Litorosuchus somnii: A new Armored and Aquatic Archosauriform From Ladinian Triassic China

A new armored archosauriform (Diapsida: Archosauromorpha) from the marine Middle Triassic of China, with implications for the diverse life styles of archosauriforms prior to the diversification of Archosauria

Authors:

Li et al

Abstract:

Reptiles have a long history of transitioning from terrestrial to semi-aquatic or aquatic environments that stretches back at least 250 million years. Within Archosauria, both living crocodylians and birds have semi-aquatic members. Closer to the root of Archosauria and within the closest relatives of the clade, there is a growing body of evidence that early members of those clades had a semi-aquatic lifestyle. However, the morphological adaptations to a semi-aquatic environment remain equivocal in most cases. Here, we introduce a new Middle Triassic (245–235 Ma) archosauriform, Litorosuchus somnii, gen. et sp. nov., based on a nearly complete skeleton from the Zhuganpo Member (Ladinian [241–235 Ma]) of the Falang Formation, Yunnan, China. Our phylogenetic analyses suggest that Litorosuchus is a stem archosaur closely related to the aberrant Vancleavea just outside of Archosauria. The well-preserved skeleton of L. somnii bears a number of morphological characters consistent with other aquatic-adapted tetrapods including: a dorsally directed external naris, tall neural spines and elongate chevrons in an elongated tail, a short and broad scapula, webbed feet, long cervical vertebrae with long slender ribs, and an elongated rostrum with long and pointed teeth. Together these features represent one of the best-supported cases of a semi-aquatic mode of life for a stem archosaur. Together with Vancleavea campi, the discovery of L. somnii demonstrates a growing body of evidence that there was much more diversity in mode of life outside Archosauria. Furthermore, L. somnii helps interpret other possible character states consistent with a semi-aquatic mode of life for archosauriforms, including archosaurs.

Ichthyosaurs Went Extinct due to Extreme Global Warming

Why ichthyosaurs — marine Mesozoic reptiles — disappeared before the dinosaur extinction has remained a mystery. New research suggests they may have gone extinct stepwise, during one of the most extreme greenhouse periods in the history of complex life-forms.

link.

Sclerocormus: a new Ichthyosauriform from Spathian Triassic China

A large aberrant stem ichthyosauriform indicating early rise and demise of ichthyosauromorphs in the wake of the end-Permian extinction

Authors:

Jiang et al

Abstract:

Contrary to the fast radiation of most metazoans after the end-Permian mass extinction, it is believed that early marine reptiles evolved slowly during the same time interval. However, emerging discoveries of Early Triassic marine reptiles are questioning this traditional view. Here we present an aberrant basal ichthyosauriform with a hitherto unknown body design that suggests a fast radiation of early marine reptiles. The new species is larger than coeval marine reptiles and has an extremely small head and a long tail without a fluke. Its heavily-built body bears flattened and overlapping gastral elements reminiscent of hupehsuchians. A phylogenetic analysis places the new species at the base of ichthyosauriforms, as the sister taxon of Cartorhynchus with which it shares a short snout with rostrally extended nasals. It now appears that ichthyosauriforms evolved rapidly within the first one million years of their evolution, in the Spathian (Early Triassic), and their true diversity has yet to be fully uncovered. Early ichthyosauromorphs quickly became extinct near the Early-Middle Triassic boundary, during the last large environmental perturbation after the end-Permian extinction involving redox fluctuations, sea level changes and volcanism. Marine reptile faunas shifted from ichthyosauromorph-dominated to sauropterygian-dominated composition after the perturbation.

