Paleontologists have discovered a new species of dinosaur that yields a wealth of insights into the biology and behavior of titanosaurs, the dinosaur group that includes the most massive land animals that have ever existed. Named Sarmientosaurus musacchioi, the new creature is represented by a single fossil specimen that includes an essentially complete, exquisitely-preserved skull—arguably the best yet found for any titanosaur—as well as part of the neck. The article describing the discovery appears today in the well-known, freely-accessible journal PLOS ONE.
The Sarmientosaurus skull and neck were unearthed in southern Chubut Province, Argentina, in the central part of the wild, windswept region known as Patagonia. The fossils were found in rocks laid down during the middle of the Cretaceous Period (the third and final period of the Mesozoic Era, or Age of Dinosaurs), roughly 95 million years ago. The specimen was discovered by the leader of the study, paleontologist Dr. Rubén D. F. Martínez of the Laboratorio de Paleovertebrados of the Universidad Nacional de la Patagonia San Juan Bosco (UNPSJB) in the city of Comodoro Rivadavia, Argentina. US-based members of the research team include paleontologist Dr. Matt Lamanna of Carnegie Museum of Natural History in Pittsburgh, Pennsylvania and paleobiologists Dr. Lawrence Witmer and Ryan Ridgely of the Ohio University Heritage College of Osteopathic Medicine in Athens, Ohio. Rounding out the team are several other Argentine scientists, including geologist Gabriel Casal of the UNPSJB, paleontologist Dr. Fernando Novas of the Museo Argentino de Ciencias Naturales in Buenos Aires, and Dr. Javier Martínez and Javier Vita, medical professionals in Comodoro Rivadavia who conducted CT (computed tomographic or ‘CAT’) scans of the Sarmientosaurus bones. “Discoveries like Sarmientosaurus happen once in a lifetime,” says study leader Martínez. “That’s why we studied the fossils so thoroughly, to learn as much about this amazing animal as we could.”
Titanosaurs are an important but mysterious group of dinosaurs. They are a type of sauropod, the huge, long-necked, long-tailed plant-eaters that many people think of when they hear the word “dinosaur.” Comprising more than 60 named species, titanosaurs lived on every continent and ranged in size from the weight of a cow to at least the weight of the biggest sperm whale. They were the most common large herbivores in the Southern Hemisphere landmasses during the Cretaceous. Despite their remarkable species richness and diversity in body size, many aspects of titanosaur anatomy, evolution, behavior, and ecology are not well understood. This is due in large part to the fact that skulls of these animals—which are fundamental for deciphering critical aspects of their biology—are exceedingly rare. Of the 60-plus named titanosaurs, only four (Nemegtosaurus, Rapetosaurus, Tapuiasaurus, and now Sarmientosaurus) are represented by nearly or even reasonably complete skulls. “Titanosaurs included the biggest land animals ever, so we want to know as much about them as we can,” notes Dr. Lamanna. “But to truly understand a creature, you need to have its head. And because titanosaur skulls are super-rare, lots of important aspects of how these dinosaurs lived and behaved have really been anybody’s guess.”
Although Sarmientosaurus itself was not particularly large by titanosaurian standards, its skull casts crucial new light on many facets of the biology of these sauropod dinosaurs. It provides scientists with their first good look at the head of an anatomically ‘primitive’ titanosaur, offering new information on the origins and evolutionary relationships of these animals. Furthermore, the team’s CT-based analyses of the Sarmientosaurus skull have yielded some of the most comprehensive information to date regarding the brain and senses of titanosaurs, or indeed, any sauropods. As is typical of sauropods, the brain of Sarmientosaurus was small relative to its enormous body, but its sensory capabilities outstripped those of most other sauropods, with a large eyeball and good vision and an inner ear better tuned for hearing low-frequency airborne sounds than other titanosaurs. Moreover, the balance organ of the inner ear indicates that this dinosaur probably habitually held its head with the snout facing downward, which may in turn suggest that it fed primarily on low-growing plants. According to Prof. Witmer, an expert on cranial anatomy, “The Sarmientosaurus skull is beautifully-preserved, which meant that we could tease out a ton of information. It was really exciting for us to work through the CT scan data because it gave us a glimpse into the biology and lifestyle of this animal like we rarely get with dinosaurs.”
The comparatively primitive architecture of the Sarmientosaurus skull and teeth contrasts that of the more ancient Tapuiasaurus, indicating that titanosaurs with radically different cranial and dental forms coexisted for much of the Cretaceous. This underscores the ecological and anatomical diversity of these sauropods, especially in the Southern Hemisphere continents. Sarmientosaurus is also the first non-avian (i.e., non-bird) dinosaur to preserve a bizarre structure in the neck that Dr. Martínez and team have interpreted as an extremely elongate bony tendon. The function of this structure remains unknown.
Sarmientosaurus musacchioi is named for the town of Sarmiento in Chubut Province, which is close to the discovery site. The species name honors the late Dr. Eduardo Musacchio, a paleontologist and professor at the UNPSJB who was a friend to Dr. Martínez and other members of the team.
A media event to announce the discovery will be held at Carnegie Museum of Natural History at 10:30 AM US Eastern time. Drs. Martínez, Lamanna, and Witmer will be on hand to address questions and give interviews; also, life-sized, scientifically accurate, 3D-printed replicas of the skull and reconstructed brain endocast of Sarmientosaurus will be available for viewing and photography. The article will be published in PLOS ONE at 2 PM Eastern and is under strict embargo until that time.
For comment, contact:
Rubén D. F. Martínez, PhD, Universidad Nacional de la Patagonia San Juan Bosco (Argentina), email@example.com, 54-0297-4843057
Matthew C. Lamanna, PhD, Carnegie Museum of Natural History (USA), LamannaM@carnegiemnh.org, 412-578-2696 / 412-592-3361
Lawrence M. Witmer, PhD, Ohio University (USA), witmerL@ohio.edu, 740-591-7712
Further information and resources:
PLOS ONE article (open-access; freely available after 2 PM EDT, April 26, 2016): http://dx.plos.org/10.1371/journal.pone.0151661
Still images, animations, and interactive 3D digital model for download (with captions and credits): https://www.dropbox.com/sh/in3tupno91h0haw/AACJmvc05hB7fk5tkeNcwgCBa?dl=0
YouTube animation of the Sarmientosaurus skull and brain endocast: https://www.youtube.com/watch?v=Zb8e5ffEC74
Interactive Sketchfab animation of the Sarmientosaurus skull: https://skfb.ly/MKOP
Interactive Sketchfab animation of the transparent Sarmientosaurus skull showing the brain endocast inside: https://skfb.ly/MKLO
Interactive Sketchfab animation of the Sarmientosaurus brain endocast: https://skfb.ly/MKKH