Ubirajara jubatus

"Ubirajara" ("lord of the spear") is an informal genus of compsognathid theropod that lived during the early Cretaceous period in what is now Brazil. The manuscript describing it was available online pre-publication but was never formally published and, as a consequence, both genus and species name are considered invalid and unavailable.^[1] It is known by a single species, "Ubirajara jubatus", recovered from the Crato Formation. It was described as the first Gondwanan non-avian theropod dinosaur discovered with preserved integumentary structures. Such proto-feathers, most likely used for display, include slender monofilaments associated with the base of the neck, increasing in length along the dorsal thoracic region, where they would form a mane, as well as a pair of elongate, ribbon-like structures likely emerging from its shoulders.^[2] The taxon was informally named in 2020 in a now-withdrawn in-press academic paper. The description caused controversy due to the fossil having been apparently illegally smuggled from Brazil. In June 2023, Germany returned the fossil to Brazil after a legitimate export permit could not be found.^[3] The name "Ubirajara jubatus" was removed from ZooBank in November 2022, which means it no longer has any nomenclatural significance.^[1] The case has been labeled as an instance of scientific colonialism.^[4][5][6][7]

Workers recovered a number of fossils from a chalk quarry located between Nova Olinda and Santana do Cariri. One of the recovered pieces was a chalk plate that had already been split by the workers. Further preparation by a sharp steel pin and X-ray photography revealed the presence of a small theropod skeleton. The specimen, SMNK PAL 29241, was discovered in a layer of the Crato Formation, dating from the Aptian, about 115 million years old. It consists of a partial skeleton lacking the skull, preserved on a slab and counterslab. It consists of nine neck vertebrae, thirteen back vertebrae, two sacral vertebrae, the shoulder girdle, one neck rib, seven dorsal ribs, fifteen belly ribs and the almost complete left arm. Apart from the bones, the fossil also preserves remains of the plumage, skin, granulate structures in the torso, and the keratin sheaths of the hand claws. The skeleton is partially articulated. It represents a juvenile, and possibly male, individual.^{[8][failed verification]}

The authors of the 2020 study claimed that the fossil had been acquired by the State Museum of Natural History Karlsruhe (SMNK) in 1995, following an export from Brazil with the necessary documentation.^{[8][failed verification]} This lead to a considerable backlash as researchers from Brazil disputed this claim.^[9] They argued that Brazilian law does not allow the removal of fossils from its territory, nor for studies on them to be conducted without the participation of local scientists or institutions.^[10][11] As a result, Brazilian scientists campaigned for the repatriation of the fossil.^[12] This campaign relied heavily on social media and mobilised a large number of supporters under the hashtag #UbirajaraBelongstoBR.^[13]

Due to the ethical issues involving the potentially illegal transfer of the fossil from Brazil to Germany, the paper describing the specimen was "temporarily removed" only a few days after being made available online "in press" prior to formal publication.^[9][14] The article was later withdrawn in September 2021.^[15]

These events prompted an investigation into the provenance of the specimen. In 2021, a spokesperson for the Ministry of Science, Research and Culture of Baden-Württemberg confirmed that the fossil had, in fact, been removed from Brazil in 2006 and acquired by the SMNK in 2009.^[15] The investigation also failed to retrieve legitimate permits for the export of the specimens from Brazil.^[16] A legal analysis, published in the International Journal of Cultural Property, later confirmed the doubts concerning the legality of the specimen, concluding that the Brazilian state was the legal owner of the specimen, that the SMNK had not acquired good title to it, and that as a result, Brazil would be entitled to a civil action of restitution pursuant to Article 985 of the German Civil Code.^[17]

Accordingly, State Minister for Science, Research and Culture Theresia Bauer made an announcement in July 2022 that the fossil of "Ubirajara jubatus" would be returned to Brazil.^[18] During a ceremony on 12 June 2023, the specimen was officially repatriated by a German delegation headed by German Foreign Minister Annalena Baerbock.^[3][19] It is now on display at the Plácido Cidade Nuvens Paleontology Museum which is associated with the Regional University of Cariri (Urca).^[20]

