Paleontologists have found evidence of a previously unrecognized soft tissue structure in the cheek region of many dinosaur species, which they’ve called the exoparia. The finding deepens our understanding of dinosaur anatomy and highlights the limitations of current methods of reconstructing parts of dinosaur anatomy that can’t be well preserved.
Visualization of a soft tissue of Edmontosaurus created by photography, 3D modeling, digital painting, and histology of bones from Dinosaur Provincial Park, Alberta, Canada. Image credit: Henry Sharpe.
“Because muscles and tissues degrade over time, there are very few examples of soft anatomy like this from dinosaurs,” said Henry Sharpe, a paleontologist at the University of Alberta.
“Although bones can be unearthed and reassembled into semi-complete skeletons, for a long time no one really had a method for how to figure out what muscles and tissues dinosaurs may have had.”
“That changed in the 1990s with the creation of the Extant Phylogenetic Bracketa method that uses dinosaurs’ closest modern relatives — crocodiles and birds — to gain insight into dinosaurs’ tissues and muscles.”
“There’s just one problem with this approach. 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?”
“It’s this question that ran through my mind as I was examining the skull of an Edmontosaurus named Gary. There was a peculiar flanged structure on the bone near the cheek that caught his eye.”
“When I began looking into what it could be, I couldn’t find any answers.”
“There were these big, corrugated parts of the skull. 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 got us thinking: What if there’s something here that is against the currently thought of model of dinosaur muscles?”
In their quest to better understand this piece of dinosaur anatomy, Sharpe and his colleagues from the University of Alberta, the University of Toronto, the Royal Ontario Museum and the University of New England began examining the same area of the skull in other dinosaur species and found evidence of the same structure across the board.
“It was always in the same spot, which to us was a pretty good indication that this was one muscle or one ligament,” Sharpe said.
To confirm their hypothesis that this area of the bone was formerly the site of some type of soft tissue structure, the researchers cut thin sections of dinosaur bone.
“Soft tissues like muscles or ligaments are anchored to the bone by collagen fibers,” Sharpe said.
“It helps anchor that muscle or that ligament into the bone, to prevent it from pulling away from the bone and causing the animal injury.”
After the soft tissue has decayed and all that’s left is the bone, bits of these collagen fibers remain and can be analyzed when looking at thin slices of bone by shining polarized light through it.
“It looks like someone’s taken the bone right beneath the surface and scratched it with an X-Acto knife,” Sharpe said.
The researchers also used a technique they called THLEEP to look at multiple angles of bone slices from the cheekbone and lower jaw, examining the 3D orientation of the fibers.
“This was because these collagen fibers won’t just insert at any odd angle; they’ll follow the angle that the muscle’s inserting at,” Sharpe said.
In every dinosaur species the scientists looked at, the collagen fibers showed there was a connection between the cheek and lower jaw, verifying that the soft tissue structure was something akin to a cheek muscle or ligament.
There was variation in the sizes and angles of attachment between different dinosaur species, which indicates this new soft tissue was used for something specialized, like stabilizing the jaw or contributing to how dinosaurs consumed food.
“We don’t know exactly what it’s being used for, but we know that clearly it’s important to how these dinosaurs are chewing differently, because they’re modifying it in different ways,” Sharpe said.
“This discovery also highlights the need to look beyond comparing dinosaur fossils with modern relatives to get a more comprehensive and accurate understanding of the extinct creatures’ 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.”
The findings were published in the Journal of Anatomy.
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Henry S. Sharpe et al. Skull morphology and histology indicate the presence of an unexpected buccal soft tissue structure in dinosaurs. Journal of Anatomypublished March 21, 2025; doi: 10.1111/joa.14242
This article is a version of a press-release provided by the University of Alberta.
Dinosaur Anatomy Revolutionized: An Interview with Paleontology Expert Dr.vivian Holloway
Paleontology has taken a fascinating turn with the recent revelation of a previously unrecognized soft tissue structure in dinosaurs, dubbed the “exoparia.” This groundbreaking find challenges existing understanding of dinosaur anatomy and opens exciting new avenues for research. To delve deeper into this discovery and its implications, Time.news spoke with Dr. Vivian Holloway, a leading expert in dinosaur anatomy and biomechanics.
