Hubbry Logo
PlesiosauroideaPlesiosauroideaMain
Open search
Plesiosauroidea
Community hub
Plesiosauroidea
logo
8 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
Plesiosauroidea
Plesiosauroidea
Plesiosauroidea
View on Wikipedia
from Wikipedia

Plesiosauroids
Temporal range: Late Triassic - Late Cretaceous, 210–66 Ma
Three plesiosauroids (clockwise from top left): Dolichorhynchops, Plesiosaurus, Traskasaura
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Superorder: †Sauropterygia
Order: †Plesiosauria
Clade: †Neoplesiosauria
Superfamily: †Plesiosauroidea
Gray, 1825
Subgroups

Plesiosauroidea (/ˈpliːsiəsɔːr/; Greek: πλησιος plēsios 'near, close to' and σαυρος sauros 'lizard') is an extinct clade of carnivorous marine reptiles. They have the snake-like longest neck to body ratio of any reptile. Plesiosauroids are known from the Jurassic and Cretaceous periods. After their discovery, some plesiosauroids were said to have resembled "a snake threaded through the shell of a turtle",[1] although they had no shell.

Plesiosauroidea appeared at the Early Jurassic Period (late Sinemurian stage) and thrived until the K-Pg extinction, at the end of the Cretaceous Period. The oldest confirmed plesiosauroid is Plesiosaurus itself, as all younger taxa were recently found to be pliosauroids.[2] While they were Mesozoic diapsid reptiles that lived at the same time as dinosaurs, they did not belong to the latter. Gastroliths are frequently found associated with plesiosaurs.[3]

History of discovery

[edit]
Autograph letter concerning the discovery of Plesiosaurus dolichodeirus (NHMUK PV OR 22656), from Mary Anning.

The first complete plesiosauroid skeletons were found in England by Mary Anning, in the early 19th century, and were amongst the first fossil vertebrates to be described by science. Plesiosauroid remains were found by the Scottish geologist Hugh Miller in 1844 in the rocks of the Great Estuarine Group (then known as 'Series') of western Scotland.[4] Many others have been found, some of them virtually complete, and new discoveries are made frequently. One of the finest specimens was found in 2002 on the coast of Somerset (England) by someone fishing from the shore. This specimen, called the Collard specimen after its finder, was on display in Taunton Museum in 2007. Another, less complete, skeleton was also found in 2002, in the cliffs at Filey, Yorkshire, England, by an amateur palaeontologist. The preserved skeleton is displayed at Rotunda Museum in Scarborough.

Description

[edit]

Plesiosauroids had a broad body and a short tail. They retained their ancestral two pairs of limbs, which evolved into large flippers.

It has been determined by teeth records that several sea-dwelling reptiles, including plesiosauroids, had a warm-blooded metabolism similar to that of mammals. They could generate endothermic heat to survive in colder habitats.[5]

Evolution

[edit]

Plesiosauroids evolved from earlier, similar forms such as pistosaurs. There are a number of families of plesiosauroids, which retain the same general appearance and are distinguished by various specific details. These include the Plesiosauridae, unspecialized types which are limited to the Early Jurassic period; Cryptoclididae, (e.g. Cryptoclidus), with a medium-long neck and somewhat stocky build; Elasmosauridae, with very long, flexible necks and tiny heads; and the Cimoliasauridae, a poorly known group of small Cretaceous forms. According to traditional classifications, all plesiosauroids have a small head and long neck but, in recent classifications, one short-necked and large-headed Cretaceous group, the Polycotylidae, are included under the Plesiosauroidea, rather than under the traditional Pliosauroidea. Size of different plesiosaurs varied significantly, with an estimated length of Trinacromerum being three meters and Mauisaurus growing to twenty meters.

Relationships

[edit]
Muraenosaurus, a cryptoclidid
Styxosaurus, an elasmosaurid
Trinacromerum, a polycotylid

Within Plesiosauroidea, there is a more exclusive group, Cryptoclidia. Cryptoclidia was named and defined as a node clade in 2010 by Hilary Ketchum and Roger Benson: the group consisting of the last common ancestor of Cryptoclidus eurymerus and Polycotylus latipinnis; and all its descendants.[6]

The smaller group within Cryptoclidia was erected prior, in 2007 under the name "Leptocleidoidea".[7] Although established as a clade, the name Leptocleidoidea implies that it is a superfamily. Leptocleidoidea is placed within the superfamily Plesiosauroidea, so it was renamed Leptocleidia by Hilary F. Ketchum and Roger B. J. Benson (2010) to avoid confusion with ranks. Leptocleidia is a node-based taxon which was defined by Ketchum and Benson as "Leptocleidus superstes, Polycotylus latipinnis, their most recent common ancestor and all of its descendants".[6] The following cladogram follows an analysis by Benson & Druckenmiller (2014).[8]

Plesiosauroidea

Behavior

[edit]
Restoration of a Plesiosaurus dolichodeirus pair, one catching a fish.

Unlike their pliosauroid cousins, plesiosauroids (with the exception of the Polycotylidae) were probably slow swimmers.[9] It is likely that they cruised slowly below the surface of the water, using their long flexible neck to move their head into position to snap up unwary fish or cephalopods. Their four-flippered swimming adaptation may have given them exceptional maneuverability, so that they could swiftly rotate their bodies as an aid to catching prey.

Contrary to many reconstructions of plesiosauroids, it would have been impossible for them to lift their head and long neck above the surface, in the "swan-like" pose that is often shown.[1][10] Even if they had been able to bend their necks upward to that degree (which they could not), gravity would have tipped their body forward and kept most of the heavy neck in the water.

On 12 August 2011, researchers from the U.S. described a fossil of a pregnant plesiosaur found on a Kansas ranch in 1987.[11] The plesiosauroid, Polycotylus latippinus, has confirmed that these predatory marine reptiles gave birth to single, large, live offspring—contrary to other marine reptile reproduction which typically involves a large number of small babies. Before this study, plesiosauroids had sometimes been portrayed crawling out of water to lay eggs in the manner of sea turtles, but experts had long suspected that their anatomy was not compatible with movement on land. The adult plesiosaur measures 4 m (13 ft) long and the juvenile is 1.5 m (4.9 ft) long.[12]

References

[edit]

