Type: MEXICO. Sonora. Mpio. de Alamos: Arroyo Las Rastras, SW edge of the Sierra de Alamos, 26°56′N, 109°3′30″W, 300 m elevation, in tropical deciduous forest understory, 9 Dec 1993, T. R. Van Devender, R. López-E. & D. A. Yetman 93-1457A (Holotype, Tex).

Suffrutex caulibus pilosis glabrescentibus, laminis foliorum ovato-crenatis, petiolis tenuibus quam laminas subaequantibus, stipulis filiformibus, pedicellis axillaribus quam petiolos brevioribus, involucellis destitutis, calyce pilosi, petalis flavis; fructis 7–8-lobatis.

Subshrub of indeterminate height (specimen apparently grazed); young stems pilose, the hairs whitish, 0.5–1 mm long, soon glabrescent. Leaf Blades ovate-cordate, 2–3.5 cm long, 2–2.5 cm wide, prominently and coarsely crenate, acute or acuminate, discolorous (at least when young), the lower surface felted-pubescent when young, the upper surface sparsely pubescent (hairs appressed), the climax leaves more or less concolorous and green, the pubescence scattered; petioles 2–3.5 cm long, very slender (0.25 mm diameter), pilose like stem; stipules filiform, 3 mm long, sparsely pilose. Inflorescence with flowers on pedicels solitary in the leaf axils, 1.5–2 cm long, articulated ca. 5 mm below the flower, sparsely pilose above the articulation; involucel absent; calyx (in bud) prominently and densely pilose, ca. 4 mm long, ca. half-divided; petals yellow, 7–8 mm long, evidently glabrous; staminal column 2.5 mm long, pallid, glabrous, the filaments 1–1.5 mm long, inserted at apex of column, the anthers yellow, numerous (ca. 20?). Fruit ca. 8 mm in diameter, radiately 7–8-lobed, subglabrous; mericarps 7–8, slightly shorter than the calyx lobes, slightly dehiscent but not fully mature.

Batesimalva Fryxell (Fryxell, 1975, 1988a) is a small neotropical genus now including five species. Four of these occur in northern Mexico and one (B. killipii Krapov. ex Fryxell) in Venezuela. The Venezuelan species (Fryxell, 1985), however, has a chromosome number (2n = 24) that is different from that of the two Mexican species that are currently cytologically known (2n = 32) and it is therefore possibly not congeneric with them (Fryxell and Stelly, 1993). It was initially placed in the genus Batesimalva because of the nature of fruit morphology, but this placement is now doubtful because of the differing chromosome number as well as other morphological differences. The correct generic placement of B. killipii is a problem yet to be resolved, especially since the base chromosome number (x = 12) is a relatively unusual one for the Malvaceae.

Batesimalva is distinguished generically by the conformation of the fruit and its constituent mericarps. Species of Batesimalva have an internal endoglossum in the mericarp that is variably developed. In B. pulchella Fryxell it nearly covers the lower cell of the mericarp and confines the solitary seed; in B. violacea (Rose) Fryxell the lower cell is partially covered; in B. lobata Villarreal-Quintanilla & Fryxell it is greatly reduced; and its nature is unknown in the new species. The fruit and mericarps are well illustrated in Fryxell (1975, Fig. 1) and Villarreal-Quintanilla and Fryxell (1990, Fig. 1). Batesimalva bears some resemblance in fruit morphology to Briquetia Hochr., Dirhamphis Krapov., Horsfordia A. Gray, and Fryxellia D. M. Bates, but the relationships among these genera remain problematical (Fryxell, 1997) and some realignment of generic boundaries is probably in order. A connection between Batesimalva and Fryxellia D. Bates remains plausible with consonant chromosome numbers of 2n = 32 and 2n = 16, respectively, and such a connection is given weak support by the ITS sequence data of Tate et al. (2005). The close alliance of Batesimalva to Neobrittonia indicated by the ITS data is contrary to the morphological evidence, although the two genera do share the same base chromosome number (x = 16).

