Allkaruen

Allkaruen (meaning "ancient brain") is a genus of rhamphorhynchoid pterosaur from the Early-to-Middle Jurassic Cañadon Asfalto Formation in Argentina.[1] It contains a single species, A. koi.

Allkaruen
Temporal range: Early-Mid Jurassic
~178–168 Ma
Allkaruen
Skeletal elements
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Order: Pterosauria
Genus: Allkaruen
Codorniú et al. 2016[1]
Species:
A. koi
Binomial name
Allkaruen koi
Codorniú et al. 2016[1]

Description

Allkaruen endocast
Endocast of the brain

As demonstrated by a CT scan, the braincase of Allkaruen exhibits a unique set of traits that are intermediate between more basal pterosaurs such as Rhamphorhynchus and more derived pterodactyloid pterosaurs such as Anhanguera. These traits are the position of the anterior semicircular canal of the inner ear,[2] the relative orientations of the occiput and occipital condyle, the relative positions of the lateral margins of the flocculus and cerebral hemispheres, and the ratio between the length of the brain and the height of the hindbrain.[1] In addition, the relative orientations of the frontal bone and lateral semicircular canal are more similar to Rhamphorhynchus than Anhanguera, while the optic lobes are positioned lower than the forebrain as in pterodactyloids.[1][2] This unique combination of characters indicates that the anatomy of the braincase in pterodactyloids evolved through mosaic evolution.

The parietals of Allkaruen were long, being 60% of the length of the frontals; the frontals themselves were broad, flat, and extensively pneumatized. The lower jaw was about 3.5 times the length of the section of the skull that is preserved, and it is curved upwards at its tip. The dentary bore four or five tooth sockets in its front half, and in the latter half they were replaced by a groove; this combination is unique among pterosaurs.[1]

Allkaruen was a small pterosaur. The holotype specimen would have been an adult, since its skull was entirely fused.[1]

Discovery and naming

The holotype of Allkauren consists of a braincase (MPEF-PV 3613), a mandible (MPEF-PV 3609), and a cervical vertebra (MPEF-PV 3615); a similar cervical vertebra (MPEF-PV 3616) was also referred to the genus.[1] These elements were in 2000 discovered in the Cañadón Asfalto Formation, Cerro Cóndor, Chubut, Argentina, for which dates ranging from the Toarcian to earliest Bathonian have been proposed.[3] Other elements, mostly disarticulated and consisting of a number of limb bones as well as another mandible, were also discovered at the site.[1][4]

The name Allkaruen is Tehuelche in origin, being derived from all ("brain") and karuen ("ancient"). The specific name, koi, originates from the Tehuelche word for "lake", in reference to the fact that the type locality would have been a saline lake.[1][5]

Classification

In 2016, two phylogenetic analyses were conducted based on the dataset from the description of Darwinopterus in order to determine the phylogenetic position of Allkaruen.[6] One analysis was restricted to the holotype braincase, while the other included the holotype mandible and cervical vertebrae as well. Allkaruen was consistently recovered as the sister taxon of the Monofenestrata; the consensus of the 360 most parsimonious trees is shown below.[1]

