Plateosaurus
Overview
Plateosaurus is a genus
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 plateosaurid
Plateosauridae
Plateosauridae is a family of plateosaurian sauropodomorphs. Plateosaurids were early sauropodomorph dinosaurs which existed in Asia, Europe and South America during the Late Triassic period. Although several dinosaurs have been classified as plateosaurids over the years, a 2007 study by Adam M....

 dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

 that lived during the Late Triassic
Triassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...

 period, around 216 to 199 million years ago, in what is now Central and Northern Europe. Plateosaurus is a basal (early) sauropodomorph
Sauropodomorpha
Sauropodomorpha is an extinct clade of long-necked, herbivorous, saurischian dinosaurs which includes the sauropods and their ancestral relatives. Sauropods generally grew to very large sizes, had long necks and tails, were quadrupedal, and became the largest animals to ever walk the Earth. The...

 dinosaur, a so-called "prosauropod". The latest research recognizes two 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...

: 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...

 P. engelhardti from the late Norian
Norian
The Norian is a division of the Triassic geological period. It has the rank of an age or stage . The Norian lasted from 216.5 ± 2.0 to 203.6 ± 1.5 million years ago. It was preceded by the Carnian and succeeded by the Rhaetian.-Stratigraphic definitions:The Norian was named after the Noric Alps in...

 and Rhaetian
Rhaetian
The Rhaetian is in geochronology the latest age of the Triassic period or in chronostratigraphy the uppermost stage of the Triassic system. It lasted from 203.6 ± 1.5 to 199.6 ± 0.6 million years ago...

, and the slightly earlier P. gracilis from the lower Norian.
Encyclopedia
Plateosaurus is a genus
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 plateosaurid
Plateosauridae
Plateosauridae is a family of plateosaurian sauropodomorphs. Plateosaurids were early sauropodomorph dinosaurs which existed in Asia, Europe and South America during the Late Triassic period. Although several dinosaurs have been classified as plateosaurids over the years, a 2007 study by Adam M....

 dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

 that lived during the Late Triassic
Triassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...

 period, around 216 to 199 million years ago, in what is now Central and Northern Europe. Plateosaurus is a basal (early) sauropodomorph
Sauropodomorpha
Sauropodomorpha is an extinct clade of long-necked, herbivorous, saurischian dinosaurs which includes the sauropods and their ancestral relatives. Sauropods generally grew to very large sizes, had long necks and tails, were quadrupedal, and became the largest animals to ever walk the Earth. The...

 dinosaur, a so-called "prosauropod". The latest research recognizes two 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...

: 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...

 P. engelhardti from the late Norian
Norian
The Norian is a division of the Triassic geological period. It has the rank of an age or stage . The Norian lasted from 216.5 ± 2.0 to 203.6 ± 1.5 million years ago. It was preceded by the Carnian and succeeded by the Rhaetian.-Stratigraphic definitions:The Norian was named after the Noric Alps in...

 and Rhaetian
Rhaetian
The Rhaetian is in geochronology the latest age of the Triassic period or in chronostratigraphy the uppermost stage of the Triassic system. It lasted from 203.6 ± 1.5 to 199.6 ± 0.6 million years ago...

, and the slightly earlier P. gracilis from the lower Norian. However, others have been assigned in the past, and there is no broad consensus on the species taxonomy
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...

 of plateosaurid dinosaurs. Similarly, there are a plethora of synonyms
Synonym (taxonomy)
In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...

 (invalid duplicate names) at the genus level.

Discovered in 1834 by Johann Friedrich Engelhardt and described three years later by Hermann von Meyer
Christian Erich Hermann von Meyer
Christian Erich Hermann von Meyer was a German palaeontologist.He was born at Frankfurt am Main.In 1832 von Meyer issued a work entitled Palaeologica, and in course of time he published a series of memoirs on various fossil organic remains: molluscs, crustaceans, fishes and higher vertebrata,...

, Plateosaurus was the fifth named dinosaur genus that is still considered valid today. However, it was not one of the three genera originally used by Richard Owen
Richard Owen
Sir Richard Owen, FRS KCB was an English biologist, comparative anatomist and palaeontologist.Owen is probably best remembered today for coining the word Dinosauria and for his outspoken opposition to Charles Darwin's theory of evolution by natural selection...

 in 1842 to define Dinosauria, because at the time, it was poorly known and difficult to identify as a dinosaur. It is now among the dinosaurs best known to science, with over 100 skeletons found, some of them nearly complete. It was nicknamed the Schwäbischer Lindwurm (Swabian dragon) because it was so common a fossil in south-western Germany.

Plateosaurus was a bipedal herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...

 with a small skull on a long, mobile neck, sharp but plump plant-crushing teeth, powerful hind limbs, short but muscular arms and grasping hands with large claws on three fingers, possibly used for defence and feeding. Unusually for a dinosaur, Plateosaurus showed strong developmental plasticity: instead of having a fairly uniform adult size, fully grown individuals were between 4.8 and 10 m (15.7 and 32.8 ft) long and weighed between 600 and 4000 kg (1,322.8 and 8,818.5 lb). Commonly, the animals lived for at least 12 to 20 years, but the maximum life span is not known.

Despite the great quantity and excellent quality of the fossil material, Plateosaurus was for a long time one of the most misunderstood dinosaurs. Some researchers proposed theories that were later shown to conflict with geological
Geology
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...

 and palaeontological
Paleontology
Paleontology "old, ancient", ὄν, ὀντ- "being, creature", and λόγος "speech, thought") is the study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments...

 evidence, but have become the paradigm of public opinion. Since 1980 the taxonomy (relationships), taphonomy
Taphonomy
Taphonomy is the study of decaying organisms over time and how they become fossilized . The term taphonomy was introduced to paleontology in 1940 by Russian scientist Ivan Efremov to describe the study of the transition of remains, parts, or products of organisms, from the biosphere, to the...

