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.

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.

[1] Workers recovered a number of fossils from a chalk quarry located between Nova Olinda and Santana do Cariri.

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.

[3][failed verification] 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.

[3][failed verification] The generic name means "Lord of the Spear" in the local Tupi language, in reference to the elongate shoulder filaments.

[1] The fossil was acquired in 1995 by the State Museum of Natural History Karlsruhe (SMNK) and moved to Germany after an export permit was allegedly obtained.

[9] 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.

[12][13][14][15] In July 2022, following an extensive social media campaign, the SMNK agreed to return the specimen to Brazil after their investigation failed to find legitimate export permits.

This SMF (slender monofilamentous integument) became longer towards the rear, reaching a length of eleven centimetres over the ninth and tenth back vertebrae.

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.

[3][failed verification][19] The specimen was placed in the Compsognathidae family in 2020, as the sister species of a clade formed by Sinosauropteryx and Compsognathus.