Sources

[edit]
  • Carpenter, K (1996). "A review of short-necked plesiosaurs from the Cretaceous of the western interior, North America" (PDF). Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen. 201 (2): 259–287. doi:10.1127/njgpa/201/1996/259.
  • Carpenter, K. 1997. "Comparative cranial anatomy of two North American Cretaceous plesiosaurs". Pp. 91–216, in Calloway J. M. and E. L. Nicholls, (eds.), Ancient Marine Reptiles, Academic Press, San Diego.
  • Carpenter, K (1999). "Revision of North American elasmosaurs from the Cretaceous of the western interior". Paludicola. 2 (2): 148–173.
  • Cicimurri, D. J.; Everhart, M. J. (2001). "An elasmosaur with stomach contents and gastroliths form the Pierre Shale (Late Cretaceous) of Kansas". Transactions of the Kansas Academy of Science. 104 (3–4): 129–143. doi:10.1660/0022-8443(2001)104[0129:aewsca]2.0.co;2. S2CID 86037286.
  • Cope, E. D. (1868). "Remarks on a new enaliosaurian, Elasmosaurus platyurus". Proceedings of the Academy of Natural Sciences of Philadelphia. 20: 92–93.
  • Ellis, R. 2003. Sea Dragons' (Kansas University Press)
  • Everhart, M. J. (2000). "Gastroliths associated with plesiosaur remains in the Sharon Springs Member of the Pierre Shale (Late Cretaceous), western Kansas". Kansas Acad. Sci. Trans. 103 (1–2): 58–69. doi:10.2307/3627940. JSTOR 3627940.
  • Everhart, M. J. (2002). "Where the elasmosaurs roam...". Prehistoric Times. 53: 24–27.
  • Everhart, M. J. (2004). "Plesiosaurs as the food of mosasaurs; new data on the stomach contents of a Tylosaurus proriger (Squamata; Mosasauridae) from the Niobrara Formation of western Kansas". The Mosasaur. 7: 41–46.
  • Everhart, M. J. (2005). "Bite marks on an elasmosaur (Sauropterygia; Plesiosauria) paddle from the Niobrara Chalk (Upper Cretaceous) as probable evidence of feeding by the lamniform shark, Cretoxyrhina mantelli". PalArch. 2 (2): 14–24.
  • Everhart, M. J. 2005. "Where the Elasmosaurs roamed", Chapter 7 in Oceans of Kansas: A Natural History of the Western Interior Sea, Indiana University Press, Bloomington, 322 p.
  • Everhart, M. J. 2005. "Gastroliths associated with plesiosaur remains in the Sharon Springs Member (Late Cretaceous) of the Pierre Shale, Western Kansas" (on-line, updated from article in Kansas Acad. Sci. Trans. 103(1-2):58-69)
  • Everhart, M. J. (2005). "Probable plesiosaur gastroliths from the basal Kiowa Shale (Early Cretaceous) of Kiowa County, Kansas". Transactions of the Kansas Academy of Science. 108 (3/4): 109–115. doi:10.1660/0022-8443(2005)108[0109:ppgftb]2.0.co;2. S2CID 86124216.
  • Everhart, M. J. (2005). "Elasmosaurid remains from the Pierre Shale (Upper Cretaceous) of western Kansas. Possible missing elements of the type specimen of Elasmosaurus platyurus Cope 1868?". PalArch. 4 (3): 19–32.
  • Everhart, M. J. (2006). "The occurrence of elasmosaurids (Reptilia: Plesiosauria) in the Niobrara Chalk of Western Kansas". Paludicola. 5 (4): 170–183.
  • Everhart, M. J. (2007). "Use of archival photographs to rediscover the locality of the Holyrood elasmosaur (Ellsworth County, Kansas)". Transactions of the Kansas Academy of Science. 110 (1/2): 135–143. doi:10.1660/0022-8443(2007)110[135:uoaptr]2.0.co;2. S2CID 86051586.
  • Everhart, M. J. 2007. Sea Monsters: Prehistoric Creatures of the Deep. National Geographic, 192 p. ISBN 978-1-4262-0085-4.
  • Everhart, M. J. "Marine Reptile References" and scans of "Early papers on North American plesiosaurs"
  • Hampe, O., 1992: Courier Forsch.-Inst. Senckenberg 145: 1-32.
  • Lingham-Soliar, T (1995). "in". Phil. Trans. R. Soc. Lond. 347: 155–180.
  • O'Keefe, F. R. (2001). "A cladistic analysis and taxonomic revision of the Plesiosauria (Reptilia: Sauropterygia);". Acta Zool. Fennica. 213: 1–63.
  • Massare, J. A. (1988). "Swimming capabilities of Mesozoic marine reptiles: Implications for method of predation". Paleobiology. 14 (2): 187–205. Bibcode:1988Pbio...14..187M. doi:10.1017/s009483730001191x. S2CID 85810360.
  • Massare, J. A. 1994. Swimming capabilities of Mesozoic marine reptiles: a review. pp. 133–149 In Maddock, L., Bone, Q., and Rayner, J. M. V. (eds.), Mechanics and Physiology of Animal Swimming, Cambridge University Press.
  • Smith, A. S. 2008. Fossils explained 54: plesiosaurs. Geology Today. 24, (2), 71-75 PDF document on the Plesiosaur Directory
  • Storrs, G. W., 1999. An examination of Plesiosauria (Diapsida: Sauropterygia) from the Niobrara Chalk (Upper Cretaceous) of central North America, University of Kansas Paleontological Contributions, (N.S.), No. 11, 15 pp.
  • Welles, S. P. 1943. Elasmosaurid plesiosaurs with a description of the new material from California and Colorado. University of California Memoirs 13:125-254. figs. 1-37., pls. 12–29.
  • Welles, S. P. 1952. A review of the North American Cretaceous elasmosaurs. University of California Publications in Geological Science 29:46-144, figs. 1-25.
  • Welles, S. P. 1962. A new species of elasmosaur from the Aptian of Columbia and a review of the Cretaceous plesiosaurs. University of California Publications in Geological Science 46, 96 pp.
  • White, T (1935). "in". Occasional Papers Boston Soc. Nat. Hist. 8: 219–228.
  • Williston, S. W. (1890). "A new plesiosaur from the Niobrara Cretaceous of Kansas". Transactions of the Kansas Academy of Science. 12: 174–178. doi:10.2307/3623798. JSTOR 3623798., 2 fig.
  • Williston, S. W. 1902. Restoration of Dolichorhynchops osborni, a new Cretaceous plesiosaur. Kansas University Science Bulletin, 1(9):241-244, 1 plate.
  • Williston, S. W. 1903. North American plesiosaurs. Field Columbian Museum, Publication 73, Geology Series 2(1): 1-79, 29 pl.
  • Williston, S. W. (1906). "North American plesiosaurs: Elasmosaurus, Cimoliasaurus, and Polycotylus". American Journal of Science. 4. 21 (123): 221–234. Bibcode:1906AmJS...21..221W. doi:10.2475/ajs.s4-21.123.221., 4 pl.
  • Williston, S. W. (1908). "North American plesiosaurs: Trinacromerum". Journal of Geology. 16 (8): 715–735. Bibcode:1908JG.....16..715W. doi:10.1086/621573. S2CID 129889740.
  • ( ), 1997: in Reports of the National Center for Science Education, 17.3 (May/June 1997) pp 16–28.
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Plesiosauroidea

View on Grokipedia
from Grokipedia
Plesiosauroidea is a monophyletic clade of Mesozoic marine reptiles within the larger group Plesiosauria (Sauropterygia), characterized by an elongated cervical region (typically comprising more than half of the presacral vertebral column), a relatively small skull, and four enlarged, paddle-like limbs adapted as hydrofoils for dynamic aquatic locomotion. These reptiles exhibited a stiff trunk, short tail, and specialized vertebral morphology, such as blade-like dorsal neural spines and cervical neural spines not angled posteriorly, enabling efficient cruising in marine environments. Plesiosauroidea originated from basal sauropterygians near the Triassic-Jurassic boundary around 201 million years ago, with the earliest unequivocal records appearing in the , and persisted as a dominant component of marine ecosystems until their during the Cretaceous-Paleogene event approximately 66 million years ago. The underwent significant diversification, particularly during the and , evolving into several families including Microcleididae, Cryptocleididae, Leptocleididae, Elasmosauridae, and , which displayed varied neck lengths (from moderately long to extreme in elasmosaurids exceeding 70 ), body sizes ranging from 3 to over 14 meters, and adaptations for different predatory niches such as nektonic foraging on and cephalopods. Phylogenetic analyses indicate that traditional short-necked "pliosauromorphs" like are nested within Plesiosauroidea, reflecting multiple convergences on similar body plans across Plesiosauria. Recent discoveries, including the transitional taxon Franconiasaurus brevispinus from the Lower Jurassic of , reveal a mosaic of primitive and derived traits—such as reduced processes and short neural spines—bridging early plesiosauroids to more specialized cryptoclidians and underscoring a major around 175-171 million years ago.

