Completeness of the Fossil Record and the Validity of Sampling Proxies: A Case Study from the Triassic of England and Wales
Dunhill, A. M., Benton, M. J., Newell, A. J., Twitchett, R. J., Journal of the Geological Society
Abstract: Many studies have highlighted correlations between palaeodiversity and sampling proxies. These correlations have been interpreted as evidence for bias, common cause, or redundancy between signals. Here, we compare a number of sampling proxies representing sedimentary rock volume, rock accessibility and worker effort with palaeodiversity through the predominantly terrestrial Triassic System in England and Wales. We find that proxies for sedimentary rock volume and accessibility do not correlate with palaeodiversity until the removal of facies-related preservational and palaeoecological factors. This indicates that a weak sampling signal may be present, but the effects of changing palaeoenvironments are far more important at the regional scale. Significant correlations between worker effort and palaeodiversity are detected, although this is likely to be a result of the preferential sampling of formations already known to be rich in fossils. The fact that there is little evidence for sedimentary rock bias in the fossil record of the Triassic of England and Wales suggests that either (1) sampling bias is not a major source of error at the regional scale or (2) sampling proxies are inadequate representations of geological and human sampling bias.
Supplementary material: Correlation test results and raw time series data from the study are available at www.geolsoc.org.uk/SUP18567.
The fossil record provides our best resource to study evolutionary patterns through deep time by observing past patterns of diversity (e.g. Benson et al. 2010; Butler et al. 2010; Upchurch et al. 2011) and disparity (e.g. Butler et al. 2012). However, palaeontologists must consider the inadequacies of the fossil record that arise from differing preservation and sampling (e.g. Raup 1972; Peters & Foote 2001; Crampton et al. 2003; Smith 2007; Benson et al. 2010; Benton et al. 2011). Raup (1972) was the first to identify correlations between the fossil and rock records and interpreted these patterns as a geological megabias that had overprinted the true diversity pattern in the fossil record (Raup 1976). Since then, many other studies have found covariation between palaeodiversity and various proxies for sampling (Peters & Foote 2001, 2002; Smith 2001; Smith et al. 2001; Crampton et al. 2003; Smith & McGowan 2005, 2007; Wang & Dodson 2006; Fröbisch 2008; Barrett et al. 2009; Butler et al. 2009, 2010; Wall et al. 2009; Benson et al. 2010). These examples of rock record-fossil record covariation at various scales have been interpreted as evidence for: (1) a sampling bias on palaeodiversity estimates (Raup 1972, 1976; Peters & Foote 2001, 2002; Smith 2001; Smith & McGowan 2005, 2007; Fröbisch 2008; Barrett et al. 2009; Butler et al. 2009, 2010; Wall et al. 2009; Benson et al. 2010); or (2) a common cause (e.g. sea level) having driven the fossil and rock records simultaneously (Sepkoski 1976; Peters 2005, 2006; Peters & Heim 2010; Hannisdal & Peters 2011; Heim & Peters 2011); or (3) redundancy between sampling proxies and apparent diversity (Benton 2010; Benton et al. 2011; Dunhill 2012). Most palaeontologists now accept that the diversity signal in the fossil record represents a combination of both evolutionary patterns and biases associated with sampling and preservation (Kalmar & Currie 2010; Dunhill et al. 2012), and that it is very difficult to distinguish between biological signals and sampling noise.
Almost all published studies investigating the adequacy of the fossil record have been carried out on a global (Raup 1972, 1976; Lloyd et al. 2008; Barrett et al. 2009; Butler et al. 2009, 2010; Wall et al. 2009; Benson et al. 2010) or continental scale (Smith 2001; Peters 2005, 2006; Smith & McGowan 2005, 2007; Marx 2009; Peters & Heim 2010, 2011; Heim & Peters 2011), where both the fossil occurrence data and sampling proxies are often, at best, vague approximations (Twitchett …
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Publication information: Article title: Completeness of the Fossil Record and the Validity of Sampling Proxies: A Case Study from the Triassic of England and Wales. Contributors: Dunhill, A. M. - Author, Benton, M. J. - Author, Newell, A. J. - Author, Twitchett, R. J. - Author. Journal title: Journal of the Geological Society. Volume: 170. Issue: 2 Publication date: March 2013. Page number: 291+. © Geological Society Publishing House Jan 2009. Provided by ProQuest LLC. All Rights Reserved.
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