Marine Reptiles Research Articles

Special Issue: 100 years of scientific excavations at UNESCO World Heritage Site Monte San Giorgio and global research on Triassic marine Lagerstätten

Only a few Swiss fossil localities are known globally and of which, the UNESCO World Heritage Site Monte San Giorgio, which extends from Switzerland into Italy, is the most important one. Following the discovery of the occurrence of articulated skeletons of marine reptiles in the local mines, large excavations were organized by Bernhard Peyer from the University of Zurich starting 1924. With this collection of articles, we commemorate the successful excavations and research, which initiated the publication of a series of monographies, mostly on the vertebrates but also on the invertebrates of this locality. Especially with the discovery of several remarkably similar Konservat-Lagerstätten in China, the discoveries from Monte San Giorgio gained global relevance. New methodologies such as computed tomography produced a wealth of new data, particularly on endocranial anatomy of several tetrapods.

Validity of Myobradypterygius hauthali von Huene, 1927 (Ichthyosauria: Ophthalmosauria) from the Early Cretaceous of Chile and Argentina

Abstract Early Cretaceous ichthyosaurs were globally distributed pelagic marine reptiles, but many remains are fragmentary, creating a Northern Hemisphere diversity bias. A rich Hauterivian locality near the Tyndall Glacier inside Torres del Paine National Park in southern Chile yields important new data regarding ichthyosaurian diversity along the Pacific margin of Gondwana. These new data will contribute to clarifying questions regarding ichthyosaur taxonomy and the palaeobiogeographical relationships between the southern Gondwanan and Northern Hemisphere ichthyosaur groups during the Early Cretaceous. Here, we describe three new ichthyosaur specimens from this locality. Two of them are referred to Myobradypterygius hauthali, expanding the distribution of this species from the Barremian of Argentina to the Hauterivian of the Chilean Patagonia. This material shows that M. hauthali differs from Platypterygius platydactylus in forefin construction and scapular morphology, supporting its classification as a separate genus within Platypterygiinae. The third specimen is a large-bodied indeterminate ophthalmosaurine ichthyosaur. This record represents the southernmost record of Ophthalmosaurinae and the first occurrence of this group from the Cretaceous of the Southern Hemisphere. These discoveries show that ophthalmosaurines and platypterygiines continued to occur sympatrically in southernmost Gondwana during the Early Cretaceous, expanding the pattern documented in Europe to the Pacific region.

Percentage of Hatching Success of Olive Ridley Turtle (Lepidochelyis oliviceae) Eggs in Natural and Semi-Natural Nests and the Quality of the Turtle Conservation Community (TCC), Lombok, Indonesia

Sea turtles are internationally and nationally protected marine reptiles. One of the turtle species that can be found in Indonesia is the Olive Ridley turtle or Lepidochelys oliviceae. This study aims to determine the percentage of hatching success of turtle eggs in semi-natural and natural nests at TCC (Turtle Conservation Community), Lombok, determine the physical characteristics of natural and semi-natural nests of turtle eggs, and determine the quality of hatchlings produced in natural and semi-natural nests. The research method used is the descriptive exploration method, including determining the location with purposive sampling, collecting data on the size of Olive Ridley turtle mothers, the number of eggs, the depth and diameter of turtle egg nests, beach slope, nest temperature, substrate grains, beach vegetation, threats to turtle eggs, and locomotor quality of hatchlings. The results of this study are, the percentage of success in natural nests of Olive Ridley turtles is lower at 71.99% and semi-natural nests as much as 59.01%. The average temperature of both nests was 28.67, which is still optimal for turtle egg nesting. The type of grain in the two types of nests is also relatively fine. The slope of the beach is also still relatively gentle. Based on the research conducted by TCC (Turtle Conservation Community), it is suitable to support the success of Olive Ridley turtle hatching.

