Plateosaurus

Plateosaurus
Temporal range: Late Triassic, 214–204 Ma
Plateosaurus Skelett 2.jpg
Mounted skeleton of P. engelhardti (GPIT "Skelett 2"), consisting of two individual specimens from the Trossingen Formation, museum of the Institute for Geosciences (GPIT) of the Eberhard-Karls-University Tübingen, Germany
Scientific classification edit
Kingdom:Animalia
Phylum:Chordata
Clade:Dinosauria
Suborder:Sauropodomorpha
Family:Plateosauridae
Genus:Plateosaurus
von Meyer, 1837
Type species
Plateosaurus engelhardti
von Meyer, 1837
Species
  • P. engelhardti von Meyer, 1837
  • P. gracilis (von Huene, 1907–08 [originally Sellosaurus])
Synonyms

Plateosaurus (probably meaning "broad lizard", often mistranslated as "flat lizard") is a genus of plateosaurid dinosaur that lived during the Late Triassic period, around 214 to 204 million years ago, in what is now Central and Northern Europe and Greenland, North America. Plateosaurus is a basal (early) sauropodomorph dinosaur, a so-called "prosauropod". As of 2011, two species are recognised: the type species P. engelhardti from the late Norian and Rhaetian, 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 of plateosaurid dinosaurs. Similarly, there are a plethora of synonyms (invalid duplicate names) at the genus level.

Discovered in 1834 by Johann Friedrich Engelhardt and described three years later by Hermann von Meyer, Plateosaurus was the fifth named dinosaur genus that is still considered valid. Although it had been described before Richard Owen 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, Germany, has led to the nickname Schwäbischer Lindwurm (Swabian lindworm).

Plateosaurus was a bipedal herbivore 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 4.8 and 10 metres (16 and 33 ft) long and weighed between 600 and 4,000 kilograms (1,300 and 8,800 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 and palaeontological evidence, but have become the paradigm of public opinion. Since 1980 the taxonomy (relationships), taphonomy (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.

Description

Restoration of P. engelhardti

Plateosaurus had the typical body shape of a herbivorous bipedal dinosaur: a small skull, a long and flexible neck composed of 10 cervical vertebrae, a stocky body, and a long, mobile tail composed of at least 40 caudal vertebrae.[1][2][3] The arms of Plateosaurus were very short, even compared to most other "prosauropods". However, they were strongly built, with hands adapted for powerful grasping.[2][4] The shoulder girdle was narrow (often misaligned in skeletal mounts and drawings),[4] with the clavicles (collar bones) touching at the body's midline,[2] as in other basal sauropodomorphs.[5] The hind limbs were held under the body, with slightly flexed knees and ankles, and the foot was digitigrade, meaning the animal walked on its toes.[2][6][7] The proportionally long lower leg and metatarsus show that Plateosaurus could run quickly on its hind limbs.[2][4][6][7] The tail of Plateosaurus was typically dinosaurian, muscular and with high mobility.[4]

Side view of a skull and the anterior part of the neck. The skull is rectangular, nearly three times as long as it was high, with an almost rectangular lateral temporal foramen at the back. The large, round orbit (eye socket), the sub-triangular antorbital fenestra and the oval naris are of almost equal size. The lower jaw is shallow, and has a large process extending far behind the jaw joint. The teeth are small and form long rows.
P. engelhardti skull cast, Royal Ontario Museum

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 (eye socket), the sub-triangular antorbital fenestra and the oval naris (nostril) are of almost equal size.[1][2][8] The jaws carried many small, leaf-shaped, socketed teeth: 5 to 6 per premaxilla, 24 to 30 per maxilla, and 21 to 28 per dentary (lower jaw).[1][2][8] The thick, leaf-shaped, bluntly serrated tooth crowns were suitable for crushing plant material.[1][2][8] The low position of the jaw joint gave the chewing muscles great leverage, so that Plateosaurus could deliver a powerful bite.[8] These features suggest that it fed primarily to exclusively on plants.[8] Its eyes were directed to the sides, rather than the front, providing all-round vision to watch for predators.[1][2][8] Some fossil skeletons have preserved sclerotic rings (rings of bone plates that protect the eye).[1][2][8]

A silhouette drawing of Plateosaurus in lateral view, and a human male. The dinosaur is depicted as a biped. The 1.8-metre-tall (5.9 ft) human does not reach hip height of Plateosaurus.
Size comparison between a maximum size individual of P. engelhardti and a human

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.[4] This is a typical value for birds, but not for mammals,[9] and indicates that Plateosaurus probably had an avian-style flow-through lung,[4] 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.[10][11] Combined with evidence from bone histology[12][13] this indicates that Plateosaurus was endothermic.[13][14]

The type species of Plateosaurus is P. engelhardti.[15] Adults of this species reached 4.8 to 10 metres (16 to 33 ft) in length,[13] and ranged in mass from 600 to 4,000 kilograms (1,300 to 8,800 lb).[7] The geologically older species, P. gracilis (formerly named Sellosaurus gracilis), was somewhat smaller, with a total length of 4 to 5 metres (13 to 16 ft).[16]

Other Languages
Afrikaans: Plateosourus
azərbaycanca: Sellosaurus
български: Платеозаври
català: Plateosaure
čeština: Plateosaurus
Deutsch: Plateosaurus
español: Plateosaurus
euskara: Plateosaurus
فارسی: پلاتیوسور
français: Platéosaure
galego: Plateosaurus
hrvatski: Plateosaur
Bahasa Indonesia: Plateosaurus
italiano: Plateosaurus
ქართული: პლატეოზავრი
magyar: Plateosaurus
Nederlands: Plateosaurus
polski: Plateozaur
português: Plateosaurus
română: Plateosaurus
русский: Платеозавр
Simple English: Plateosaurus
slovenčina: Plateosaurus
српски / srpski: Plateosaurus
srpskohrvatski / српскохрватски: Plateosaur
svenska: Plateosaurus
Türkçe: Plateosaurus
українська: Платеозавр
Tiếng Việt: Plateosaurus
中文: 板龍屬