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Vegavis iaaiFossil, Fossil Bird
Dr. Julia Clarke - North Carolina State University
C. P. Tambussi, J. I. Noriega, G. M. Erickson, and R. A. Ketcham
Vegavis iaai
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skull
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Museo de La Plata, Argentina (MLP 93-I-3-1)

Image processing: Dr. Richard Ketcham
Publication Date: 21 Jan 2005

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Clarke, J. A., C. P. Tambussi, J. I. Noriega, G. M. Erickson, and R. A. Ketcham. 2005. Definitive fossil evidence for the extant avian radiation in the Cretaceous. Nature 433:305-308.

Abstract

Long-standing controversy surrounds the question of whether living bird lineages emerged after non-avian dinosaur extinction at the Cretaceous/Tertiary (K/T) boundary or whether these lineages coexisted with other dinosaurs and passed through this mass extinction event. Inferences from biogeography and molecular sequence data project major avian lineages deep into the Cretaceous period, implying their ‘mass survival’ at the K/T boundary. By contrast, it has been argued that the fossil record refutes this hypothesis, placing a ‘big bang’ of avian radiation only after the end of the Cretaceous. However, other fossil data—fragmentary bones referred to extant bird lineages have been considered inconclusive. These data have never been subjected to phylogenetic analysis. Here we identify a rare, partial skeleton from the Maastrichtian of Antarctica as the first Cretaceous fossil definitively placed within the extant bird radiation. Several phylogenetic analyses supported by independent histological data indicate that a new species, Vegavis iaai, is a part of Anseriformes (waterfowl) and is most closely related to Anatidae, which includes true ducks. A minimum of five divergences within Aves before the K/T boundary are inferred from the placement of Vegavis; at least duck, chicken and ratite bird relatives were coextant with non-avian dinosaurs.

Slice Movies:

Primary bone-bearing slab - scan 1 (4.0mb)

Primary bone-bearing slab - scan 2 (3.8mb)

Counter slab (6.2mb)

Color animation through reconstruction of realigned datasets (3.7mb)

Additional imagery on the UTCT website

About the Species

The Vegavis iaai holotype specimen from Vega Island, is a disarticulated partial postcranial skeleton preserved in two halves of a concretion. This specimen from western Antarctica, was discovered in 1992 and received rudimentary preparation that, in fact, degraded delicate bones that were originally exposed. Significant new preparation, X-ray computed tomography (CT) and recovery of latex peels of the specimen before its original preparation reveal numerous, previously unknown bones and anatomical details.

About this Specimen

The principal bone-bearing half of the specimen was scanned twice using the high-energy subsystem at the UT CT Facility, using X-ray settings of 420 kV and 4.7 mA. First the specimen was surrounded by garnet sand and scanned horizontally with a slice thickness of 1.0 mm and spacing of 0.5 mm in the principal bone-bearing layer and 1.0 mm below. X-ray settings were 420 kV and 4.7 mA. This protocol provided data relatively free of beam-hardening artifacts but with relatively low resolution. The second scan was done at 0.25 mm slice thickness and spacing with the specimen oriented so that its short axis was parallel to the scan plane. Beam-hardening artifacts, including uneven attenuation values, rings, and streaks, were ameliorated through pre-processing of the raw scan data and post-processing of the reconstructed images. The counter-slab was also scanned with the second protocol.

About the
Scan

Literature

Chinsamy, A. 2002. Bone microstructure of early birds; pp. 421-431 in L. M. Chiappe, and L. M. Witmer (eds.), Mesozoic Birds: Above the Heads of Dinosaurs, University of California Press, Berkeley, California.

Clarke, J., and M. Norell. 2002. The morphology and phylogenetic position of Apsaravis ukhaana from the Late Cretaceous of Mongolia. American Museum Novitates 3387:1-47.

Cooper, A., and R. Fortey. 1998. Evolutionary explosions and the phylogenetic fuse. Trends in Ecology and Evolution 13:151-156.

Cooper, A., and D. Penny. 1997. Mass survival of birds across the Cretaceous-Tertiary boundary: molecular evidence. Science 275:1109-1113.

Cracraft, J. 2001. Avian evolution, Gondwana biogeography and the Cretaceous-Tertiary mass extinction event. Proceedings of the Royal Society of London, B, 268:459-469.

Dyke, G., and M. van Tuinen. 2004. The evolutionary radiation of modern birds (Neornithes): reconciling molecules, morphology, and the fossil record. Zoological Journal of the Linnean Society 141:153-177.