Age and growth rate estimated by skeletochronology in loggerhead sea turtles from French Mediterranean waters

Abstract Skeletochronology was used to determine the ages of 30 loggerhead sea turtles (Caretta caretta) found in French Mediterranean waters. Histological sections were performed with 30 humeri collected on stranded C. caretta on the coast of Provence and the Gulf of Lion. Lines of arrested growth (LAGs) were used to evaluate age, considering only one period of arrested growth per year. Two successive LAGs delimit an interval that is proportional to the individual’s body growth. In a first step, we created a skeletogram for each individual that identified its LAGs. Secondly, we measured the areas delineating successive intervals to determine individual growth patterns over the years. Two methods were used to deduce sea turtle age from histological sections: the correction factor (CF) method and the growth rate (GR) method, the latter using Von Bertalanffy growth function. Age estimations varied from 4.3 to 24.7 years (mean ± SD = 10.1 ± 4.8) with the CF method and from 6.2 to 25.6 years (mean ± SD = 12.2 ± 5.2) with the GR method, with no significant difference between the methods. The study sample was thus mostly composed of juveniles, which is also the most frequent life stage observed in the study area. The annual curved carapace length growth rate calculated with every LAG interval varied from 1.0 to 6.9 cm/year (mean ± SD = 3.5 ± 1.4, ). High variability in interindividual growth rates were observed, which is of interest in understanding the complex lifecycle of these long-lived marine reptiles.

Review of two marine vertebrate assemblages from the Arauco Basin (central Chile) reveals diversity changes throughout the Maastrichtian

Upper Cretaceous vertebrate records from Chile are mostly known by historical mentions with unknown repositories and uncertain stratigraphic provenance. This contribution reviews and complements two marine vertebrate assemblages from the Upper Cretaceous of central Chile, which were part of the ancient Arauco Basin. The oldest assemblage (lower Maastrichtian) comprises abundant condrichthyans referred to Carcharias gracilis, Odontaspis cf. winkleri, Scapanorhynchus sp., Centrophoroides appendiculatus, Squatina sp., Cretorectolobus sp., Orectolobidae indet., Paraorthacodus sp., Ischyrhiza chilensis and Biropristis landbecki, which adds to the previously reported occurrences of Echinorhinus sp. and Myledaphus araucanus. In addition, chimeroids referred to as Edaphodon kawai and remains of a leatherback turtle referable to Mesodermochelys sp. are here described, the latter being its first occurrence outside Japan. The younger assemblage (upper Maastrichtian) includes similar chondrichthyans and a higher diversity of marine reptiles, including plesiosaurians (Aristonectes sp., Aristonectinae indet., and Elasmosauridae indet.), sea turtles (Pancheloniidae indet.) and diverse mosasaurs (Halisaurus sp., Tylosaurinae indet., and the first local occurrence of Plioplatecarpinae indet.). Throughout the Maastrichtian, the local marine vertebrates likely suffered a declination in abundance but a rise in diversity, with evidence of a marked alteration in middle levels of the trophic web during the upper Maastrichtian. This fauna shows a main influence from the northern hemisphere (especially from the Western Interior Sea), acquiring a more marked Weddellian influence during the end of the Maastrichtian. The studied material allows a better understanding of the Upper Cretaceous vertebrate marine fauna in lower latitudes of the southeastern Pacific.

First record of a mosasaurid (Squamata: Mosasauridae) from the Upper Cretaceous of Ecuador

We report the first Upper Cretaceous marine reptile fossil in Ecuador, identified as an incomplete right maxilla from the Mosasauridae family. The remains were unearthed from marine marlstones and limestones within a karstic cave in the Tamia Yura indigenous community, situated northeast of Tena in the central Subandean Zone of the Ecuadorian Amazon. Morphological analysis reveals seven preserved teeth conical in shape. Stratigraphic analysis suggests the remains belong to the Middle Napo Fm, Oriente basin, indicating a presence from the Turonian to the end of the Coniacian. This discovery offers new insights into the study of Cretaceous marine reptiles in South America.

