Kronosaurus

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Kronosaurus
Temporal range: Aptian-Late Albian
~120–100 Ma
Kronosaurus boyacensis fossil.jpg
K. boyacensis in Villa de Leyva, Boyaca, Colombia
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Superorder: Sauropterygia
Order: Plesiosauria
Family: Pliosauridae
Subfamily: Brachaucheninae
Genus: Kronosaurus
Longman, 1924[1]
Type species
Kronosaurus queenslandicus
Species
  • K. queenslandicus Longman, 1924 (type)[1]
  • K. boyacensis Hampe 1992[2]

Kronosaurus (/ˌkrɒnˈsɔːrəs/ KRON-o-SAWR-əs; meaning "lizard of Kronos") is an extinct genus of short-necked pliosaur. With an estimated length of 9 to 10.5 metres (30 to 34 ft), it was among the largest pliosaurs, and is named after the leader of the Greek Titans, Cronus. It lived in the Early Cretaceous period (Aptian to Late Albian).[2][3] Fossil material has been recovered from the Toolebuc Formation (middle to late Albian) and Wallumbilla Formations (Aptian) of Queensland and New South Wales in Australia, and from the upper Paja Formation (late Aptian) in Boyacá, Colombia, and assigned to two species.

Description[edit]

Restoration of K. queenslandicus

Like other pliosaurs, Kronosaurus was a marine reptile. It had an elongated head, a short neck, a stiff body propelled by four flippers, and a relatively short tail. The posterior flippers were larger than the anterior. Kronosaurus was carnivorous, and had many long, sharp, conical teeth. A feature of the genus Kronosaurus is that the first three maxillary teeth are enlarged to fangs.[4] Current estimates put Kronosaurus at around 9 to 10.5 metres (30 to 34 ft) in length.[3][4] In 2009, K. queenslandicus was estimated to weigh up to 11,000 kilograms (11 t).[4]

All Sauropterygians had a modified pectoral girdle that supported a powerful swimming stroke.[5] Kronosaurus and other plesiosaurs/pliosaurs had a similarly adapted pelvic girdle,[6] allowing them to push hard against the water with all four flippers. Between its two limb girdles was a massive mesh of gastralia (belly ribs) that provided additional strength and support.[6] The strength of the limb girdles, combined with evidence of large, powerful swimming muscles, indicates that Kronosaurus was likely a fast, active swimmer.[6]

Kronosaurus queenslandicus has four pairs of premaxillary teeth. The first three pairs of its maxillary teeth are large caniniform teeth, and in its lower jaw there are also three pairs of large caniniform teeth which are located immediately in front of the three maxillary caniniforms when the mouth is closed. Two pairs of the lower jaw caniniforms occlude between the last pair of premaxillary teeth and first pair of maxillary teeth in a diastema (gap in the tooth row). The enlargement of these two pairs of lower jaw teeth in K. queenslandicus may be related to the absence of a fifth pair of premaxillary teeth, which are present in a number of other pliosaurs.[4]

Oliver Hampe described Kronosaurus boyacensis as having five pairs of premaxillary teeth. Colin Richard McHenry has said that the premaxillary tooth count of K. boyacensis requires confirmation and that if its premaxillary tooth count is confirmed to be five, it may be appropriate to place K. boyacensis into a different genus to K. queenslandicus. In addition to apparently having a different premaxillary tooth count, K. boyacensis differs from K. queenslandicus in postcranial features and possibly tooth ornamentation.[4]

Teeth[edit]

Kronosaurus teeth exceed 7 centimetres (2.8 in) in length (the largest up to 30 centimetres (12 in) long with 12 centimetres (4.7 in) crowns). However, they lack carinae (cutting edges) and the distinct trihedral (three facets) of Pliosaurus and Liopleurodon teeth. The combination of large size, conical shape and lack of cutting edges allows for easy identification of Kronosaurus teeth in Cretaceous formations from Australia.[3][7]

Discovery and species[edit]

In 1899, Andrew Crombie of Hughenden discovered a "scrap of bone" containing six conical teeth, and gave this fragmentary fossil to the Queensland Museum. Twenty-five years later, then-director Heber Longman formally described the specimen as the holotype of a new species: Kronosaurus queenslandicus.[1][8] More Kronosaurus material, including a partial skull, was discovered in 1929, in the same location as Crombie's original find.[8]