Classification and Phylogeny

Definition and Taxonomy

Plesiosauroidea is an extinct clade of carnivorous marine reptiles within the order Plesiosauria, belonging to the larger group , and is distinguished by its members' characteristically long necks relative to body length and four hydrofoil-like flippers of approximately equal size that facilitated underwater propulsion. These reptiles inhabited oceans from the to the , preying primarily on fish and cephalopods through a combination of neck flexibility and limb-powered swimming. The was formally defined in a node-based manner by O'Keefe (2001) as the most inclusive group containing the Plesiosaurus dolichodeirus (Conybeare, 1821) and all descendants of their with Euplesiosauria, a derived encompassing more specialized forms. This definition emphasizes shared morphological traits such as a reduced and specific vertebral counts that support . Subsequent phylogenetic revisions have incorporated short-necked derived forms like within the , reflecting convergences in body plans. The superfamily name Plesiosauroidea was established by Welles (1943) to group long-necked plesiosaurs (plesiosauromorphs), building on earlier informal distinctions between long- and short-necked forms proposed by Owen (1841) and Seeley (1874). Taxonomic revisions have incorporated families such as Plesiosauridae (basal Jurassic forms), Elasmosauridae (extreme long-necked Cretaceous taxa like Elasmosaurus), Microcleididae and Leptocleididae (early diverging Jurassic groups), Cryptocleididae (Middle-Late Jurassic mid-necked forms), and (short-necked but derived Cretaceous members). Earlier classifications, such as those by Tarlo (), emphasized sternal and pelvic girdle traits, but cladistic analyses like O'Keefe's resolved Plesiosauroidea as monophyletic, reorganizing Cryptocleidoidea to include polycotylids and affirming its distinction from the short-necked . In modern frameworks, Plesiosauroidea represents a well-supported lineage originating near the Triassic- boundary and diversifying globally until the end- , encompassing both predominantly long-necked forms and derived short-necked lineages.

Major Families and Genera

Plesiosauroidea comprises several major families that highlight the group's morphological diversity, particularly in neck length and body proportions, spanning the and periods. Basal families include Microcleididae and Leptocleididae, which represent early-diverging forms from the Early to with moderate neck lengths (typically 30-40 ) and are known primarily from European deposits. Representative genera in Microcleididae include Microcleidus homalospondylus, featuring a small head, robust limbs, and slightly elongated cervicals for enhanced maneuverability in coastal environments, and Aphrosaurus fossilensis from . Leptocleididae encompasses genera like Leptocleidus superstes and Nichollssaura borealis, characterized by similar proportions but with adaptations for both marine and possibly freshwater habitats, as evidenced by fossils from and . The Plesiosauridae, another early group, is characterized by relatively short to moderate necks (typically 20-40 cervical vertebrae) and is best known from Early Jurassic deposits in Europe. The type genus Plesiosaurus dolichodeirus features a small head and robust limbs adapted for paddling. The Cryptoclididae, prominent during the Middle to Late Jurassic, represent a diversification of mid-sized plesiosauroids with necks comprising 30-50 vertebrae, enabling flexible foraging in open marine settings. Key genera include Cryptoclidus oxoniensis, known from well-preserved skeletons in the Oxford Clay Formation of England, which possessed a deeper skull with robust teeth for grasping fish and cephalopods, and Tricleidus lacustris, distinguished by its slender build and elongated rostrum. These forms dominated Jurassic seas, with fossils reported from Europe and potentially North America, reflecting a peak in plesiosauroid abundance before the Cretaceous. Polycotylidae, a derived family, is characterized by short necks (typically 15-20 ), large heads with elongated snouts, and powerful flippers suited for fast pursuit predation. This family, nested within Plesiosauroidea as the to Elasmosauridae, includes genera such as Polycotylus latipinnis from the of , featuring triangular teeth for catching fish and squid, and Dolichorhynchops osborni, known for its agile build and widespread distribution across marine environments. Fossils are primarily from , with recent finds in and elsewhere indicating global presence. Elasmosauridae, the most derived long-necked family, flourished in the and is defined by exceptionally elongated necks (up to 70-76 ), comprising over half the total body length in some specimens. Exemplified by platyurus from the Smoky Hill Chalk of , this family features a tiny head relative to the neck, slender teeth for filter-feeding or snaring soft-bodied prey, and hyper-elongated limb girdles for efficient cruising. Other genera, such as Libonectes atlas, share these traits but vary in vertebral counts, underscoring adaptive radiations in epicontinental seas. Taxonomic revisions have reduced the number of valid genera within Plesiosauroidea to approximately 60, with many former assignments to reclassified as junior synonyms or distinct taxa like Hydrorion brachypterygius due to differences in vertebral morphology and limb structure. Nomenclatural challenges persist, particularly in resolving synonymies from fragmentary specimens, emphasizing the need for ongoing phylogenetic analyses to clarify diversity.

Evolutionary Relationships

Plesiosauroidea forms a monophyletic within the larger group Plesiosauria, which itself is nested within the marine reptile Sauropterygia, and is consistently recovered as the to the short-necked in cladistic analyses. This relationship is supported by shared derived traits at the Plesiosauria level, such as the hyperphalangy of the limb autopodia (more than five phalanges per digit) and modifications to the pectoral girdle for enhanced aquatic propulsion, but Plesiosauroidea is distinguished by further specializations including an elongated cervical vertebral series typically exceeding 40 elements, enabling the characteristic long-necked body plan. These synapomorphies underscore the early divergence of Plesiosauroidea from pliosauroids during the , with the originating from basal sauropterygians that had already adapted to fully marine lifestyles by the . Internally, the phylogeny of Plesiosauroidea reveals a basal grade of early-diverging forms, such as those in Microcleididae and Leptocleididae, which exhibit moderate neck elongation (around 30-40 cervical vertebrae) and represent the initial radiation in the Early to Middle Jurassic. More derived lineages include the Middle to Late Jurassic Cryptoclididae, characterized by intermediate neck lengths, followed by the highly specialized Elasmosauridae and their sister group Polycotylidae in the Late Cretaceous, with elasmosaurids possessing the most extreme elongation (up to 76 cervical vertebrae) and positioned as a terminal clade within Plesiosauroidea. Phylogenetic analyses recover Polycotylidae firmly within Plesiosauroidea due to shared features like expanded pterygoid plates and a vomeronasal fenestra. Cladistic evidence from comprehensive datasets, such as the 152-character matrix of Druckenmiller and Russell (2008) and its updates incorporating additional taxa and characters (e.g., Benson et al. 2012), depicts as a robust with moderate to high support values, including Bremer decay indices of 2-4 for the node uniting basal plesiosauroids and a bootstrap support of 65% for the elasmosaurid position in time-calibrated trees. These analyses, based on parsimony and Bayesian methods, highlight sequential branching: basal taxa like Plesiopterys and Anningasaura at the root, followed by a resolving into cryptoclidian and elasmosauriform lineages, with low inconsistency indices (0.15-0.20) indicating strong congruence among morphological data from over 50 ingroup taxa. Recent additions, such as transitional forms like Franconiasaurus, further reinforce this topology by filling gaps between basal and derived branches, with posterior probabilities exceeding 0.8 in Bayesian implementations.

