Euphorbia tanquahuete Sesse & Mocino 1894

Euphorbia tanquahuete Sessé & Mociño (1894: 122).

Neotype (designated here):— MEXICO. Jalisco: barranca of Guadalajara, volcanic ledges, 5000 ft, 8 August 1902, C.G. Pringle 8736 (MEXU no. 1391104!; isoneotypes ARIZ no. 69846!, ARIZ no. 330147!, F no. 202000!, K barcode K000476653 photo!, MICH barcode 1163366!).

Although Martín de Sessé y Lacasta and José Mariano Mociño conducted their botanical exploration of Nueva España, currently Mexico, from 1787 until 1803, their conspectuses on its plants were not published until nearly a century later (McVaugh, 1969). Thus, most of the names that they proposed as new are synonyms of taxa described during the lengthy time between the completion of their manuscript and its actual publication. However, in the case of Euphorbia tanquahuete, they were the first to describe this distinctive tree occurring in the tropical deciduous forests of central and southern Mexico.

Sessé & Mociño mention that their new species inhabits the hills around Guadalajara, Jalisco [‘Habitat in anfractibus Gualalaxarae vicinis’] and is known locally as “tanquahuete ” and “tlaxcalama.” They describe it as tree to 20 feet tall with alternate, short-petiolate, entire, lanceolate leaves with the upper surface glabrous and the lower surface tomentose; six-flowered [six-cyathiate] umbels; and yellow flowers [cyathia] with subrotund petals [involucral glands]. Their description, coupled with the common names, is sufficient to conclude that it is the same taxon that was described a few years later by Altamirano and Rose (1905) as Euphorbia elastica, an illegitimate homonym of E. elastica Jumelle which was published just a few months earlier (see above). Stapf (1907) proposed the replacement name Euphorbia fulva, and for much of the 20th century, Euphorbia fulva was used for this species (e.g., Standley 1923, Dressler 1961). It was only about 30 years ago that Euphorbia tanquahuete began to be applied to this taxon (e.g., Sahagún Godínez et al. 2014, Steinmann 2002, Martínez Gordillo et al. 2002, Vázquez et al. 1995).

According to McVaugh (2000), there are no known specimens of E. tanquahuete collected by Sessé and Mociño. The neotype designated here was collected in the barranca of Guadalajara and certainly represent the same taxon described by Sessé and Mociño.