In 1977, a Colombian peasant farmer from Moniquirá turned up an enormous stone while tilling his field, which he later recognized as a possible fossil. Excavation revealed a nearly complete Kronosaurus skeleton, one of the best preserved fossils to come from Colombia.[9] Oliver Hampe formally described the specimen in 1992, assigning it to a second species, K. boyacensis.[2]

The people of Villa de Leyva built a museum, El Fósil, around the spot where the skeleton was excavated, and the K. boyacensis skeleton is on display there.[9]

Harvard's completed skeleton[edit]

K. queenslandicus at Harvard University which may have been reconstructed with too many vertebrae
K. queenslandicus scale diagram, showing the size of the restored Harvard skeleton along with a more accurate estimate

In 1931 the Harvard Museum of Comparative Zoology (MCZ) sent an expedition to Australia for the dual purpose of procuring specimens - the museum being "weak in Australian animals and...desires[ing] to complete its series" - and to engage in "the study of the animals of the region when alive."[10] The Harvard Australian Expedition (1931–1932), as it became known, was a six-man venture led by Harvard Professor William Morton Wheeler, with the others being Dr. P. Jackson Darlington, Jr. (a renowned coleopterist)[11][12], Dr. Glover Morrill Allen and his student Ralph Nicholson Ellis[13], medical officer Dr. Ira M. Dixon, and William E. Schevill (a graduate-student in his twenties and Associate Curator of Invertebrate Palaeontology).[14][15][16] MCZ director Thomas Barbour said at the time "We shall hope for specimens' of the kangaroo, the wombat, the Tasmanian devil and Tasmanian wolf," and the mission was a success with over 300 mammal and thousands of insect specimens returning to the United States.[17][18] Yet Mr. Schevill, the team's fossil enthusiast, remained in Australia after the others had departed and, in the winter of 1932, was told by the rancher R.W.H. Thomas of rocks with something "odd" poking out of them on his property near Hughenden.[8][19][20][21] The rocks were limestone nodules containing the most complete skeleton of Kronosaurus ever discovered.[8][22][23] After dynamiting the nodules out of the ground (and into smaller pieces weighing approximately four tons[24][25]) with the aid of a British migrant trained in the use of explosives[26], William Schevill had the fossils shipped back to Harvard for examination and preparation. The skull—which matched the holotype jaw fragment of K. queenslandicus—was prepared right away, but time and budget constraints put off restoration of the nearly complete skeleton - most of the bones of which remained unexcavated within the limestone blocks - for 20 years.[22]

This interim ended when they came to the attention of Godfrey Lowell Cabot - Boston industrialist, philanthropist, and founder of the Cabot Corporation - "who was then in his nineties had been interested in sea serpents since childhood."[27] Having formerly question MCZ director Alfred Romer about the existence and reports of sea serpents and it thus occurred to Dr. Romer to tell Mr. Cabot about the skeleton in the museum closet. Godfrey Cabot thus asked asked how much a restoration would cost and "Romer, pulling a figure out of the musty air, replied, 'Oh, about $10,000.'" Romer may not have been serious but the philanthropist clearly was because the check for said sum came shortly thereafter.[28][29] Two years - and more than $10,000 - later, following the careful labor of the museum preparators, the restored and mounted skeleton was displayed at Harvard in 1959.[8][22] However, Dr. Romer and MCZ preparator Arnold Lewis confirmed that same year in the institution’s journal Breviora that "erosion had destroyed a fair fraction of this once complete and articulated skeleton...so that approximately a third of the specimen as exhibited is plaster restoration."[30] Furthermore, the original (real) bones are also layered in plaster; a fact that, while keeping the fossils safe, makes it difficult for paleontologists to study it - an issue which factors into the controversial question of the true size of the Kronosaurus queenslandicus.[31]

Size issues[edit]

Body-length estimates, largely based on the 1959 Harvard reconstruction, had previously put the total length of Kronosaurus at 12.8 metres (42 ft).[32] However, more recent studies, comparing fossil specimens of Kronosaurus to other pliosaurs suggests that the Harvard reconstruction may have included too many vertebrae, exaggerating the previous estimate, with the true length probably only 9 to 10.5 metres (30 to 34 ft).[3][4]

Classification[edit]

Reconstructed skull of the Harvard specimen
Restoration of K. boyacensis by Dmitry Bogdanov, 2008.