Anatomy and Morphology

Overall Body Plan

Plesiosauroids exhibited a highly specialized quadrupedal uniquely adapted for marine existence, characterized by a streamlined, torso that minimized hydrodynamic drag during swimming. This morphology included four robust, paddle-like limbs serving as primary propulsors through underwater flight-like motions, with the limbs modified from ancestral configurations via hyperphalangy and elongation of elements. The overall form contrasted sharply with terrestrial reptiles, emphasizing control and efficient cruising in open water environments. The featured a notably short trunk region comprising 18–22 dorsal vertebrae, which contributed to the rigid, compact mid-body structure and supported the attachment of single-headed forming a robust thoracic basket. In marked contrast, the cervical series displayed extreme variability in length, ranging from moderate proportions in basal forms to exceptionally elongated configurations; for instance, elasmosaurids such as platyurus possessed up to 72 , enabling necks that could exceed half the total body length. This disparity in vertebral counts underscored the clade's morphological diversity while maintaining a conserved trunk design across taxa. Body sizes within Plesiosauroidea spanned a broad spectrum, typically from 3 to 15 meters in total length, with smaller basal representatives like Plesiosaurus measuring around 3–5 meters and advanced elasmosaurids approaching 12–14 meters. Mass estimates, derived from volumetric modeling of skeletal reconstructions and assuming densities akin to modern marine reptiles (approximately 900–1100 kg/m³), ranged from 1 ton for diminutive species to over 10 tons for the largest forms, highlighting their ecological roles from mid-tier predators to apex consumers. Preserved skin impressions reveal a predominantly smooth, scaleless across the torso and tail, likely reducing frictional resistance during locomotion, while small, triangular scales occurred along the trailing edges of the flippers, possibly aiding in maneuverability or substrate interaction. This texture, documented in Lower specimens, suggests adaptations for streamlined swimming efficiency, with potential for pigmentation inferred from broader patterns in marine reptiles, though direct evidence remains limited.

Neck and Head Structure

The skulls of plesiosauroids were typically small relative to body size, featuring a compact, triangular shape with a short adapted for piscivory. These skulls exhibited relatively large orbits, which likely enhanced vision in low-light marine environments, compared to smaller temporal fenestrae that supported a streamlined cranial with a single temporal opening. The consisted of slender, conical or needle-like teeth with recurved, interlocking tips, facilitating the grasping and retention of slippery fish prey without requiring strong crushing force. The hyperelongated necks characteristic of plesiosauroids resulted primarily from an increase in the number of rather than elongation of individual , enabling necks to comprise a substantial portion of total body length. Basal forms typically possessed 28–32 , while advanced elasmosaurids like platyurus reached up to 72, resulting in necks estimated at approximately 7.1 meters long in large specimens. Neck flexibility was facilitated by zygapophyses that permitted significant lateral and ventral bending for maneuvering during feeding, though vertical motion was more restricted due to overlapping and broad that maintained structural integrity during swimming. The braincase and of plesiosauroids displayed adaptations suited to pelagic lifestyles, including a compact, bulbous endosseous with short, wide that differed from the more elongate forms in nearshore ancestors. These features, such as subequal anterior and posterior canal heights and a laterally bowed horizontal canal, supported enhanced postural equilibrium and in three-dimensional underwater environments. The overall endocranial morphology, with elongated olfactory tracts, reduced pineal organs, and prominent optic lobes alongside a large , indicated well-developed visual and auditory capabilities, potentially including sensitivity to through modifications like robust structures.

Limbs and Locomotion Adaptations

Plesiosauroids possessed four large, wing-like flippers adapted for aquatic , with both fore- and hindlimbs evolving into hydrofoil-shaped structures that facilitated lift-based . These flippers were characterized by hyperphalangy, featuring an increased number of phalanges beyond the typical pentadactyl condition, resulting in elongated and tightly interlocking bones that tapered to fine tips for enhanced rigidity and streamlining. The and were robust and heavily muscled, with prominent glenoid processes that restricted motion to dorso-ventral oscillations, supporting dynamic underwater movements akin to flight. Locomotion in plesiosauroids is inferred to have resembled underwater flight, primarily powered by alternating or synchronized strokes of the flippers, with (CFD) simulations indicating dominance for generation. In models of taxa like Meyerasaurus, executed primary propulsive strokes similar to those in modern sea turtles and , achieving cruising speeds of approximately 0.48 m/s, while hindlimbs provided supplementary for stability and maneuverability rather than main . Synchronized use of all four flippers in tandem configurations enhanced overall performance, with hindlimbs contributing up to 60% more and enabling versatile transitions between cruising and sprinting. Buoyancy control in plesiosauroids likely involved a combination of anatomical features and behavioral adaptations, including dorsally positioned lungs occupying about 10% of body volume to counter the high buoyancy of their lightweight skeletal structure. Gastroliths, or stomach stones, were present with total masses typically less than 0.2% of body weight, likely aiding digestion or food processing rather than buoyancy control, as per recent analyses of Alberta specimens. Myotome arrangements, inferred from muscle reconstructions, supported efficient body undulation to complement flipper-driven locomotion and maintain equilibrium in three dimensions. Energy efficiency in plesiosauroid swimming was notably high compared to modern analogs like sea turtles, which also employ flipper-based flight but rely more heavily on forelimbs alone. Coordinated four-flipper yielded up to 40% greater hydrodynamic through reduced drag coefficients and optimized Strouhal numbers (0.18 for cruising), allowing sustained with minimal expenditure relative to body mass. This underscores the evolutionary convergence in marine tetrapods for low-cost, long-distance locomotion in open oceans.

