Arcticodactylus

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

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 .

Contents

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 honors 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 24 centimeters (9.4 in). 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 an 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

Eudimorphodontoidea
Raeticodactylidae

Raeticodactylus filisurensis

Caviramus schesaplanensis

Eudimorphodontidae

Arcticodactylus cromptonellus

Carniadactylus rosenfeldi

Eudimorphodon ranzii

In 2020 however, a study upheld by Matthew G. Baron about early pterosaur interrelationships found Arcticodactylus to group with Carniadactylus, Raeticodactylus , and the Austriadraconidae, which in turn were within a clade he called Caviramidae. [6]

See also

Related Research Articles

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<i>Eudimorphodon</i> Genus of eudimorphodontid pterosaur from the Late Triassic

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, making Eudimorphodon one of the oldest pterosaurs known. It had a wingspan of about 100 centimeters (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.

<i>Dorygnathus</i> Genus of rhamphorhynchid pterosaur from the Early Jurassic

Dorygnathus was a genus of pterosaur that lived in Europe during the Early Jurassic period, 180 million years ago when shallow seas flooded much of the continent. It had a short 1.5 meters wingspan, and a relatively small triangular sternum, which is where its flight muscles attached. Its skull was long and its eye sockets were the largest opening therein. Large curved fangs that "intermeshed" when the jaws closed featured prominently at the front of the snout while smaller, straighter teeth lined the back. Having variable teeth, a condition called heterodonty, is rare in modern reptiles but more common in primitive pterosaurs. The heterodont dentition in Dorygnathus is consistent with a piscivorous (fish-eating) diet. The fifth digit on the hindlimbs of Dorygnathus was unusually long and oriented to the side. Its function is not certain, but the toe may have supported a membrane like those supported by its wing-fingers and pteroids. Dorygnathus was according to David Unwin related to the Late Jurassic pterosaur, Rhamphorhynchus and was a contemporary of Campylognathoides in Holzmaden and Ohmden.

<i>Peteinosaurus</i> Genus of pterosaur from the Late Triassic

Peteinosaurus was a prehistoric genus of pterosaur. It lived in the late Triassic period in the late Norian age, and at a wingspan of around 60 cm (24 in), was one of the smallest and earliest pterosaurs.

<i>Campylognathoides</i> Genus of campylognathoidid pterosaur from the Early Jurassic

Campylognathoides is a genus of pterosaur discovered in the Württemberg Lias deposits of Germany; this first specimen however, consisted only of wing fragments. Further better preserved specimens were found in the Holzmaden shale; based on these specimens, Felix Plieninger erected a new genus.

<i>Austriadactylus</i> Genus of preondactylian pterosaur from the Late Triassic

Austriadactylus is a genus of "rhamphorhynchoid" pterosaur. The fossil remains were unearthed in Late Triassic rocks of Austria.

Caviramus is a genus of caviramid pterosaur from the Late Triassic lower Kössen Formation of the Northern Calcareous Alps of Switzerland.

<i>Dendrorhynchoides</i> Genus of anurognathid pterosaur from the Middle Jurassic

Dendrorhynchoides was a genus of anurognathid pterosaur containing only the holotype species D. curvidentatus that is known from the Middle Jurassic Tiaojishan Formation of Qinglong, northern Hebei Province, China.

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.

Forni Dolostone

The Forni Dolostone, also known as the Dolomia di Forni, is a Late Triassic dolomite geological formation in northeastern Italy. The formation was deposited in a lagoonal to shallow marine environment.

<i>Carniadactylus</i> Genus of pterosaur from the Late Triassic

Carniadactylus is a genus of pterosaur which existed in Europe during the Late Triassic period. The genus contains a single species, Carniadactylus rosenfeldi.

Eopterosauria Clade of basal pterosaurs

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).

Eudimorphodontidae Family of eopterosaurs from the Late Triassic

Eudimorphodontidae is an extinct family of early pterosaurs from the Late Triassic 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, but they didn't defined the clade. Brian Andres define Eudimorphodontidae and found Peteinosaurus to be most closely related to it. Furthermore, he found monophyletic Eudimorphodon clade, 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.

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.

<i>Bergamodactylus</i> Genus of campylognathoidid pterosaur from the Late Triassic

Bergamodactylus is a putative genus of basal pterosaur which lived during the Late Triassic in the area of present-day Bergamo province in Italy. Its only species is Bergamodactylus wildi. It was named in 2015 based on a pterosaur specimen which had previously been regarded as a juvenile Eudimorphodon or as identical to Carniadactylus. Some Triassic pterosaur specialists consider the distinguishing features of Bergamodactylus to be invalid or insufficient to distinguish it from Carniadactylus, and thus retain the specimen in that genus.

<i>Douzhanopterus</i> Genus of monofenestratan pterosaur from the Late Jurassic

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<i>Caelestiventus</i> Genus of dimorphodontid pterosaur from the Late Triassic

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<i>Seazzadactylus</i> Genus of austriadraconid pterosaur from the Late Triassic

Seazzadactylus is a basal pterosaur genus that during the late Triassic lived in the area of present Italy.

<i>Mimodactylus</i> Genus of mimodactylid pterosaur from the Late Cretaceous

Mimodactylus is a genus of mimodactylid pterodactyloid pterosaur from the Late Cretaceous of what is now Lebanon.

Caviramidae Family of basal pterosaurs from the Late Triassic

Caviramidae is a group of basal pterosaurs. It was erected by paleontologist Matthew G. Baron in 2020. It was defined as the least inclusive clade that includes Arcticodactylus cromptonellus and Caviramus schesaplanensis.

References

  1. 1 2 3 4 5 Jenkins, F. A. Jr.; Shubin, N. H.; Gatesy, S. M.; 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. 1 2 3 4 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. doi: 10.1590/0001-3765201520150307 . PMID   26131631.
  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 . PMID   26339122.
  6. Matthew G. Baron (2020). "Testing pterosaur ingroup relationships through broader sampling of avemetatarsalian taxa and characters and a range of phylogenetic analysis techniques". PeerJ. 8: e9604. doi:10.7717/peerj.9604. PMC 7512134. PMID   33005485.