Eurazhdarcho

''Eurazhdarcho'' is a genus of azhdarchid pterosaur that lived during the Maastrichtian age of the Late Cretaceous period in what is now Romania, about 69 million years ago. Starting in 2009, pterosaur fossil remains were unearthed in a layer of the Sebeș Formation in Lancrăm, southwestern Transylvania by paleontologist Mátyás Vremir. In 2013, he, along with paleontologists Alexander Kellner, Darren Naish, and Gareth Dyke would name the new genus and type species ''Eurazhdarcho langendorfensis''. Its generic name is a combination of Europe and the genus ''Azhdarcho'', while its specific name is in reference to its origin from Langendorf (the name of Lancrăm in the language of the German ethnic minority in Romania). The holotype specimen of ''Eurazhdarcho'' consists of a partial skeleton that includes cervical (neck) vertebrae, metacarpal, and phalanx fragments. The related and much larger azhdarchid ''Hatzegopteryx'' has also been found in the same location, indicating a possibility that ''Eurazhdarcho'' may have a juvenile of this pterosaur. However, the describers deemed this unlikely as its fossils seem to represent an adult specimen.

With extrapolations from the comparisons of cervical vertebrae and wingbones of ''Eurazhdarcho'' with those of the related azhdarchid '' Zhejiangopterus'' from China, Vremir and colleagues would estimate a wingspan not surpassing . This makes ''Eurazhdarcho'' a medium size member of its family, Azhdarchidae. The distinctive traits that the describers set for ''Eurazhdarcho'' are all found in its cervical vertebrae. Within Azhdarchidae, the position of ''Eurazhdarcho'' has been somewhat disputed, with some studies recovering it within the subfamily Quetzalcoatlinae, while others have found it in a basal (primitive) position within the family. Due to the abundance of terrestrial fauna in the Sebeș Formation, it has been suggested that ''Eurazhdarcho'' most likely fed by snatching small terrestrial prey while walking on all fours instead of being a fish-eater on the coast.

Discovery and naming

In 2009, Romanian paleontologist Mátyás Vremir uncovered the remains of a pterosaur at the SbG-B site of the Sebeș Formation in Lancrăm, near Sebeș-Glod in southwestern Transylvania, Romania. He donated these to the ''Erdélyi Múzeum'' of the '' Societății Muzeului Ardelean'' (Transylvanian Museum Society). Subsequent excavations by Vremir discovered additional bones of the same individual animal and were added by him to the collection of the Babeș-Bolyai University.

In 2013, Vremir, along with paleontologists Alexander Kellner, Darren Naish, and Gareth Dyke named and described a new genus and type species, ''Eurazhdarcho langendorfensis''. The generic name ''Eurazhdarcho'' combines the name of Europe with that of the related pterosaur ''Azhdarcho''. The specific name ''langendorfensis'' refers to its provenance from Langendorf, which is the name of Lancrăm in the language of the German ethnic minority in Romania. The article appeared in the electronic journal '' PLoS ONE'' without an accompanying printed version; it nevertheless validly names the taxon under the new rules of the ICZN.

The holotype specimen, EME VP 312, was found in a layer of the Sebeș Formation dating from the upper Early Maastrichtian, about 69 million years old. It consists of a partial skeleton lacking the skull. It includes three cervical (neck) vertebrae among which the almost complete third and the fourth; the third and fourth right metacarpal; the upper part of the first phalanx of the wing finger; the lower part of the second phalanx; a lower phalanx of one of the other fingers and a number of undetermined fragments. The Babeș-Bolyai University material is included within this enumeration and is not indicated by a separate inventory number. Generally, the quality of the bones is poor, with much of the outer cortex broken or eroded and internal structures present as impressions of natural molds. The fossils have not been completely flattened, preserving three-dimensionality, but compression has caused some distortion. The carcass had probably by flooding been deposed on its back in mud near a riverbank. Afterwards it was exposed to the air, weathering and being scavenged as proven by circular bite-marks inflicted by the conical teeth of some member of the Crocodyliformes. Later covered by a thin layer of dirt, it was damaged by beetles and termites.

