The evolution of Metriorhynchoidea (mesoeucrocodylia, thalattosuchia): an integrated approach using geometric morphometrics, analysis of disparity, and biomechanics

Abstract

Metriorhynchoid crocodylians represent the pinnacle of marine specialization within Archosauria. Not only were\ud they a major component of the Middle Jurassic–Early Cretaceous marine ecosystems, but they provide further\ud examples that extinct crocodilians did not all resemble their modern extant relatives. Here, we use a varied toolkit\ud of techniques, including phylogenetic reconstruction, geometric morphometrics, diversity counts, discrete character\ud disparity analysis, and biomechanical finite-element analysis (FEA), to examine the macroevolutionary history of\ud this clade. All analyses demonstrate that this clade became more divergent, in terms of biodiversity, form, and\ud function, up until the Jurassic–Cretaceous boundary, after which there is no evidence for recovery or further\ud radiations. A clear evolutionary trend towards hypercarnivory in Dakosaurus is supported by phylogenetic\ud character optimization, morphometrics, and FEA, which also support specialized piscivory within Rhacheosaurus\ud and Cricosaurus. Within Metriorhynchoidea, there is a consistent trend towards increasing marine specialization,\ud with the hypermarine Cricosaurus exhibiting numerous convergences with other Mesozoic marine reptiles (e.g. loss\ud of the deltopectoral crest and retracted external nares). In addition, biomechanics, morphometrics, and characterdisparity\ud analyses consistently distinguish the two newly erected metriorhynchid subfamilies. This study illustrates\ud that together with phylogeny, quantitative assessment of diversity, form, and function help elucidate the\ud macroevolutionary pattern of fossil clades

A long-snouted, multihorned tyrannosaurid from the Late Cretaceous of Mongolia

“…The feeding habits of large-bodied tyrannosaurids have been studied in intense detail, and bite marks, coprolites, gross morphology, and finite element analysis all indicate that Tyrannosaurus and kin had skulls well suited to take down large prey and bite through bone (4,5,30). A. altai lacks many of the cranial adaptations that are integral to using ''puncture-pull'' feeding in this manner, such as a deep skull, robust bones, fused or interlocking sutures (5), peg-like teeth (4), a rigid lower jaw (22), a strongly interlocking dentary symphysis (31), and a rugose lacrimal-postorbital bar above the orbit (32). This suggests that Alioramus exploited a different feeding style, likely focusing on smaller prey, than other Late Cretaceous tyrannosaurids, including the contemporary Tarbosaurus, whose remains have also been collected at the Tsaagan Khuushu locality.…”

Soft tissue preservation in a fossil marine lizard with a bilobed tail fin

“…A classic example is the streamlined body shape and fluked tail developed by cetaceans and fish to allow swift movement through the water. Piscine body plans and bilobed caudal flukes have also been documented in two groups of distantly related Mesozoic marine reptiles; that is, ichthyosaurs and metriorhynchid crocodyliforms, thanks to rare soft tissue impressions in exceptionally preserved fossils [1][2][3] . However, to date, no similar soft tissue evidence has been reported in mosasaurs, despite a remarkably rich fossil record and a collection history that spans almost 250 years 4 .…”

Reptiles Extintos - Volumen en Homenaje a Zulma Gasparini

“…La comprensión de estos cambios permitirá delimitar las innovaciones evolutivas claves que le permitieron a los metriorrínquidos la conquista, sin paralelo entre los arcosaurios, del medio pelágico. Fernández, 2005, 2011 1913; Hua and Buffrénil, 1996;Young et al, 2010), and enlarged external carotid foramen and canal, enlarged and highly vascularised nasal salt gland, preorbital fenestra related with the drainage of salt gland, and reduced olfactory tract and bulbs Gasparini, 2000, 2008;Fernández and Herrera, 2009;Pol and Gasparini, 2009;Fernández et al, 2011;Herrera et al, 2013a;Herrera and Vennari, 2015). Metriorhynchidae is a Middle Jurassic to…”

“…Based on the supra-generic taxonomy of Metriorhynchoidea updated by Young and Andrade (2009), Young et al (2010), and Cau and Fanti (2011, the Late JurassicEarly Cretaceous Argentinean metriorhynchids are included in the Rhacheosaurini and Geosaurini tribes. Rhacheosaurini are mainly characterized by having gracile skulls with long and tubular snouts, and acute carinated teeth without true denticles in the carinae (e.g., Cricosaurus), whereas…”

“…potens has been debated (see Gasparini, 1973aVignaud, 1995;Pol and Gasparini, 2007;Young et al, 2010; among others) but the poor preparation of this specimen precluded its determination. A recent preparation of the material allowed its redescription as well as the exploration of its phylogenetic relationships (see .…”