 (how the animals became embedded and fossilized), biomechanics (how their skeletons worked), and palaeobiology (life circumstances) of Plateosaurus have been re-studied in detail, altering the interpretation of the animal's biology, posture and behaviour.

Description

Plateosaurus is a member of a group of early herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...

s known as "prosauropods". The group name is obsolete, as "Prosauropoda" is not a monophyletic
Monophyly
In common cladistic usage, a monophyletic group is a taxon which forms a clade, meaning that it contains all the descendants of the possibly hypothetical closest common ancestor of the members of the group. The term is synonymous with the uncommon term holophyly...

 group (thus given in quotation marks), and most researchers prefer the term basal sauropodomorph
Sauropodomorpha
Sauropodomorpha is an extinct clade of long-necked, herbivorous, saurischian dinosaurs which includes the sauropods and their ancestral relatives. Sauropods generally grew to very large sizes, had long necks and tails, were quadrupedal, and became the largest animals to ever walk the Earth. The...

. Plateosaurus had the typical body shape of a herbivorous bipedal dinosaur: a small skull, a long and flexible neck composed of ten cervical
Neck
The neck is the part of the body, on many terrestrial or secondarily aquatic vertebrates, that distinguishes the head from the torso or trunk. The adjective signifying "of the neck" is cervical .-Boner anatomy: The cervical spine:The cervical portion of the human spine comprises seven boney...

 (neck) vertebrae, a stocky body and a long, mobile tail composed of at least 40 caudal
Tail
The tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, reptiles, and birds...

 (tail) vertebrae. The arms of Plateosaurus were very short, even compared to most other "prosauropods", but strongly built, with hands adapted to powerful grasping. The shoulder girdle was narrow (often misaligned in skeletal mounts and drawings), with the clavicle
Clavicle
In human anatomy, the clavicle or collar bone is a long bone of short length that serves as a strut between the scapula and the sternum. It is the only long bone in body that lies horizontally...

s (collar bones) touching at the body midline, as is the case in other basal sauropodomorphs. The hind limbs were held under the body, with slightly flexed knees and ankles, and the foot digitigrade
Digitigrade
A digitigrade is an animal that stands or walks on its digits, or toes. Digitigrades include walking birds , cats, dogs, and many other mammals, but not plantigrades or unguligrades...

 – the animal walked on its toes. The proportionally long lower leg and metatarsus
Metatarsus
The metatarsus or metatarsal bones are a group of five long bones in the foot located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the medial side : the first, second, third, fourth, and fifth...

 show that Plateosaurus was adapted to rapid bipedal locomotion. The tail of Plateosaurus was typically dinosaurian, muscular and with high mobility.
The skull of Plateosaurus is small and narrow, rectangular in side view, and nearly three times as long as it is high. There is an almost rectangular lateral temporal foramen at the back. The large, round orbit
Orbit (anatomy)
In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents...

 (eye socket), the sub-triangular antorbital fenestra
Antorbital fenestra
An antorbital fenestra is an opening in the skull, in front of the eye sockets. This skull formation first appeared in archosaurs during the Triassic Period. Living birds today possess antorbital fenestrae, but the feature has been lost in modern crocodilians...

 and the egg-shaped naris
Nostril
A nostril is one of the two channels of the nose, from the point where they bifurcate to the external opening. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation...

 (nostril) are of almost equal size. The snout carried many small, leaf-shaped, socketed teeth in both the upper and lower jaw, 5 to 6 on 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....

, 24 to 30 on the 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...

, and 21 to 28 on the dentary
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...

 (lower jaw). The teeth had bluntly serrated, thick, leaf-shaped crowns suitable for crushing plant material. The low position of the jaw joint gave the chewing muscles great leverage, so that Plateosaurus could deliver a powerful bite. These features suggest that it fed exclusively or mainly on plants. Its eyes were directed to the sides, rather than the front, providing all-round vision to watch for predators. Some fossil skeletons have preserved sclerotic ring
Sclerotic ring
Sclerotic rings are rings of bone found in the eyes of several groups of vertebrate animals, except for mammals and crocodilians. They can be made up of single bones or small bones together. They are believed to have a role in supporting the eye, especially in animals whose eyes are not spherical,...

s (rings of bone plates that protect the eye).

The ribs were connected to the dorsal (trunk) vertebrae with two joints, together acting as a simple hinge joint, which has allowed reconstructing the inhaled and exhaled positions of the ribcage. The difference in volume between both positions define the air exchange volume (the amount of air moved with each breath), determined to be ~20 l for a P. engelhardti individual estimated to have weighed 690 kg, or 29 ml/kg bodyweight. This is a typical value for birds, but not for mammals, and indicates that Plateosaurus probably had an avian-style flow-through lung, although indicators for postcranial pneumaticity
Skeletal pneumaticity
Skeletal pneumaticity is the presence of air spaces within bones. Skeletal pneumaticity exists only in synapsids and archosaurs. It is generally produced during development by excavation of bone by pneumatic diverticula from an air-filled space such as the lungs or nasal cavity...

 (air sacs of the lung invading the bones to reduce weight) can be found on the bones of only few individuals, and were only recognized in 2010. Combined with evidence from bone histology this indicates that Plateosaurus was an endotherm
Endotherm
An endotherm is an organism that produces heat through internal means, such as muscle shivering or increasing its metabolism...

.

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...

 of Plateosaurus is P. engelhardti. Adult individuals of this species reached 4.8 to 10 m (15.7 to 32.8 ft) in length. Adult individuals had a mass of around 600 to 4000 kg (1,322.8 to 8,818.5 lb). The older species, P. gracilis (formerly named Sellosaurus gracilis), was somewhat smaller, with a total length of 4 to 5 m (13.1 to 16.4 ft).

Discovery and history

In 1834, physician
Physician
A physician is a health care provider who practices the profession of medicine, which is concerned with promoting, maintaining or restoring human health through the study, diagnosis, and treatment of disease, injury and other physical and mental impairments...