Evolutionary History

Origins and Early Forms

Plesiosauroidea emerged near the Triassic-Jurassic boundary around 201 million years ago, likely from basal sauropterygian ancestors within the broader radiation that included early plesiosaurians such as pistosaurs. This origin reflects a key transition in evolution, where basal plesiosaurians adapted to fully aquatic lifestyles following the diversification of earlier stem-group sauropterygians. The clade's phylogenetic position places it as a derived branch of Plesiosauria, stemming from forms that exhibited intermediate morphologies between nothosauromorphs and more specialized plesiosaurians. The earliest records of Plesiosauroidea date to the early stage of the , with Plesiosaurus dolichodeirus representing one of the oldest known members. A basal plesiosaurian from deposits in , Rhaeticosaurus mertensi, represents an early short-necked form in the pliosauroid lineage. These forms document the initial radiation of the group around the Triassic-Jurassic boundary. Recent discoveries, such as the transitional Franconiasaurus brevispinus from the Lower of (ca. 175-171 Ma), reveal a of primitive and derived traits—such as reduced cervical rib processes and short neural spines—bridging early plesiosauroids to more specialized cryptoclidians and underscoring a major . Transitional features in these early plesiosauroids include a gradual elongation of the neck relative to ancestral sauropterygians, with increasing in number and length to enhance reach without extreme specialization seen in later taxa. Limb adaptations progressed toward equalization of fore- and hind-limb sizes, developing into broad, paddle-like flippers for efficient underwater propulsion, a shift from the more asymmetrical paddling in pre-plesiosaurian relatives. This early evolution unfolded in the context of recovery from the end-Triassic mass extinction, within shallow epicontinental seas that characterized the paleoenvironments of the Tethyan margins and proto-Atlantic regions. These habitats, including lagoonal and nearshore settings, provided niches for the initial diversification of plesiosauroids amid reduced competition from other marine reptiles affected by the extinction event.

Diversification Across Periods

Plesiosauroidea underwent significant diversification following their emergence in the , with early representatives appearing in the Lower strata of . Forms such as Microcleidus from the and stages of and Seeleyosaurus guilelmiimperatoris from the of exemplify these initial radiations, characterized by moderately elongated necks and adaptations for shallow marine environments. These taxa represent basal plesiosauroids that contributed to the group's expansion into more open oceanic niches during this period. The witnessed a peak in plesiosauroid diversity, particularly in the Middle and Late stages, where cryptoclidids emerged as a dominant across the . This family, including genera like and Kimmerosaurus, proliferated in deposits such as the Formation of , where they formed a significant component of assemblages. Their success is evidenced by abundant skeletal remains in these Kimmeridgian-Tithonian sediments, reflecting adaptive radiations tied to expanding epicontinental seas. Overall, the fossil record documents approximately 20 plesiosauroid genera, highlighting a phase of moderate centered in European waters. Transitioning into the , plesiosauroids experienced further expansion, with elasmosaurids marking a key phase of radiation in the . Basal elasmosaurids, such as Lagenanectes richterae from the of , indicate the onset of this group's proliferation, featuring further neck elongation relative to predecessors. By the , elasmosaurids achieved a global distribution, with fossils reported from , , , and , underscoring their adaptation to diverse marine provinces. The record reveals heightened , with over 30 genera known, surpassing levels and reflecting enhanced sampling and ecological opportunities in widespread seaways. Adaptive trends during these periods included progressive increases in neck length among plesiosauroids, which correlated with shifts toward exploiting larger or more mobile prey items in stratified water columns. This morphological facilitated niche partitioning, particularly with short-necked pliosaurs, where plesiosauroids occupied roles as pursuit predators targeting schooling and cephalopods, while pliosaurs dominated as ambush specialists on larger vertebrates. Such partitioning is supported by functional analyses of craniomandibular and dental traits, illustrating complementary ecological roles within marine ecosystems.

Decline and Extinction

During the , Plesiosauroidea maintained a degree of dominance in marine ecosystems, with diverse elasmosaurids and polycotylids persisting into the stage (72.1–66 million years ago). Fossil records indicate their presence across multiple continents, including and , exemplified by the elasmosaurid Alexandronectes zealandiensis from strata in . Specific lineages like elasmosaurids remained viable until the very end of the . The extinction of Plesiosauroidea at the K-Pg boundary approximately 66 million years ago was driven by a confluence of catastrophic events, primarily the Chicxulub asteroid impact, Deccan Traps volcanism, and associated marine regression. The asteroid strike off the Yucatán Peninsula triggered an "impact winter," blocking sunlight and collapsing primary productivity, which disrupted marine food webs from plankton upward. Plesiosauroids, as specialized piscivores reliant on fish populations that in turn depended on plankton, suffered from this trophic cascade, as evidenced by stable isotope analyses showing uniform diets among late Maastrichtian elasmosaurids and polycotylids. Concurrent Deccan volcanism released massive sulfur and CO₂, exacerbating global cooling and ocean acidification, while falling sea levels reduced shallow marine habitats critical for these reptiles. These factors collectively led to the near-total eradication of non-avian marine reptiles, with no unequivocal Plesiosauroidea fossils post-dating the boundary. Claims of Plesiosauroidea survival beyond the K-Pg boundary, such as alleged elasmosaur sightings or carcasses in the mid-20th century, have been thoroughly debunked as misidentifications. For instance, a 1977 carcass hauled aboard the Japanese trawler Zuiyo-maru was initially speculated to be a but was confirmed through anatomical and analysis to be a decayed (Cetorhinus maximus). Similar reports from the , often involving washed-up marine remains misinterpreted amid post-war excitement over , lack supporting evidence and align with known patterns of decay in large cetaceans or sharks rather than archaic reptiles. No verified post-Cretaceous fossils or genetic traces support survival. In comparison to their short-necked relatives, the , Plesiosauroidea exhibited a more protracted decline, with pliosauroids like brachauchenines vanishing by the stage (~93–89 million years ago) due to niche competition from rising mosasauroids. The long-necked specialization of plesiosauroids, suited for ambush predation in stable epicontinental seas, may have buffered them against earlier Mid-Cretaceous perturbations but rendered them vulnerable to the terminal K-Pg disruptions in open-ocean food webs. This rigidity contrasts with the more versatile mosasauroids, which also succumbed at the boundary but dominated the interim.

Discovery and Research

Initial Discoveries

The initial discovery of a plesiosauroid occurred in December 1823, when renowned fossil collector unearthed an nearly complete skeleton at on the of . This specimen, from the Lower Jurassic , represented a novel with a long neck, small head, and four large paddles, later named Plesiosaurus dolichodeirus by William Daniel Conybeare in his 1824 description presented to the . The find sparked immediate interest but also controversy, as French anatomist initially dismissed it as a potential assembled from parts of known reptiles like ichthyosaurs and crocodiles; Conybeare countered this by emphasizing the specimen's anatomical coherence and marine adaptations. Key figures in these early 19th-century European discoveries included Anning, who supplied numerous specimens to scientists, as well as geologists and , who supported her work and disseminated findings through institutions like the Geological Society. Initial artistic reconstructions often depicted plesiosaurs as terrestrial quadrupeds capable of crawling on land with limb-like paddles, reflecting limited understanding of their aquatic lifestyle; however, Conybeare's analysis highlighted flipper-like limbs suited for swimming, shifting perceptions toward fully marine reptiles. Most early fossils came from British Jurassic sites, particularly the exposures at and nearby coastal localities, where ammonite-rich shales preserved these reptiles in abundance. Further controversies arose as additional specimens emerged. A more notorious error occurred in the 1870s during the American "Bone Wars," when described Elasmosaurus platyurus in 1868 but erroneously placed its small head on the short tail end, resulting in an implausibly long neck exceeding 70 vertebrae; rival [Othniel Charles Marsh](/page/Othniel Charles Marsh) publicly corrected this in 1870, highlighting the anatomical impossibility and fueling rivalry between the two paleontologists. By the 1840s, plesiosauroid remains began appearing in , with Leidy describing specimens from deposits in , expanding the known distribution beyond .

