![Fig, I. Geological m:lp of Seymour Island with plesiusaur fossilluealities (alkr Huher I ')XS and Macellari I ']X!!).](https://www.researchgate.net/profile/Sankar-Chatterjee/publication/249548928/figure/fig1/AS:669076519141376@1536531681128/Fig-I-Geological-mlp-of-Seymour-Island-with-plesiusaur-fossilluealities-alkr-Huher-I_Q320.jpg)
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New plesiosaurs from the Upper Cretaceous of Antarctica
Abstract and Figures
New plesiosaur remains from the Upper Cretaceous Lopez de Bertodano Formation (late Campanian-Maastrichtian) of Seymour Island, Antarctic Peninsula include Cryptoclididae and Elasmosauridae. The occurrence of Cryptoclididae is reported from the Antarctic region for the first time. The taxon represents a new genus and species, based on a skull and associated cervical vertebrae. The long, slender and delicate teeth may have formed a ‘trapping’ device that enabled cryptoclidids to feed on small fish and crustaceans that abound in the same deposits. The cryptoclidids had a restricted distribution, being known so far from the Middle and Late Jurassic of England, and the Late Cretaceous of Chile, Argentina, and Antarctica.
Other specimens, represented by several postcranial skeletons, are taxonomically indeterminate, but they share some features with other contemporary elasmosaurid genera such as Hydrotherosaurus, Morenosaurus, Thalassomedon , and Mauisaurus . Unlike the cryptoclidids, the elasmosaurids had a cosmopolitan distribution during the Jurassic and Cretaceous periods.
Trophic diversity within guilds of marine predators is examined in the Lopez de Bertodano palaeocommunities. Three predator guilds are recognized on the basis of tooth morphology and prey preference. The mosasaurs composed the ‘Cut guild’, and were the principal predators. The elasmosaurids constituted the ‘Pierce guild’, and the cryptoclidids formed the ‘Trap guild’. These marine reptiles exploited the various pelagic resources such as sharks, bony fish, soft cephalopods and crustaceans, and survived until the end of the Cretaceous. The plesiosaurs were excellent swimmers, and used their hyperphalangic paddles for subaqueous flight in the manner of modern sea lions.
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... Specifically, in the Pierce II Guild, plesiosauroids fall in an area of the morphospace defined by the shortest mandibular symphysis length, highest TI and highest MA values as well as the smallest jaw length in our dataset (figures 2, 5 and 6). This suggests that plesiosauroids adopted a unique foraging strategy [15,33,67], different from that of other taxa in the Pierce Guild (i.e. the 'trap guild' proposed by Chatterjee and Small [68]. This separation supports the original subdivision in Pierce I and Pierce II by Massare [9], a split that could not be confirmed by the dentition-only study by Foffa et al. [5]. ...
... fast-opening jaws, long mandibular symphysis, gracile jaws, small adductor musculature relative to mandible length). The distinction between plesiosauroids and other members of the Pierce Guild was observed based on qualitative data by Chatterjee and Small [68], who proposed the addition to the new category of 'Trap Guild'. ...
... Kimmerosaurus langhami might be an exception to this pattern, as this taxon could diverge from the traditional plesiosaur feeding style based on the unusual shape and a high number of strongly hooked teeth [40,69]. Similarities with Morturneria seymourensis-a Late Cretaceous elsamosaur-indicate that both taxa could be adapted for filter feeding [68]. In support of this hypothesis, this taxon has comparatively smaller muscle insertion areas compared with its closest relatives (figure 8; electronic supplementary material, appendix S1). ...
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.
... However, the specimens diagnostic at genus or species level are restricted to the aristonectines from the upper Maastrichtian, such as Morturneria seymourensis and one specimen referred to cf. Aristonectes, and to the lower Maastrichtian non-aristonectine Vegasaurus molyi (Chatterjee & Small, 1989;O'Gorman et al., 2015;O'Gorman, Santillana, et al., 2019;O'Keefe et al., 2017). With the remarkable exception of the holotype of Morturneria seymourensis, the specimen MLP 15-I-7-6 (MLP Museo de La Plata, La Plata; Argentina), and an indeterminate non-aristonectine elasmosaurid from the lower Maastrichtian levels of the Cape Lamb Member of the Snow Hill Island Formation (O'Gorman et al., 2018), Antarctic elasmosaurids lack any well-preserved cranial material (Chatterjee & Small, 1989;Gasparini et al., 2003;Martin et al., 2007;O'Gorman et al., 2012;O'Gorman, Santillana, et al., 2019;Otero et al., 2014). ...