 Johann Friedrich Engelhardt discovered some vertebrae and leg bones at Heroldsberg
Heroldsberg
Heroldsberg is a municipality in the district of Erlangen-Höchstadt, in Bavaria, Germany. It is the head quarter of Schwan-Stabilo....

 near Nuremberg
Nuremberg
Nuremberg[p] is a city in the German state of Bavaria, in the administrative region of Middle Franconia. Situated on the Pegnitz river and the Rhine–Main–Danube Canal, it is located about north of Munich and is Franconia's largest city. The population is 505,664...

, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

. Three years later German palaeontologist
Paleontology
Paleontology "old, ancient", ὄν, ὀντ- "being, creature", and λόγος "speech, thought") is the study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments...

 Hermann von Meyer
Christian Erich Hermann von Meyer
Christian Erich Hermann von Meyer was a German palaeontologist.He was born at Frankfurt am Main.In 1832 von Meyer issued a work entitled Palaeologica, and in course of time he published a series of memoirs on various fossil organic remains: molluscs, crustaceans, fishes and higher vertebrata,...

 designated them as the type specimen
Holotype
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...

 of a new genus, Plateosaurus. Since then, remains of well over 100 individuals of Plateosaurus have been discovered at various locations throughout Europe.

Material assigned to Plateosaurus has been found at over 50 localities in Germany (mainly along the Neckar
Neckar
The Neckar is a long river, mainly flowing through the southwestern state of Baden-Württemberg, but also a short section through Hesse, in Germany. The Neckar is a major right tributary of the River Rhine...

 and Pegnitz river valleys), Switzerland (Frick) and France. Three localities are of special importance, because they yielded specimens in large numbers and unusually good quality. Between the 1910s and 1930s, excavations in a clay pit
Clay pit
A clay pit is a quarry or mine for the extraction of clay, which is generally used for manufacturing pottery, bricks or Portland cement.The brickyard or brickworks is often located alongside the clay pit to reduce the transport costs of the raw material. These days pottery producers are often not...

 in Saxony-Anhalt
Saxony-Anhalt
Saxony-Anhalt is a landlocked state of Germany. Its capital is Magdeburg and it is surrounded by the German states of Lower Saxony, Brandenburg, Saxony, and Thuringia.Saxony-Anhalt covers an area of...

 dug up between 39 and 50 skeleton
Skeleton
The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...

s that belonged to Plateosaurus, along with teeth and a small number of bones of the theropod Liliensternus
Liliensternus
Liliensternus was a genus of coelophysoid dinosaur from the Late Triassic period, about 205 Ma.Liliensternus was originally named in 1934 by Friedrich von Huene as a second species of Halticosaurus, H. liliensterni, the specific name honouring the German amateur paleontologist, Dr...

and two skeletons and some fragments of the turtle Proganochelys
Proganochelys
Proganochelys quenstedti is the second oldest turtle species discovered to date, known only from fossils found in Germany and Thailand in strata from the late Triassic, dating to approximately 210 million years ago...

. Some of the plateosaur material was assigned to P. longiceps, a species now considered a junior synonym
Synonym (taxonomy)
In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...

 of P. engelhardti and described by palaeontologist Otto Jaekel
Otto Jaekel
Otto Max Johannes Jaekel was a German paleontologist and geologist.Jaekel was born in Neusalz , Prussian Silesia. He studied geology and paleontology in Liegnitz . After graduating in 1883, he moved to Breslau and studied under Ferdinand Roemer until 1885. Karl von Zittel awarded a PhD to Jaekel...

 in 1914. Most of the material found its way to the Museum für Naturkunde in Berlin
Berlin
Berlin is the capital city of Germany and is one of the 16 states of Germany. With a population of 3.45 million people, Berlin is Germany's largest city. It is the second most populous city proper and the seventh most populous urban area in the European Union...

, where much of it was destroyed during World War II. The Halberstadt quarry today is covered by a housing development.
The second major German locality with P. engelhardti finds, a quarry in Trossingen
Trossingen
Trossingen is a town in Baden-Württemberg, Germany. It is situated in a region called Baar, between the Swabian Alb and the Black Forest. Stuttgart is about an hour away, Lake Constance about half an hour, and the source of the river Danube can be reached in about twenty minutes by car.Trossingen...

 in the Black Forest
Black Forest
The Black Forest is a wooded mountain range in Baden-Württemberg, southwestern Germany. It is bordered by the Rhine valley to the west and south. The highest peak is the Feldberg with an elevation of 1,493 metres ....

, was worked repeatedly in the 20th century. Between 1911 and 1932, excavations during six field seasons led by German palaeontologists Eberhard Fraas (1911–1912), Friedrich von Huene
Friedrich von Huene
Friedrich von Huene was a German paleontologist who named more dinosaurs in the early 20th century than anyone else in Europe.-Biography:...

 (1921–23), and finally Reinhold Seemann (1932) revealed a total of 35 complete or partially complete skeletons of Plateosaurus, as well as fragmentary remains of approximately 70 more individuals. The large number of specimens from that area caused German palaeontologist Friedrich August von Quenstedt to nickname the animal Schwäbischer Lindwurm (Swabian lindworm or Swabian dragon).

The Plateosaurus skeletons in a clay pit of the Tonwerke Keller AG in Frick
Frick, Switzerland
Frick is a municipality in the district of Laufenburg in the canton of Aargau in Switzerland. A dinosaur graveyard containing more than 100 Plateosaurus was found there in August 2007.-History:...

, Switzerland, were first noticed in 1976. While the bones are often significantly deformed by taphonomic
Taphonomy
Taphonomy is the study of decaying organisms over time and how they become fossilized . The term taphonomy was introduced to paleontology in 1940 by Russian scientist Ivan Efremov to describe the study of the transition of remains, parts, or products of organisms, from the biosphere, to the...

 processes, Frick yields skeletons of P. engelhardti comparable in completeness and position to those of Trossingen and Halberstadt.

