The extant moss genus Leucobryum (Bryopsida: Leucobryaceae) from Miocene Zhangpu amber

Abstract

The fossil record of bryophytes from worldwide amber deposits substantially increased within the past decade. Inclusions of mosses have now been described from 15 Cretaceous and Cenozoic amber localities. These fossils stand out by their excellent preservation and are therefore very valuable for divergence time estimates as well as for the reconstruction of the evolution of morphological traits through time. The amber inclusions are three-dimensional and show diminutive details which are crucial for classification of bryophytes. Many moss fossils preserved in amber were convincingly assigned to extant genera and, in the case of Miocene taxa, sometimes even to living species. Here, we describe a fossil Leucobryum from Zhangpu amber of southeastern China. The extant genus Leucobryum comprises between 35 and 83 mainly tropical species and is characterized by a highly modified costa consisting of one layer of small chlorocysts between two layers of large, empty leucocysts. Some leaves of the fossil specimens are broken and show the arrangement of cells typical for extant species. We provide a thorough comparison to extant representatives, however, as several characters necessary for assignment at species level are not accessible in the fossil, it is uncertain whether it represents an extinct or extant species.