Key Fossil Sites and Specimens

Plesiosauroid fossils have been recovered from numerous localities worldwide, spanning the and periods, with key sites providing insights into their diversity and distribution. The Formation in , particularly the Member of age, has yielded significant remains of cryptoclidids such as eurymerus, including multiple partial skeletons that preserve details of their short-necked morphology. Similarly, the in southern Germany, a () , has produced rare plesiosauroid fragments, including elements attributable to early long-necked forms, though these are less common than associated ichthyosaur and pterosaur remains. In North America, the Niobrara Chalk Formation of Kansas, dating to the Santonian-Campanian stages, is renowned for elasmosaurid specimens, including those of Styxosaurus snowii, which represent some of the most complete Late Cretaceous plesiosauroids from the Western Interior Seaway. This site has preserved articulated cervical vertebrae and paddle elements, highlighting the extreme neck elongation characteristic of elasmosaurs. The Pierre Shale in western Kansas and South Dakota has also contributed iconic elasmosaur finds, such as partial skeletons of Elasmosaurus platyurus, though these often suffer from disarticulation due to depositional environments. Notable specimens include the holotype of Plesiosaurus dolichodeirus (NHMUK PV OR 22656), a nearly complete skeleton from the of , , which exemplifies the basal plesiosauroid with its moderate neck length and four flippers. Another significant example is the holotype of Styxosaurus snowii (KUVP 400, now KU 400), an articulated skull and anterior neck from the Niobrara Chalk, providing the first intact elasmosaurid cranium for study. Preservation in plesiosauroid fossils is generally fragmentary, with fully articulated skeletons being rare owing to the marine depositional settings that promote scattering; however, exceptional cases include those with preserved stomach contents, such as fish scales and bones in a Tatenectes laramiensis specimen (a cryptoclidid relative) from the Sundance Formation of , indicating piscivorous habits. Recent discoveries have expanded the record, particularly in high-latitude settings. In , a partial postcranial of a giant aristonectine elasmosaurid (MLP 09-X-4-1) from the López de Bertodano Formation on Vega Island, dated to the , reveals body sizes exceeding 10 meters and underscores Gondwanan . In , nearly complete elasmosaurid specimens from the in Río Negro Province, including a 2015-reported individual (MMCh-PV 2015-1), have added to the Campanian-Maastrichtian diversity with well-preserved axial elements. These finds, often from fine-grained marine sediments, occasionally preserve impressions, though full articulation remains exceptional. As of 2025, notable additions include the nearly complete of Plesiopterys wildi from the of , revealing early diversification of cryptoclidian precursors, and a complete from outback , , the first such articulated specimen from the (2024).

Advances in Study Techniques

Advances in non-destructive imaging techniques, particularly computed tomography (CT) scanning, have revolutionized the study of plesiosauroid internal anatomy and since the early 2000s. CT scans of exceptionally preserved specimens, such as the plesiosauromorph Nichollssaura borealis, allow for the creation of high-resolution 3D models of , revealing osteological constraints like zygapophyseal facets and that limit neck flexibility. These models quantify intervertebral (ROM), demonstrating average lateral bending of approximately 13° per joint, with reduced dorsal and ventral flexion around 11° and 10°, respectively, indicating that plesiosauroid necks were adapted for precise, lateral strikes rather than extreme coiling. Such analyses have also exposed internal impressions and vascular structures, providing insights into muscle attachments and neural canal morphology that were previously inaccessible without destructive preparation. Stable , especially oxygen isotope (δ¹⁸O) analysis of tooth , has provided key evidence for plesiosauroid physiology, particularly . Studies of plesiosauroid teeth from diverse latitudes show consistently high body temperatures of about 35 ± 2°C, comparable to modern marine mammals and exceeding those inferred for contemporaneous cold-blooded ectotherms like . This uniformity in δ¹⁸O values across tropical and temperate environments suggests endothermy or regional , enabling plesiosauroids to maintain elevated metabolic rates and potentially undertake long-distance migrations into cooler waters without . These findings challenge earlier assumptions of ectothermy and highlight adaptations for active, high-energy lifestyles in oceans. Computational modeling, including finite element analysis (FEA) and 3D biomechanical simulations, has enhanced understanding of plesiosauroid feeding and locomotion. FEA applied to skulls like that of the Libonectes morgani simulates bite-induced stresses, revealing that adductor muscles generated forces sufficient to handle soft-bodied prey, with von Mises stresses peaking at around 100 MPa during occlusion and indicating robust but not exceptionally powerful jaws compared to short-necked relatives. Bite force models for plesiosauroids typically estimate values up to several hundred Newtons, emphasizing puncture-and-tear feeding strategies over crushing. Complementing this, 3D finite element models of vertebrae in like Cryptoclidus eurymerus quantify flexibility limits, showing maximal lateral ROM of 70-80° for the entire , which informs hydrodynamic simulations of swimming efficiency. Bayesian relaxed-clock methods, calibrated with fossil occurrences, have refined plesiosauroid evolutionary timelines by integrating morphological and stratigraphic constraints. These analyses, applied to comprehensive phylogenies, place the origin of Plesiosauria in the around 235-240 Ma, predating the earliest definitive s and suggesting a hidden diversification phase before the radiation. Such tip-dating approaches account for incomplete sampling and variable evolutionary rates, providing more precise divergence estimates than traditional node-calibration methods and linking plesiosauroid emergence to post-extinction recovery in marine ecosystems. Recent advances as of include analysis of soft tissues from a 183-million-year-old , revealing preserved scales and body outline via advanced imaging.

Paleobiology and Ecology

Diet and Predatory Behavior

Plesiosauroids exhibited a varied diet, including piscivory on soft-bodied and cephalopods, as well as bottom-feeding on soft-bodied benthic in some taxa. Their conical, needle-like teeth were well-suited for piercing and holding slippery prey such as , preventing escape during capture. This dental morphology, observed in genera like , aligns with that of modern piscivores, emphasizing a feeding strategy focused on agile, mid-sized aquatic vertebrates rather than crushing hard-shelled organisms. Direct evidence from fossil gut contents further supports this dietary diversity, with remains of small and soft-bodied often preserved in association with plesiosauroid skeletons. Some specimens also contain gastroliths—smooth, rounded stones accumulated in the stomach—the function of which is debated, with hypotheses including mechanical digestion by grinding ingested prey or providing for control. These stones, documented in elasmosaurid plesiosaurs from deposits, occur in varying numbers and masses across specimens. Predatory behavior in plesiosauroids is inferred to have involved tactics, leveraging the elongated as a rapid "strike organ" to surprise prey. Biomechanical models indicate that elasmosaur necks could achieve lateral excursions of up to 176°, enabling quick arcing motions for prey interception without full-body repositioning. This flexibility supported a sit-and-wait strategy, where the animal held a straight-necked posture before executing a swift lateral or ventral sweep, ideal for targeting evasive in open water. Basal plesiosauroids, such as those from the , exhibited more generalist habits, consuming a broader range of and , while advanced elasmosaurs specialized on small schooling , as evidenced by associated remains. Rare instances of cephalopod hooks and beaks in gut contents point to occasional inclusion of soft-bodied mollusks in their diet, particularly in polycotylids. Within marine food webs, plesiosauroids occupied mid- to high-trophic levels as versatile predators, preying on abundant nektonic organisms but in some cases approaching apex roles similar to pliosaurs, which targeted larger marine reptiles. This positioning is reflected in isotopic and assemblage data from sites, where plesiosauroids competed with other mid-level carnivores like mosasaurs for resources, contributing to ecosystem stability without dominating the top tiers.