In 1997, workers of an oil platform
Oil platform
An oil platform, also referred to as an offshore platform or, somewhat incorrectly, oil rig, is a lаrge structure with facilities to drill wells, to extract and process oil and natural gas, and to temporarily store product until it can be brought to shore for refining and marketing...

 of the Snorre oil field
Snorre oil field
Snorre is an oil and gas field in the Tampen area in the southern part of the Norwegian Sea. The sea depth in the area is . Snorre is operational since August 1992. It was the first field developed by Saga Petroleum.-Production:...

 located at the northern end of the North Sea
North Sea
In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...

 were drilling through sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...

 for oil exploration when in a drill core extracted from 2,256 meters below the seafloor they stumbled upon a fossil they believed to be plant material. Martin Sander and Nicole Klein, palaeontologists of the University of Bonn
University of Bonn
The University of Bonn is a public research university located in Bonn, Germany. Founded in its present form in 1818, as the linear successor of earlier academic institutions, the University of Bonn is today one of the leading universities in Germany. The University of Bonn offers a large number...

, analysed the bone microstructure and concluded that the rock preserved fibrous bone tissue from a fragment of a limb bone belonging to Plateosaurus, making it the first dinosaur found in Norway. Plateosaurus material has also been found in the Fleming Fjord Formation
Fleming Fjord Formation
The Fleming Fjord Formation is a geological formation in eastern Greenland.-Vertebrate fauna:...

 of East Greenland.

Classification and type material

{clade|style=font-size:75% label1= Plateosauria
Plateosauria
Plateosauria is a clade of sauropodomorph dinosaurs which lived during the Late Triassic to the Late Cretaceous. The name Plateosauria was first coined by Gustav Tornier in 1913. The name afterwards fell out of use until the 1980s, when a new generation of paleontologists began using the name...

 
1=
}}
Basal sauropodomorph phylogeny simplified after Yates, 2007. This is only one of many proposed cladograms for basal sauropodomorphs. Some researchers do not agree that plateosaurs were the direct ancestors of sauropods

Plateosaurus was the first "prosauropod" to be described, and gives its name to the family Plateosauridae
Plateosauridae
Plateosauridae is a family of plateosaurian sauropodomorphs. Plateosaurids were early sauropodomorph dinosaurs which existed in Asia, Europe and South America during the Late Triassic period. Although several dinosaurs have been classified as plateosaurids over the years, a 2007 study by Adam M....

 as type genus
Type genus
In biological classification, a type genus is a representative genus, as with regard to a biological family. The term and concept is used much more often and much more formally in zoology than it is in botany, and the definition is dependent on the nomenclatural Code that applies:* In zoological...

. Initially, when the genus was poorly known, it was only included in Sauria
Sauria
Sauria is a clade of reptiles that includes all living diapsids, as well as their common ancestor and all its extinct descendants. The ancestral saurian was probably a small lizard-like creature living in the Permian Period...

, being some kind of reptile, but not in any more narrowly defined taxon. In 1845, von Meyer created the group Pachypodes
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

 (a defunct junior synonym
Synonym (taxonomy)
In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...

 of Dinosauria) to include Plateosaurus, Iguanodon
Iguanodon
Iguanodon is a genus of ornithopod dinosaur that lived roughly halfway between the first of the swift bipedal hypsilophodontids and the ornithopods' culmination in the duck-billed dinosaurs...

, Megalosaurus
Megalosaurus
Megalosaurus is a genus of large meat-eating theropod dinosaurs of the Middle Jurassic period of Europe...

and Hylaeosaurus
Hylaeosaurus
Hylaeosaurus is the most obscure of the three animals used by Sir Richard Owen to first define the new group Dinosauria, in 1842. The original specimen, recovered by Gideon Mantell from the Tilgate Forest in the south of England in 1832, now resides in the Natural History Museum of London, where...

. Plateosauridae was proposed by Othniel Charles Marsh
Othniel Charles Marsh
Othniel Charles Marsh was an American paleontologist. Marsh was one of the preeminent scientists in the field; the discovery or description of dozens of news species and theories on the origins of birds are among his legacies.Born into a modest family, Marsh was able to afford higher education...

 in 1895 within Theropoda
Theropoda
Theropoda is both a suborder of bipedal saurischian dinosaurs, and a clade consisting of that suborder and its descendants . Dinosaurs belonging to the suborder theropoda were primarily carnivorous, although a number of theropod groups evolved herbivory, omnivory, and insectivory...

. Later it was moved to "Prosauropoda" by von Huene, a placement that was accepted by most authors. For many years the clade only included Plateosaurus and various junior synonyms, but later two more genera were considered to belong to it: Sellosaurus and possibly Unaysaurus
Unaysaurus
Unaysaurus is a genus of sauropodomorph dinosaur, and is one of the oldest dinosaurs known. It was discovered in southern Brazil,in the geopark of paleorrota, in 1998, and announced in a press conference on Thursday, December 3, 2004...

. Of these, Sellosaurus is probably another junior synonym of Plateosaurus.

The type series of Plateosaurus engelhardti included "roughly 45 bones", of which nearly half are lost. The remaining material is kept in the Institute for Palaeontology of the University of Erlangen-Nuremberg, Germany. From it, German palaeontologist Markus Moser in 2003 selected a partial sacrum
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...

 (series of fused hip vertebrae) as a lectotype
Syntype
In biological nomenclature, a syntype is a term used to indicate a specimen with a special status.In zoological nomenclature, a syntype is defined as "Each specimen of a type series from which neither a holotype nor a lectotype has been designated [Arts. 72.1.2, 73.2, 74]. The syntypes...

. The type locality is not known for certain, but Moser attempted to infer it from previous publications and the colour and preservation of the bones, concluding that the material probably stems from the "Buchenbühl", roughly 2 kilometres (1.2 mi) south of Heroldsberg near Nuremberg
Nuremberg
Nuremberg[p] is a city in the German state of Bavaria, in the administrative region of Middle Franconia. Situated on the Pegnitz river and the Rhine–Main–Danube Canal, it is located about north of Munich and is Franconia's largest city. The population is 505,664...