The cladogram below follows a 2011 analysis by paleontologists Hilary F. Ketchum and Roger B. J. Benson, and reduced to genera only.[33]

Pliosauroidea
Rhomaleosauridae

Anningasaura

"Plesiosaurus" macrocephalus

Archaeonectrus

Macroplata

Atychodracon

Eurycleidus

Rhomaleosaurus

Meyerasaurus

Maresaurus

Pliosauridae

Thalassiodracon

Hauffiosaurus

Attenborosaurus

BMNH R2439

Marmornectes

"Pliosaurus" andrewsi

OUMNH J.02247

Peloneustes

Simolestes

Liopleurodon

Pliosaurus

Megacephalosaurus[34]

Brachauchenius

Kronosaurus

Paleobiology[edit]

Life restoration of K. queenslandicus preying on Woolungasaurus by Dmitry Bogdanov, 2008.

Fossil stomach contents from Northern Queensland show that Kronosaurus preyed on turtles and plesiosaurs. Fossil remains of giant squid have been found in the same area as Kronosaurus; it may have fed on them, but no direct evidence for this exists.[35]

Large, round bite-marks have been found on the skull of an Albian-age Australian elasmosaurid (Eromangasaurus) that could be from a Kronosaurus attack.[36][37]

Palaeoecology[edit]

Kronosaurus is known from Australia and Colombia. Both areas were covered by shallow inland seas when Kronosaurus inhabited them.[9][35]

See also[edit]

References[edit]

