''Plateosaurus'' (probably meaning "broad
lizard
Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia alt ...
", often mistranslated as "flat lizard") is a
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of
plateosaurid dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
that lived during the Late
Triassic
The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...
period
Period may refer to:
Common uses
* Era, a length or span of time
* Full stop (or period), a punctuation mark
Arts, entertainment, and media
* Period (music), a concept in musical composition
* Periodic sentence (or rhetorical period), a concept ...
, around 214 to 204
million years ago
The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds.
Usage
Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago). ...
, in what is now Central and Northern Europe. ''Plateosaurus'' is a
basal (early)
sauropodomorph
Sauropodomorpha ( ; from Greek, meaning "lizard-footed forms") is an extinct clade of long-necked, herbivorous, saurischian dinosaurs that includes the sauropods and their ancestral relatives. Sauropods generally grew to very large sizes, had lon ...
dinosaur, a so-called
"prosauropod". 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 ...
is ''Plateosaurus trossingensis''; before 2019, that honor was given to ''Plateosaurus engelhardti'', but it was ruled as undiagnostic (i.e. indistinguishable from other dinosaurs) by the
ICZN
The International Code of Zoological Nomenclature (ICZN) is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals. It is also informally known as the ICZN Code, for its publisher, the I ...
. Currently, there are three valid species; in addition to ''P. trossingensis'', ''P. longiceps'' and ''P. gracilis'' are also known. However, others have been assigned in the past, and there is no broad consensus on the species
taxonomy
Taxonomy is the practice and science of categorization or classification.
A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...
of plateosaurid dinosaurs. Similarly, there are a plethora of
synonyms
A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...
(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 (3 September 1801 – 2 April 1869), known as Hermann von Meyer, was a German palaeontologist. He was awarded the 1858 Wollaston medal by the Geological Society of London.
Life
He was born at Frankfurt am Ma ...
, ''Plateosaurus'' was the fifth named dinosaur genus that is still considered valid. Although it had been described before
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 ...
formally named Dinosauria in 1842, it was not one of the three genera used by Owen to define the group, 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: over 100 skeletons have been found, some of them nearly complete. The abundance of its fossils in
Swabia
Swabia ; german: Schwaben , colloquially ''Schwabenland'' or ''Ländle''; archaic English also Suabia or Svebia is a cultural, historic and linguistic region in southwestern Germany.
The name is ultimately derived from the medieval Duchy of ...
, Germany, has led to the nickname ''Schwäbischer Lindwurm'' (Swabian
lindworm
The lindworm (''worm'' meaning snake), also spelled lindwyrm or lindwurm, is a mythical creature in Northern and Central European folklore living deep in the forest that traditionally has the shape of a giant serpent monster. It can be seen as a ...
).
''Plateosaurus'' was a
bipedal
Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning 'two feet' (from Latin ''bis'' 'double' ...
herbivore
A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...
with a small skull on a long, flexible 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 long and weighed between . 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 () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Eart ...
and
palaeontological
Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (geology), epoch (roughly 11,700 years before present). It includes t ...
evidence, but have become the paradigm of public opinion. Since 1980 the taxonomy (relationships),
taphonomy
Taphonomy is the study of how organisms decay and become fossilized or preserved in the paleontological record. The term ''taphonomy'' (from Greek , 'burial' and , 'law') was introduced to paleontology in 1940 by Soviet scientist Ivan Efremov t ...
(how the animals became embedded and fossilised), 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.
Discovery and history
![Plateosaurus cent europ localities2](https://upload.wikimedia.org/wikipedia/commons/d/df/Plateosaurus_cent_europ_localities2.png)
In 1834, physician Johann Friedrich Engelhardt discovered some vertebrae and leg bones at
Heroldsberg
Heroldsberg (East Franconian: ''Herldsbärch'') is a municipality in the district of Erlangen-Höchstadt, in Bavaria, Germany. It is located eleven kilometers north-east from the city of Nuremberg and 23 kilometers east from Erlangen and is the hea ...
near
Nuremberg
Nuremberg ( ; german: link=no, Nürnberg ; in the local East Franconian dialect: ''Nämberch'' ) is the second-largest city of the German state of Bavaria after its capital Munich, and its 518,370 (2019) inhabitants make it the 14th-largest ...
, Germany.
[ Three years later German ]palaeontologist
Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...
Hermann von Meyer
Christian Erich Hermann von Meyer (3 September 1801 – 2 April 1869), known as Hermann von Meyer, was a German palaeontologist. He was awarded the 1858 Wollaston medal by the Geological Society of London.
Life
He was born at Frankfurt am Ma ...
designated them as the type specimen
In biology, a type is a particular wiktionary:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to a ...
