, Volume 99, Issue 6, pp 435–442 | Cite as

A drowned Mesozoic bird breeding colony from the Late Cretaceous of Transylvania

  • Gareth DykeEmail author
  • Mátyás Vremir
  • Gary Kaiser
  • Darren Naish
Original Paper


Despite a rapidly improving fossil record, the reproductive biology of Mesozoic birds remains poorly known: only a handful of undisputed, isolated Cretaceous eggs (some containing embryonic remains) are known. We report here the first fossil evidence for a breeding colony of Mesozoic birds, preserved at the Late Cretaceous (Maastrichtian) Oarda de Jos (Od) site in the Sebeş area of Transylvania, Romania. A lens of calcareous mudstone with minimum dimensions of 80 cm length, 50 cm width and 20 cm depth contains thousands of tightly packed, morphologically homogenous eggshell fragments, seven near-complete eggs and neonatal and adult avialan skeletal elements. Eggshell forms 70–80 % of the matrix, and other fossils are entirely absent. The bones exhibit clear characters of the Cretaceous avialan clade Enantiornithes, and the eggshell morphology is also consistent with this identification. Both taphonomy and lithology show that the components of this lens were deposited in a single flood event, and we conclude that it represents the drowned remains of a larger enantiornithine breeding colony, swamped by rising water, washed a short distance and deposited in a shallow, low-energy pond. The same fate often befalls modern bird colonies. Such a large concentration of breeding birds suggests aquatic feeding in this species, augments our understanding of enantiornithine biology and shows that colonial nesting was not unique to crown birds.


Avialae Enantiornithes Eggs Oology Nesting behaviour Hatching 



We thank E. Buffetaut, A. Clark, Z. Csiki, A. Dulai, J. Dyke, G. Grellet-Tinner, E. Hankó, R. Hebda, R. Horn, F. Jackson, E. Kurochkin, A. Ősi, J. O’Connor, P.M. Sander, P. Tafforeau, D. Varricchio, X. Wang, two anonymous reviewers, R. Reisz and S. Thatje for their help with this project and for detailed comments on the manuscript.


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Copyright information

© Springer-Verlag 2012

Authors and Affiliations

  • Gareth Dyke
    • 1
    Email author
  • Mátyás Vremir
    • 2
  • Gary Kaiser
    • 3
  • Darren Naish
    • 1
  1. 1.Ocean and Earth Science, National Oceanography Centre, SouthamptonUniversity of SouthamptonSouthamptonUK
  2. 2.Department of Natural SciencesTransylvanian Museum Society (EME)Cluj-NapocaRomania
  3. 3.Royal British Columbia MuseumVictoriaCanada

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