Timeline of stegosaur research

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Skeletal mount of Stegosaurus.

This timeline of stegosaur research is a chronological listing of events in the

Alfred Sherwood Romer implemented the modern use of the name Stegosauria as specifically pertaining to the plate-backed and spike-tailed dinosaurs.[1]

From the time of their earliest description, the chief mystery surrounding stegosaurs was the function of their distinctive back plates. Marsh originally interpreted them as being plates of armor that would protect against predators. In

Charles Whitney Gilmore disagreed in 1914 and argued that the only protection a stegosaur could gain from its plates was to appear intimidatingly larger to potential predators. Nearly forty years later, Davitashvili argued that the plates were too fragile to be used for defense and instead used to attract mates and signal the stegosaur's rank in a social hierarchy.[3]

In the late

mammals,[5] in which case the plates may have served primarily to shed heat rather than gain it. In the late 1980s Buffrenil and others revived the idea that stegosaur plates were display structures, an interpretation that would continue to find favor from researchers like Main and colleagues into the 21st century.[4]

19th century

Regnosaurus jaw fragments.
Omosaurus armatus
.

1840s

1841

  • Regnosaurus northamptoni.[6]

1870s

Othniel Charles Marsh's reconstruction of Stegosaurus.

1874

  • Craterosaurus pottonensis.[7]

1875

  • Omosaurus armatus.[7]

1876

  • Owen described the new species
    Anthodon serrarius.[6]

1877

1878

  • Hypsirhophus discurus.[6]

1879

1880s

Sir Richard Owen
's 1875 monograph.
Stegosaurus stenops
.

1880

1881

  • Marsh described the new genus and species
    Diracodon laticeps.[6]

1884

  • Hulke reported a Cretaceous stegosaur pubis from England.[1]

1887

1890s

1891

  • Marsh provided an illustrated description of
    Stegosaurus ungulatus
    , with a row of erect plates running along the centre of its back.

1893

  • Omosaurus phillipsi.[6]

20th century

1900s

Artist's restoration of Dacentrurus.
Dacentrurus spike and limb bones.

1901

1902

  • Frederick Augustus Lucas described the new genus Dacentrurus to house the species Omosaurus armatus.[7]

1905

  • Loomis argued that the plates adorning the backs of stegosaurs were maladaptive traits that sapped their vigor and signaled their impending extinction.[8] Similar arguments would later be extended to the extinction of the dinosaurs overall by Woodward in 1910.[9]

1910s

1910

  • Omosaurus vetustus.[6]
  • Richard Swann Lull followed Marsh's interpretation of Stegosaurus plates as armor and its tail spines as "defensive" weapons.[3]

1911

  • Stegosaurus priscus.[7]

1912

  • Palaeoscincus africanus.[6]

1914

Artist's restoration of Kentrosaurus.
  • Stegosaurus longispinus.[6] He agreed with previous workers that Stegosaurus used its spines to protect itself, but dismissed the idea that its plates functioned as armor. However, Gilmore conceded that the plates may have helped protect it by making it appear intimidatingly large to predators.[3]

1915

  • Kentrosaurus aethiopicus.[7]

1916

1920s

Ankylosaurs (pictured) were first distinguished from stegosaurs in 1927 by Romer.

1924

  • Hennig described the distribution of Kentrosaurus bones in Quarry St at
    Tendaguru, Tanzania. He observed that at one place in the quarry multiple sacra were found near each other, while another area of the quarry contained limb bones, and yet another preserved vertebrae.[10]

1927

  • ankylosaurs. As the Stegosauria originally included all armored dinosaurs, Romer's distinction marked the beginning of the modern use of the name to refer to the plate-backed and spike-tailed dinosaurs.[1]
Skull of Paranthodon.

1929

  • Nopcsa erected the new taxon Paranthodon oweni for the same material as Palaeoscincus africanus.[6]

1940s

1944

1950s

Chialingosaurus kuani
.

1951

  • Young described the new genus and species
    Chialingosaurus kuani.[7]

1957

1960s

Fossils of Lexovisaurus.

1961

  • social hierarchy.[3]

1963

  • Nicholas Hotton III proposed that stegosaur plates could be moved by flexing muscles in the skin, allowing the plates to function defensively, discouraging attacks from either above or the side depending on the plates' position at any given time.[3]

1966

1970s

Artist's restoration of Wuerhosaurus.

