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Three-dimensionally preserved minute larva of a great-appendage arthropod from the early Cambrian Chengjiang biota

PNAS 113: 5542-6. doi: 10.1073/pnas.1522899113. Epub 2016 May 2.

Authors/Editors: Liu Y
Melzer RR
Haug JT
Haug C
Briggs DE
Hörnig MK
He YY
Hou XG
Publication Date: 2016
Type of Publication: Journal Articles 2001 - 2017

Abstract

A three-dimensionally preserved 2-mm-long larva of the arthropodLeanchoilia illecebrosa from the 520-million-year-old earlyCambrian Chengjiang biota of China represents the first evidence,to our knowledge, of such an early developmental stage in a shortgreat-appendage (SGA) arthropod. The larva possesses a pair ofthree-fingered great appendages, a hypostome, and four pairs ofwell-developed biramous appendages. More posteriorly, a series of rudimentary limb Anlagen revealed by X-ray microcomputedtomography shows a gradient of decreasing differentiation toward the rear. This, and postembryonic segment addition at the putative growth zone, are features of late-stage metanauplii of eucrustaceans. L. illecebrosa and other SGA arthropods, however, are considered representative of early chelicerates or part of the stem lineage of all euarthropods. The larva of an early Cambrian SGA arthropod with a small number of anterior segments and their respective appendages suggests that posthatching segment addition occurred in the ancestor of Euarthropoda.