Ecomorphological diversifications of Mesozoic marine reptiles

Ecomorphological diversifications of Mesozoic marine reptiles: the roles of ecological opportunity and extinction

Authors:

Stubbs et al

Abstract:

Mesozoic marine ecosystems were dominated by several clades of reptiles, including sauropterygians, ichthyosaurs, crocodylomorphs, turtles, and mosasaurs, that repeatedly invaded ocean ecosystems. Previous research has shown that marine reptiles achieved great taxonomic diversity in the Middle Triassic, as they broadly diversified into many feeding modes in the aftermath of the Permo-Triassic mass extinction, but it is not known whether this initial phase of evolution was exceptional in the context of the entire Mesozoic. Here, we use a broad array of disparity, morphospace, and comparative phylogenetic analyses to test this. Metrics of ecomorphology, including functional disparity in the jaws and dentition and skull-size diversity, show that the Middle to early Late Triassic represented a time of pronounced phenotypic diversification in marine reptile evolution. Following the Late Triassic extinctions, diversity recovered, but disparity did not, and it took over 100 Myr for comparable variation to recover in the Campanian and Maastrichtian. Jurassic marine reptiles generally failed to radiate into vacated functional roles. The signatures of adaptive radiation are not seen in all marine reptile groups. Clades that diversified during the Triassic biotic recovery, the sauropterygians and ichthyosauromorphs, do show early diversifications, early high disparity, and early burst, while less support for these models is found in thalattosuchian crocodylomorphs and mosasaurs. Overall, the Triassic represented a special interval in marine reptile evolution, as a number of groups radiated into new adaptive zones.

Atopodentatus unicus: The Earliest Known Herbivorous Marine Reptile From Anisian Triassic China

The earliest herbivorous marine reptile and its remarkable jaw apparatus

Authors:

Chun et al

Abstract:

Newly discovered fossils of the Middle Triassic reptile Atopodentatus unicus call for a radical reassessment of its feeding behavior. The skull displays a pronounced hammerhead shape that was hitherto unknown. The long, straight anterior edges of both upper and lower jaws were lined with batteries of chisel-shaped teeth, whereas the remaining parts of the jaw rami supported densely packed needle-shaped teeth forming a mesh. The evidence indicates a novel feeding mechanism wherein the chisel-shaped teeth were used to scrape algae off the substrate, and the plant matter that was loosened was filtered from the water column through the more posteriorly positioned tooth mesh. This is the oldest record of herbivory within marine reptiles.

Dawazisaurus brevis: a new Middle Triassic Eosauropterygian From China

Dawazisaurus Brevis, A New Eosauropterygian From the Middle Triassic of Yunnan, China

Authors:

Chen et al

Abstract:


Dawazisaurus brevis (gen. et sp. nov.) is a newly discovered Triassic marine reptile, represented by a complete skeleton from Member II of the Guanling Formation of Luoping, Yunnan Province, China. This paper aims to (1) present a thorough description of the species, (2) make a detailed comparison to demonstrate if the species can be referred to any known sauropterygian taxa, and (3) conduct phylogenetic analyses to establish the internal relationships of the species with other sauropterygians. In addition, the discovery of Dawazisaurus provides a chance not only to test the phylogenetic patterns of the Sauropterygia obtained by previous studies but also to evaluate the previous hypotheses on the origin of the sauropterygian groups at different levels. D. brevis is an eosauropterygian, characterized by a unique combination of derived features such as a pair of large nasals joining in the formation of the internarial septum, a short trunk with 16 dorsal vertebrae; the zygapophyses of the trunk vertebrae very small or weakly developed; the posterior margin of the skull roof deeply V-shaped, and an ossified distal carpal 5. Phylogenetic analysis indicates that D. brevis appears to be more closely related to the Nothosauroidea than the Pistosauroidea within the Eosauropterygia.

Were Mosasaurs Warm Blooded?

