Occasionally I glance at the site statistics, but since I don't use anything detailed there's not a lot to get from them except that it's fun to see where the obvious spoof hits are coming from (Singapore, lately; sometimes Hong Kong or Russia). Sometimes I can tell that a post has been picked up elsewhere and gotten a few views. Over the last month or so, there have been an unusually large number of visits to "Titanosaur osteoderms: functions and conclusions", and at the same time a similar number of visits have come from a service at the University at Buffalo. Conclusion? Seems like someone at the university is using the post in a course. If that's what's going on, this one is for you!
Since I wrote the osteoderm series back in 2019, there have a few reports of interest on titanosaur osteoderms. I added several overlooked and new records to the distribution post in 2019–2020, and there hasn't been much change there since. One tangential note, also applicable to "Titanosaurs of Yesterday", is a further advance in the study of Agustinia ligabuei, the spiky sauropod that wasn't. Bellardini et al. (2022) published an analysis that found A. ligabuei was not a titanosaurian or even a macronarian, but a rebbachisaurid. (And it's still not armored, either.)
As noted in the Menucocelsior arriagadai post, Rolando et al. (2022) was not just a description of a new titanosaur taxon, but also included reports of material from other titanosaurs. Among these specimens were four isolated osteoderms from the Cerro Matadero site of the Allen Formation. Three represent the "ellipsoidal" form (bulb-and-root) of D'Emic et al. (2009) and the other is a "keeled" osteoderm. Rolando et al. interpreted the keeled osteoderm as perhaps from the tail or back of a saltasaur and the two more complete ellipsoidal osteoderms as perhaps aeolosaur osteoderms from the hip region.
Another report also discussed in another post is Fronimos (2021) on an osteoderm of a Big Bend titanosaur (e.g., Big Bend Alamosaurus). To paraphrase, this is a large oval and unkeeled osteoderm from the upper Javelina. It is tall, symmetrical, 19.9 cm long (7.83 in), not hollow, not differentiated into a bulb and root, and does not have a cingulum. It resembles the North Horn Formation Alamosaurus osteoderm and the osteoderms of Mendozasaurus neguyelap and unnamed South American forms (Fronimos 2021). Fronimos (2021) regarded the most likely functions as mineral storage, local defense, and display.
Concerning the function of titanosaur osteoderms, Silva Junior et al. (2022) published a study using finite element analysis to evaluate titanosaur osteoderms versus likely titanosaur adversaries, specifically the bites of abelisaurs and baurusuchid crocs. They found that bites had less of an effect on solid osteoderms (i.e., those without hollow internal spaces), and interpreted this to indicate that solid osteoderms could do more than provide mineral storage. On the other side of the mineral storage question, Broeckhoven and du Plessis (2022) made an analysis of osteoderms in armadillo lizards. Using micro-computed tomography, they found that the female lizards in their study had denser, more compact osteoderms than males, and observed the presence of TRAP-positive cells (tartrate-resistant acid phosphatase, involved in bone resorption and breakdown). Denser osteoderms may help maintain a minimum level of mineral density for reproduction and provide defensive strength to osteoderms also being used for a mineral storage function. The authors did not find a difference in density between seasons, and suggested this meant the osteoderms were only subject to resorption during particularly stressful conditions, or that it only took place during certain phases of embryo growth. They concluded that mineral storage for reproduction is a plausible function for osteoderms in female reptiles.
Finally, I've saved the most interesting update for last. In an abstract, Filippi et al. (2023) described an articulated tail, MAU-Pv-CO-726, from the Bajo de la Carpa Formation of Cerro Overo–La Invernada, Patagonia, Argentina. (Yes, another Bajo de la Carpa mystery titanosaur!) MAU-Pv-CO-726 includes 25 caudals, 11 chevrons, and two osteoderms in place, with another nearby. The pair of osteoderms is associated with the last anterior caudal, found flanking the side and underside of the tail (about where the chevron articulates with the caudal). They are described as bulbous, oval, a little more than 10 cm (4 in) long, and feature a medial ridge and tapered spine on the lateral half, whereas the solitary osteoderm is described more like a classic bulb-and-root. Filippi et al. found MAU-Pv-CO-726 to be the sister taxon of Rinconsaurus caudamirus, marking the first evidence of an armored rinconsaur (and no doubt causing R. caudamirus's usual best friend Muyelensaurus pecheni great phylogenetic distress). They interpreted the location of the osteoderms as evidence of a defensive function. The osteoderms' placement also has implications for paleoart; titanosaur restorations usually put osteoderms on upper-lateral surfaces. But, then again, if you want my opinion I think titanosaurs were too diverse for a one-size-fits-all approach to osteoderms, in function, anatomy, or placement.
References (note that a couple are different from previous usage, as those were online preprints)
Bellardini, F., R. A. Coria, G. J. Windholz, A. G. Martinelli, and M. A. Baiano. 2022. Revisiting the Early Cretaceous sauropod Agustinia ligabuei (Dinosauria: Diplodocoidea) from southern Neuquén Basin (Patagonia, Argentina), with implications on the early evolution of rebbachisaurids. Historical Biology 35(12): 1–27. doi: https://doi.org/10.1080/08912963.2022.2142911
Broeckhoven, C., and A. du Plessis. 2022. Osteoderms as calcium reservoirs: Insights from the lizard Ouroborus cataphractus. Journal of Anatomy 241(3): 635–640. doi: https://doi.org/10.1111/joa.13683
D'Emic, M. D., J. A. Wilson, and S. Chatterjee. 2009. The titanosaur (Dinosauria: Sauropoda) osteoderm record: review and first definitive specimen from India. Journal of Vertebrate Paleontology 29(1):165–177.
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. Publicación Electrónica de la Asociación Paleontológica Argentina 24(R3): R67–R68.
Fronimos, J. A. 2021. Morphology and neurovascular anatomy of a titanosaur (Dinosauria, Sauropoda) osteoderm from the Upper Cretaceous of Big Bend National Park, Texas. Cretaceous Research 120: 104670. doi: https://doi.org/10.1016/j.cretres.2020.104670
Rolando, M. A., J. A. Garcia Marsà, F. L. Agnolín, M. J. Motta, S. Rozadilla, and F. E. Novas. 2022. The sauropod record of Salitral Ojo del Agua: An Upper Cretaceous (Allen Formation) fossiliferous locality from northern Patagonia, Argentina. Cretaceous Research 129: 105029. doi: https://doi.org/10.1016/j.cretres.2021.105029
Silva Junior, J. C. G., F. C. Montefeltro, T. S. Marinho, A. G. Martinelli, and M. C. Langer. 2022. Finite elements analysis suggests a defensive role for osteoderms in titanosaur dinosaurs (Sauropoda). Cretaceous Research 129: 105031. doi: https://doi.org/10.1016/j.cretres.2021.105031
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