Inter- and Intraspecific Morphological Variation of Crinoid Columnals in Relation to Water Depth in the Type Cincinnatian (Upper Ordovician) A thesis submitted to The Graduate School of the University of Cincinnati in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in the Department of Geology of the College of Arts and Sciences 2005 by Bradley Deline B.S. University of Michigan, Ann Arbor, 2003 Committee Chair David L. Meyer Abstract Crinoid columnals are a major constituent in the Upper Ordovician fossil assemblage of the Cincinnati Arch Region. Several species of Cincinnatian crinoids are identifiable based on columnal morphology alone. Disarticulated columnals of two crinoids were measured throughout a 68-meter section of the Kope and lower Fairview Formations to examine the relationship between columnal morphology and sea level fluctuations. The columnal diameter of two disparid crinoids increased in the upward shallowing sequence. Detrended Correspondence Analysis axis 1 scores computed using columnal measurements of two crinoids correlated significantly with a proxy for depth. Therefore, crinoid columnals may provide a metric for the study of small-scale sea level fluctuation in a depositional sequence. A larger scale study showed similar morphological shifts in five taxa of crinoids, but to differing degrees. The morphologic shifts in the columnals are likely due to differences in nutrient levels and flow regimes between depths. Table of Contents List of Figures 2 List of Tables 3 Acknowledgments 4 Introduction 5 Materials and Methods 8 Results 13 Discussion 17 Summary 24 References 26 Appendix 1 (Species Description) 33 Appendix 2 (Crenularium Area Calculation) 40 Appendix 3 (Localities) 43 Appendix 4 (Data) 44 Figure Captions 54 Figures 59 Table Captions 80 Tables 81 1 LIST OF FIGURES Figure 1. SEM of Disparid columnals Figure 2. The effects of applying a moving average and coarsening on the Lithology and the Faunal gradient of the K445 section Figure 3. SEM of Monobatherid columnals. Figure 4. SEM of Cladid and Diplobatherid columnals. Figure 5. Diagram of columnal morphology and explanation of the calculation for lumen and crenularium circularity. Figure 6. Diagram showing the differences between columns in lateral view. Figure 7. Diagram showing the difference between column forms. Figure 8. Relative depth curve. Figure 9. Comparison of crinoid morphology, lithology and faunal gradient for K445. Figure 10. PCA axis 1 compared with PCA axis 2 Figure 11. PCA axis 2 compared with relative depth. Figure 12. PCA axis 2 compared with relative depth for disparids. Figure 13. Averages of PCA axis 2 compared with relative depth. Figure 14. Averages of PCA axis 2 compared with stratigraphic position. Figure 15. Average depth compared with average PCA axis 2 score. Figure 16. Range in columnal diameter of Ectenocrinus simplex in the K445 section. Figure 17. The effects of other crinoids on Cincinnaticrinus and Ectenocrinus. Figure 18. Comparing Relative Depth as well A PCA axis 2 score between pinnulate and nonpinnulate crinoids. 2 LIST OF TABLES Table 1. Crinoid Occurrences. Table 2. Characters used in the Polar coordinate analysis. Table 3. Result of the correlations in the K445 analysis. 3 ACKNOWLEDGMENTS I would like to foremost thank my advisor David Meyer as well as the other members of my committee Carlton Brett and Arnold Miller. My project was much improved due to discussions with Tomasz Baumiller, Forest Gahn, and Patrick McLaughlin. I would also like to thank Forest Gahn, Brenda Hanke, and Kendall Hauer for access to museum collections. Steve Holland, Jim Brower and Arnold Miller provided access to data, which allowed me to test ideas and broaden the scope of my project. Stacy Deline provided valuable technical assistance in preparation of several of the figures. Funding for this project was provided in part by the University of Cincinnati Geology Department and the University of Cincinnati Graduate Student Governance Association. Finally, I would like to thank my wife and family for their support throughout this project. 