Your Friends The Titanosaurs: Yeneen houssayi

What do you get the formation that has five established titanosaur species and a couple of ne'er-do-wells? A sixth titanosaur, of course!

All joking aside, it's misleading to think of "Titanosauria" as a relatively small-scale group like Diplodocidae or Brachiosauridae when it's really a massive, sprawling complex including multiple distinct lineages that essentially monopolized all things sauropod in the Late Cretaceous. We talk of the Morrison Formation having diplodocids and dicraeosaurids and camarasaurids and brachiosaurids and whatever else, and that may sound more impressive than the Bajo de la Carpa Formation having six different titanosaurs. "What? You need all those titanosaurs?" "All those titanosaurs" are functionally replacing each of those smaller clades of the Morrison, as well as apparently just about everything else large and herbivorous. It's just the relationships and smaller divisions are still fuzzy. Eventually, we'll have a better grasp. But enough philosophy! Let's bring on today's guest, Yeneen houssayi. (And thank you to Alberta Claw and Stephen Poropat for supplying me with the paper!)

Genus and Species: Yeneen houssayi. "Yeneen" is a Tehuelche (Aónikenk) spirit or entity of winter, with a double meaning in this case because the type locality is in La Invernada, from the Spanish for winter pasture. The species name honors Dr. Bernardo Alberto Houssay, "Nobel Laureate in Medicine and member of the commission that promoted the creation of CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina)" (Filippi et al. 2026).

Citation: Filippi, L. S., F. Bellardini, J. l. Carballido, A. H. Méndez, and A. C. Garrido. 2026. Yeneen houssayi gen. et sp. nov. and an overview of the sauropod titanosaurian diversity from Cerro Overo – La Invernada area (Bajo de la Carpa Formation, Santonian), North Patagonia, Argentina. Historical Biology (advance online publication). doi: 10.1080/08912963.2025.2584707.

Geography and Stratigraphy: As mentioned, the type specimen comes from La Invernada, in northeastern Neuquén, Argentina, southwest of frequently mentioned Rincon de los Sauces. It was found in bedform deposits in a fluvial bar near the top of the Bajo de la Carpa Formation, of middle Late Cretaceous (Santonian) age (Filippi et al. 2026).

Holotype: MAU-Pv-LI-538/1–30 (Museo Municipal Argentino Urquiza, Rincón de los Sauces, Neuquén, Argentina). This specimen is primarily composed of vertebrae: six cervicals, ten dorsals, a sacrum of six fused vertebrae, and one anterior caudal. There are also a few partial to complete dorsal ribs and parts of both ilia (fused to the sacrum, naturally). The bones were found associated in an area about 5 m by 3 m (16 ft by 10 ft). The dorsals, sacrum, and caudal appear to make one sequence, but the cervicals have a couple of gaps (Filippi et al. 2026).

A smaller right ilium (MAU-Pv-LI-539) was found in the same rectangle and designated cf. Yeneen houssayi. A third titanosaur, MAU-Pv-LI-731, represented by axial and appendicular bones, was also found here (Filippi et al. 2026). It is not depicted on the quarry map, though, so it's not clear how it relates spatially to the other two. None of these are one of the La Invernada or Rincon de los Sauces titanosaurs discussed in this post. Dragging in recent abstracts and papers, they are also not MAU-Pv-CO-726 (CO=nearby Cerro Overo) and its partial tail with osteoderms, also from the Bajo de la Carpa Formation; or MAU-Pv-LI-733, 734, 735, et al., a collection of axial and appendicular bones representing multiple individuals of different growth stages from the Bajo de la Carpa of La Invernada (Filippi et al. 2025); or the braincases and endocasts from the Bajo de la Carpa of Cerro Overo-La Invernada (Paulina-Carabajal et al. 2024); or the miscellaneous specimens in Filippi et al. (2024) (same titanosaur-time, same titanosaur-channel). Doubtless at least some of these belong to named taxa (one of the braincases is Inawentu oslatus, for example), but gee, that's a lot of titanosaurs.