1973

  • Wuerhosaurus homheni.[6]

1976

Artist's restoration of Tuojiangosaurus.
  • James O. Farlow and others proposed that stegosaur plates were used to help regulate the animal's body temperature. Their alternating placement along its spine would allow them to dissipate its body heat by acting as forced-convection fins, the researchers argued.[4]

1977

  • Dong and others described the new genus and species
    Tuojiangosaurus multispinus.[6]

1978

  • Robert T. Bakker proposed that contrary to the prevailing interpretation of stegosaurs as low browsers, they were actually high browsers who fed on high foliage by rearing up on their hind limbs and propping themselves up in this position with their tail.[3]
  • Walter Coombs argued based on their limb anatomy that stegosaurs were graviportal animals.[3]

1979

  • Dravidosaurus blanfordi based on fragmentary material assumed to include a skull and plates. Since it was dated to the Coniacian it would have been the most recent known surviving stegosaur taxon. The authors also reported the existence of Maastrichtian stegosaur remains, but they did not describe these fossils.[1]
  • Michael Seidel argued that while the plates of Stegosaurus were used to help regulate its body temperature, they were actually used to absorb heat rather than lose it as argued by Farlow and others in 1976.[4]

1980s

Huayangosaurus taibaii
.

1980

  • droughts. The stegosaur Kentrosaurus was present there, although not especially common. Its local fossil record consists largely of "medium-sized" members of the species.[10]

1981

Skeletal mount of Kentrosaurus.
  • Peter Malcolm Galton observed that stegosaurs were uncommon during the Cretaceous period.[1]

1982

  • Dong,
    Huayangosaurus taibaii as well as the Huayangosauridae.[7]
  • Nikolaï Spassov argued that the plates of stegosaurs were used as display structures in competitions over mates. Their orientation made them best suited to being viewed from the side.[3]
  • Galton studied the growth and development of Stegosaurus.[11]
  • Galton found that Kentrosaurus came in two varieties, one with an extra sacral rib. He speculated that this morph with the extra sacral rib was the female and the other morph lacking the rib was male.[11]
Chungkingosaurus jiangbeiensis
.

1983

1984

  • Giuseppe Leonardi attributed Early Cretaceous footprints of the ichnogenus Caririchnium to stegosaurs.[1]
  • Zhou observed that the Bathonian to Callovian Huayangosaurus was among the oldest known stegosaur fossils.[1]
  • Sharpey's fibers that anchored it within the animal's skin were symmetrical it could not be moved. They also argued that there was no physical evidence in the anatomy of the plate to suggest that it was covered by horn in life. The researchers dismissed the idea that the plates could function as armor on the grounds that they were too fragile. They also doubted that the plates were used as threat displays for intimidation because "they could not unfold suddenly". They found that the plates were more likely used as sexual displays to attract mates or help regulate the animal's body temperature. They proposed that the plates were covered by a skin dense with blood vessels that helped exchange heat by both convection and radiation. They argued that their hypothesis was compatible with both major competing interpretations of dinosaur thermophysiology since if Stegosaurus was cold-blooded the plates could be used to absorb heat while if it was warm-blooded the plates could shed the excess heat that its body produced.[4]
Stegosaurus back plate.

1985

  • Daniel Brinkman and Conway studied the bone texture and mineralogy of stegosaur plates.[4]
  • Galton observed that the plates of Lexovisaurus were large, thin, and rich in blood vessels like Stegosaurus plates are.[4]

1986

  • Robert Bakker expanded on his hypothesis that stegosaurs were high browsers that fed while rearing up on their hindlimbs. He also supported the idea that stegosaur plates were mobile armor that could defend the animal's back or flanks depending on what angle to which they were flexed. He also argued that the anatomy of the tail of Stegosaurus rendered it more flexible than that of other bird-hipped dinosaurs, whose tails were often stiffened by bony tendons. He hypothesized that Stegosaurus could "push off" using its massive chest muscles to turn its body about its back legs.[3]
  • Buffrénil and others studied the histology of a Stegosaurus plate. They concluded that since the Sharpey's fibers that anchored it within the animal's skin was symmetrical that it couldn't be moved. They also argued that there was no physical evidence in the anatomy of the plate to suggest that it was covered by horn in life. The researchers dismissed the idea that the plates could function as armor on the grounds that they were too fragile. They also doubted that the plates were used as threat displays for intimidation because "they could not unfold suddenly". They found that the plates were more likely used as sexual displays to attract mates or help regulate the animal's body temperature. They proposed that the plates were covered by a skin dense with blood vessels that helped exchange heat by both convection and radiation. They argued that their hypothesis was compatible with both major competing interpretations of dinosaur thermophysiology since if Stegosaurus was cold-blooded the plates could be used to absorb heat while if it was warm-blooded the plates could shed the excess heat that its body produced.[4]
Tracks supposedly left by stegosaurs in South America may actually have been left by hadrosaurs.

