Autostreptus silvagonzalezi sp. nov.

urn:lsid:zoobank.org:act: 4439984B-190F-4D12-A09E-55D5812AF75D

Figs 1, 8–9

Diagnosis

Males of A. silvagonzalezi sp. nov. differ from those of other species of the genus by having telopodite (tp) with lamellar branch (ltp) thickened (Fig. 9C–F), but narrower than those in A. chilensis (Fig. 5F) and A. yanezi (Fig. 7F), and an acuminate, arched solenomere (sl); antetorsal process (atp) thickened, almost as long as the tp (Fig. 9C–F). First leg-pair with subtriangular pfp (Fig. 9A).

Etymology

The species epithet honours Francisco Silva González (1933–1990), the only Chilean millipede specialist in history.

Material examined

Holotype

CHILE – Maule Region • ♂; south of Constitución; 35.4563° S, 72.4229° W; 238 m a.s.l.; 12 Jul. 2012; G. Valenzuela D. leg.; MNHNCL 8449.

Paratypes

CHILE – Maule Region • 1 ♀; same data as for holotype; MNHNCL 8450 • 1 ♂; same data as for holotype; MZUC-CCC 48107 • 1 ♀; same data as for holotype; MZUC-CCC 48108.

Description (male holotype, MNHNCL 8449)

MEASUREMENTS. Length ca 4.3 cm, vertical diameter 3.2 mm, width 3.3 mm. 46 podous rings, no apodous ring in front of telson.

COLOR. After recent fixation in alcohol. Head, antennae, and collum blackish (Fig. 8A–C); body rings blackish in general, posterior margin of metazonites with brownish to amber colored; telson blackish (Fig. 8D), slightly faded; legs blackish, also faded by alcohol (Fig. 8C–D).

HEAD. Eyes each with ca 29 ommatidia in five horizontal rows (Fig. 8C). Antennae very short, reaching back to ring 2 when stretched; fifth and sixth antennomere with distodorsal patch of short sensilla basiconica, seventh antennomere with distal margin covered by tiny conical setae; last three antennomeres setose (Fig. 8B). Mandibles with stipital lobes evident. Gnathochilarium with stipites slightly swollen distally (Fig. 8A); mentum heptagonal, with deep concavity; long setae marginally on apical part of lamellae linguales and stipites.

COLLUM. Smooth, with only one lateral diagonal furrow; unornamented and very slightly extended in an anterior lateral lobe (Fig. 8C).

BODY RINGS. Mostly smooth, without carinae or granulation (Fig. 8C–D). Prozonites with usual fine ring furrows in anterior part. Metazonites striated, but striation not reaching ozopore level, dorsally smooth. Ozopore situated at mid-length of metazonite. No sigilla. Stigmatal grooves not extended.

TELSON. Preanal ring without process. Anal valves smooth, marginal lips not developed. Subanal scale broad triangular (Fig. 8D).

LEGS. Midbody legs short, ca ¼ of body maximum vertical diameter. With postfemoral and tibial adhesive pads from leg-pair 3 on; pads gradually smaller towards posterior rings. First leg-pair (Fig. 9A): coxosternum subrectangular, with lateral groups of few short setae, surface scattered with tiny setae. Prefemoral process (pfp) long, but not as long as prefemur, subtriangular, surface scattered with tiny setae. Prefemur subrectangular, surface scattered with tiny setae, distally with few short setae. Femur, postfemur, tibia, and tarsus with long setae ventrally. Second leg-pair (Fig. 9B): coxosternum short, smooth. Prefemur slightly compressed dorsoventrally, with paramedian row of large setae; remaining podomeres setose, with long setae ventrally; tarsal claw present. Penes (pn) located at proximal region of second leg-pair, composed of two entirely separate parts with markedly rounded tips extended in short laminar processes also rounded distally; gonopore positioned distally, not setose.

GONOPOD. Sternum short, trapezoidal. Proplica (pp) ca as long as metaplica (mp) (Fig. 9C–D), parallelsided, mesal margin curved; pp constricted basally, swollen and rounded distally, with few very short distal setae (Fig. 9C). Metaplica (mp) not complex (Fig. 9C–D); mesal margin thickened, laterally in contact with pp almost along its entire length; mp excavated distally, where antetorsal process (atp) emerges (Fig. 9C); mesoapical metaplica process (map) swollen, rounded (Fig. 9C–D); distolateral metaplica process (dmp) extended from mp excavation, thickened, pointed, directed diagonally ectad (Fig. 9C–E). Telopodite (tp) long, reaching in length pp when stretched, thickened, with torsion of 360° basally (Fig. 9C–D); tp distally diverging in lamellar branch (ltp) and in seminal branch where solenomere (sl) is located (Fig. 9E); ltp curved over seminal branch, not broad, smooth; seminal groove (sg) running marginally on seminal branch (Fig. 9E); antetorsal process (atp) thickened (Fig. 9C, E), curved over telopodite (tp) and directed posteriorly (Fig. 9E); atp as long as tp; sl arched, pointed, not covered by ltp.

Distribution

Known only from Constitución, Maule Region (Fig. 1).

Remarks

A large difference in the number of body rings has been observed among species of Autostreptus. Autostreptus silvagonzalezi sp. nov. presents 46 rings, while A. chilensis has 58–61, and A. yanezi has 69–74 rings. Although this difference is considerable (almost 30 rings between A. silvagonzalezi and A. yanezi), especially for an endemic, short-range genus, it is based on only a few adults of the former species. In this context, we expect to collect additional specimens, particularly from regions beyond the type locality, to better assess the variation among species of Autostreptus.