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Making New Out of the Old: Recent Biological Advances on...
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Making New Out of the Old: Recent Biological Advances on Mesozoic Marine Reptiles

A special issue of Diversity (ISSN 1424-2818). This special issue belongs to the section "Phylogeny and Evolution".

Deadline for manuscript submissions: closed (31 March 2024) | Viewed by 25514

Image courtesy of Benjamin Waterhouse Hawkins

Special Issue Editor

Dr. Nathalie Bardet

E-Mail Website
Guest Editor
Centre de Recherche en Paléontologie de Paris, UMR 7207 - CNRS, MNHN, SU, Muséum National d’Histoire Naturelle, CP 38 – 57 rue Cuvier, 75005 Paris, France
Interests: systematics; phylogeny; palaeobiogeography; palaeobiology; palaeoecology and science history of Late Cretaceous marine reptiles from the northern and southern margins of the Mediterranean Tethys

Special Issue Information

Dear Colleagues,

A secondary return to aquatic life is a major evolutionary phenomenon in vertebrate history. Although some pioneers returned to aquatic life by the end of the Paleozoic era, this phenomenon is best illustrated during the Mesozoic (with reptiles) and Cenozoic (with mammals) eras.

During the Mesozoic era, about ten clades of reptiles underwent a dramatic return to aquatic life; in doing so, they colonized most marine environments, exhibiting great systematic diversity and astonishing ecological disparity. Many were among the greatest marine predators of their time, and some, such as ichthyosaurs, plesiosaurs and mosasaurs, were iconic clades of large Mesozoic ‘gigantic saurians’ that mirrored terrestrial dinosaurs.

These marine reptiles illustrate a mosaic of morphological, physiological and ecological adaptations to an aquatic lifestyle, some of which are convergent with those found in Cenozoic marine mammals, and others completely unique.

This volume aims to present recent biological advances made through the discovery of exceptionally preserved specimens and/or the use of modern methods. As such, it will focus mainly (but not exclusively) on topics such as locomotion modes and sensory systems, physiology and metabolism, reproduction and predation modes, and soft tissues and colors.

Dr. Nathalie Bardet
Guest Editor

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Keywords

  • Mesozoic
  • marine reptiles
  • biology

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Published Papers (9 papers)

