Dearc
| Dearc Temporal range: Middle Jurassic,
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Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Order: | †Pterosauria |
| Family: | †Rhamphorhynchidae |
| Subfamily: | †Rhamphorhynchinae |
| Tribe: | †Angustinaripterini |
| Genus: | †Dearc Jagielska et al., 2022 |
| Species: | †D. sgiathanach
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| Binomial name | |
| †Dearc sgiathanach Jagielska et al., 2022
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Dearc (Scottish Gaelic pronunciation: [tʲɛrxk] ) is a genus of large-bodied rhamphorhynchine pterosaur from the Middle Jurassic of Scotland. The holotype, a juvenile or subadult that was still actively growing, has an estimated wingspan of 2.5 to 3 meters, making it the largest flying animal of its time. This pushes the origin of large pterosaurs back significantly, as it was previously assumed that pterosaurs didn't reach greater body sizes until the short tailed pterodactyloid lineages of the Cretaceous. The genus contains a single species, Dearc sgiathanach ([ˈtʲɛɾxk ˈs̪kʲiəhanəx] ).[1]
History and naming
The holotype of Dearc was found in 2017 by Amelia Penny in the Lealt Shale Formation and consists of a three-dimensionally preserved skeleton preserved in articulation in a slab of limestone (separated into 4 pieces for preparation). The specimen preserves most of the body with the exception of the end of the tail, hindlimbs, parts of the wing and the very tip of the beak. The specimen was found near Trotternish on the Isle of Skye in north-west Scotland, and the rock slab removed to the University of Edinburgh.[2] It is to be displayed by National Museums Scotland.[2]
The name derives from the Scottish Gaelic language. The name has a double meaning, simultaneously translating to "winged reptile" and "reptile from Skye". The first translation is a reference to pterosaurs as a whole, while the later translation indicates that it was found on the Isle of Skye (An t-Eilean Sgitheanach, The Winged Island in Scottish Gaelic).
Description
Dearc possesses several features typical of fully grown adults in the related Rhamphorhynchus, including the large recurved teeth of the premaxilla, the well developed crest of the humerus, fusion between the scapula-coracoid, smooth bone texture and other features. However, at the same time other areas of the fossil show signs of immaturity, including unfused bones of the skull and unfused sacral vertebrae. Histology supports the later interpretation, indicating that, while at least 2 years old at its time of death, the animal was still actively growing. The wing bone shows two prominent lines of growth that allow this interpretation and further suggest that it died shortly after emerging from a hiatus in growth.
The wingspan could not be directly meassured for Dearc as several phalanges of the wingfinger were missing, in particular the very tip and a central portion of the wing. However, an estimate could be made based on comparisson with better sampled taxa, in this case Rhamphorhynchus and Dorygnathus. Using the proportions of Rhamphorhynchus, an estimated wingspan between 2.2 meters (based on skull length) and 3.8 meters (based on humerus length) was recovered. Estimates based on the humerus length of Dorygnathus give an estimated wingspan of 1.9 meters. These results already make Dearc the largest known Jurassic pterosaur, larger than the largest Rhamphorhynchus and Dorygnathus (1.8 and 1.69 meters wingspan respectively). The larger interpretation is favored by the authors for a series of reasons including the well established ontogenetic series of Rhamphorhynchus, phylogenetic proximity and the fact that Dearc was still growing, making a wingspan of up to 3 meters quite possible.
Generally, Dearc shows the typical bodyplan of non-monofenestratan pterosaurs. The neck was short and the tail elongated, supported by interlocking zygapophyses of the caudal vertebrae. The madibular symphysis is elongated and the metacarpus short. There are however some features shared with pterodactyloids such as a skull longer than the dorsal and sacral vertebrae combined and the shape of the quadrate. Furthermore, although proportinally short compared to pterodactyloids, the cervical vertebrae are notably elongated compared to other non-monofenestratans, resembling those of the more derived Wukongopterus. The dentition shows two distinct types of teeth: elongated fangs close to the tip of the snout and more conical peg-like teeth further back.
Phylogeny
The phylogenetic analysis conducted for Dearc included characters from several independent publications as well as entirely new ones, while also excluding those that are only known from very young animals or known to vary greatly with age. The resulting tree recovered Dearc to lie within the Rhamphorhynchidae, specifically in a clade alongside Angustinaripterus and Sericipterus, the Angustinaripterini.
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References
- ^ Natalia Jagielska; Michael O’Sullivan; Gregory F. Funston; et al. (February 2022). "A skeleton from the Middle Jurassic of Scotland illuminates an earlier origin of large pterosaurs". Current Biology. 32: 1–8. doi:10.1016/J.CUB.2022.01.073. ISSN 0960-9822. Wikidata Q110984418.
- ^ a b "Fossil of largest Jurassic pterosaur found on Skye". BBC News. 22 February 2022. Retrieved 22 February 2022.
