Aerosteon

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Aerosteon
Temporal range:
Campanian
Aerosteon riocoloradensis.jpg
Skeletal diagram illustrating air-filled bones
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Clade: Megaraptora
Family: Megaraptoridae
Genus: Aerosteon
Sereno et al. 2009
Type species
Aerosteon riocoloradensis
Sereno et al. 2009

Aerosteon is a genus of megaraptoran dinosaur from the Late Cretaceous period of Argentina. Its remains were discovered in 1996 in the Anacleto Formation, which is from the late Campanian. [1] The type and only known species is A. riocoloradensis. Its specific name indicates that its remains were found 1 km (0.6 miles) north of the Río Colorado, in Mendoza Province, Argentina.

Contents

They show evidence of a bird-like respiratory system. [1] Aerosteon's name can be translated as air bone and derives from Greek ἀήρ (aer, "air") and ὀστέον (osteon, "bone").

Discovery

Neck vertebrae Aerosteon cervicals.png
Neck vertebrae

Aerosteon was first discovered in 1996 and was first described by Sereno et al. in a paper which appeared in the online journal PLoS ONE in September 2008. However, at the time, the International Code of Zoological Nomenclature did not recognize online publication of names for new species as valid unless print copies were also produced and distributed to several libraries, and that this action is noted in the paper itself. PLoS ONE initially failed to meet this requirement for Aerosteon. On May 21, 2009, the journal's managing editor coordinated with the ICZN to correct this oversight, publishing a comment to the original paper with an addendum stating that the requirements had been met as of that date. Consequently, though the description appeared in 2008, Aerosteon was not a valid name until 2009. [2]

The holotype specimen, MCNA-PV-3137 consists of some cranial bones, a number of partial or complete vertebrae from the neck, back, and sacrum, several cervical and dorsal ribs, gastralia, furcula (wishbone), left scapulocoracoid, left ilium, and left and right pubes. The incomplete fusion of some of its bones indicate that it was not quite fully mature. No dental material is known for this taxon as the isolated tooth initially referred to the holotype [1] was revealed to belong to an abelisaurid theropod. [3]

Description

Abelisaurid tooth initially referred to the holotype of Aerosteon Tooth of Aerosteon.png
Abelisaurid tooth initially referred to the holotype of Aerosteon
Size of various megaraptorids; Aerosteon in blue Megaraptoridae size chart.png
Size of various megaraptorids; Aerosteon in blue

Initially Aerosteon was estimated at 9 to 10 meters (30 to 33 ft). [1] In 2010, however, Gregory S. Paul, estimated it at 6 meters (20 ft) and 500 kilograms (1,100 lb). [4] Later in 2016, Molina-Pérez and Larramendi gave a length of 7.5 meters (25 ft) and a weight of 1 metric ton (1.1 short tons). [5]

Life restoration Aerosteon BW.jpg
Life restoration

Classification

Aerosteon did not initially appear to belong to any of the three groups of large theropods that were known to have inhabited the southern continents during this time (namely the Abelisauridae, Carcharodontosauridae or Spinosauridae). Sereno suggested that it might be related to the allosauroid radiation of the Jurassic period, and this was supported in subsequent studies that recognized a clade of late-surviving, lightly built, advanced allosauroids with large hand claws similar to the spinosaurs, called the Megaraptora, within the allosaur family Neovenatoridae. [6] A later analysis has placed Megaraptora, including Aerosteon, within the Tyrannosauroidea. [7] Megaraptorans have since been also considered as non-tyrannosauroid basal coelurosaurs in some analyses. [8] [9]

A very close relative of Aerosteon, Murusraptor , was described in 2016 which preserved some bones with a lesser level of pneumaticity. However, the Murusraptor holotype also preserved several teeth which were very dissimilar to the one tooth observed in Aerosteon's holotype. The authors of the description noted that this tooth closely resembled that of abelisaurids and was probably incorrectly referred to Aerosteon. Murusraptor and Aerosteon are practically identical in the structure of their cranial bones and vertebrae, only noticeably differing in the proportions of the ilium, with Aerosteon's ilium being taller than that of Murusraptor. [10]

