Arcticodactylus

Arcticodactylus is a genus of basal pterosaur living during the Late Triassic in the area of present Greenland. Its only species was previously attributed to Eudimorphodon, and its closest relatives may have been Eudimorphodon or Austriadraco.

Arcticodactylus
Temporal range: Late Triassic, 208–201 Ma
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Order: Pterosauria
Family: Eudimorphodontidae
Genus: Arcticodactylus
Kellner, 2015
Species:
A. cromptonellus
Binomial name
Arcticodactylus cromptonellus
(Jenkins et al., 2001)
Synonyms

Eudimorphodon cromptonellus Jenkins et al., 2001

History of discovery

In 1989, William Amaral on the McKnight Bjerg in the east of Greenland discovered a rich fossil site. It was excavated in 1991 and 1992. Part of the material was a small skeleton of a pterosaur. In 2001, Farish Jenkins, Neil Shubin, Stephen Gatesy and Kevin Padian named and described it as a new species of Eudimorphodon: Eudimorphodon cromptonellus. The specific name honours Professor Alfred Walter Crompton. The suffix ~ellus, in Latin indicating a diminutive, alluded to the small size of the specimen.[1]

The holotype, MGUH VP 3393, was found in the Carlsberg Fjord Beds of the Ørsted Dal Member of the Fleming Fjord Formation dating from the NorianRhaetian. It consists of a partial skeleton with skull. It is largely disarticulated.[1]

The reference to Eudimorphodon had been essentially based on the similarity in tooth form, especially the distinctive multi-cuspid build with three, four or five points on the crown. In 2003, Alexander Kellner pointed out that other basal pterosaurs also possess such teeth.[2] In 2014, Fabio Marco Dalla Vecchia noted that E. cromptonellus shared not a single trait with Eudimorphodon ranzii not present in other pterosaurs but lacked the distinguishing fang-like teeth, pterygoid teeth and striated tooth enamel.[3] In 2015, Kellner named a separate genus Arcticodactylus. The generic name is derived from the Arctic, and Greek δάκτυλος, daktylos, "finger", a usual suffix in pterosaur names since Pterodactylus. The Life Science Identifier is 72AE012A-018A-4B4B-950F-3CCB4C1D2471. The type species is Eudimorphodon cromptonellus, the combinatio nova is Arcticodactylus cromptonellus.[4]

Description

The holotype individual of Arcticodactylus is the smallest pterosaur known, with an estimated wingspan of just twenty-four centimetres. It was in 2001, on the basis of histological research of its bone structure, considered not to have been full-grown yet, though not newly born.[1]

In 2015, Kellner established some distinguishing traits, correcting and adding to the 2001 diagnosis. The jaws have eleven or twelve multi-cusped teeth per side. The articulation surface of the fourth metacarpal with the fourth finger shows two true condyles. The thighbone is only a little shorter than the shinbone, with 96% of its length. The scapula is much longer, 93%, than the coracoid. The humerus is only slightly shorter than the thighbone, with 92% of its length, or the ulna with 91% of ulnar length. The thighbone is somewhat longer than the first phalanx of the wing finger that has 91% of femoral length. The third metatarsal of the foot is elongated with 56% of shinbone length. These proportions imply that Arcticodactylus had relatively short wings and large feet.[4]

Arcticodactylus can furthermore be distinguished from Eudimorphodon in the lack of long fang-like teeth in the middle of the tooth row and from Eudimorphodon ranzii, Carniadactylus and Bergamodactylus by a triangular instead of rectangular deltopectoral crest on the humerus. Articodactylus has fewer teeth than any other known Triassic pterosaur.[4]

Jenkins e.a. claimed that the unique articulation in Arcticodactylus between the main wing metacarpal and the wing finger, with two rounded condyles, was a transitional shape between the ancestral form that featured a single rounded articulation surface on the metacarpal allowing a considerable amount of lateral movement, and the condition in later pterosaurs that showed a gentle depression or trochlea. The two condyles, the upper one the largest, would have forced the finger into the most optimal plane of movement during the upstroke of the wing.[1]

Classification

In 2001, E. cromptonellus was placed in the Eudimorphodontidae.[1] Kellner in 2015 indicated a basal position in the Pterosauria, the short coracoid suggesting a close affinity to Austriadraco within a Austriadraconidae. According to Kellner, the original describers had incorrectly identified a coracoid as a quadrate bone.[4] The following phylogenetic analysis follows the topology of Upchurch et al. (2015).[5]

