The anatomy, affinity, and phylogenetic significance of Markuelia: The fossil record provides a paucity of data on the development of extinct organisms, particularly for their embryology. The recovery of fossilized embryos heralds new insight into the evolution of development but advances are limited by an almost complete absence of phylogenetic constraint. Markuelia is an exception to this, known from cleavage and pre-hatchling stages as a vermiform and profusely annulated direct-developing bilaterian with terminal circumoral and posterior radial arrays of spines. Phylogenetic analyses have hitherto suggested assignment to stem-Scalidophora (phyla Kinorhyncha, Loricifera, Priapulida). We test this assumption with additional data and through the inclusion of additional taxa. The available evidence supports stem-Scalidophora affinity, leading to the conclusion that scalidophorans, cyclonerualians, and ecdysozoans are primitive direct developers, and the likelihood that scalidophorans are primitively metameric.

Xi-Ping Dong, PCJ Donoghue, J Cunningham, J Liu, H Cheng

Research output: Contribution to journalArticle (Academic Journal)peer-review

59 Citations (Scopus)
Translated title of the contributionThe anatomy, affinity, and phylogenetic significance of Markuelia
Original languageEnglish
Pages (from-to)468-482
Number of pages15
JournalEvolution and Development
Issue number5
Publication statusPublished - Sept 2005

Bibliographical note

Publisher: Blackwell

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