''Plesiosaurus'' (Greek: ' ('), near to + ' ('), lizard) is a genus of extinct, large marine
sauropterygia
Sauropterygia ("lizard flippers") is an extinct taxon of diverse, aquatic reptiles that developed from terrestrial ancestors soon after the end-Permian extinction and flourished during the Triassic before all except for the Plesiosauria became ...
n
reptile
Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...
that lived during the
Early Jurassic
The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-J ...
. It is known by nearly complete skeletons from the
Lias
Lias may refer to:
Geology
* Lias Formation, a geologic formation in France
*Lias Group, a lithostratigraphic unit in western Europe
* Early Jurassic, an epoch
People
* Godfrey Lias, British author
* Mohd Shamsudin Lias (born 1953), Malaysian ...
of England. It is distinguishable by its small head, long and slender neck, broad turtle-like body, a short tail, and two pairs of large, elongated paddles. It lends its name to the order
Plesiosauria
The Plesiosauria (; Greek: πλησίος, ''plesios'', meaning "near to" and ''sauros'', meaning "lizard") or plesiosaurs are an order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia.
Plesiosaurs first appeare ...
, of which it is an early, but fairly typical member. It contains only one species, the
type, ''Plesiosaurus dolichodeirus''. Other species once assigned to this genus, including ''P. brachypterygius'', ''P. guilielmiimperatoris'', and ''P. tournemirensis'' have been reassigned to new genera, such as ''
Hydrorion
''Hydrorion'' (meaning 'water hunter') is a genus of plesiosaur from the Toarcian Age of the Lower Jurassic. It is only known from multiple specimens, all discovered in the Posidonia Shale of southwestern Germany. The only species of ''Hydrori ...
'', ''
Seeleyosaurus
''Seeleyosaurus'' is an extinct genus of plesiosaur that was initially placed within the genus ''Plesiosaurus'' in 1895Dames, H. W. (1895). Die Plesiosaurier der süddeutschen Liasformation. ''Abhandlungen der Königlichen Akademie der Wissenscha ...
'' and ''
Occitanosaurus
''Microcleidus'' is an extinct genus of sauropterygian reptile belonging to the Plesiosauroidea. The species has 40 neck vertebrae and a short tail of 28 vertebrae. Fossils of the genus have been found in France, the Posidonia Shale in Germany an ...
''.
Discovery
The first complete skeleton of ''Plesiosaurus'' was discovered by early paleontologist and fossil hunter
Mary Anning
Mary Anning (21 May 1799 – 9 March 1847) was an English fossil collector, dealer, and palaeontologist who became known around the world for the discoveries she made in Jurassic marine fossil beds in the cliffs along the English Channel ...
in
Sinemurian
In the geologic timescale, the Sinemurian is an age and stage in the Early or Lower Jurassic Epoch or Series. It spans the time between 199.3 ± 2 Ma and 190.8 ± 1.5 Ma (million years ago). The Sinemurian is preceded by the Hettangian and is ...
(
Early Jurassic
The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-J ...
)-age rocks of the lower
Lias Group
The Lias Group or Lias is a lithostratigraphic unit (a sequence of rock strata) found in a large area of western Europe, including the British Isles, the North Sea, the Low Countries and the north of Germany. It consists of marine limestones, sh ...
in December 1823.
[Storrs 1997 pp. 146] Additional fossils of ''Plesiosaurus'' were found in rocks of the Lias Group of Dorset for many years, "until the cessation of quarrying activities in the Lias Group, early in this
0th
0th or zeroth may refer to:
Mathematics, science and technology
* 0th or zeroth, an ordinal for the number zero
* 0th dimension, a topological space
* 0th element, of a data structure in computer science
* Zeroth (software), deep learning softwar ...
century."
[ although less complete remains were used by ]Henry De la Beche
Sir Henry Thomas De la Beche KCB, FRS (10 February 179613 April 1855) was an English geologist and palaeontologist, the first director of the Geological Survey of Great Britain, who helped pioneer early geological survey methods. He was the f ...
and William Conybeare to name the species two years earlier in 1821,[De la Beche, H. T. & W. D. Conybeare. (1821). Notice of the discovery of a new fossil animal, forming a link between the '']Ichthyosaurus
''Ichthyosaurus'' (derived from Greek ' () meaning 'fish' and ' () meaning 'lizard') is a genus of ichthyosaurs from the Early Jurassic ( Hettangian - Pliensbachian), with possible Late Triassic record, from Europe (Belgium, England, Germany, S ...
