Abstract
AbstractVariation in preservation and sampling probability clouds our estimates of past biodiversity. The most extreme examples are Lagerstätten faunas and floras. Although such deposits provide a wealth of information and represent true richness better than other deposits, they can create misleading diversity peaks because of their species richness. Here, we investigate how Lagerstätten formations add to time series of vertebrate richness in the UK, Germany and China. The first two nations are associated with well‐studied fossil records and the last is a country where palaeontology has a much shorter history; all three nations include noted Lagerstätten in their fossil records. Lagerstätten provide a larger proportion of China's sampled richness than in Germany or the UK, despite comprising a smaller proportion of its fossiliferous deposits. The proportions of taxa that are unique to Lagerstätten vary through time and between countries. Further, in all regions, we find little overlap between the taxa occurring in Lagerstätten and in ‘ordinary’ formations within the same time bin, indicating that Lagerstätten preserve unusual faunas. As expected, fragile taxa make up a greater proportion of richness in Lagerstätten than the remainder of the fossil record. Surprisingly, we find that Lagerstätten account for a minority of peaks in the palaeodiversity curves of all vertebrates (18% in the UK; 36% in Germany and China), and Lagerstätten count is generally not a good overall predictor of the palaeodiversity signal. Vastly different sampling probabilities through taxa, locations and time require serious consideration when analysing palaeodiversity curves.
Highlights
Variation in preservation and sampling probability clouds our estimates of past biodiversity
Our aim is to address three questions: (1) Do Lagerst€atten significantly alter our perceptions of the vertebrate fossil record? (2) How does this vary between countries with widely different sampling histories? (3) Do Lagerst€atten contribute significantly to our understanding of new ecosystems, or do they mostly record previously identified ecosystems in greater detail? To address these questions, we explore how the palaeodiversity signal from three countries (UK, Germany, China) depends on ordinary and Lagerst€atten formations, discriminating between marine and terrestrial deposits, and between fragile and robust fossil specimens
We focus on vertebrates, as there has been a great deal of recent work on their palaeodiversity (Barrett et al 2009; Benson et al 2010; Benson & Butler 2011; Fro€bisch 2013; Lloyd & Friedman 2013; Close et al 2017; Cleary et al 2018; Driscoll et al 2019), they span both marine and terrestrial environments, and Lagerst€atten effects have been identified owing to the fragility of their remains, among, for example: pterosaurs (Butler et al 2009, 2013; Dean et al 2016), birds (Fountaine et al 2005; Brocklehurst et al 2013), lepidosaurs and lissamphibians (Fara 2002; Cleary et al 2018) and bats (Brown et al 2019)
Summary
Variation in preservation and sampling probability clouds our estimates of past biodiversity. One approach is to use sampling proxies such as the number of collections, localities or formations to model geological control of the fossil record (Smith 2007; Smith & McGowan 2007; Lloyd & Friedman 2013). Problems have been noted with the use of strict proxies as they are redundant with the palaeodiversity signal (Benton et al 2011), except in the case of broader sample counts; for example a count of ammonite diversity versus all marine localities. More useful may be subsampling approaches (rarefaction: Tipper 1979; SQS: Alroy 2010) and a Poisson sampling model (TRiPS: Starrfelt & Liow 2016), which have been employed to control for various sampling biases, with varying degrees of success Lagerst€atten are traditionally thought of as representing unusual, localized depositional environments, but there is strong evidence for clustering in space and time, perhaps reflecting global-scale phenomena that enable several similar Lagerst€atten to occur in an area or within a time bin (Muscente et al 2017)
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