The famous fish beds of Lebanon: the Upper Cretaceous Lagerstätten of Haqel, Hjoula, Nammoura and Sahel Aalma

The fossils of the Lebanese Upper Cretaceous Lagerstätten, especially the articulated fish, are world renowned. Famous for their soft tissue preservation and highly sought after by fossil collectors, Lebanese fossils provide key information concerning the evolution of several major extant and extinct groups of Mesozoic organisms including cephalopods, crustaceans, hagfish, sharks, marine reptiles and pterosaurs. In fact, fossils from Lebanon are so exceptional that historical documentation describing them extends back to the Roman Empire. However, despite over 1600 years of knowledge of these fossils, a thorough understanding of the depositional environments, taphonomy and palaeoecology of the four main sites, Haqel, Hjoula, Nammoura (each Cenomanian in age) and Sahel Aalma (Santonian), is lacking. Here we compile a review of the palaeoenvironments, fauna and flora of these four Lebanese Lagerstätten. Our synthesis outlines the history of fossil discovery, and describes the current understanding of the geology, ages, mode of preservation and organisms found at these four sites. We also undertake a bibliometric and holotype analysis to investigate the impact that scientific colonialism has had on Lebanon. Our data confirm that local Lebanese researchers are typically not included in publications pertaining to Lebanese fossils and that the majority of Lebanese type material is stored in large historical collections outside Lebanon, predominantly in institutions within the northern hemisphere. Here, we recommend some basic practices for researchers utilizing historical collections that can help develop local Lebanese fossil collections and establish more research opportunities for local palaeontologists.

Conodonts suggest a late Spathian (late Early Triassic) age for Thaisaurus chonglakmanii (Reptilia: Ichthyosauromorpha) from Thailand

The timing of the emergence of marine reptiles following the Permian–Triassic mass extinction is crucial for studying the recovery of marine ecosystems in the Triassic. Conodonts, key index fossils in the Triassic, are widely used to date the marine reptiles, especially in the Early Triassic. Triassospathodus anhuinensis is a conodont species originally discovered in the upper Spathian of South China, but lacked a comprehensive description, leading to misidentifications and confusion in previous research. Here, we reevaluated Tr. anhuinensis and summarized its morphological characteristics and spatial and temporal distribution based on a review of the literature. We then critically evaluated the age of the primitive ichthyosaur Thaisaurus chonglakmanii from Thailand based on the updated knowledge of Tr. anhuinensis. We sampled the Khao Thong section where T. chonglakmanii was found for conodont study. Tr. anhuinensis elements were obtained from the bed where T. chonglakmanii was collected and also in the bed five metres above the T. chonglakmanii fossil horizon, suggesting a late Spathian age for T. chonglakmanii. A late Spathian age for T. chonglakmanii questions the hypothesis of Thailand as the place of origin of ichthyosaurs in the late Induan or early Spathain.

Specific marine policies are needed to prevent the extinction of marine reptiles

Specific marine policies are needed to prevent the extinction of marine reptiles

Oldest southern sauropterygian reveals early marine reptile globalization

Sauropterygians were the stratigraphically longest-ranging clade of Mesozoic marine reptiles with a global fossil record spanning ∼180 million years1. However, their early evolution has only been known from what is now the Northern Hemisphere, extending across the northern and trans-equatorial western margins of the Tethys paleo-ocean1 after the late-Early Triassic (late Olenekian, ∼248.8 million years [Ma] ago2), and via possible trans-Arctic migration1 to the Eastern Panthalassa super-ocean prior to the earliest Middle Triassic (Olenekian-earliest Anisian3,4, ∼247 Ma). Here, we describe the geologically oldest sea-going reptile from the Southern Hemisphere - a nothosaur (basal sauropterygian5) from the Middle Triassic (Anisian, after ∼246 Ma6) of New Zealand. Time-scaled ancestral range estimations thus reveal an unexpected circum-Gondwanan high-paleolatitude (>60° S7) dispersal from a northern Tethyan origination center. This coincides with the adaptive diversification of sauropterygians after the end-Permian mass extinction8 and suggests that rapid globalization accompanied their initial radiation in the earliest Mesozoic.

