Xiphactinus (from Latin and Greek for "sword-ray") is an extinct genus of large (5.1 metres (16.7 ft)[3]) predatory marine bony fish that lived during the Late Cretaceous (Albian to Maastrichtian).[4] Species in the genus bore a superficial resemblance to a gargantuan, fanged tarpon.
| Xiphactinus | |
|---|---|
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| Mounted skeleton of X. audax at the Tellus Science Museum, Georgia | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | †Ichthyodectiformes |
| Family: | †Ichthyodectidae |
| Subfamily: | †Ichthyodectinae |
| Genus: | †Xiphactinus Leidy, 1870 |
| Type species | |
| †Xiphactinus audax Leidy, 1870
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| Other species | |
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| Synonyms | |
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The species Portheus molossus described by Cope is a junior synonym of X. audax. Skeletal remains of Xiphactinus have come from the Carlile Shale and Greenhorn Limestone of Kansas (where the first Xiphactinus fossil was discovered during the 1850s in the Niobrara Chalk),[5][6] and Cretaceous formations all over the East Coast (most notably Georgia, Alabama, North Carolina, and New Jersey) in the United States,[5][2] as well as Europe, Australia,[7] the Kanguk and Ashville Formations of Canada,[5] La Luna Formation of Venezuela and the Salamanca Formation in Argentina.[5][8][9]
Paleobiology
_(Niobrara_Formation,_Upper_Cretaceous;_Gove_County,_Kansas,_USA)_2_(32938717214).jpg)
Species of Xiphactinus were voracious predatory fish. At least a dozen specimens of X. audax have been collected with the remains of large, undigested or partially digested prey in their stomachs. In particular, one 4.2 metres (14 ft) fossil "Fish-Within-A-Fish" specimen was collected by George F. Sternberg with another, nearly perfectly preserved 1.9 metres (6.2 ft) long ichthyodectid Gillicus arcuatus inside of it. The larger fish apparently died soon after eating its prey, most likely owing to the smaller prey's struggling and rupturing an organ as it was being swallowed. This fossil is on display at the Sternberg Museum of Natural History in Hays, Kansas.[10]
Like many other species in the Late Cretaceous oceans, a dead or injured individual was likely to be scavenged by sharks (Cretoxyrhina and Squalicorax). The remains of a Xiphactinus were found within a large specimen of Cretoxyrhina collected by Charles H. Sternberg. The specimen is on display at the University of Kansas Museum of Natural History.
Virtually nothing is known about the larval or juvenile stages. The smallest fossil specimen of X. audax consists of a tooth-bearing premaxilla and lower jaws of an individual estimated to be about 12 inches (30 cm) long.[11][self-published source?][better source needed]
The species and all other ichthyodectids became extinct near the end of the Late Cretaceous – see Cretaceous–Paleogene extinction event.
An incomplete skull of what may be a new species of Xiphactinus was found in 2002 in the Czech Republic, in a small town called Šachov next to Borohrádek city, by then 16-year-old student Michal Matějka.[12]
In July 2010 the bones of a Xiphactinus were discovered near Morden, Manitoba, Canada. The specimen was about 18–20 feet (5.5–6.1 m) long and was found with the flipper of a mosasaur between its jaws.[13]
"Unicerosaurus"
In 1982, a former Baptist minister, Carl Baugh, began excavations on the limestone beds of the Paluxy River, near Glen Rose, Texas, famous for its dinosaur tracks. Some of the tracks resembled human footprints and had been proclaimed since 1900 as evidence that dinosaurs and modern humans had once lived alongside one another. Scientists' investigations found the supposed human footprints to be "forms of elongate dinosaur tracks, while others were selectively highlighted erosional markings, and still others (on loose blocks) probable carvings." While excavating, he found a solitary "Y-shaped" fossil that he informally called "Unicerosaurus". In a 1987 popular article, John Armstrong described the fossil as a "Y-shaped petrified bone that appears to be the neural spine from a huge fish like the Portheus of Niobrara Chalk" that Baugh's museum "declared to be the forehead horn of a newly discovered dinosaur genus".[14] The museum's exhibit told visitors that the "horn" belonged to "the unicorn of Job 38, one of three dinosaurs mentioned in Scripture; the others being behemoth and leviathan of Job 40 and 41", and that the horn was able to fold back like the blade of a jack knife. Although some Young Earth Creationists shared Baugh's interpretations of the biblical Behemoth and Leviathan, Baugh's claims were not taken seriously either by Christian organizations or the scientific community.[citation needed]
In popular culture
In October 2010, Kansas House Rep. Tom Sloan (R-Lawrence) announced that he would introduce legislation to make Xiphactinus audax, a.k.a. the "X-fish", the state fossil of Kansas.[15]
Notes
References
- ^ Bardack, D. (1965). "Anatomy and evolution of chirocentrid fishes". The University of Kansas Paleontological Contributions. 10: 1–88. hdl:1808/3814.
