Gomphrena caxcana Sandoval-Ortega, Rodríguez-Pérez & Zumaya-Mendoza sp. nov. (Fig. 1 and 2).

Type:— MEXICO. Zacatecas, municipio Atolinga, 800 m al NO de la localidad Cerrito Pelón, aproximadamente a 1.6 km al E de Atolinga, por la carretera a Tlaltenango, 21°49’14.8”N 103°25’49.4”W, vegetación arvense, 2161 m a.s.l., Rodríguez-Pérez 9920 (holotype USON33719!; isotypes CIIDIR!, HUAA!, HZAC!, IBUG!, MEXU!, UAZ!).

Diagnosis (Table 1): — Gomphrena caxcana differs from G. serrata Linnaeus (1753: 224), G. nealleyi Coulter & Fisher (1892: 349–350), and G. haageana Klotzsch (1853: 297–298) by the fleshy perennial taproot (vs. fibrous usually annual root in G. serrata), the presence of adventitious roots (vs. absence of adventitious roots in G. serrata, G. nealleyi, and G. haageana), the length of bractlets (3–4 mm vs. 4.8–7.4 mm in G. serrata, 5.0–7.0 mm in G. nealleyi, and 10–15 mm in G. haageana), the two external tepals slightly sclerotic at base (vs. all tepals sclerotic at base in G. serrata, G. nealleyi, and G. haageana), a differentiation between tepals (the 2 external tepals densely lanate on the midvein, the other 3 tepals sparsely pilose at the base vs. all tepals densely lanate except at the apex in G. serrata, G. nealleyi, and G. haageana), and the structure of staminal tube (with two short apical lobules between anthers vs. staminal tube with a single long apical lobule between anthers in G. serrata and G. haageana or two long apical lobules between anthers in G. nealleyi).

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Description:—Herbs perennial; fleshy taproot up to 12 cm long and 2 cm thick; stems ascending to geniculate or procumbent, 7–30(–45) cm long, branched, reddish, usually forming adventitious roots at the base and the prostrate portion of the stems, which may extend like short rhizomes on flooded soils, pilose, trichomes 1.0– 1.5 mm long, appressed, uniseriate, multicellular. Leaves opposite, arranged along the stem, proximal leaves petiolate, distal leaves sessile to subsessile, petiole 3.0– 10 mm long, leaf blades oblanceolate, oblong-elliptic to ovate-elliptic, 1.0–3.6 × 0.4– 1.2 cm, base long decurrent, margin entire, apex mucronate, adaxial surface glabrous or with some isolated trichomes, abaxial surface sparsely pilose especially on the midvein, trichomes similar to those on stems. Inflorescences globose to shortly spiciform, terminal, solitary or in groups of up to 3, 6.0–9.0 × 6.0– 12 mm, white to pinkish, supported by 2 involucral leaves longer than the inflorescence, 10–12(–15) × 4.0–7.0 mm. Flowers hermaphrodite, bract 1 broadly ovate, membranous, hyaline and glabrous, reaching more or less half the length of the bractlets, 1.8–2.3 × 11.2 mm, middle vein evident, apex acute; bractlets 2, crested, cymbiform, lanceolate, membranous, glabrous, reddish to magenta, same or slightly longer than the tepals, 3.0–4.0 × 1.5–2.0 mm wide, the crest prolonged from the apex to above the middle, 0.3–0.5 mm wide, irregularly toothed; tepals 5, unequal, the 2 external cymbiform, 3.0–4.0 × 0.5– 0.7 mm, 3 oblong-lanceolate, 3.0–3.5(–4.0) × 0.5–0.7 mm, slightly sclerotic at base and membranous towards margin and apex, margin entire, 1-veined, lanate over the midvein, the 3 internal oblong-lanceolate, 3.0–3.5(–4.0) × 0.5–0.7 mm, membranous, sparsely pilose near the base; trichomes white, undulated and simple; androecium with filaments fused into a staminal tube 3.0– 3.5 mm long, with a pair of apical lobes shorter and alternating with the anthers; anthers ca. 0.7 mm long; gynoecium with subglobose ovary, ca. 1.0 mm diameter; style ca. 1.0 mm long; stigma formed by two filiform branches 0.5–1.0 mm long. Fruit a subglobose translucid utricle 1.0– 1.5 mm diameter. Seed 1, oblong, brown, ca. 1.0 mm diameter, testa shiny, reddish brown.

Etymology:—The new species is named after the Caxcanes, an indigenous group who inhabited the southern region of Zacatecas and surrounding areas of Jalisco (Mexico), during the pre-Hispanic era. They were part of the people known as Chichimecas by the Mexica.

Distribution and habitat:— Gomphrena caxcana grows on plains with gentle slopes with reddish clayey soil (i.e. luvisol). It is a rare element in the oak forest secondary vegetation or in natural grasslands. It is also often found in shallow, rain-fed wetlands and on the banks of crops, roads and in urban areas, where it is more common. Distributed in the Sierra Madre Occidental biogeographic province, in the states of Jalisco and Zacatecas (Fig. 3), at 1800–2000 m a.s.l.

Phenology:—Flowering and fruiting times from July to October.

Conservation status:— Gomphrena caxcana is known only for locus classicu (south-western of Zacatecas) plus two other sites in the State of Jalisco. However, it is possible that this species has a wider distribution, since it was collected also in disturbance areas like roadsides and crop fields. So, we think that more extensive filed surveys need to assess its conservation status. Therefore, following the guidelines of the IUCN criteria (IUCN 2025), G. caxcana is here assessed as Data Deficient (DD).

Notes:— At first glance, specimens of Gomphrena caxcana look like G. serrata. However, after consulting the protologue G. serrata (Linnaeus 1753: 224), the neotype designated by Mears (1980: 86–87, i.e. the specimen BM000522330!), as well as material deposited in MEXU and USON matching the current concept of G. serrata (see e.g. Clemants 2003, Zumaya-Mendoza & Sánchez-del Pino 2015), we confirmed that the material here referred to the new species does not correspond to any previously described species of Gomphrena from Mexico.

Additional examined material (paratypes):— MEXICO. Zacatecas: municipio Atolinga, Cerrito Pelón, 21°48’50”N 103°25’18”W, bosque de Quercus, 2079 m, 17 October 2002, Balleza 14497 (UAZ12185). Jalisco: municipio Totatiche, 4.5 km en línea recta al S de Totatiche sobre la carretera que va de Atolinga a Colotlán, 21°53’30.2”N 103°27’19.3”W, vegetación ruderal, 2059 m, 17 August 2025, Rodríguez-Pérez 9962 (USON33718); municipio Lagos de Moreno, Aproximadamente 2 km al Sur de Churintzio, 21°14’31.6”N 102°0’58.7”W, vegetación acuática (humedal de temporal), 1850 m, 22 August 2025, Rodríguez-Pérez 9964 (USON33749); Aproximadamente 2 km al Sur de Churintzio, 21°14’32.1”N 102°0’59.3”W, vegetación acuática (humedal de temporal), 1850 m, 22 August 2025, Rodríguez-Pérez 9965 (USON33748).