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Rostrum and frontal region of the holotype of Thililua longicollis (MHNGr.PA.11710) from the middle Turonian of Morocco. (a) Dorsal view and (b) osteological interpretation of (a).
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Polycotylidae is a clade of plesiosaurians that appeared during the Early Cretaceous and became speciose and abundant early in the Late Cretaceous. However, this radiation is poorly understood. Thililua longicollis from the Middle Turonian of Morocco is an enigmatic taxon possessing an atypically long neck and, as originally reported, a series of u...
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... Members of the family Elasmosauridae were still widespread and diverse during the latest Maastrichtian, as exemplified by Zarafasaura from phosphatic strata of Morocco (Lomax & Wahl, 2013;Vincent et al., 2013), as well as by material from Chile (Otero et al., 2014), Argentina , Antarctica (O'Gorman & Coria, 2016) and Arctic regions of Eurasia (Zverkov et al., 2023) and North-America (Russell, 1967). Until recently, only two polycotylid clades appeared to have ranged into the early Maastrichtian, namely Occultonectia and Polycotylinae (Mulder et al., 2000;Sato, 2005;O'Gorman & Gasparini, 2013;Fischer et al., 2018). Recently, a new polycotylid with an elongated snout and remarkably long neck from the lower Maastrichtian of the United States has been added to the latest Cretaceous record of this family (Persons et al., 2022), while Clark et al. (2024) additionally introduced a new clade of derived polycotylids that ranged into the Maastrichtian, the Dolichorhynchia. ...
... Recently, a new polycotylid with an elongated snout and remarkably long neck from the lower Maastrichtian of the United States has been added to the latest Cretaceous record of this family (Persons et al., 2022), while Clark et al. (2024) additionally introduced a new clade of derived polycotylids that ranged into the Maastrichtian, the Dolichorhynchia. Representatives of the family Polycotylidae Williston, 1908 in general had short, stout necks and an elongated rostrum (Druckenmiller & Russell, 2008;Frey et al., 2017;Fischer et al., 2018). Similar to polycotylids, elasmosaurids possessed numerous pointy teeth, but had extremely long necks and a short rostrum (Everhart, 2006;Kubo et al., 2012;Brum et al., 2022). ...
The first isolated and well-preserved phalanx (autopodial element) of a generically and specifically indeterminate (probably xenopsarian) plesiosaur from the Maastrichtian type area (south-east Netherlands) is described and illustrated. Morphological features of this bone, such as the articular subchondral surfaces, allow it to be distinguished from phalanges of co-occurring mosasaurs (Mosasauridae, Squamata) and could imply rapid growth in plesiosaurs, similar to that observed in extant leatherback turtles. The large size of the phalanx indicates that it originates either from a large juvenile or from a paedomorphic individual. The paucity of plesiosaur remains in biocalcarenites of late Maastrichtian age in the Maastrichtian type area could be explained by the shallow settings, in which these strata were deposited, which may not have offered suitable ecological resources conducive to abundant plesiosaur inhabitation. Presumably, the lack of steep continental slopes in the type Maastrichtian, at which oceanic upwelling of cold, nutrient-rich water supported a higher prey density for pelagic predators such as plesiosaurs, may have inhibited plesiosaur occupation. Rather, decomposing floating carcasses may have been the source of dissociated elements of plesiosaurs in this area, such as isolated teeth, vertebrae and the autopodial element described here.
... Polycotylids are a remarkable clade of Cretaceous plesiosaurians, characterized by a proportionally short neck, comprising 19e32 vertebrae, elongated snout, extensive plates of girdle elements and large, stiff flippers (e.g. Carpenter, 1996;Fischer et al., 2018;Persons et al., 2022). At present 13e18 genera and 19 polycotylid species (excluding taxa described from isolated and fragmentary elements) are recognized as valid (e.g. ...