, Bavaria, Germany.

The type specimen of Plateosaurus gracilis, an incomplete postcranium, is kept at the Staatliches Museum für Naturkunde Stuttgart
State Museum of Natural History Stuttgart
The State Museum of Natural History Stuttgart is one of the two state of Baden-Württemberg's natural history museums...

, Germany. The type locality is Heslach, a suburb of Stuttgart
Stuttgart
Stuttgart is the capital of the state of Baden-Württemberg in southern Germany. The sixth-largest city in Germany, Stuttgart has a population of 600,038 while the metropolitan area has a population of 5.3 million ....

, Germany.

Etymology

The etymology
Etymology
Etymology is the study of the history of words, their origins, and how their form and meaning have changed over time.For languages with a long written history, etymologists make use of texts in these languages and texts about the languages to gather knowledge about how words were used during...

 of the name Plateosaurus is not clear. Moser pointed out that the original description contains no information, and various authors have offered differing interpretations. Agassiz offered the first explanation, listing Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

 platê/πλατη ("paddle", "rudder"; Agassiz translates this as Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 pala = "spade") and sauros/σαυρος (lizard). Agassiz consequently renamed the genus Platysaurus, probably from Greek platys/πλατυς ("broad, flat, broad-shouldered"), creating an invalid junior synonym. This derivation was copied by later authors, so that Plateosaurus is often translated as "broad lizard" or "flat lizard". Often, claims were made that platys/πλατυς is supposed to have been intended as a reference to the laterally flattened teeth of Plateosaurus, which is impossible because the teeth were unknown at the time of description. Palaeontologist Markus Moser suggests the Ancient Greek plateia/πλατεια (broadway) as an alternative, which corresponds better to the stem of Plateosaurus, which clearly is "plate-", and not "platy-". Thus, the name should be translated as "broadway lizard".

Valid species

The taxonomic history of Plateosaurus is complex and confusing. As of 2009, only two species are accepted as valid, the type species P. engelhardti and the older P. gracilis, previously referred to as its own genus Sellosaurus. British palaeontologist Peter Galton
Peter Galton
Peter M. Galton is a British vertebrate paleontologist working in America, who has to date written or co-written about a hundred papers in scientific journals or chapters in paleontology textbooks, especially on ornithischian and prosauropod dinosaurs.With Robert Bakker in a joint article...

 showed clearly that all cranial material from Trossingen, Halberstadt and Frick pertains to one species. Moser performed the most extensive and detailed investigation of all plateosaurid material from Germany and Switzerland, concluding that all Plateosaurus and most other prosauropod material from the Keuper
Keuper
The Keuper is a lithostratigraphic unit in the subsurface of large parts of west and central Europe. The Keuper consists of dolostone, shales or claystones and evaporites that were deposited during the Middle and Late Triassic epochs...

 stems from the same species as the type material of Plateosaurus engelhardti. Moser considered Sellosaurus to be the same genus as Plateosaurus, but did not discuss whether S. gracilis and P. engelhardti belong to the same species. Palaeontologist Adam Yates of the University of the Witwatersrand
University of the Witwatersrand
The University of the Witwatersrand, Johannesburg is a South African university situated in the northern areas of central Johannesburg. It is more commonly known as Wits University...

 casted further doubt on the generic separation, and included the type material, but not all assigned finds of Sellosaurus gracilis, in Plateosaurus as P. gracilis. Previously, von Huene had already concluded this in 1926.

However, Yates cautioned that P. gracilis may be a metataxon, meaning that there is neither evidence that material assigned to it is monophyletic (belongs to one species), nor that it is paraphyletic
Paraphyly
A group of taxa is said to be paraphyletic if the group consists of all the descendants of a hypothetical closest common ancestor minus one or more monophyletic groups of descendants...

 (belongs to several species). This is the case because the holotype of P. (Sellosaurus) gracilis has no skull, and the other specimens consist of skulls and material that overlaps too little with the holotype to make certain that they belong to the same taxon. It is therefore possible that the known material contains more species belonging to Plateosaurus.

Invalid species

All named species of Plateosaurus except P. gracilis have turned out to be junior synonyms of the type species or invalid names. Huene practically erected a new species and sometimes a new genus for each relatively complete find from Trossingen (three species of Pachysaurus and seven of Plateosaurus) and Halberstadt (one species of Gresslyosaurus and eight of Plateosaurus). Later, he collapsed several of these species, but remained convinced that more than one genus and more than one species of Plateosaurus was present in both localities. Jaekel also believed that the Halberstadt material included several plateosaurid dinosaurs, as well as non-plateosaurid prosauropods. Systematic research by Galton drastically reduced the number of genera and species. Galton synonymised all cranial material, and described differences between the syntype
Syntype
In biological nomenclature, a syntype is a term used to indicate a specimen with a special status.In zoological nomenclature, a syntype is defined as "Each specimen of a type series from which neither a holotype nor a lectotype has been designated [Arts. 72.1.2, 73.2, 74]. The syntypes...

s of P. engelhardti and the Trossingen material, which he referred to P. longiceps. Galton recognized P. trossingensis, P. fraasianus and P. integer to be identical to P. longiceps. Markus Moser, however, showed clearly that P. longiceps is itself a junior synonym of P. engelhardti. Furthermore, a variety of species in other genera were created for material belonging to P. engelhardti, including Dimodosaurus poligniensis, Gresslyosaurus robustus, Gresslyosaurus torgeri, Pachysaurus ajax, Pachysaurus giganteus, Pachysaurus magnus and Pachysaurus wetzelianus.
However, there is much prosauropod material from the German Knollenmergel
Knollenmergel
The Knollenmergel is a geological formation in Germany and Switzerland. It dates back to the late Norian.-Dinosaurs:-References:* Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka : The Dinosauria, 2nd, Berkeley: University of California Press. 861 pp. ISBN 0-520-24209-2....

 in museum collections, most of it labelled as Plateosaurus, that does not belong to the type species, and possibly not to Plateosaurus at all. Some of this material is not diagnostic; other material has been recognized to be different, but was never sufficiently described.

