| Elopteryx | |
|---|---|
 | |
| Theholotype femur fragment in several views | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Clade: | Paraves |
| Genus: | †Elopteryx Andrews, 1913 |
| Type species | |
| †Elopteryx nopcsai Andrews, 1913 | |
| Synonyms | |
| |
Elopteryx is agenus ofparaviantheropoddinosaur based on fragmentaryfossils found inLate Cretaceous rocks ofRomania. The singlespecies,Elopteryx nopcsai, was known only from very incomplete material until new specimens were reported in the 21st century.Balaur bondoc might represent ajunior synonym of this taxon.[1][2]
In the late nineteenth or early twentieth century, the famousHungarianpaleontologistFranz Nopcsa von Felső-Szilvás found nearSînpetru, in what is now the Romanian region ofTransylvania, some bone fragments of a small theropod. These were acquired by theBritish Museum of Natural History. In 1913, curatorCharles William Andrews named these as thetype speciesElopteryx nopcsai. The genus nameElopteryx is fromAncient Greekhelos (ἕλος), "marsh" +pteryx (πτέρυξ), "wing". Thespecific name honors Nopcsa. Initially,Elopteryx was described from itsholotype, aproximal leftfemur, specimenBMNH A1234. A second upper left thighbone fragment, BMNH A1235, was referred. Adistal lefttibiotarsus was also tentatively assigned to thistaxon; it was initially classified with the same specimen number as the holotype and was found in close proximity, but may not be from the same individual (see below). This has since been relabeled and is now specimen BMNH A4359. The exact location and time of the discoveries are today unknown. The fossils date from the early-lateMaastrichtian (Begudian)faunal stage, circa 70-66million years ago, originating from theSânpetru Formation of theHațeg Island. The animal was by Andrews believed to be apelecaniformseabird.[3][4]
In 1929 the Hungarian paleontologistKálmán Lambrecht referred two more specimens: BMNH A PAL.1528 and BMNH A PAL.1588, respectively a left and a right tibiotarsus.[5] In 1933 Lambrecht named a separate family Elopterygidae.[6]The supposed family Elopterygidae was initially placed in thesuborderSulae – then still in thepolyphyletic "Pelecaniformes" – in 1963 byPierce Brodkorb in his fossil bird catalogue, and theCenozoic generaArgillornis andEostega were moved to it.[7] These two are unequivocal derivedneornith birds and the latter indeed seems to be an ancientsulid, whereasArgillornis has turned out to be referrable to the giantpseudotooth birdDasornis which was almost certainly not very closely related to the Sulae.[8] Reconstruction attempts ofE. nopcsai likethis are based on this presumed affiliation withgannets andcormorants. But more recent studies would result in radically different interpretations.
In 1975, the distal tibiotarsi BMNH A1588 and BMNH A1528, together with BMNH A4359, were byColin James Oliver Harrison andCyril Alexander Walker removed fromElopteryx, redescribed asBradycneme draculae andHeptasteornis andrewsi respectively, and used to establish a supposed family of gigantic two metre tallowls, theBradycnemidae.[3] In 1978 Brodkorb had changed his opinion after the supposedElopteryx material was divided among three species in total, and was actually the first scholar in modern times to suggest that theseMesozoic bones were not of birds but of non-avian dinosaurs.[9]
In 1981,Dan Grigorescu andEugen Kessler stated thatElopteryx was a non-aviancoelurosaurian dinosaur. They also referred a supposed distal femur (FGGUB R.351) toElopteryx,[10] but both researchers (with Zoltan Csiki) later identified this specimen as ahadrosauroid distalmetatarsal.[11]
In 1992, it was proposed byJean Le Loeuff e.a. thatBradycneme andHeptasteornis should besynonymized withE. nopcsai again, and a femur (MDE-D203), ananteriordorsalvertebra (MDE-D01), aposteriorsacral vertebra (MDE collection, unnumbered) and some dorsalrib fragments from theJurassicGrès à Reptiles formation of France were described as an indeterminate species ofElopteryx; that study placed all this material in theDromaeosauridae or a family orsubfamily (Elopteryginae) very close to these.[12] The vertebrae were in 1998 separated again and assigned to a new dromaeosaurid,Variraptor mechinorum.[13] The French femur is similar in general appearance to theElopteryx type but it differs in diagnostic traits, e.g. lacking a fourth trochanter. Also, neither the ribs nor the tibiotarsi can be compared to thetype specimen ofElopteryx, there being no overlapping material.
In 2005, another (distal) femur piece, FGGUB R.1957, has been described as a new specimen ofElopteryx on the basis of the bone texture.[11] In 2019, a potential pelvis specimen identified as cf.E. nopcsai was reported.[14] In 2024, a new femur specimen fromRomania was attributed toElopteryx, and the specimen shows that it was secondarily flightless.[2]
Modern interpretations have differed on the question whether theBradycneme andHeptasteornis material should be included — they have meanwhile been synonymized and split from each other andElopteryx many times — and what the exact affiliations of the material would be. Various solutions were proposed for this problem.[15] Previously, some researchers proposedElopteryx was a member of theDromaeosauridae orTroodontidae,[16] without being able to support this with much empirical evidence.[11] In 1998 Csiki & Grigorescu suggested thatElopteryx belonged to theManiraptora, whileBradycneme had a more basal position in theTetanurae.[17]
Since the 21st century,Elopteryx has been supported widely as a member of theManiraptora, with most studies recovering it as a member of theParaves. In 2004,Darren Naish andGareth Dyke consideredElopteryx as aEumaniraptoraincertae sedis, possibly either a non-ornithuromorphanpygostylian bird[18] or atroodontid, whileBradycneme would be a maniraptoran, and thedubiousHeptasteornis (at least its holotype BMNH A4359) a member of theAlvarezsauridae.[19] ThusE. nopcsai seems to be some sort of birdlike eumaniraptoran, but not related to modern birds. In 2005, Kessler, Grigorescu and Csiki reunited all the material inElopteryx but considered it an alvarezsaurid.[11] In a 2011 classification, Tom Holtz assignedElopteryx to theTroodontidae.[20] In 2013,Stephen L. Brusatte and colleagues mentioned a possibility ofElopteryx and theparavianBalaur bondoc being the same taxon, though the authors did not consider it the most likely case.[1] Later, in 2019, two studies have found it to be anavialan once again, but a basal one; Hartman and colleagues recover it as a confuciusornithiform[21] while Mayr and colleagues note similarities withGargantuavis andBalaur, suggesting they form a clade native to the Late Cretaceous European archipelago.[14] Mayr and colleagues also claimed that the synonymy ofElopteryx andBalaur remains possible and that more work is needed for confirmation.[14] In 2024, Stoicescu and colleagues suggested thatElopteryx is indeed aparavian and a member of theAvialae based on its new specimen, and thatBalaur bondoc is probably ajunior synonym ofElopteryx.[2]
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