Pteranodon sternbergi
Pteranodon sternbergi | |
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Mounted female and male P. sternbergi skeletons at the Royal Ontario Museum | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Order: | †Pterosauria |
Suborder: | †Pterodactyloidea |
Family: | †Pteranodontidae |
Genus: | †Pteranodon |
Species: | †P. sternbergi
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Binomial name | |
†Pteranodon sternbergi Harksen, 1966
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Synonyms | |
Genus synonymy
Synonyms of G. sternbergi
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Pteranodon sternbergi is an extinct
Discovery and history
The first fossils of Pteranodon sternbergi were collected by American paleontologist
The most complete example of the species, currently in the collections of the University of Alberta Laboratory for Vertebrate Paleontology as specimen number UALVP 24238, is a partially-articulated sub-adult fossil with a wingspan of about 4 meters (13 ft). The skeleton is missing only parts of the skull and the ends of the wings and feet, was discovered in 1974 near
P. sternbergi fossils are known from the Niobrara and Sharon Springs Formations of the central United States. Geosternbergia existed as a group for more than four million years during the late Coniacian – early Campanian stages of the Cretaceous period.[3] The genus is present in the lower the Niobrarra Formation except for the upper two; in 2003, Kenneth Carpenter surveyed the distribution and dating of fossils in this formation, demonstrating that Pteranodon sternbergi existed there from 88 to 85 million years ago, while the species later named G. maiseyi existed between 81.5 and 80.5 million years ago.[6]
Description
Size
Pteranodon sternbergi was among the largest pterosaurs, with the wingspan of most adults ranging between 3 and 6 meters (9.8 and 19.7 ft). No complete skulls of adult males have been found, but a nearly complete lower jaw has been estimated at 1.25 meters (4.1 ft) long.[7] While most specimens are found crushed, enough fossils exist to put together a detailed description of the animal. P. sternbergi differs from its close relative Pteranodon longiceps mainly due to its earlier time period and broader, more upright crest.[5]
Skull and beak
The upright
Unlike the earlier pterosaurs, such as the
Classification
Pteranodon sternbergi is one of the two widely recognized species of Pteranodon. Alexander Kellner has argued that Pteranodon sternbergi should be classified in a separate genus, Geosternbergia,[4] but other pterosaur researchers have regarded this split as unwarranted and continued to classify it as a species of Pteranodon.[5][9] Kellner also classified a specimen previously identified as Pteranodon longiceps as a second species of Geosternbergia, G. maiseyi.[4]
Below is a cladogram showing the phylogenetic placement of this species within Pteranodontia from Andres and Myers (2013).[10]
Pteranodontia |
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Paleobiology
Sexual variation
Adult P. sternbergi specimens may be divided into two distinct size classes, small and large, with the large size class being about one and a half times larger than the small, and the small being twice as common as the large. Both size classes lived alongside each other, and while researchers had previously suggested that they represent different species, Christopher Bennett showed that the differences between them are consistent with the concept that they represent females and males, and that P. sternbergi was sexually dimorphic. Skulls from the larger size class preserve large, upward and backward pointing crests, while the crests of the smaller size class are small and triangular. Some larger skulls also show evidence of a second crest that extended long and low, toward the tip of the beak, which is not seen in smaller specimens.[8]
The gender of the different size classes was determined, not from the skulls, but from the pelvic bones. Contrary to what may be expected, the smaller size class had disproportionately large and wide-set pelvic bones. Bennett interpreted this as indicating a more spacious birth canal, through which eggs would pass. He concluded that the small size class with small, triangular crests represent females, and the larger, large-crested specimens represent males.[8]
Note that the overall size and crest size also corresponds to age. Immature specimens are known from both females and males, and immature males often have small crests similar to adult females. Therefore, it seems that the large crests only developed in males when they reached their large, adult size, making the gender of immature specimens difficult to establish from partial remains.[11]
The fact that females appear to have outnumbered males two to one suggests that, as with modern animals with size-related sexual dimorphism, such as sea lions and other pinnipeds, P. sternbergi might have been polygynous, with a few males competing for association with groups consisting of large numbers of females. Similar to modern pinnipeds, P. sternbergi may have competed to establish territory on rocky, offshore rookeries, with the largest, and largest-crested, males gaining the most territory and having more success mating with females. The crests of male P. sternbergi would not have been used in competition, but rather as "visual dominance-rank symbols", with display rituals taking the place of physical competition with other males. If this hypothesis is correct, it also is likely that male P. sternbergi played little to no part in rearing the young; such a behavior is not found in the males of modern polygynous animals who father many offspring at the same time.[8]
See also
References
- JSTOR 3626742.
- JSTOR 3627664.
- ^ a b c Bennett, S.C. (1994). "Taxonomy and systematics of the Late Cretaceous pterosaur Pteranodon (Pterosauria, Pterodactyloida)". Occasional Papers of the Natural History Museum, University of Kansas. 169: 1–70.
- ^ PMID 21152777.
- ^ doi:10.18435/B5059J.)
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: CS1 maint: multiple names: authors list (link - ISBN 978-1-4020-1443-7.
- ISBN 0-689-84113-2.
- ^ .
- PMID 30581660.
- S2CID 84617119.
- S2CID 90380603.