Pneumatopores on the left ilium of A. riocoloradensis Pneumatopores on the left ilium of the theropod Aerosteon riocoloradensis.jpg
Pneumatopores on the left ilium of A. riocoloradensis

The cladogram below follows the 2010 analysis by Benson, Carrano and Brusatte, which considered megaraptorans as tetanurans. [6]

Neovenatoridae

Neovenator

unnamed

Chilantaisaurus

Megaraptora

Australovenator

Fukuiraptor

? Orkoraptor

Aerosteon

Megaraptor

The cladogram shown below follows an analysis by Porfiri et al., 2014, which recovered megaraptorans as tyrannosauroids. [11]

Megaraptora

Fukuiraptor

Megaraptoridae

Australovenator

Aerosteon

unnamed

Orkoraptor

Eotyrannus

Megaraptor

Paleobiology

Stereo images of the furculae of A. riocoloradensis (A) and the Magpie-goose, Anseranas semipalmata (B). Scale bars are 10 cm in (A) and 2 cm in (B). Furcula of the theropod Aerosteon riocoloradensis and magpie goose Anseranas semiplamata.jpg
Stereo images of the furculae of A. riocoloradensis (A) and the Magpie-goose, Anseranas semipalmata (B). Scale bars are 10 cm in (A) and 2 cm in (B).

Some of Aerosteon's bones show pneumatization (air-filled spaces), including pneumatic hollowing of the furcula and ilium, and pneumatization of several gastralia. The addition of pneumatization throughout the bones of Aerosteon shows the evolutionary progress of the avian air sacs, which first appear as features on the sides of vertebrae, before being incorporated within bones throughout the skeleton. These air sacs would have acted like bellows, moving air into and out of the animal's relatively inflexible lungs, instead of the lungs themselves being expanded and contracted as occurs with mammals. See avian respiratory system for more detailed information on this.

Sereno et al. theorize that this respiratory system may have developed to assist with regulating body temperature and was later co-opted for breathing. [1]

Paleoecology

Aerosteon lived approximately 84 million years ago during the Santonian stage.

Related Research Articles

<i>Fukuiraptor</i> Megaraptoran theropod dinosaur genus from the Early Cretaceous epoch

Fukuiraptor was a medium-sized megaraptoran theropod dinosaur of the Early Cretaceous epoch that lived in what is now Japan. Fukuiraptor is known from the Kitadani Formation and possibly also the Sebayashi Formation.

<i>Eotyrannus</i> Extinct genus of dinosaurs

Eotyrannus is a genus of tyrannosauroid theropod dinosaur hailing from the Early Cretaceous Wessex Formation beds, included in Wealden Group, located in the southwest coast of the Isle of Wight, United Kingdom. The remains (MIWG1997.550), consisting of assorted skull, axial skeleton and appendicular skeleton elements, from a juvenile or subadult, found in a plant debris clay bed, were described by Hutt et al. in early 2001. The etymology of the generic name refers to the animal's classification as an early tyrannosaur or "tyrant lizard", while the specific name honors the discoverer of the fossil.

<i>Deltadromeus</i> Theropod dinosaur genus from mid-Cretaceous Period

Deltadromeus is a genus of theropod dinosaur from Northern Africa. It had long, unusually slender hind limbs for its size, suggesting that it was a swift runner. The skull is not known. One fossil specimen of a single species has been described, found in the Kem Kem Beds, which date to the mid-Cretaceous Period, about 95 million years ago. It may be a junior synonym of the contemporary Bahariasaurus. The classification of Deltadromeus has been in flux since its original description. In 2016, a South American theropod known as Gualicho shinyae was found to possess many similarities with Deltadromeus. Depending on the phylogenetic position of Gualicho, Deltadromeus may have been a neovenatorid carnosaur, a tyrannosauroid, or a basal coelurosaur if its close relation to Gualicho is legitimate. Other studies have considered it a ceratosaurian, more specifically a member of the family Noasauridae.