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
The Neckar () is a river in Germany, mainly flowing through the southwestern state of Baden-Württemberg, with a short section through Hesse. The Neckar is a major right tributary of the Rhine. Rising in the Schwarzwald-Baar-Kreis near Schwenn ...
and Pegnitz river valleys), Switzerland ( Frick) and France.[ Three localities are of special importance, because they yielded specimens in large numbers and of unusually good quality: near ]Halberstadt
Halberstadt ( Eastphalian: ''Halverstidde'') is a town in the German state of Saxony-Anhalt, the capital of Harz district. Located north of the Harz mountain range, it is known for its old town center that was greatly destroyed by Allied bombi ...
in Saxony-Anhalt
Saxony-Anhalt (german: Sachsen-Anhalt ; nds, Sassen-Anholt) is a state of Germany, bordering the states of Brandenburg, Saxony, Thuringia and Lower Saxony. It covers an area of
and has a population of 2.18 million inhabitants, making it the ...
, Germany; Trossingen
Trossingen ( Swabian: ''Drossinge'') 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 sour ...
in Baden-Württemberg
Baden-Württemberg (; ), commonly shortened to BW or BaWü, is a German state () in Southwest Germany, east of the Rhine, which forms the southern part of Germany's western border with France. With more than 11.07 million inhabitants across a ...
, Germany; and Frick.[ Between the 1910s and 1930s, excavations in a ]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. Quarries where clay is mined to make bricks are sometimes called brick pits.
A brickyard or brickworks is of ...
in Saxony-Anhalt revealed between 39 and 50 skeletons that belonged to ''Plateosaurus'', along with teeth and a small number of bones of the theropod
Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...
'' Liliensternus'', and two skeletons and some fragments of the turtle ''Proganochelys
''Proganochelys'' is an extinct, primitive stem-turtle that has been hypothesized to be the sister taxon to all other turtles creating a monophyletic group, the ''Casichelydia''. ''Proganochelys'' was named by Georg Baur in 1887 as the oldest tur ...
''.[ Some of the plateosaur material was assigned to ''P. longiceps'', a species described by palaeontologist ]Otto Jaekel
Otto Max Johannes Jaekel (21 February 1863 – 6 March 1929) was a German paleontologist and geologist.
Biography
Jaekel was born in Neusalz (Nowa Sól), Prussian Silesia, the son of a builder and the youngest of seven children. He studied at ...
in 1914.[ Most of the material found its way to the ]Museum für Naturkunde
The Natural History Museum (german: Museum für Naturkunde) is a natural history museum located in Berlin, Germany. It exhibits a vast range of specimens from various segments of natural history and in such domain it is one of three major muse ...
in Berlin, 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 ''Plateosaurus'' finds, a quarry in Trossingen in the Black Forest
The Black Forest (german: Schwarzwald ) is a large forested mountain range in the state of Baden-Württemberg in southwest Germany, bounded by the Rhine Valley to the west and south and close to the borders with France and Switzerland. It is t ...
, 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, born Friedrich Richard von Hoinigen, (March 22, 1875 – April 4, 1969) was a German paleontologist who renamed more dinosaurs in the early 20th century than anyone else in Europe. He also made key contributions about v ...
(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 ]Swabia
Swabia ; german: Schwaben , colloquially ''Schwabenland'' or ''Ländle''; archaic English also Suabia or Svebia is a cultural, historic and linguistic region in southwestern Germany.
The name is ultimately derived from the medieval Duchy of ...
had already caused German palaeontologist Friedrich August von Quenstedt to nickname the animal ''Schwäbischer Lindwurm'' (Swabian lindworm
The lindworm (''worm'' meaning snake), also spelled lindwyrm or lindwurm, is a mythical creature in Northern and Central European folklore living deep in the forest that traditionally has the shape of a giant serpent monster. It can be seen as a ...
or Swabian dragon
A dragon is a reptilian legendary creature that appears in the folklore of many cultures worldwide. Beliefs about dragons vary considerably through regions, but dragons in western cultures since the High Middle Ages have often been depicted as ...
). Much of the Trossingen material was destroyed in 1944, when the Naturaliensammlung in Stuttgart (predecessor to the State Museum of Natural History Stuttgart
The State Museum of Natural History Stuttgart (german: Staatliches Museum für Naturkunde Stuttgart), abbreviated SMNS, is one of the two state of Baden-Württemberg's natural history museums. Together with the State Museum of Natural History ...
(SMNS)) burnt to the ground after an Allied bombing raid. Luckily, however, a 2011 study by SMNS curator Rainer Schoch found that, at least from the finds of Seemann's 1932 excavation, "the scientifically most valuable material is still available".
The ''Plateosaurus'' skeletons in a clay pit of the Tonwerke Keller AG in Frick, Switzerland, were first noticed in 1976.[ While the bones are often significantly deformed by ]taphonomic
Taphonomy is the study of how organisms decay and become fossilized or preserved in the paleontological record. The term ''taphonomy'' (from Greek , 'burial' and , 'law') was introduced to paleontology in 1940 by Soviet scientist Ivan Efremov t ...
processes, Frick yields skeletons of ''P. trossingensis'' comparable in completeness and position to those of Trossingen.[
In 1997, workers of an ]oil platform
An oil platform (or oil rig, offshore platform, oil production platform, and similar terms) is a large structure with facilities to extract and process petroleum and natural gas that lie in rock formations beneath the seabed. Many oil platfor ...
of the 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 has been operational since August 1992. It was the first field developed by Saga Petroleum.