... At present 13e18 genera and 19 polycotylid species (excluding taxa described from isolated and fragmentary elements) are recognized as valid (e.g. Fischer et al., 2018;Clark et al., 2024). Polycotylids were widespread and occurred on both low and high latitudes of all continents (Russell, 1967;Novas et al., 2015;Zverkov et al., 2023). ...
... Cope, 1869b; e.g. Carpenter, 1996;Sato and Storrs, 2000;Druckenmiller, 2002;Bardet et al., 2003;Buchy et al., 2005;Schmeisser McKean, 2012;O'Gorman and Gasparini, 2013;Novas et al., 2015;Fischer et al., 2018;Morgan and O'Keefe, 2019;O'Gorman, 2022;O'Gorman and Otero, 2023). Surprisingly, no attempt to clarify this mismatch has previously been undertaken. ...
Polycotylids are among the most common plesiosaurians of the Late Cretaceous, however, in Eurasia their findings are rare and fragmentary. In 2016, a partial polycotylid skeleton from the Upper Cretaceous of the Izhberda quarry in the Southern Urals region was described by Efimov et al. as a new species, Polycotylus sopozkoi. Here we revise this holotype specimen and show that many characters initially proposed to distinguish the species are the result of misinterpretations. However, P. sopozkoi is indeed referable to Polycotylus and is highly similar to its type species, P. latipinnis. Although only one distinctive trait of the species noted by Efimov et al., the protruding basioccipital tubera with deep carotid canals on their anterodorsal surface, is confirmed here, new observations revealed additional features that allow us to substantiate the validity of P. sopozkoi. The presence of Polycotylus in the Upper Cretaceous of North America and Eastern Europe highlights a wide distribution of some plesiosaurian genera and suggests caution in assumptions of ‘endemic’ plesiosaurian taxa in particular regions of the world.
... ; to contain Pliosauridae, Rhomaleosauridae and Polycotylidae, and Plesiosauroidea used to contain Plesiosauridae, Elasmosauridae and Cryptoclididae [210,38,211]. This taxonomic system was affected by body proportions, which have been revealed to be volatile among different clades (e.g., shortening of the neck evolved independently for multiple times [212,213]). Benson and Drunkenmiller [20] constructed a large character matrix containing 270 morphological characters and 80 operational taxonomic units. ...
... Pliosauridae has been revealed to form a monophyletic clade with Plesiosauroidea, known as Neoplesiosauria [22]. Polycotylidae is a group within Plesiosauroidea [213]. On the other hand, there exists discrepancy in topologies inside each clade among the phylogenies from recent years, due to the incompleteness of fossil materials and the usage of incompatible matrices. ...
... The phylogeny and taxonomy of Polycotylidae has been revised very recently by Clark et al [176], and I follow their taxonomic system despite the unstable topologies inside this clade discovered in previous studies [324,213,325,326]. The earliest polycotylids are known from Aptian of Australia [327]. ...
Body size is the key to understanding many biological properties. Sizes of extinct animals are usually estimated from body reconstructions since their masses can not be weighed directly. Plesiosaurs were Mesozoic marine reptiles that were diverse in both body plan and size. Attempts to estimate body masses of plesiosaurs were rare in the past two centuries, possibly due to lack of knowledge about their postcranial anatomy and body shapes in life. The burst of plesiosaur studies in the past two decades has greatly expanded our cognition of their physiology, taxonomy, potential behavior and even soft body outlines. Here I present a comprehensive review of relevant knowledge, and propose a uniform set of methodology for rigorous body reconstruction of plesiosaurs. Twenty-two plesiosaur models were constructed under these criteria, and they were subsequently used as samples to find proxies for body mass. It is revealed that multiple skeletal elements are good indicators of plesiosaur size. This study offers scaling equations for size estimation, enabling quick acquisition of body mass information from fragmented fossils. A summary of body size evolution of different plesiosaur clades is also provided.
