Your Friends The Titanosaurs: Ibirania parva

It's been more than half a year since our last friendly titanosaur (Abditosaurus kuehnei), but September has brought us a new saltasaur. To be precise, our guest is Ibirania parva, hailing from the late Late Cretaceous of the Bauru Basin of southern Brazil. There is always room here for a sauropod that could have been transported in a standard shipping container,* so let's begin.

*Or, heck with that, in an Amazon van—curl the neck and/or tail and 5.7 meters/19 feet of sauropod can be yours with free shipping for Amazon Prime members. Or get a horse trailer and make allowance for your curious sauropod to poke its head out the sides.

Genus and Species: Ibirania parva. The genus name combines "Ibirá", the name of the municipality where the fossils were discovered, with a modification of the Greek "plania" for "wander". Ibirá itself is derived from a Tupi word ("ybyrá") meaning "tree" or "wood". The species name "parva" is the feminine form of the Latin "parvus" meaning "small" or "little" (Navarro et al. 2022). Together we get something akin to "little tree wanderer", if you want to call attention to a browsing habit, or "little Ibirá wanderer" if you want to recognize the municipality; it's a neat double meaning.

Citation: Navarro, B. A., A. M. Ghilardi, T. Aureliano, V. Díez Díaz, K. L. N. Bandeira, A. G. S. Cattaruzzi, F. V. Iori, A. M. Martine, A. B. Carvalho, L. E. Anelli, M. A. Fernandes, and H. Zaher. 2022. A new nanoid titanosaur (Dinosauria: Sauropoda) from the Upper Cretaceous of Brazil. Ameghiniana 59(5):317–354. doi:10.5710/AMGH.25.08.2022.3477 [which always gives me a 403 error, but maybe it won't for you].

Stratigraphy and Geography: The type specimen was collected from a massive conglomeratic sandstone of the São José do Rio Preto Formation, dating to the late Santonian–early Campanian of the Late Cretaceous (Navarro et al. 2022). Unlike most South American Upper Cretaceous formations, only one other titanosaur has been named from this formation, the ever-popular "Antarctosaurus" brasiliensis. The outcrop was on the "Sítio dos Irmãos Garcia (Garcia Brothers Farm), near the Washington Luis State Highway (SP-310) in Vila Ventura [District], Ibirá Municipality, northeastern São Paulo State, Brazil" (Navarro et al. 2022). Referred specimens come from similar stratigraphic horizons in the district (Navarro et al. 2022). The authors describe the depositional setting as a braided fluvial floodplain under a strongly seasonal and generally arid climate.

Holotype: The type specimen of I. parva is a group of bones found associated but disarticulated. They include a posterior dorsal, a couple of partial caudals, a partial caudal neural arch, a fragmentary radius and ulna, the distal half of a metacarpal, and a metatarsal, catalogued in the series LPP-PV-0200 to 0207 (Laboratório de Paleoecologia e Paleoicnologia of the Departamento de Ecologia e Biologia Evolutiva, Universidade Federal de São Carlos, São Carlos) (Navarro et al. 2022).

In addition to the holotype, the authors referred other specimens to the new species, including parts of two cervicals, parts of four dorsals, another caudal, a partial fibula, and a nearly complete fibula (Navarro et al. 2022). (In other words, like most titanosaurs I. parva is known from partial remains mostly belonging to the vertebral column.) Weathering was unkind to many of the elements (Navarro et al. 2022). The remains are skeletally mature and represent animals around 5.7 m (19 ft) long (Navarro et al. 2022), which is pretty darn small even for a saltasaur. Aside from its unusually diminutive dimensions, I. parva is a typical saltasaur, a small stocky well-pneumatized sauropod. The only thing missing for the complete saltasaur experience is osteoderms, and their absence is hardly surprising with much of the rest of the skeleton absent as well. Within the saltasaurs, I. parva was found to be closest to a clade made up of Bonatitan reigi and Rocasaurus muniozi (Navarro et al. 2022). (For those of you who are fans of the idea that Alamosaurus sanjuanensis includes more than one species, note that the phylogeny also has the neck BIBE 45854 hanging out with the lognkosaurs while the rest of Alamosaurus is paired with Baurutitan just outside of Saltasaurinae.)

The authors also drew attention to "nanoid" titanosaurs in their phylogeny, which are widely distributed phylogenetically (of course, longtime readers might have drawn that conclusion already). Titanosaurs seem to have had a knack for evolving small-bodied forms. Temporally the nanoids are Santonian–Maastrichtian, and geographically they are European or South American, with a couple of European lineages and perhaps a couple of South American lineages (saltasaurs and aeolosaurs/aeolosaur-adjacent titanosaurs). Interestingly, the Bauru Basin is a good place to find downsized titanosaurs. Unlike some of the other cases, there is no evidence that I. parva was small due to living on a small landmass. Instead, the authors suggest it was small as a response to aridity (Navarro et al. 2022).

References

Navarro, B. A., A. M. Ghilardi, T. Aureliano, V. Díez Díaz, K. L. N. Bandeira, A. G. S. Cattaruzzi, F. V. Iori, A. M. Martine, A. B. Carvalho, L. E. Anelli, M. A. Fernandes, and H. Zaher. 2022. A new nanoid titanosaur (Dinosauria: Sauropoda) from the Upper Cretaceous of Brazil. Ameghiniana 59(5):317–354. doi:10.5710/AMGH.25.08.2022.3477 [which always gives me a 403 error, but maybe it won't for you].