Endothermic mosasaurs? Possible thermoregulation of Late Cretaceous mosasaurs (Reptilia, Squamata) indicated by stable oxygen isotopes in fossil bioapatite in comparison with coeval marine fish and pelagic seabirds

Authors:

Lynn Harrell et al

Abstract:

The thermoregulatory style of Late Cretaceous mosasaurs has become a highly controversial subject in vertebrate palaeontology. These extinct marine reptiles have previously been described as poikilothermic, endothermic or gigantothermic. Here we analyse three genera of mosasaurs from the Mooreville Chalk in Alabama (USA) of differing body mass, and compare their δ18OPO4 derived body temperatures (Tb) with those of coeval poikilothermic fish (Enchodus) and endothermic pelagic seabirds (Ichthyornis). Results show that all mosasaurs, Clidastes (Tb = 33.1°C), Platecarpus (Tb = 36.3°C), and Tylosaurus (Tb = 34.3°C), had elevated average body temperatures in relation to those of the fish (Tb = 28.3°C) and were closer to those of Ichthyornis (Tb = 38.6°C). The temperatures calculated for Enchodus compare well with previously reported temperature estimates for the Mooreville Chalk and the Tb of Ichthyornis compares well with temperatures that have been reported for modern seabirds, suggesting that this method provides accurate results. Finally, although there are small differences of body temperature among mosasaur genera, these are independent of size, and thus inferred body mass, suggesting that mosasaurs were not gigantotherms, but rather endotherms.

Ichthyosaurs Went Extinct During Cenomanian Cretaceous due to Inability to Adapt to Radical Climate Change

Ichthyosaurs - shark-like marine reptiles from the time of dinosaurs - were driven to extinction by intense climate change and their own failure to evolve quickly enough, according to new research by an international team of scientists.

The study provides an explanation for one of the longest-standing enigmas in palaeobiology: how and why ichthyosaurs died out. Unlike other marine reptile groups, ichthyosaurs disappeared tens of millions of years before the end-Cretaceous extinction (65 million years ago) that marked the end for dinosaurs and the beginning of the age of mammals.

The research is published in the journal Nature Communications.

First author Dr Valentin Fischer, of the University of Liège, Belgium, and the University of Oxford, UK, said: "We analysed the extinction of this crucial marine group thoroughly for the first time. We compared the diversity of ichthyosaurs with the geological record of global change, emphasising the dynamics of these datasets.

"Ichthyosaurs were actually well diversified during the last chapter of their reign, with several species, body shapes and ecological niches present. However, their evolution was much slower than earlier in their history. Additionally, they were seemingly negatively affected by the profound global changes going on during the Cretaceous, as their extinction rate correlates with environmental volatility."

Causes of extinctions - including the demise of the ichthyosaurs, or 'sea dragons' - have often remained elusive and conjectural, particularly when they cannot be linked to an obvious geological or geochemical event such as a large meteorite or massive volcanic eruption. Ichthyosaurs were regarded as undiversified for a prolonged period before their extinction, and their dying out has previously been linked to minor events including increased competition with other marine predators and a decline in their assumed principal source of food.

However, using a battery of cutting-edge techniques to quantify ancient biodiversity and its fluctuations, the team was able to reconstruct the evolution of the ichthyosaurs during the last 120 million years of their lifetime and assess the causes of their extinction. The researchers - comprising Belgian, British, French and Russian scientists - demonstrated that before their extinction, ichthyosaurs were in fact highly diverse, both in terms of body shape and ecological role.

A two-phase event then suppressed their ecological diversity and wiped out the group at the beginning of the Late Cretaceous period, about 100 million years ago. At that time, the Earth's poles were essentially ice-free, and sea levels were much higher than today. Analyses revealed that this two-phase extinction can be associated both with reduced evolutionary rates (a failure to evolve novel body plans for a prolonged period) and intense climate change (strong variations in sea surface temperatures and sea levels).

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paper link.