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Research

27 pages, 3438 KiB  
Article
The Evolution of Mosasaurid Foraging Behavior Through the Lens of Stable Carbon Isotopes
by Michael J. Polcyn, John A. Robbins, Anne S. Schulp, Johan Lindgren and Louis L. Jacobs
Diversity 2025, 17(4), 291; https://doi.org/10.3390/d17040291 - 19 Apr 2025
Viewed by 1368
Abstract
A large data set of new and previously published measurements of δ13C values derived from tooth enamel (n = 223, of which 93 are new) are compiled to explore patterns of foraging area preferences of Late Cretaceous mosasaurid squamates over [...] Read more.
A large data set of new and previously published measurements of δ13C values derived from tooth enamel (n = 223, of which 93 are new) are compiled to explore patterns of foraging area preferences of Late Cretaceous mosasaurid squamates over evolutionary time scales (~93–66 Ma). Our results indicate that small-bodied halisaurines are restricted to a relatively nearshore range, overlapping the lower end of the range of plioplatecarpines and some mosasaurine taxa. Most moderately sized plioplatecarpines occupy a relatively narrow foraging area in much of the nearshore and proximal offshore marine foraging area for the majority of their existence. Tylosaurines exhibit a greater offshore marine range than plioplatecarpines, consistent with their large body size and the robustness of their feeding apparatus. The largest tylosaurine taxa are replaced by Mosasaurus in the Late Campanian–Maastrichtian in the offshore foraging range. Mosasaurine taxa are found to occupy the broadest range of foraging areas, but their ranges are taxonomically segregated, consistent with adult body size and the diversity of feeding adaptations such as tooth morphologies and skull architecture seen in that subfamily. Where foraging areas of multiple taxa overlap, differences are typically in tooth form, reflecting prey preference or feeding niche. Foraging area occupation by multiple taxa with similar tooth forms suggests that other factors such as body size and prey acquisition style may have allowed for the finer partitioning of resources. Deep diving and long submergence may have also contributed to the depleted signals recovered for some of the large-bodied durophages and the largest of the macrophagous apex predators. Full article
(This article belongs to the Special Issue Making New Out of the Old: Recent Biological Advances on Mesozoic Marine Reptiles)
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14 pages, 2945 KiB  
Article
Mosasaur Feeding Ecology from the Campanian Bearpaw Formation, Alberta, Canada: A Preliminary Multi-Proxy Approach
by Femke M. Holwerda, Mark T. Mitchell, Madelon van de Kerk and Anne S. Schulp
Diversity 2025, 17(3), 205; https://doi.org/10.3390/d17030205 - 13 Mar 2025
Cited by 1 | Viewed by 2296
Abstract
Mosasaur taxa recovered from the Bearpaw Formation, Alberta, Canada, generally show exceptional preservation after rapid burial. Since the mosasaur community consisted of two dominant taxa, Mosasaurus missourensis Prognathodon overtoni, and three less prevalent taxa Tylosaurus proriger, Mosasaurus conodon, and Plioplatecarpus [...] Read more.
Mosasaur taxa recovered from the Bearpaw Formation, Alberta, Canada, generally show exceptional preservation after rapid burial. Since the mosasaur community consisted of two dominant taxa, Mosasaurus missourensis Prognathodon overtoni, and three less prevalent taxa Tylosaurus proriger, Mosasaurus conodon, and Plioplatecarpus primaevus, some form of habitat or dietary niche partitioning is to be expected. To test this, several approaches are tried. Two-dimensional microwear analysis is used as an exploratory method to quantify tooth abrasion by food items. The good preservation of skull material reveals complete tooth rows of the upper and lower jaws for Mosasaurus missouriensis and Prognathodon overtoni, as well as isolated teeth for all taxa. The teeth are also measured for tooth bending strength to test stress regarding usage of teeth per taxon. Energy-dispersive X-ray spectroscopy (EDX) measurements show trace elements which may be a preliminary test for relative trophic level positioning. Some mosasaurs have their stomach contents preserved, providing direct and unambiguous evidence of diet. The results show a relatively clear separation of two-dimensional microwear counts between Mosasaurus, Prognathodon, and Plioplatecarpus, which, to some extent, is reflected in the EDX analyses, too. Tooth bending strength measurements show a clear difference between the latter three mosasaurs but no difference between the lower and upper jaws in Mosasaurus or Prognathodon. The combination of these three techniques maps a clear dietary niche differentiation of Bearpaw mosasaurs, which lays the groundwork for future analytical or chemical palaeoecological studies. Full article
(This article belongs to the Special Issue Making New Out of the Old: Recent Biological Advances on Mesozoic Marine Reptiles)
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47 pages, 5005 KiB  
Article
Mosasaurids Bare the Teeth: An Extraordinary Ecological Disparity in the Phosphates of Morocco Just Prior to the K/Pg Crisis
by Nathalie Bardet, Valentin Fischer, Nour-Eddine Jalil, Fatima Khaldoune, Oussama Khadiri Yazami, Xabier Pereda-Suberbiola and Nicholas Longrich
Diversity 2025, 17(2), 114; https://doi.org/10.3390/d17020114 - 4 Feb 2025
Viewed by 2158
Abstract