Taphonomy

The taphonomy
Taphonomy
Taphonomy is the study of decaying organisms over time and how they become fossilized . The term taphonomy was introduced to paleontology in 1940 by Russian scientist Ivan Efremov to describe the study of the transition of remains, parts, or products of organisms, from the biosphere, to the...

 (burial and fossilization process) of the three main Plateosaurus sites—Trossingen, Halberstadt (both in Germany) and Frick (Switzerland)—is unusual in several ways. All three sites are nearly monospecific assemblages, meaning that they contain practically only one species, which requires very special circumstances. However, shed teeth of theropod
Theropoda
Theropoda is both a suborder of bipedal saurischian dinosaurs, and a clade consisting of that suborder and its descendants . Dinosaurs belonging to the suborder theropoda were primarily carnivorous, although a number of theropod groups evolved herbivory, omnivory, and insectivory...

s have been found at all three sites, as well as remains of Proganochelys, an early turtle. Additionally, a partial "prosauropod" skeleton was found in Halberstadt that does not belong to Plateosaurus, but is preserved in a similar position. All sites yielded almost complete and partial skeletons of Plateosaurus, as well as isolated bones. The partial skeletons tend to include the hind limbs and hips, while parts of the anterior body and neck are rarely found in isolation. The animals were all adults or subadults (nearly adult individuals); no juveniles or hatchlings are known. Complete skeletons and large skeleton parts that include the hind limbs all rest right side up, as do the turtles. Also, they are mostly well articulated, and the hind limbs are three-dimensionally preserved in a zigzag posture, with the feet often much deeper in the sediment than the hips.

Earlier interpretations

In the first published discussion of the Trossingen Plateosaurus finds, Fraas suggested that only miring in mud allowed the preservation of the single complete skeleton then known. Similarly, Jaekel interpreted the Halberstadt finds as animals that waded too deep into swamps, became mired and drowned. He interpreted partial remains as having been transported into the deposit by water, and strongly refuted a catastrophic accumulation. In contrast, von Huene interpreted the sediment as aeolian deposits, with the weakest animals, mostly subadults, succumbing to the harsh conditions in the desert and sinking into the mud of ephemeral water holes. He argued that the completeness of many finds indicated that transport did not happen, and saw partial individuals and isolated bones as results of weathering and trampling. Seemann developed a different scenario, in which Plateosaurus herds congregated on large water holes, and some herd members got pushed in. Light animals managed to get free, heavy ones got stuck and died.

A different school of thought developed almost half a century later, with palaeontologist David Weishampel suggesting that the skeletons from the lower layers stemmed from a herd that died catastrophically in a mudflow, while those in the upper layers accumulated over time. Weishampel explained the curious monospecific assemblage by theorizing that Plateosaurus were common during this period. This theory was erroneously attributed to Seemann in a popular account of the plateosaurs in the collection of the Institute and Museum for Geology and Palaeontology, University of Tübingen
Tübingen
Tübingen is a traditional university town in central Baden-Württemberg, Germany. It is situated south of the state capital, Stuttgart, on a ridge between the Neckar and Ammer rivers.-Geography:...

, and has since become the standard explanation on most internet sites and in popular books on dinosaurs. Rieber proposed a more elaborate scenario, which included the animals dying of thirst or starvation, and being concentrated by mudflows.

Current interpretation

A detailed re-assessment of the taphonomy by palaeontologist Martin Sander of the University of Bonn
University of Bonn
The University of Bonn is a public research university located in Bonn, Germany. Founded in its present form in 1818, as the linear successor of earlier academic institutions, the University of Bonn is today one of the leading universities in Germany. The University of Bonn offers a large number...

, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

, found that the mud-miring hypothesis first suggested by Fraas is true: animals above a certain body weight sank into the mud, which was further liquefied by their attempts to free themselves. Sander's scenario, similar to that proposed for the famous Rancho La Brea Tar Pits
La Brea Tar Pits
The La Brea Tar Pits are a cluster of tar pits around which Hancock Park was formed, in the urban heart of Los Angeles. Asphaltum or tar has seeped up from the ground in this area for tens of thousands of years. The tar is often covered with water...

, is the only one explaining all taphonomic data. The degree of completeness of the carcasses was not influenced by transport, which is obvious from the lack of indications for transport before burial, but rather by how much the dead animals were scavenged. Juveniles of Plateosaurus and other taxa of herbivores were too light to sink into the mud, or managed to extract themselves, and were thus not preserved. Similarly, the scavenging theropod
Theropoda
Theropoda is both a suborder of bipedal saurischian dinosaurs, and a clade consisting of that suborder and its descendants . Dinosaurs belonging to the suborder theropoda were primarily carnivorous, although a number of theropod groups evolved herbivory, omnivory, and insectivory...

s were not trapped due to their lower body weights, combined with a proportionally larger footprint. There is no indication of herding, or of catastrophic burial of such a herd, or catastrophic accumulation of animals that previously died isolated elsewhere.

Posture and gait

Practically any imaginable posture has been suggested for Plateosaurus in the scientific literature at some point. Von Huene
Friedrich von Huene
Friedrich von Huene was a German paleontologist who named more dinosaurs in the early 20th century than anyone else in Europe.-Biography:...

 assumed digitigrade
Digitigrade
A digitigrade is an animal that stands or walks on its digits, or toes. Digitigrades include walking birds , cats, dogs, and many other mammals, but not plantigrades or unguligrades...

 bipedality with erect hind limbs for the animals he excavated at Trossingen
Trossingen
Trossingen is a town in Baden-Württemberg, Germany. It is situated in a region called Baar, between the Swabian Alb and the Black Forest. Stuttgart is about an hour away, Lake Constance about half an hour, and the source of the river Danube can be reached in about twenty minutes by car.Trossingen...

