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Inawentu; Temporal range: Late Cretaceous, Santonian PreꞒ Ꞓ O S D C P T J K Pg N ↓
	Reconstructed skeleton
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	Saurischia
Clade:	†Sauropodomorpha
Clade:	†Sauropoda
Clade:	†Macronaria
Clade:	†Titanosauria
Clade:	†Eutitanosauria
Genus:	†Inawentu; Filippi et al., 2024
Species:	†I. oslatus
Binomial name
	†Inawentu oslatus; Filippi et al., 2024

Inawentu (meaning "imitator") is an extinct genus of titanosaurian sauropod dinosaur from the Late Cretaceous Bajo de la Carpa Formation of Argentina. The genus contains a single species, I. oslatus, known from a partial articulated skeleton including the skull. The square-shaped jaw of Inawentu demonstrates convergent characteristics with rebbachisaurids.^[1]

Discovery and naming

The Inawentu holotype specimen, MAU-Pv-LI-595, was discovered in sediments of the Bajo de la Carpa Formation (Neuquén Group) near Rincón de los Sauces in Neuquén Province, Argentina. The specimen consists of a partial articulated skeleton, including a nearly complete skull, all of the vertebrae from the atlas to the end of the sacrum (comprising twelve cervical, ten dorsal, and six sacral vertebrae), and both ilia.^[1] MAU-Pv-LI-595 is one of the few known titanosaur specimens to preserve a complete neck.^[2]

In 2016, the find was presented at a conference in Argentina.^[3]^[2] In 2023, Filippi et al. announced Inawentu oslatus as a new genus and species of titanosaurian sauropod based on these fossil remains in a non-final preprint. The description was finalized the following year. The generic name, "Inawentu", is derived from a Mapundungun word meaning "mimic" or "imitator". The specific name, "oslatus", combines the Latin words "os", meaning "mouth" and "latus", meaning "broad".^[1]

Description

The skull of Inawentu showed several convergent similarities to rebbachisaurids such as Nigersaurus, such as a wide, squared-off snout that was deflected strongly downward. The neck of Inawentu consisted of only twelve vertebrae, fewer than in any other known titanosaur.^[1] MCT 1487-R, a specimen possibly referable to Uberabatitan,^[4] has thirteen, Futalognkosaurus has fourteen, and Rapetosaurus has seventeen. Thus, Inawentu may have had a proportionately shorter neck than most titanosaurs. The centra and neural arches of the neck and back vertebrae are highly modified, which suggests that the neck would have been capable of multidirectional movement. As in most titanosaurs, there were ten dorsal and six sacral vertebrae. The hips were narrower than in Saltasaurus and Neuquensaurus.^[1]

Classification

Filippi et al. (2024) recovered Inawentu as a member of a previously unrecognized clade of square-jawed eutitanosaurs, which they referred to as "Clade A", as the sister taxon to Antarctosaurus. Their results differ from many previous studies, which usually found a close relationship between lognkosaurs and rinconsaurs, but similar results had been previously found by Gorscak and O'Connor in 2016.^[1]^[5] The results of their phylogenetic analyses are shown in the cladogram below:^[1]

	Notocolossus

	Lognkosauria

Lithostrotia

"Clade A"

Baalsaurus

Bonitasaura

	Inawentu

	Antarctosaurus

Narambuenatitan

	Uberabatitan

	Brasilotitan

	Rinconsauria

	Aeolosaurini

Paleoecology

The Bajo de la Carpa Formation, where Inawentu was found, preserves an ecosystem including other titanosaurs, including other members of "Clade A": Bonitasaura, Rinconsaurus, and Overosaurus.^[6]

References

^ ^a ^b ^c ^d ^e ^f ^g Filippi, Leonardo S.; Juárez Valieri, Rubén D.; Gallina, Pablo A.; Méndez, Ariel H.; Gianechini, Federico A.; Garrido, Alberto C. (February 2024). "A rebbachisaurid-mimicking titanosaur and evidence of a Late Cretaceous faunal disturbance event in South-West Gondwana". Cretaceous Research. 154. doi:10.1016/j.cretres.2023.105754. ISSN 0195-6671.
^ ^a ^b Taylor, Michael P. (2022-01-24). "Almost all known sauropod necks are incomplete and distorted". PeerJ. 10: e12810. doi:10.7717/peerj.12810. ISSN 2167-8359. PMC 8793732. PMID 35127288.
^ Filippi, L. S.; Juárez Valieri, R. D.; Gallina, P. A.; Méndez, A. H.; Gianechini, F. A.; Garrido, A. C. (2016), "A new titanosaur specimen with highly derived skull from the Santonian of northern Patagonia, Argentina", 11 Congreso de la Asociación Paleontológica Argentina.
^ Silva Junior, Julian C. G.; Marinho, Thiago S.; Martinelli, Agustín G.; Langer, Max C. (2019-04-08). "Osteology and systematics of Uberabatitan ribeiroi (Dinosauria; Sauropoda): a Late Cretaceous titanosaur from Minas Gerais, Brazil". Zootaxa. 4577 (3): 401. doi:10.11646/zootaxa.4577.3.1. eISSN 1175-5334. ISSN 1175-5326. PMID 31715707. Retrieved 2021-02-13.
^ Gorscak, Eric; O‘Connor, Patrick M. (2016-04-30). "Time-calibrated models support congruency between Cretaceous continental rifting and titanosaurian evolutionary history". Biology Letters. 12 (4): 20151047. doi:10.1098/rsbl.2015.1047. ISSN 1744-9561. PMC 4881341. PMID 27048465.
^ Gallina, Pablo A.; González Riga, Bernardo J.; Ortiz David, Leonardo D. (2022). "Time for Giants: Titanosaurs from the Berriasian–Santonian Age". South American Sauropodomorph Dinosaurs. Cham: Springer International Publishing. pp. 299–340. ISBN 978-3-030-95958-6.