See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/260123543 Evaluating deformation in Spheroolithus dinosaur eggs from Zhejiang, China Article in Historical Biology · July 2013 DOI: 10.1080/08912963.2013.807252 CITATIONS READS 3 81 5 authors, including: Christian Heck Hannah M. Wilson Oklahoma State University - Center for Health … Montana State University 6 PUBLICATIONS 3 CITATIONS 1 PUBLICATION 3 CITATIONS SEE PROFILE SEE PROFILE David J Varricchio Frankie D. Jackson Montana State University Montana State University 116 PUBLICATIONS 2,657 CITATIONS 77 PUBLICATIONS 1,459 CITATIONS SEE PROFILE SEE PROFILE Some of the authors of this publication are also working on these related projects: Avian Pelvis-Egg Coevolution View project Eggshell taphonomy View project All content following this page was uploaded by David J Varricchio on 08 September 2015. The user has requested enhancement of the downloaded file. This article was downloaded by: [David J. Varricchio] On: 05 July 2013, At: 05:33 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Historical Biology: An International Journal of Paleobiology Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/ghbi20 Evaluating deformation in Spheroolithus dinosaur eggs from Zhejiang, China Hannah M. Wilson a , Christian T. Heck b , David J. Varricchio c , Frankie D. Jackson c & Xingsheng Jin d a Department of Economics and Department of History , Montana State University , Bozeman , MT , 59717 , USA b Department of Cell Biology and Neuroscience , Montana State University , Bozeman , MT , 59717 , USA c Department of Earth Sciences , Montana State University , Bozeman , MT , 59717 , USA d Zhejiang Museum of Natural History , No. 6 in the Westlake Cultural Plaza, Hangzhou , Zhejiang , P.R. China Published online: 01 Jul 2013. To cite this article: Historical Biology (2013): Evaluating deformation in Spheroolithus dinosaur eggs from Zhejiang, China, Historical Biology: An International Journal of Paleobiology, DOI: 10.1080/08912963.2013.807252 To link to this article: http://dx.doi.org/10.1080/08912963.2013.807252 PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. 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Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions Historical Biology, 2013 http://dx.doi.org/10.1080/08912963.2013.807252 Evaluating deformation in Spheroolithus dinosaur eggs from Zhejiang, China Hannah M. Wilsona1, Christian T. Heckb1*, David J. Varricchioc, Frankie D. Jacksonc and Xingsheng Jind aDepartment of Economics and Department of History, Montana State University, Bozeman, MT 59717, USA; bDepartment of Cell Biology and Neuroscience, Montana State University, Bozeman, MT 59717, USA; cDepartment of Earth Sciences, Montana State University, Bozeman, MT 59717, USA; dZhejiang Museum of Natural History, No. 6 in the Westlake Cultural Plaza, Hangzhou, Zhejiang, P.R. China (Received 31 January 2013; final version received 18 April 2013) Lack of stratigraphic context for dinosaur eggs inhibits understanding of dinosaur reproductive biology and the taphonomic processes of egg preservation. Past taphonomic work suggests two features, compression ridges (sharp edge of broken eggshell around egg circumference) and deformation asymmetry (proportion of crushed to rounded sides of the egg), as geopetal structures. We examined these features across a large sample of Spheroolithus eggs from the Cretaceous of Zhejiang, China, to test their utility. On 103 isolated eggs, we determined asymmetry ratios (crushed side egg height divided by rounded side egg height) and observed an average asymmetry ratio of 0.71. Additional observations of in situ eggs demonstrate the stratigraphic downside as more rounded and less fractured, the stratigraphic upside as flatter with heavier fracturing and compression ridges as parallel to original bedding plane. Burial-caused fractures on the upper side of the egg allowed sediment to partially fill, subsequently supporting the bottom portion. Examining these features within 16 clutches allowed differentiation of biotic versus taphonomically altered arrangements. Three common clutch arrangements include planar (minimal egg overlap), offset (extreme overlap) and agglomerate (randomly arranged, closely packed). Analysis of egg strike and dip across clutches favours planar clutches as the principal configuration for Spheroolithus clutches. Keywords: Spheroolithus; compression; orientation; Zhejiang; asymmetry; deformation Introduction high levels of fracturing and a unique crease-like fracture Research on dinosaur eggs provides insight into dinosaur about the equator. After extensive observations on the reproductive biology, biodiversity, climatic conditions, preservation of spherical Cretaceous eggs, including climate change and dinosaur extinction (Thaler 1965; Faveoolithus and Dictyoolithus, Mueller-Towe et al. Folinsbee et al. 1970; Erben et al. 1979; Williams 1981; (2002) concluded that an egg’s original shape was better Hirsch et al. 1989; Zhao et al. 1991; Zelenitsky and Hills preserved after infilling with sediment. Through the use of 1997; Chiappe et al. 2000; Yang et al. 2001; Zhao et al. computed tomography, they observed that some eggs 2002; Varricchio and Jackson 2004). However, taphonomic exhibited a sediment-filled bottom overlain by a hollow processes such as lithostatic compaction and solifluction space or, alternatively, crystals that precipitated and filled have the potential to alter egg clutch arrangement and the previously open space. More recently, Soja (2008) original egg morphology (Hayward et al. 1989; Hayward performed burial experiments on intact modern eggs of et al. 2000; Jackson et al. 2004; Jackson and Schmitt 2008; alligators, chickens, emus and ostriches. Her experiments Downloaded by [David J. Varricchio] at 05:33 05 July 2013 Hayward et al. 2011). The altered features can potentially showed that fractures appeared on eggs during burial and lead to misidentification of eggs and misinterpretations of that sediment sifted through the fractures into the eggs, nest construction, incubation and hatching behaviours. filling their interior and preventing further collapse. In Thus, understanding the effects of mechanical alteration of addition, shell membrane that lined the inside of eggs acted fossilised eggs is essential for accurate interpretation of egg as an adhesive, ‘gluing’shell pieces together after the initial clutch arrangement and egg morphology. Despite the phases of burial and fracturing. importance of understanding taphonomic effects, there has The Zhejiang Museum of Natural History (ZMNH) in been a limited number of research on mechanical alteration Hangzhou, China, houses a large collection of dinosaur of eggs and eggshell (e.g. Hayward et al. 1989; Hayward eggs and egg clusters from Upper Cretaceous formations et al. 2000; Mueller-Towe et al. 2002; Soja 2008). of the Tiantai basin of Zhejiang Province. We consider egg Hayward et al. (2000) used a hydraulic press to clusters to consist of multiple eggs adjacent to one another simulate the effects of triaxial loading with a greater within the same matrix block. The majority of ZMNH vertical than horizontal force on complete chicken eggs. eggs exhibit a distinctly crushed side and a more rounded After the simulated loading, the compressed eggs displayed side presumably reflecting lithostatic compaction. *Corresponding author. Email: [email protected] q 2013 Taylor & Francis 2 H.M. Wilson et al. Figure 1. (A) Crushed Spheroolithus from ZMNH with visible compression ridge (arrows) around circumference of egg separating crushed side and rounded side. (B) Crushed side of egg displaying flatter surface and high eggshell fracturing. (C) Rounded side of egg has convex shape and minimal eggshell fracturing (scale bar ¼ 3 cm). A ‘compression ridge’ defined here as an irregular band of sufficient stratigraphic data. For example, most Zhejiang broken and protruding eggshell, extends around the specimens were acquired from construction sites and circumference of the egg and separates the two sides. independent fossil collectors, and thus, the majority lack This feature is most visible on isolated eggs (Figure 1). We detailed