Mosasaurid teeth are abundant in the fossil record and often diagnostic to low taxonomic levels, allowing to document the taxonomic diversity and ecological disparity through time and with fewer biases than in other marine reptiles. The upper Maastrichtian Phosphates of Morocco, with at [...] Read more.
Mosasaurid teeth are abundant in the fossil record and often diagnostic to low taxonomic levels, allowing to document the taxonomic diversity and ecological disparity through time and with fewer biases than in other marine reptiles. The upper Maastrichtian Phosphates of Morocco, with at least fifteen coeval species representing a wide range of sizes and morphologies, undoubtedly represent the richest outcrop in the world for this clade of iconic Mesozoic squamates and one of the richest known marine tetrapod assemblages. Until now, the methods used to link tooth morphology to diets in marine amniotes were mainly qualitative in nature. Here, using the dental morphology of mosasaurids from Morocco, we combine two complementary approaches—a thorough comparative anatomical description and 2D/3D geometric morphometry—to quantitatively categorize the main functions of these teeth during feeding processes and infer diet preferences and niche-partitioning of these apex predators. Our results from combining these two approaches show the following: (1) Mosasaurids from the upper Maastrichtian Phosphates of Morocco occupy the majority of dental guilds ever colonized by Mesozoic marine reptiles. (2) As seen elsewhere in the Maastrichtian, mosasaurines dominate the regional mosasaurid assemblage, exhibiting the greatest taxonomic diversity (two-thirds of the species) and the largest range of morphologies, body sizes (2 m to more than 10 m) and ecological disparities (participating in nearly all predatory ecological guilds); strikingly, mosasaurines did not developed flesh piercers and, conversely, are the only ones to include durophagous species. (3) Halisaurines, though known by species of very different sizes (small versus large) and cranial morphologies (gracile versus robust), maintain a single tooth shape (piercer). (4) Plioplatecarpines were medium-size cutters and piercers, known by very morphologically diverging species. (5) Tylosaurines currently remain scarce, represented by a very large generalist species; they were largely replaced by mosasaurines as apex predators over the course of the Maastrichtian, as observed elsewhere. Also, when comparing tooth shapes with body sizes, the largest taxa (>8 m long) occupied a restricted area of tooth shapes (generalist, durophagous), whereas small and medium-sized species (<8 m long) range across all of them (generalists, durophagous, cutters, piercers). In other words, and probably related to the specificities and advantages of biomechanical resistance, apex predators are never dedicated piercers, micro-predators are conversely never generalists, and meso-predators show the widest range of dental adaptations. These diversities and disparities strongly suggest that Tethyan mosasaurids evolved strong niche-partitioning in the shallow marine environment of the upper Maastrichtian Phosphates of Morocco. Such a high diversity sensu lato just prior to the K/Pg biological crisis suggests that their extinction was rather sudden, though the exact causes of their extinction remain unknown. Finally, Gavialimimus Strong et al., 2020 is systematically reassigned to Gavialimimus ptychodon (Arambourg, 1952), and an emended diagnosis (for teeth and dentition) is proposed for this species. Full article
(This article belongs to the Special Issue Making New Out of the Old: Recent Biological Advances on Mesozoic Marine Reptiles)
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16 pages, 3588 KiB  
Article
First Virtual Reconstruction of a Mosasaurid Brain Endocast: Description and Comparison of the Endocast of Tethysaurus nopcsai with Those of Extant Squamates
by Rémi Allemand, Michael J. Polcyn, Alexandra Houssaye, Peggy Vincent, Camilo López-Aguirre and Nathalie Bardet
Diversity 2024, 16(9), 548; https://doi.org/10.3390/d16090548 - 5 Sep 2024
Viewed by 2492
Abstract
Paleoneurological studies of mosasaurids are few and limited to old partial reconstructions made from latex casts on Platecarpus and Clidastes. Here, the brain endocasts of three specimens of the early mosasaurid Tethysaurus nopcsai from the Turonian of Morocco are reconstructed for the [...] Read more.
Paleoneurological studies of mosasaurids are few and limited to old partial reconstructions made from latex casts on Platecarpus and Clidastes. Here, the brain endocasts of three specimens of the early mosasaurid Tethysaurus nopcsai from the Turonian of Morocco are reconstructed for the first time by using micro-computed tomography. Comparisons between Tethysaurus and the later Platecarpus and Clidastes show that distinct endocranial organizations have occurred within the clade through time, including differences in the flexure of the endocast and the size of the parietal eye. The physiological consequences of such variability remain unclear and further investigations are required to better interpret these variations. In addition, the endocast of Tethysaurus was compared to those of extant anguimorphs, iguanians, and snakes, using landmark-based geometric morphometrics. The results revealed that Tethysaurus exhibits a unique combination of endocranial features compared to extant toxicoferans. Contrary to previous statements, we find no strong resemblance in endocast morphology between Tethysaurus and varanids. Rather, the endocast of Tethysaurus shows some morphological similarities with each of the clades of anguimorphs, iguanians, and snakes. In this context, while a notable phylogenetic signal is observed in the variability of squamate endocasts, it is premature to establish any phylogenetic affinities between mosasaurids and extant squamates based solely on endocast morphologies. Full article