A ''Plateosaurus'' ...
, located at the northern end of the North Sea
The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...
within the Lunde Formation, were drilling through sandstone
Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks.
Most sandstone is composed of quartz or feldspar (both silicates) ...
for oil exploration when they stumbled on a fossil they believed to be plant material. The drill core containing the fossil was extracted from below the seafloor.[ Martin Sander and Nicole Klein, palaeontologists of the ]University of Bonn
The Rhenish Friedrich Wilhelm University of Bonn (german: Rheinische Friedrich-Wilhelms-Universität Bonn) is a public research university located in Bonn, North Rhine-Westphalia, Germany. It was founded in its present form as the ( en, Rhine U ...
, 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. Material referred to ''Plateosaurus'' has also been found in the ]Fleming Fjord Formation
The Fleming Fjord Formation, alternatively called the Fleming Fjord Group is an Upper Triassic geological formation in the northeastern coast of Jameson Land, Greenland. It consists of terrestrial sediments and is known for its fossil content.
...
of East Greenland,[ but they were given the new genus name '']Issi
''Issi'' (meaning "cold" in Greenlandic) is a plateosaurid dinosaur described in 2021 from the Late Triassic Fleming Fjord Formation of Greenland. It contains one species, ''Issi saaneq''; the full binomial name means "cold bones".
Fossils of ...
'' in 2021.
The type series of ''Plateosaurus engelhardti'' included "roughly 45 bone fragments", of which nearly half are lost. The remaining material is kept in the Institute for Palaeontology of the University of Erlangen-Nuremberg
A university () is an institution of higher (or tertiary) education and research which awards academic degrees in several academic disciplines. Universities typically offer both undergraduate and postgraduate programs. In the United States, t ...
, Germany. From these bones, German palaeontologist Markus Moser in 2003 selected a partial sacrum
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 ...
(series of fused hip vertebrae) as a lectotype
In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes the ...
. 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. He concluded that the material probably stems from the "Buchenbühl", roughly south of Heroldsberg.
The type specimen of ''Plateosaurus gracilis'', an incomplete postcranium Postcrania (postcranium, adjective: postcranial) in zoology and vertebrate paleontology is all or part of the skeleton apart from the skull. Frequently, fossil remains, e.g. of dinosaurs or other extinct tetrapods, consist of partial or isolated s ...
, is kept at the Staatliches Museum für Naturkunde Stuttgart, Germany, and the type locality is Heslach, a suburb of the same city.
The type specimen of ''Plateosaurus trossingensis'' is SMNS 132000, stored in the same museum as ''P. gracilis''. Its type locality is Trossingen, which is located in Baden-Württemberg and the Löwenstein Formation
The Löwenstein Formation (Stubensandstein in Baden-Württemberg, Burgsandstein in Bavaria) is a lithostratigraphic formation of the Keuper in Germany. It is underlain by the Mainhardt Formation and overlain by the Trossingen Formation. It dates ...
.
The type specimen of ''Plateosaurus longiceps'' is MB R.1937, which is stored in the Museum für Naturkunde
The Natural History Museum (german: Museum für Naturkunde) is a natural history museum located in Berlin, Germany. It exhibits a vast range of specimens from various segments of natural history and in such domain it is one of three major muse ...
in Berlin. Its type locality is Halberstadt, located in Saxony-Anhalt and the Knollenmergel Member of the Trossingen Formation
The Trossingen Formation, formerly the Knollenmergel, is a geological formation in Germany and Switzerland. It dates back to the late Norian- Rhaetian.Weishampel et al., 2004, pp.521–525
Vertebrate paleofauna
See also
* List of dinosa ...
.
Etymology
The etymology
Etymology ()The New Oxford Dictionary of English (1998) – p. 633 "Etymology /ˌɛtɪˈmɒlədʒi/ the study of the class in words and the way their meanings have changed throughout time". is the study of the history of the Phonological chan ...
of the name ''Plateosaurus'' is not entirely clear. Moser pointed out that the original description contains no information, and various authors have offered differing interpretations. German geologist Hanns Bruno Geinitz
Hanns Bruno Geinitz (16 October 1814 – 28 January 1900) was a German geologist, born at Altenburg, the capital of Saxe-Altenburg.
He was educated at the universities of Berlin and Jena, and gained the foundations of his geological knowledge ...
in 1846 gave
πλᾰτῠ́ς
breit)" nglish: broad with von Meyer's Latin spelling ''Plateosaurus'' evidently derived from the stem of πλᾰτέος (''plateos''), the genitive case of the masculine adjective ''platys'' in Ancient Greek. In the same year, Agassiz offered Ancient Greek
Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...