As the holotype makes clear, Y. houssayi is another example of a titanosaur with good axial material but not much else. In the Bajo de la Carpa Formation alone we also have Inawentu oslatus, Overosaurus paradasorum, and Traukutitan eocaudata going the same route. The other two established names, Bonitasaura salgadoi and Rinconsaurus caudamirus, also include quite a few vertebrae, so we have decent overlap. T. eocaudata, being caudals, is the only one where the overlap leaves something to be desired, but fortunately it's pretty distinctive as a basal titanosaur. Y. houssayi is interpreted as closest to the similarly smallish O. paradasorum (found near but outside the aeolosaurs), then R. caudamirus (unsurprisingly, a rinconsaur). I. oslatus and B. salgadoi are off on the other side of Titanosauria (Filippi et al. 2026).

One feature of Filippi et al. (2026) you may find convenient is the use of numbered red circles in the figures to point out diagnostic characteristics. They cite seven for their new species; as is typical with sauropod vertebrae the features are mostly details of vertebral laminae and such with twenty-letter names, so having the indicators makes them much easier to visualize. (Also, with the lavish description, running to nearly 40 pages with multiple images of each bone, having such cues is useful for keeping on track as a reader!)

References

Filippi, L. S., F. Bellardini, A. Paulina-Carabajal, P. Cruzado-Caballero, J. González-Dionis, A. H. Méndez, F. Gianechini, K. Ulloa-Guaiquin, A. Garrido, I. Maniel, Y-N. Lee, and K. Do-Kwon. 2023. Articulated osteoderms on a titanosaur tail from Cerro Overo–La Invernada (Bajo de la Carpa Formation), Upper Cretaceous, Northern Patagonia, Argentina: Paleobiological and paleoecological implications. Reunión de Comunicaciones de la Asociación Paleontológica Argentina 2023. Publicación Electrónica de la Asociación Paleontológica Argentina 24(R3): R67–R68.

Filippi, L. S., F. Bellardini, J. L. Carballido, A. Pérez-Moreno, and A. C. Garrido. 2024. Sauropod diversity (Dinosauria: Sauropoda) of Cerro Overo – La Invernada (Bajo de la Carpa Formation, Santonian), northeastern Neuquén Basin, and paleoecological implications for Upper Cretaceous sauropod faunas. Publicación Electrónica de la Asociación Paleontológica Argentina 24(1): 71–96.

Filippi, L. S., F. Bellardini, F. Barrios, A. Paulina-Carabajal, F. A. Gianechini, G. Martínez Palacio, K. Ulloa-Guaiquin, C. Rodríguez Canalis, A. C. Garrido, I. J. Maniel, J. E. Guevara Lucero, A. H. Méndez, Y. N. Lee, K. D. Kwon, and S. Lee. 2025. An exceptional sauropod titanosaur site with multiple ontogenetic stages, from Cerro Overo-La Invernada area (Bajo de la Carpa Formation, Santonian) from North Patagonia. Reunión de Comunicaciones de la Asociación Paleontológica Argentina 2024. Publicación Electrónica de la Asociación Paleontológica Argentina 25(R1): R81–R82.

Filippi, L. S., F. Bellardini, J. l. Carballido, A. H. Méndez, and A. C. Garrido. 2026. Yeneen houssayi gen. et sp. nov. and an overview of the sauropod titanosaurian diversity from Cerro Overo – La Invernada area (Bajo de la Carpa Formation, Santonian), North Patagonia, Argentina. Historical Biology (advance online publication). doi: 10.1080/08912963.2025.2584707.

Paulina-Carabajal, A., K. Ulloa-Guaiquin, F. Barrios, I. Maniel, A. H. Méndez, L. Filippi, F. Gianechini, J. Dionis, Y.-N. Lee, D. Kim, S. Lee, and A. Garrido. 2024. An extraordinary site for the findings of natural endocasts in Patagonia and its implications for dinosaur paleoneurology. 2024 XXXVII Jornadas Argentinas de Paleontología de Vertebrados. Publicación Electrónica de la Asociación Paleontológica Argentina 24(R4): R16.