'' and crocodile
Crocodiles (family (biology), family Crocodylidae) or true crocodiles are large semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term crocodile is sometimes used even more loosely to inclu ...
, together with general remarks on the osteology of the ''Ichthyosaurus''. ''Transactions of the Geological Society of London'' 5: 559–594 and despite being discovered first, Conybeare's remains were not the holotype; Anning's were.
''Plesiosaurus'' was one of the first of the "antediluvian
The antediluvian (alternatively pre-diluvian or pre-flood) period is the time period chronicled in the Bible between the fall of man and the Genesis flood narrative in biblical cosmology. The term was coined by Thomas Browne. The narrative take ...
reptiles" to be discovered and excited great interest in 19th-century England. It was so-named ("near lizard") by William Conybeare and Henry De la Beche
Sir Henry Thomas De la Beche KCB, FRS (10 February 179613 April 1855) was an English geologist and palaeontologist, the first director of the Geological Survey of Great Britain, who helped pioneer early geological survey methods. He was the f ...
, to indicate that it was more like a normal reptile than ''Ichthyosaurus
''Ichthyosaurus'' (derived from Greek ' () meaning 'fish' and ' () meaning 'lizard') is a genus of ichthyosaurs from the Early Jurassic ( Hettangian - Pliensbachian), with possible Late Triassic record, from Europe (Belgium, England, Germany, S ...
'', which had been found in the same rock strata just a few years earlier. ''Plesiosaurus'' is the archetypical genus of Plesiosauria and the first to be described, hence lending its name to the order. Conybeare and De la Beche coined the name for scattered finds from the Bristol region, Dorset
Dorset ( ; archaically: Dorsetshire , ) is a county in South West England on the English Channel coast. The ceremonial county comprises the unitary authority areas of Bournemouth, Christchurch and Poole and Dorset (unitary authority), Dors ...
, and Lyme Regis
Lyme Regis is a town in west Dorset, England, west of Dorchester and east of Exeter. Sometimes dubbed the "Pearl of Dorset", it lies by the English Channel at the Dorset–Devon border. It has noted fossils in cliffs and beaches on the Herita ...
in 1821. The type species
In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...
of ''Plesiosaurus'', ''P. dolichodeirus'', was named and described by Conybeare in 1824 on the basis of Anning's original finds.
Description
Skull and dentition
Compared to other plesiosaur genera, ''Plesiosaurus'' has a small head. The skull is much narrower than long,[Storrs 1997 pp. 166] reaching its greatest width just behind the eyes (the postorbital
The ''postorbital'' is one of the bones in vertebrate skulls which forms a portion of the dermal skull roof and, sometimes, a ring about the orbit. Generally, it is located behind the postfrontal and posteriorly to the orbital fenestra. In some ve ...
bar).[Storrs 1997 pp. 165] The anterior
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...
portion is "bluntly triangular".[ In lateral view, the skull reaches its highest point at the rear of the ]skull table
The skull roof, or the roofing bones of the skull, are a set of bones covering the brain, eyes and nostrils in bony fishes and all land-living vertebrates. The bones are derived from dermal bone and are part of the dermatocranium.
In comparati ...
.[Storrs 1997 pp. 167] "The external nostrils overlie the internal nares".[ They are not positioned at the tip of the snout, but farther back, nearer the eyes than the tip of the skull.][ Unlike the nostrils of '']Rhomaleosaurus
''Rhomaleosaurus'' (meaning "strong lizard") is an extinct genus of Early Jurassic (Toarcian age, about 183 to 175.6 million years ago) rhomaleosaurid pliosauroid known from Northamptonshire and from Yorkshire of the United Kingdom. It was first ...
'', they do not appear to be adapted for underwater olfaction.[ The ]orbits
In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as a p ...
(eye sockets) are roughly circular and are positioned about halfway along the length of the skull.[ They face up and to the sides.][ Just posterior to the orbits are the ]supratemporal fenestra
The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...
e, which are about the same size as the orbits and also roughly circular.[ Between the four openings is the ]pineal foramen
A parietal eye, also known as a third eye or pineal eye, is a part of the epithalamus present in some vertebrates. The eye is located at the top of the head, is photoreceptive and is associated with the pineal gland, regulating circadian rhythm ...