... However, the transition from "archaic", Early Jurassic, to "derived", Middle Jurassic and younger, plesiosauroid communities has been poorly understood because of the scarcity of plesiosaur fossil record from the Lower/Middle Jurassic boundary interval (see, e.g., Fischer et al., 2021;Sachs et al., 2022: Supplementary Table S2). From the phylogenetic perspective, only a single taxon [Plesiopterys wildi from the lower Toarcian Posidonia Shale of Germany (O'Keefe, 2004)] has been reconstructed at this "transitional" position "between" microcleidids and cryptoclidians (e.g., Benson et al., 2012;Benson and Druckenmiller, 2014;Fischer et al., 2018;Madzia and Cau, 2020;Roberts et al., 2020). However, that taxon is based on an early juvenile individual that is additionally partly reconstructed and in a need of redescription. ...
... Only Plesiopterys wildi has previously been inferred at that position (e.g., Benson et al., 2012;Benson and Druckenmiller, 2014;Fischer et al., 2018;Madzia and Cau, 2020;Roberts et al., 2020). However, these results are doubtful. ...
Plesiosaurs are Mesozoic reptiles fully adapted to an aquatic lifestyle. Throughout their evolutionary history exceeding 140 million years plesiosaurs dispersed globally, achieved substantial diversity, occupied a variety of ecological niches, and experienced multiple faunal turnovers. Of those, the Early/Middle Jurassic transition event (∼175–171 Mya) has recently became of increased interest because it apparently profoundly affected all three major lineages of plesiosaurs. Once dominant Rhomaleosauridae started to vanish, while Pliosauridae and Plesiosauroidea diversified and gave rise to several clades that flourished for tens of millions of years. Here, we report exquisite, three-dimensionally preserved skeletons of a new plesiosaur from the Lower Jurassic of Germany. Franconiasaurus brevispinus gen. et sp. nov. lived during the late Toarcian (∼175 Mya), near the onset of the Early–Middle Jurassic turnover. Franconiasaurus displays an intriguing mixture of features, combining characters almost uniformly distributed among early plesiosaurs with those typically observed in later-diverging members of the clade. Phylogenetic analyses firmly place Franconiasaurus as the sister taxon to Cryptoclidia, bridging an evolutionary gap between early plesiosauroids, such as Plesiosaurus-like forms and microcleidids, and later-diverging representatives of the clade, such as cryptoclidids, leptocleidians, and elasmosaurids.
... To determine the phylogenetic position of MPEF-PV 5232 a phylogenetic analysis was performed. The data set is based on those of Benson and Drukenmiller (2014) and Serratos et al. (2017), modified by O'Gorman (2019) and O'Gorman et al. (2021) with the addition of the polycotylids from the data set of Fischer et al. (2018) and three characters and scoring of Morgan and O'Keefe (2019) dfor details see O'Gorman (2022). A few modifications on scorings and additional four characters were included and described in Supplementary Material 1. ...
A new elasmosaurid, Chubutinectes carmeloi gen. et sp. nov., from the Chubut Province, Argentina, is described. The holotype and only specimen of this species (MPEF-PV 5232) was collected from the La Colonia Formation. Chubutinectes carmeloi gen. et sp. nov. is among the few upper Maastrichtian elasmosaurids from the Southern Hemisphere whose postcranial anatomy is well known. It can be distinguished from other elasmosaurids by the following combination of characters: middle cervical centra longer than high with lateral keel and bilobate articular faces; pectoral and anterior dorsal centra with bilobate articular faces; coracoids with closed cordiform fenestra and long anterior coracoids process; high ratio coracoids/scapular length; ilium with angled shaft; pubis with small lateral cornua; humerus with posterior expansion ending in accessory facet and epipodial facets of humerus almost aligned; accessory ossification between tibia and tibial, and radius and radial. Preliminary phylogenetic analysis recovered Chubutinectes carmeloi gen. et sp. nov. within the Weddellonectia clade, including the Late Cretaceous Wedellian aristonectine elasmosaurids. The study of the associated microfossiliferous assemblages (micro- and nanofossils) indicates a marine inner neritic paleoenvironment, with restricted circulation and warm waters. The presence of Micula prinsii and Micula murus at this latitude indicates a latest Maastrichtian age, upper part of the UC20d sub-biozone and younger than ~67,3 Ma.
