In the version of this article initially published, Tomas Marques-Bonet was missing the following affiliations: Catalan Institution of Research and Advanced Studies (ICREA), Barcelona, Spain; CNAG-CRG, Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology (BIST), Barcelona, Spain; and Institut Català de Paleontologia Miquel Crusafont, Universitat Autònoma de Barcelona, Barcelona, Spain. The affiliations have been added in the PDF and HTML versions of the article.