Gigantic gastropods from the Middle Triassic Qingyan biota of Guizhou

Body sizes of organisms underpin their ecological functions and evolutionary trajectories. Previous studies have shown that significant reduction in body size — the Lilliput effect — occurred in the aftermath of the Permian–Triassic mass extinction (PTME) and that body size did not rebound until to the late Middle Triassic (Ladinian). Here we describe three new gastropod specimens, identified as Toxoconcha sp., with unprecedented large shell sizes among Triassic gastropods, from the Qingyan biota of Guizhou, China. Meanwhile, a new dataset on the gastropod size of Lopingian (Late Permian) to Middle Triassic is presented. The largest specimen we found is ∼350 mm in height while its shell volume is estimated to be 1358661 (= 6.13 log10) mm3. As the largest record of the Triassic gastropod shells, these new fossils from Qingyan suggest that gastropod body size rebounded from the post-PTME Lilliput effect as early as the Anisian. Rapid gigantism has been reported in Middle Triassic marine reptiles, and the occurrence of giant gastropods in Qingyan suggests a convergent morphological response to the unique ecological and environmental conditions of the Middle Triassic.

Callovian Marine Reptiles of European Russia

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.

Asymmetric fin shape changes swimming dynamics of ancient marine reptiles’ soft robophysical models

Animals have evolved highly effective locomotion capabilities in terrestrial, aerial, and aquatic environments. Over life’s history, mass extinctions have wiped out unique animal species with specialized adaptations, leaving paleontologists to reconstruct their locomotion through fossil analysis. Despite advancements, little is known about how extinct megafauna, such as the Ichthyosauria one of the most successful lineages of marine reptiles, utilized their varied morphologies for swimming. Traditional robotics struggle to mimic extinct locomotion effectively, but the emerging soft robotics field offers a promising alternative to overcome this challenge. This paper aims to bridge this gap by studying Mixosaurus locomotion with soft robotics, combining material modeling and biomechanics in physical experimental validation. Combining a soft body with soft pneumatic actuators, the soft robotic platform described in this study investigates the correlation between asymmetrical fins and buoyancy by recreating the pitch torque generated by extinct swimming animals. We performed a comparative analysis of thrust and torque generated by Carthorhyncus, Utatsusaurus, Mixosaurus, Guizhouichthyosaurus, and Ophthalmosaurus tail fins in a flow tank. Experimental results suggest that the pitch torque on the torso generated by hypocercal fin shapes such as found in model systems of Guizhouichthyosaurus, Mixosaurus and Utatsusaurus produce distinct ventral body pitch effects able to mitigate the animal’s non-neutral buoyancy. This body pitch control effect is particularly pronounced in Guizhouichthyosaurus, which results suggest would have been able to generate high ventral pitch torque on the torso to compensate for its positive buoyancy. By contrast, homocercal fin shapes may not have been conducive for such buoyancy compensation, leaving torso pitch control to pectoral fins, for example. Across the range of the actuation frequencies of the caudal fins tested, resulted in oscillatory modes arising, which in turn can affect the for-aft thrust generated.

Comparative functional morphology indicates niche partitioning among sympatric marine reptiles.

Mesozoic marine ecosystems were dominated by diverse lineages of aquatic tetrapods. For over 50 Ma in the Jurassic until the Early Cretaceous, plesiosaurians, ichthyosaurians and thalattosuchian crocodylomorphs coexisted at the top levels of trophic food webs. We created a functional dataset of continuous craniomandibular and dental characters known from neontological studies to be functionally significant in modern aquatic tetrapods. We analysed this dataset with multivariate ordination and inferential statistics to assess functional similarities and differences in the marine reptile faunas of two well-sampled Jurassic ecosystems deposited in the same seaway: the Oxford Clay Formation (OCF, Callovian-early Oxfordian, Middle-Late Jurassic) and the Kimmeridge Clay Formation (KCF, Kimmeridgian-Tithonian, Late Jurassic) of the UK. Lower jaw-based macroevolutionary trends are similar to those of tooth-based diversity studies. Closely related species cluster together, with minimal overlaps in the morphospace. Marine reptile lineages were characterized by the distinctive combinations of features, but we reveal multiple instances of morphofunctional convergence among different groups. We quantitatively corroborate previous observations that the ecosystems in the OCF and KCF were markedly distinct in faunal composition and structure. Morphofunctional differentiation may have enabled specialization and was an important factor facilitating the coexistence of diverse marine reptile assemblages in deep time.