1987

  • Martin Lockley disputed Leonardi's attribution of the Brazilian Caririchnium tracks to stegosaurs. Instead, Lockley concluded that they were left by hadrosaurs walking on all fours.[1]

1987

  • Farlow examined the possible distinct feeding strategies exploited by stegosaurs that enabled them to flourish alongside other ornithischians during the Middle and Late Jurassic.[3]

1987

  • Malcolm James Coe and others disputed Robert Bakker's reinterpretation of stegosaurs as high browsers, observing that even if stegosaurs were capable of rearing like Bakker portrays, that it doesn't imply it was their normal feeding posture since elephants are also physically capable of standing on their hind limbs but do not feed in this stance. Instead, Coe and the other researchers supported the traditional view of Stegosaurus as feeding on plants one meter high or less.[3]

1990s

Wuerhosaurus back plate

1990

  • Dong published the new genus and species name
    Monkonosaurus lawulacus but attributed it to Zhou.[6]

1991

  • Dayton reported possible Early Cretaceous stegosaur footprints from Australia.[1]

1992

  • Boneham and Forsey reported stegosaur armor and vertebrae from the Early Bajocian of England. These are among the oldest known stegosaur bones.[1]

1993

  • Dong described the new species
    Wuerhosaurus ordosensis.[6]
  • Kenneth Carpenter uses Thagomizer formally to describe stegosaur tail spikes, moving the term from humor to informal designation of the anatomy.

1994

  • Sara Metcalf and Rachel Walker reported a stegosaur tooth from the early Bajocian of England. It is among the oldest known stegosaur remains.[1]
Dravidosaurus may have actually been a plesiosaur.

1996

1997

  • Chatterjee expanded on his argument that Dravidosaurus was actually a plesiosaur rather than a stegosaur.[1]
  • Thulborn reported possible Early Cretaceous stegosaur footprints from Australia.[1]
  • Fortelius reported wear facets on stegosaur teeth caused by physical interactions between teeth.[3]

1998

Stegosaurus tail spikes.
  • Paul Sereno proposed a stem-based definition of Stegosauria that included all taxa more closely related to Stegosaurus than to Ankylosauria.[13]
  • Kenneth Carpenter disputed Bakker's reinterpretation of Stegosaurs as high browsers. He argued that the plates along the animal's tail made it too rigid to be used as the third "leg" of the tripodal stance needed to support it in the rearing posture Bakker imagined stegosaurs adopted to reach high foliage.[3] He noted that the first vertebra in the tail had a wedge shape that fit under a backward-facing projection of bone from the top of the last vertebra in the pelvis. This configuration would have held the tail out straight from the animal's body. Its other tail vertebrae show anatomical evidence for ligaments that would have assisted in keeping the tail aloft. Carpenter concluded that while the plates limited the mobility between individual vertebrae, the tail itself had enough range of motion to swing its spiked tip to an angle exceeding ninety degree from a resting position.[3]

1999

  • Sereno continued to use the stem-based definition of Stegosauria he proposed in 1998.[13]
  • Jean Le Loeuff and others reported some fossil footprints from France that may have been left behind by stegosaurs. As these tracks date back to the Hettangian, they may represent the oldest known stegosaur fossils.[1]
  • Wolf-Dieter Heinrich observed that stegosaur bones were common in Quarry X at Tendaguru, Tanzania. He interpreted the deposit as resulting from the gradual accumulation of remains in a fresh-to-brackish water environment.[14]
  • turtles.[3]
  • Galton argued that stegosaurs were
    sexually dimorphic and the females had extra rib in their sacra.[11]

21st century

2000s

Main and others argued that Stegosaurus did not use its plates to regulate its body temperature.