... Aristonectes, and to the lower Maastrichtian non-aristonectine Vegasaurus molyi (Chatterjee & Small, 1989;O'Gorman et al., 2015;O'Gorman, Santillana, et al., 2019;O'Keefe et al., 2017). With the remarkable exception of the holotype of Morturneria seymourensis, the specimen MLP 15-I-7-6 (MLP Museo de La Plata, La Plata; Argentina), and an indeterminate non-aristonectine elasmosaurid from the lower Maastrichtian levels of the Cape Lamb Member of the Snow Hill Island Formation (O'Gorman et al., 2018), Antarctic elasmosaurids lack any well-preserved cranial material (Chatterjee & Small, 1989;Gasparini et al., 2003;Martin et al., 2007;O'Gorman et al., 2012;O'Gorman, Santillana, et al., 2019;Otero et al., 2014). As cranial material is the main source of characters (about 50%; Benson & Druckenmiller, 2014;O'Gorman, 2019) used in the diagnosis of species and genera, the scarcity of cranial material partially explains the difficulties related to the systematics of Antarctic elasmosaurids. ...
... 11A, C, E, 12D, F). The ventral plate is present, although less developed and anteriorly inclined in Nakonanectes bradti (Serratos et al., 2017), while the basioccipital shows only a small step on the ventral surface in Morturneria seymourensis (Chatterjee & Small) Chatterjee & Creisler, 1994(Chatterjee & Small, 1989 Fig. 12G, H). A similar condition is observed in MLP 15-I-7-6, an indeterminate juvenile non-aristonectine elasmosaurid from the lower Maastrichtian of Vega Island, Antarctica (O'Gorman et al., 2018). ...
... In plesiosaurians, different interpretations have been suggested for the identification and passages of the glossopharyngeal, vagus, and possible accessory nerves. Carpenter (1997) labelled two distinct canals on the endocast of Libonectes morgani (Fig. 3.7b) Chatterjee and Small 1989;Carpenter 1997) foramina that correspond to the roots of hypoglossal nerves. Laterally, all these canals may merge with the foramen that also accommodates the glossopharyngeal and vagus nerves (e.g. ...
... Druckenmiller 2002Evans 2012) other distinct foramina. Although the branching pattern of the hypoglossal nerves might be of phylogenetic and taxonomic significance (Zverkov et al. 2017), the presence of a possible rightleft asymmetry (Chatterjee and Small 1989), as well as potential misidentification of vascular or nutritive foramina (e.g. Evans 2012) may challenge the recognition of the hypoglossal foramina. ...
Most meso- and megapredatory niches across Mesozoic marine ecosystems were gradually occupied by the secondarily aquatic Ichthyopterygia and Sauropterygia. Although their presumed Early Triassic origins remain obscured, the subsequent radiation and diversification of these diapsid superorders is reasonably well documented in the fossil record. In the first quarter of the twentieth century, the Triassic sauropterygian genera Nothosaurus and Placodus were among the first taxa for which the cranial endocast was extracted and described. The advent of computed tomography, circa 50 years after these pivotal paleoneurological investigations, has led to its adoption as the tool of choice for the non-destructive assessment of neurosensory adaptations in extinct vertebrates. Despite the increasing availability of paleoneurological data on extinct diapsids, Ichthyopterygia and Sauropterygia have received relatively modest, albeit growing, attention since. Here we review paleoneurological insights gleaned from these fossils to date and identify endocranial and neurosensory modifications associated with increasingly pelagic lifestyles and ecological specializations. Nevertheless, a broader ichthyopterygian and sauropterygian sample will be required to facilitate high-resolution taxon-wide comparisons and discern between endocranial changes accompanying progressive adaptation to aquatic niches and conservative features informing on phylogenetic identity. Systematic evaluation will reveal the neurosensory developments that facilitated these Mesozoic ecological success stories in aquatic environments.
... Several species of pinnipeds have teeth modified into filter-feeding, specifically with elaborate cusps of postcanines on both the upper and lower jaw. This modification is well-seen, especially in the crabeater seal Carinophaga lobodon (Chatterjee & Small, 1989;Bengtson, 2002;Adam, 2005). ...
Background
Coprolites, i.e ., fossilized faeces, are an important source of knowledge on the diet and food processing mechanisms in the fossil record. Direct and indirect evidences for the dietary preferences of extinct sharks are rare in the fossil record. The first coprolite attributable to Ptychodus containing prey remains from the European Cretaceous is documented here.
Methods
A coprolite from the Late Cretaceous of Opole (southern Poland) was scanned using micro-computed tomography to show the arrangement of the inclusions. In addition, the cross-section was examined under the SEM/EDS to analyse the microstructure and chemical composition of the inclusions.
Results
Brachiopod shell fragments and foraminiferan shells are recognized and identified among the variously shaped inclusions detected through the performed analysis.
