Nichima gen. nov. (Alismataceae) based on reproductive structures from the Oligocene-Miocene of Mexico.

Abstract

Alismataceae, a sub-cosmopolitan 28 family with ca. 17 genera 29 and 113 species, is a large group of aquatic plants. Compression/impressions and bio-inclusions in amber support the documentation of the lineage in low-latitude North America. In Mexico, fossil aquatic plants have been infrequently documented. The new flowers recognize a group mainly known through fruits and seeds. Impression/compression reproductive structures from the Oligocene Los Ahuehuetes locality, Puebla, and bio-inclusions from the Miocene amber of Simojovel de Allende, Chiapas, Mexico, known through 150 samples. They are described and compared with extinct and extant taxa. A parsimony analysis based on 29 floral characters of 17 extant genera of the Alismataceae evaluates the relationship between the fossil material and their potential living relatives. Nichima gen. nov. is a perfect, actinomorphic flower with an expanded receptacle, three persistent sepals with multi-vasculature, delicate and caducous petals, six stamens, and gynoecium composed of three to more superior carpels, maturing into achenes. These characteristics resemble flowers of Alismataceae. Nichima represents an extinct member of the family, with two new species, Nichima magalloniae L. Hern., Cevallos-Ferriz et Hernández-Damián sp. nov. and Nichima gonzalez-medranoi L. Hern., Cevallos-Ferriz et Hernández-Damián, sp. nov. Their phylogenetic position suggests affinity with a clade that includes Baldiella, Echinodorus, and Alisma. Reproductive structures from the Cenozoic of Mexico support the identification of a new extinct genus, Nichima, evidencing Alismataceae's extensive history in North America's low latitudes and suggests a southern extension of the Boreotropical Flora. This article is protected by copyright. All rights reserved.