Fossil pleurocarpous mosses

The undoubted pleurocarps, however, are almost absent or at least extremely rare in earlier deposits. This fact, along with the other evidence, leads to the tentative conclusion (e.g.. Buck, 1991), that the evolution of pleurocarps followed the habitat diversification of the angiosperms, i.e., occurred in the Cretaceous. At the same time, an analysis of fossil data lead Krassilov and Schuster (1984) to the conclusion that the pleurocarpous mosses appeared no earlier than the Jurassic. 

It must also be noted that, if the fossil record accurately reflects the diversity of terrestrial ecosystems, the dense, complex angiosperm forests that we currently know, with their rich diversity of habitats, would have appeared relatively late in the process of diversification of angiosperm lineages (Behrensmeyer, 1992) further emphasizing the uncoupling of pleurocarpous moss diversification from... 

Selected Palaeozoic and Mesozoic mosses are discussed, focusing on their possible relationships to pleurocarpous groups. Among thm. Palaeozoic, Triassic and some Jurassic fossils are similar to pleurocarps in some respects, but some other peculiarities of these mosses make their immediate placement into extant groups difiScult. One new genus and species, Palaeodichelyma sinitzae, is described from the Upper Jurassic of Transbaikalia. This fossil moss is probably the most similar to pleurocarps among the pre-Cenozoic fossils. 

The majority of the moss fossil record cannot provide us with useful information about the possible ages of nodes, for the most part being too recent or too poorly characterized to be used as constraints or to contribute much to our understanding of the timing and sequence of evolutionary events (Krassilov and Schuster, 1984 Miller, 1984). However, our age estimates can possibly suggest something about our interpretation of the fossils. Only fossils credibly considered to be pleurocarpous are discussed here (see also Ignatov and Shcherbakov, Chapter 16). 

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