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The humerus of Panderichthys in three dimensions and its significance in the context of the fish-tetrapod transition
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
2009 (English)In: Acta Zoologica (Stockholm), ISSN 0001-7272, E-ISSN 1463-6395, Vol. 90, no suppl 1, 297-305 p.Article in journal (Refereed) Published
Abstract [en]

The humerus of Panderichthyshas been considered to represent a transitionalform between that of tetrapodomorph fish such asEusthenopteronandtetrapods such asAcanthostega. The previous description was based onflattened material and was analysed in the context of the few fossils known atthe time. Since then, several new forms have been described such asGogonasus,Tiktaalikand an isolated humerus from the Catskill Formation. The humeralmorphology ofPanderichthys rhombolepisand its interpretation in this newcontext are therefore reassessed with the help of a three-dimensional modelproduced with themimicssoftware based on a computed tomography scan ofan unflattened specimen as well as comparisons with the originally describedmaterial. The humerus ofPanderichthysdisplays a combination of primitive,derived, intermediate and unique characteristics. It is very similar to themorphology ofTiktaalikbut when it differs from it, it is most often morederived despite the more basal phylogenetic position thatPanderichthysoccupies. What emerges from this study is a much more gradual transformationof the humerus morphology from fish to tetrapods and the ability to distinguishautapomorphies more easily. The picture is more complex than previouslybelieved, with many morphological specializations probably reflecting thebreadth of ecological specializations already present at the time.

Place, publisher, year, edition, pages
2009. Vol. 90, no suppl 1, 297-305 p.
Keyword [en]
fish-tetrapod transition, sarcopterygian, humeri, pectoral musculature
National Category
Biological Sciences
Research subject
URN: urn:nbn:se:uu:diva-98908DOI: 10.1111/j.1463-6395.2008.00389.xISI: 000266242000025OAI: oai:DiVA.org:uu-98908DiVA: diva2:201521
Available from: 2009-03-04 Created: 2009-03-04 Last updated: 2011-03-11Bibliographically approved
In thesis
1. The Origin of Tetrapod Limbs and Girdles: Fossil and Developmental Evidence
Open this publication in new window or tab >>The Origin of Tetrapod Limbs and Girdles: Fossil and Developmental Evidence
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Around 375 million years ago, the first tetrapods appeared, marking one of the most important events in vertebrate evolutionary history. The fin to limb transition saw the appearance of fingers and a weight bearing pelvic girdle. While very little research has been done on the evolution of the tetrapod pelvic girdle, a fair amount has been done on the origins of fingers but some aspects remained controversial. A combination of palaeontology, developmental biology and comparative morphology was therefore used in this thesis to better understand the fin to limb transition. The pectoral fin of Panderichthys, a sarcopterygian fish closely related to tetrapods was CT-scanned and modeled in three dimensions and its pelvic girdle and fin were examined with traditional techniques. This information from the fossil record was integrated with comparisons of the development of the Australian lungfish, Neoceratodus forsteri, our closest living fish relative and the axolotl (Ambystoma mexicanum), a salamander representing well the condition of early tetrapods. Development of bone and cartilage was studied through clearing and staining and development of skeletal muscles through immunostaining. In situ hybridizations were performed on the lungfish to study the expression of Hoxd13, associated with the formation of digits in tetrapods.

This work shows that the late expression phase of Hoxd13 is present in Neoceratodus and is associated with the formation of radials. Redescription of the pectoral fin of Panderichthys reveals that distal radials are present, which, in addition to other information, lead us to conclude that digits are not novelties in tetrapods but rather have evolved from the distal radials present in the fins of all sarcopterygian fish. The earliest tetrapods lack a full set of wrist + carpals/ankle + tarsal bones. Here, we propose that this region of the limbs evolved after fingers and toes through an expansion of the region between the proximal limb bones and the digits. As for the pelvic girdle, it is very primitive in Panderichthys but comparison of its development in Neoceratodus and Ambystoma suggest that the ischium evolved through the posterior expansion of the pubis and the ilium, through an elongation of the iliac process already present in sarcopterygian fishes.

The results of this thesis help to better understand the fin to limb transition and show that it is more gradual than previously believed.


Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 53 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 613
National Category
urn:nbn:se:uu:diva-98911 (URN)978-91-554-7448-5 (ISBN)
Public defence
2009-04-09, Lindhalsalen, EBC, Norbyvägen 14, Uppsala, 13:00 (English)
Available from: 2009-03-13 Created: 2009-03-04 Last updated: 2009-04-03Bibliographically approved

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