title: Fossilized nuclei and chromosomes reveal 180 million years of genomic stasis in royal ferns.
abstract: Rapidly permineralized fossils can provide exceptional insights into the evolution of life over geological time. Here, we present an exquisitely preserved, calcified stem of a royal fern (Osmundaceae) from Early Jurassic lahar deposits of Sweden in which authigenic mineral precipitation from hydrothermal brines occurred so rapidly that it preserved cytoplasm, cytosol granules, nuclei, and even chromosomes in various stages of cell division. Morphometric parameters of interphase nuclei match those of extant Osmundaceae, indicating that the genome size of these reputed "living fossils" has remained unchanged over at least 180 million years-a paramount example of evolutionary stasis.
authors.affiliation: Department of Palaeobiology, Swedish Museum of Natural History, Post Office Box 50007, SE-104 05 Stockholm, Sweden.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Bomfleur
authors.forename: Stephen
authors.initials: S
authors.lastname: McLoughlin
authors.forename: Vivi
authors.initials: V
authors.lastname: Vajda
mesh_terms: D005075:Biological Evolution; D002467:Cell Nucleus / Q000648:ultrastructure*; D032461:Chromosomes, Plant / Q000648:ultrastructure*; D029624:Ferns / Q000235:genetics* / Q000648:ultrastructure; D005580:Fossils; D018745:Genome, Plant; D013548:Sweden; D013995:Time