Fossilized embryos are widespread but the record is temporally and taxonomically biased

Evolution & Development
Philip C J DonoghueJohn E Repetski

Abstract

We report new discoveries of embryos and egg capsules from the Lower Cambrian of Siberia, Middle Cambrian of Australia and Lower Ordovician of North America. Together with existing records, embryos have now been recorded from four of the seven continents. However, the new discoveries highlight secular and systematic biases in the fossil record of embryonic stages. The temporal window within which the embryos and egg capsules are found is of relatively short duration; it ends in the Early Ordovician and is roughly coincident with that of typical "Orsten"-type faunas. The reduced occurrence of such fossils has been attributed to reducing levels of phosphate in marine waters during the early Paleozoic, but may also be owing to the increasing depth of sediment mixing by infaunal metazoans. Furthermore, most records younger than the earliest Cambrian are of a single kind-large eggs and embryos of the priapulid-like scalidophoran Markuelia. We explore alternative explanations for the low taxonomic diversity of embryos recovered thus far, including sampling, size, anatomy, ecology, and environment, concluding that the preponderance of Markuelia embryos is due to its precocious development of cuticle at an embryonic stage, predisposing...Continue Reading

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Citations

Dec 3, 2008·Proceedings of the National Academy of Sciences of the United States of America·Elizabeth C RaffRudolf A Raff
Jan 15, 2008·Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences·Rudolf A Raff
Mar 31, 2006·Proceedings of the National Academy of Sciences of the United States of America·Elizabeth C RaffRudolf A Raff
Nov 2, 2006·Proceedings of the National Academy of Sciences of the United States of America·Guangjun Zhang, Martin J Cohn
Aug 8, 2015·Developmental Dynamics : an Official Publication of the American Association of Anatomists·Chris L OrganTobin L Hieronymus
Nov 17, 2007·Nature Reviews. Genetics·Rudolf A Raff
May 8, 2008·Evolution & Development·Neil J GostlingPhilip C J Donoghue
May 8, 2008·Evolution & Development·Sofia A WennbergGraham E Budd
Aug 11, 2006·Nature·Philip C J DonoghueMarco Stampanoni
Apr 6, 2007·Nature·Leiming YinJie Hu
Apr 3, 2016·Development Genes and Evolution·Daniel Aguilar-HidalgoFernando Casares
May 23, 2018·Proceedings of the National Academy of Sciences of the United States of America·Allison C DaleyStephen Pates
Feb 17, 2021·Nature Communications·Michael SteinerPhilip Donoghue

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