 Breviquartossa 

Dorygnathus

Nesodactylus

Rhamphorhynchus

Cacibupteryx

Pterorhynchus

Sordes

Scaphognathus

Allkaruen

 Monofenestrata 

Darwinopterus

Wukongopterus

Pterodactyloidea

References

  1. ^ a b c d e f g h i j k Codorniú, L.; Carabajal, A.P.; Pol, D.; Unwin, D.; Rauhut, O.W.M (2016). "A Jurassic pterosaur from Patagonia and the origin of the pterodactyloid neurocranium". PeerJ. 4: e2311. doi:10.7717/peerj.2311. PMC 5012331. PMID 27635315.
  2. ^ a b Witmer, L.M.; Chatterjee, S.; Franzosa, J.; Rowe, T. (2003). "Neuroanatomy of flying reptiles and implications for flight, posture and behaviour". Nature. 425 (6961): 950–953. Bibcode:2003Natur.425..950W. doi:10.1038/nature02048. PMID 14586467.
  3. ^ Cúneoa, R.; Ramezani, J.; Scasso, R.; Pol, D.; Escapa, I.; Zavattieri, A.M.; Bowring, S.A. (2013). "High-precision U–Pb geochronology and a new chronostratigraphy for the Cañadón Asfalto Basin, Chubut, central Patagonia: Implications for terrestrial faunal and floral evolution in Jurassic". Gondwana Research. 24 (3–4): 1267–1275. Bibcode:2013GondR..24.1267C. doi:10.1016/j.gr.2013.01.010.
  4. ^ Codorniú, L.; Rauhut, O.W.M.; Pol, D. (2010). "Osteological features of Middle Jurassic pterosaurs from Patagonia (Argentina)". Acta Geoscientica Sinica. 31 (suppl. 1): 12–13.
  5. ^ Cabaleri, N.G.; Armella, C.; Silva Nieto, D.G. (2005). "Saline paleolake of the Cañadón Asfalto Formation (Middle-Upper Jurassic), Cerro Cóndor, Chubut province (Patagonia), Argentina". Facies. 51 (1): 350–364. doi:10.1007/s10347-004-0042-5.
  6. ^ Lu, J.; Unwin, D.M.; Jin, X.; Liu, Y.; Ji, Q. (2010) [2009]. "Evidence for modular evolution in a long-tailed pterosaur with a pterodactyloid skull". Proceedings of the Royal Society B: Biological Sciences. 277 (1680): 383–389. doi:10.1098/rspb.2009.1603. PMC 2842655. PMID 19828548.
Anchisauria

The Anchisauria were a clade of sauropodomorph dinosaurs that lived during the Late Triassic and Early Jurassic. The name Anchisauria was first used by Galton and Upchurch in the second edition of The Dinosauria. Galton and Upchurch assigned two families of dinosaurs to the Anchisauria: the Anchisauridae and the Melanorosauridae. The more common prosauropods Plateosaurus and Massospondylus were placed in the sister clade Plateosauria.

However, recent research indicates that Anchisaurus is closer to sauropods than traditional prosauropods; thus, Anchisauria would also include Sauropoda.The following cladogram simplified after an analysis presented by Blair McPhee and colleagues in 2014.

Averostra

Averostra, or "bird snouts", is a clade that includes most theropod dinosaurs that have a promaxillary fenestra (fenestra promaxillaris), an extra opening in the front outer side of the maxilla, the bone that makes up the upper jaw. Two groups of averostrans, the Ceratosauria and the Orionides, survived into the Cretaceous period. When the Cretaceous–Paleogene extinction event occurred, ceratosaurians and two groups of orionideans within the clade Coelurosauria, the Tyrannosauroidea and Maniraptoriformes, were still extant. Only one subgroup of maniraptoriformes, Aves, survived the extinction event and persisted to the present day.

Avetheropoda

Avetheropoda, or "bird theropods", is a clade that includes carnosaurians and coelurosaurs to the exclusion of other dinosaurs.

Cerapoda

Cerapoda ("ceratopsians and ornithopods") is a clade of the dinosaur order Ornithischia.

Dinosauriformes

Dinosauriformes is a clade of archosaurian reptiles that include the dinosaurs and their most immediate relatives. All dinosauriformes are distinguished by several features, such as shortened forelimbs and a partially to fully perforated acetabulum, the hole in the hip socket traditionally used to define dinosaurs. The oldest known member is Asilisaurus, dating to about 245 million years ago in the Anisian age of the middle Triassic period.

Haya griva

Haya is an extinct genus of basal neornithischian dinosaur known from Mongolia.

Jeholosauridae

Jeholosaurids were herbivorous neornithischian dinosaurs from the Cretaceous Period (Aptian - Santonian, with a possible Campanian record) of Asia. The family was first proposed by Han et al. in 2012. The jeholosaurids were defined as those ornithischians more closely related to Jeholosaurus shangyuanensis than to Hypsilophodon foxii, Iguanodon bernissartensis, Protoceratops andrewsi, Pachycephalosaurus wyomingensis, or Thescelosaurus neglectus. The Jeholosauridae includes the type genus Jeholosaurus and Yueosaurus.

Jingshanosaurus

Jingshanosaurus (meaning "Jingshan lizard") is a genus of sauropodomorph dinosaurs from the early Jurassic period.

