Europejara

The Castilla-La Mancha region of eastern Spain contains many rich fossil localities spanning from the Precambrian to the Pleistocene, and the Las Hoyas site of Serranía de Cuenca in the southwestern Iberian ranges has been particularly noted for its exceptional Konservat-Lagerstätte preservation. The locality belongs to the La Huérguina Formation and dates to the late Barremian age of the Early Cretaceous epoch. The site was discovered in 1985, and since then, nearly 30 excavation campaigns have yielded over 19,000 fossils, housed at the Sciences Museum of Castilla-La Mancha in Cuenca. The completeness of the site's fossil flora and fauna has given it worldwide scientific renown, and it was declared a Site of Cultural Interest in 2016.^[1][2]

In 2012, the palaeontologist Romain Vullo and colleagues reported an incomplete skull of a new pterosaur from Las Hoyas, the first member of the family Tapejaridae known from Europe, adding to the poorly known pterosaur fauna of the locality. Previously, tapejarids were only unambiguously known from Brazil and China, where pterosaur fossils of similar age are more abundant and complete than in Europe. At the time, the specimen was also the oldest known tapejarid and oldest known toothless pterosaur. The specimen (designated as MCCM-LH 9413 in the Sciences Museum) was made the holotype of the new genus and species Europejara olcadesorum. The generic name combines the names of Europe (itself derived from Europa, a Phoenician princess of Greek mythology) where it was found, and the related genus Tapejara, the Brazilian genus that defines the clade Tapejarinae. The name Tapejara itself is composed of the Tupí-Guaraní words tapi or tape, which means 'path', and yara or jara, which means 'lord'. The specific name refers to the Olcades, an ancient Celtiberian people from Hispania that first inhabited the region of Cuenca.^[2][3]

The holotype consists of the hind part of a skull with lower jaws, compressed on a slab and counterslab. Several scattered scleral ring plates (that formed a bony ring inside the eye) and two elements of the hyoid (tongue bone) are also present. The skull is crushed and flattened from top to bottom, with various bones displaced, and the mandible is almost complete. No integument, such as soft tissue and keratinous parts, is preserved. The preparation of the specimen included removing elements from the fossil matrix with acid, and it was photographed under ultraviolet light for its description. The fossil was presented at an "open doors" event in 2012, which included the best Las Hoyas fossils of the Sciences Museum, where the audience interacted with the researchers who showed study techniques.^[2]

Based on the proportions of other tapejarids, Europejara was a relatively small pterosaur, with an estimated wingspan of 2 m (6.6 ft).^[2][4] Tapejarids are characterised by their short faces and downturned jaw tips, and most mature skulls had two crests on their upper surface, one at the front (on the premaxilla, the frontmost bone of the upper jaw) and one at the back, with keratinous soft-tissue structures occupying the space between the two. The lower jaws of adults had a rounded crest projecting down from the dentary bone at the mandibular symphysis (where the two halves of the mandible connected at the front). Although Europejara is only known from skull bones, relatives had comparatively robust and complex limb girdles, elongated limbs for their body size, but rather short wing fingers and feet, and very short tails.^[4][2] As a pterosaur, Europejara was covered with hair-like pycnofibres and had extensive wing membranes (which were extended by the wing finger).^[5]

What is preserved of the holotype skull is incomplete and flattened from top-to-bottom, whereas the mandible is preserved in side view. The preserved fragments of the skull mainly represent elements from the area around the right orbit (eye socket). Both maxillae (the bone that forms most of the upper jaw) are preserved, though incompletely, in top view, and form an angle of around 12 degrees. The postorbital bone (the bone behind the orbit) is roughly triangular, with no visible suture (joint) between it and the jugal bone (or cheek bone) underneath.^[2]

The scleral plates are trapezoidal in shape and thin. A lacrimal bone was tentatively identified and is typical for tapejarids, being thin and fenestrated (with openings). The lower temporal fenestra (the opening behind the orbit) at the back of the skull was narrow, as indicated by the position of the quadrate bone. The palate is preserved in top view and has two narrow, elongated choanae (internal nostrils), separated by a thin vomer. The hyoid apparatus, a structure involved in supporting the tongue and larynx, is preserved in the form of the first pair of ceratobranchial bones. Each is about 135 mm (5.3 in) in length and 2 mm (0.079 in) in diameter, and their hind half is slightly curved.^[2]

