Increased pliosaurid dental disparity across the Jurassic–Cretaceous transition

Abstract

Pliosaurid marine reptiles played important roles in marine food chains from the Middle Jurassic to the middle Cretaceous, frequently as apex predators. The evolution of pliosaurids during the later parts of the Early Cretaceous has recently been illuminated by discoveries from Russia (Hauterivian) and Colombia (Barremian). However, knowledge of pliosaurids representing the Jurassic–Cretaceous transition (late Tithonian – Valanginian), is still largely incomplete, especially during the earliest Cretaceous. As such, the effect on pliosaurids of hypothesized faunal turnover during the Jurassic–Cretaceous boundary interval is poorly understood. We report pliosaurid teeth from the upper Volgian (Tithonian, Upper Jurassic) of the Kheta river basin (Eastern Siberia, Russia), to the Berriasian and Valanginian (Lower Cretaceous) of the Volga region (European Russia). These assemblages have yielded a series of distinct tooth morphotypes, including the first reports of conical‐toothed pliosaurids from the latest Jurassic and earliest Cretaceous. This challenges the hypothesis that only one lineage of pliosaurids crossed the Jurassic–Cretaceous boundary. It appears that conical‐toothed pliosaurids co‐existed with their trihedral‐toothed relatives for at least 25 million years during the latest Jurassic and earliest Cretaceous. In fact, our quantitative analyses indicate that pliosaurids reached their maximal dental disparity during this interval, showing little evidence of turnover associated with the Jurassic–Cretaceous transition. Instead, disparity decreased later in the Early Cretaceous, with the disappearance of trihedral‐toothed forms in the Barremian.

Estimating the evolutionary rates in mosasauroids and plesiosaurs: discussion of niche occupation in Late Cretaceous seas

“…The overall tree topology broadly agrees with those reconstructed through more recent parsimony analyses (see, e.g., Ketchum & Benson, 2010;Benson et al, 2013;Benson & Druckenmiller, 2014;Fischer et al, 2015;Cau & Fanti, 2016;Otero, 2016;Sachs, Hornung & Kear, 2016;Fischer et al, 2017;O'Gorman et al, 2017;Serratos, Druckenmiller & Benson, 2017;Fischer et al, 2018;O'Gorman, Gasparini & Spalletti, 2018;Páramo-Fonseca, Benavides-Cabra & Gutiérrez, 2018;Sachs, Lindgren & Kear, 2018;Madzia, Sachs & Lindgren, 2019;Morgan & O'Keefe, 2019). Plesiosauria (posterior probability [pp ] = 1; node origin estimated at ∼241 Mya) basally branches into Rhomaleosauridae (pp = 0.96; ∼215 Mya) and Neoplesiosauria (pp = 0.88; ∼215 Mya), consisting of Pliosauridae (pp = 1; ∼206 Mya) and Plesiosauroidea (pp = 0.89; ∼210 Mya).…”

“…The changes include: modifications to the scores of Brancasaurus brancai and 'Gronausaurus wegneri' as in Sachs, Hornung & Kear (2016); addition of Lagenanectes richterae from ; addition of Nakonanectes bradti, Albertonectes vanderveldei, Aristonectes quiriquinensis, Elasmosaurus platyurus, 'Hydralmosaurus serpentinus', Mauisaurus haasti, 'Libonectes' atlasense, Terminonatator ponteixensis, Tuarangisaurus keyesi, Zarafasaura oceanis, Kawanectes lafquenianum, and Vegasaurus molyi from Serratos, Druckenmiller & Benson (2017); addition of Neusticosaurus pusillus and Nothosaurus marchicus, and modifications to the scores of Yunguisaurus liae and Pistosaurus OTUs as in Wintrich et al (2017); addition of Acostasaurus pavachoquensis, 'Kronosaurus' boyacensis, and Sachicasaurus vitae from Páramo-Fonseca, Benavides-Cabra & Gutiérrez (2018), with amended scores for A. pavachoquensis and S. vitae as in Páramo-Fonseca, Benavides-Cabra & Gutiérrez (2019); modifications to the character scores of Thililua longicollis and addition of Eopolycotylus rankini, Manemergus anguirostris, Dolichorhynchops tropicensis, Georgiasaurus penzensis, Dolichorhynchops sp. (specimen ROM 29010), Dolichorhynchops herschelensis, Sulcusuchus erraini, and Mauriciosaurus fernandezi following Fischer et al (2018), with amended scores for Trinacromerum bentonianum, Dolichorhynchops osborni, Dolichorhynchops bonneri, Mauriciosaurus fernandezi, and Polycotylus latipinnis as in Morgan & O'Keefe (2019); addition of Styxosaurus snowii from Sachs, Lindgren & Kear (2018); and modifications to the scores of Kronosaurus queenslandicus and Stenorhynchosaurus munozi following Holland (2018) and Páramo-Fonseca, Benavides-Cabra & Gutiérrez (2019).…”

“…The origin of the least inclusive clade formed by Russellosaurina and Mosasaurinae (+ Halisaurinae) occurred ∼100 Mya, and the splitting of the clade uniting plioplatecarpines and tylosaurines ∼93 Mya; thus covering the last few millions of years of the brachauchenine evolution. In turn, during the splitting of the smallest clade comprising globidensins and mosasaurins (∼81 Mya) and the origin of the Mosasaurus node (∼75 Mya), pliosaurids were probably already extinct and polycotylids rare (e.g., Sato, 2005;Salgado, Parras & Gasparini, 2007;O'Gorman & Gasparini, 2013;Novas et al, 2015;Fischer et al, 2018;Morgan & O'Keefe, 2019).…”

“…Similarly, the large-scale assessment of pliosaurid teeth by Zverkov et al (2018), that was based on material representing the vast majority of pliosaurid taxa, including assemblages of isolated teeth, suggested that pliosaurids (1) could have been represented by two lineages in the Cretaceous, instead of one, and that (2) they experienced the highest dental disparity around the Jurassic/Cretaceous boundary interval. Such results were surprising because they were and still are in striking contrast with all studies assessing the phylogenetic relationships of Pliosauridae, that cannot consider numerous latest Jurassic/Early Cretaceous specimens due to their highly fragmentary nature, and that suggest the presence of a single clade of pliosaurids crossing the Jurassic/Cretaceous boundary.…”

Convergence and functional evolution of longirostry in crocodylomorphs

“…Pliosaurs achieved their highest dental disparity in the Late Jurassic suggesting diverse feeding strategies (Zverkov et al . ), some of them being marine apex predators (Foffa et al . ) as geosaurine metriorhynchids were (Young et al .…”