(This article belongs to the Special Issue Making New Out of the Old: Recent Biological Advances on Mesozoic Marine Reptiles)
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16 pages, 15119 KiB  
Article
Skin Anatomy, Bone Histology and Taphonomy of a Toarcian (Lower Jurassic) Ichthyosaur (Reptilia: Ichthyopterygia) from Luxembourg, with Implications for Paleobiology
by Ida Bonnevier Wallstedt, Peter Sjövall, Ben Thuy, Randolph G. De La Garza, Mats E. Eriksson and Johan Lindgren
Diversity 2024, 16(8), 492; https://doi.org/10.3390/d16080492 - 12 Aug 2024
Viewed by 3137
Abstract
A partial ichthyosaur skeleton from the Toarcian (Lower Jurassic) bituminous shales of the ‘Schistes Carton’ unit of southern Luxembourg is described and illustrated. In addition, associated remnant soft tissues are analyzed using a combination of imaging and molecular techniques. The fossil (MNHNL TV344) [...] Read more.
A partial ichthyosaur skeleton from the Toarcian (Lower Jurassic) bituminous shales of the ‘Schistes Carton’ unit of southern Luxembourg is described and illustrated. In addition, associated remnant soft tissues are analyzed using a combination of imaging and molecular techniques. The fossil (MNHNL TV344) comprises scattered appendicular elements, together with a consecutive series of semi-articulated vertebrae surrounded by extensive soft-tissue remains. We conclude that TV344 represents a skeletally immature individual (possibly of the genus Stenopterygius) and that the soft parts primarily consist of fossilized skin, including the epidermis (with embedded melanophore pigment cells and melanosome organelles) and dermis. Ground sections of dorsal ribs display cortical microstructures reminiscent of lines of arrested growth (LAGs), providing an opportunity for a tentative age determination of the animal at the time of death (>3 years). It is further inferred that the exceptional preservation of TV344 was facilitated by seafloor dysoxia/anoxia with periodical intervals of oxygenation, which triggered phosphatization and the subsequent formation of a carbonate concretion. Full article
(This article belongs to the Special Issue Making New Out of the Old: Recent Biological Advances on Mesozoic Marine Reptiles)
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12 pages, 6664 KiB  
Article
Bone Connectivity and the Evolution of Ichthyosaur Fins
by Marta S. Fernández, Lisandro Campos, Agustina Manzo and Evangelos Vlachos
Diversity 2024, 16(6), 349; https://doi.org/10.3390/d16060349 - 17 Jun 2024
Viewed by 3146
Abstract
After the end-Triassic extinction, parvipelvian ichthyosaurs diversified and became dominant elements of marine ecosystems worldwide. By the Early Jurassic, they achieved a thunniform body plan that persisted for the last 100 m.y.a of their evolution. Diversification and extinctions of thunniform ichthyosaurs, and their [...] Read more.
After the end-Triassic extinction, parvipelvian ichthyosaurs diversified and became dominant elements of marine ecosystems worldwide. By the Early Jurassic, they achieved a thunniform body plan that persisted for the last 100 m.y.a of their evolution. Diversification and extinctions of thunniform ichthyosaurs, and their swimming performance, have been studied from different perspectives. The transformation of limbs into hydrofoil-like structures for better control and stability during swimming predates thunniform locomotion. Despite their importance as control surfaces, fin evolution among thunnosaurs remains poorly understood. We explore ichthyosaur fin diversity using anatomical networks. Our results indicate that, under a common hydrofoil controller fin, the bone arrangement diversity of the ichthyosaur fin was greater than traditionally assumed. Changes in the connectivity pattern occurred stepwise throughout the Mesozoic. Coupled with other lines of evidence, such as the presence of a ball-and-socket joint at the leading edge of some derived Platypterygiinae, we hypothesize that fin network disparity also mirrored functional disparity likely associated with different capabilities of refined maneuvering. The ball-and-socket articulation indicates that this local point could be acting like a multiaxial intrafin joint changing the angle of attack and thus affecting the maneuverability, similar to the alula of flying birds. Further studies on large samples and quantitative experimental approaches would be worthy to test this hypothesis. Full article
(This article belongs to the Special Issue Making New Out of the Old: Recent Biological Advances on Mesozoic Marine Reptiles)
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48 pages, 65909 KiB  
Article
Callovian Marine Reptiles of European Russia
by Nikolay Zverkov, Maxim Arkhangelsky, Denis Gulyaev, Alexey Ippolitov and Alexey Shmakov
Diversity 2024, 16(5), 290; https://doi.org/10.3390/d16050290 - 10 May 2024
Cited by 2 | Viewed by 2805
Abstract
Our knowledge of marine reptiles of the Callovian age (Middle Jurassic) is majorly based on the collections from the Oxford Clay Formation of England, which yielded a diverse marine reptile fauna of plesiosaurians, ichthyosaurians, and thalattosuchians. However, outside of Western Europe, marine reptile [...] Read more.