The preserved part of the almost complete mandible is 230 mm (9.1 in), with an estimated total length of 255 mm (10.0 in), and each mandibular ramus (half) is 22 mm (0.87 in) in height. Most of their length consists of the dentary bones. The mandibular rami are robust and their upper and lower borders are parallel. The outer side surface of each ramus is smooth while the inner surface has shallow, well-marked depressions, and there is a bulge on the upper, inner surface of each dentary, a distinguishing combination for this genus. In side view, the cutting edge of the dentaries is slightly sigmoid curved in the area of the mandibular symphysis. The upper surface of the symphysis is concave in cross-section.^[2]

Europejara had a deep, bony crest that projected down from the dentaries and was distinct from those of its relatives in being recurved backwards and in being more developed from top to bottom than from front to back. The crest was at least 90 mm (3.5 in) deep, four times deeper than the back of the lower jaw and therefore proportionally deeper than in other tapejarids. The dentary crest of Europejara was larger, better developed and deeper than those of the Chinese tapejarids Sinopterus and Huaxiadraco, while those of the Brazilian Tapejara and Tupandactylus were longer from front to back. Both the premaxillary and dentary crests are low in Sinopterus and Huaxiadraco, while they are well-developed in Tapejara and Tupandactylus, indicating that their dimensions can be roughly correlated in tapejarids. Vullo and colleagues therefore inferred that the deep dentary crest of Europejara suggested that its premaxillary crest was relatively high, and may have been backwards recurved, reflecting the shape of the dentary crest.^[2]

Europejara was found to be a member of the pterosaur family Tapejaridae by Vullo and colleagues in the phylogenetic analysis accompanying their 2012 description. At the time, this group was divided into two subfamilies; the long-faced and large Thalassodrominae, and the short-faced and smaller Tapejarinae, both with well-developed cranial crests. Europejara was assigned to the latter due to the presence of a dentary crest and a step-like upper edge at the symphyseal area of the dentary, a unique feature of tapejarines. The position of Europejara within Tapejarinae was poorly resolved due to its incompleteness. The describers stated that the presence of a tapejarid in Spain during the Barremian shows that the group was distributed earlier and broader throughout the palaeocontinents of Gondwana (the southern continent) and Laurasia (the northern continent), living from Brazil to China.^[2]

Despite its phylogenetic position within Tapejarinae being unresolved, the describers suggested that it might be sister group to a clade consisting of taxa from Brazil and China, which would be the most stratigraphically sound conclusion, as grouping Europejara with Chinese tapejarines would be inconsistent unless older Gondwanan taxa were found. They also found that the oldest tapejarids being from the late Barremian of Spain and China supported the view that the group originated in Eurasia near the beginning of the Early Cretaceous rather than in Gondwana, and could have spread to Brazil during the later Aptian. Furthermore, the occurrence of a tapejarid in the Cenomanian of Morocco suggests that the group diversified in Gondwana during the mid-Cretaceous, but these authors cautioned that knowledge about tapejarid evolution and palaeobiogeography was affected by uneven fossil sampling, and that the absence of the group in North American, European and African deposits from the Aptian–Albian could be due to the lack of pterosaur-bearing sites of those times and places.^[2]

In 2016, the palaeontologist Rubi Vargas Pêgas and colleagues recovered Europejara as sister group of the Brazilian genera Caiuajara, Tapejara, and Tupandactylus. Earlier studies found Chinese tapejarines to be basal (earlier diverging) to the Brazilian taxa, concluding that Laurasia was therefore the group's likely place of origin, with the older age of these and Europejara used as argument. Pêgas and colleagues noted that since Chinese tapejarines form a monophyletic (natural) clade instead of a paraphyletic (unnatural) group, this does not give support for a Laurasian origin over a Gonwanan one, and their sister group Thalassodrominae was restricted to South America. On the other hand, the existence of early tapejarines in Brazil and the exclusive presence of Thalassodrominae there points in favour of an origin for the group in Gondwana. That Chinese tapejarines were monophyletic would support a single dispersal to China, while being related to South American tapejarines, Europejara would represent another dispersal in Europe, but the authors noted more work was needed to support this interpretation.^[6]

