Spatial and Temporal Body-Size Changes of Brachiopods in Relation to Varied Palaeogeographic Settings

The so-called Lilliput effect refers to a macroevolutionary phonemnon where the surviving animals in the aftermath of a mass extinction tend to be smaller on average than their pre-extinction relatives (Urbanek 1993; Fraiser and Bottjer 2004; Payne 2005; Twitchett 2007; Keller and Abramovich 2009; Zhang et al. 2016). This observation clearly highlights the importance of animal body-size changes in the study of mass extinctions. Body size is a key character of any organism and profoundly affects its biology and ecology (Jablonski 1996). Body size is often controlled by environmental factors, including oxygen fluctuations (Savrda and Bottjer 1986; Payne et al. 2008, 2013), food availability (Hallam 1965; Rheault and Rice 1996; Twitchett 2007; He et al. 2010) and temperature changes (Hunt et al. 2010; Sheridan and Bickford 2011; Edeline et al. 2013), as well as substrate conditions. As many of these factors vary with water depth, the relationship between body size and bathymetry (i.e., spatial body-size changes in this book) is crucial for the study on body-size changes (Anderson 1971; Thiel 1975; Peck and Harper 2010; Shi et al. 2016). For example, the study of spatial body-size changes is useful for examining which factor (or factors) played a more important role in controlling the differences of body sizes, thereby providing insights into the evolution of palaeoenvironments through time. Meanwhile, the study of size changes through past extinction times (i.e., temporal body-size changes in this book) is also of particular importance in understanding the biotic responses to global-scale climatic and environmental evolution (Twitchett 2007; He et al. 2010, 2015).