Ambrysus sonorensis Usinger

(Figs. 37–39)

Ambrysus sonorensis Usinger 1946: Univ. Kans. Sci. Bull. 31: 202–203 (original description).

Diagnosis. Ambrysus sonorensis can be distinguished from others in this section by the symmetrical female SGP with small and narrowly rounded lateral lobes and inconspicuous apical lobes at the base of the middle and apical thirds, respectively. Additionally, the posterolateral corners are short and rounded and the central lobe is poorly developed and shallowly concave medially, giving the appearance of two low and rounded lobes (Fig. 37B). Also, the male phallosoma presents both endosomal sclerites knob-like with conspicuous denticles (Fig. 37E).

Comparative notes. Ambrysus sonorensis and A. altiplanus present the female SGP with low apical lobes, but these lobes are more distinct in A. altiplanus . Also, the SGP rounded posterolateral corners and broad central lobe of A. sonorensis are respectively pointed and narrow in A. altiplanus, and males of A. sonorensis do not have the diagnostic lobe-shaped and granulose sclerotized area of the endosoma present in the phallosoma of A. altiplanus .

Discussion. This species measures 13.43–15.48 in length and 8.50–10.50 in width. Usinger (1946) described this species based on a single male specimen (Fig. 38) from the northern Mexican state of Sonora, hence the etymology of the specific epithet in the species name. In the original description, Usinger assigned this species to the A. signoreti complex, but did not give the features to establish such inclusion. Apparently, this is the first time the A. signoreti complex was mentioned in the literature. La Rivers (1953a) considered it impractical to include this species in his revision of the Ambrysus of Mexico because it was only known from a single male specimen and a key feature used in that work to distinguish the species was the shape of the female SGP. It was not until recently (Reynoso-Velasco 2022), after more than 70 years since the original description, that the female of A. sonorensis was described and the identity of the species clarified.

Variation. Some females exhibit the posterior margin of the SGP with indistinct posterolateral corners. Additionally, in some females the apical third of the SGP can be wider than average, giving it a subquadrate shape.

Type locality. Mexico: Sonora: Mpio. Álamos, Río Mayo at San Bernardo .

Repository. Male holotype (Fig. 38) is housed at the CAS.

Published records: MEXICO: Sinaloa, Sonora (Reynoso-Velasco 2022).

Distribution. This species is distributed in the northwestern part of Mexico, predominantly in the drainage systems with headwaters in the western slopes of the Sierra Madre Occidental mountain range, in the states of Sinaloa and Sonora (Fig. 39). The majority of records are within the northernmost section of the Pacific Lowlands biogeographic province (160–570 meters). A single record situated farthest north is in the Chihuahuan Desert province (1,300 meters) and another in the Sierra Madre Occidental province (1,231 meters). Some localities are in the vicinity of the border with the state of Chihuahua, where the drainage systems in which the species was collected originate; thus, the species most likely is also present in the southwesternmost part of this state.

Type material examined. HOLOTYPE ♂ (by original designation). MEXICO: Sonora: [Mpio. Álamos], San Bernardo, Rio Mayo, 02-III-1935, H.S. Gentry coll.

Additional material examined. MEXICO: Sinaloa: [Mpio. Choix], Rio Choix at Choix, [26º43’58.31’’N, 108º18’52.06’’W], 24-IV-1981, CL1643, J.T.& D.A. Polhemus /J.T.Polhemus Collection2014/C.J.DrakeAccession (1♀ USNM) . Sonora: Mpio. Álamos, Arroyo El Taymuco at El Naranjo, 27°14’43.3’’N, 108°45’27.8’’W, 462 m, L-1682, 25-XII-2013, Reynoso-Velasco coll. (2♂, 3♀ IEXA); Mpio. Álamos, Arroyo La Vinatería at Taymuco (El Vado), 27°14’39.7’’N, 108°43’17.3’’W, 537 m, L-1683, 25-XII-2013, Reynoso-Velasco coll. (2♂, 2♀ IEXA; 9♂, 1♀ UMC); Mpio. Álamos, Río Mayo at Nahuibampo, 27°22’28.8’’N, 108°54’34.4’’W, 158 m, L-1685, 26-XII-2013, Reynoso-Velasco coll. (1♂, 1♀ UMC); [Mpio. Álamos], Upper Rio Mayo [N of San Bernardo, 27º25’30.14’’N, 108º51’26.74’’W], 19-IV-1981, CL1636, J.T. & D.A. Polhemus / J.T. Polhemus Collection 2014 / C.J. Drake Accession (1♂, 1♀ USNM); [Mpio. Bacanora] Rio Bacanora at Bacanora, [28º58’50.02’’N, 109º23’45.90’’W], 24-IV-1982, D.A. & J.T. Polhemus colls. / J.T. Polhemus Collection 2014 / C.J. Drake Accession (7♂, 5♀ USNM); [Mpio. Imuris], 9 mi NNE of Imuris, [30º52’36.41’’N, 110º44’09.39’’W], 7–11-VII-1958, J.D. Alcorn coll. (2♂, 2♀ SEMC); Mpio. Onavas, Arroyo Tepoca at Tepoca, 28°25’50.3’’N, 109°15’26.0’’W, 564 m, L-1691, 27-XII-2013, Reynoso-Velasco coll. (2♂, 2♀ CNIN; 19♂, 18♀ IEXA; 12♂, 10♀ UMC); [Mpio. Rosario de Tesopaco], Arroyo Batella [Río Nuri], on Hwy 11 at junct to Nuri, [28º06’38.25’’N, 109º19’17.07’’W], 18-I-1988, Kondratieff coll. / J.T. Polhemus Collection 2014 / C.J. Drake Accession (1♂ USNM); Mpio. Rosario de Tesopaco, Arroyo Cajón de Amador ca. 6 km N of Nuri, 28°09’50.0’’N, 109°19’37.7’’W, 324 m, L-1689, 27-XII-2013, Reynoso-Velasco coll. (2♂, 5♀ IEXA; 1♂ UMC); [Mpio. San Pedro de la Cueva], Rio Moctezuma, trib. Rio Yaqui, 2 mi N of Batuc, [29º16’50.20’’N, 109º44’03.61’’W], 16-III-1941. R.G. Miller coll. (1♂ UMMZ); [Mpio. Yécora], Arroyo Milpillas [El Encinal] at Tepoca on Hwy 16, [28º25’48.36’’N, 109º15’26.31’’W], 550 m, 20-IV-1988, CL2317, D.A. & J.T. Polhemus colls. / J.T. Polhemus Collection 2014 / C.J. Drake Accession (1♂, 1♀ USNM); [Mpio. Yécora, Río Pedregoso at] 22 mi NE of Yécora, [28º22’33.36’’N, 108º45’38.69’’W], 26-IV-1982, D.A. & J.T. Polhemus colls. / J.T. Polhemus Collection 2014 / C.J. Drake Accession (3♀ USNM) .