2024 has been productive for titanosaurs. Not counting other titano-centric publications, there have already been (potentially) three new genera and species. For number 3, we head back to the familiar land of Patagonia in Argentina, although in this case our new guest represents an Upper Cretaceous formation with no previous named titanosaurs (which seems like a real oddity these days). Titanomachya gimenezi is also decidedly non-titanic for a titanosaur, hanging out down in the saltasaur neighborhood.
Genus and Species: Titanomachya gimenezi. The genus name is derived from the Titanomachy, which in Greek mythology was a war in which the older gods (the Titans) were defeated by the younger gods (the Olympians). The usage here alludes to the dinosaur dating to near the end of the time of titanosaurs. "Gimenezi" refers to "the late Dr. Olga Giménez, who was the first female palaeontologist that studied the dinosaurs from Chubut Province" (Pérez-Moreno et al. 2024).
Citation: Pérez-Moreno, A., L. Salgado, J. L. Carballido, A. Otero, and D. Pol. 2024. A new titanosaur from the La Colonia Formation (Campanian-Maastrichtian), Chubut Province, Argentina. Historical Biology (advance online publication). doi: https://doi.org/10.1080/08912963.2024.2332997.
Geography and Stratigraphy: The type and only known specimen of T. gimenezi was discovered in the Cerro Bayo area, about 10 km (6 mi) southwest of Bajado del Diablo in Chubut Province, Argentina (Pérez-Moreno et al. 2024). The rocks pertain to the La Colonia Formation, which you may otherwise recognize as the formation that produced Carnotaurus (and which started out dated around the middle of the Cretaceous but now is known to date later). This formation is composed of sandstone, siltstone, and claystone deposited in coastal settings (e.g., estuarine, tidal flat, coastal plain) under a seasonal climate (Pérez-Moreno et al. 2024).
Holotype: MPEF Pv 11547 (vertebrate paleontology collection of the Museo Paleontológico "Egidio Feruglio" Trelew, Chubut, Argentina; there is some minor variation in the text concerning the exact formula, things like dashes and commas and so forth), an associated partial skeleton mostly represented by the hind limbs. Individual bones get a "/[#]" after the 11547. They include an incomplete posterior caudal vertebra, incomplete ribs, a couple of chevrons, the left humerus, a fragment of the left ilium, a fragment of the right pubis, the right femur and the distal end of the left femur, both tibiae and fibulae, the right astragalus, and the left astragalus (incomplete). They were found in an area about 4 m by 4 m (13 ft by 13 ft) (Pérez-Moreno et al. 2024).
[this is where I would put a quarry map figure from the publication, except it's free access and not open access and doesn't have information about licenses. So, hey, go here instead and look at Figure 4.]
Unlike most titanosaur type specimens, there is only that one caudal vertebra. It is elongate, with a lateral ridge on the centrum and a distinctly pointed articular "ball" (a bit more of a cone). T. gimenezi instead is the odd titanosaur that gets by mostly on limb elements. Three of the four segments (upper arm, upper leg, and lower leg) are represented by complete elements, and provided T. gimenezi had reasonably typical lower arms, we can get a decent sense of its limb proportions. The humerus is 64.54 cm long (25.41 in), the tibiae average 61.2 cm long (24.1 in) with a variation of 0.2 cm, and the complete femur is 88.5 cm long (34.8 in) (Pérez-Moreno et al. 2024). This is basically Neuquensaurus-size, if you'd like a reference.
[this is where I would put the authors' skeletal reconstruction, except, well, you know. So, go back here for Figure 3.]
Interestingly, the humerus and femur are robust, whereas the tibia is more gracile (Pérez-Moreno et al. 2024). T. gimenezi is still firmly on the "compact chunky" end of the titanosaur spectrum, though. In fact, although the lengths of the limb bones indicate T. gimenezi was comparable to classic saltasaurs Neuquensaurus and Saltasaurus in length and proportions, its anatomy suggests it was heavier, between 5.79 and 9.79 metric tons (6.38 and 10.79 US tons) versus about 5 to 6 metric tons (5.5 to 6.6 US tons) (Pérez-Moreno et al. 2024). This seems to be reflected in its unusual astragali, which are broader than those of the classic saltasaurs and overlap the fibulae more. Phylogenetically, T. gimenezi seems to be close to the classic saltasaurs but not quite in the club (Pérez-Moreno et al. 2024); perhaps its lineage split off after miniaturization was well underway but before the neat pneumatic features showed up. At any rate, T. gimenezi is another example of the titanosaurs' evolutionary mastery of body size range. One wonders what its lineage might have gotten up to had titanosaurs not encountered their own Titanomachy (a massive asteroid strike is certainly worthy of Greek gods).
One other interesting bit: toward the end of the Late Cretaceous, northern Patagonia seems to have been overrun by small titanosaurs (i.e., aeolosaurs, classic saltasaurs), whereas southern Patagonia had large titanosaurians. Central Patagonia is more poorly known but appears to have had a mix, including T. gimenezi (Pérez-Moreno et al. 2024).
A couple of other, unrelated notes:
If you'd like some non-titanosaurian reading material, may I suggest the spring 2024 edition of Park Paleontology News? Also, I've done some housecleaning, checking the links on the external link, museum database, and publication pages, and moving some theropods around on The Compact Thescelosaurus because compsognathids aren't wee little adult theropods, they're juveniles.
References
Pérez-Moreno, A., L. Salgado, J. L. Carballido, A. Otero, and D. Pol. 2024. A new titanosaur from the La Colonia Formation (Campanian-Maastrichtian), Chubut Province, Argentina. Historical Biology (advance online publication). doi: https://doi.org/10.1080/08912963.2024.2332997.
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