, and between the temporal fenestrae is a narrow sagittal ridge.[ As in other plesiosaurs, the ]pterygoid Pterygoid, from the Greek for 'winglike', may refer to:
* Pterygoid bone, a bone of the palate of many vertebrates
* Pterygoid processes of the sphenoid bone
** Lateral pterygoid plate
** Medial pterygoid plate
* Lateral pterygoid muscle
* Medial ...
s of the palate are fused to the basioccipital
The basilar part of the occipital bone (also basioccipital) extends forward and upward from the foramen magnum, and presents in front an area more or less quadrilateral in outline.
In the young skull this area is rough and uneven, and is joined t ...
of the braincase
In human anatomy, the neurocranium, also known as the braincase, brainpan, or brain-pan is the upper and back part of the skull, which forms a protective case around the brain. In the human skull, the neurocranium includes the calvaria or skul ...
,[ although the union is not as robust as in the pliosaurs ''Rhomaleosaurus'' and '']Pliosaurus
''Pliosaurus'' (meaning 'more lizard') is an extinct genus of thalassophonean pliosaurid known from the Kimmeridgian and Tithonian stages (Late Jurassic) of Europe and South America. Their diet would have included fish, cephalopods, and marine re ...
''.[ "The palatal bones are thin, but there is no suborbital fenestra."][
The two rami of the lower jaw make a "V" shape with an angle of about 45°.][ The specialized region where they meet, the ]symphysis
A symphysis (, pl. symphyses) is a fibrocartilaginous fusion between two bones. It is a type of cartilaginous joint, specifically a secondary cartilaginous joint.
# A symphysis is an amphiarthrosis, a slightly movable joint.
# A growing together ...
, is robust. The two rami are fused at the symphysis, making a pointed, shallow scoop-like shape.[Storrs 1997 pp. 169.]
The teeth of ''Plesiosaurus'' are "simple, needle-like cones" that are "slightly curved and circular in transverse section". They are sharply pointed with fine striations running from tip to base, and point forward (procumbent). This procumbency becomes more pronounced near the leading end of the skull, where they may be only 10–15° above horizontal.[ There are 20 to 25 teeth per upper jaw tooth row,][ and 24 per low jaw tooth row.][ Up to four teeth of a lower jaw's tooth row are found in the symphyseal region.][
]
Vertebral column
''Plesiosaurus'' was a moderately sized plesiosaur that grew to in length and in body mass.[Storrs 1997 pp. 149] There are approximately 40 cervical vertebrae
In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In ...
(neck vertebrae), with different specimens preserving 38 to 42 cervical vertebrae.[Storrs 1997 pp. 170] Of the rest of the vertebral column, there are a handful (four or five in the holotype
A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...
specimen) of "pectoral" vertebrae from the neck-torso transition,[ approximately 21 dorsal or back vertebrae, three or more ]sacral vertebrae
The sacrum (plural: ''sacra'' or ''sacrums''), in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30.
The sacrum situates at the upper, back part ...
, and at least 28 caudal vertebra
The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic i ...
e.[Storrs 1997 pp. 171] Generally, the centra
Centra is a convenience shop chain that operates throughout Ireland. The chain operates as a symbol group owned by Musgrave Group, the food wholesaler, meaning the stores are all owned by individual franchisees.
The chain has three different f ...
of the cervical vertebrae are relatively elongated, being slightly longer than tall. The width, however, is usually greater than or equal to the length. The articular surfaces of the cervical centra are "slightly concave and kidney-shaped, with rounded, slightly rugose edges." Small holes called foramina subcentralia are found on the ventral surface of the centra. Some of the dorsals have rugose articular edges, like the cervicals; this feature is typically absent from the caudals.[
Ribs are found from the neck to the tail. Cervical ribs are hatchet-shaped and have two articular heads.][ Dorsal ribs are thick and have only one head. Sacral ribs are "short, robust, and blunt or knob-like on both ends." Caudal ribs have different morphologies depending on their location along the tail, with anterior examples being pointed and more distal examples being "broad and blunt."][Storrs 1997 pp. 170] ''Plesiosaurus'' also has gastralia
Gastralia (singular gastralium) are dermal bones found in the ventral body wall of modern crocodilians and tuatara, and many prehistoric tetrapods. They are found between the sternum and pelvis, and do not articulate with the vertebrae. In these ...
