The Jurassic rise of squamates as supported by lepidosaur disparity and evolutionary rates

Abstract

The squamates (lizards, snakes, and relatives) today comprise more than 10,000 species, and yet their sister group, the Rhynchocephalia, is represented by a single species today, the tuatara. The explosion in squamate diversity has been tracked back to the Cretaceous Terrestrial Revolution, 100 million years ago (Ma), the time when flowering plants began their takeover of terrestrial ecosystems, associated with diversification of coevolving insects and insect-eating predators such as lizards, birds, and mammals. Squamates arose much earlier, but their long pre-Cretaceous history of some 150 million years (Myr) is documented by sparse fossils. Here, we provide evidence for an initial radiation of squamate morphology in the Middle and Late Jurassic (174–145 Ma), and show that they established their key ecological roles much earlier than had been assumed, and they have not changed them much since.

The affinities of the Late Triassic Cryptovaranoides and the age of crown squamates

“…Furthermore, divergence times for the major clades of squamates using total evidence dating of dataset 2 (even when including †C. microlanius) are estimated to occur during the Middle and Late Jurassic (figure 7; electronic supplementary material, figure S21), in agreement with previous estimates [5,7,9,[13][14][15]26]. The revised, more basal position of †C.…”

“…252-202 Ma) age for the origins of the squamate and rhynchocephalian total clades, followed by the diversification of the major clades of crown squamates during the Jurassic (approx. 202-145 Ma) [5,7,[11][12][13][14][15]. This was followed by the radiation of modern squamate families during the middle and Late Cretaceous [16,17] shortly after the Cretaceous Terrestrial Revolution [18], along with the Cretaceous invasion of aquatic environments by mosasaurian squamates [19].…”

Evolutionary origins of the prolonged extant squamate radiation

“…†Eoscincus ornatus and †Microteras borealis suggest that the crown squamate morphological diversification took place while the lizard sister clade, the rhynchocephalians, were the dominant small reptiles across the globe [24][25][26]62,63 . Both new species existed at a critical juncture in lepidosaur evolution just before the hypothesized Jurassic-Cretaceous turnovers that devastated the diversity and abundance of rhynchocephalians and paved the way for elevated squamate species richness and abundance 26,34,35,53,[62][63][64][65][66][67] . At the type locality of †M.…”

A Palaeogene stem crotaphytid ( Aciprion formosum ) and the phylogenetic affinities of early fossil pleurodontan iguanians

“…In a combined-evidence analysis using an expanded morphological matrix, Afairiguana was placed in a polytomy with Anolidae and Polychrus [ 45 ]. In a more recent combined-evidence divergence-time analysis of UCEs and the matrix from Conrad [ 45 ], Afairiguana was placed as sister to Leiosauridae [ 8 ], and in a new morphological analysis, Afairiguana was placed as the sister of Anolis [ 98 ]. The reported diagnostic characters of Afairiguana include rugosities on the jugal, the presence of a discrete postfrontal, a posteriorly elongated dentary, proximally expanded and notched/fenestrated clavicles, postxiphisternal inscriptional ribs with midline contact, and caudal autotomy fracture planes anterior to the transverse processes [ 89 ].…”

“…Based on this study and that of Bolet et al . [ 98 ], Afairiguana avius should be considered a member of total clade Anolidae instead of Leiosauridae. In the uncalibrated constrained analyses of this study, Afairiguana was nested in crown-Anolidae (the unusual Anolis barbouri was sister to the rest of Anolidae), and in the calibrated constrained analyses Afairiguana avius was sister to crown-Anolidae.…”