Kawanectes lafquenianum: a new Elasmosaurid Plesiosaur From Campanian/Maastrichtian Cretaceous Patagonia

A SMALL BODY SIZED NON-ARISTONECTINE ELASMOSAURID (SAUROPTERYGIA, PLESIOSAURIA) FROM THE LATE CRETACEOUS OF PATAGONIA WITH COMMENTS ON THE RELATIONSHIPS OF THE PATAGONIAN AND ANTARCTIC ELASMOSAURIDS

Author:

O'Gorman

Abstract:

The systematics of the Late Cretaceous non-aristonectine elasmosaurids from Argentinean Patagonia are poorly known as there is no valid species currently recognized. Here a new non-aristonectine elasmosaurid: Kawanectes lafquenianum nov. comb. from the late Campanian–early Maastrichtian Allen Formation is diagnosed. Kawanectes lafquenianum is a distinctively small-bodied sized non-aristonectine elasmosaurid characterized by caudal vertebrae with marked laterally projected parapophyses, presence of pelvic bar, high ratio (~1.2) between humerus/femur length and a large posterodistal projection of the humerus which bears a posterior accessory articular facet. A phylogenetic analysis recovered K. lafquenianum closely related with Morenosaurus stocki, Vegasaurus molyi and Aristonectinae, showing the relationships between the elasmosaurids from Patagonia, Western Antarctic, and the Pacific coast of the USA. Kawanectes lafquenianum is part of the fauna of the coeval Allen and La Colonia formations that also comprises indeterminate aristonectines and polycotylids . This relatively high diversity plesiosaur fauna includes the three main morphotypes (aristonectines, non-aristonectines elasmosaurids and polycotylids), which is remarkable since the depositational environments of the Allen have been inferred as marginal marine to non-marine environments.

Muiscasaurus catheti: A new Ophthalmosaurid Ichthyosaur From Barremian/Aptian Cretaceous Colombia

A new ophthalmosaurid ichthyosaur from the Early Cretaceous of Colombia

Authors:

Maxwell et al

Abstract:

Cretaceous ichthyosaurs were relatively diverse in temperate latitudes, but few species have been described from the palaeotropics. Here, we describe a new ophthalmosaurid ichthyosaur, Muiscasaurus catheti gen. et sp. nov., from the Barremian–Aptian aged Paja Formation of Colombia. This species is known only from a partial skull and differs from all other ichthyosaurs in the unusual configuration of the external narial opening, slender rostrum, narrow postorbital region, and gracile dentition. It is the second ichthyosaur described from the Paja Formation, suggesting moderate taxonomic and ecological ichthyosaur diversity in the region during the Early Cretaceous.

A new Ophthalmosaurid Ichthyosaur From Jurassic British Columbia

An Upper Jurassic ichthyosaur (Ichthyosauria: Ophthalmosauridae) from the Bowser Basin, British Columbia

Authors:

Sissons et al

Abstract:

Although the Jurassic was a period of high diversity in ichthyosaurs, only a small number of specimens have been recorded from Canada to date. We describe here a new occurrence of an ophthalmosaurid ichthyosaur from a shallow marine depositional environment within the Bowser Basin of northern British Columbia. Based on vertebral diameters and the size of the humerus, the ichthyosaur was relatively large compared to other contemporaneous forms, yet possessed teeth that were small for its body size. As well, the height to length ratio of the preserved vertebrae suggests it may have had a more elongate, less regionalized body shape. Although indeterminate at a generic level, the presence of Late Jurassic ichthyosaurs in nearshore waters of northwestern North America further demonstrates their cosmopolitan distribution.

Makhaira rossica: a new Pliososaur With Crocodile Like Teeth From Hauterivian Cretaceous Russua

Peculiar macrophagous adaptations in a new Cretaceous pliosaurid

Authors:

Fischer et al

Abstract:

