Topper, Timothy P.5; Skovsted, Christian B.6; Peel, John S.4; Harper, David A. T.5
1 Natural History Museum of Denmark, Natural History Museum of Denmark, Faculty of Science, Københavns Universitet2 Natural History Museum of Denmark, Faculty of Science, Københavns Universitet3 Swedish Museum of Natural History4 Uppsala Universitet5 Natural History Museum of Denmark, Faculty of Science, Københavns Universitet6 Swedish Museum of Natural History
A number of lobopodian taxa from the Cambrian display pairs of sclerotized plates symmetrically positioned along the dorsum of the animal, predominantly above the walking appendages. Most genera were described from complete body fossils exquisitely preserved in the famous Cambrian Lagerstatten, but lobopodian phosphatized plates are found worldwide as typical components of Cambrian small shelly fossil assemblages (SSF). Details regarding intraspecific and ontogenetic variation in lobopod plates are elusive, and the lack of details of ornamentation in Lagerstatte specimens does not minimize the problem. We document here an assemblage of well-preserved isolated plates of Onychodictyon sp. from the Lower Cambrian (Cambrian Series 2, Stage 4) of North Greenland. Two specimens exhibit perfectly conjoined plates from successive moults. Details of ornamentation and the outline and profile of the fixed plates are identical, but width and length of the underlying plate are 24% larger. These specimens boost the body of evidence that lobopodians moulted but also show that plate outline and ornamentation did not vary during ontogeny.