, also known as "belly ribs." Nine or more sets of gastralia are present between the shoulder
The human shoulder is made up of three bones: the clavicle (collarbone), the scapula (shoulder blade), and the humerus (upper arm bone) as well as associated muscles, ligaments and tendons. The articulations between the bones of the shoulder mak ...
and pelvis
The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis, or pelvic skeleton).
The ...
. Each set is composed of seven elements: a bone on the midline flanked by three lateral elements.[
]
Limbs
The shoulder girdle is only partly known but appears to be typical for plesiosaurs. It includes fused clavicle
The clavicle, or collarbone, is a slender, S-shaped long bone approximately 6 inches (15 cm) long that serves as a strut between the shoulder blade and the sternum (breastbone). There are two clavicles, one on the left and one on the rig ...
s at the anterior end, scapula
The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eithe ...
e (shoulder blades), and large coracoid
A coracoid (from Greek κόραξ, ''koraks'', raven) is a paired bone which is part of the shoulder assembly in all vertebrates except therian mammals (marsupials and placentals). In therian mammals (including humans), a coracoid process is prese ...
s. The scapulae and coracoids both contribute to the glenoids (arm sockets). A pair of oval holes called pectoral fenestrae are found midway along the scapular/coracoid contacts.[ The forelimbs are elongate and relatively narrow compared to those of most plesiosaurs. The ]humerus
The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...
(upper arm bone) has distinctive curvature, which appears to be a retained primitive feature among sauropterygia
Sauropterygia ("lizard flippers") is an extinct taxon of diverse, aquatic reptiles that developed from terrestrial ancestors soon after the end-Permian extinction and flourished during the Triassic before all except for the Plesiosauria became ...
ns. Mature ''Plesiosaurus'' also have a distinctive groove along the ventral surface of the humerus. The forearm includes a flat, broad, crescent-shaped ulna
The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...
and a "robust and pillar-like" radius
In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...
. The wrist includes six bones.[Storrs 1997 pp. 173] The hand paddle has five digits; the phalangeal formula
The phalanges (singular: ''phalanx'' ) are digital bones in the hands and feet of most vertebrates. In primates, the thumbs and big toes have two phalanges while the other digits have three phalanges. The phalanges are classed as long bones.
...
is uncertain, but the count for one large individual, from "thumb
The thumb is the first digit of the hand, next to the index finger. When a person is standing in the medical anatomical position (where the palm is facing to the front), the thumb is the outermost digit. The Medical Latin English noun for thumb ...
" to fifth "finger", is 4-8-9-8-6.[Storrs 1997 pp. 176]
The pelvis includes equant pubic bones
In vertebrates, the pubic region ( la, pubis) is the most forward-facing (ventral and anterior) of the three main regions making up the coxal bone. The left and right pubic regions are each made up of three sections, a superior ramus, inferior r ...
, ischia
Ischia ( , , ) is a volcanic island in the Tyrrhenian Sea. It lies at the northern end of the Gulf of Naples, about from Naples. It is the largest of the Phlegrean Islands. Roughly trapezoidal in shape, it measures approximately east to west ...
,[ and blade-shaped ilia connecting the pelvis to the vertebral column.][Storrs 1997 pp. 178] The acetabulum
The acetabulum (), also called the cotyloid cavity, is a concave surface of the pelvis. The head of the femur meets with the pelvis at the acetabulum, forming the hip joint.
Structure
There are three bones of the ''os coxae'' (hip bone) that c ...
is formed by surfaces on the pubic bones and ischia. Similar to the pectoral girdle, there is a pair of holes between the ischia and pubic bones.[ The hindlimbs are long and narrow,][ and in adults, they are much smaller than the forelimbs.][ The thigh bones are straight. The lower hindlimb includes two roughly equal-sized bones, the robust ]tibia
The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...
and the semilunate-shaped fibula
The fibula or calf bone is a leg bone on the lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones. Its upper extremity is ...
. There are six bones in the ankle. The foot paddle includes five digits. Like the hand, the phalangeal formula is uncertain, but is at least 3-7-9-8-7 from innermost to outer "toe".[
]
Classifications
''Plesiosaurus'' has historically been a wastebasket taxon
Wastebasket taxon (also called a wastebin taxon, dustbin taxon or catch-all taxon) is a term used by some taxonomists to refer to a taxon that has the sole purpose of classifying organisms that do not fit anywhere else. They are typically defined ...