The palaeontologist Alexander W. Kellner, one of the describers of Europejara, and colleagues named the tribe Tapejarini for the clade containing Europejara and its Brazilian relatives in 2019.^[7] The palaeontologist Gabriela M. Cerqueira and colleagues reached similar conclusions as Pêgas and colleagues in 2020.^[8] The cladogram below follows a phylogenetic analysis by Pêgas and colleagues in 2024, following a scheme where thalassodromids were excluded from Tapejaridae and considered their own family.^[9]

Vullo and colleagues found the shape of Europejara's dentary crest unlike any before described among pterosaurs. They noted that the purpose of such a deep and recurved crest at the midline of the mandible remains unclear, but there may have been multiple functions, such as use in aerodynamics, thermoregulation, social behavior, or to support a gular pouch. Well-developed bony cranial crests are known from various pterosaur groups, but mandibular crests are only known from anhanguerids and tapejarids, as well as some early non-pterodactyloids (long-tailed pterosaurs).^[2]

The palaeontologist Mark Witton summarised ideas of tapejarid locomotor abilities in 2013, stating they were adaptable, generalist fliers, similar to extant parrots and crows. Their relatively short wings appear consistent with flying in inland areas and their long limbs and probably well-muscled limb girdles would have made them adept at launching and flapping. It is uncertain what effect their large crests had on their flight abilities, and Witton considered a primary role in display and socialisation most likely, but their presence would have impacted their steering and speed in windy conditions for better or worse. Tapejarids would have been proficient on the ground owing to their long, powerful limbs and compact, padded feet.^[4]

Diet

As Europejara showed tapejarids were the oldest known certainly toothless pterosaurs, Vullo and colleagues pointed out this might have been linked to the group developing new feeding strategies during the Early Cretaceous (145–99 million years ago); toothlessness probably evolved independently at least three times among pterosaurs. They noted that tapejarids are thought to have been good fliers with excellent vision, and have mainly been considered frugivorous (fruit-eaters) and/or granivorous (seed-eaters), based on their short skulls, downturned jaws, and unusually shaped toothless jaws. The beak was probably covered by a rhamphotheca (a keratinous covering), and while shaped like the underlying bone as in modern birds, the bills of some tapejarids might have had pointed projections as in omnivorous birds such as toucans. This indicates tapejarids could also have had a herbivorous or omnivorous diet that included seeds, fruits, insects, and small vertebrate animals, but such assumptions lack fossil evidence.^[2]

The Cretaceous Terrestrial Revolution is a turn-over event in the ecosystems of the Cretaceous in which gymnosperm plants were replaced by angiosperms, flowering plants, associated with the diversification of insects, birds and mammals. Vullo and colleagues noted that the role of pterosaurs had not been previously considered in this event, but pointed out that an effective mode of seed dispersal by vertebrates would have aided the rapid, worldwide spread of angiosperms. The Early Cretaceous La Huérguina Formation in Spain and the Yixian and Jiufotang formations in China preserve fossils of organisms that may have lived in subtropical wet, forested and lacustrine (associated with lakes) environments that contained an abundance of early angiosperms, and these authors found this to support the presence of frugivorous and granivorous pterosaurs that would have dispersed seeds with birds and insects.^[2]

Tapejarids were part of these trophic networks during the Cretaceous Terrestrial Revolution and their distinct features may have been connected to angiosperm dispersal; tapejarids and early angiosperms radiated synchronously and had a similar patchy distribution in time and space. Vullo and colleagues therefore suggested that the Barremian–Aptian distribution of tapejarids partially coincided with the first phase of angiosperm radiation in both the world's hemispheres. Angiosperm diversification during that time is well-documented from Iberian fossils and the Aptian–Albian Crato and Santana formations of Brazil also have early angiosperm assemblages and tapejarids. The describers considered this evidence for congruence between the early radiation of angiosperms and tapejarids, and that these pterosaurs were one of the biological vectors involved in dispersing the flowers between landmasses, but cautioned that more research was required to establish whether the two groups co-evolved or if tapejarids were incidental vectors, with more fossils and gut-content needed for confirmation.^[2]

