The Early Cretaceous Apple Bay flora of Vancouver Island: a hotspot of fossil bryophyte diversity

Abstract

Abstract:The pre-Cenozoic bryophyte fossil record is significantly sparser than that of vascular plants or Cenozoic bryophytes. This situation has been traditionally attributed to a hypothesized low preservation potential of the plants. However, instances of excellent pre-Cenozoic bryophyte preservation and the results of experiments simulating fossilization contradict this traditional interpretation, suggesting that bryophytes have good preservation potential. Studies of an anatomically preserved Early Cretaceous (Valanginian) plant fossil assemblage on Vancouver Island (British Columbia), at Apple Bay, focusing on the cryptogamic flora, have revealed an abundant bryophyte component. The Apple Bay flora hosts one of the most diverse bryophyte assemblages worldwide, with at least nine distinct moss types (polytrichaceous, leucobryaceous, tricostate), one complex thalloid liverwort, and two other thalloid plants (representing bryophyte or pteridophyte gametophytes), which contribute a significant fraction of biodiversity to the pre-Cenozoic fossil record of bryophytes. These results (i) corroborate previous observations and studies, indicating that the preservation potential of bryophytes is much better than traditionally thought; (ii) indicate that the bryophyte fossil record is incompletely explored and many more bryophyte fossils are hidden in the rock record, awaiting discovery; and (iii) suggest that the paucity of the pre-Cenozoic bryophyte fossil record is primarily a reflection of inadequate paleobryological capacity.Key words: fossil, bryophyte, moss, Cretaceous, anatomy, permineralized.Résumé : Le registre des bryophytes fossiles du pré-Cénozoïque est significativement plus mince que celui de plantes vasculaires ou de bryophytes du Cénozoïque. Cette situation a été traditionnellement attribuée à un hypothétique faible potentiel de préservation de ces plantes. Cependant, des exemples d'une excellente préservation de bryophytes du pré-Cénozoïque et les résultats d'expériences simulant la fossilisation contredisent cette interprétation traditionnelle, suggérant que les bryophytes ont un bon potentiel de préservation. Des études d'un assemblage de plantes fossiles anatomiquement préservées du Crétacé inférieur sur l'Ile de Vancouver (Colombie Britannique), à Apple Bay, se concentrant sur la flore cryptogame, ont révélé une composante importante de bryophytes. La flore d'Apple Bay comporte un des assemblages de bryophytes les plus diversifiés dans le monde, avec au moins neuf types distincts de mousses (Polytrichacées, Leucobryacées, mousses tricostées), une hépatique thalloïde complexe et deux autres plantes thalloïdes (représentant des gamétophytes de bryophyte ou de ptéridophyte), qui contribuent à une fraction significative de la biodiversité du registre des bryophytes fossiles du pré-Cénozoïque. Ces résultats (i) corroborent les observations et les études antérieures indiquant que le potentiel de préservation des bryophytes est beaucoup meilleur qu'initialement présumé; (ii) indiquent que le registre de...

Wanted dead or alive (probably dead): Stem group Polytrichaceae

“…The most expedient source for this type of data would be discovery of a stem group member of the family, either in the modern biota or, more likely, in the fossil record. Recently, several Cretaceous and Jurassic Polytrichaceae have been discovered in Europe, North America, and South America and await description (Tomescu, 2016;Tomescu et al, in press). Because the current paucity of fossil bryophytes is probably due to incomplete exploration of the fossil record and to the dearth of bryological expertise in the paleontological community, these recent discoveries predict that there are more Mesozoic fossil Polytrichaceae still undiscovered, some of which are stem group members of the family.…”

“…Additionally, rooting the phylogeny of Polytrichaceae with a member of the family (Alophosia) does not allow for empirical testing of the phylogenetic relationships of extinct polytrichaceous mosses that may be more basal members of the family (and are much older) than Alophosia. Recently, three previously unknown fossil Polytrichaceae that are morphologically similar to basal members of the family (Alophosia, Bartramiopsis, Lyellia, Meantoinea) have been discovered in the Early Cretaceous of Vancouver Island (Canada) and northern California (Tomescu, 2016), and in the Middle Jurassic of Argentina (Tomescu et al, in press). These taxa await description and phylogenetic assessment.…”

A Burmese amber fossil of <i>Radula</i> (Porellales, Jungermanniopsida) provides insights into the Cretaceous evolution of epiphytic lineages of leafy liverworts

“…& Robison, Schuster and Janssens, 1989). Cretaceous fossils of thallose liverworts are more numerous but generally poorly preserved (Fletcher et al, 2008;Li et al, 2014Li et al, , 2016Tomescu, 2016) and can hardly be aligned with extant genera or families (Laenen et al, 2014;Villarreal et al, 2016). Considering the importance of the Cretaceous for the evolution of epiphytic lineages of liverworts and our scarce knowledge on the morphology of these plants, an extension of the Cretaceous fossil record of liverworts is very desirable.…”

How to rely on the unreliable: Examples from Mesozoic bryophytes of Transbaikalia

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