. This is due in part to few anatomical or taxonomic studies of the relevant fossils. Uncritical taxonomic work resulted in hundreds of species representing most of the world and most of the Mesozoic being assigned to ''Plesiosaurus.'' None of the younger Jurassic
The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...
or Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...
species belong to ''Plesiosaurus''. Review of the Early Jurassic species indicates that the only English species properly assigned to ''Plesiosaurus'' is ''P. dolichodeirus''.[ Several other European Early Jurassic species have been assigned to new genera. ''P. brachypterygius'', ''P. guilielmiimperatoris'' and ''P. tournemirensis'', for example, were assigned to the new genera '']Hydrorion
''Hydrorion'' (meaning 'water hunter') is a genus of plesiosaur from the Toarcian Age of the Lower Jurassic. It is only known from multiple specimens, all discovered in the Posidonia Shale of southwestern Germany. The only species of ''Hydrori ...
'', ''Seeleyosaurus
''Seeleyosaurus'' is an extinct genus of plesiosaur that was initially placed within the genus ''Plesiosaurus'' in 1895Dames, H. W. (1895). Die Plesiosaurier der süddeutschen Liasformation. ''Abhandlungen der Königlichen Akademie der Wissenscha ...
'' and ''Occitanosaurus
''Microcleidus'' is an extinct genus of sauropterygian reptile belonging to the Plesiosauroidea. The species has 40 neck vertebrae and a short tail of 28 vertebrae. Fossils of the genus have been found in France, the Posidonia Shale in Germany an ...
''.
The following cladogram
A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...
follows an analysis by Benson ''et al.'', 2012, and shows the placement of ''Plesiosaurus'' within Plesiosauria.
Stratigraphy
Unequivocal specimens of ''Plesiosaurus dolichodeirus'' are limited to the Lyme Regis area of Dorset. It appears to be the most common species of plesiosaur in the Lias Group of England. ''Plesiosaurus'' is best represented from the "upper part of the Blue Lias
The Blue Lias is a geological formation in southern, eastern and western England and parts of South Wales, part of the Lias Group. The Blue Lias consists of a sequence of limestone and shale layers, laid down in latest Triassic and early Jurassi ...
, the 'Shales with Beef,' and the lower Black Ven Marls" the latter of which form part of the Charmouth Mudstone
The Charmouth Mudstone Formation is a geological formation in England. It preserves fossils dating back to the early part of the Jurassic period (Sinemurian–Pliensbachian). It forms part of the lower Lias Group. It is most prominently exposed at ...
; using the Lias Group ammonite
Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) ...
fossil zones, these rocks date to the early Sinemurian
In the geologic timescale, the Sinemurian is an age and stage in the Early or Lower Jurassic Epoch or Series. It spans the time between 199.3 ± 2 Ma and 190.8 ± 1.5 Ma (million years ago). The Sinemurian is preceded by the Hettangian and is ...
stage. Some other ''Plesiosaurus'' fossils are from later Sinemurian rocks. The oldest specimen may be a skull thought to come from late Rhaetian
The Rhaetian is the latest age of the Triassic Period (in geochronology) or the uppermost stage of the Triassic System (in chronostratigraphy). It was preceded by the Norian and succeeded by the Hettangian (the lowermost stage or earliest age ...
or early Hettangian
The Hettangian is the earliest age and lowest stage of the Jurassic
The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (My ...
rocks.[Storrs 1997 pp.180]
Paleoecology
''Plesiosaurus'' fed mainly on clams and snails, and is thought to have eaten belemnite
Belemnitida (or the belemnite) is an extinct order of squid-like cephalopods that existed from the Late Triassic to Late Cretaceous. Unlike squid, belemnites had an internal skeleton that made up the cone. The parts are, from the arms-most to ...
s, fish and other prey as well. Its U-shaped jaw and sharp teeth would have been like a fish trap. It propelled itself by the paddles, the tail being too short to be of much use. Its neck could have been used as a rudder when navigating during a chase. ''Plesiosaurus'' gave live birth to live young in the water like sea snake
Sea snakes, or coral reef snakes, are elapid snakes that inhabit marine environments for most or all of their lives. They belong to two subfamilies, Hydrophiinae and Laticaudinae. Hydrophiinae also includes Australasian terrestrial snakes, wher ...
s. The young might have lived in estuaries
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...
before moving out into the open ocean.
