The Therizinosaurus, an ancient inhabitant of the Late Cretaceous period, is known for its unusual appearance, including forelimbs with claws over half a meter long. Its distinctive features have led to popular culture portrayals suggesting impaired senses. However, scientific understanding reveals a different picture regarding its visual capabilities.
The Therizinosaurus’s Vision
Contrary to popular depictions, the Therizinosaurus was not blind. Scientific consensus, based on fossil evidence, indicates this large herbivore possessed effective vision. Fictional portrayals, such as those in “Jurassic World Dominion,” depicting a blind or visually impaired Therizinosaurus, are creative liberties. Such a condition would have severely hindered its survival in its natural environment.
Paleontologists utilize advanced techniques, including computerized tomography (CT scans) of fossilized skulls, to examine internal sensory organ structures. These analyses suggest the Therizinosaurus had well-developed optic lobes within its brain, which are regions responsible for processing visual information. A larger and more complex optic lobe correlates with better visual acuity, implying the Therizinosaurus relied significantly on sight for navigation.
Deciphering Dinosaur Senses
Paleontologists employ several methods to infer the sensory capabilities of extinct dinosaurs. One approach involves examining fossilized skull structures. The size and shape of the orbits, or eye sockets, provide clues about the size of the eyeballs they once housed. This estimation relies on comparative anatomy, drawing parallels with living archosaurs like birds and crocodiles, whose eye-to-orbit ratios are well understood.
Beyond the orbits, scientists study endocasts, which are molds of the brain cavity. These endocasts reveal the morphology and relative proportions of different brain regions, including the optic lobes and areas associated with the optic nerve. Internal neurovascular canals, such as those for the optic nerve, are identified through CT scans, providing insights into visual processing. While soft tissues rarely fossilize, these skeletal and endocranial proxies offer reliable data for reconstructing ancient sensory worlds.
Vision and the Therizinosaurus Lifestyle
The inferred visual capabilities of the Therizinosaurus played a role in its daily existence and ecological niche. As a colossal herbivore, standing approximately 4 to 5 meters tall and weighing over 5 tons, its primary activity was foraging for plant material. Its exceptionally long neck and unique, scythe-like claws, which could reach up to 50 centimeters, were adapted for stripping leaves and pulling down high vegetation. Good eyesight would have been advantageous for efficiently locating and identifying suitable plant sources within its environment.
Vision also contributed to its interaction with its surroundings and potential threats. While its massive claws are often sensationalized, they were likely used for defense or intimidation against predators like the contemporary Tarbosaurus bataar, rather than active combat. Its ability to perceive its surroundings visually would have aided in detecting predators and deploying its defensive adaptations. The overall physical structure of Therizinosaurus, including its posture and limb proportions, may also have conveyed visual signals, potentially for social communication or territorial displays.