at 400 x with a compound microscope). Labrum with triangular tooth-lined orifice (Fig. 7 a, b; Mb- 805580). Denticulate shelf-like carina, projecting dorsally from labrum-epistome margin (Fig. 8 a, b; Mb- 805588). Gnathochilarium, mandible and head capsule noticeably separate at base, 1 / 3 head length distally from mandibular joint (Fig. 2 a, Mb- 805589). Antennae sub-geniculate, elbowed between antennomeres 3, 4, comprising 7 antennomeres (Fig. 3, Mb- 805578). Antennae massive distally; antennomeres 5, 6 enlarged (Fig. 3, Mb- 805579). Five sensillum types: 4 apical cones (AS) oriented in a trapezoidal cluster on 7 th antennomere, with longitudinally grooved outer surface and apical circular invagination (Fig. 13, Mb- 805590). Chaetiform sensilla (CS) widely spaced on antennomeres 1 - 7, each sensillum with 2 or 3 barbules (Fig. 14 a, Mb- 805591). Trichoid sensilla (TS) oriented apically encircling antennomeres 1 - 7, lacking barbules (Fig. 14 b, Mb- 805592). Small basiconic sensilla (Bs 2) in clusters of 7 or 8; in slight depressions oriented apical dorsally (retrolaterally) on antennomeres 5 and 6; smooth, finger-shaped, 1 / 2 length of chaetiform sensillum (Fig. 4, Mb- 805593). Spiniform basiconic sensilla (Bs 3) in cluster of 5, oriented apical dorsally on 7 th antennomere; tips facing apical cones (on longitudinal axis with Bs 2 on antennomeres 5, 6); each sensillum with 2 barbules (Fig. 13 b, Mb- 805594). Antennae extend posteriorly to middle of 3 rd tergite. Relative antennomere lengths 6> 2> 5> 3> 4> 1> 7. Segments: Collum not covering head, with straight cephalic edge, gradually tapering laterally (Fig. 2 b, Mb- 805595). Collum with carina present on anterolateral margin, appearing scaly (Fig. 15, Mb- 805596). Carina repeated serially on lateral tergal and pleural margins (absent from telson). Lateral tergal and pleural carinae jagged, pronounced on midbody segments (Fig. 16 a, Mb- 805597). Lateral margin of collum round. Tergites: Metazonites rectangular, 3 x wider than long, slightly convex (Fig. 17, Mb- 805598). Paranota absent. Metazonite dorsal surface pilose, covered with long, slender setae (Fig. 2, Mb- 805599). Tergal setae hollow, cavity diameter 1 / 8 that of setae diameter; tipped with silk-like exudate, tangled, appearing adhered to neighboring setae (Fig. 18, Mb- 805600). (NB: Tergal silk-like exudate observed in scanning electron micrographs, and by the observation of fine strands issuing from the metaterga of live individuals, viewed while magnified at 80 x with a stereomicroscope. Silk stickiness was indicated by increased adherence of soil particles after handling and live observation of the millipede's coiled body becoming stuck together.) Metazonite posterior margin (limbus) lined with posteriorly projecting anchor-shaped spikes and a row of conical spikes just dorsal to anchor-shaped spikes (Fig. 17 a, Mb- 805601). Anchor-shaped spikes alternating in size (large, small) along row. Ozopores oriented dorsally, located near limbus, absent from tergites 1 - 3 and telson. Ozopores elevated slightly (porosteles absent), with 2 stout posteriorly projecting spines and encircled by 13 - 15 robust setae (Fig. 19, Mb- 805602). 