The remaining four species (with the exclusion of Batesimalva killipii) are compared in Table 1 and in the following key. The new species is distinguished most notably by its yellow corolla, small calyx, and evident stipules, as well as by its Sonoran distribution.

Type: UNITED STATES. Texas: Hidalgo County: near La Sal del Rey, on roadside, 7 Jul 2005, A. Richardson & K. King 3239 (Holotype: TEX; Isotype: RUNYON, n.v.).

Suffrutices erecti ramificantes, caulibus tenuis obscure pubescentibus, laminis foliorum discoloribus plerumque quam 3.5 cm longis parvioribus, floribus fructibusque in racemis vel paniculis terminalibus dispositis, pedicellis tenuis 2–3 cm longis, calyce 3–5 mm longi lobis apiculatis, corollis luteo-aurantiacis, fructibus 7–9 mm longis, calycem excedentibus, mericarpiis 5, bulboso-apiculatis.

Erect branched Subshrubs, ca. 1 m tall, the stems slender, minutely and obscurely stellate-pubescent, the hairs scattered, brownish, persistent. Leaf blades ovate, more or less cordate, acute or subobtuse, 2.5–3.5 cm long, 2–2.5 cm wide (smaller upward), discolorous, the margins (in sicco) somewhat undulate (seemingly crenate but actually entire), curved; petioles 1–1.5 (-2) cm long, with pubescence like stem although somewhat denser; stipules minute, early deciduous. Inflorescence a terminal raceme or panicle surpassing the foliage; the pedicels axillary, slender, 2–3 cm long, articulated ca. 5 mm below the flower, minutely stellate-pubescent, more densely so above the articulation; involucel absent; calyx 3–5mm long, ca. half-divided, the lobes short-apiculate, the midribs obscure but sometimes raised distally; corolla ca. 5 mm long, seen only in bud (when yellow, but collectors' note: “flowers orange color, with a reddish ring about 1 mm from the base, leaving an orange colored inner ring”). Fruits exceeding the calyx, 7–9 mm long, minutely and obscurely pubescent; mericarps 5, distally bulbousapiculate, divided into lower and upper cells by a relatively obscure constriction, the lower cell indehiscent, 1-seeded, the upper cell dehiscent, with 2 collateral seeds, the seeds blackish, 2.5 mm long, minutely pubescent.

Additional Specimen Examined: UNITED STATES. Texas: Hidalgo Co.: Tres Corales Reserve (Nature Conservancy), at intersection of Linn-Raymondville hwy. and Sal del Rey road, locally common in disturbed sites, 13 Oct 1985, A. D. Zimmerman & J. Poole 2303 (Paratype: TEX).

The genus Wissadula was treated comprehensively by Fries (1908) but now needs a modern revision. The majority of species are South American (some of which are now pantropical weeds) and only a few species reach as far north as Mexico and the southern United States (Fryxell 1988b). The new species is distinguished from other species of Wissadula by its smaller leaves, obscure stipules, and the relatively obscure constriction in the center of the mericarp. It is similar in the latter characteristic to W. contracta (Link) R. E. Fries, but is very different from it in most other characters and thus not to be confused with it.

The new species cannot be accommodated among the four species previously known from Mexico, Wissadula contracta, W. excelsior (Cav.) C. Presl, W. hernandioides (L'Hé r.) Garcke (as W. amplissima (L.) sensu R. E. Fr.), and W. periplocifolia (L.) Presl ex Thwaites (Fryxell, 1988b), and does not match the two heretofore reported from the United States, W. periplocifolia and W. hernandioides. It should be noted that most authors (including Fryxell, 1988b and Correll & Johnston, 1970) followed the usage of Fries (1908) in giving the name Wissadula amplissima (L.) R.E. Fr. to the plant that is common in Mexico and southern Texas (and elsewhere), until Krapovickas (1996) pointed out that this name correctly applies to a different Central American species and that the name Wissadula hernandioides should be used instead. The following key presents the distinctions.