'' πλατη'' (''platê'' – "paddle", "rudder"; Agassiz translates this as Latin
Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
''pala'' = "spade") and
σαυρος
' (''sauros'' – "lizard"). Agassiz consequently renamed the genus ''Platysaurus'', probably from Greek ''πλατυς'' (''platys'' – "broad, flat, broad-shouldered"), creating an invalid junior synonym. Later authors often referred to this derivation, and the secondary meaning "flat" of ''πλατυς'', so that ''Plateosaurus'' is often translated as "flat lizard". Often, claims were made that ''πλατυς'' is supposed to have been intended as a reference to flat bones, for example the laterally flattened teeth of ''Plateosaurus'', but the teeth and other flat bones such as the pubic bones and some skull elements were unknown at the time of description.[
In 1855, von Meyer published a detailed description of ''Plateosaurus'' with illustrations, but again gave no details on the etymology. He repeatedly referred to its gigantic size ("Riesensaurus" = giant lizard) and massive limbs ("schwerfüssig"), comparing ''Plateosaurus'' to large modern land mammals, but did not describe any important features that fit the terms "flat" or "shaped like an oar."][
In addition to his formal scientific descriptions, von Meyer also gave a public lecture about fossil reptiles in 1851 that included a short mention of ''Plateosaurus''. That talk and a later one on fossil mammals were turned into a general audience book published in 1852, entitled ''Über die Reptilien und Säugethiere der verschiedenen Zeiten der Erde'' 'On the Reptiles and Mammals from the Different Time Periods of the Earth''][ In the German text (page 44), von Meyer briefly described ''Plateosaurus'' and mentioned that it had "breite, starke Gliedmaassenknochen," which translates as "broad, strong limb bones." Because his original description of ''Plateosaurus'' in 1837 stressed the similarity of its large limb bones to those of ''Megalosaurus'' and ''Iguanodon'', a meaning "broad lizard" for the name ''Plateosaurus'' to refer in particular to its robust limb bones would seem plausible.
]
Valid species
The taxonomic history of ''Plateosaurus'' is "long and confusing", a "chaotic tangle of names". As of 2019, only three species are universally accepted as valid: the type species ''P. trossingensis, P. longiceps, and'' ''P. gracilis'', previously assigned to its own genus ''Sellosaurus''. 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
The Keuper is a lithostratigraphic unit (a sequence of rock strata) in the subsurface of large parts of west and central Europe. The Keuper consists of dolomite, shales or claystones and evaporites that were deposited during the Middle and Late ...
stems from the same species as the type material of ''Plateosaurus engelhardti''. However, this is problematic due to the undiagnostic state of the lectotype. 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
The University of the Witwatersrand, Johannesburg (), is a multi-campus South African Public university, public research university situated in the northern areas of central Johannesburg. It is more commonly known as Wits University or Wits ( o ...
cast further doubt on the generic separation. He included the type material of ''Sellosaurus gracilis'' in ''Plateosaurus'' as ''P. gracilis'' and reintroduced the old name ''Efraasia
''Efraasia'' (pronounced "E-FRAHS-ee-A") is a genus of basal sauropodomorph dinosaur. It was a herbivore which lived during the middle Norian stage of the Late Triassic, around 210 million years ago, in what is now Germany. It was named in 1 ...
'' for some material that had been assigned to ''Sellosaurus''.[ In 1926, von Huene had already concluded the two genera were the same.
Yates has cautioned that ''P. gracilis'' may be a metataxon, which means that there is neither evidence that the material assigned to it is monophyletic (belongs to one species), nor that it is ]paraphyletic
In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...
(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 it certain that it belongs to the same taxon. It is therefore possible that the known material contains more species belonging to ''Plateosaurus''.
Some scientists regard other species as valid as well, for example ''P. erlenbergensis'' and ''P. engelhardti''.[ These claims are problematic since both ''P. erlenbergensis'' and ''P. engelhardti'' have undiagnostic type specimens.]
All named species of ''Plateosaurus'' except the type species, ''P. gracilis,'' or ''P. longiceps'' have turned out to be junior synonyms of the type species or invalid names.[ Von 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 merged 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
In biological nomenclature, a syntype is any one of two or more biological types that is listed in a description of a taxon where no holotype was designated. Precise definitions of this and related terms for types have been established as part of ...
s of ''P. engelhardti'' and the Trossingen material, which he referred to ''P. longiceps''.[ Galton recognised ''P. trossingensis'' (''P. fraasianus'' and ''P. integer'' are junior objective synonyms) to be identical to ''P. longiceps''.] Markus Moser, however, showed 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''. ''G. ingens'' has been considered separate from ''Plateosaurus'', pending a revision of the material.
The skull of AMNH FARB 6810, the best-preserved skull of ''Plateosaurus'' that has been taken apart during preparation and is thus available as separate bones, was described anew in 2011.][ The authors of that publication, palaeontologists Albert Prieto-Márquez and Mark A. Norell, refer the skull to ''P. erlenbergensis'', a species erected in 1905 by Friedrich von Huene and regarded as a synonym of ''P. engelhardti'' by Markus Moser. If the ''P. erlenbergensis'' holotype is diagnostic (i.e., has enough characters to be distinct from other material), it is the correct name for the material assigned to ''P. longiceps'' Jaekel, 1913.][
Aside from fossils clearly belonging to ''Plateosaurus'', there is much prosauropod material from the German Knollenmergel in museum collections, most of it labeled 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 recognised to be different, but was never sufficiently described.
