Publikationsdatum:
2013-01-22
Beschreibung:
The construction of the vertebral column has been used as a key anatomical character in defining and diagnosing early tetrapod groups. Rhachitomous vertebrae--in which there is a dorsally placed neural arch and spine, an anteroventrally placed intercentrum and paired, posterodorsally placed pleurocentra--have long been considered the ancestral morphology for tetrapods. Nonetheless, very little is known about vertebral anatomy in the earliest stem tetrapods, because most specimens remain trapped in surrounding matrix, obscuring important anatomical features. Here we describe the three-dimensional vertebral architecture of the Late Devonian stem tetrapod Ichthyostega using propagation phase-contrast X-ray synchrotron microtomography. Our scans reveal a diverse array of new morphological, and associated developmental and functional, characteristics, including a possible posterior-to-anterior vertebral ossification sequence and the first evolutionary appearance of ossified sternal elements. One of the most intriguing features relates to the positional relationships between the vertebral elements, with the pleurocentra being unexpectedly sutured or fused to the intercentra that directly succeed them, indicating a 'reverse' rhachitomous design. Comparison of Ichthyostega with two other stem tetrapods, Acanthostega and Pederpes, shows that reverse rhachitomous vertebrae may be the ancestral condition for limbed vertebrates. This study fundamentally revises our current understanding of vertebral column evolution in the earliest tetrapods and raises questions about the presumed vertebral architecture of tetrapodomorph fish and later, more crownward, tetrapods.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pierce, Stephanie E -- Ahlberg, Per E -- Hutchinson, John R -- Molnar, Julia L -- Sanchez, Sophie -- Tafforeau, Paul -- Clack, Jennifer A -- England -- Nature. 2013 Feb 14;494(7436):226-9. doi: 10.1038/nature11825. Epub 2013 Jan 13.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉University Museum of Zoology, Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK. spierce@rvc.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23334417" target="_blank"〉PubMed〈/a〉
Schlagwort(e):
Animals
;
*Biological Evolution
;
Extremities/*anatomy & histology
;
*Fossils
;
Phylogeny
;
Spine/*anatomy & histology
;
Synchrotrons
;
Vertebrates/*anatomy & histology
;
X-Ray Microtomography
Print ISSN:
0028-0836
Digitale ISSN:
1476-4687
Thema:
Biologie
,
Chemie und Pharmazie
,
Medizin
,
Allgemeine Naturwissenschaft
,
Physik
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