The Atlantic Jigsaw Puzzle and the geoheritage of Angola

Abstract The jigsaw-puzzle fit of South America and Africa is an icon of plate tectonics and continental drift. Fieldwork in Angola since 2002 allows the correlation of onshore outcrops and offshore geophysical and well-core data in the context of rift, sag, salt, and post-salt drift phases of the opening of the central South Atlantic. These outcrops, ranging in age from >130 Ma to <71 Ma, record Early Cretaceous outpouring of the Etendeka–Paraná Large Igneous Province (Bero Volcanic Complex) and rifting, followed by continental carbonate and siliciclastic deposition (Tumbalunda Formation) during the sagging of the nascent central South Atlantic basin. By the Aptian, evaporation of sea water resulted in thick salt deposits (Bambata Formation), terminated by seafloor spreading. The Equatorial Atlantic Gateway began opening by the early Late Cretaceous (100 Ma) and allowed flow of currents between the North and South Atlantic, creating environmental conditions that heralded the introduction of marine reptiles. These dramatic outcrops are a unique element of geoheritage because they arguably comprise the most complete terrestrially exposed geological record of the puzzle-like icon of continental drift.

Cymbospondylus (Ichthyopterygia) from the Early Triassic of Svalbard and the early evolution of large body size in ichthyosaurs

Ichthyosaurs were a highly successful group of marine reptiles in the Mesozoic. The ichthyosaur radiation is part of the recovery from the Permian-Triassic mass extinction. In the Early Triassic, this group underwent extensive global radiation, filling ecological niches for the first time that were later occupied by various other lineages of marine amniotes. However, the evolution of body size in ichthyosaurs is not fully understood, as most large-bodied taxa originate from the Middle Triassic and later, and are mostly known from only a few specimens. In this study, we describe three articulated posterior dorsal vertebrae (IGPB R660) of the ichthyosaur Cymbospondylus sp. from the latest Olenekian Keyserlingites subrobustus zone of the Vikinghøgda Formation of the Agardhdalen area, eastern Spitsbergen, Svalbard. We numerically estimated the total body length of IGPB R660 from dorsal vertebral centrum length using a comparative dataset of other species of the genus and two different allometric analyses. This approach yields total length estimates of 7.5 m and 9.5 m for the individual, respectively, the highest for any unambiguous Early Triassic ichthyosaur find. Earlier, higher estimates of 11 m were based on taxonomically and stratigraphically inconclusive material but do not appear unreasonable based on evidence provided in this paper. Our study underscores both the rapid ecosystem recovery after a major mass extinction and extremely rapid increases in body size in ichthyosaurs after their adaptation to a secondarily aquatic lifestyle.

The multidimensional spectrum of eco-evolutionary relationships between sharks and remoras.

Remoras are a highly specialised group of fishes known to associate with a range of marine megafauna, including elasmobranchs, cetaceans and marine reptiles. Remoras appear to benefit from these interspecific interactions through consumption of host dermal parasites or reduced cost of transport. Shark-remora associations are widely documented, yet our understanding of the costs and benefits involved in these interactions is poor. Studies frequently make claims about mutualistic, commensalistic or parasitic relationships without providing the necessary quantitative information necessary to make these claims. Here I explain why this approach is problematic, and proceed to examine shark-remora interactions in a rigorous eco-evolutionary framework. These interactions cannot be properly classified without considering net evolutionary fitness and context dependence. In reality, shark-remora interactions are best defined by a multidimensional spectrum of fitness consequences, with net fitness outcomes shifting between mutualism and parasitism (and vice versa) through space and time.

New occurrences of the bone-eating worm Osedax from Late Cretaceous marine reptiles and implications for its biogeography and diversification.