4 Introduction Traditionally, the preferred method to identify small-scale sea level oscillations within the alternating shales and limestones of the Upper Ordovician Cincinnatian Series was to track changes in the ratio of shale to limestone (Weiss and Norman, 1960; Ford, 1967). Recently, the use of event beds and cyclicity has helped to create a better- resolved picture of small-scale eustatic fluctuations (Brett and Algeo 2001). Lithology alone can be misleading because differing local patterns of sedimentation or variations in the frequency and intensity of storms (Holland et al., 2001) could give signals through a section that are unrelated to shifts in sea level. Therefore, it is important to include many different sources of information to track these small-scale patterns. In particular, fossil faunal distributions have been shown to track minor sea level shifts that are not detected by examination of the lithology alone (Holland et al., 2001, Miller et al., 2001). Faunal gradients are based on the ecological preferences of organisms and during short time intervals these preferences are assumed to remain static. Subtle differences in environments (flow rate, nutrients, light penetration) that favor certain taxa over others in a particular area should also cause intraspecific differences (ecophenotypic variation) along depth gradients. These effects could manifest themselves in many different ways, but they may be observable in the morphology of the animal. Therefore, studying morphology as it related to relative water depth could provide information independent of lithology to help diagnose small-scale changes and to provide insights into the biology of the organism. Several different organisms within the type Cincinnatian have been studied to detect changes in morphology that are related to water depth. Webber and Hanke 5 (submitted) have shown that there is an anteromedial shift in the eye location of the trilobite Flexicalymene graulosa through the Kope and Fairview Formations that tracks the faunal gradient presented by Miller et al. (2001). Daley (1993) showed that shell size of the bivalve Ambonychia tracked water depth based on facies models across the Cincinnatian, but the brachiopod Rafinesquina showed no such variation. However, Daley showed that the frequency of geniculation (an upward bend in the shell) was much more frequent in populations from shallower facies than in deep-water facies (Daley, 1993). Different taxa, even within an ecological guild, may react very differently to changes in environment. However, it appears that most taxa are sensitive to small-scale water depth oscillations and thus other taxa should be examined for similar patterns. Stalked crinoids (echinoderms) are filter feeders that are quite common throughout the fossil record in the shallow to marine environments, but they are mostly restricted to depths greater than 100 meters in today’s oceans (Hess, 1999). Crinoids are thought to be an ideal group for the study of small-scale changes in water depth and velocity because of well-documented relationships in the group between hydrodynamic conditions and morphologies associated with feeding. Crinoids need water flow to feed, but the water velocity cannot be too high or they would be forced to abandon feeding posture (Meyer, 1973, Messing, personal communication) or, in extreme cases, become dislodged (Rasmussen, 1977). Thus, crinoids need a distinctive flow regime to survive in a habitat and it has been documented that their morphology often reflects this (Kammer and Ausich, 1987). Most studies exploring the relationship between crinoids and their environment focus on how distributions of crinoids change with water depth (Meyer et al. 2002), how 6 filter morphology relates to the flow regime (Ausich, 1980; Kammer and Ausich, 1987), how morphology relates to substrate (Sprinkle and Guensburg, 1995), and the evolutionary consequences of these different morphologies (Baumiller, 1993). The difficulty with studying changes in filter morphology is that articulated specimens are rare in the fossil record, making studies of fine scale changes in depth difficult. However, disarticulated crinoid columnals are exceedingly common and underutilized sources of information. The difficulty with using individual columnals is in species identification. One attempt to characterize disarticulated columnals was made by Moore and Jeffords (1968), in which individual columnals were described as “form taxa” without knowledge of calyx morphology. This is a valuable approach to attempt to realize the actual diversity of crinoids in a poorly preserved assemblage and has obvious uses in biostratigraphy (Le Menn, 1985; Le Menn, 1993). This approach also has significant drawbacks, such as the inability to determine whether form taxa represent single biological species. Moreover, there is a danger of taxonomic overrepresentation among crinoids that have xenomorphic stems (several different types of columnals in a single stem). Tracing the morphology of a single species through a depositional sequence using form taxa is therefore problematic. Working in the type Cincinnatian, Meyer et al. (2002) showed that in a low diversity, well-studied area many crinoids can be identified to the species level using only columnal morphology, thereby eliminating the need for form taxa. Focusing on the study interval of Meyer et al. (2002), the present study examines