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May 27 2025
6In a groundbreaking study, researchers have uncovered evidence of a previously unrecognized soft tissue structure in the cheek area of numerous dinosaur species. This structure, named the "exoparia," provides new perspectives on dinosaur anatomy and underscores the limitations of current reconstruction techniques that rely heavily on comparisons with modern relatives.
The discovery was spearheaded by Henry Sharpe, a master's student in the Department of Biological Sciences, and detailed in the Journal of Anatomy. Sharpe, who also identifies as a "paleoartologist" due to his work in creating lifelike dinosaur renderings for research, stumbled upon the finding while examining the skull of an Edmontosaurus specimen nicknamed Gary. He noticed a peculiar flanged structure near the cheekbone that didn't align with known anatomical features.
"There were these big, corrugated parts of the skull," Sharpe explained. "If we were looking at a mammal skull, we'd say that's the cheek muscle. But reptiles aren't supposed to have a cheek muscle." This observation led the team to question existing models of dinosaur musculature.
Traditionally, scientists have used the "Extant Phylogenetic Bracket" method to reconstruct dinosaur anatomy, comparing them to their closest living relatives—crocodiles and birds. However, Sharpe pointed out a significant limitation: "Every muscle you would ever reconstruct in a dinosaur would only be one that's in a crocodile or a bird. What if dinosaurs had their own muscles that either weren't present in the dinosaurs that led to birds, or that birds lost or adapted into something else?"
To explore this possibility, Sharpe and his team examined the same cheek region in other dinosaur species and consistently found similar structures. They hypothesized that these areas were sites of soft tissue attachments, such as muscles or ligaments. To test this, they prepared thin sections of dinosaur bone and analyzed them under polarized light. This technique revealed remnants of collagen fibers—indicative of soft tissue attachments—that appeared as scratch-like marks beneath the bone surface.
Further analysis using a technique dubbed THLEEP allowed the researchers to examine the three-dimensional orientation of these fibers. They discovered that the collagen fibers consistently connected the cheekbone to the lower jaw across various dinosaur species, suggesting the presence of a soft tissue structure akin to a cheek muscle or ligament.
Interestingly, the size and angle of these attachments varied among species, implying that the exoparia served specialized functions, possibly related to jaw stabilization or feeding mechanisms. "We don't know exactly what it's being used for," Sharpe noted, "but we know that clearly it's important to how these dinosaurs are chewing differently, because they're modifying it in different ways."
This discovery challenges the reliance on modern analogs for reconstructing extinct species' anatomy. "There's a ton of diversity in dinosaurs that we're just missing because we're trying to explain the past only in the terms of the present," Sharpe emphasized.
To facilitate further research, Sharpe and his collaborators have made their bone slide images and methodologies publicly available, encouraging other scientists to investigate the exoparia in additional dinosaur species. "We hope our study is a cautionary tale for how much we can assume and how much we have to dig deep and verify our assumptions, or challenge them when they're not right," Sharpe concluded.
Source:https://phys.org/news/2025-05-cheeky-discovery-scientists-previously-unknown.html
This is non-financial/medical advice and made using AI so could be wrong.
