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Earliest ontogeny of Early Palaeozoic Craniiformea: implications for brachiopod phylogeny

2009; Wiley; Volume: 43; Issue: 3 Linguagem: Inglês

10.1111/j.1502-3931.2009.00197.x

1502-3931

Leonid E. Popov, Michael G. Bassett, Lars E. Holmer, Christian B. Skovsted, Michael Zuykov,

Paleontology and Evolutionary Biology

LethaiaVolume 43, Issue 3 p. 323-333 Earliest ontogeny of Early Palaeozoic Craniiformea: implications for brachiopod phylogeny LEONID E. POPOV, LEONID E. POPOVSearch for more papers by this authorMICHAEL G. BASSETT, MICHAEL G. BASSETTSearch for more papers by this authorLARS E. HOLMER, LARS E. HOLMERSearch for more papers by this authorCHRISTIAN B. SKOVSTED, CHRISTIAN B. SKOVSTEDSearch for more papers by this authorMICHAEL A. ZUYKOV, MICHAEL A. ZUYKOVSearch for more papers by this author LEONID E. POPOV, LEONID E. POPOVSearch for more papers by this authorMICHAEL G. BASSETT, MICHAEL G. BASSETTSearch for more papers by this authorLARS E. HOLMER, LARS E. HOLMERSearch for more papers by this authorCHRISTIAN B. SKOVSTED, CHRISTIAN B. SKOVSTEDSearch for more papers by this authorMICHAEL A. ZUYKOV, MICHAEL A. ZUYKOVSearch for more papers by this author First published: 03 August 2010 https://doi.org/10.1111/j.1502-3931.2009.00197.xCitations: 8 Leonid E. Popov, [[email protected]] and Michael G. Bassett, [[email protected]], Department of Geology, National Museum of Wales, Cathays Park, Cardiff CF10 3NP, Wales, UK; Lars E. Holmer, [[email protected]] and Christian B. Skovsted, [[email protected]], Department of Earth Sciences, Palaeobiology, Uppsala University, SE-752 36 Uppsala, Sweden and Michael A. Zuykov [[email protected]], G. Khlopin Radium Institute 28, 2-nd Murinskiy ave., St Petersburg, 194021, Russia; Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Abstract Popov, L.E., Bassett, M.G., Holmer, L.E., Skovsted, C.B. & Zuykov, M.A. 2010: Earliest ontogeny of Early Palaeozoic Craniiformea: implications for brachiopod phylogeny. Lethaia, Vol. 43, pp. 323–333. Well preserved specimens of the Early Palaeozoic craniiform brachiopods Orthisocrania and Craniops retain clear evidence of a lecithotrophic larval stage, indicating the loss of planktotrophy early in their phylogeny. The size of the earliest mineralized dorsal shell was <100 μm across, and the well preserved shell structure in these fossil craniiforms allows their earliest ontogeny to be compared directly with that of living Novocrania, in which the first mineralized dorsal shell (metamorphic shell) is secreted only after settlement of the lecithotrophic larvae. Immediately outside this earliest shell (early post-metamorphic or brephic shell) and in the rest of the dorsal valve the primary layer in both fossil and living craniiforms has characteristic radially arranged laths, which are invariably lacking in the earliest dorsal shell. The ventral valve of the fossil specimens commonly preserves traces of an early attachment scar (cicatrix), which is equal in size to the dorsal metamorphic shell, and the brephic post-metamorphic ventral valve also has a primary shell with radially arranged laths. However, a primary shell with radial laths is completely lacking in the ventral valve of living Novocrania, indicating that heterochrony may have been involved in the origin of the encrusting mode of life in living craniids; the entire ventral valve of Recent craniids (with the possible exception of Neoancistrocrania) may correspond to the earliest attachment scar of some fossil taxa such as Orthisocrania. It is also probable that the unique absence of an inner mantle lobe as well as the absence of lobate cells in Novocrania could be the result of heterochronic changes. The dorsal valve of both fossil and living craniiforms has a marked outer growth ring, around 500 μm across, marking the transition to the adult, and a significant change in regime of shell secretion. The earliest craniiform attachment is considered to be homologous to the unique attachment structures described recently in polytoechioids (e.g. Antigonambonites) and other members of the strophomenate clade. However, unlike the craniiforms, polytoechioids and strophomenates all have planktotrophic larvae, and planktotrophy is most probably a plesiomorphic character for all Brachiopoda. □Brachiopoda, Craniiformea, Early Palaeozoic, ontogeny, phylogeny. Citing Literature Volume43, Issue3September 2010Pages 323-333 RelatedInformation