Reproduction and Life Cycle

Plesiosauroids are inferred to have been , giving birth to live young rather than laying eggs, based on the absence of fossilized eggs and direct evidence from a gravid specimen of the polycotylid Polycotylus latipinnis containing a single large preserved within the maternal body cavity. This reproductive mode aligns with the narrow pelvic structure observed in plesiosauroids, which lacks the robust, expandable form suitable for oviposition seen in oviparous reptiles, as noted in early cladistic analyses of the group. Embryo fossils in related sauropterygians, such as nothosaurs, further support the evolution of within the broader , likely as an to fully aquatic lifestyles that precluded returning to land for egg-laying. Bone histology reveals rapid growth rates during juvenile stages in plesiosauroids, with primary tissue dominated by fibrolamellar structures indicative of high metabolic rates and fast deposition, comparable to those in endothermic vertebrates like birds. Skeletochronology, using lines of arrested growth (LAGs) in long bones, indicates extremely accelerated early ontogeny, with circumferential growth rates around 90-100 μm/day in taxa such as and elasmosaurids, translating to substantial linear increases in body length during the first few years. was likely reached relatively early, within 3-5 years, as inferred from growth trajectories in related early sauropterygians and the large birth sizes observed in plesiosauroid fossils, which minimized the vulnerable neonatal phase. Minimum ages from LAG counts indicate individuals of small-bodied adults like the elasmosaurid Kawanectes lafquenianum reached at least 11-14 years, with extensive secondary remodeling suggesting potentially longer lifespans typical of large marine reptiles. Secondary bone remodeling and robusticity variations in humeri and femora between specimens indicate potential sexual dimorphism, with males possibly exhibiting denser cortical bone for agonistic interactions during reproductive periods. The reproductive strategy of plesiosauroids aligns with a K-selected life history, characterized by few offspring (likely single large young per pregnancy), high , and delayed , as evidenced by the polycotylid and the overall rarity of juvenile fossils relative to adults. Low in marine deposits, compared to more abundant ichthyosaurs or mosasauroids, further supports stable, low-density populations adapted to resource-limited oceanic environments rather than r-selected explosive . This strategy contributed to their long-term evolutionary success across seas, emphasizing quality over quantity in offspring survival.

Habitat and Environmental Interactions

Plesiosauroids primarily inhabited epicontinental seas and continental shelf margins during the Mesozoic, with abundant fossil evidence from shallow marine deposits such as the Lower Cretaceous strata of the Neuquén Basin in Argentina, where long-necked elasmosaurs are associated with offshore to shoreface environments typically less than 200 meters deep. In North America, species like Unktaheela specta occupied the Western Interior Seaway, a vast epicontinental system spanning temperate to subtropical latitudes, where sedimentary records indicate water depths ranging from 10 to 100 meters, suitable for ambush predation near the seafloor. Bone microstructure analyses, including vascularization patterns in limb elements, support these neritic preferences, showing adaptations for sustained activity in shallow, well-oxygenated waters rather than deep oceanic basins, as evidenced by the prevalence of fibrolamellar bone indicative of rapid growth in stable coastal habitats. Plesiosauroids coexisted sympatrically with ichthyosaurs and pliosaurs in Jurassic seaways like the and formations, where niche partitioning minimized direct competition for fish prey through differences in mechanics and strategies. Long-necked plesiosauroids exhibited slow jaw-opening kinetics and high tooth implantation indices, enabling segregation into niches targeting soft-bodied or schooling fish in mid-water columns, while short-necked pliosaurs focused on larger, tougher prey via powerful bites, reducing overlap with ichthyosaurs that pursued fast-swimming cephalopods and small fish. This interspecies dynamic is illustrated by isotopic and taphonomic data from shared assemblages, suggesting plesiosauroids occupied benthic to epipelagic zones, potentially displacing ichthyosaurs toward deeper or pelagic realms during peak diversification in the . Stable oxygen analyses of plesiosauroid and associated marine carbonates reveal tolerance for water temperatures from temperate (around 15–20°C) to subtropical (25–30°C) regimes, with body temperatures maintained at 27–35°C via poikilothermic endothermy, allowing habitation across latitudinal gradients in seaways like the . Evidence of seasonal migration is inferred from intra-tooth δ¹⁸O gradients in specimens from the , indicating shifts between coastal subtropical breeding grounds and temperate shelf foraging areas to track prey availability. As apex and mid-level predators, plesiosauroids played a pivotal paleoecological role in marine ecosystems, exerting top-down control on populations by preying on abundant schooling like teleosts, thereby stabilizing community structures in epicontinental seas and preventing of lower trophic levels. Their presence in diverse assemblages, from the to the , underscores their function as keystone regulators, with short-necked forms like polycotylids acting as burst predators on herring-like , fostering in shelf ecosystems comparable to modern orca-mediated marine balances.