The bone-eating worm Osedax is a speciose and globally distributed clade, primarily found on whale carcasses in marine environments. The earliest fossil evidence for Osedax borings was previously described in plesiosaur and sea turtle bones from the mid-Cretaceous of the United Kingdom, representing the only unequivocal pre-Oligocene occurrences. Confirming through CT scanning, we present new evidence of Osedax borings in three plesiosaur specimens and, for the first time, identify borings in two mosasaur specimens. All specimens are from the Late Cretaceous: one from the Cenomanian of the United Kingdom, two from the Campanian of the southeastern United States, and two from the Maastrichtian of Belgium. This extends the geographic range of Osedax in the Cretaceous to both sides of the northern Atlantic Ocean. The bones contain five borehole morphotypes, potentially created by different species of Osedax, with the Cenomanian specimen containing three morphotypes within a single tooth. This combined evidence of heightened species diversity by the Cenomanian and broad geographic range by the Campanian potentially indicates an earlier origin and diversification for this clade than previously hypothesized. Preservational biases indicate that Osedax was probably even more widely distributed and speciose in the Cretaceous than apparent in the fossil record.

Oldest record of Machimosaurini (Thalattosuchia, Teleosauroidea): teeth and scavenging traces from the Middle Jurassic (Bajocian) of Switzerland.

The Jurassic period was a time of major diversification for Mesozoic marine reptiles, including Ichthyosauria, Plesiosauria and thalattosuchian Crocodylomorpha. The latter originated in the Early Jurassic and thrived during the Late Jurassic. Unfortunately, the Middle Jurassic, a crucial time in their evolution, has a poor fossil record. Here, we document the first evidence of macrophagous/durophagous Machimosaurini-tribe teleosauroid thalattosuchians from the late Bajocian (ca 169 Ma) in the form of three robust tooth crowns with conical blunt shapes and anastomosed pattern of thick enamel ridges towards the apex, associated with the skeleton of a large ichthyosaur lacking preserved tooth crowns. The tooth crowns were found on the posterior section of the lower jaw (left angular), a lacrimal and the axis neural arch of the ichthyosaur. In addition, some of the distal sections of the posterior dorsal ribs of the ichthyosaur skeleton exhibit rounded bite marks and some elongated furrows that fit in size and shape with the Machimosaurini teeth. These marks, together with the absence of healing in the rib bone are interpreted here as the indicators of peri- to post-mortem scavenging by a Machimosaurini teleosauroid after the large ichthyosaur carcass settled on the floor of a shallow ocean.

A large new Middle Jurassic ichthyosaur shows the importance of body size evolution in the origin of the Ophthalmosauria

The Middle Jurassic is an important time period for the evolutionary history of marine reptiles as it represented a transitional phase for many clades. Notably, in ichthyosaurs, many early parvipelvian taxa went extinct. The Middle Jurassic saw the emergence of the derived Ophthalmosauria, ultimately becoming the dominant ichthyosaurian clade by the end of the epoch. Even though this is an important period in the evolutionary history of Ophthalmosauria, our understanding remains limited in terms of morphology and taxonomy due to the scarcity of vertebrate-bearing strata. Here we present a large new ichthyosaur from the Bajocian of Switzerland, represented by an almost complete skull with 3D-preserved bones, the (inter)clavicles and a large portion of the postcranial skeleton. After CT- and surface scanning, we reconstructed the 3D in vivo morphology. Our morphological observations and phylogenetic analyses show that the new taxon named Argovisaurus martafernandezi is nested at the base of the Ophthalmosauria. The holotype and only known specimen of Argovisaurus likely represents an adult individual. Bajocian members of the Ophthalmosauria (Mollesaurus and Argovisaurus) were large-bodied animals, a trait typically associated with the more derived Platypterygiinae. This hints at the importance of a large body size early in ophthalmosaurian evolution.LSID: urn:lsid:zoobank.org:act:C3312628-1544-4B87-BBE3-B12346A30BE3LSID: urn:lsid:zoobank.org:act:23C2BD71-8CF0-4D99-848A-0D631518415B