Time.news: Dr. Holloway, thank you for joining us. This “exoparia” discovery is making waves.Can you explain to our readers what exactly has been found?
Dr.Holloway: Absolutely. The research, primarily led by Henry Sharpe, has identified evidence of a soft tissue structure, likely a muscle or ligament, in the cheek region of various dinosaur species. The team calls it an “exoparia”,and it was previously unrecognized. This soft tissue isn’t usually preserved, so its discovery is incredibly notable.It suggests a complexity in dinosaur anatomy that we hadn’t fully appreciated before.
Time.news: Current methods of reconstructing dinosaur anatomy rely heavily on the “Extant Phylogenetic bracket,” comparing dinosaurs to their modern relatives – crocodiles and birds. How does this exoparia discovery challenge this method?
Dr. Holloway: that’s a crucial point. The Extant Phylogenetic Bracket has been invaluable, allowing us to infer muscle and tissue structures based on what exists in crocodiles and birds. Though, this new finding indicates that dinosaurs might have possessed unique anatomical features not found in their modern relatives. As Sharpe articulated, reconstructing dinosaurs solely based on crocodiles and birds creates a significant limitation because dinosaurs may have had unique muscles. The exoparia discovery highlights the need to move beyond just comparative anatomy and consider unique dinosaurian features.
Time.news: The article mentions that the researchers examined an Edmontosaurus skull and identified a peculiar structure near the cheek. What methods did they use to confirm that this was, in fact, a soft tissue attachment site?
Dr. Holloway: The team employed a multi-pronged approach, which is what makes this finding so compelling. Firstly, they found similar structures across multiple dinosaur species, indicating it wasn’t just an anomaly. Then,they used histology,examining thin sections of bone under polarized light to identify remnants of collagen fibers. These fibers, which anchor soft tissues to bone, leave a characteristic “scratched” pattern on the bone surface. they utilized a technique called THLEEP to analyze the 3D orientation of these collagen fibers, confirming that they were aligned in a way consistent with muscle or ligament attachment.
Time.news: So, what does this exoparia do? The article suggests it might be related to chewing.
Dr. Holloway: That’s the million-dollar question! The variation in size and attachment angles of the exoparia across different dinosaur species suggests it played a role in jaw stabilization or food processing. It’s likely that this soft tissue structure contributed to the diverse feeding strategies we see in dinosaurs. Further research is needed to pinpoint the exact function, potentially involving biomechanical modeling and comparative studies with modern animals.
Time.news: What are the broader implications of this discovery for the field of paleontology? How will this impact future research on dinosaur anatomy?
Dr. Holloway: this discovery is a wake-up call. It underscores the fact that there’s still so much we don’t know about dinosaur anatomy. It encourages paleontologists to look beyond the limitations of current reconstruction methods and to explore novel techniques for identifying and interpreting evidence of soft tissues in fossils. It means we need continue to improve techniques that enable us to visualize and also identify soft tissue.It also reinforces the importance of meticulous examination of fossil bones, even seemingly insignificant features, as they may hold clues to undiscovered anatomical structures.
Time.news: For our readers who are fascinated by dinosaurs, what practical advice would you give them on how to learn more about these kinds of discoveries and engage with paleontology?
Dr. Holloway: Stay curious! Follow reputable science news sources, like Time.news, and read articles about paleontology. Many museums and universities offer public lectures and tours led by paleontologists. Consider volunteering at a museum or participating in citizen science projects that involve fossil identification.And don’t be afraid to delve into the scientific literature – many journals offer accessible summaries of their research findings. The field of paleontology is constantly evolving, and there are always new discoveries to be made!
Time.news: Dr. Holloway, thank you for sharing your expertise with us today. This is truly an exciting time for dinosaur research.
Dr. holloway: My pleasure. The “exoparia” discovery is a stunning reminder of the mysteries still hidden within the fossil record. There are still remarkable discoveries waiting to be unearthed!