]
Description
''Plateosaurus'' had the typical body shape of a herbivorous bipedal dinosaur: a small skull, a long and flexible neck composed of 10 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 ...
, a stocky body, and a long, mobile tail composed of at least 40 caudal vertebrae
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 ...
.[ The arms of ''Plateosaurus'' were very short, even compared to most other "prosauropods". However, they were strongly built, with hands adapted for powerful grasping.][ The ]shoulder girdle
The shoulder girdle or pectoral girdle is the set of bones in the appendicular skeleton which connects to the arm on each side. In humans it consists of the clavicle and scapula; in those species with three bones in the shoulder, it consists of t ...
was narrow (often misaligned in skeletal mounts and drawings),[ with the ]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 (collar bones) touching at the body's midline,[ as in other basal sauropodomorphs.][ The hind limbs were held under the body, with slightly flexed knees and ankles, and the foot was ]digitigrade
In terrestrial vertebrates, digitigrade () locomotion is walking or running on the toes (from the Latin ''digitus'', 'finger', and ''gradior'', 'walk'). A digitigrade animal is one that stands or walks with its toes (metatarsals) touching the groun ...
, meaning the animal walked on its toes.[ The proportionally long lower leg and ]metatarsus
The metatarsal bones, or metatarsus, 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 med ...
show that ''Plateosaurus'' could run quickly on its hind limbs.[ 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
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 socket), the sub-triangular antorbital fenestra
An antorbital fenestra (plural: fenestrae) is an opening in the skull that is in front of the eye sockets. This skull character is largely associated with archosauriforms, first appearing during the Triassic Period. Among extant archosaurs, birds ...
and the oval naris
A nostril (or naris , plural ''nares'' ) is either of the two orifices of the nose. They enable the entry and exit of air and other gasses through the nasal cavities. In birds and mammals, they contain branched bones or cartilages called turbi ...
(nostril) are of almost equal size.[ The jaws carried many small, leaf-shaped, socketed teeth: 5 to 6 per ]premaxilla
The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has b ...
, 24 to 30 per maxilla
The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...
, and 21 to 28 per dentary
In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...
(lower jaw).[ The thick, leaf-shaped, bluntly serrated tooth crowns were 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 primarily to exclusively 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 rings are rings of bone found in the eyes of many animals in several groups of vertebrates, except for mammals and crocodilians. They can be made up of single bones or multiple segments and take their name from the sclera. They are bel ...
s (rings of bone plates that protect the eye).[
]
The ribs were connected to the dorsal (trunk) vertebrae with two joints, acting together as a simple hinge joint, which has allowed researchers to reconstruct the inhaled and exhaled positions of the ribcage. The difference in volume between these two positions defines the air exchange volume (the amount of air moved with each breath), determined to be approximately 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
Avian may refer to:
*Birds or Aves, winged animals
*Avian (given name) (russian: Авиа́н, link=no), a male forename
Aviation
*Avro Avian, a series of light aircraft made by Avro in the 1920s and 1930s
*Avian Limited, a hang glider manufacture ...
-style flow-through lung,[ although indicators for postcranial pneumaticity (air sacs of the lung invading the bones to reduce weight) can be found on the bones of only a few individuals, and were only recognised in 2010.][ Combined with evidence from bone ]histology
Histology,
also known as microscopic anatomy or microanatomy, is the branch of biology which studies the microscopic anatomy of biological tissues. Histology is the microscopic counterpart to gross anatomy, which looks at larger structures vis ...
[ this indicates that ''Plateosaurus'' was ]endotherm
An endotherm (from Greek ἔνδον ''endon'' "within" and θέρμη ''thermē'' "heat") is an organism that maintains its body at a metabolically favorable temperature, largely by the use of heat released by its internal bodily functions inste ...
ic.[
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 ''Plateosaurus'' is ''P. trossingensis''.[ Adults of this species reached in length,][ and ranged in mass from .][ The geologically older species, ''P. gracilis'' (formerly named ''Sellosaurus gracilis''), was somewhat smaller, with a total length of .][
]
Classification
''Plateosaurus'' is a member of a group of early herbivore
A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...
s known as "prosauropods
Plateosauridae is a family (biology), family of plateosaurian sauropodomorphs from the Late Triassic of Europe, Greenland, Africa and Asia. Although several dinosaurs have been classified as plateosaurids over the years, the family Plateosaurida ...
".[ The group is not a ]monophyletic
In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...
group (thus given in quotation marks), and most researchers prefer the term ''basal sauropodomorph
Sauropodomorpha ( ; from Greek, meaning "lizard-footed forms") is an extinct clade of long-necked, herbivorous, saurischian dinosaurs that includes the sauropods and their ancestral relatives. Sauropods generally grew to very large sizes, had lon ...