Ericson, P. 1999. New material of Juncitarsus (Phoenicopteridae), with a guide for differentiating that genus from the Presbyornithidae (Aves: Anseriformes). Smithsonian Contributions in Paleobiology 89:245-251.

Ericson, P. 2000. Systematic revision, skeletal anatomy, and paleoecology of the New World early Tertiary Presbyornithidae (Aves: Anseriformes). PaleoBios 20:1-23.

Ericson, P. G. P., L. Christidis, A. Cooper, M. Irestedt, J. Jackson, U. S. Johansson, and J. A. Norman. 2002. A Gondwanan origin of passerine birds supported by DNA sequences of the endemic New Zealand wrens. Proceedings of the Royal Society of London, B, 269:235-241.

Fedducia, A. 1995. Explosive evolution in Tertiary birds and mammals. Science 267:637-638.

Feduccia, A. 2003. 'Big bang' for Tertiary birds? Trends in Ecology and Evolution 18:172-176.

Francillon-Viellot, H., et al.. 1990. pp. 471-530 in J. G. Carter (ed.), Skeletal Biomineralization: Patterns and Evolutionary Trends, Van Nostrand Reinhold, New York.

Groth, J., and G. Barrowclough. 1999. Basal divergences in birds and the phylogenetic utility of the nuclear RAG-1 gene. Molecular Phylogenetics and Evolution 21:974-983.

Harrison, G. L., P. A. McLenachan, M. J. Phillips, K. E. Slack, A. Cooper, and D. Penny. 2004. Four new avian mitochondrial genomes help get to basic evolutionary questions in the Late Cretaceous. Molecular Biology and Evolution 21:974-982.

Hedges, S., P. Parker, C. Sibley, and S. Kumar. 1996. Continental breakup and the ordinal diversification of birds and mammals. Nature 381:226-229.

Hope, S. 2002. The Mesozoic radiation of Neornithes; pp. 339-388 in L. M. Chiappe, and L. M. Witmer (eds.), Mesozoic Birds: Above the Heads of Dinosaurs, University of California Press, Berkeley, California.

Ketcham, R. A., and W. D. Carlson. 2001. Acquisistion, optimization, and interpretation of X-ray computed tomographic imagery: applications to the geosciences. Computers & Geosciences 27:381-400.

Kurochkin, E., G. Dyke, and A. A. Karhu. 2002. A new presbyornithid bird (Aves: Anseriformes) from the Late Cretaceous of southern Mongolia. American Museum Novitates 3386:1-11.

Livezey, B. 1997. The fossil Presbyornis and the interordinal relationships of waterfowl. Zoological Journal of the Linnean Society 121:361-428.

Marenssi, S., S. Salani, and S. Santillana. 2001. Geología de cabo Lamb, isla Vega, Antártida. Contribución Instituto Antártico Argentino 530:1-43.

Mayr, G., and J. Clarke. 2003. The deep divergences of neornithine birds: a phylogenetic analysis of morphological characters. Cladistics 19:527-553.

Noriega, J., and C. Tambussi. 1995. A Late Cretaceous Presbyornithidae (Aves: Anseriformes) from Vega Island, Antarctic Peninsula: paleobiogeographic implication. Ameghiniana 32:57-61.

Olson, S. 1999. The anseriform relationships of Anatalavis Olson and Parris (Anseranatidae), with a new species of the London Clay. Smithsonian Contributions in Paleobiology 89:231-243.

Olson, S., and A. Feduccia. 1980. Relationships and evolution of flamingos (Aves: Phoenicopteridae). Smithsonian Contributions in Zoology 316:1-73.

Padian, K., A. J. de Ricqlés, and J. R. Horner. 2001. Dinosaurian growth rates and bird origins. Nature 412:405-408.

Stidham, T. 1998. A lower jaw from a Cretaceous parrot. Nature 396:29-30.

van Tuinen, M., and B. Hedges. 2001. Calibration of avian molecular clocks. Molecular Biology and Evolution 18:206-213.

van Tuinen, M., T. Paton, O. Haddrath, and A. Baker. 2003. 'Big bang for Tertiary birds? A replay. Trends in Ecology and Evolution.

Literature
& Links

Additional imagery on the UTCT website

Additional
Imagery

To cite this page: Dr. Julia Clarke, C. P. Tambussi, J. I. Noriega, G. M. Erickson, and R. A. Ketcham, 2005, "Vegavis iaai" (On-line), Digital Morphology. Accessed December 20, 2014 at http://digimorph.org/specimens/Vegavis_iaai/.

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