Figure 20 - uploaded by Eberhard "Dino" Frey
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Comparison of the body outline of Mauriciosaurus fernandezi and Dermochelys coriacea. A) Schematic outline reconstruction of Mauriciosaurus fernandezi CPC RFG 2544 P.F.1. based on soft tissue evidence in ventral aspect. Note that trunk and tail form a functional unit with a drop-shaped outline with the thickest diameter lying anterior to the mid-section of the body. B) Outline sketch of a Leatherback Turtle (Dermochelys coriacea). Note that the drop-shaped outline of the carapace strikingly resembles the trunk-tail complex of Mauriciosaurus.
Source publication
A nearly complete skeleton of a polycotylid
plesiosaur is described from
the early Late Cretaceous laminated
limestones at Vallecillo, northeast
Mexico. It shows extensive soft tissue
preservation. In some exceedingly
well preserved areas there are transversely
elongate rectangular to trapezoid
millimetric scale-like structures
arranged in longitud...
Context in source publication
Context 1
... anatomical features, and the fact that the thickest part of the trunk and tail unit lies in its an- terior third, suggest swimming speeds comparable to that of modern sea turtles. Among these, the leatherback (Dermochelys coriacea), the fastest swim- ming sea turtle, travels at an average velocity of about 7 kph (Eckert, 2002) and shows a hydrody- namic carapace, the outline of which strikingly re- sembles the body outline of Mauriciosaurus ( Figure 20). This swimming speed falls within the range of swimming speeds reconstructed for Mesozoic marine reptiles (Massare, 1988). ...
Citations
... The knowledge of polycotylid plesiosaurians has greatly improved in recent decades due to new discoveries and reassessment of some important specimens (e.g. Clark et al., 2024;Fischer et al., 2018;Frey et al., 2017;Persons et al., 2022). However, some polycotylid taxa are still far from being well-known, including the name-giving genus Polycotylus Cope, 1869. ...
... This observation may be used as an additional trait for distinguishing juvenile and mature polycotylid individuals based on girdle elements. Despite its small size, the pectoral girdle elements of OGMM 507 have several traits of advanced ossification, such as wellpronounced posterolateral cornu of the coracoid, and long scapular dorsal ramus and ventral plate, which contrasts with significantly less ossified pectoral elements of juvenile Martinectes bonneri UNSM 55810 (O'Keefe & Byrd, 2012) and Mauriciosaurus fernandezi Frey et al., 2017. The scapulae of OGMM 507 have unfinished ossification along their anterior and dorsal margins. ...
... Moreover, ossification of these additional elements may be delayed in ontogeny and thus even the perfectly preserved but osteologically immature specimens with intact limbs (e.g. Frey et al., 2017) may have an incomplete set of postaxial ossicles. ...
Since the discovery of the holotype of Polycotylus sopozkoi in the Southern Urals, several skeletons referable to Polycotylus were collected from the upper Santonian – lower Campanian bone bed at its type locality (Izhberda quarry, Orenburg Region, Russia). Here we describe these new specimens, which together with the holotype constitute an ontogenetic series from small juveniles with the propodial length of 27 cm to a large adult individual with the propodial length exceeding 47 cm and traces of senile pathologies of limb elements. The new specimens significantly expand the knowledge of the morphology and variation of the postcranial skeleton in Polycotylus. They also reveal additional diagnostic features of Polycotylus sopozkoi (28 cervical vertebrae, one of the highest counts for polycotylines, and strongly tapered anterodistal processes of cervical ribs), and shared traits with P. latipinnis (divergent anteromedial processes and pronounced anterior shelf of the coracoid), which were previously unnoticed in the known specimens and supplement the generic diagnosis. The observed individual variation in Polycotylus sopozkoi has implications for phylogenetic and ontogenetic studies of plesiosaurs, and for assessment of the taxonomic value of some characters in polycotylids.
... 10 Indeed, the epidermal microstructure of MH 7 corresponds well to that of living amniotes, with an outermost stratum corneum comprising compacted corneocytes and an underlying stratum spinosum composed of younger, sub-spherical skin cells. 27-29 Frey et al. 2 suggested that the rarity of recovered plesiosaur skin might be due to their epidermis being thin, as in extant snakes, 35 and thus susceptible to rapid breakdown after death. Conversely, the combined depth of the stratum spinosum and stratum corneum in MH 7 (which was at least $250 mm) implies a thick epidermis, more compatible with that of living sea turtles (Figures S1F and S1G). ...
... The latter are represented by exquisitely preserved fossils of fishes (elasmobranchs, actinopterygians and actinistians) and marine reptiles (protostegid turtles, mosasauroids and polycotylid plesiosaurs) (e.g. [39][40][41][42]) (see electronic supplementary material, figure S1). ...