''.[ ''Plateosaurus'' was the first "prosauropod" to be described,][ and gives its name to the family ]Plateosauridae
Plateosauridae is a family of plateosaurian sauropodomorphs from the Late Triassic of Europe, Greenland, Africa and Asia. Although several dinosaurs have been classified as plateosaurids over the years, the family Plateosauridae is now restric ...
as the type genus
In biological taxonomy, the type genus is the genus which defines a biological family and the root of the family name.
Zoological nomenclature
According to the International Code of Zoological Nomenclature, "The name-bearing type of a nominal f ...
.[ Initially, when the genus was poorly known, it was only included in ]Sauria
Sauria is the clade containing the most recent common ancestor of archosaurs (such as crocodilians, dinosaurs, etc.) and lepidosaurs ( lizards and kin), and all its descendants. Since most molecular phylogenies recover turtles as more closely re ...
, being some kind of reptile, but not in any more narrowly defined taxon.[ In 1845, von Meyer created the group Pachypodes (a defunct junior ]synonym
A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...
of Dinosauria) to include ''Plateosaurus'', ''Iguanodon
''Iguanodon'' ( ; meaning 'iguana-tooth'), named in 1825, is a genus of iguanodontian dinosaur. While many species have been classified in the genus ''Iguanodon'', dating from the late Jurassic Period to the early Cretaceous Period of Asia, Eu ...
'', ''Megalosaurus
''Megalosaurus'' (meaning "great lizard", from Greek , ', meaning 'big', 'tall' or 'great' and , ', meaning 'lizard') is an extinct genus of large carnivorous theropod dinosaurs of the Middle Jurassic period (Bathonian stage, 166 million years a ...
'' and ''Hylaeosaurus
''Hylaeosaurus'' ( ; Greek: / "belonging to the forest" and / "lizard") is a herbivorous ankylosaurian dinosaur that lived about 136 million years ago, in the late Valanginian stage of the early Cretaceous period of England. It was found in ...
''.[ Plateosauridae was proposed by ]Othniel Charles Marsh
Othniel Charles Marsh (October 29, 1831 – March 18, 1899) was an American professor of Paleontology in Yale College and President of the National Academy of Sciences. He was one of the preeminent scientists in the field of paleontology. Among h ...
in 1895 within Theropoda
Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally ca ...
.[ Later it was moved to "]Prosauropoda
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.
Classificati ...
" by von Huene,[ a placement that was accepted by most authors.][ Before the advent of ]cladistics
Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups (" clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived char ...
in paleontology during the 1980s, with its emphasis on monophyletic
In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...
groups (clade
A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
s), Plateosauridae was defined loosely, as large, broad-footed, broad-handed forms with relatively heavy skulls, unlike the smaller " anchisaurids" and sauropod-like " melanorosaurids".[ Reevaluation of "prosauropods" in light of the new methods of analysis led to the reduction of Plateosauridae. 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'' is a genus of unaysauridae, unaysaurid sauropodomorpha, sauropodomorph herbivore dinosaur. Discovered in southern Brazil, in the geopark of Paleorrota, in 1998, and announced in a press conference on Thursday, December 3, 2004, it ...
''.[ Of these, ''Sellosaurus'' is probably another junior synonym of ''Plateosaurus''.][
]
Basal sauropodomorph phylogeny
A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spec ...
simplified after Yates, 2007. This is only one of many proposed 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 ...
s for basal sauropodomorphs. Some researchers do not agree that plateosaurs were the direct ancestors of sauropods.
Palaeobiology
Posture and gait
Practically every imaginable posture has been suggested for ''Plateosaurus'' in the scientific literature at some point. Von Huene assumed digitigrade
In terrestrial vertebrates, digitigrade () locomotion is walking or running on the toes (from the Latin ''digitus'', 'finger', and ''gradior'', 'walk'). A digitigrade animal is one that stands or walks with its toes (metatarsals) touching the groun ...
bipedality
Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning 'two feet' (from Latin ''bis'' 'double' a ...
with erect hind limbs for the animals he excavated at Trossingen, with the backbone held at a steep angle (at least during rapid locomotion).[ In contrast, Jaekel, the main investigator of the Halberstadt material, initially concluded that the animals walked quadrupedally, like lizards, with a sprawling limb position, ]plantigrade
151px, Portion of a human skeleton, showing plantigrade habit
In terrestrial animals, plantigrade locomotion means walking with the toes and metatarsals flat on the ground. It is one of three forms of locomotion adopted by terrestrial mammals. T ...
feet, and laterally undulating the body.[ Only a year later, Jaekel instead favoured a clumsy, ]kangaroo
Kangaroos are four marsupials from the family Macropodidae (macropods, meaning "large foot"). In common use the term is used to describe the largest species from this family, the red kangaroo, as well as the antilopine kangaroo, eastern gre ...
-like hopping,[ a change of heart for which he was mocked by German ]zoologist
Zoology ()The pronunciation of zoology as is usually regarded as nonstandard, though it is not uncommon. is the branch of biology that studies the Animal, animal kingdom, including the anatomy, structure, embryology, evolution, Biological clas ...