Our knowledge of marine reptiles of the Callovian age (Middle Jurassic) is majorly based on the collections from the Oxford Clay Formation of England, which yielded a diverse marine reptile fauna of plesiosaurians, ichthyosaurians, and thalattosuchians. However, outside of Western Europe, marine reptile remains of this age are poorly known. Here, we survey marine reptiles from the Callovian stage of European Russia. The fossils collected over more than a century from 28 localities are largely represented by isolated bones and teeth, although partial skeletons are also known. In addition to the previously described rhomaleosaurid and metriorhynchids, we identify pliosaurids of the genera Liopleurodon and Simolestes; cryptoclidid plesiosaurians, including Cryptoclidus eurymerus, Muraenosaurus sp., and cf. Tricleidus, and ophthalmosaurid ichthyosaurians, including the iconic Ophthalmosaurus icenicus. These findings expand the ranges of several Callovian marine reptile taxa far to the Eastern Europe, and support the exchange of marine reptile faunas between Western and Eastern European seas in the middle to late Callovian. However, some specimens from the lower Callovian of European Russia show differences from typical representatives of the middle Callovian Oxford Clay fauna, possibly representing the earlier stages of evolution of some of these marine reptiles not yet recorded in Western Europe or elsewhere. Full article
(This article belongs to the Special Issue Making New Out of the Old: Recent Biological Advances on Mesozoic Marine Reptiles)
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12 pages, 8443 KiB  
Article
Exceptional In Situ Preservation of Chondrocranial Elements in a Coniacian Mosasaurid from Colombia
by María Eurídice Páramo-Fonseca, José Alejandro Narváez-Rincón, Cristian David Benavides-Cabra and Christian Felipe Yanez-Leaño
Diversity 2024, 16(5), 285; https://doi.org/10.3390/d16050285 - 10 May 2024
Cited by 1 | Viewed by 3018
Abstract
The first record of well-preserved chondrocranial elements in mosasaurids is here described. These elements are preserved in situ in a Coniacian skull found in north-central Colombia, inside a calcareous concretion. Based on a 3D model generated from computed tomography scans, we identified elements [...] Read more.
The first record of well-preserved chondrocranial elements in mosasaurids is here described. These elements are preserved in situ in a Coniacian skull found in north-central Colombia, inside a calcareous concretion. Based on a 3D model generated from computed tomography scans, we identified elements of the nasal and orbitotemporal regions. Our descriptions show that in this specimen, the chondrocranium was reduced, more so than in most lacertilians (including their closest recent relatives, the varanids), but not as severely as in snakes or amphisbaenians (which have an extremely reduced chondrocranium and limbs). The new evidence suggests that the reduction in the chondrocranium in mosasaurids could be related to modification of their limbs when adapting to aquatic environments, but also that in mosasaurids, the olfactory tract was reduced, and the optic muscle insertions occurred mainly in the interorbital septum. The exceptional preservation of the chondrocranial elements in the specimen is facilitated by a gray mineralization covering them. XRD analysis and thin section observations indicated that this mineralization is composed of microcrystalline quartz and calcite. We infer that this material was produced by a partial silicification process promoted by lower pH microenvironments associated with bacterial breakdown of non-biomineralized tissues during early diagenesis. Full article
(This article belongs to the Special Issue Making New Out of the Old: Recent Biological Advances on Mesozoic Marine Reptiles)
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19 pages, 5577 KiB  
Article
How Elongated? The Pattern of Elongation of Cervical Centra of Elasmosaurus platyurus with Comments on Cervical Elongation Patterns among Plesiosauromorphs
by José Patricio O’Gorman
Diversity 2024, 16(2), 106; https://doi.org/10.3390/d16020106 - 7 Feb 2024
Viewed by 3708
Abstract
Elasmosaurids comprise some of the most extreme morphotypes of plesiosaurs. Thus, the study of their neck and vertebrae elongation patterns plays a crucial role in understanding the anatomy of elasmosaurids. In this study, the taphonomic distortion of the holotype of Elasmosaurus platyurus and its [...] Read more.
Elasmosaurids comprise some of the most extreme morphotypes of plesiosaurs. Thus, the study of their neck and vertebrae elongation patterns plays a crucial role in understanding the anatomy of elasmosaurids. In this study, the taphonomic distortion of the holotype of Elasmosaurus platyurus and its effects on the vertebral length index (VLI) values are evaluated, and a new index to describe the neck is proposed (MAVLI = mean value of the vertebral elongation index of the anterior two-thirds of neck vertebrae). The results provide a strong foundation for a new scheme of neck elongation patterns that divide the diversity of the neck elongation of plesiosauriomorphs into three categories: not-elongate (MAVLI < 95 and Max VLI < 100), elongate (125 > MAVLI > 95 and 100 < Max VLI < 135), and extremely elongated (MAVLI > 125 and Max VLI > 135). Full article
(This article belongs to the Special Issue Making New Out of the Old: Recent Biological Advances on Mesozoic Marine Reptiles)
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