Background:

Chthamalia is a genus of Gonolobinae distinctive by its climbing or creeping habit, its flowers up to two centimeters in diameter and its cyathiform gynostegial corona with generally linear appendages. Eight species have been reported in Mexico, but none of them correspond to the taxon studied in this article.

Questions and/or hypotheses:

What are the characteristics that differentiate the individuals of this taxon with respect to other species of Chthamalia? What is its distribution and conservation status?

Studied species:

Chthamalia tehuacana and morphologically similar species.

Study site and dates:

Tehuacán Valley, Puebla, Mexico, 2021-2022.

Methods:

An intensive search for information related to the genus was carried out and eight herbaria and databases were consulted. A comparative analysis between morphologically similar species was performed. The conservation status of the new species was evaluated following the guidelines of the IUCN. Populations were observed for floral visitors and semi-structured surveys were carried out to know the common names and uses of the taxon.

Results:

The new species Chthamalia tehuacana is described and compared with C. ojadapantha, C. schaffneri, and Matelea pueblensis. Detailed images of the species as well as floral visitors of C. tehuacana are provided. A distribution map is presented and a conservation status of Vulnerable is suggested.

Conclusions:

This contribution enriches the knowledge of Chthamalia in Mexico, which now has nine registered species and increases its level of endemism to 78 %. Likewise, it highlights the high diversity of Apocynaceae in the Tehuacán-Cuicatlán Valley.