The describers of ''Eurazhdarcho'' noted that the related giant pterosaur ''Hatzegopteryx'' is known from the same Romanian layers; the known fossil material from both genera does not overlap. Vremir and colleagues considered a juvenile identity for ''Eurazhdarcho'' with respect to ''Hatzegopteryx'' to be unlikely because the much smaller EME VP 312 seems to represent an adult individual.

Description

''Eurazhdarcho'' is a medium-sized member of Azhdarchidae, the family to which it belongs. Comparing the cervical vertebrae and wingbones of the largest adult and most complete specimen of '' Zhejiangopterus'', Vremir and colleagues noted that the length of the fourth cervical is roughly the same as in specimen EME VP 312 of ''Eurazhdarcho'', while the estimated length of the fourth metacarpal is substantially less, in ''Eurazhdarcho'' versus in ''Zhejiangopterus''. Extrapolating from this data, Vremir and colleagues estimated the wingspan of ''Eurazhdarcho'' at no more than .

Vremir and colleagues established some distinctive traits for ''Eurazhdarcho'', all present in the cervical vertebrae. The third neck vertebra has three-quarters of the length of the fourth vertebra, whereas 60 percent would be normal with azhdarchids. The necks of the prezygapophyses, the front joint processes, are well-developed and elongated, obliquely pointing forwards and outwards under an angle of 30 degrees with the long axis of the vertebra. The preexapophysis, a secondary joint process on the side of the prezygapophysis, is well-developed with a forward pointing articulation facet and separated from a process, itself the remains of the diapophysis and possibly a neck rib, on the outer base of the prezygapophysis, by a deep trough on its underside. The pneumatic openings, the entrance holes for the air sacks, at the sides of the neural arch are small and placed in a low position.

Classification

In its description, ''Eurazhdarcho'' was assigned to the family Azhdarchidae, based on the method of comparative anatomy. However, a cladistic analysis was not performed. In his 2021 study of ''Quetzalcoatlus'', American paleontologist Brian Andres included ''Eurazhdarcho'' in his phylogenetic analysis. He placed ''Eurazhdarcho'' in the subfamily Quetzalcoatlinae within Azhdarchidae. His analysis is shown in the first cladogram below. In 2023, paleontologist Rodrigo Pêgas and colleagues recovered ''Eurazhdarcho'' in a different position within Azhdarchidae. They found it forming a clade with azhdarchids ''Phosphatodraco'', '' Wellnhopterus'', and '' Aralazhdarcho'' in a basal (primitive) position within the family. This classification model would be followed by a few subsequent studies. Their phylogenetic analysis is shown in the second cladogram below.

Topology 1: Andres (2021).

Topology 2: Pêgas and colleagues (2023).

Paleobiology

The area where ''Eurazhdarcho'' was found, in the Upper Cretaceous was localized on the Hațeg Island, part of the prehistoric European archipelago in the ancient Tethys Sea. The SbG-B site, though encompassing a surface of just , has yielded several distinct animal species, among which are the turtle '' Kallokibotion bajazidi'', the hadrosaur ''Telmatosaurus'' and the titanosaur ''Magyarosaurus''. This terrestrial fauna suggests that ''Eurazdarcho'' was not a coastal piscivore catching fish on the wing, affirming the "superstork" model for azhdarchids, in which they are terrestrial stalkers snatching small prey animals while walking on all fours.

If ''Eurazhdarcho'' was indeed distinct from ''Hatzegopteryx'', its discovery implies the presence of two azhdarchid forms in the Hațeg fauna, the one gigantic, the other medium-sized. This suggests a niche partitioning between them, although it is as yet unclear how this correlates with differences in prey preference and hunting techniques. This reflects a pattern seen in other Late Cretaceous faunae which also show a combination of a large azhdarchid species with a smaller one. One such example is the Javelina Formation from the Maastrichtian of Texas, which has brought forth the giant ''Quetzalcoatlus northropi'', but also smaller taxa such as ''Quetzalcoatlus lawsoni'' and '' Wellnhopterus brevirostris''.

See also

* List of pterosaur genera
* Timeline of pterosaur research

References

{{Portal bar, Paleontology, Romania

Azhdarchidae
Maastrichtian life
Late Cretaceous pterosaurs of Europe
Cretaceous Romania
Fossils of Romania
Hațeg fauna
Fossil taxa described in 2013