Terminonatator
Encyclopedia
Terminonatator is a genus
of elasmosaurid
plesiosaur
from the Late Cretaceous
of Saskatchewan
, Canada
. It is known from a skull and partial skeleton from a young adult, found in the Campanian
-age Bearpaw Formation
near Notukeu Creek in Ponteix. Terminonatator is currently one of the youngest plesiosaurs from the Western Interior Seaway
.
RSM
P2414.1, a skull and partially articulated incomplete skeleton found high in the Bearpaw Formation. Tamaki Sato, who named and described the specimen in 2003
, used the genus name to emphasize its lateness in the fossil record, and the species
epithet ponteixensis for Ponteix. Only one species has been described: the type species
T. ponteixensis.
RSM P2414.1 appears to represent an adult, because the neural arches
are fused to their vertebrae, although incomplete fusion elsewhere indicates it was a young adult. It would have been small as an adult for an elasmosaurid, at only about 7 meters long (23 ft), up to 9 meters (30 ft) if it had an extremely long neck like Elasmosaurus
(which had 72 neck vertebrae).
The skull as preserved is 26.8 centimeters long (10.6 in), but is broken near the posterior
end. Compared to other elasmosaurids, the snout was relatively short. Unlike other plesiosaurs, the pineal foramen in the roof of the skull was closed, and there were only nine teeth in the premaxilla
ry bones that form the tip of the snout instead of ten, although this could be individual variation. The right jaw is better preserved than the left; at least 13 teeth were present in the right maxilla
(the main tooth-bearing bone of the upper jaw), and 17 to 18 teeth were present in the right dentary, which held teeth in lower jaw. There was an unusually tall bony process
on the coronoid, a bone of the lower jaw. Impressions of part of the brain
and other cranial nervous tissue were found in the braincase.
The backbone is incomplete, but 51 neck, 17 back, four sacral
, and 12 tail vertebrae were preserved. Over 150 pebbles, representing gastrolith
s, were found within the rib cage; the largest has a diameter of 6 centimeters (2 in). The shoulder and pelvic girdle are fragmentary. The thigh bone
was longer than the upper arm
, which is unusual for an elasmosaurid, and the right thigh bone was broken and healed.
Terminonatator is significant because of its late age, its inclusion of a skull with most of a skeleton, and its nature as an elasmosaurid (the remains of short-necked plesiosaurs are more common in comparable rocks in Canada). The remains of comparable elasmosaurids are poorly preserved, and/or have poorly described skulls, making comparisons of this genus to other elasmosaurids difficult at this time.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of elasmosaurid
Elasmosauridae
Elasmosauridae was the family of plesiosaurs. They had the longest necks of the plesiosaurs and survived from the Late Triassic to the end of the Cretaceous. They had a diet of fish and shelless cephalopods.-Size:...
plesiosaur
Plesiosaur
Plesiosauroidea is an extinct clade of carnivorous plesiosaur marine reptiles. Plesiosauroids, are known from the Jurassic and Cretaceous Periods...
from the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
of Saskatchewan
Saskatchewan
Saskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota....
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
. It is known from a skull and partial skeleton from a young adult, found in the Campanian
Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...
-age Bearpaw Formation
Bearpaw Formation
The Bearpaw Formation, also called the Bearpaw Shale, is a sedimentary rock formation found in northwestern North America. It is exposed in the U.S. state of Montana, as well as the Canadian provinces of Alberta and Saskatchewan, east of the Rocky Mountains...
near Notukeu Creek in Ponteix. Terminonatator is currently one of the youngest plesiosaurs from the Western Interior Seaway
Western Interior Seaway
The Western Interior Seaway, also called the Cretaceous Seaway, the Niobraran Sea, and the North American Inland Sea, was a huge inland sea that split the continent of North America into two halves, Laramidia and Appalachia, during most of the mid- and late-Cretaceous Period...
.