During the Middle and Late Jurassic, pliosaurid plesiosaurs evolved gigantic body size and a series of craniodental adaptations that have been linked to the occupation of an apex predator niche. Cretaceous pliosaurids (i.e. Brachaucheninae) depart from this morphology, being slightly smaller and lacking the macrophagous adaptations seen in earlier forms. However, the fossil record of Early Cretaceous pliosaurids is poor, concealing the evolution and ecological diversity of the group. Here, we report a new pliosaurid from the Late Hauterivian (Early Cretaceous) of Russia. Phylogenetic analyses using reduced consensus methods recover it as the basalmost brachauchenine. This pliosaurid is smaller than other derived pliosaurids, has tooth alveoli clustered in pairs and possesses trihedral teeth with complex serrated carinae. Maximum-likelihood ancestral state reconstruction suggests early brachauchenines retained trihedral teeth from their ancestors, but modified this feature in a unique way, convergent with macrophagous archosaurs or sphenacodontoids. Our findings indicate that Early Cretaceous marine reptile teeth with serrated carinae cannot be unequivocally assigned to metriorhynchoid crocodylomorphs. Furthermore, they extend the known diversity of dental adaptations seen in Sauropterygia, the longest lived clade of marine tetrapods.

Phosphorosaurus ponpetelegans: a Halisaurine Mosasaur With Binocular Vision From Cretaceous Japan

A new halisaurine mosasaur (Squamata: Halisaurinae) from Japan: the first record in the western Pacific realm and the first documented insights into binocular vision in mosasaurs

Authors:

Konishi et al

Abstract:

A specimen of a halisaurine mosasaur is reported from Japan for the first time, closing the pre-existing biogeographical gap between the Middle East and the eastern Pacific. Phosphorosaurus ponpetelegans sp. nov., from the lowermost Maastrichtian of Hokkaido, has been assigned to the genus Phosphorosaurus for sharing the following suite of major cranial characters with P. ortliebi, the type species from Belgium: apex of posterodorsal triangular plateau on frontal reaching level of interorbital constriction; frontal lateral border forming a step-like junction between interorbital and preorbital segments of frontal; preorbital segment of frontal sloping anteroventrally; and stapedial meatus parallel-sided in latero-medial view. Potential autapomorphies that distinguish P. ponpetelegans from other members of Halisaurinae include: postorbitofrontal jugal process elongate and stalk-like, projecting laterally; this process distally bearing a ventrally facing depression for jugal articulation; and lateral surangular–articular suture angular rather than round. The long and laterally projecting jugal processes, when combined with a depressed as well as narrow snout, provide compelling evidence for well-developed binocular vision for the new mosasaur, with an estimated binocular field of view (BFoV) of 35°. This value is unusually high for non-ophidian squamates that typically exhibit a BFoV of 10—20°, and is higher than those of other measured mosasaur taxa by at least 5°. Among colubrid snakes, nocturnal species exhibit greater BFoV than diurnal ones in both arboreal and terrestrial taxa. Known also from the Maastrichtian of Hokkaido are fossils of lantern fish (myctophids) and 10-armed cephalopods (coleoids), both of which are typically bioluminescent today. It is hence proposed that the exceptionally large, forward-facing eyes of P. ponpetelegans may well have been a special adaptation for a nocturnal lifestyle, where they hunted small, bioluminescent prey at night while avoiding direct competition with larger, more piscine mosasaurine taxa such as Mosasaurus hobetsuensis that co-existed with P. ponpetelegans.

Dianmeisaurus gracilis: A new Small-sized Eosauropterygian From Anisian Triassic Luoping

A new small-sized eosauropterygian (Diapsida: Sauropterygia) from the Middle Triassic of Luoping, Yunnan, southwestern China

Authors:

Shang et al

Abstract:

A new eosauropterygian, Dianmeisaurus gracilis gen. et sp. nov. is described based on a nearly complete skeleton from the Member II of Guangling Formation (Anisian) of Luoping County, Yunnan Province. It is a small-sized (with a total length of less than 50 cm) sauropterygian with a slender body. This new species is similar superficially to two other smallsized eosauropterygians, Diandongosaurus Shang et al., 2011 and Dianopachysaurus Liu et al., 2011a, which were also collected from the same stratum of Luoping, in the body proportion, the skull with no contracted snout, and an oval orbit extremely larger than supratemporal fenestra. However, the new species is characterized by an extremely narrowed interorbital septum, the mandibular articulation at the level of occipital condyle, the big and stout anterolateral process of the clavicle, the proximal part of the ulna much wider than the distal end, and the presence of 41 presacral vertebrae. Furthermore, the new species differs from Diandongosaurus in having the preorbital region shorter than the postorbital region, the prefrontal with no contact of the postfrontal along the dorsal margin of the orbit, the short mandibular symphysis with the entrance of the splenial, and the premaxillary and anterior dentary teeth fang like but not king-sized. Additionally, the anterolateral process of the clavicle is very sharp and slender in Diandongosaurus. Compared with the Dianopachysaurus, the new species is different in having no pachyostosis of the caudal ribs, no more than three carpal ossifications, and the rounded astragalus. Our phylogenetic analyses suggest that Dianmeisaurus is probably the sister group of Diandongosaurus. The two genera, together with the Majiashanosaurus, Keichousaurus, and Dianopachysaurus are grouped in a monophyletic clade and phylogenetically more closely related to the Nothosauroidea than the European pachypleurosaurs (Dactylosaurus, Anarosaurus, Serpianosaurus, and Neusticosaurus). The coexist of three small-sized eosauropterygians indicates that sauropterygians were a highly diversified group of marine reptiles in the Luoping fauna, Yunnan Province during the early Middle Triassic.

Polycotylus latipinnis: a Redescription of Polycotylid Plesiosaur From Campanian Cretaceous South Dakota

Polycotylus latipinnis Cope (Plesiosauria, Polycotylidae), a nearly complete skeleton from the Niobrara Formation (Early Campanian) of southwestern South Dakota

Authors:

Schumacher et al

Abstract:

A nearly complete skeleton of Polycotylus latipinnis (SDSM 23020) from the upper Niobrara Formation (early Campanian) of South Dakota (U.S.A) greatly improves information for this formerly poorly known taxon. Specimens SDSM 23020 and YPM 1125 (paratype P. latipinnis) exhibit numerous postcranial characters that distinguish Polycotylus, in particular presacral vertebral count, nature of chevron facets, unique ilia, and highly derived paddles including five epipodial ossifications and increased hyperphalangy. Greater vertebral and phalangeal counts of Polycotylus are accompanied by exceptional foreshortening; thus, the relative body and limb proportions are likely similar to less derived polycotylids, with fewer, more elongate vertebrae and phalanges. The complete skull, derived among polycotylids, has short temporal fenestrae, elongate frontals, exceptionally slender parasphenoid with prominent cultriform process, and exceptionally long extensions of the angulars and splenials within the mandibular symphysis. Cladistic analysis indicates that Polycotylus nests firmly within derived Polycotylidae as a potential sister taxon to Dolichorhynchops osborni and Trinacromerum, despite a ‘primitive’ presacral vertebral count. Future improvements in available data, in particular better information regarding basal polycotylids, and refinement of character selection to nullify homoplasy could significantly alter the tree structure to show distinct subgroups within Polycotylidae. North American polycotylids with elongate temporal fenestrae, elongate podials, and relatively long vertebrae are confined to occurrences of late Cenomanian and earliest Turonian age, whereas polycotylids distinctly foreshortened in these respects are restricted to post-Turonian occurrences. Ilium morphology is highly variable among polycotylids and, in addition to taxonomic utility, may be in part attributable to sexual dimorphism.

Prolacertilians and Eosauropterygians From Early Triassic Donskaya Luka, Russia

New data on the herpetofauna of the Early Triassic Donskaya Luka locality, Volgograd Region

Authors:

Sennikov

Abstract:

New material of Early Triassic prolacertilians and eosauropterygians from the Donskaya Luka locality is described. New data on the morphology and functional morphology of these reptile groups are provided; their taxonomy, phylogeny, and lifestyle are discussed.