2000

Hesperosaurus mjosi
.
  • artiodactyls unrelated to heat regulation like horns and frills often show similar amount of vasculature to stegosaur plates.[4]

2001

  • Paul Michael Barrett found further anatomical support for the hypothesis that stegosaur jaws were only capable of opening and closing in a straight up-an-down fashion that precluded the complex chewing motions seen in some other herbivorous dinosaur groups. He concluded that the tooth-tooth wear facets reported by Popowics and Fortelius only formed as a result of teeth growing in at slightly different angles rather than tooth-tooth contact occurring as part of the animals' natural feeding strategy.[3]
  • Carpenter,
    Hesperosaurus mjosi.[7]
  • Neil Donald Lewis Clark reported the discovery of near ends of a radius and ulna from Early Bajocian rocks in Scotland. Although they might be ankylosaur fossils, these are likely to be some of the oldest known stegosaur bones.[1]
  • Éric Buffetaut and others reported a stegosaur vertebra from Thailand. This was the first scientifically recognized stegosaur fossil from southeast Asia.[1]
  • William Blows reported Cretaceous stegosaur dermal armor from England.[1]
  • Darren Naish and David Martill reported Cretaceous stegosaur dermal armor from England.[1]
  • Galton and Paul Upchurch accepted Dravidosaurus as a stegosaur not taking notice of arguments made by Chatterjee and Rudma in the 1990s that it was actually a plesiosaur.[1]

2004

  • Dravidosaurus blanfordi
    as a stegosaur/plesiosaur chimera.

2007

  • Jiangjunosaurus junggarensis.[15]

2008

2009

Artist's restoration of Miragaia longicollum.

2010s

2015

  • Robert P. Cameron, John A. Cameron and Stephen M. Barnett recognised that Stegosaurus exhibited exterior chirality and highlighted the need to distinguish a specimen from its distinct, hypothetical mirror-image form.[18]

2016

  • Peter M. Galton and Kenneth Carpenter described the new genus Alcovasaurus for the species "Stegosaurus" longispinus.[19]
  • Cameron, Cameron, and Barnett published another paper on exterior chirality in Stegosaurus.[20]

2018

  • Tumanova and Alifanov described the new genus and species
    Mongolostegus exspectabilis.[21]

2019

  • A study on the morphological diversity of stegosaurs through the evolutionary history of the group will be published by Romano (2019).[22]
  • A study on pathological characteristics of left femur of a specimen of Gigantspinosaurus sichuanensis from the Late Jurassic of China will be published by Hao et al. (2019), who interpret this specimen as probably affected by bone tumor.[23]

2020s

2020

  • Maidment and others described the new genus and species
    Adratiklit boulahfa.[24]

2022

See also

Footnotes

  1. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab Galton and Upchurch (2004); "Introduction", page 343.
  2. ^ Galton and Upchurch (2004); "Table 16.1: Stegosauria", pages 344-345.
  3. ^ a b c d e f g h i j k l m n o p q r s Galton and Upchurch (2004); "Paleoecology and Behavior", page 361.
  4. ^ a b c d e f g h i Galton and Upchurch (2004); "Paleoecology and Behavior", page 362.
  5. ^ Chinsamy and Hillenius (2004); "Introduction", page 643.
  6. ^ a b c d e f g h i j k l m n o p q r Galton and Upchurch (2004); "Table 16.1: Stegosauria", page 345.
  7. ^ a b c d e f g h i j k l m n o p q r Galton and Upchurch (2004); "Table 16.1: Stegosauria", page 344.
  8. ^ Benton (1990); "Racial Senility", page 379.
  9. ^ For Woodward's speech, see Benton (1990); "Racial Senility", page 379. For a definition and discussion of racial senility, see "Post-Darwinian Interpretations", page 376.
  10. ^ a b c d Galton and Upchurch (2004); "Taphonomy", page 360.
  11. ^ a b c d Galton and Upchurch (2004); "Paleoecology and Behavior", page 360.
  12. ^ Galton and Upchurch (2004); "Introduction", page 343. For the original publication, see Jenny and Jossen (1982)
  13. ^ a b Galton and Upchurch (2004); "Systematic and Evolution", page 358.
  14. ^ Galton and Upchurch (2004); "Taphonomy", page 360. For the original publication, see Heinrich (1999).
  15. ^ Chengkai et al. (2007); "Abstract", page 351.
  16. ^ Maidment et al. (2008); "Synopsis", page 367.
  17. ^ Mateus, Maidment and Christiansen (2009); "Abstract", page 1815.
  18. ^ Cameron, Cameron, and Barnett (2015); in passim.
  19. ^ Galton and Carpenter (2016); in passim.
  20. ^ Cameron, Cameron, and Barnett (2016); in passim.
  21. S2CID 91559457
    .
  22. S2CID 89787668
    .
  23. S2CID 91554634
    .
  24. ISSN 1342-937X
    .
  25. S2CID 247267743
    .

References

External links
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