The genus name "Ubirajara" was erected by Robert S. H. Smyth, David Michael Martill, Eberhard Frey, Hector Eduardo Rivera-Silva and Norbert Lenz in December 2020.^{[8][failed verification]} The generic name means "Lord of the Spear" in the local Tupi language, in reference to the elongate shoulder filaments. The informal specific name, "jubatus", means "maned" in Latin, referring to the preserved integument on its back.^[21]

The "temporary removal" and ultimately the retraction of the publication describing the new genus and species, however, raise questions as to the nomenclatural validity of the new taxon.^[15] On 18 November 2022, the records of the names "Ubirajara jubatus", as well as their publication records, were removed from ZooBank, and a 2023 review noted that "Ubirajara jubatus" is an unavailable name with no nomenclatural significance, but not specifically a nomen nudum.^[1] The authors of the review note also noted that the phylogenetic matrix containing the specimen has never been made available, raising doubts about the claimed affinities of the specimens.^[1]

In life, the fossil individual would have been approximately 1 metre (3.3 ft) long.^[21]

The describing authors established a unique combination of two traits that in themselves were not unique. The shoulder blade has 81% of the length of the humerus instead of being equally long or much longer, the two prevailing conditions with other compsognathids. The top profiles of the neural spines of the sacral vertebrae are 15% to 27% longer than their bases are long in side view, instead of being much longer as with Mirischia.^{[8][failed verification]}

The granulated structures in the torso were concluded to have been adipocere, corpse wax. They do not show food remains and are therefore unlikely to represent intestines. Also they lack a scale structure. The specimen preserves a "mane" of proto-feathers that ran along its neck and back. Also they covered the arm including the hand up to the claws. This SMF (slender monofilamentous integument) became longer towards the rear, reaching a length of eleven centimetres over the ninth and tenth back vertebrae. These filaments were not branched and had a diameter of about 0.3 millimetre with a hollow core. Skin remains contain a series of nineteen rectangular vertical structures that were interpreted as the follicles of the filaments. Skin muscles would have allowed to erect a mane over the back. Their shrinking in the saline lagoon conditions of the Crato Formation would have caused the mane to have been activated after death, as still shown by the fossil.^{[8][failed verification]}

Unique, 15-centimetre (5.9 in) integumentary structures projected from its sides. The left side shows a pair of flat straight elongated spikes. A similar pair was assumed to have been present on the opposite right side. The upper spike is fifteen centimetres long, the lower one fourteen centimetres. The structures are reinforced by a central sharp longitudinal ridge, 0.1 millimetre wide. Total width is 4.5 millimetres for the upper spike, 2.5 millimetres for the lower with parallel sides which only taper close to the distal end. There is no sign of any ossification. The authors compared this Broad Monofilamentous Integument to those of the standardwing bird-of-paradise. The authors speculate that the ribbon-like shoulder structures might have had display purposes, perhaps being erected in a courtship display. It was also deemed possible that they vibrated and even made a noise. That such a display structure should be present in a juvenile is exceptional. This phenomenon is not known from modern Neornithes but has been reported in Enantiornithes and Zuolong.^{[8][failed verification]} The authors noted that in the more derived group of the Paraves, such structures are largely limited to the tail. They suggested this prevented the display structures to limit the aerodynamic capabilities of these volant species. The non-volant compsognathids would in this respect not be hindered by shoulder spikes. That simple filaments could evolve into complex display structures would be an indication that pennaceous feathers were not evolved for display reasons, contrary to what has been often assumed.^{[8][failed verification][22]}

The specimen was placed in the Compsognathidae family in 2020, as the sister species of a clade formed by Sinosauropteryx and Compsognathus.^[21] This phylogeny was criticized since it cannot be properly scientifically tested or replicated at the moment because the data supporting it were never made available.^[1]

Compsognathidae	Huaxiagnathus "Ubirajara" Compsognathus Sinosauropteryx

• List of informally named dinosaurs
• List of non-avian dinosaur species preserved with evidence of feathers