Eopterosauria

Preondactylus buffarinii

Austriadactylus cristatus

Peteinosaurus zambellii

Eudimorphodontidae
Raeticodactylinae

Raeticodactylus filisurensis

Caviramus schesaplanensis

Eudimorphodontinae

Arcticodactylus cromptonellus

Carniadactylus rosenfeldi

Eudimorphodon ranzii

See also

References

  1. ^ a b c d e Jenkins, F. A. Jr., Shubin, N. H., Gatesy, S. M., and Padian, K., 2001, "A diminutive pterosaur (Pterosauria: Eudimorphodontidae) from the Greenlandic Triassic", Bulletin of the Museum of Comparative Zoology, 156: 151–170
  2. ^ Kellner, A.W.A., 2003, "Pterosaur phylogeny and comments on the evolutionary history of the group". In: Buffetaut E. and Mazin J-M. (Eds), Evolution and Palaeobiology of Pterosaurs. Geological Society of London, Special Publications 217, pp. 105-137
  3. ^ Dalla Vecchia F.M., 2014, Gli pterosauri triassici, Memorie del Museo Friulano di Storia Naturale, pubblicazione numero 54, 319 p., 266 figs, Museo Friulano di Storia Naturale, Udine
  4. ^ a b c d Kellner, Alexander W.A., 2015, "Comments on Triassic pterosaurs with discussion about ontogeny and description of new taxa", Anais da Academia Brasileira de Ciências 87(2): 669–689
  5. ^ Upchurch, P.; Andres, B.B.; Butler, R.J.; Barrett, P.M. (2015). "An analysis of pterosaurian biogeography: implications for the evolutionary history and fossil record quality of the first flying vertebrates". Historical Biology. 27 (6): 697–717. doi:10.1080/08912963.2014.939077. PMC 4536946.
Austriadraco

Austriadraco is a genus of pterosaur living during the Late Triassic in the area of present Austria. Its only species—Austriadraco dallavecchiai—was previously attributed to Eudimorphodon, and its closest relatives may have been Eudimorphodon or Arcticodactylus.In June 1994, near Seefeld in Austrian Tirol, at a 1600 metres high mountain trail to the Reither Spitze, in the vicinity of the Reither Joch-Alm, Bernd Lammerer discovered a pterosaur skeleton. The remains have been secured as five stone plates, removed on several occasions. In 2003, Peter Wellnhofer identified the fossil as a specimen of Eudimorphodon, a cf. E. ranzii. As it was 10 to 25% shorter than the latter's holotype, Wellnhofer considered it a juvenile. The same year Fabio Marco Dalla Vecchia doubted the comparability to E. ranzii and suggested that it represent a separate Eudimorphodon species. In 2009, Dalla Vecchia concluded that the specimen was neither a juvenile nor closely related to Eudimorphodon.In 2015, Alexander Kellner named the separate genus Austriadraco, with the type species Austriadraco dallavecchiai. The generic name is a combination of the Latin words Austria and draco, "dragon". The specific name honours Dalla Vecchia. The Life Science Identifiers are for the genus 120B3003-6DE3-41B4-AF6B-6F242FB2A777 and for the species 6E123721-07EA-419CB755-9981CC7D9209.The holotype, BSP 1994 I 51, was found in a layer of the Seefeld Formation, dating from the late Norian. It consists of a partial and disarticulated skeleton with skull. It contains both frontal bones, a left jugal, the lower jaws, loose teeth, vertebrae of the neck, back and tail, the shoulder girdle, both humeri, a first wing phalanx, the pelvis, a shinbone and a calf bone. The fused frontals had in 2003 been incorrectly identified as a breast bone by Wellnhofer. The bones have been partly preserved as impressions only and many are fragmented. The fossil is part of the collection of the Bayerische Staatssammlung für Paläontologie und historische Geologie at Munich.Austriadraco dallavecchiai is a small species. Humerus length is about four centimetres. In 2015 Kellner indicated several distinguishing traits. Some of these are autapomorphies. The frontal bone has a short front branch. The jugal bone has short branches to the front, in the direction of the maxilla and the nasal bone, and a long narrow upwards branch running towards the postorbital bone. In the outer rear side of the lower jaw an opening is present, the mandibular fenestra. The coronoid process of the surangular bone is low. The shoulder blade is considerably longer, 62%, than the coracoid.Additionally, a unique combination of in themselves not unique traits is present. The coracoid is broad, with a constricted shaft. In the pelvis, the ischipubic plate, the fusion of the pubic bone with the ischium, is deep. The shinbone is relatively long, with a length of 57.7 millimetres attaining 70% of the length of the humerus and 92% of the length of the first phalanx of the (fourth) wingfinger.According to Dalla Vecchia's analysis, Austriadraco would have a very basal position in the Pterosauria. Kellner concluded that its affinities were uncertain and placed Austriadraco in a separate, undefined, Austriadraconidae. He suggested a close relationship with Arcticodactylus as both taxa shared the trait of a short coracoid.

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.

Caelestiventus

Caelestiventus ( sə-LES-tih-VEN-təs, meaning "heavenly wind") is a pterosaur genus from the Late Triassic (Norian or Rhaetian) found in western North America. The type species, Caelestiventus hanseni, honors Robin Hansen, the Bureau of Land Management geologist (BLM), who facilitated access to the excavation site.

