Phylogeny and Morphology Unveil a New Species of <i>Macropsychanthus</i> (Leguminosae-Papilionoideae) Bridging Its Two Subgenera: Implications for Infrageneric Classification

Abstract— Macropsychanthus currently comprises 51 species and is divided into two subgenera, M. subg. Macropsychanthus and M. subg. Platylobium , which are distinguished by a combination of morphological traits and supported by molecular data. However, certain species present morphological features typical of M. subg. Platylobium despite their phylogenetic placement within M. subg. Macropsychanthus . During our comprehensive revision of Macropsychanthus in the Neotropics, we discovered a new species, here named Macropsychanthus echidna . Phylogenetic analyses based on nuclear ITS/ETS and plastid trnK/matK markers recovered it within M. subg. Macropsychanthus . Nevertheless, the species displays traits such as triangular, basifixed stipules; exstipellate leaflets with 7‐9 pairs of secondary veins; and slightly obovate pods, all features typically associated with M. subg. Platylobium . Together with Macropsychanthus huberi , this is the second species assigned to M. subg. Macropsychanthus that displays a morphology largely aligned with M. subg. Platylobium , thereby challenging the validity of maintaining the current subgeneric delimitation. The short, oblong hilum of the seed remains the only consistent morphological feature distinguishing M. subg. Platylobium .