Phylogenetic structure of the extinction and biotic factors explaining differential survival of terrestrial notosuchians at the Cretaceous–Palaeogene crisis

Abstract

Although the clade Crocodylomorpha is represented by few extant species (Crocodylia), it has a rich fossil record. Hundreds of species, adapted to terrestrial, semi‐aquatic and marine environments, have existed over more than 200 million years. Numerous studies have attempted to characterize the factors driving the diversification and extinction events of Crocodylomorpha, resulting in ambiguous and even contradictory conclusions, which points to the need for phylogenetically and temporally smaller‐scaled studies. Here, we focus on differential survival at the Cretaceous–Palaeogene (K–Pg) crisis of Notosuchia, a diverse clade of mostly terrestrial Crocodylomorpha that achieved great diversity during the Cretaceous. More precisely, we tested the effect of body size and palaeotemperatures on notosuchian survival probability during the K–Pg crisis as well as the effect of diet on the evolution of their body size. We find that Notosuchia showed an evolutionary trend towards larger body sizes through time, associated with a shift from an omnivorous to a carnivorous diet. This may explain why sebecids were the only notosuchians to survive the K–Pg crisis. We also corroborate the conclusions of previous studies that detected a Lagerstätten effect occurring in the Adamantina Formation (Upper Cretaceous, Brazil, Bauru Group). This work confirms the value of more finely‐scaled macroevolutionary studies for understanding the history of a rich and complex group such as Crocodylomorpha.

Biotic and abiotic factors and the phylogenetic structure of extinction in the evolution of Tethysuchia

“…One of these factors may be dietary differences. Indeed, dietary shifts have been shown to explain body-size variation in Canidae and Notosuchia (Van Valkenburgh et al 2004; Aubier et al 2023). Another possible component may be species competitiveness: species with a relatively similar ecology may limit competition for the same resources because of their larger range of body sizes.…”

“…As a result, SW was excluded from further analyses. SL is the most available skull metric and has previously been used as a proxy for body size (e.g., Godoy et al 2019; Aubier et al 2023). However, studies have criticized this variable as subject to biases linked to group differences and have tried to address this problem using various methods (Young et al 2011; Stockdale and Benton 2021).…”

“…D -values can fall outside this range. This method has been used before to check extinction risk for extant organisms (Fritz and Purvis 2010; Yessoufou et al 2012; Fontana et al 2021) or extinction selectivity in the fossil record (Allen et al 2019; Wilke et al 2020; Aubier et al 2023). We used the phylo.d function of the caper package (Orme et al 2013) in R v. 4.2.2 (R Core Team 2013), selecting 1000 permutations (i.e., repetition of the simulations to scale D -values), as suggested by Fritz and Purvis (2010).…”

“…These analyses revealed a phylogenetic structure in notosuchian extinction at the K/Pg crisis and an evolutionary trend toward larger body sizes after this crisis. This last trend was tentatively explained as being the outcome of a dietary shift (Aubier et al 2023).…”

“…Such studies, however, remain scarce. A new approach coding extinction/survival as a binary variable was applied recently to Notosuchia, a group of largely terrestrial crocodylomorphs (Aubier et al 2023). These authors tested the phylogenetic structure of extinction during the K/Pg crisis and used Phylogenetic Logistic Regression (PLR) to test the factors influencing survival during the K/Pg crisis.…”