Non-avian

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 ...

and

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s are frequently found in a characteristic posture consisting of head thrown back, tail extended, and mouth wide open. The cause of this posture—often called a "death pose"—has been a matter of scientific debate. Traditional explanations ranged from strong

ligament A ligament is the fibrous connective tissue that connects bones to other bones. It is also known as ''articular ligament'', ''articular larua'', ''fibrous ligament'', or ''true ligament''. Other ligaments in the body include the: * Peritoneal l ...

s in the animal's neck

desiccating Desiccation () is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. ...

and contracting to draw the body into the pose, to water currents arranging the remains in the position. Faux and Padian suggested in 2007 that the live animal was suffering opisthotonus during its death throes, and that the pose is not the result of any post-mortem process at all. They also reject the idea of water as responsible for randomly arranging the bodies in a "death pose", as different parts of the body and the limbs can be in different directions, which they found unlikely to be the result of moving water.Padian K & Faux M (2007)
"The opisthotonic posture of vertebrate skeletons: post-mortem contraction or death throes?"
''Paleobiology'' 33(2): p. 201-226. They also found that the claim that drying out of ligaments would make the position does not seem believable either. A study conducted by Alicia Cutler, Brooks B. Britt, and colleagues from

Brigham Young University Brigham Young University (BYU, sometimes referred to colloquially as The Y) is a private research university in Provo, Utah. It was founded in 1875 by religious leader Brigham Young and is sponsored by the Church of Jesus Christ of Latter-d ...

in Provo, Utah, suggests that the pose is a result of submersion in water after death. Seconds after placing chicken carcasses in water, the bodies assumed the "death pose." The reduction of friction to allow ligaments and tendons to contract to their typical positions causes dorsoflexion of the head and tail of the animal. They also found that the chickens' claws contracted, likely due to the same cause (reduction of friction in water allows ligaments to return to their original positions, and death releases muscle tension that would have held the neck and claws in different positions in life). The experiment was replicated with an emu, which produced the same results. When the intervertebral ligaments of the chickens' necks were cut, they did not assume the death pose. In 2012, paleontologists Achim G. Reisdorf and Michael Wuttke published a study regarding death poses. According to the conclusions of this study, the so-called "opisthotonic posture" is not the result of a cerebral illness creating muscle spasms, and also not of a rapid burial. Rather, peri-mortem submersion resulted in

buoyancy Buoyancy (), or upthrust, is an upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus the ...

that enabled the Ligamentum elasticum to pull the head and tail back. Reisdorf, A.G. & Wuttke, M. (2012)
"Re-evaluating Moodie’s Opisthotonic-Posture Hypothesis in Fossil Vertebrates Part I: Reptiles—the taphonomy of the bipedal dinosaurs ''Compsognathus longipes'' and ''Juravenator starki'' from the Solnhofen Archipelago (Jurassic, Germany)"
''Palaeobiodiversity and Palaeoenvironments'', 92(1): 119-168. . Image:Ornithomimus edmontonicus.jpg, '' Ornithomimus'' Image:Struthiomimus skeleton jconway.jpg, ''

Struthiomimus ''Struthiomimus'' (meaning "ostrich mimic", from the Greek στρούθειος/''stroutheios'' meaning "of the ostrich" and μῖμος/''mimos'' meaning "mimic" or "imitator") is a genus of ornithomimid dinosaurs from the late Cretaceous of No ...

''. Image:Gorgosaurus death pose.jpg, ''

Gorgosaurus ''Gorgosaurus'' ( ; ) is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period (Campanian), between about 76.6 and 75.1 million years ago. Fossil remains have been found in the Ca ...

''. Image:Archaeopteryx_lithographica_(Berlin_specimen).jpg, ''

Archaeopteryx ''Archaeopteryx'' (; ), sometimes referred to by its German name, "" ( ''Primeval Bird''), is a genus of bird-like dinosaurs. The name derives from the ancient Greek (''archaīos''), meaning "ancient", and (''ptéryx''), meaning "feather" ...

''. Image:Messelornis.JPG, ''

Messelornis ''Messelornis'', also known as the Messel rail, is an extinct genus of gruiform bird, closely related to modern rails. It is the most abundant bird from the Messel Lagerstätte, representing roughly half of all Messel bird fossils with more than ...

''. Image:Sapeornis chaoyangensis.JPG, ''

Sapeornis ''Sapeornis'' is a monotypic genus of avialan which lived during the early Cretaceous period ( late Barremian to early Aptian, roughly 125-120 mya). ''Sapeornis'' contains only one species, ''Sapeornis chaoyangensis''. Description ''Sapeornis ...

''. Image:9119 - Milano, Museo storia naturale - Scipionyx samniticus - Foto Giovanni Dall'Orto 22-Apr-2007.jpg, ''

Scipionyx ''Scipionyx'' ( ) was a genus of theropod dinosaur from the Early Cretaceous of Italy, around 113 million years ago. There is only one fossil known of ''Scipionyx'', discovered in 1981 by an amateur paleontologist and brought to the attention ...

''. Image:Camarasaurus_lentus_Carnegie.jpg, ''

Camarasaurus ''Camarasaurus'' ( ) was a genus of quadrupedal, herbivorous dinosaurs and is the most common North American sauropod fossil. Its fossil remains have been found in the Morrison Formation, dating to the Late Jurassic epoch ( Kimmeridgian to ...

References

{{Death Dinosaurs Death Biostratinomy

See also

References