A tristichous moss from the Lower Cretaceous (Valanginian) of Vancouver Island, British Columbia, Canada

ADOLFINA SAVORETTI; HOLLISTER C. NADEAU; MAKALANI F. NORMAN; RUTH A. STOCKEY; GAR W. ROTHWELL; ALEXANDRU M. F. TOMESCU

Salvador de Bahía

Congreso; XIV International Palynological Congress - X International Organisation of Paleobotany Conference; 2016

The Early Cretaceous (ca. 136 Ma) Apple Bay flora of Vancouver Island is preserved anatomically by calcium carbonate permineralization, in concretions that host an allochthonous fossil assemblage deposited in nearshore marine sediments. The Apple Bay flora has yielded representatives of most major groups of tracheophytes (lycopodialean and selaginellalean lycopsids, sphenopsids, ten fern families, and several types of gymnosperms), as well as fungi (ascomycetes and basidiomycetes) and a lichen. A wide variety of bryophytes are also present. These make the Apple Bay flora one of the most diverse fossil bryophyte floras worldwide and have broadened significantly the range of biodiversity covered by the generally sparse fossil record of the group. Notable here are polytrichaceous and leucobryaceous mosses, as well as a several types of tricostate mosses, at least some of which have hypnanaean affinities (Tricostaceae). Another bryophyte type identified at Apple Bay has gametophytes characterized by weakly triquetrous stems bearing tristichous, helically arranged, imbricate, and evenly keeled leaves. The leaves are erect and closely spaced, with slightly recurved margins in the upper half. The lamina is unistratose, but can be bistratose near the costa. The strong costa is attenuate and exhibits some differentiation between thicker-walled epidermal cells and thinner-walled internal cells. In the extant flora, select species of some genera or entire genera exhibiting tristichous helical phyllotaxis are known in several moss families, including the Meesiaceae, Seligeriaceae, Polytrichaceae, Bartramiaceae, Catoscopiaceae, Grimmiaceae, Pottiaceae, Fontinalaceae, Amphidiaceae, and Ditrichaceae. Of these, the Apple Bay tristichous moss compares well with Seligeria tristicha (Brid.) Bruch & Schimp. (Seligeriaceae), Anoectangium Schwägr. and Triquetrella C. Müll. (Pottiaceae), Tristichum mirabile (C. Müll.) Herz. (Ditrichaceae), and Plagiopus oederianus H. Crum et L.E. Anderson (Bartramiaceae). A complete description of this moss type and anatomical comparisons with the extant moss species of above families, will allow for more precise taxonomic circumscription of this Apple Bay fossil.