... Before running the analysis, we set the maximum number of trees to 800,000 through the 'hold 800000;' command. Plesiosaur phylogenetic studies usually set the maximum number of trees to up to 200,000 (e.g., Páramo-Fonseca et al., 2018;Fischer et al., 2018Fischer et al., , 2020Madzia et al., 2019;Roberts et al., 2020;Marx et al., 2021;Sachs et al., 2021), which is generally considered to be a representative sample of the most parsimonious trees (MPTs); though, higher numbers have been used as well (Puértolas-Pascual et al., 2021). Still, none of the recently published phylogenetic assessments of Plesiosauria conducted through unweighted parsimony analyses succeeded to find a definitive number of MPTs. ...
... The phylogenetic analysis reconstructed a poorly resolved strict consensus tree (Supplemental Data 1, Fig. S1) that shows extensive polytomies near the base of Plesiosauria. The majority rule tree (Supplemental Data, Fig. S2), however, shows tree topology that is broadly congruent with currently inferred plesiosaur phylogenetic relationships (see e.g., Fischer et al., 2018;Páramo Fonseca et al., 2018;Madzia and Cau, 2020;Roberts et al., 2020;Marx et al., 2021;Puértolas-Pascual et al., 2021;Sachs et al., 2021). Our analysis places the Trematospondylus operational taxonomic unit (OTU) among Atychodracon-Archaeonectrus-Eurycleidus-grade rhomaleosaurids (Fig. 3), though due to the highly incomplete nature of the material, such placement needs to be treated with caution. ...
Described in 1858, Trematospondylus macrocephalus is one of the earliest established plesiosaur taxa. However, despite being historically significant, the taxon disappeared from the literature shortly after its initial description and has not been mentioned for over a century. Thus, it has never been properly assessed. The holotype comprises seven vertebrae, including a supposed sacral vertebra and caudal vertebrae. The specimens were collected from the Lochen mountain massif near Balingen in southwestern Germany and derive from the Dentalienton Formation. As such, they are most likely early Bathonian (Middle Jurassic) in age. Here, we provide a thorough redescription of the material, illustrate it, and assess its phylogenetic affinities through a parsimony analysis. Our results show that T. macrocephalus shares characters with members of the Rhomaleosauridae, including, for example, the length-height ratio of the caudal centra as well as the placement of caudal ribs and hemapophyseal facets. Rhomaleosaurid affinities of the material are likewise supported by our phylogenetic analysis. Comparisons further indicate that the taxon belonged to large-bodied members of the clade, with a body length similar to that of Rhomaleosaurus. Even though the material does not enable Trematospondylus to be properly diagnosed, thus making it a nomen dubium, it still adds to the rare Middle Jurassic record of rhomaleosaurid plesiosaurs. At the same time, it enhances our knowledge of the plesiosaur taxic diversity during the pre-Callovian Middle Jurassic, which has been very limited.
... Polycotylidae Cope, 1869 is a clade of short-necked plesiosaurs whose range extends from the Aptian to the K/Pg mass extinction (Kear 2003(Kear , 2005(Kear , 2006Bardet et al. 2003;Sato 2005;Buchy et al. 2005;O'Gorman & Gasparini 2013;Fischer et al. 2018). Polycotylids show a peak of diversity during the Albian-Turonian, achieving a worldwide distribution, including Antarctica (Carpenter 1996;Sato & Storrs 2000;Bardet et al. 2003;Kear 2005;Buchy et al. 2005;Novas et al. 2015;Fischer et al. 2018). ...