Conclusions
The extinct shell-crushing shark Ptychodus has been identified as the likely producer of the examined coprolite. The presence of brachiopod shell fragments indicates that at least some species of this durophagous predatory shark may have preyed on small benthic elements on the sea bottom.
... 2013), actinopterygians(Cione et al. 2018), mosasaurids(Martin 2006, Fern andez & Gasparini 2012, and elasmosaurid plesiosaurians(Chatterjee & Small 1989, O'Gorman & Coria 2017, O'Gorman et al. 2018, 2021, O'Keefe et al. 2017, O'Gorman et al. 2019. Continental vertebrates are represented by hadrosaurid, ankylosaurid(Rich et al. 1999, Case et al. 2000, Lamanna et al. 2019, and avian theropod dinosaurs(Chatterjee 2000, Clarke et al. 2005, Hospitaleche & Gelfo 2015.Materials and methodsInstitutional abbreviationsDM, Museum of New Zealand Te Papa Tongarewa, Wellington, New Zealand. ...
... The absence of a similar structure on the dentary probably precludes a direct involvement in food procurement and processing, unlike the situation in the several marine and terrestrial taxa bearing procumbent teeth that probably permit easier catch of small prey items (e.g. Chatterjee & Small, 1989). '[F]orwardly oriented' mesial dentary teeth have been described in another pliosaurid, Pliosaurus patagonicus (Gasparini & O'Gorman, 2014: 276). ...
Pliosaurid plesiosaurians are iconic marine reptiles that regulated marine trophic chains from the Middle Jurassic to the early Late Cretaceous. However, their evolution during the Cretaceous remains poorly documented. Recent discoveries from the Hauterivian–Aptian interval suggest that the radiation of brachaucheniine pliosaurids produced a wide disparity of forms following the Pliosaurus-dominated assemblages of the Late Jurassic. Among the most bizarre of these early brachaucheniines is Luskhan itilensis, from the Hauterivian of Russia. We describe the osteology of this tusked, longirostrine pliosaurid and discuss its possible behaviour by drawing comparisons with other marine amniotes possessing forward-pointing teeth. We take this opportunity to make extensive anatomical comparisons among Cretaceous pliosaurids, including previously overlooked cranial features. Bayesian inference of phylogenetic relationships of plesiosaurians reveals that the internal branches in Late Jurassic–Late Cretaceous pliosaurids have generally low rates of morphological evolution, indicating that the recently described Early Cretaceous pliosaurids have effectively bisected the long branch leading to the ‘classical’ brachaucheniines of the middle Cretaceous (Brachauchenius, Kronosaurus and Megacephalosaurus). Pliosaurids exhibit low evolutionary rates and a dwindling disparity before their extinction, mirroring the events seen, roughly at the same time, for ichthyosaurians.
... The record of polycotylids from Antarctica is restricted to two indeterminate records from lower levels of the marine Santa Marta Formation (Coniacian-Santonian), described by (Kellner et al. 2011;Novas et al. 2015). The overlying Campanian-Mastrichtian marine formations of Antarctic Peninsula (Snow Hill Island and López de Bertodano formations) of Antarctica has a rich and frequent record of elasmosaurids (Gasparini et al. 1984;O'Gorman 2012;Otero et al. 2014a;O'Gorman et al. 2018) even including endemic taxa (Chatterjee & Small 1989;O'Keefe et al. 2017); however, despite thirty years of continuous field work by the Argentinean Antarctic Institute, post-Coniacian Antarctic polycotylids remain unknown to date. ...
Polycotylidae Cope, 1869 is a clade of short-necked plesiosaurians that achieved a cosmopolitan distribution by the Late Cretaceous. Here, the material previously referred to Polycotylidae/Pliosauridae from the Upper Cretaceous of New Zealand is reviewed, concluding that only 2.4% and 7.7% respectively of the total plesiosaurians specimens recovered in these formations (late Campanian-early Maastrichtian Tahora Formation and Campanian-Maastrichtian Conway Formation) belong to Polycotylidae. This proportion is similar to that recorded in upper Campanian-Maastrichtian levels of the Allen, Los Alamitos and La Colonia formations, northern Patagonia (Argentina) and southernmost Chile, but contrasts with the coeval absence of polycotylids in Campanian-Santonian levels of Antarctica and central Chile. These new results improve our knowledge about the representation of Weddellian polycotylids and underline the relative scarcity of Campanian-Maastrichtian records in the Weddellian Province.