- ^ a b Schwimmer, David R.; Stewart, J. D.; Williams, G. Dent (1997). "Xiphactinus vetus and the Distribution of Xiphactinus Species in the Eastern United States". Journal of Vertebrate Paleontology. 17 (3): 610–15. doi:10.1080/02724634.1997.10011007. JSTOR 4523841.
- ^ Shimada, Kenshu, and Michael J. Everhart. "Shark-bitten Xiphactinus audax (Teleostei: Ichthyodectiformes) from the Niobrara Chalk (Upper Cretaceous) of Kansas." The Mosasaur 7 (2004): 35-39.
- ^ Sepkoski, Jack (2002). "A compendium of fossil marine animal genera". Bulletins of American Paleontology. 364: 560. Archived from the original on July 23, 2011. Retrieved 2009-02-27.
- ^ a b c d Xiphactinus at Fossilworks.org
- ^ Haines, Tim; Chambers, Paul (2005). The complete guide to prehistoric life (First ed.). Buffalo, N.Y.: Firefly Books. p. 134. ISBN 978-1-55407-181-4.
The first Xiphactinus fossil was found during the 1850s in Kansas.
- ^ Vavrek, Matthew J.; Murray, Alison M.; Bell, Phil R. (2016-02-04). "Xiphactinus audax Leidy 1870 from the Puskwaskau Formation (Santonian to Campanian) of northwestern Alberta, Canada and the distribution of Xiphactinus in North America". Vertebrate Anatomy Morphology Palaeontology. 1: 89. doi:10.18435/B5H596.
- ^ De Pasqua, Julieta J.; Agnolin, Federico L.; Bogan, Sergio (2020). "First record of the ichthyodectiform fish Xiphactinus (Teleostei) from Patagonia, Argentina". Alcheringa: An Australasian Journal of Palaeontology. 44 (2): 327–331. doi:10.1080/03115518.2019.1702221. S2CID 216170146.
- ^ Carrillo-Briceño, J., Alvarado-Ortega, J. & Torres, C. (2012). Primer registro de Xiphactinus Leidy, 1870, (Teleostei: Ichthyodectiformes) en el Cretácico Superior de América del Sur (Formación La Luna, Venezuela). Revista Brasileira de Paleontologia 15(3):327-335
- ^ Konishi, T., Newbrey, M. G., & Caldwell, M. W. (2014). A small, exquisitely preserved specimen of Mosasaurus missouriensis (Squamata, Mosasauridae) from the upper Campanian of the Bearpaw Formation, western Canada, and the first stomach contents for the genus. Journal of Vertebrate Paleontology, 34(4), 802–819. https://doi.org/10.1080/02724634.2014.838573
- ^ "Xiphactinus Audax" (JPG). oceansofkansas.com.
- ^ http://www.mestoborohradek.cz/file.php?nid=428&oid=5254456 [bare URL PDF]
- ^ "Major Fossil Discovery Underway in Morden" (PDF). Canadian Fossil Discovery Centre. July 16, 2010. Press release.
- ^ Armstrong, John R. (1987). Creation/Evolution Newsletter 7 5:21; Geolog. 16, Part 4.
- ^ "Kansas Rep. Tom Sloan agrees to back X-fish as state's official fossil / LJWorld.com". .ljworld.com. Associated Press. 2010-10-26. Retrieved 2011-10-12.
External links