It has been postulated that the long neck of ''Plesiosaurus'' would have been a hindrance when trying to speed up, any bend in the neck creating turbulences. If that is the case then ''Plesiosaurus'' would have had to keep its neck straight to achieve good acceleration, something that would make hunting difficult. For this reason it may be possible that these animals would actually lie in wait for prey to come close instead of trying to pursue them.
See also
* Timeline of plesiosaur research
This timeline of plesiosaur research is a chronologically ordered list of important fossil discoveries, controversies of interpretation, taxonomic revisions, and cultural portrayals of plesiosaurs, an order of marine reptiles that flourished duri ...
* List of plesiosaur genera
This list of plesiosaurs is a comprehensive listing of all genera that have ever been included in the order Plesiosauria, excluding purely vernacular terms. The list includes all commonly accepted genera, but also genera that are now considered inv ...
* Loch Ness Monster
The Loch Ness Monster ( gd, Uilebheist Loch Nis), affectionately known as Nessie, is a creature in Scottish folklore that is said to inhabit Loch Ness in the Scottish Highlands. It is often described as large, long-necked, and with one or mor ...
References
Notes
Sources
* Andrews, C. W. 1896. "On the structure of the plesiosaurian skull". ''Quarterly Journal of the Geological Society'', London, 52, 246–253.
* Brown, D. S. 1981. "The English Upper Jurassic Plesiosauroidea (Reptilia) and a review of the phylogeny and classification of the Plesiosauria". ''Bulletin of the British Museum (Natural History): Geology'', 35, (4), 253–347.
* Cruickshank, A. R. I.; Small, P. G.; and Taylor, M. A. 1991. "Dorsal nostrils and hydrodynamically driven underwater olfaction in plesiosaurs". ''Nature'', 352, 62–64.
*Lydekker, R. 1889. Catalogue of the fossil Reptilia and Amphibia in the British Museum (Natural History), Part II. Containing the Orders Ichthyopterygia and Sauropterygia. British Museum (Natural History)
* Richard Owen
Sir Richard Owen (20 July 1804 – 18 December 1892) was an English biologist, comparative anatomist and paleontologist. Owen is generally considered to have been an outstanding naturalist with a remarkable gift for interpreting fossils.
Owe ...
, Fossil Reptili of the Liassic Formations, pt iii. (Monogr. Palaeont. Soc., 1865)
* Persson, P. O. 1963. A revision of the classification of the Plesiosauria with a synopsis of the stratigraphical and geographical distribution of the group. Lunds Universitets Årsskrift, N. F. Avd. 2. 59, 1–59.
* Storrs, G. W. 1991. "Anatomy and relationships of ''Corosaurus alcovensis'' (Diapsida: Sauropterygia) and the Triassic Alcova Limestone of Wyoming". ''Bulletin of the Peabody Museum of Natural History'', 44, 1–151.
* Storrs, G. W. and Taylor, M. A. 1996. "Cranial anatomy of a new plesiosaur genus from the lowermost Lias (Rhaetian/Hettangian) of Street, Somerset, England". ''Journal of Vertebrate Paleontology'', 16, (3), 403–420.
* Storrs, G. W. 1997. "Morphological and taxonomic clarification of the genus ''Plesiosaurus''". 145–190. In Callaway, J. M and Nicholls, E. L. (eds.). ''Ancient Marine Reptiles''. Academic press. London.
*Taylor, M. A. and Cruickshank, A. R. I. 1993. Cranial anatomy and functional morphology of Pliosaurus brachyspondylus (Reptilia: Plesiosauria) from the Upper Jurassuc of Westbury, Wiltshire. Philosophical Transactions of the Royal Society of London, Series B, 341, 399–418.
* Torrens, Hugh 1995. "Mary Anning (1799–1847) of Lyme; 'The Greatest Fossilist the World Ever Knew'". ''The British Journal for the History of Science'', 25 (3): 257–284
External links
Genus Plesiosaurus
– The Plesiosaur Directory
– Palaeos
– Mikko's Phylogeny Archive
{{Taxonbar, from=Q857081
Early Jurassic plesiosaurs of Europe
Plesiosauroids
Fossil taxa described in 1821
Taxa named by William Conybeare
Sauropterygian genera
Taxa named by Henry De la Beche