Heinrichsia cheilanthoides gen. et sp. nov., a fossil fern in the family Pteridaceae (Polypodiales) from the Cretaceous amber forests of Myanmar

Abstract

Divergence time estimates suggest that most clades constituting the fern family Pteridaceae (Polypodiales) were in existence by the Early Cretaceous. However, fossil evidence to corroborate this remains exceedingly rare. Burmese amber is an important source of new information on the radiation of derived fern lineages during the Cretaceous Terrestrial Revolution. This study describes Heinrichsia cheilanthoides gen. et sp. nov., a fern with suggested affinities to Pteridaceae, based on fertile foliage portions preserved in Early Cretaceous (~100 Ma) amber from Myanmar. Heinrichsia cheilanthoides is characterized by a pinnate‐pinnatifid frond that bears apical, marginal sori protected by a pseudoindusium. Sporangia are of the polypod type and contain tetrahedral‐globose, trilete spores with a striate perine. This discovery provides a new calibration point to test and refine molecular clock‐based concepts of the evolutionary history of the Pteridaceae. Heinrichsia cheilanthoides further substantiates the suggestion that the Cretaceous forests of Myanmar were home to a rich fern flora.

How diverse were ferns in the Baltic amber forest?

“…five tonnes per year) is excavated from these deposits. Eight fossils of different families within the Polypodiales and many sporangia and spores have been found in Burmese amber (Poinar & Buckley, 2008;Schneider et al, 2016;Regalado et al, 2017aRegalado et al, , 2017bRegalado et al, , 2018Regalado et al, , 2019Li et al, 2018Li et al, , 2019 and several taxa await description. Four fern species were described from Dominican amber, so far (Gómez, 1982;Lóriga et al, 2014;Schneider et al, 2015;Sundue & Poinar, 2016).…”

Selaginella was hyperdiverse already in the Cretaceous

“…Kachin amber, the older variety of the more widely known Burmese amber, originates from the Albian-Cenomanian (c. 100 million years old (Ma)) of Myanmar (for additional information on provenance and age, refer to Supporting Information Notes S1), and presently represents the most important source of three-dimensionally preserved younger Mesozoic terrestrial organisms (plants, animals and microorganisms). More than 1200 species have been formally described, half of those in the last 3 years (Ross, 2019), including some 20 taxa of free-sporing land plants such as liverworts, mosses and ferns (Heden€ as et al, 2014;Heinrichs et al, 2018;Regalado et al, 2019), which makes Burmese amber the most likely source for Cretaceous lycophyte fossils entombed in amber. Recent screening of several collections of Kachin amber has yielded 14 distinct morphologies of fertile Selaginella (Fig.…”

Celebrating Research Devoted to Seed‐Free Land Plants

“…The third aspect is focused on the improved ability to study the evolution of genomes to answer major questions, such as the maintenance of species identity despite introgression and the role of processes shaping the genomic disparity in SFLP. The special issue contains the description of one extant liverwort, Lejeunea heinrichsii (Lee et al, ), and one extinct fern genus, Heinrichsia (Regalado et al, ), that are both new to science and named in memory of Jochen Heinrichs.…”

“…The first set consists of three contributions devoted to the study of the fossil record of SFLP during the Mesozoic and Cenozoic (Mamonto & Ignatov, ; Regalado et al, ; Sadowski et al, ). In recent years, major advances have been achieved in our understanding of the evolutionary history of these plants especially, but not exclusively, by studying amber inclusions.…”

“…Two studies report specific advances in the study of amber fossils. The study by Sadowski et al () provides for the first time a critical review of the fern diversity recovered in Baltic amber, whereas the study by Regalado et al () added a further critical piece to resolve the remarkable fern diversity preserved in Cretaceous Burmese amber inclusions. The study on the bryophyte of the Mesozoic of Transbaikalia (Mamonto & Ignatov, ) expands the exploration of the fossil record to non‐amber fossils of the early Cretaceous and late Jurassic, including the vegetative body of thalloid liverworts and capsules of derived mosses.…”