... Polycotylidae Cope, 1869 is a clade of short-necked plesiosaurs whose range extends from the Aptian to the K/Pg mass extinction (Kear 2003(Kear , 2005(Kear , 2006Bardet et al. 2003;Sato 2005;Buchy et al. 2005;O'Gorman & Gasparini 2013;Fischer et al. 2018). Polycotylids show a peak of diversity during the Albian-Turonian, achieving a worldwide distribution, including Antarctica (Carpenter 1996;Sato & Storrs 2000;Bardet et al. 2003;Kear 2005;Buchy et al. 2005;Novas et al. 2015;Fischer et al. 2018). The Weddellian (i.e., New Zealand, Western Antarctica and southern South America) polycotylid record is markedly scarce. ...
... The presence of a short medial anterior process in such a large (likely adult) specimen suggests the lack of a girdle bar (in this reinterpretation, a pelvic bar). In addition, typical features present in polycotylid coracoids, such as the perforations on the symphyseal margin (Sato 2005;Albright et al. 2007;Schmeisser-McKean et al. 2012), although absent in Plesiopleurodon wellesi Carpenter, 1996and Mauriciosaurus fernandezi Frey, Mulder, Stinnesbeck, Rivera-Sylva, Padilla-Gutiérrez & González-González, 2017(Frey et al. 2017Fischer et al. 2018), are not present. Therefore, the specimen CD 457 is considered a plesiosaur pubis. ...
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.
... The apparent temporal discontinuity of the ecological adaptation of a narrow snout with procumbent front teeth on premaxilla among brachauchenines could be due to a collection bias, but also to ecological changes. It would not be unreasonable to suggest that the polycotylid plesiosaurs, having elongated snouts, relatively isodont dentition, and frequent teeth with carinae , which begin their history in the Aptian-Albian (Druckenmiller, 2002;Kear, 2003) and become diverse during the late Cretaceous (Druckenmiller and Russel, 2009;Fischer et al., 2018;Sachs et al., 2020), could have occupied the ecological niche of the Early Cretaceous long-snouted brachauchenines. consensus tree, with Bremer support indicated in some nodes. ...
A recently prepared fragment of the anterior end of a snout comprising occluded upper and lower jaws of a juvenile individual of Stenorhynchosaurus munozi Páramo-Fonseca et al., 2016 (Plesiosauria, Pliosauridae) is described herein. The specimen was found in the 1990s at Sutamarchán (Boyacá, Colombia), in Barremian beds of the Arcillolitas abigarradas Member of the Paja Formation. Its description provides hitherto unknown valuable morphological information on the species: dorsal anterior extension of the vomer, five premaxillary teeth (not four as was previously suggested), and anteriorly directed orientation of the first premaxillary alveolus (procumbent). New observations made on previously studied material corroborated the existence of procumbent anterior premaxillary teeth in the species. The presence of this trait highlights the close relationship of S. munozi with other early-diverging brachauchenines from the Lower Cretaceous of Russia.
... Geographic (outcrops numbering) and stratigraphic (members and beds numbering) data follow Zakharov et al. (1986Zakharov et al. ( , 1989a conservatively, to a leptocleidian) plesiosaurian (e.g. Carpenter, 1996;Fischer et al., 2018), rather than to elasmosaurids, which have flattened labial surface giving the crown oval to D-shaped cross-section (e.g. Welles, 1943;Druckenmiller and Russell, 2008). ...
... It differs from ZIN PH 1/285 in lacking ridges on its labial surface (Fig. 4I, L), however, the ridges on its mesial, distal and lingual surfaces (16 in total count) are widely spaced and coarse similarly to ZIN PH 1/285, and the cross-section of the crown is subcircular (Fig. 4L), indicating, as in the case of the former specimen, that this is rather a polycotylid, than elasmosaurid plesiosaurian. Among polycotylids, smooth labial surface occurs in Dolichorhynchops spp., Thililua longicollis and Eopolycotylus rankini (Williston, 1903;O'Keefe, 2004;Albright et al., 2007;Schmeisser McKean, 2012;Fischer et al., 2018), whereas other polycotylid taxa (e.g. Polycotylus, Trinacromerumi) have ridges distributed around the entire circumference (e.g. ...