Caelestiventus is important because it is the sole example of a desert-dwelling non-pterodactyloid pterosaur and is 65 million years older than other known desert-dwelling pterosaurs. Additionally, it shows that even the earliest pterosaurs were morphologically and ecologically diverse and that the Dimorphodontidae originated in the Triassic Period.

Carniadactylus

Carniadactylus is a genus of pterosaur which existed in Europe during the Late Triassic period (late Carnian or early Norian, about 228 million years ago). The genus contains a single species, Carniadactylus rosenfeldi.

Caviramus

Caviramus is a genus of "rhamphorhynchoid" pterosaur from the Late Triassic (late Norian-early Rhaetian-age) lower Kössen Formation of the Northern Calcareous Alps of Switzerland.

The genus was in 2006 named by Nadia Fröbisch and Jörg Fröbisch. The type species is Caviramus schesaplanensis. The genus name is derived from Latin cavus, "hollow" and ramus, "branch". The specific name refers to Mount Schesaplana.

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.

Eopterosauria

Eopterosauria is a group of basal pterosaurs from the Triassic, which form their own clade. The term was first used in Andres et al. (2014) to include Preondactylus, Austriadactylus, Peteinosaurus and Eudimorphodontidae. Inside the group were two other new clades, Preondactylia, which included Preondactylus and Austriadactylus, and Eudimorphodontoidea, to include Eudimorphodontidae and Raeticodactylidae. Eopterosauria was defined as "the least inclusive clade containing Preondactylus buffarinii and Eudimorphodon ranzii". The specimen BSP 1994, previously assigned to Eudimorphodon, was named the separate taxon Austriadraco in 2015, and assigned to the new family Austriadraconidae, but further classification was not described. The following phylogenetic analysis follows the topology of Andres et al. (2014).

Eudimorphodon

Eudimorphodon was a pterosaur that was discovered in 1973 by Mario Pandolfi in the town of Cene, Italy and described the same year by Rocco Zambelli. The nearly complete skeleton was retrieved from shale deposited during the Late Triassic (mid to late Norian stage), making Eudimorphodon one of the oldest pterosaurs known. It had a wingspan of about 100 centimetres (3.3 ft) and at the end of its long bony tail may have been a diamond-shaped flap like in the later Rhamphorhynchus. If so, the flap may have helped it steer while maneuvering in the air. Eudimorphodon is known from several skeletons, including juvenile specimens.

Eudimorphodontidae

Eudimorphodontidae is an extinct family of early pterosaurs from the Late Triassic (early Norian to Rhaetian age) of Europe. It was named by Peter Wellnhofer in 1978 to include Eudimorphodon ranzii. Some phylogenetic analyses suggested that Eudimorphodontidae is a junior synonym of Campylognathoididae, however more comprehensive analyses found Eudimorphodontidae to be basal to Macronychoptera that includes Campylognathoididae and more derived pterosaurs (Breviquartossa). Wang et al. (2009) found Eudimorphodontidae to include six species (the monospecific Peteinosaurus, Raeticodactylus and Caviramus, and three species of Eudimorphodon), but they didn't defined the clade. Brian Andres (2010, in press) define Eudimorphodontidae and found Peteinosaurus to be most closely related to it. Furthermore, he found monophyletic Eudimorphodon clade (unlike Wang et al., 2009 and Dalla Vecchia, 2009), and defined two subfamilies within Eudimorphodontidae. The Eudimorphodontinae includes all taxa more closely related to Eudimorphodon ranzii than to Raeticodactylus filisurensis while the Raeticodactylinae includes all taxa more closely related to Raeticodactylus filisurensis than to Eudimorphodon ranzii. More recently, Raeticodactylus and Caviramus were moved into their own family, Raeticodactylidae. The below cladogram follows that analysis.

Jingshanosaurus

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

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.

Peteinosaurus

Peteinosaurus ( peh-TY-nə-SOR-əs; meaning "winged lizard") was a prehistoric genus of Pterosaur. It lived in the late Triassic period in the late Norian age (about 221 to 210 million years ago), and at a wingspan of around 60 cm (24 in), was one of the smallest and earliest Pterosaurs.

Preondactylus

Preondactylus is a genus of long-tailed pterosaurs from the Late Triassic (late Carnian or early Norian age, about 228 million years ago) that inhabited what is now Italy. It contains a single known species, Preondactylus buffarinii, which was discovered by Nando Buffarini in 1982 at the Forni Dolostone near Udine in the Preone valley of the Italian Alps.

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).

Raeticodactylus

Raeticodactylus is a genus of non-pterodactyloid pterosaur from the late Norian-early Rhaetian-age Upper Triassic lower Kössen Formation of the central Austroalpine of Grisons, Switzerland. It is known from holotype BNM 14524, a single disarticulated partial skeleton including an almost complete skull, found in August 2005. This genus was named and described in 2008 by its discoverer Rico Stecher; the type species is Raeticodactylus filisurensis. The specific name refers to Filisur.

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.

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