Resolving Details of the Nonbiomineralized Anatomy of Trilobites Using Computed Tomographic Imaging Techniques Thesis Presented in Partial Fulfillment of the Requirements for the Master of Science in the Graduate School of The Ohio State University By Jennifer Anita Peteya, B.S. Graduate Program in Earth Sciences The Ohio State University 2013 Thesis Committee: Loren E. Babcock, Advisor William I. Ausich Stig M. Bergström Copyright by Jennifer Anita Peteya 2013 Abstract Remains of two trilobite species, Elrathia kingii from the Wheeler Formation (Cambrian Series 3), Utah, and Cornuproetus cornutus from the Hamar Laghdad Formation (Middle Devonian), Alnif, Morocco, were studied using computed tomographic (CT) and microtomographic (micro-CT) imaging techniques for evidence of nonbiomineralized alimentary structures. Specimens of E. kingii showing simple digestive tracts are complete dorsal exoskeletons preserved with cone-in-cone concretions on the ventral side. Inferred stomach and intestinal structures are preserved in framboidal pyrite, likely resulting from replication by a microbial biofilm. C. cornutus is preserved in non- concretionary limestone with calcite spar lining the stomach ventral to the glabella. Neither species shows sediment or macerated sclerites of any kind in the gut, which tends to rule out the possibilities that they were sediment deposit-feeders or sclerite-ingesting durophagous carnivores. Instead, the presence of early diagenetic minerals in the guts of E. kingii and C. cornutus favors an interpretation of a carnivorous feeding strategy involving separation of skeletal parts of prey prior to ingestion. ii Dedication This manuscript is dedicated to my parents for encouraging me to go into the field of paleontology and to Lee Gray for inspiring me to continue. iii Acknowledgments I would like to thank Loren E. Babcock for providing most of the specimens used in this study and providing guidance in the completion of the work. Daniel F. Merriam (Kansas Geological Survey) provided specimens of Ditomopyge decurtata for study, but which are not reported on here. I would also like to thank William Ausich and Matthew Saltzman for their helpful advice through the completion of my studies and Stig Bergström for his contribution to my thesis defense. Soo-Yeun Ahn from The University of Akron supplied environmental scanning electron microscope images. Garrett Noble and Kyle Bodnyk from The Ohio State University’s School of Biomedical Engineering provided help and advice with the microtomography scans. Richard Hart provided access to the microtomography facility in The Ohio State University’s School of Biomedical Engineering and Ann Cook provided access to the computed tomography scanner in The Ohio State University’s School of Earth Sciences. Funding for the project was provided by Loren Babcock and the Friends of Orton Hall Fund of The Ohio State University. iv Vita 2010................................................................B.S. Geology, Mount Union College 2010 to present ...............................................Graduate Teaching Associate, School of Earth Sciences, The Ohio State University Field of Study Major Field: Earth Sciences v Table of Contents Abstract ..........................................................................................................ii Dedication ......................................................................................................iii Acknowledgments..........................................................................................iv Vita .................................................................................................................v List of Figures ................................................................................................vii Chapter 1: Introduction ..................................................................................1 Chapter 2: Materials and Methods .................................................................4 Chapter 3: Scans of Elrathia kingii ................................................................8 Chapter 4: Scans of Cornuproetus cornutus ..................................................17 Chapter 5: Discussion ....................................................................................20 References ......................................................................................................25 vi List of Figures Figure 1. Micro-CT scanner ...........................................................................5 Figure 2. Digestive structures in Elrathia kingii, PRI 0000A........................12 Figure 3, Digestive structures in Elrathia kingii, PRI 0000B ........................14 Figure 4. ESEM images of PRI 0000A and PRI 0000D ................................16 Figure 5. Digestive structures and traces in Cornuproetus cornutus .............18 Figure 6. Reconstruction of the morphology of the Elrathia kingii alimentary canal, including the stomach in the anterior glabella and intestine, in dorsal view .................................................................................24 vii Chapter 1: Introduction Much of the information about the nonbiomineralized anatomy of trilobites comes from exceptionally preserved specimens representing a relatively small number of taxa. Nonbiomineralized remains have been described from approximately 40 species, which represents approximately 0.04% of the described species. Some of the more exquisite examples of nonbiomineralized preservation are documented from specimens of Phacops sp. (Stürmer and Bergström, 1973), Olenoides serratus (Whittington, 1975, 1980), Triarthrus eatoni (Cisne, 1981), Agnostus pisiformis (Müller and Walossek, 1987), Pterocephalia sp. (Chatterton et al., 1994), Buenellus higginsi (Babcock and Peel, 2007), Isotelus maximus (Babcock, 2003; English and Babcock, 2007), Coosella kieri (Robison and Babcock, 2011), Meniscopsia beebei (Robison and Babcock, 2011; Lerosey-Aubril et al. 2012), Sphaerophthalmus? (Eriksson and Terfelt, 2012), Selenopeltis buchi, and Biramites ingens (Fatka et al., 2013) from Konservat-lagerstӓtten (deposits of exceptional preservation) in North America, Europe, and Asia. Preservation of nonbiomineralized anatomy of trilobites varies. In some material, appendages are present and internal structures are not. In others, internal structures are present and appendages are not, or both appendages and internal structures are preserved. Trace fossils in sediment have been used to supplement information on the ventral anatomy of trilobites (Jensen, 1990; 1 Brandt et al., 1995; Babcock, 2003; English and Babcock, 2007), but the information provided by trace fossils is limited to details of external anatomy. Exceptional preservation of trilobites and other marine organisms is inferred to have occurred quickly after death (Briggs et al., 1994; Babcock and Chang, 1997; Babcock et al., 2001; Butterfield, 2002; Zhu et al., 2005; Ciampaglio et al., 2006; Robison and Babcock, 2011). Mineral replication of nonbiomineralized tissues was likely mediated by microbial biofilms in most examples (see Borkow and Babcock, 2003; Maas et al., 2006; English and Babcock, 2007; Lerosey-Aubril et al., 2010, 2012; Babcock and Robison, 2011). Mineral replication or fill of various types has been described (e.g., Stürmer and Bergström, 1973; Whittington, 1980; Cisne, 1981; Müller and Walossek, 1987; Orr et al., 1998; Babcock, 2003; Zhu et al., 2005; English and Babcock, 2007; Robison and Babcock, 2011). Among the preservational agents of nonbiomineralized anatomy of trilobites are calcium phosphate (Chatterton et al., 1994; Robison and Babcock, 2011; Lerosey-Aubril et al., 2010, 2012; Eriksson and Terfelt, 2012), calcium carbonate (Chatterton et al., 1994; English and Babcock, 2007), iron sulfide (Stürmer and Bergström, 1973; Cisne, 1982), aluminosilicates (Whittington, 1980), and silica (Babcock and Peel, 2007). Nonbiomineraized trilobite anatomy can be studied either through surface examination of fortuitously broken or well-prepared specimens, or through non-invasive imaging techniques. In comparatively rare examples, alimentary structures, limbs, or other nonbiomineralized structures are evident in trilobites with surface examination (see for example Chatterton et al., 1994; Babcock, 2003; Babcock and Peel, 2007; Robison 2 and Babcock, 2011; Fatka et al., 2013). Serial grinding and serial sectioning can reveal nonbiomineralized anatomy (Walcott, 1881), but this leads to destruction of specimens (Sutton et al., 2001). Non-invasive techniques (see for review Sutton, 2008), such as X- ray imaging technology, have long been known to be effective for discerning nonbiomineralized structures in unprepared and unexposed specimens (Stürmer and Bergström, 1973; Cisne, 1981). In recent years, standard x-ray imaging has been surpassed in utility by other non- invasive techniques, including computed tomography (CT), microtomography (micro- CT), and synchrotron radiation imaging. Such techniques make it possible to gain more insight into the anatomy of various arthropods without destroying the specimens. Computer-based imaging has revealed, for example, insect and arachnid inclusions in opaque amber (Dierick et al., 2007; Penney et al., 2007; Soriano et al., 2010), external anatomy of arthropods preserved in siderite (Garwood et al., 2009; Garwood and Sutton, 2010), and internal anatomy of the meraspid stage of a trilobite (Eriksson and Terfelt, 2012). The purpose of this paper is to describe and interpret