Here we describe the first findings of reptile remains in the Upper Cretaceous marine strata of Siberia, which represent the northernmost occurrences of plesiosaurians, ?mosasaurids and turtles in the Cretaceous of Eurasia (66-72° N palaeolatitudes). The specimens come from the upper Cenomanian, Turonian and Coniacian of the Pyasina River basin, Santonian and Maastrichtian of the Tanama River and upper Santonian–lower Campanian of the Kheta River. They include remains of polycotylid and elasmosaurid plesiosaurians, as well as indeterminate small and osteologically immature plesiosaurians, indicating a somewhat typical Late Cretaceous plesiosaurian assemblage at the Arctic Polar Circle and implying that these shallow-water regions possibly used by plesiosaurians as a birth and nursery areas during the polar summer. In addition to plesiosaurian remains, a partial carinate ?mosasaurid tooth, and two turtle shell fragments, assigned to either non-marine Macrobaenidae or to marine Chelonioidea, and to non-marine Testudinoidea, are discovered, providing first direct evidence for the presence of these reptile groups in the Late Cretaceous of Northern Siberia. The findings of turtles are the northern most records of this group in the Cenomanian and Coniacian of Eurasia, which parallels previous records from the upper Cenomanian of Arctic Canada, and further supports warm climate conditions during the Cretaceous Greenhouse at high latitudes. Therefore, the Cenomanian–Turonian Boundary Event associated to the climate warming and to the beginning of the Cretaceous thermal maximum is well-recognized in Northern Siberia showing an expression of this “global” event over the Arctic region.
... A very unusual condition for theropods found in Irritator is that the maxillary teeth are very widely spaced, with the space between individual teeth being more than the mesiodistal length of the alveoli (Figures 1-2, 4B, 5-6). It is noteworthy that wide tooth spacing to this degree is otherwise predominantly observed in longirostrine aquatic taxa, including polycotylid plesiosaurs (e.g., Fischer et al., 2018) and derived tomistomine crocodylians (e.g., Brochu, 2001). However, this wide tooth spacing is not present in other spinosaurid snouts 16 (Charig and Milner, 1997;Sereno et al., 1998;Taquet and Russell, 1998;Dal Sasso et al., 2005) and also present in non-aquatic taxa, for instance Archaeopteryx , many pterosaurs (e.g., Wellnhofer, 1975;Andres et al., 2010;Pêgas et al., 2021), and some squamates (e.g., Conrad, 2008Conrad, , 2012. ...
Although originally described almost three decades ago, the holotype of Irritator challengeri from the Lower Cretaceous Romualdo Formation of Brazil still represents the most complete spinosaurid skull known to science. Here, we present a detailed description of the skull of Irritator based on digital reconstructions from medical and micro computed tomography (μCT) data. Segmentation reveals the near-complete palatal complex and braincase, an unusual morphology of the retroarticular process, a large, ventrally inclined surangular shelf and the tooth replacement pattern. The digitally reconstructed skull anatomy indicates a robust dentition, a field of binocular vision in front of the skull with an inclined snout orientation, a relatively weak but fast bite, as well as laterally spreading and rotating lower jaw rami during jaw opening. We modified an existing phylogenetic matrix of Tetanurae to account for new observations on the morphology of Irritator and analysed this using parsimony and Bayesian methods. Results support Spinosauridae as members of Megalosauroidea and recover a monophyletic Carnosauria (Megalosauroidea + Allosauroidea). Parsimony analysis recovers Monolophosaurus nested within Megalosauroidea as sister taxon to spinosaurids, but this is not supported by the Bayesian analysis. Bayesian time-calibration and evolutionary rate analysis indicate that spinosaurid evolution happened fast, despite a long ghost lineage of at least 35 million years. High evolutionary rates over a prolonged time can explain the highly derived skull morphology of spinosaurids. This study provides an in-depth look into the evolution of spinosaurid skull anatomy and refines our understanding of these specialized Mesozoic predators.