3 or 4 stout flat tubercles opposite ozopore near anterior margin, lunate arrangement encircling ozopore (Fig. 17 b, Mb- 805603). Posterior tergites more convex, covered with a greater density of long, slender " silk " - exuding setae (Fig. 20, Mb- 805604). Lunate-arranged tubercles opposite ozopores on posterior metazonites: conical and spiked, not flat. Apodous segments lacking sterna, pleurites contiguous in midline. Apodous tergites densely setose, covered with unevenly distributed spikes (Fig. 21, Mb- 805605). Telson densely covered with irregularly oriented and unevenly distributed stout spines; posterior margin lined with variably-shaped posterodorsally oriented anchor-shaped spikes. Tergal tubercles and spikes: consistently projecting posteriorly, occasionally posterodorsally. Prozonite highly sculptured, with 5 rows of discoidal flat tubercles; anterior 3 rows staggered and posterior 2 rows aligned (Fig. 22, Mb- 805606). Pleurites quadrate, flat, with jagged scaly lateral, posterior and medial margins (Fig. 16, Mb- 805609). Pleurite medial margin broad, with scaly carina (Fig. 16 b, Mb- 805610). Left and right pleurites plate-like, comprising 4 / 5 ' s of ventral segment space. Left and right pleurites broadly overlapping sternite, covering spiracles (Fig. 23, Mb- 805612). Sternites free, separate from pleurites; heart-shaped, wider anteriorly. Sternal surface with broad, jagged scales. Medial sternal ridge projecting ventrally, with spiracles and legs oriented ventrally (Fig. 24, Mb- 805614). Spiracles circular, orifice open; oriented dorsally above legs (Fig. 25, Mb- 805615). Anterior and posterior sternites separate. Tergites, pleurites and sternites separated by arthrodial membrane (Fig. 20, Mb- 805616). Arthrodial membrane between tergites and pleurites wider posteriorly. Telson pilose, covered with long, slender posteriorly recurved setae (Fig. 20, Mb- 805628). Paraprocts semihemispherical, anterior margins slightly scaly. Epiproct absent. Hypoproct small, one-eighth area of paraproct, with row of posterior projecting setae. Legs: six subequally shaped podomeres, with coxa slightly shorter and tarsus slightly longer. Legs with sparse setae, appearing similar to trichoid sensilla, with 2 or 3 barbules. Coxae nearly contiguous medially, separated by thin sternal ridge. Large posteroventral D-shaped opening for eversible sac (Fig. 26, Mb- 805618). Eversible sacs membranous, bulging slightly from opening (Fig. 24 b, Mb- 805620). Pregonopodal tarsus with stout bifurcate claw; dorsal subdivision thicker, more arcuate (Fig. 27, Mb- 805621). Postgonopodal tarsus with two separate claws, co-terminal on tarsal apex; dorsal claw thick and arcuate, ventral claw thin and setiform (Fig. 16 c, Mb- 805623). 2 nd leg pair with posteriorly oriented coxal gonapophyses; rounded, protuberant, one-third length of prefemur. Gonopods: 9 th, 10 th leg pairs modified into gonopods, each comprising 6 podomeres (Fig 6 a, b). Anterior gonopod thick, more robust than posterior gonopod (Fig. 10, Mb- 805583, Fig. 6 b). Anterior gonopodal apex (podomere 6) shovel-shaped; in repose cupped sheath-like around flagelliform posterior gonopodal apex (podomere 6, Fig. 11, Mb- 805584). Posterior gonopodal podomere 6 divided, comprising a bundle of 3 stylus-shaped articles (Fig. 5, Mb- 805627, Fig 6 a). 2 dors al-most, longest articles of P 6 laminate distally, recurved laterally, denticulate posterior margins, appearance similar to a chicken foot in rigor mortis (Fig. 12, Mb- 805585, Fig 6 a). Ventral-most, shortest article of P 6 acuminate distally, spike-like. Thin ridge-shaped sterna present between left and right gonopods, thicker between anterior gonopods.

Common Names

Taxonomic Hierarchy

Kingdom: Animalia

Phylum: Arthropoda

Class: Diplopoda

Order: Siphonophorida

Family: Siphonorhinidae

Genus: Illacme

Species: Illacme plenipes Cook & Loomis, 1928