<i>Megaraptor</i> Extinct genus of dinosaurs

Megaraptor is a genus of large theropod dinosaur that lived in the ages of the Late Cretaceous. Its fossils have been discovered in the Patagonian Portezuelo Formation of Argentina, South America. Initially thought to have been a giant dromaeosaur-like coelurosaur, it was classified as a neovenatorid allosauroid in previous phylogenies, but more recent phylogeny and discoveries of related megaraptoran genera has placed it as either a basal tyrannosauroid or a basal coelurosaur with some studies still considering it a neovenatorid.

<span class="mw-page-title-main">Tyrannosauroidea</span> Extinct superfamily of dinosaurs

Tyrannosauroidea is a superfamily of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent beginning in the Jurassic Period. By the end of the Cretaceous Period, tyrannosauroids were the dominant large predators in the Northern Hemisphere, culminating in the gigantic Tyrannosaurus. Fossils of tyrannosauroids have been recovered on what are now the continents of North America, Europe and Asia, with fragmentary remains possibly attributable to tyrannosaurs also known from South America and Australia.

Unenlagia is a genus of dromaeosaurid theropod dinosaur that lived in South America during the Late Cretaceous period. The genus Unenlagia has been assigned two species: U. comahuensis, the type species described by Novas and Puerta in 1997, and U. paynemili, described by Calvo et al. in 2004.

<span class="mw-page-title-main">Allosauroidea</span> Extinct superfamily of Dinosaurs

Allosauroidea is a superfamily or clade of theropod dinosaurs which contains four families — the Metriacanthosauridae, Allosauridae, Carcharodontosauridae, and Neovenatoridae. Allosauroids, alongside the family Megalosauroidea, were among the apex predators that were active during the Middle Jurassic to Late Cretaceous periods. The most famous and best understood allosauroid is the North American genus Allosaurus.

<i>Orkoraptor</i> Extinct genus of dinosaurs

Orkoraptor is a genus of medium-sized megaraptoran theropod dinosaur from the late Cretaceous Period of Argentina. It is known from incomplete fossil remains including parts of the skull, teeth, tail vertebrae, and a partial tibia. The specialized teeth resemble those of some maniraptoriform theropods, namely the deinonychosaurs and compsognathids. This and other anatomical features led the authors who described it to suggest that it was a maniraptoran coelurosaur. However, subsequent studies found it to be a megaraptoran. Found in the Cerro Fortaleza Formation of Southern Patagonia, it is one of the southernmost carnivorous dinosaurs known from South America.

<span class="mw-page-title-main">Bahariasauridae</span> Probable family of averostran theropods

Bahariasauridae is a potential family of averostran theropods that might include a handful of African and South American genera, such as Aoniraptor, Bahariasaurus, Deltadromeus, and Gualicho. The placement of these theropods is controversial, with some studies placing them as basal ceratosaurs possibly related to Noasauridae, others classifying them as megaraptorans, basal neovenatorids, or basal coelurosaurs. There is also a possibility the group might not be monophyletic, as a monograph on the vertebrate diversity in the Kem Kem Beds published in 2020 found Bahariasaurus to be nomen dubium. In the same paper Deltadromeus is classified as an noasaurid, a result also recovered by some previous studies.

<i>Australovenator</i> Extinct genus of dinosaurs

Australovenator is a genus of megaraptoran theropod dinosaur from Cenomanian -age Winton Formation of Australia. It is known from partial cranial and postcranial remains which were described in 2009 by Scott Hocknull and colleagues, although additional descriptions and analyses continue to be published. It is the most complete predatory dinosaur discovered in Australia. It has been suggested that Australovenator is a sister taxon to Fukuiraptor, although some phylogenetic analyses find it to be a more derived member of the Megaraptora, possibly being part of the main Megaraptoridae family itself.

