Morphology of the sacral region and reproductive strategies of Metriorhynchidae: a counter-inductive approach

Herrera, Yanina; Fernández, Marta; Lamas, Susana Gisela; Campos, Lisandro; Talevi, Marianella; Gasparini, Zulma

doi:10.1017/s1755691016000165

Cited by 27 publications

(25 citation statements)

References 46 publications

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“…We here hypothesise that this was in response to living in different habitats: heavily ornamented forms in semi-aquatic coastal environments and weakly ornamented forms in a more pelagic habitat, in which basking was less important (or perhaps impossible). A similar reduction in dermatocranial and osteodermal ornamentation is also seen in Metriorhynchidae, which are well established as fully pelagic thalattosuchians (Fraas, 1902; Andrews, 1913; Fernández & Gasparini, 2008; Herrera, Fernández & Gasparini, 2013; Herrera et al, 2017).…”

Section: Discussionmentioning

confidence: 61%

Revision of the Late Jurassic deep-water teleosauroid crocodylomorph Teleosaurus megarhinus Hulke, 1871 and evidence of pelagic adaptations in Teleosauroidea

Foffa

Johnson

Young

et al. 2019

PeerJ

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Teleosauroids were a successful group of semi-aquatic crocodylomorphs that were an integral part of coastal marine/lagoonal faunas during the Jurassic. Their fossil record suggests that the group declined in diversity and abundance in deep water deposits during the Late Jurassic. One of the few known teleosauroid species from the deeper water horizons of the well-known Kimmeridge Clay Formation is ‘Teleosaurus’ megarhinus Hulke, 1871, a poorly studied, gracile longirostrine form. The holotype is an incomplete snout from the Aulacostephanus autissiodorensis Sub-Boreal ammonite Zone of Kimmeridge, England. The only other referred specimen is an almost complete skull from the slightly older A. eudoxus Sub-Boreal ammonite Zone of Quercy, France. Recently, the validity of this species has been called into question. Here we re-describe the holotype as well as the referred French specimen and another incomplete teleosauroid, DORCM G.05067i-v (an anterior rostrum with three osteoderms and an isolated tooth crown), from the same horizon and locality as the holotype. We demonstrate that all specimens are referable to ‘Teleosaurus’ megarhinus and that the species is indeed a valid taxon, which we assign to a new monotypic genus, Bathysuchus. In our phylogenetic analysis, the latest iteration of the ongoing Crocodylomorph SuperMatrix Project, Bathysuchus megarhinus is found as sister taxon to Aeolodon priscus within a subclade containing Mycterosuchus nasutus and Teleosaurus cadomensis. Notably Bathysuchus has an extreme reduction in dermatocranial ornamentation and osteoderm size, thickness and ornamentation. These features are mirrored in Aeolodon priscus, a species with a well-preserved post-cranial skeleton and a similar shallow and inconspicuous dermal ornamentation. Based on these morphological features, and sedimentological evidence, we hypothesise that the Bathysuchus + Aeolodon clade is the first known teleosauroid lineage that evolved a more pelagic lifestyle.

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Section: Discussionmentioning

confidence: 61%

Revision of the Late Jurassic deep-water teleosauroid crocodylomorph Teleosaurus megarhinus Hulke, 1871 and evidence of pelagic adaptations in Teleosauroidea

Foffa

Johnson

Young

et al. 2019

PeerJ

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“…The basal cetaceans that we consider most skeletally analogous to semiaquatic thalattosuchians-the nearshore remingtonocetids, which had teleosauroidlike elongate snouts, comparatively long necks, forelimbs and hindlimbs used in swimming, and robust pelves (1, 33)-had miniaturized pelagic-style labyrinths, and flourished for only a few million years. It may be that cetaceans were able to adapt more quickly to fully pelagic lifestyles, because they evolved from terrestrial ancestors that were already endothermic and gave live birth, whereas metriorhynchids had to develop these attributes after entering the water (34,35).…”

Section: Discussionmentioning

confidence: 99%

Inner ear sensory system changes as extinct crocodylomorphs transitioned from land to water

