The macroevolutionary landscape of short-necked plesiosaurians

Abstract

Throughout their evolution, tetrapods have repeatedly colonised a series of ecological niches in marine ecosystems, producing textbook examples of convergent evolution. However, this evolutionary phenomenon has typically been assessed qualitatively and in broad-brush frameworks that imply simplistic macroevolutionary landscapes. We establish a protocol to visualize the density of trait space occupancy and thoroughly test for the existence of macroevolutionary landscapes. We apply this protocol to a new phenotypic dataset describing the morphology of short-necked plesiosaurians, a major component of the Mesozoic marine food webs (ca. 201 to 66 Mya). Plesiosaurians evolved this body plan multiple times during their 135-million-year history, making them an ideal test case for the existence of macroevolutionary landscapes. We find ample evidence for a bimodal craniodental macroevolutionary landscape separating latirostrines from longirostrine taxa, providing the first phylogenetically-explicit quantitative assessment of trophic diversity in extinct marine reptiles. This bimodal pattern was established as early as the Middle Jurassic and was maintained in evolutionary patterns of short-necked plesiosaurians until a Late Cretaceous (Turonian) collapse to a unimodal landscape comprising longirostrine forms with novel morphologies. This study highlights the potential of severe environmental perturbations to profoundly alter the macroevolutionary dynamics of animals occupying the top of food chains.

Ecological signal in the size and shape of marine amniote teeth

“…A Generalised Procrustes Superimposition (GPA) is then called to eliminate the size and positioning factors and then a Principal Component analysis (PCA) is applied on the GPA coordinates to produce morphospaces. Density-based macroevolutionary landscape are then produced using the method explained in Fischer et al [29]. Newly digitized models are deposited on Morphosource (https://www.morphosource.org/projects/000435369).…”

Global ecomorphological restructuring of dominant marine reptiles prior to the K/Pg mass extinction

“…Comparative NMDS analyses were performed in ‘vegan’ v.2.5-6 (Oksanen et al 2018); graphical results from PCoA ecomorphospaces can be found in Supplementary Figure S1. Kernel 2D density estimates were used to visualise density-based macroevolutionary landscapes, plotted onto NMDS ecomorphospaces, following the methodology of Fischer et al (2020). Moreover, mandible length (proxy for body size) was used both in scaling datapoints to visually inspect the spread of large-sized mosasaurids, and additionally to compare the spread of body sizes in mosasaurids through the Campanian-Maastrichtian.…”

“…Marine ecosystems were dominated by reptiles during the entire Mesozoic (Motani 2002; Massare 1987; Bardet 2012; Scheyer et al 2014). Despite important turnovers at its base (Fischer et al 2017; 2020), the Late Cretaceous is no exception, as mosasaurid squamates rapidly diversified (Bardet et al 2008; 2007; Polcyn et al 2014), achieving a cosmopolitan distribution prior to the Campanian (c.83.5 Mya) (Bardet et al 2014; Polcyn et al 2014), and colonised several ecological guilds until their global extinction at the K/Pg boundary mass extinction (66 Mya) (Martin et al 2017). Prior to the Campanian, mosasaurid taxonomic richness saw a steep increase (Polcyn et al 2014), with speciation in the Western Interior Seaway (WIS) in central North America triggering a diversification during the so-called ‘Niobraran Age’ (e.g.…”

Anatomy and phylogenetic relationships of Temnodontosaurus zetlandicus (Reptilia: Ichthyosauria)

“…Because skull shape in marine tetrapods is now known to be heavily influenced by ecomorphological convergence (e.g. Kelley & Pyenson, 2015;Fischer, 2016;Fischer et al, 2017Fischer et al, , 2020McCurry et al, 2017), these ratios are likely suboptimal to establish a stable taxonomy. Switching the taxonomy of Early Jurassic ichthyosaurians to apomorphy-based definitions is desirable and ongoing (Maisch & Matzke, 2000;Maisch, 2008Maisch, , 2010Martin et al, 2012;Lomax, 2016;Maxwell & Corteś, 2020;Swaby & Lomax, 2020), but still far from complete.…”