<span class="mw-page-title-main">Neovenatoridae</span> Extinct family of dinosaurs

Neovenatoridae is a proposed clade of carcharodontosaurian dinosaurs uniting some primitive members of the group such as Neovenator with the Megaraptora, a group of theropods with controversial affinities. Other studies recover megaraptorans as basal coelurosaurs unrelated to carcharodontosaurs. Other theropods with uncertain affinities such as Gualicho, Chilantaisaurus and Deltadromeus are also sometimes included.

<span class="mw-page-title-main">Megaraptora</span> Extinct clade of dinosaurs

Megaraptora is a clade of carnivorous theropod dinosaurs. Its derived members, the Megaraptoridae are noted for their large hand claws and powerfully-built forelimbs, which are usually reduced in size in other large theropods.

<span class="mw-page-title-main">Proceratosauridae</span> Extinct family of dinosaurs

Proceratosauridae is a family or clade of tyrannosauroid theropod dinosaurs from the Middle Jurassic to the Early Cretaceous.

<span class="mw-page-title-main">Skeletal pneumaticity</span> Presence of air spaces within bones

Skeletal pneumaticity is the presence of air spaces within bones. It is generally produced during development by excavation of bone by pneumatic diverticula from an air-filled space, such as the lungs or nasal cavity. Pneumatization is highly variable between individuals, and bones not normally pneumatized can become pneumatized in pathological development.

<i>Pamparaptor</i> Extinct genus of dinosaurs

Pamparaptor is an extinct genus of maniraptoran theropod dinosaur from the Late Cretaceous Portezuelo Formation of the Neuquén province in Argentine Patagonia. Its precise classification is uncertain, but it is definitely a member of Paraves and probably a deinonychosaur. The authors who described it have argued that it is a dromaeosaurid. The genus contains a single species, P. micros, which is known from a single specimen consisting of a mostly complete and fully-articulated left foot, which preserves the iconic dromaeosaur-like “killing claw”.

<i>Siats</i> Extinct genus of theropod dinosaur

Siats (/see-ats/) is an extinct genus of large theropod dinosaur known from the Late Cretaceous Cedar Mountain Formation of Utah, United States. It contains a single species, Siats meekerorum. It was initially classified as a megaraptoran, a clade of large theropods with very controversial relationships. Siats may be a neovenatorid allosauroid, a coelurosaur of uncertain phylogenetic position, or a tyrannosauroid.

<i>Murusraptor</i> Extinct genus of dinosaurs

Murusraptor is a genus of carnivorous megaraptoran theropod dinosaur from the Sierra Barrosa Formation, part of the Neuquén Group of Patagonia, in Argentina, South America. It is known from a single specimen that consists of a partial skull, ribs, partial pelvis, leg and other assorted skeletal elements.

<i>Tratayenia</i> Extinct genus of dinosaurs

Tratayenia is an extinct genus of megaraptoran theropod dinosaurs known from remains found in the Santonian-age Bajo de la Carpa Formation of Argentina. The type and only species, Tratayenia rosalesi, was described in March 2018.

<i>Phuwiangvenator</i> Extinct genus of dinosaurs

Phuwiangvenator is an extinct genus of megaraptoran theropod that lived during the Early Cretaceous period in what is now Thailand. It contains only the type species, P. yaemniyomi. The generic name of Phuwiangvenator comes from the Phu Wiang mountains, where the holotype was discovered, and the Latin word "venator" meaning hunter. The specific name, "yaemniyomi", is in honor of Sudham Yaemniyom, who was a historical paleontologist from Thailand and the first person to discover fossils there.

<i>Maip</i> Genus of megaraptoran dinosaurs

Maip is a genus of large megaraptorid theropod dinosaur from the Late Cretaceous (Maastrichtian) Chorrillo Formation of Santa Cruz, Argentina. The genus contains a single species, M. macrothorax, known from an incomplete, disarticulated skeleton. Maip may represent the largest megaraptorid known from South America, and possibly the world.