Schwab

Young

Neenan

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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Major evolutionary transitions, in which animals develop new body plans and adapt to dramatically new habitats and lifestyles, have punctuated the history of life. The origin of cetaceans from land-living mammals is among the most famous of these events. Much earlier, during the Mesozoic Era, many reptile groups also moved from land to water, but these transitions are more poorly understood. We use computed tomography to study changes in the inner ear vestibular system, involved in sensing balance and equilibrium, as one of these groups, extinct crocodile relatives called thalattosuchians, transitioned from terrestrial ancestors into pelagic (open ocean) swimmers. We find that the morphology of the vestibular system corresponds to habitat, with pelagic thalattosuchians exhibiting a more compact labyrinth with wider semicircular canal diameters and an enlarged vestibule, reminiscent of modified and miniaturized labyrinths of other marine reptiles and cetaceans. Pelagic thalattosuchians with modified inner ears were the culmination of an evolutionary trend with a long semiaquatic phase, and their pelagic vestibular systems appeared after the first changes to the postcranial skeleton that enhanced their ability to swim. This is strikingly different from cetaceans, which miniaturized their labyrinths soon after entering the water, without a prolonged semiaquatic stage. Thus, thalattosuchians and cetaceans became secondarily aquatic in different ways and at different paces, showing that there are different routes for the same type of transition.

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“…To accommodate major uncertainties in crocodylomorph phylogeny, we also conducted analyses using two alternative topologies, varying the position of Thalattosuchia. Thalattosuchians are Jurassic–Early Cretaceous aquatic crocodylomorphs, some of which were probably fully marine [106]. They have classically been placed within Neosuchia, as the sister taxon of Tethysuchia [103, 104].…”

Section: Methodsmentioning

confidence: 99%

The multi-peak adaptive landscape of crocodylomorph body size evolution

et al. 2019

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Background Little is known about the long-term patterns of body size evolution in Crocodylomorpha, the > 200-million-year-old group that includes living crocodylians and their extinct relatives. Extant crocodylians are mostly large-bodied (3–7 m) predators. However, extinct crocodylomorphs exhibit a wider range of phenotypes, and many of the earliest taxa were much smaller (< 1.2 m). This suggests a pattern of size increase through time that could be caused by multi-lineage evolutionary trends of size increase or by selective extinction of small-bodied species. Here, we characterise patterns of crocodylomorph body size evolution using a model fitting-approach (with cranial measurements serving as proxies). We also estimate body size disparity through time and quantitatively test hypotheses of biotic and abiotic factors as potential drivers of crocodylomorph body size evolution. Results Crocodylomorphs reached an early peak in body size disparity during the Late Jurassic, and underwent an essentially continual decline since then. A multi-peak Ornstein-Uhlenbeck model outperforms all other evolutionary models fitted to our data (including both uniform and non-uniform), indicating that the macroevolutionary dynamics of crocodylomorph body size are better described within the concept of an adaptive landscape, with most body size variation emerging after shifts to new macroevolutionary regimes (analogous to adaptive zones). We did not find support for a consistent evolutionary trend towards larger sizes among lineages (i.e., Cope’s rule), or strong correlations of body size with climate. Instead, the intermediate to large body sizes of some crocodylomorphs are better explained by group-specific adaptations. In particular, the evolution of a more aquatic lifestyle (especially marine) correlates with increases in average body size, though not without exceptions. Conclusions Shifts between macroevolutionary regimes provide a better explanation of crocodylomorph body size evolution on large phylogenetic and temporal scales, suggesting a central role for lineage-specific adaptations rather than climatic forcing. Shifts leading to larger body sizes occurred in most aquatic and semi-aquatic groups. This, combined with extinctions of groups occupying smaller body size regimes (particularly during the Late Cretaceous and Cenozoic), gave rise to the upward-shifted body size distribution of extant crocodylomorphs compared to their smaller-bodied terrestrial ancestors. Electronic supplementary material The online version of this article (10.1186/s12862-019-1466-4) contains supplementary material, which is available to authorized users.

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Morphology of the sacral region and reproductive strategies of Metriorhynchidae: a counter-inductive approach

Cited by 27 publications

References 46 publications

Revision of the Late Jurassic deep-water teleosauroid crocodylomorph Teleosaurus megarhinus Hulke, 1871 and evidence of pelagic adaptations in Teleosauroidea

Revision of the Late Jurassic deep-water teleosauroid crocodylomorph Teleosaurus megarhinus Hulke, 1871 and evidence of pelagic adaptations in Teleosauroidea

Inner ear sensory system changes as extinct crocodylomorphs transitioned from land to water

The multi-peak adaptive landscape of crocodylomorph body size evolution

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