A Very Complete Triassic Plesiosaur Found in Germany

link (auf deutch/in german)

A Revised Phylogeny of Ichthyosaurs and Their Relatives

Phylogeny of the Ichthyopterygia incorporating recent discoveries from South China

Authors:

Ji et al

Abstract:

During the last decade, abundant ichthyopterygian material has been found from the Triassic of South China as well as the Upper Jurassic and Lower Cretaceous of Europe and South America, significantly expanding our knowledge of ichthyopterygian diversity through the Mesozoic. Previous phylogenetic hypotheses of the group no longer account for these extensive additions, necessitating a new phylogenetic framework for the entire Ichthyopterygia to enable evolutionary studies of the group. We present here a comprehensive phylogenetic hypothesis for Ichthyopterygia based on cladistic analysis of 163 characters coded for 59 ingroup and five outgroup taxa. The monophyly of Ichthyopterygia is strongly supported by a Bremer index value of 7. Five major groups of Ichthyopterygia during the Triassic, viz., Grippioidea, Cymbospondylidae, Mixosauridae, Shastasauridae, and Toretocnemidae, are well supported by Bremer index values between 3 and 5. Major clades that evolved in the Triassic, including Merriamosauria, Euichthyosauria, and Parvipelvia, are also robustly supported, whereas most post-Triassic clades are very weakly supported with a Bremer index value of 1, with a few exceptions, such as Thunnosauria and Ophthalmosauridae. The traditional Shastasauridae is expanded to comprise six genera but excludes Callawayia, which is more closely related to Parvipelvia than to Shastasauridae. ‘C.’ wolonggangensis is a shastasaurid but does not form a monophyletic clade with Callawayia neoscapularis or Guizhouichthyosaurus tangae as previously asserted. The new phylogenetic hypothesis is generally consistent with the stratigraphic occurrences of each taxon especially for the Triassic taxa.

Mortuneria: an Anarctic Filter Feed Maastrichtian Cretaceous Pleisosaur

If you’ve ever flipped through a book of prehistoric creatures or ambled through a major museum’s fossil halls, you’ve probably seen a plesiosaur.

These were the four-flippered marine reptiles that patrolled the seas for almost the entire Mesozoic era, some 250 to 66 million years ago. Some plesiosaurs were big-headed apex predators. Others had ludicrously long necks and snatched up fish and crustaceans with their little jaws.

Now, Marshall University paleontologist F. Robin O’Keefe has discovered that some of them filled their bellies in a way thought to be impossible for the aquatic reptiles: filter feeding.

The findings, presented last month at the annual Society of Vertebrate Paleontology meeting in Dallas, centered on a plesiosaur that has puzzled paleontologists for over 25 years. Named Mortuneria, this plesiosaur was found in the 66-million-year-old rock of Seymour Island, Antarctica.

Along with a closely related animal called Artistonectes found in Chile, Mortuneria was informally called one of “the hoopy jaws” for its large, hoop-shaped mouth that made it stand out from other known plesiosaurs, O’Keefe says.

Paleontologists Sankar Chatterjee and Bryan Small, who initially described Mortuneria in 1989, mooted the idea that the marine reptile’s odd jaw and needle-like teeth were adaptations for trapping small prey. So O’Keefe went back to re-describe the odd animal and seek out alternate feeding strategies.

“I look at it, and I was baffled”, O’Keefe says. But after weeks of hard work, he found that Mortuneria possessed an array of anatomical features that meant it must have been filter feeding. First of all, the teeth of Mortuneria don’t interlock like they do in other plesiosaurs.

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The Hydrodynamics of Plesiosaurs

Millions of years ago when the dinosaurs were walking around on the earth, there was a type of marine reptile called a plesiosaur that was swimming in the seas. Plesiosaurs were reptiles that had evolved to live in the ocean, and had four big flippers that they used to swim with. These flippers were similar to the flippers of a turtle or sea lion, but whereas these creatures only really use their front two for propulsion, plesiosaurs used all four.

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