Amniotes through major biological crises: faunal turnover among Parareptiles and the end‐Permian mass extinction

Abstract

The Parareptilia are a small but ecologically and morphologically diverse clade of Permian and Triassic crown amniotes generally considered to be phylogenetically more proximal to eureptiles (diapsids and their kin) than to synapsids (mammals and their kin). A recent supertree provides impetus for an analysis of parareptile diversity through time and for examining the influence of the endPermian mass extinction on the clade's origination and extinction rates. Phylogeny-corrected measures of diversity have a significant impact on both rates and the distribution of origination and extinction intensities. Time calibration generally results in a closer correspondence between origination and extinction rate values than in the case of no time correction. Near the end-Permian event, extinction levels are not significantly higher than origination levels, particularly when time calibration is introduced. Finally, regardless of time calibration and ⁄ or phylogenetic correction, the distribution of rates does not differ significantly from unimodal. The curves of rate values are discussed in the light of the numbers and distributions of both range extensions and ghost lineages. The disjoint time distributions of major parareptile clades (e.g. procolophonoids and nycteroleterids-pareiasaurs) are mostly responsible for the occurrence of long-range extensions throughout the Permian. Available data are not consistent with a model of sudden decline at the end-Permian but rather suggest a rapid alternation of originations and extinctions in a number of parareptile groups, both before and after the Permian ⁄ Triassic boundary.Key words: diversity, extinctions, originations, Parareptilia, Permian, Triassic, turnover.Mass extinctions provide the most dramatic example of large-scale biological crises on record. The modalities of decline, disappearance and ⁄ or recovery of different clades inform our understanding of the tempo and mode of ecosystem collapse and recovery and allow us to explore the interplay of biotic and abiotic factors in shaping clade diversification. Therefore, the study of mass extinctions is of great interest to palaeontologists, evolutionary biologists, and macroecologists (e.g. Benton 2003; Erwin 2006; Purvis 2008). However, the specific responses of individual groups to extinctions remain inadequately documented, particularly in the terrestrial domain. It is clear that some clades of plants and animals were minimally affected by these events, whilst others were hit to varying degrees. One of the challenges in the analysis of largescale extinctions is to integrate patterns that emerge for specific groups to understand how they contribute to broader local and global trends.Numerous papers have used tetrapods for case studies of the impact of the end-Permian mass extinction on land (in particular, see papers by Pitrat 1973; Benton 1987; Olson 1989; Milner 1990; Maxwell 1992; Modesto et al. 2001 Modesto et al. , 2003 Benton et al. 2004; Ward et al. 2005; Botha and Smith 2006; Retallack et al. 2006; ...

Olson's Extinction and the latitudinal biodiversity gradient of tetrapods in the Permian

“…During the middle and late Permian, this fauna is replaced by a therapsid-dominated fauna with therapsid synapsids representing the most common large carnivores (dinocephalians, therocephalians, gorgonopsians) and herbivores (dinocephalians, dicynodonts) [6][7][8][9]. Parareptile diversity increases [10] while the amphibian fauna is noticeably reduced [5,11]. These faunal changes were accompanied by a shift towards more complex ecosystems with more trophic levels [2].…”

What limits the morphological disparity of clades?

“…The study of these patterns is central to the study of macroevolution, with questions centring on whether there is a typical pattern [1][2][3][4][5][6][7], whether the fortunes of clades are positively or negatively correlated [8][9][10][11][12][13] and whether there are particular responses to marked environmental changes [14]. Clade evolution is commonly studied by plotting diversity (numbers of constituent species, genera or higher taxa) through time, which can highlight periods of elevated diversification, extinction and turnover, as well as potential interactions between groups [15][16][17][18][19][20]. All Phanerozoic diversity curves affirm some form of increasing trajectory, variously modified by physical and biological factors [21].…”

First procolophonid (Reptilia, Parareptilia) from the Lower Triassic of Madagascar

“…The supposed decline of parareptiles during the Early Triassic was recently challenged with the description and revision of procolophonoids from the South African Karoo (Botha et al, 2007;Modesto et al, 2001. These new data show that the taxonomic diversity of parareptiles was able to keep up during the PT events because the extinction of some procolophonoids, millerettids, and pareiasaurs was offset by the diversification of the remaining procolophonoids (Irmis and Whiteside, 2012;Ruta et al, 2011). Though turtles have also been considered as parareptiles (Lee, 1995;Lyson et al, 2010;Reisz and Laurin, 1991), they have been regarded, in the latest studies, as modified diapsids that are more closely related to lepidosauriforms and sauropterygians on morphological (Li et al, 2011) and molecular (Lyson et al, 2012) grounds.…”