, with the backbone held at a steep angle at least during rapid locomotion. In contrast, the main investigator of the Halberstadt
Halberstadt
Halberstadt is a town in the German state of Saxony-Anhalt and the capital of the district of Harz. It is located on the German Half-Timbered House Road and the Magdeburg–Thale railway....

 material, Jaekel, initially concluded that the animals walked quadrupedally, like lizards, with a sprawling limb position, plantigrade
Plantigrade
right|151px|thumb|Human skeleton, showing plantigrade habitIn terrestrial animals, plantigrade locomotion means walking with the podials and metatarsals flat on the ground. It is one of three forms of locomotion adopted by mammals...

, and laterally undulating
Undulatory locomotion
Undulatory locomotion is the type of motion characterized by wave-like movement patterns that act to propel an animal forward. Examples of this type of gait include crawling in snakes, or swimming in the lamprey...

 the body. Only a year later, Jaekel instead favoured a clumsy, kangaroo-like hopping, a change of heart for which he was mocked by German
Germans
The Germans are a Germanic ethnic group native to Central Europe. The English term Germans has referred to the German-speaking population of the Holy Roman Empire since the Late Middle Ages....

 zoologist
Zoology
Zoology |zoölogy]]), is the branch of biology that relates to the animal kingdom, including the structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct...

 Gustav Tornier, who interpreted the shape of the articulation surfaces in the hip and shoulder as typically reptilian. Fraas, the first excavator of the Trossingen lagerstätte
Lagerstätte
A Lagerstätte is a sedimentary deposit that exhibits extraordinary fossil richness or completeness.Palaeontologists distinguish two kinds....

, also favoured a reptilian posture. Müller-Stoll listed a number of characters required for an erect limb posture that Plateosaurus supposedly lacked, concluding that the lizard-like reconstructions were correct. However, most of these adaptations are actually present in Plateosaurus.
From 1980 on, a better understanding of dinosaur biomechanics, and studies by palaeontologists Andreas Christian and Holger Preuschoft on the resistance to bending of the back of Plateosaurus, led to widespread acceptance of an erect, digitigrade limb posture and a roughly horizontal position of the back. Many researchers were of the opinion that Plateosaurus could use both quadrupedal gaits (for slow speeds) and bipedal gaits (for rapid locomotion), while Wellnhofer
Peter Wellnhofer
Peter Wellnhofer is a German paleontologist at the "Bayerische Staatssammlung fur Paläontologie" in Munich. He is best known for his work on the various fossil specimens of Archaeopteryx or "Urvogel", the first known bird...

 insisted that the tail curved strongly downward, making a bipedal posture impossible. However, Moser showed that the tail was in fact straight.

This consensus was changed by a detailed study of the forelimbs of Plateosaurus by Bonnan
Matthew Bonnan
Matthew Bonnan is an American paleobiologist and an associate professor of biological sciences at Western Illinois University. His research combines traditional descriptive and anatomical study with computer-aided morphometric analysis and modeling of vertebrate skeletons. Dr...

 and Senter (2007), which clearly showed that Plateosaurus was incapable of pronating
Pronation
In anatomy, pronation is a rotational movement of the forearm at the radioulnar joint, or of the foot at the subtalar and talocalcaneonavicular joints. For the forearm, when standing in the anatomical position, pronation will move the palm of the hand from an anterior-facing position to a...

 its hands. The pronated position in some museum mounts had been achieved by exchanging the position of radius
Radius
In classical geometry, a radius of a circle or sphere is any line segment from its center to its perimeter. By extension, the radius of a circle or sphere is the length of any such segment, which is half the diameter. If the object does not have an obvious center, the term may refer to its...

 and ulna
Ulna
The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller. In anatomical position The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form...

 in the elbow. This meant that Plateosaurus was an obligate (i.e., unable to walk in any other way) digitigrade biped. Further indicators for a purely bipedal mode of locomotion are the great difference in limb length (the hind limb is roughly twice as long as the forelimb), the very limited motion range of the forelimb, and the fact that the center of mass
Center of mass
In physics, the center of mass or barycenter of a system is the average location of all of its mass. In the case of a rigid body, the position of the center of mass is fixed in relation to the body...

 rests squarely over the hind limbs.

Plateosaurus shows a number of cursorial
Cursorial
Cursorial is a biological term that describes an organism as being adapted specifically to run. It is typically used in conjunction with an animal's feeding habits or another important adaptation. For example, a horse can be considered a "cursorial grazer", while a wolf may be considered a...

 adaptations, including an erect hind limb posture, a relatively long lower leg, an elongated metatarsus
Metatarsus
The metatarsus or metatarsal bones are a group of five long bones in the foot located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the medial side : the first, second, third, fourth, and fifth...

 and a digitigrade foot posture. However, in contrast to mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

ian cursors, the moment arms of the limb extending
Extension (kinesiology)
In kinesiology, extension is a movement of a joint that results in increased angle between two bones or body surfaces at a joint. Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extending the flexed elbow. Straightening of...

 muscles are short, especially in the ankle, where a distinct, moment arm-increasing tuber on the calcaneum is missing. This means that in contrast to running mammals, Plateosaurus probably did not use gaits with aerial, unsupported phases. Instead, Plateosaurus must have increased speed by using higher stride frequencies, created by rapid and powerful limb retraction. Reliance on limb
Limb (anatomy)
A limb is a jointed, or prehensile , appendage of the human or other animal body....

 retraction
Retraction (kinesiology)
Retraction is the anatomical term of motion for posterior movement of the arms at the shoulders. It is the opposite of protraction. Major muscles involved include: * Rhomboid major muscle* Rhomboid minor muscle* Trapezius muscle-External links:* *...

 instead of extension is typical for non-avian dinosaurs.