References

  1. 1 2 3 4 5 Sereno, P.C.; Martinez, R.N.; Wilson, J.A.; Varricchio, D.J.; Alcober, O.A.; Larsson, H.C.E. (2008). Kemp, Tom (ed.). "Evidence for Avian Intrathoracic Air Sacs in a New Predatory Dinosaur from Argentina". PLOS ONE. 3 (9): e3303. Bibcode:2008PLoSO...3.3303S. doi: 10.1371/journal.pone.0003303 . PMC   2553519 . PMID   18825273.
  2. PLoS ONE Group (2009). "Steps taken to meet the requirements of the ICZN to make new taxonomic names nomenclaturally available. Archived December 5, 2022, at the Wayback Machine " Comment on Original Article: "Evidence for Avian Intrathoracic Air Sacs in a New Predatory Dinosaur from Argentina." PLoS ONE, May 21, 2009.
  3. Hendrickx, Christophe; Tschopp, Emanuel; Ezcurra, Martín D. (April 1, 2020). "Taxonomic identification of isolated theropod teeth: The case of the shed tooth crown associated with Aerosteon (Theropoda: Megaraptora) and the dentition of Abelisauridae". Cretaceous Research. 108: 104312. Bibcode:2020CrRes.10804312H. doi:10.1016/j.cretres.2019.104312. ISSN   0195-6671. S2CID   210268523. Archived from the original on September 16, 2020. Retrieved September 15, 2020.
  4. Paul, Gregory S. (2010). The Princeton Field Guide to Dinosaurs. New Jersey: Princeton University Press. p. 99.
  5. Molina-Pérez & Larramendi (2016). Récords y curiosidades de los dinosaurios Terópodos y otros dinosauromorfos. Spain: Larousse. p. 264.
  6. 1 2 Benson R.B.J.; Carrano M.T.; Brusatte S.L. (2010). "A new clade of archaic large-bodied predatory dinosaurs (Theropoda: Allosauroidea) that survived to the latest Mesozoic". Naturwissenschaften. 97 (1): 71–78. Bibcode:2010NW.....97...71B. doi:10.1007/s00114-009-0614-x. PMID   19826771. S2CID   22646156.
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  8. Apesteguía, S; Smith, N.D.; Valieri, R.J.; Makovicky, P.J. (2016). "An Unusual New Theropod with a Didactyl Manus from the Upper Cretaceous of Patagonia, Argentina". PLOS ONE. 11 (7): e0157793. Bibcode:2016PLoSO..1157793A. doi: 10.1371/journal.pone.0157793 . PMC   4943716 . PMID   27410683.
  9. Novas, F.E.; Aranciaga Rolando, A.M.; Agnolín, F.L. (2016). "Phylogenetic relationships of the Cretaceous Gondwanan theropods Megaraptor and Australovenator: the evidence afforded by their manual anatomy". Memoirs of Museum Victoria. 74: 49–61. doi: 10.24199/j.mmv.2016.74.05 . hdl: 11336/48895 .
  10. Coria, Rodolfo A.; Currie, Philip J. (July 20, 2016). "A New Megaraptoran Dinosaur (Dinosauria, Theropoda, Megaraptoridae) from the Late Cretaceous of Patagonia". PLOS ONE. 11 (7): e0157973. Bibcode:2016PLoSO..1157973C. doi: 10.1371/journal.pone.0157973 . ISSN   1932-6203. PMC   4954680 . PMID   27439002.
  11. Juan D. Porfiri; Fernando E. Novas; Jorge O. Calvo; Federico L. Agnolín; Martín D. Ezcurra; Ignacio A. Cerda (2014). "Juvenile specimen of Megaraptor (Dinosauria, Theropoda) sheds light about tyrannosauroid radiation". Cretaceous Research. 51: 35–55. Bibcode:2014CrRes..51...35P. doi:10.1016/j.cretres.2014.04.007. hdl: 11336/12129 .