In 2025, the palaeontologist Shunxing Jiang and colleagues reported stomach contents from a specimen of the tapejarid Sinopterus. These include gastroliths (stones used to aid food processing in the gizzard) and the first evidence of phytoliths in pterosaurs (minerals found in certain plants which persist after their decomposition), and the first evidence of these co-occurring in a pterosaur. Some of the phytoliths were identified as the angiosperm family Poaceae as well as gymnosperms or ferns, indicating Sinopterus had a diverse diet of plants. While noting that tapejarids and some other pteosaurs had earlier been suggested as herbivorous based on indirect evidence, these researchers considered the gut contents confirmation of herbivory, and excluded a generalist diet for Sinopterus as for example no undigested bones, scales, or insect exoskeletons were found. They also stated that bite force estimations of Tapejara had suggested a herbivorous diet of fruits, seeds, and more resistant plant matter, and added that the similarity between their skulls indicated similar bite forces, supporting a herbivorous diet for both.^[10]

Field work at the Las Hoyas site in 2018 (left), and fossil of the dinosaur Concavenator from there

The Las Hoyas site in the La Huérguina Formation, from which Europejara was recovered, has been dated to the late Barremian (about 129.4–126.3 million years ago) based on assemblages of charophyte algae and ostracod crustaceans,^[11] and the fossiliferous deposits are composed of laminated limestone and marlstone.^[2] These deposits represent a continental, subtropical wetland environment,^[12] between a lacustrine environment and a tree fern-dominated savannah, which overlaid a low-relief karstic terrain. The vertebrate fossils of this Konservat-Lagerstätte are notable for their articulation and preservation of mineralised soft tissue, but also includes more incomplete, isolated remains. Preservation at the Las Hoyas site is so precise that certain taxa, such as the mammal Spinolestes, have been preserved with their internal organs intact, and even bacteria have been reported.^[11][2]

More than twenty thousand plant and animal fossils are known from Las Hoyas. The biota of Las Hoyas is intermediate between Jurassic and other Early Cretaceous biotas, and is thus representative of the early stages of the Cretaceous Terrestrial Revolution.^[11] The terrestrial macroflora of Las Hoyas is dominated by conifers of the family Cheirolepidiaceae and ferns of the families Matoniacea and Schizaeaceae, as well as relatively diverse angiosperms.^[2] Plants known from the site include the ferns Cladophlebis and Weichselia. The oldest angiosperm macrofossil, the aquatic Montsechia, comes from this site.^[13] While most of the terrestrial plant microfossils from the formation are pteridophytes and gymnosperms, there is a significant amount of angiosperm pollen grains, such as Afropollis and Clavatipollenites, as well as leaves.^[2]

The biota of Las Hoyas consists mainly of aquatic organisms, with amphibious forms being less abundant, terrestrial forms being rare, and large forms (such as dinosaurs) being exceptional. Pterosaurs are rare; in addition to Europejara, a few teeth indicate the presence of a large anhanguerid and a small istiodactylid.^[2] Non-avian theropod dinosaurs are represented by the carcharodontosaurid Concavenator and the ornithomimosaur Pelecanimimus,^[11] as well as several taxa (Euronychodon, Paronychodon, and Richardoestesia) known from teeth; known avians are the enantiornitheans Concornis, Eoalulavis, and Iberomesornis.^[14] A single non-theropod dinosaur, the ornithischian Mantellisaurus, has been identified from Las Hoyas. Dinosaur footprints are also known from there.^[15] Crocodyliforms are represented by the gobiosuchid Cassissuchus, and trackways presumably left by goniopholidids.^[11] Lepidosaurs include Scandensia,^[16] and Jucaraseps.^[17] The exceptionally preserved eutriconodont mammal Spinolestes comes from Las Hoyas.^[18] An albanerpetontid amphibian, Celtedens, is known. Roughly twenty species of chondrichthyans (cartilaginous fishes), coelacanths, and actinopterygians (ray-finned fishes), including species previously thought to have lived exclusively in saltwater, constitute the known fish fauna of Las Hoyas.^[11][19] The invertebrate fauna of Las Hoyas is represented primarily by insects, and especially aquatic beetles.^[11]

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