  1. ^ a b c Longman HA. 1924. A new gigantic marine reptile from the Queensland Cretaceous, Kronosaurus queenslandicus new genus and species. Memoirs of the Queensland Museum 8: 26–28.
  2. ^ a b c Hampe O. 1992. Ein großwüchsiger Pliosauride (Reptilia: Plesiosauria) aus der Unterkreide (oberes Aptium) von Kolumbien. Courier Forschungsinstitut Senckenberg 145: 1-32.
  3. ^ a b c d Kear BP. 2003. Cretaceous marine reptiles of Australia: a review of taxonomy and distribution. Cretaceous Research 24: 277–303.
  4. ^ a b c d e f McHenry, Colin R. "Devourer of Gods: The Palaeoecology of the Cretaceous Pliosaur Kronosaurus Queenslandicus." The University of Newcastle Australia, Apr. 2009. Web.
  5. ^ Palaios - Sauropterygia
  6. ^ a b c Palaios - Plesiosauria
  7. ^ Massare JA. 1997. Introduction - faunas, behaviour and evolution. In: Callaway JM, Nicholls EL. (Eds.), Ancient Marine Reptiles. Academic Press, San Diego, pp. 401-421.
  8. ^ a b c d e Mather, Patricia, with Agnew, N.H. et al. The History of the Queensland Museum, 1862-1986 Retrieved from archive.org
  9. ^ a b c Museo El Fósil
  10. ^ Nature International Journal of Science No. 3228, VOL. 128 - https://www.nature.com/articles/128457c0.pdf
  11. ^ Capinera, John L. (2008). "Darlington, Jr., Philip J". Encyclopedia of Entomologists. pp. 1153–1154. 
  12. ^ A Guide to Stag Beetles of Australia By George Hangay, Roger de Keyzer (p. 139) - https://books.google.com/books?id=CqxWDgAAQBAJ&pg=PA139&lpg=PA139&dq=Harvard+expedition+to+Australia+in+1931&source=bl&ots=z7sMfkRcr3&sig=F82aRX9ZWuNqujfCXBHj90YFs5A&hl=en&sa=X&ved=0ahUKEwjt3Kq1_K3bAhWB7lMKHW0uAJ8Q6AEIWTAF#v=onepage&q=Harvard%20expedition%20to%20Australia%20in%201931&f=false
  13. ^ Ralph Ellis archives, 1898-1972 - http://etext.ku.edu/view?docId=ksrlead/ksrl.sc.ellisralpharchives.xml
  14. ^ About the Exhibits by Elizabeth Hall and Max Hall (Museum of Comparative Zoology "Agazziz Museum" Havard University. Third Edition, Copywrite 1964, 1975, 1985, by the President and Fellows of Harvard College
  15. ^ Nature International Journal of Science No. 3228, VOL. 128 - https://www.nature.com/articles/128457c0.pdf
  16. ^ Annual report of the director of the Museum of Comparative Zoology at Harvard College, to the president of Harvard College for 1932-1933. Cambridge, U.S.A.: Printed for the Museum p.54-58 [BHL - https://www.biodiversitylibrary.org/page/41109461#page/58/mode/1up]
  17. ^ Capinera, John L. (2008). "Darlington, Jr., Philip J". Encyclopedia of Entomologists. pp. 1153–1154. 
  18. ^ About the Exhibits by Elizabeth Hall and Max Hall (Museum of Comparative Zoology "Agazziz Museum" Havard University. Third Edition, Copywrite 1964, 1975, 1985, by the President and Fellows of Harvard College
  19. ^ News-Press from Fort Myers, Florida on January 26, 1989 · Page 9 - https://www.newspapers.com/newspage/215995144/
  20. ^ About the Exhibits by Elizabeth Hall and Max Hall (Museum of Comparative Zoology "Agazziz Museum" Havard University. Third Edition, Copywrite 1964, 1975, 1985, by the President and Fellows of Harvard College
  21. ^ Bailey, Joyce R. W. H. Thomas : a man of distinction. Joyce Bailey, [Kangaloon, N.S.W, 2005. - https://trove.nla.gov.au/work/19722517?q&versionId=23188287+220283007
  22. ^ a b c Meyers, Troy. Kronosaurus Chronicles. Australian Age of Dinosaurs, Issue 3, 2005. Retrieved from australianageofdinosaurs.com[permanent dead link]
  23. ^ Zoology Museum to Exhibit Largest Sea-Reptile Fossil - https://www.thecrimson.com/article/1956/4/25/zoology-museum-to-exhibit-largest-sea-reptile/
  24. ^ Rolfe, WD Ian. "William Edward Schevill: palaeontologist, librarian, cetacean biologist." Archives of natural history 39.1 (2012): 162-164. - https://www.euppublishing.com/doi/pdfplus/10.3366/anh.2012.0069
  25. ^ 1930s: The One That Got Away - https://australianmuseum.net.au/blogpost/museullaneous/1930s-the-one-that-got-away
  26. ^ The Rarest of the Rare: Stories Behind the Treasures at the Harvard Museum of Natural History (Hardcover) – October 26, 2004
  27. ^ About the Exhibits by Elizabeth Hall and Max Hall (Museum of Comparative Zoology "Agazziz Museum" Havard University. Third Edition, Copywrite 1964, 1975, 1985, by the President and Fellows of Harvard College
  28. ^ About the Exhibits by Elizabeth Hall and Max Hall (Museum of Comparative Zoology "Agazziz Museum" Havard University. Third Edition, Copywrite 1964, 1975, 1985, by the President and Fellows of Harvard College
  29. ^ The Rarest of the Rare: Stories Behind the Treasures at the Harvard Museum of Natural History (Hardcover) – October 26, 2004
  30. ^ Romer, A. S. and A. D. Lewis. 1959. A mounted skeleton of the giant plesiosaur Kronosaurus. Breviora 112:1-15.
  31. ^ The Rarest of the Rare: Stories Behind the Treasures at the Harvard Museum of Natural History (Hardcover) – October 26, 2004
  32. ^ Romer AS, Lewis AD. 1959. A mounted skeleton of the giant plesiosaur Kronosaurus. Breviora 112: 1-15.
  33. ^ Hilary F. Ketchum and Roger B. J. Benson (2011). "A new pliosaurid (Sauropterygia, Plesiosauria) from the Oxford Clay Formation (Middle Jurassic, Callovian) of England: evidence for a gracile, longirostrine grade of Early-Middle Jurassic pliosaurids". Special Papers in Palaeontology. 86: 109–129. doi:10.1111/j.1475-4983.2011.01083.x. 
  34. ^ Schumacher, B. A.; Carpenter, K.; Everhart, M. J. (2013). "A new Cretaceous Pliosaurid (Reptilia, Plesiosauria) from the Carlile Shale (middle Turonian) of Russell County, Kansas". Journal of Vertebrate Paleontology. 33 (3): 613. doi:10.1080/02724634.2013.722576. 
  35. ^ a b Queensland Museum - Kronosaurus
  36. ^ Sachs S. 2005. Tuarangisaurus australis sp. nov. (Plesiosauria: Elasmosauridae) from the Lower Cretaceous of northeastern Queensland, with additional notes on the phylogeny of the Elasmosauridae. Memoirs of the Queensland Museum. 50 (2): 425-440.
  37. ^ Kear, B. P. 2007. Taxonomic Clarification of the Australian Elasmosaurid Genus Eromangasaurus, with Reference to Other Austral Elasmosaur Taxa. Memoirs of the Queensland Museum. 27 (1): 241-246.

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