This contribution reassesses the first historical specimen from the Upper Cretaceous of Chile, referred to the genus Aristonectes in the late sixties. A detailed description allows an improved understanding of those elements comprising the mandibular ramus. These are found to be coincident with those of the holotype of Aristonectes quiriquinensis, with only minor differences in size, which are explainable due to different ontogenetic stages of the specimens. Therefore, the re-studied material is now referred to as A. quiriquinensis, being the second available skull material of the species. The new description recognizes that the available elements belong to the right side of the skull. Moreover, the material also preserves part of the right orbit, a portion previously unknown in the available skulls of Aristonectes spp. The assessed orbit outline reveals the presence of the prefrontal, forming the anteroventral margin of the orbit. A similar topology is observed in other aristonectines such as Morturneria seymourensis and Kaiwhekea katiki, but also in the non-aristonectine austral elasmosaurid Tuarangisaurus keyesi. The orbit outline of Aristonectes quiriquinensis is here disclosed for the first time, showing this to be remarkably similar to that of Kaiwhekea, but probably differs from that of Aristonectes parvidens, at least based in their available skull elements. This suggests that A. quiriquinensis could be a more basal taxon with respect to A. parvidens.
A worldwide revision of the Cretaceous record of Neornithes (crown birds) revealed that unambiguous neornithine taxa are extremely scarce, with only a few showing diagnostic features to be confidently assigned to that group. Here we report two new neornithine specimens from Vega Island (López de Bertodano Formation). The first is a synsacrum (MN 7832-V) that shows a complex pattern of transversal diverticula intercepting the canalis synsacri, as in extant neornithines. Micro-CT scanning revealed a camerate pattern of trabeculae typical of neornithines. It further shows the oldest occurrence of lumbosacral canals in Neornithes, which are related to a balance sensing system acting in the control of walking and perching. The second specimen (MN 7833-V) is a distal portion of a tarsometatarsus sharing with Vegavis iaai a straight apical border of the crista plantaris lateralis. Osteohistologically the tarsometatarsus shows a thick and highly vascularized cortex that lacks any growth marks, resembling Polarornis gregorii. The cortex is osteosclerotic as in other extinct and extant diving neornithines. These new specimens increase the occurrences of the Cretaceous avian material recovered from the Upper Cretaceous strata of the James Ross Sub-Basin, suggesting that a Vegaviidae-dominated avian assemblage was present in the Antarctic Peninsula during the upper Maastrichtian.
The initial radiation of Eosauropterygia during the Triassic biotic recovery represents a key event in the dominance of reptiles secondarily adapted to marine environments. Recent studies on Mesozoic marine reptile disparity highlighted that eosauropterygians had their greatest morphological diversity during the Middle Triassic, with the co-occurrence of Pachypleurosauroidea, Nothosauroidea and Pistosauroidea, mostly along the margins of the Tethys Ocean. However, these previous studies quantitatively analysed the disparity of Eosauropterygia as a whole without focussing on Triassic taxa, thus limiting our understanding of their diversification and morphospace occupation during the Middle Triassic. Our multivariate morphometric analyses highlight a clearly distinct colonization of the ecomorphospace by the three clades, with no evidence of whole-body convergent evolution with the exception of the peculiar pistosauroid Wangosaurus brevirostris , which appears phenotypically much more similar to nothosauroids. This global pattern is mostly driven by craniodental differences and inferred feeding specializations. We also reveal noticeable regional differences among nothosauroids and pachypleurosauroids of which the latter likely experienced a remarkable diversification in the eastern Tethys during the Pelsonian. Our results demonstrate that the high phenotypic plasticity characterizing the evolution of the pelagic plesiosaurians was already present in their Triassic ancestors, casting eosauropterygians as particularly adaptable animals.
Collection of decapod crustaceans from fifteen localities in Cretaceous and Eocene rocks on Seymour Island, Antarctic Peninsula, has documented at least nine species-level taxa. The Campanian Lopez de Bertodano Formation encloses numerous specimens of Hoploparia stokesi as well as remains of Enoploclytia? and Linuparus n. sp. The Eocene La Meseta Formation contains a rich decapod assemblage dominated by Lyreidus antarcticus, but the unit also yields Chasmocarcinus seymourensis, and undescribed species in the Dromioidea, Calappidae, and Portunidae. Calliananassa sp. also occurs in the la Meseta Formation. With the exception of the previously named species, the specimens document the first records of these taxa on Seymour Island and many represent first records in Antarctica. -from Current Antarctic Literature
Fossil reptile material found during 1983-84 in the sandstone of the late Cretaceous Lopez de Bertodano Formation at Seymour I. included partial skeletons of plesiosaurs and mosasaurids. At this stage, the identification of taxa is tentative and finer diagnosis must wait until the preparation of the material is completed. Their record on Seymour I. indicates that these large marine animals co-existed in the late Cretaceous seas as far south as the coast off the Antarctic Peninsula and must have been able to traverse great areas of oceanic waters when the temperature was more equable. - from Current Antarctic Literature
