Aphonopelma phasmus Chamberlin, 1940

Hamilton, Chris A., Hendrixson, Brent E. & Bond, Jason E., 2016, Taxonomic revision of the tarantula genus Aphonopelma Pocock, 1901 (Araneae, Mygalomorphae, Theraphosidae) within the United States, ZooKeys 560, pp. 1-340 : 215

Taxon classification Animalia Araneae Theraphosidae

Aphonopelma phasmus Chamberlin, 1940 Figures 122, 123

Aphonopelma (Delopelma) phasmus Chamberlin, 1940: 28; male holotype from Phantom Ranch, Grand Canyon, Coconino Co., Arizona, 36.105315 -112.095201, elev. 2536ft., 26.vii.1934, coll. Dr. Lutz; deposited in AMNH. [examined]

Rhechostica phasmus Raven, 1985: 149.

Aphonopelma phasmus Smith, 1995: 129.

Diagnosis.

Based on carapace length (a proxy for body size) and evaluation of morphospace, Aphonopelma phasmus probably belongs to the paloma species group but molecular data is needed to confirm its phylogenetic placement. Although the tip of the embolus is broken, the palpal bulb is unique (Fig. 122) compared to other species found in the region (i.e., Aphonopelma iodius , Aphonopelma marxi , and Aphonopelma prenticei ). The carapace is distinctly more round than Aphonopelma prenticei ; Aphonopelma phasmus possess a larger F3L/W ratio (3.59 ± (only 1 specimen)) than Aphonopelma prenticei (≤3.27; 2.76-3.27), and larger L3 scopulation extent (81.7% ± (only 1 specimen)) than Aphonopelma prenticei (60%-73%). Aphonopelma phasmus can be differentiated from Aphonopelma marxi by comparing the PTl, Cl, and metatarsus measurements; Aphonopelma phasmus possess a smaller PTl/M1 (0.79 ± (only 1 specimen)) than Aphonopelma marxi (≥0.92: 0.92-1.23) and a smaller Cl/M1 (1.21 ± (only 1 specimen)) than Aphonopelma marxi (≥1.43; 1.43-1.89).

Description.

Male originally described by Chamberlin (1940).

Redescription of male holotype

(Fig. 122). Specimen preparation and condition: unknown collecting information; deposited in AMNH; original coloration faded due to preservation. Specimen badly fragmented, with legs stored in vial with specimen; most setae have fallen off over time. Specimen was pieced together for measurements. General coloration: Faded brown. Cephalothorax: Carapace 7.89 mm long, 6.84 mm wide; foveal groove medium deep and straight; pars cephalica region rises gradually from foveal groove to ocular area; AER very slightly procurved, PER straight; normal sized chelicerae; clypeus extends forward on a curve; LBl 1.072, LBw 1.315. Abdomen: Devoid of setae - lost over time. Legs: Metatarsus I very slightly curved. F1 8.88; F1w 1.917; P1 3.598; T1 8.124; M1 6.523; A1 4.773; L1 length 31.898; F3 7.338; F3w 2.046; P3 2.635; T3 5.979; M3 6.902; A3 4.369; L3 length 27.223; F4 8.59; F4w 1.79; P4 2.93; T4missing/damaged; M4missing/damaged; A4missing/damaged; L4 incomplete; femur III is slightly swollen. All tarsi fully scopulate. Extent of metatarsal scopulation: leg III (SC3) = 81.7%; leg IV (SC4) = missing/damaged. Two ventral spinose setae and one prolateral spinose seta on metatarsus III; five ventral spinose setae and one prolateral spinose seta on metatarsus IV; one prolateral spinose seta on tibia I; one large megaspine is present at the apex on the retrolateral tibia of the mating clasper. Coxa I: Prolateral surface covered by thin tapered and fine, hair-like setae. Pedipalps: One spinose seta near the anterior margin of the prolateral palpal femur; three spinose setae on the prolateral palpal tibia (one near the anterior/ventral margin), one ventral spinose seta towards the anterior margin; PTl 5.188, PTw 1.768. Palpal bulb is unique; embolus is broken; distinct ventral transition from bulb to embolus; unique process extending posteriorly.

Distribution and natural history.

Aphonopelma phasmus is known from a single adult male collected at Phantom Ranch (770 meters) near the Colorado River in Grand Canyon National Park in Coconino County, Arizona (Fig. 123); Phantom Ranch is characterized by riparian habitat surrounded by desert. The July collection date for the holotype indicates a summer breeding period for this species. Aphonopelma phasmus is the only species known to inhabit the bottom of Grand Canyon; Aphonopelma marxi is abundant along the South Rim in ponderosa pine forest, some 1300 meters higher in elevation and Aphonopelma prenticei can be found in desert habitats north and west of Grand Canyon.

Conservation status.

Aphonopelma phasmus probably has a very restricted distribution along the Colorado River in Grand Canyon National Park. Although the species is protected by the boundaries of the park, the Phantom Ranch area is prone to habitat degradation due to foot traffic and other recreational activities. New collecting efforts to find this species need to be taken before its conservation status can be assessed.

Species concept applied.

Morphological Species Concept.

Remarks.

Very little is known about this enigmatic species. Despite our extensive fieldwork throughout Arizona and surrounding areas, we have not encountered any other specimens that appear to be conspecific with Aphonopelma phasmus . Focused collection efforts at Phantom Ranch and other locations along the Colorado River are necessary to fully grasp the validity of this species and to determine its phylogenetic placement. A handful of measurements demonstrate that Aphonopelma phasmus likely is not conspecific with other species in the surrounding area (i.e., Aphonopelma iodius , Aphonopelma marxi , and Aphonopelma prenticei ) but new material is needed to confirm this hypothesis. Unfortunately, the holotype is badly damaged, fragmented, and missing multiple pieces, and because we lack more specimens, we are not able to understand the possible morphological variation that exists within this species. During evaluation of traditional PCA morphospace and three-dimensional PCA morphospace (PC1~PC2~PC3), Aphonopelma phasmus groups with the other species in the paloma species group (see Suppl. material 2).