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
A Lagerstätte (, from ''Lager'' 'storage, lair' '' Stätte'' 'place'; plural ''Lagerstätten'') is a sedimentary deposit that exhibits extraordinary fossils with exceptional preservation—sometimes including preserved soft tissues. These for ...
, 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),][ and Wellnhofer insisted that the tail curved strongly downward, making a bipedal posture impossible.][ However, Moser showed that the tail was in fact straight.
]
The bipedal-quadrupedal consensus was changed by a detailed study of the forelimbs of ''Plateosaurus'' by Bonnan and Senter (2007), which clearly showed that ''Plateosaurus'' was incapable of pronating its hands.[ The pronated position in some museum mounts had been achieved by exchanging the position of ]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 ...
and 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 ...
in the elbow. The lack of forelimb pronation meant that ''Plateosaurus'' was an obligate (i.e. unable to walk in any other way) 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 centre of mass
In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weighted relative position of the distributed mass sums to zero. This is the point to which a force may ...
rests squarely over the hind limbs.[
''Plateosaurus'' shows a number of ]cursorial
A cursorial organism is one that is adapted specifically to run. An animal can be considered cursorial if it has the ability to run fast (e.g. cheetah) or if it can keep a constant speed for a long distance (high endurance). "Cursorial" is often u ...
adaptations, including an erect hind limb posture, a relatively long lower leg, an elongated metatarsus
The metatarsal bones, or metatarsus, 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 med ...
and a digitigrade foot posture.[ However, in contrast to ]mammal
Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...
ian cursors, the moment arms of the limb extending muscles are short, especially in the ankle, where a distinct, moment arm-increasing tuber on the calcaneum
In humans and many other primates, the calcaneus (; from the Latin ''calcaneus'' or ''calcaneum'', meaning heel) or heel bone is a bone of the tarsus of the foot which constitutes the heel. In some other animals, it is the point of the hock.
St ...
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 may refer to:
Science and technology
*Limb (anatomy), an appendage of a human or animal
*Limb, a large or main branch of a tree
*Limb, in astronomy, the curved edge of the apparent disk of a celestial body, e.g. lunar limb
*Limb, in botany, ...
retraction 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
A crown is a traditional form of head adornment, or hat, worn by monarchs as a symbol of their power and dignity. A crown is often, by extension, a symbol of the monarch's government or items endorsed by it. The word itself is used, partic ...
is similar to that of modern herbivorous or omnivorous iguana
''Iguana'' (, ) is a genus of herbivorous lizards that are native to tropical areas of Mexico, Central America, South America, and the Caribbean. The genus was first described in 1768 by Austrian naturalist Josephus Nicolaus Laurenti in his bo ...
s. The maximum width of the crown was greater than that of the root for the teeth of most "prosauropods", including ''Plateosaurus''; this results in a cutting edge similar to those of extant herbivorous or omnivorous reptiles.[ Paul Barrett proposed that prosauropods supplemented their mostly herbivorous diets with small prey or ]carrion
Carrion () is the decaying flesh of dead animals, including human flesh.
Overview
Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters (or scavengers) include crows, vultures, c ...
, thus making them omnivores.[
So far, no fossil of ''Plateosaurus'' has been found with ]gastrolith
A gastrolith, also called a stomach stone or gizzard stone, is a rock held inside a gastrointestinal tract. Gastroliths in some species are retained in the muscular gizzard and used to grind food in animals lacking suitable grinding teeth. In othe ...
s (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 archosaurs (pterosaurs, crocodiles, alligators, dinosaurs, birds), earthworms, some gastropods, so ...
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'' ( ; "parrot lizard") is a genus of extinct ceratopsian dinosaur from the Early Cretaceous of what is now Asia, existing between 126 and 101 million years ago. It is notable for being the most species-rich non-avian dinosaur gen ...
''.[
]
Life history and metabolism
Similar to all non-avian dinosaurs studied to date, ''Plateosaurus'' grew in a pattern that is unlike that of both extant
Extant is the opposite of the word extinct. It may refer to:
* Extant hereditary titles
* Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English
* Extant taxon, a taxon which is not extinct, ...
mammals and birds. In the closely related sauropods with their typical dinosaurian physiology, growth was initially rapid, continuing somewhat more slowly 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 (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...
rate (i.e. ectotherm
An ectotherm (from the Greek () "outside" and () "heat") is an organism in which internal physiological sources of heat are of relatively small or of quite negligible importance in controlling body temperature.Davenport, John. Animal Life a ...
y), and is called "developmental plasticity".[ (Note that is not the same as neural ]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. Much like neuroplasticity or brain plasticity, develo ...
).
''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' (16 ft) total length, while others reached . However, the bone microstructure indicates rapid growth, as in sauropods and extant mammals, which suggests endothermy
An endotherm (from Greek ἔνδον ''endon'' "within" and θέρμη ''thermē'' "heat") is an organism that maintains its body at a metabolically favorable temperature, largely by the use of heat released by its internal bodily functions inste ...