The fossil fish Ptychodus Agassiz, 1834, characterized by a highly distinctive grinding dentition and an estimated gigantic body size (up to around 10 m), has remained one of the most enigmatic extinct elasmobranchs (i.e. sharks, skates and rays) for nearly two centuries. This widespread Cretaceous taxon is common in Albian to Campanian deposits from almost all continents. However, specimens mostly consist of isolated teeth or more or less complete dentitions, whereas cranial and post-cranial skeletal elements are very rare. Here we describe newly discovered material from the early Late Cretaceous of Mexico, including complete articulated specimens with preserved body outline, which reveals crucial information on the anatomy and systematic position of Ptychodus. Our phylogenetic and ecomorphological analyses indicate that ptychodontids were high-speed (tachypelagic) durophagous lamniforms (mackerel sharks), which occupied a specialized predatory niche previously unknown in fossil and extant elasmobranchs. Our results support the view that lamniforms were ecomorphologically highly diverse and represented the dominant group of sharks in Cretaceous marine ecosystems. Ptychodus may have fed predominantly on nektonic hard-shelled prey items such as ammonites and sea turtles rather than on benthic invertebrates, and its extinction during the Campanian, well before the end-Cretaceous crisis, might have been related to competition with emerging blunt-toothed globidensine and prognathodontine mosasaurs.
... 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). ...
... During the evolution of the Polycotylidae, the podials (including phalanges) became increasingly shorter and wider over time; early polycotylids tend to have longer and slenderer limb elements than the highly derived species that possessed short and blocky phalanges (Schumacher, 2007). Phalanges from a polycotylid found in Mexico and illustrated and described in detail by Frey et al. (2017) are characterised by an hourglass shape and furthermore possess an almost straight interphalangeal articulation surface. The length/ breadth ratio of the phalanges is around 1.8 on average and the appearance of the bones is robust and short. ...
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.
... Williston (1908) is commonly cited as the author of this family (e.g. White, 1940;Persson, 1963;Kuhn, 1964;Thurmond, 1968;Adams, 1997;Storrs, 1999;Storrs et al., 2000;O'Keefe, 2004O'Keefe, , 2008Albright et al., 2007;Schumacher, 2007;Arkhangelsky and Sennikov, 2008;Ketchum and Benson, 2010;Benson and Druckenmiller, 2014;Schumacher and Martin, 2016;Efimov et al., 2016;Frey et al., 2017;Persons et al., 2022;Clark et al., 2024), however, approximately half of the contributions on polycotylids indicate authorship of Cope, while citing different works of this author published in 1869, although more often "Synopsys …" (i.e. Cope, 1869b; e.g. ...
... With the recent increase in research on polycotylids and the erection of several new genera and species (e.g. Frey et al., 2017;Persons et al., 2022;Clark et al., 2024) Cragin, 1888 from the CenomanianeTuronian of USA. We agree that no convincing character was proposed to distinguish Mauriciosaurus from Trinacromerum, and the genera appear potentially synonymous from the published descriptions (e.g. ...
... We agree that no convincing character was proposed to distinguish Mauriciosaurus from Trinacromerum, and the genera appear potentially synonymous from the published descriptions (e.g. Williston, 1908;Caprenter, 1996;O'Keefe, 2004;Frey et al., 2017). However, the clearly juvenile state of the holotype of M. fernandezi complicates its comparison with other polycotylids and probably bias its phylogenetic position to a more basal (see e.g. ...
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.
... Sometimes it is tricky to identify the actual vertebral formulas in osteologically mature plesiosaurs because of fusion of neural arches to the centra [38]. Although widely used, the concept of pectoral vertebrae is, however, not accepted by all researchers (e.g., [46,47]). Some recent studies opposed this traditional concept by combining pectorals into cervicals or dorsals ( [48,49,50]; [51,52,53]). ...
... Many previous studies stated that tails of plesiosaurs are too short to be used for propul-6 Hydrotherosaurus alexandrae Elasmosauridae about 1 cm between anterior cervical spines, and posterior cervicals almost touch; [36] Elasmosaurus platyurus Elasmosauridae intervertebral distances in the middle cervical region larger than 1 cm; [34] Kawanectes lafquenianum Elasmosauridae (assumed) intervertebral distance 2 mm each; [66] Aristonectine indet Elasmosauridae (assumed) intervertebral distance 2 mm each; [65] Multiple elasmosaurids Elasmosauridae (assumed) intercervical distance 1∼3 mm each; [64] Cryptoclidus eurymerus Cryproclididae 15%∼26% of anterior cervical lengths; [68] Cryptoclidus eurymerus Cryproclididae (assumed) intercervical distance 1∼3 mm each; [57] Muraenosaurus leedsi Cryproclididae 4%∼19% of anterior cervical lengths; [68] Ophthalmothule cryostea Cryproclididae intercervical distances 2.7∼5.8 mm (5.5%∼15.5% of cervical lengths, 9.3% by average); [54] Multiple plesiosauroids Plesiosauroidea (assumed) intercervical distance around 1 cm each; [69] Trinacromerum sion and can only function as tools for direction control, stabilization or streamlining [71,1,72,73,47]. However, this cognition may be biased due to the poor preservation of tails in many plesiosaur fossils [74,75,50,22]. ...