Feeding and diet

Important cranial characteristics (such as jaw articulation) of most "prosauropods" are closer to those of herbivorous reptiles than those of carnivorous ones, and the shape of the tooth crown
Crown (tooth)
In dentistry, crown refers to the anatomical area of teeth, usually covered by enamel. The crown is usually visible in the mouth after developing below the gingiva and then erupting into place.-References:...

 is similar to those of modern herbivorous or omnivorous iguana
Iguana
Iguana is a herbivorous genus of lizard native to tropical areas of Central America and the Caribbean. The genus was first described in 1768 by Austrian naturalist Josephus Nicolaus Laurenti in his book Specimen Medicum, Exhibens Synopsin Reptilium Emendatam cum Experimentis circa Venena...

s. The maximum width of the crown was greater than that of the root, resulting in a cutting edge similar to those of extant herbivorous or omnivorous reptiles. This is also true in Plateosaurus. Paul Barrett proposed that prosauropods supplemented their herbivorous diets with small prey or carrion
Carrion
Carrion refers to the carcass of a dead animal. Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters include vultures, hawks, eagles, hyenas, Virginia Opossum, Tasmanian Devils, coyotes, Komodo dragons, and burying beetles...

.

So far, no fossil of Plateosaurus has been found with 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 (gizzard
Gizzard
The gizzard, also referred to as the ventriculus, gastric mill, and gigerium, is an organ found in the digestive tract of some animals, including birds, reptiles, earthworms and some fish. This specialized stomach constructed of thick, muscular walls is used for grinding up food; often rocks are...

 stones) in the stomach area. The old, widely cited idea that all large dinosaurs, implicitly also Plateosaurus, swallowed gastroliths to digest food because of their relatively limited ability to deal with food orally has been refuted by a study on gastrolith abundance, weight, and surface structure in fossils compared to alligators and ostriches by Oliver Wings. The use of gastroliths for digestion seems to have developed on the line from basal theropods to birds, with a parallel development in Psittacosaurus
Psittacosaurus
Psittacosaurus is a genus of psittacosaurid ceratopsian dinosaur from the Early Cretaceous Period of what is now Asia, about 130 to 100 million years ago. It is notable for being the most species-rich dinosaur genus...

.

Growth, metabolism and life span

Similar to all non-avian dinosaurs studied to date, Plateosaurus grew in a pattern that is dissimilar to both extant mammals and avian dinosaurs. In the closely related sauropods with their typical dinosaurian physiology, growth was initially rapid, continued somewhat slower well beyond sexual maturity, but was determinate, i.e. the animals stopped growing at a maximum size. Mammals grow rapidly, but sexual maturity falls typically at the end of the rapid growth phase. In both groups, the final size is relatively constant, with humans atypically variable. Extant reptiles show a sauropod-like growth pattern, initially rapid, then slowing after sexual maturity, and almost, but not fully, stopping in old age. However, their initial growth rate is much lower than in mammals, birds and dinosaurs. The reptilian growth rate is also very variable, so that individuals of the same age may have very different sizes, and final size also varies significantly. In extant animals, this growth pattern is linked to behavioural thermoregulation and a low metabolic
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

 rate (i.e. ectotherm
Ectotherm
An ectotherm, from the Greek εκτός "outside" and θερμός "hot", refers to organisms that control body temperature through external means. As a result, organisms are dependent on environmental heat sources and have relatively low metabolic rates. For example, many reptiles regulate their body...

y), and is called "developmental plasticity". (Note that is not the same as neural developmental plasticity
Developmental plasticity
Developmental plasticity is a general term referring to changes in neural connections during development as a result of environmental interactions as well as neural changes induced by learning...

.)
Plateosaurus followed a trajectory similar to sauropods, but with a varied growth rate and final size as seen in extant reptiles, probably in response to environmental factors such as food availability. Some individuals were fully grown at only 4.8 metres (15.7 ft) total length, while others reached 10 metres (32.8 ft). However, the bone microstructure indicates rapid growth, as in sauropods and extant mammals, which suggests endothermy
Warm-blooded
The term warm-blooded is a colloquial term to describe animal species which have a relatively higher blood temperature, and maintain thermal homeostasis primarily through internal metabolic processes...

. Plateosaurus apparently represents an early stage in the development of endothermy, in which endothermy was decoupled from developmental plasticity. This hypothesis is based on a detailed study of Plateosaurus long-bone histology conducted by Martin Sander and Nicole Klein of the University of Bonn
University of Bonn
The University of Bonn is a public research university located in Bonn, Germany. Founded in its present form in 1818, as the linear successor of earlier academic institutions, the University of Bonn is today one of the leading universities in Germany. The University of Bonn offers a large number...

, Germany. A further indication for endothermy is the avian-style lung of Plateosaurus.

Long-bone histology also allows estimating the age a specific individual reached. Sander and Klein found that some individuals were fully grown at 12 years of age, others were still slowly growing at 20 years, and one individual was still rapidly growing at 18 years. The oldest individual found was 27 years and still growing; most individuals were between 12 and 20 years old. However, some individually may well have lived much longer, because the fossils from Frick and Trossingen are all animals that died in accidents, and not from old age. Due to the absence of individuals smaller than 4.8 metres (15.7 ft) long, it is not possible to deduce a complete ontogenetic
Ontogeny
Ontogeny is the origin and the development of an organism – for example: from the fertilized egg to mature form. It covers in essence, the study of an organism's lifespan...

 series for Plateosaurus or determine the growth rate of animals less than 10 years of age.

Daily activity patterns

Comparisons between the scleral ring
Sclerotic ring
Sclerotic rings are rings of bone found in the eyes of several groups of vertebrate animals, except for mammals and crocodilians. They can be made up of single bones or small bones together. They are believed to have a role in supporting the eye, especially in animals whose eyes are not spherical,...

s and estimated orbit size of Plateosaurus and modern birds and reptiles suggest that it may have been cathemeral
Cathemeral
A cathemeral organism is one that has sporadic and random intervals of activity during the day or night in which food is acquired, socializing with other organisms occurs, and any other activities necessary for livelihood are performed...

, active throughout the day and night, possibly avoiding the mid-day heat.

External links

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