Melanorosauridae

The Melanorosauridae were a family of sauropodomorph dinosaurs which lived during the Late Triassic and Early Jurassic. The name Melanorosauridae was first coined by Friedrich von Huene in 1929. Huene assigned several families of dinosaurs to the infraorder "Prosauropoda": the Anchisauridae, the Plateosauridae, the Thecodontosauridae, and the Melanorosauridae. Since then, these families have undergone numerous revisions. Galton and Upchurch (2004) considered Camelotia, Lessemsaurus, and Melanorosaurus members of the family Melanorosauridae. A more recent study by Yates (2007) indicates that the melanorosaurids were instead early sauropods.

Neotheropoda

Neotheropoda (meaning "new theropods") is a clade that includes coelophysoids and more advanced theropod dinosaurs, and the only group of theropods who survived the Triassic–Jurassic extinction event. Yet all of the neotheropods became extinct during the early Jurassic period except for Averostra.

Novialoidea

Novialoidea (meaning "new wings") is an extinct clade of macronychopteran pterosaurs that lived from the latest Early Jurassic to the latest Late Cretaceous (early Toarcian to late Maastrichtian age), their fossils having been found on all continents except Antarctica. It was named by Alexander Wilhelm Armin Kellner in 2003 as a node-based taxon consisting of the last common ancestor of Campylognathoides, Quetzalcoatlus and all its descendants. This name was derived from Latin novus "new", and ala, "wing", in reference to the wing synapomorphies that the members of the clade possess. Unwin (2003) named Lonchognatha in the same issue of the journal that published Novialoidea (Geological Society of London, Special Publications 217) and defined it as Eudimorphodon ranzii, Rhamphorhynchus muensteri, their most recent common ancestor and all its descendants (as a node-based taxon). Under Unwin's and Kellner's phylogenetic analyses (where Eudimorphodon and Campylognathoides form a family that basal to both Rhamphorhynchus and Quetzalcoatlus), and because Novialoidea was named first (in pages 105-137, while Lonchognatha was named in pages 139-190), Lonchognatha is an objective junior synonym of the former. However, other analyses find Lonchognatha to be valid (Andres et al., 2010) or synonymous with the Pterosauria (Andres, 2010 and Andres, in press).

Orionides

Orionides is a clade of tetanuran theropod dinosaurs from the Middle Jurassic to the Present. The clade includes most theropod dinosaurs, including birds.

Orodrominae

Orodrominae is a subfamily of parksosaurid dinosaurs from the Cretaceous of North America and Asia.

Plateosauridae

Plateosauridae is a family of plateosaurian sauropodomorphs from the Late Triassic of Europe. Although several dinosaurs have been classified as plateosaurids over the years, the family Plateosauridae is now restricted to Plateosaurus. In another study, Yates (2003) sunk Sellosaurus into Plateosaurus (as P. gracilis).

Raeticodactylidae

Raeticodactylidae is a family of eudimorphodontoid eopterosaurian pterosaurs that lived in Switzerland during the Late Triassic. The family includes Caviramus, and the type genus Raeticodactylus, which are both known from the Kössen Formation, around 205 mya. Raeticodactylidae was first used in 2014 by Andres et al., as a group of all pterosaurs closer to Raeticodactylus than Eudimorphodon. The following phylogenetic analysis follows the topology of Andres et al. (2014).

Riojasauridae

Riojasauridae is a family of sauropod-like dinosaurs from the Upper Triassic. It is known primarily from the genera Riojasaurus and Eucnemesaurus. Sites containing Riojasauridae include the Lower Elliot Formation of Orange Free State, South Africa (where fossils of Eucnemesaurus have been found), and Ischigualasto, in La Rioja Province, Argentina ( where fossils of Riojasaurus have been recovered).

Unaysauridae

Unaysauridae is a family of basal sauropodomorphs from the Late Triassic of India and Brazil.

Xixiposaurus

Xixiposaurus is a genus of prosauropod dinosaur which existed in what is now Lower Lufeng Formation, China during the lower Jurassic period. It was first named by Sekiya Toru in 2010 and the type species is Xixiposaurus suni.

Yueosaurus

Yueosaurus is an extinct genus of basal ornithopod dinosaur known from Zhejiang Province, China.

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