Description
Terminonatator is based onHolotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
RSM
Royal Saskatchewan Museum
The Royal Saskatchewan Museum was established in Regina as the Provincial Museum in 1906 to "secure and preserve natural history specimens and objects of historical and ethnological interest." It was the first museum in Saskatchewan, Canada, and the first provincial museum in the three Prairie...
P2414.1, a skull and partially articulated incomplete skeleton found high in the Bearpaw Formation. Tamaki Sato, who named and described the specimen in 2003
2003 in paleontology
-New taxa:-Newly named dinosaurs:Data courtesy of George Olshevsky's dinosaur genera list and Dr. Jeremy Montague's dinosaur genus database.-New taxa:-New taxa:-Non-mammalian:-newly named:-Conifers:-Angiosperms:...
, used the genus name to emphasize its lateness in the fossil record, and the species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
epithet ponteixensis for Ponteix. Only one species has been described: the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
T. ponteixensis.
RSM P2414.1 appears to represent an adult, because the neural arches
Vertebral arch
The vertebral arch is the posterior part of a vertebra.It consists of a pair of pedicles and a pair of laminae, and supports seven processes:* four articular processes* two transverse processes* one spinous process...
are fused to their vertebrae, although incomplete fusion elsewhere indicates it was a young adult. It would have been small as an adult for an elasmosaurid, at only about 7 meters long (23 ft), up to 9 meters (30 ft) if it had an extremely long neck like Elasmosaurus
Elasmosaurus
Elasmosaurus + σαυρος sauros 'lizard') is a genus of plesiosaur with an extremely long neck that lived in the Late Cretaceous period , 80.5 million years ago.-Description:...
(which had 72 neck vertebrae).
The skull as preserved is 26.8 centimeters long (10.6 in), but is broken near the posterior
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
end. Compared to other elasmosaurids, the snout was relatively short. Unlike other plesiosaurs, the pineal foramen in the roof of the skull was closed, and there were only nine teeth in the premaxilla
Premaxilla
The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
ry bones that form the tip of the snout instead of ten, although this could be individual variation. The right jaw is better preserved than the left; at least 13 teeth were present in the right maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
(the main tooth-bearing bone of the upper jaw), and 17 to 18 teeth were present in the right dentary, which held teeth in lower jaw. There was an unusually tall bony process
Process (anatomy)
In anatomy, a process is a projection or outgrowth of tissue from a larger body. The vertebra has several kinds of processes,such as: transverse process, prezygapophysis, postzygapophysis.-Examples:Examples of processes include:...
on the coronoid, a bone of the lower jaw. Impressions of part of the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
and other cranial nervous tissue were found in the braincase.
The backbone is incomplete, but 51 neck, 17 back, four sacral
Sacrum
In vertebrate anatomy the sacrum is a large, triangular bone at the base of the spine and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two hip bones. Its upper part connects with the last lumbar vertebra, and bottom part with the coccyx...
, and 12 tail vertebrae were preserved. Over 150 pebbles, representing gastrolith
Gastrolith
A gastrolith, also called a stomach stone or gizzard stones, is a rock held inside a gastrointestinal tract. Gastroliths are retained in the muscular gizzard and used to grind food in animals lacking suitable grinding teeth. The grain size depends upon the size of the animal and the gastrolith's...
s, were found within the rib cage; the largest has a diameter of 6 centimeters (2 in). The shoulder and pelvic girdle are fragmentary. The thigh bone
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
was longer than the upper arm
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
, which is unusual for an elasmosaurid, and the right thigh bone was broken and healed.
Terminonatator is significant because of its late age, its inclusion of a skull with most of a skeleton, and its nature as an elasmosaurid (the remains of short-necked plesiosaurs are more common in comparable rocks in Canada). The remains of comparable elasmosaurids are poorly preserved, and/or have poorly described skulls, making comparisons of this genus to other elasmosaurids difficult at this time.