Darwinopterus
Darwinopterus | |
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D. modularis fossil | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Order: | †Pterosauria |
Family: | †Wukongopteridae |
Subfamily: | † Wukongopterinae
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Genus: | †Darwinopterus Lü et al., 2010 |
Type species | |
†Darwinopterus modularis Lü et al., 2010
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Other species | |
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Darwinopterus (meaning "Darwin's wing") is a genus of pterosaur, discovered in China and named after biologist Charles Darwin.[1] Between 30 and 40 fossil specimens have been identified,[2] all collected from the Tiaojishan Formation, which dates to the middle Jurassic period, 160.89–160.25 Ma ago.[3][4] The type species, D. modularis, was described in February 2010.[1] D. modularis was the first known pterosaur to display features of both long-tailed (rhamphorhynchoid) and short-tailed (pterodactyloid) pterosaurs, and was described as a transitional fossil between the two groups.[5] Two additional species, D. linglongtaensis and D. robustodens, were described from the same fossil beds in December 2010 and June 2011, respectively.[6][7]
Description
Darwinopterus, like its closest relatives, is characterized by its unique combination of
Darwinopterus is distinguished from its close relatives by the greater relative length of the back portion of the skull compared to its jaws, thin nasal bone, and elongated hip bone (ilium). The teeth in all species were spaced widely with the longest teeth at the jaw tips. The teeth were spike-like in form, and set into tooth sockets with raised margins. The hand bones were relatively short, even shorter than the femur. The tail was long, with over 20 vertebrae, and was partially stiffened by long, thin bony projections.[7] Unlike other wukongopterids, the head crest found in males was supported by a thin bony extension of the skull, with a serrated top edge. The serrations probably helped anchor an even larger keratin extension.[6]
Specimens of Darwinopterus have been divided into three distinct species, based largely on the size and shape of their teeth. The first, D. modularis, was named by Lü Junchang and colleagues in 2010. D. modularis had an especially elongated back end to the skull, and widely spaced, "spike-like" teeth. D. linglongtaensis was named by Wang Xiaolin and colleagues in later in 2010. It was characterized by a shorter and taller skull and shorter, cone-shaped teeth.[6] In 2011, Lü and another team of scientists described and named D. robustodens, for a new specimen with very robust teeth. Lü and colleagues (2011) suggested that these differences in tooth shape may indicate that each Darwinopterus species occupied a different ecological niche, with the teeth of each becoming specialized for different food sources. The robust teeth of D. robustodens, for example, may have been used to feed on hard-shelled beetles.[7]
Biology
Because Darwinopterus is known from numerous well-preserved specimens including an egg, researchers have been able to deduce various aspects of its biology, including growth patterns and life history, reproduction, and possible variation between sexes.
Sexual variation
The large amount of variation among Darwinopterus specimens has been interpreted as sexual dimorphism. The first Darwinopterus specimen in which sex could be confidently identified was specimen ZMNH M8802 in the collections of the Zhejiang Museum of Natural History, nicknamed "Mrs T" (short for "Mrs Pterodactyl"), described by Lü Junchang and colleagues in January 2011. This specimen was preserved with the impression of an egg between its thighs in close association with its pelvis. This specimen had a broad pelvis and lacked any evidence of a crest. The egg was probably expelled from the body during decomposition, and its association with the Darwinopterus individual was used to support the hypothesis of sexual dimorphism.[2]
However, this hypothesis has been criticized. Pterosaur researcher Kevin Padian questioned some of the conclusions drawn by Lü et al., suggesting in a 2011 interview that, in other animals with elaborate display crests (such as ceratopsian dinosaurs), the size and shape of the crests change dramatically with age. He noted that the "Mrs T" specimen may simply have been a sub-adult which had not yet developed a crest (most animals are able to reproduce before they are fully grown).[2] In 2015, Wang e.a. reassigned the "Mrs T" specimen to Kunpengopterus,[8] and in 2021 it was classified as a specimen of the new species Kunpengopterus antipollicatus. Furthermore, a rigorous analysis of wukongopterid variation published in 2017 noted that crests among wukongopterids were subject to a large amount of individual variation, and that there was no consistent dimorphism in the pelvic anatomy of crested and uncrested wukongopterid specimens.[9]
Reproduction
The specimen preserved along with an egg (nicknamed "Mrs T"), described by Lü and colleagues in 2011, offers insight into the reproductive strategies of Darwinopterus and pterosaurs in general.
Diet
Darwinopterus, like most wukongopterids, is a terrestrial pterosaur lacking speciations for piscivory; ergo, it was early on recognised to have been a terrestrial form. Originally, it was described as a raptorial
Classification
Below is a cladogram following Wang et al. (2017) [13]
Monofenestrata |
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Implications
As the name Darwinopterus modularis implies, the researchers who first described this genus saw it as evidence that pterodactyloid pterosaurs evolved from the more primitive 'rhamphorhynchoids' via
See also
References
- ^ PMID 19828548.
- ^ a b c d e f g Hecht, J. (2011). "Did pterosaurs fly out of their eggs?" New Scientist online edition, 20 Jan 2011. Accessed online 21 Jan 2011, https://www.newscientist.com/article/dn20011-did-pterosaurs-fly-out-of-their-eggs.html
- ^ Liu Y.-Q. Kuang H.-W., Jiang X.-J., Peng N., Xu H. & Sun H.-Y. (2012). "Timing of the earliest known feathered dinosaurs and transitional pterosaurs older than the Jehol Biota." Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication).
- .
- ^ Dell'Amore, C. (2009). "Odd New Pterosaur: 'Darwin's Wing' Fills Evolution Gap." National Geographic News, 13 October 2009. Accessed 14 October 2009.
- ^ PMID 21152776.
- ^ S2CID 128545851.
- ^ PMID 26153915.
- PMID 28198921.
- ^ S2CID 206529739.
- S2CID 4416203.
- ^ Witton, Mark P. (2013), Pterosaurs: Natural History, Evolution, Anatomy
- PMID 28202936.