... Such a condition continued into late Jurassic and Cretaceous: thalassophoneans, cryptoclidids and elasmosaurids also possessed long tails comparative in length with their trunks (e.g., Peloneustes philarchus [43], Cryptoclidus eurymerus [38], Albertonectes vanderveldei [46]). But in polycotylids, the tails were much shortened, exemplified by Dolichorhynchops osborni and Mauriciosaurus fernandezi [78,47]. ...
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.
... This increases the width and total area of the horizontal projection of the tail, mainly the area of its most effective middle and, especially, posterior sections, which bend up and down with the greatest amplitude. The width of the tail is usually additionally greatly increased due to soft tissues, which is seen, for instance, in the platypus (Fig. 5c), the beaver, or the Cretaceous plesiosaur Mauriciosaurus fernandezi (Frey et al., 2017). Modern crocodiles and lizards, swimming with the help of lateral movements of the tail, have a powerful m. caudofemoralis longus. ...
... This increases the width and total area of the horizontal projection of the tail, mainly the area of its most effective middle and, especially, posterior sections, which bend up and down with the greatest amplitude. The width of the tail is usually additionally greatly increased due to soft tissues, which is seen, for instance, in the platypus (Fig. 5c), the beaver, or the Cretaceous plesiosaur Mauriciosaurus fernandezi (Frey et al., 2017). Modern crocodiles and lizards, swimming with the help of lateral movements of the tail, have a powerful m. caudofemoralis longus. ...
In ancient and modern aquatic and semi-aquatic tetrapods, several types of structure of the locomotor apparatus are presented, providing various styles of swimming. In the course of evolutionary adaptation to swimming, an important role was played by the morphological transformations of the tail, which often performs the main propulsion function. Modern reptiles (except turtles) swim mainly with the help of horizontal tail bends, while mammals swim either vertical or horizontal ones. Among extinct reptiles, Sauropterygia probably used vertical tail mobility when swimming. In most archosauromorphs, the tail became high, laterally compressed, and they swam mainly with the help of its horizontal movements. Among early archosaurs, Proterohampsians and Doswelliids are distinguished by their wide and dorsoventrally flat tails, which may indicate an adaptation to swimming using its vertical mobility.
... 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.
... Measurements (Table 1) Centra are short, length being~60% height (Table 1). Cervicals are about as long as tall in Nichollssaura (Druckenmiller and Russell, 2008) and Brancasaurus (Sachs et al., 2016), but shorter than long in Leptocleidus superstes (Kear and Barrett, 2011), L. capensis (Andrews, 1911), L. clemai (Cruickshank and Long, 1997), and in Polycotylidae (Frey et al., 2017). Centra are platycoelous. ...
Plesiosaurs were a long-lived and widespread group of marine reptiles, with a worldwide distribution and a temporal range from the Late Triassic to the Late Cretaceous. Most occur in marine deposits, but some occur in low-salinity, brackish to freshwater environments. We report plesiosaurs from the freshwater fluvial deposits of the mid-Cretaceous (?Albian-Cenomanian) Kem Kem Group of Morocco. Remains include numerous shed teeth, vertebrae, and a humerus. The humerus represents a young juvenile; vertebrae likely belong to sub-adults. Teeth show heavy wear, similar to teeth of co-occurring spinosaurids. While coeval plesiosaurs from the Bahariya Formation of Egypt are members of Polycotylidae, the Kem Kem fossils show features of Leptocleididae, small-bodied plesiosaurs that were widely distributed in nearshore and non-marine settings in the Early Cretaceous. These fossils are the first freshwater plesiosaurs from Morocco, and are among the youngest representatives of Leptocleididae. The Kem Kem leptocleidids could have been infrequent visitors from the sea, freshwater-tolerant, or even freshwater-adapted, as in modern river dolphins. The abundance of shed teeth in the Kem Kem Group supports the hypothesis that they had some degree of freshwater tolerance. Furthermore, leptocleidids occur almost exclusively in shallow nearshore, brackish, or freshwater environments, suggesting adaptation to shallow, low-salinity environments. Other plesiosaur groups and other Mesozoic marine reptiles, including teleosaurids and mosasaurids, also occur in freshwater settings, suggesting plesiosaurs and other marine reptiles frequently exploited non-marine environments.
