In 2018 paleontologists Nick Longrich, David Martill, and Brian Andres named a new species of pteranodontid, Tethydraco regalis, from the Upper Cretaceous Couche III beds at the Sidi Daoui phosphate mines near Khouribga, Morocco. These rocks were formed in the final one million years of the Mesozoic Era and represent some of the last species of pterosaurs that lived before the K-Pg Extinction. Tethydraco is based on an isolated humerus which serves as the holotype, and several referred limb bones including two ulnae, a femur, and an articulated femur and tibia. The name translates to “royal Tethys dragon,” a reference to the ancient Tethys Ocean, which once spanned between northern Africa and Eurasia.
The humerus is 23 cm (9 inches) long and mostly complete, only missing the head which articulated with the shoulder joint. Its distal end is a broad and triangular, tapering toward the middle. Near the shoulder joint, a prominent flange of bone called the deltopectoral crest rises from the front side of the humerus, nearly at a right angle to the flattened triangular distal end. The deltopectoral crest is narrowest on its proximal and distal surfaces, but forms a massive pillar of bone at its center. The apex of the crest is thickened and curls slightly backward. The deltopectoral crest anchored the powerful deltoid and pectoral muscles, which were greatly enlarged for flapping flight in pterosaurs.
The referred ulnae are robust and quite similar to ulnae of Pteranodon. They are unique by having the proximal end becoming gradually broader and flatter. The leg bones are also quite similar to Pteranodon, but the tibia is proportionally shorter in Tethydraco. Although incompletely known, Tethydraco probably had a wingspan of about 5 meters (16.5 feet), about the same size as many male individuals of Pteranodon.
Longrich, Martill, and Andres noted several anatomical similarities shared by Pteranodon and Tethydraco, but not other pterosaur species. The authors performed a phylogenetic analysis and found that Tethydraco was indeed a pteranodontid, living about 15 million years after its Kansan cousins. Other pteranodontids were toothless marine fishers with long slightly upwardly curving bills, and prominent head crests. Pteranodon is known from hundreds of specimens in at least two species, and shows strong sexual dimorphism where males are physically larger and have much larger and more prominent crests. Although nothing is known of the skull in Tethydraco, it too probably had a prominent head crest and may have been sexually dimorphic as well.
At the time Tethydraco lived, about 67 million years ago, global sea levels were higher than today and the modern phosphate mines were under water several kilometers out to sea. Africa was further south than it is now, and the nearby coast would have been rocky and arid, much like the coastal areas in modern Yemen. The phosphate mines preserve fossils of at least seven species of pterosaurs from three families, showing that pterosaur diversity remained high until the mass extinction. In addition to the pterosaurs, abundant fossils of marine reptiles, fish, and marine invertebrates are known from the locality.