References

  1. https://www.cambridge.org/core/services/aop-cambridge-core/content/view/8A68F79F7BCF0D56D2D7435D3A018704/S0094837300017395a.pdf/evolution_of_plesiosaur_and_pliosaur_morphotypes_in_the_plesiosauria_reptilia_sauropterygia.pdf
  2. https://mds.marshall.edu/cgi/viewcontent.cgi?article=1051&context=bio_sciences_faculty
  3. https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2024.1341470/full
  4. https://fr.pensoft.net/article/97686/
  5. https://plesiosauria.com/pdf/welles_1943_elasmosaurid_plesiosaurs.pdf
  6. https://paleoarchive.com/literature/Persson1963-RevisionClassificationPlesiosauria.pdf
  7. https://onlinelibrary.wiley.com/doi/10.1111/j.1469-185X.2009.00107.x
  8. https://www.researchgate.net/publication/40663923_The_taxonomic_and_phylogenetic_position_of_the_Plesiosauroidea_from_the_Lower_Jurassic_Posidonia_Shale_of_southwest_Germany
  9. https://royalsocietypublishing.org/doi/10.1098/rsos.172177
  10. https://www.sciencedirect.com/science/article/abs/pii/S0195667123003403
  11. https://doi.org/10.1371/journal.pone.0031838
  12. https://doi.org/10.1111/j.1469-185X.2009.00107.x
  13. https://doi.org/10.1080/02724630109342770
  14. https://doi.org/10.11646/zootaxa.1863.1.1
  15. https://doi.org/10.1098/rsos.172177
  16. https://doi.org/10.7717/peerj.19665
  17. https://doi.org/10.3389/feart.2024.1341470
  18. https://www.sciencedirect.com/science/article/pii/S0960982223004669
  19. https://pmc.ncbi.nlm.nih.gov/articles/PMC5729018/
  20. https://pmc.ncbi.nlm.nih.gov/articles/PMC3733804/
  21. http://palaeos.com/vertebrates/sauropterygia/plesiosauroidea.html
  22. https://doi.org/10.1016/j.cub.2025.01.001
  23. https://doi.org/10.1016/j.cub.2023.04.018
  24. https://pmc.ncbi.nlm.nih.gov/articles/PMC7120097/
  25. https://www.researchgate.net/publication/285278103_Faunas_behavior_and_evolution
  26. https://doi.org/10.4202/app.00334.2016
  27. https://pmc.ncbi.nlm.nih.gov/articles/PMC6842296/
  28. https://doi.org/10.1016/j.cub.2017.10.069
  29. https://doi.org/10.1080/02724634.2019.1595636
  30. https://www.researchgate.net/publication/227540334_Ecomorphology_of_plesiosaur_flipper_geometry
  31. https://pmc.ncbi.nlm.nih.gov/articles/PMC8684327/
  32. https://journals.plos.org/ploscompbiol/article?id=10.1371/journal.pcbi.1004605
  33. https://pmc.ncbi.nlm.nih.gov/articles/PMC5577481/
  34. https://pmc.ncbi.nlm.nih.gov/articles/PMC11373562/
  35. https://pterosaurheresies.wordpress.com/2020/10/29/svp-abstracts-27-plesiosaur-breathing/
  36. https://doi.org/10.1098/rspb.2017.0951
  37. https://evolution-outreach.biomedcentral.com/articles/10.1007/s12052-009-0139-y
  38. https://pmc.ncbi.nlm.nih.gov/articles/PMC3306369/
  39. https://www.science.org/doi/10.1126/sciadv.1701144
  40. https://www.researchgate.net/publication/233481849_Cranial_anatomy_of_a_new_plesiosaur_genus_from_the_Lowermost_Lias_RhaetianHettangian_of_Street_Somerset_England
  41. https://bmcecolevol.biomedcentral.com/articles/10.1186/s12862-023-02150-w
  42. https://www.newscientist.com/article/2156370-this-is-the-oldest-fossil-of-a-plesiosaur-from-the-dinosaur-era/
  43. https://peerj.com/articles/19665/
  44. https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.25620
  45. https://www.researchgate.net/publication/389208223_The_osteology_taxonomy_and_phylogenetic_placement_of_Seeleyosaurus_guilelmiimperatoris_Plesiosauroidea_Microcleididae_from_the_Lower_Jurassic_Posidonia_Shale_of_Germany
  46. https://www.tandfonline.com/doi/full/10.1080/02724634.2025.2505520
  47. https://pmc.ncbi.nlm.nih.gov/articles/PMC10351514/
  48. https://www.sciencedirect.com/science/article/abs/pii/S0016699502000190
  49. https://www.cell.com/current-biology/fulltext/S0960-9822(23)00466-9
  50. https://www.tandfonline.com/doi/abs/10.1080/02724634.2017.1301945
  51. https://www.sciencedirect.com/science/article/abs/pii/S0195667116302403
  52. https://www.researchgate.net/publication/40662466_The_evolution_of_plesiosaur_and_pliosaur_morphotypes_in_the_Plesiosauria_Reptilia_Sauropterygia
  53. https://pmc.ncbi.nlm.nih.gov/articles/PMC11285779/
  54. https://www.app.pan.pl/archive/published/app62/app003342016.pdf
  55. https://pmc.ncbi.nlm.nih.gov/articles/PMC7164395/
  56. https://www.nature.com/articles/s41598-020-61089-w
  57. http://www.paleo.cc/paluxy/plesios.htm
  58. https://www.nhm.ac.uk/discover/mary-anning-unsung-hero.html
  59. https://www.geolsoc.org.uk/the-library/online-exhibitions/mary-anning-and-the-geological-society/reconstruction-of-life/plesiosaurus-dolichodeirus/
  60. https://digitalcommons.csbsju.edu/cgi/viewcontent.cgi?article=1024&context=headwaters
  61. http://oceansofkansas.com/tale-tail.html
  62. https://bioone.org/journals/proceedings-of-the-academy-of-natural-sciences-of-philadelphia/volume-152/issue-1/0097-3157_2002_152_0215_HPOVBM_2.0.CO_2/Bonehead-mistakes--The-background-in-scientific-literature-and-illustrations/10.1635/0097-3157%282002%29152%255B0215:HPOVBM%255D2.0.CO%3B2.short
  63. https://www.researchgate.net/publication/319116980_The_completeness_of_the_fossil_record_of_plesiosaurs_marine_reptiles_from_the_Mesozoic
  64. https://ucmp.berkeley.edu/mesozoic/jurassic/solnhofen.html
  65. https://doc.rero.ch/record/15100/files/PAL_E2367.pdf
  66. https://www.tandfonline.com/doi/abs/10.1080/14772019.2023.2242846
  67. https://data.nhm.ac.uk/object/35641294-c471-4e37-bcc8-4c125c03713e
  68. https://www.sciencedirect.com/science/article/abs/pii/S0195667118302003
  69. https://www.researchgate.net/publication/254315131_Albertonectes_vanderveldei_a_New_Elasmosaur_Reptilia_Sauropterygia_from_the_Upper_Cretaceous_of_Alberta
  70. https://www.sci.news/paleontology/plesiopterys-wildi-13787.html
  71. https://www.abc.net.au/news/2024-02-16/plesiosaur-fossil-museum-queensland-discovery-rare-reptile-xray/103466686
  72. https://royalsocietypublishing.org/doi/10.1098/rsos.172307
  73. https://pmc.ncbi.nlm.nih.gov/articles/PMC5994164/
  74. https://palaeo-electronica.org/content/2013/418-plesiosaur-mastication
  75. https://academic.oup.com/evolut/article/71/5/1164/6881988
  76. https://www.sciencedaily.com/releases/2025/02/250207122619.htm
  77. https://pubmed.ncbi.nlm.nih.gov/16210529/
  78. https://www.tandfonline.com/doi/full/10.1080/03115518.2023.2194944
  79. https://pubs.geoscienceworld.org/gsa/books/edited-volume/579/chapter/3803526/Comparison-of-gastroliths-within-plesiosaurs
  80. https://pubmed.ncbi.nlm.nih.gov/17933571/
  81. https://www.researchgate.net/publication/5910913_Elasmosaur_Reptilia_Sauropterygia_neck_flexibility_Implications_for_feeding_strategies
  82. https://rivp-paludicola.org/wp-content/uploads/2018/05/9-1-wahl-2012.pdf
  83. https://pubs.geoscienceworld.org/paleosoc/jpaleontol/article/74/5/907/83247/AN-EARLY-POLYCOTYLID-PLESIOSAUR-REPTILIA
  84. https://www.nature.com/articles/s41598-023-43015-y
  85. https://www.science.org/doi/10.1126/science.1205689
  86. https://www.researchgate.net/publication/274835037_Evolution_of_viviparous_reproduction_in_Paleozoic_and_Mesozoic_reptiles
  87. https://www.researchgate.net/publication/324757654_Growth_patterns_sexual_dimorphism_and_maturation_modeled_in_Pachypleurosauria_from_Middle_Triassic_of_central_Europe_Diapsida_Sauropterygia
  88. https://onlinelibrary.wiley.com/doi/10.1111/joa.14273
  89. https://doi.org/10.1098/rsos.231951
Add your contribution
Related Hubs
User Avatar
No comments yet.