. ''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.[ 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 growing rapidly at 18 years. The oldest individual found was 27 years and still growing; most individuals were between 12 and 20 years old.][ However, some 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 long, it is not possible to deduce a complete ]ontogenetic
Ontogeny (also ontogenesis) is the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the egg to adult. The term can also be used to refer to the st ...
series for ''Plateosaurus'' or determine the growth rate of animals less than 10 years of age.[
Comparisons between the scleral rings and estimated orbit size of ''Plateosaurus'' and modern birds and reptiles suggest that it may have been ]cathemeral
Cathemerality, sometimes called metaturnality, is an organismal activity pattern of irregular intervals during the day or night in which food is acquired, socializing with other organisms occurs, and any other activities necessary for livelihood ar ...
, active throughout the day and night, possibly avoiding the midday heat.[
]
Palaeoecology
''Plateosaurus gracilis'', the older species, is found in the Löwenstein Formation
The Löwenstein Formation (Stubensandstein in Baden-Württemberg, Burgsandstein in Bavaria) is a lithostratigraphic formation of the Keuper in Germany. It is underlain by the Mainhardt Formation and overlain by the Trossingen Formation. It dates ...
(Lower Norian). ''P. trossingensis'' stems from the upper Löwenstein Formation (Upper Norian), and ''P. longiceps'' the Trossingen Formation
The Trossingen Formation, formerly the Knollenmergel, is a geological formation in Germany and Switzerland. It dates back to the late Norian- Rhaetian.Weishampel et al., 2004, pp.521–525
Vertebrate paleofauna
See also
* List of dinosa ...
(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 ...
), and equivalently aged rock units. ''Plateosaurus'' thus lived probably from approximately 214 to 204 million years ago.[
]
Taphonomy
The taphonomy
Taphonomy is the study of how organisms decay and become fossilized or preserved in the paleontological record. The term ''taphonomy'' (from Greek , 'burial' and , 'law') was introduced to paleontology in 1940 by Soviet scientist Ivan Efremov t ...
(burial and fossilisation process) of the three main ''Plateosaurus'' sites—Trossingen, Halberstadt and Frick—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 ]theropods
Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally ca ...
have been found at all three sites, as well as remains of the early turtle ''Proganochelys''.[ 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 dorsal (top) 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
Aeolian commonly refers to things related to either of two Greek mythological figures:
* Aeolus (son of Hippotes), ruler of the winds
* Aeolus (son of Hellen), son of Hellen and eponym of the Aeolians
* Aeolians, an ancient Greek tribe thought to ...
, 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, while heavy individuals got stuck and died.][
A different school of thought developed almost half a century later, with palaeontologist ]David Weishampel
Professor David Bruce Weishampel (born November 16, 1952) is an American palaeontologist in the Center for Functional Anatomy and Evolution at Johns Hopkins University School of Medicine. Weishampel received his Ph.D. in Geology from the Univers ...
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 theorising 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
The University of Tübingen, officially the Eberhard Karl University of Tübingen (german: Eberhard Karls Universität Tübingen; la, Universitas Eberhardina Carolina), is a public research university located in the city of Tübingen, Baden-Wü ...
,[ 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.][
]
Mud-miring trap
A detailed re-assessment of the taphonomy by palaeontologist Martin Sander of the University of Bonn
The Rhenish Friedrich Wilhelm University of Bonn (german: Rheinische Friedrich-Wilhelms-Universität Bonn) is a public research university located in Bonn, North Rhine-Westphalia, Germany. It was founded in its present form as the ( en, Rhine U ...
, Germany, 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 is an active paleontological research site in urban Los Angeles. Hancock Park was formed around a group of tar pits where natural asphalt (also called asphaltum, bitumen, or pitch; ''brea'' in Spanish) has seeped up from the gro ...
, 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, scavenging theropods
Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally ca ...
were not trapped due to their lower body weights, combined with proportionally larger feet. There is no indication of herding, or of catastrophic burial of such a herd, or catastrophic accumulation of animals that previously died isolated elsewhere.[
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Notes
References
External links
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3D skull models of ''Plateosaurus''
at Sketchfab
Sketchfab is a 3D modeling platform website to publish, share, discover, buy and sell 3D, VR and AR content. It provides a viewer based on the WebGL and WebXR technologies that allows users to display 3D models on the web, to be viewed on a ...
3D walking skeletal model of ''Plateosaurus''
at Sketchfab
Sketchfab is a 3D modeling platform website to publish, share, discover, buy and sell 3D, VR and AR content. It provides a viewer based on the WebGL and WebXR technologies that allows users to display 3D models on the web, to be viewed on a ...
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Plateosauridae
Clawed herbivores
Late Triassic genus first appearances
Late Triassic genus extinctions
Late Triassic dinosaurs of Europe
Fossils of Germany
Fossils of Switzerland
Fossils of Norway
Fossil taxa described in 1837
Taxa named by Christian Erich Hermann von Meyer