Nineteen species of Leptodontium are recognized for the New World. The genus is divided into four sections, including two new species. Critical characters of taxonomic importance, such as stem and costal anatomy, and laminal papillae morphology, are described in detail. The species are mainly found in mountainous areas, on various substrates. Several species are disjunct from the New World to Africa, while two species are essentially pan-tropical in distribution. Leptodontium (Pottiaceae) is a genus of mosses with wide distribution in the tropics and subtropics. Most of the species have been described from South America. At the beginning of the present study, there were 92 validly published species or valid combinations in the genus reported from the New World. Leptodontium in its American range was selected for revision on account of the need for careful evaluation of the numerous poorly defined species described for the area. Except as treated in certain regional floras, the genus has not previously been revised. Heretofore, taxonomic treatments of species of Leptodontium have emphasized rather variable gross morphological characters, such as color and habit of the plants, and the size and shape of the leaves, resulting in problems with identification. Microscopic features of the stem, leaf areolation, papillae, and costal structure, which I consider critical to analysis of genetic relationships in the genus, have been seldom used or ignored.
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Richard H. Zander (1972) studied this question.