| Tethydraco | |
|---|---|
 | |
| Holotype humerus | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | †Pterosauria |
| Suborder: | †Pterodactyloidea |
| Superfamily: | †Ornithocheiroidea |
| Genus: | †Tethydraco Longrichet al.,2018 |
| Type species | |
| †Tethydraco regalis Longrichet al., 2018 | |
Tethydraco is a genus ofpterodactyloidpterosaur that lived during theLate Cretaceous period (Maastrichtian stage) of what is now the area of presentMorocco, about 66 million years ago.Tethydraco was originally assigned to the familyPteranodontidae. Some researchers argued that subsequently described material suggests that it may have been anazhdarchid, and possibly synonymous withPhosphatodraco, though this has been disputed. Thetype and only species isT. regalis.[1]
Since 2015, a group of paleontologists has been acquiring pterosaur fossils from commercial Moroccan fossil traders, who obtain these from workers in thephosphate mines on theKhouribga plateau, which is located within theOuled Abdoun Basin. The purpose of this project is to determine pterosaur diversity in the latest Cretaceous. From this stage, noKonservat-Lagerstätten are known, sites combining a large variety of species with exceptional preservation. It is in such sites that the vast majority of pterosaur fossils and taxa have been discovered. The latest Cretaceous had only produced some partial skeletons ofAzhdarchidae. Researchers usually have concluded from this fact that other pterosaur groups had already gone extinct. However, an alternative explanation could be that the poorfossil record caused a distorted image of the true situation through undersampling. To test this hypothesis, an effort was made to collect all pterosaurs bones brought to light by the massive and systematic commercial exploitation of the Khourigba phosphate layers. It transpired that indeed some finds could not be determined as azhdarchids and likely represented other groups. Four of the findings were described as new species in 2018, including Tethydraco.[1]
In 2018, Nicholas R. Longrich, David M. Martill and Brian Andres described and named the type speciesTethydraco regalis. The generic name combines a reference to theTethys, the ocean in the Late Cretaceous separating Africa from Europe and Asia, with aLatindraco, "dragon". Thespecific name means "royal" in Latin.[1]
Theholotype,FSAC-OB 1, was found in the middleCouche III, itself the lowest phosphate layer complex atSidi Daoui, dating from the lateMaastrichtian. It consists of a left humerus. The bone is relatively crushed. Other specimens have been referred to the species. FSAC-OB 199 is an ulna. FSAC-OB 200 is another ulna. FSAC-OB 201 is a thighbone. FSAC-OB 202 consists of a thighbone with shinbone. The describing authors admitted that a connection between the holotype and the referred specimens is hard to prove, in view of the lack of overlapping material. However, the wide ulnae fit the exceptional distal width of the humerus. The thighbones were, more tentatively, referred because they seemed to bepteranodontid.[1]
Tethydraco had a wingspan of 5 meters (16 ft) and a body mass of 15 kg (33 lb).[1][2]
The describing authors indicated some traits in whichTethydraco could be distinguished from known pteranodontids. In the humerus, the deltopectoral crest is placed rather proximally, closer to the torso of the animal, its closest border being positioned just proximal to the beginning of the opposite crest, thecrista ulnaris. Distally, away from the torso, the humerus has a broad triangular expansion. The bone ridge running to the outer joint condyle has a distinct process pointing to above, when the wing is in a stretched position. The ridge leading to the inner condyle is enlarged and extends towards the torso over a long distance. The ulna is relatively short and wide while its proximal end, towards the humerus, is massively expanded.[1]
Tethydraco was placed in the familyPteranodontidae; it would have been the youngest known member of that family, since its fossil remains dated back 66 million years ago. Its existence was seen as proof that pterosaur diversity in the Maastrichtian was higher than previously assumed. Apparent pterosaur decline would have been an illusion caused by theSignor–Lipps effect, groups seeming to disappear earlier than amass extinction because their youngest fossils by chance have been found at somewhat older layers than the extinction event.[1]
Below is acladogram showing the results of aphylogenetic analysis first presented by Andres and colleagues in 2014, and updated with additional data by Longrich and colleagues in 2018. In this analysis, they foundTethydraco to be the sister taxon of the two species ofPteranodon (P. longiceps andP. sternbergi); all three of them forming the family Pteranodontidae, which is found as the sister taxon of the familyNyctosauridae.[3][1]
In 2021, Labita and Martill assigned a partial right wing (FSAC CP 251) from the same deposit toTethydraco, but classified the genus as an azhdarchid possibly representing the wing-elements ofPhosphatodraco based on its morphology, rather than a pteranodontid as originally proposed.[4] In 2022, the describers ofEpapatelo noted that the humerus ofEpapatelo shares similarity with that ofTethydraco and other non-Nyctosaurus pteranodontoids, and recoveredTethydraco as a pteranodontian closely related toPteranodon.[5] In 2023, Pentland and Poropat noted that while the hatchet-shaped deltopectoral crest of FSAC CP 251 is consistent with Azhdarchidae, it differs from the shape of theTethydraco holotype.[6]
Tethydraco was discovered in theOuled Abdoun Basin inMorocco. This basin is divided into layers called "Couches", andTethydraco was discovered in Couche III. It coexisted with the pterosaursAlcione,Barbaridactylus,Simurghia andPhosphatodraco and theabelisauriddinosaurChenanisaurus.[1][7]
