The fossil of Archaeopteryx is one of the most famous in the world, yet a Chicago specimen has just yielded a set of bizarre features that had literally been hiding in the rock. Using ultraviolet light and high‑resolution CT scans, a 2025 Nature paper on the Field Museum’s specimen FMNH PA 830, unearthed in 1990, reveals new details of how this proto bird flew and fed. The findings turn a classic icon of evolution into a far more dynamic animal, with specialized wing feathers, a mobile tongue, and a mouth lined with soft, tooth‑like structures.
The Specimen’s Journey to Chicago
The fossil now known as the Chicago Archaeopteryx, catalogued as FMNH PA 830, began its story in the fine‑grained Solnhofen Limestone, where it was unearthed in 1990. According to the Field Museum’s institutional history, the slab and counterslab remained in private hands for decades, away from the kind of intensive lab work that has transformed other famous Archaeopteryx specimens. That long detour helps explain why some of the most striking details of this individual stayed invisible until very recently.
The Field Museum reports that the fossil finally arrived in Chicago in August 2022, when it was acquired for the museum’s collection and entered a new phase of scientific preparation. Conservators used X‑ray imaging as they stabilized the rock, which helped map bones and hidden structures before any physical work on the slab. Only after that behind‑the‑scenes effort did the institution unveil FMNH PA 830 to the public, setting the stage for the intensive UV and CT investigations that underpin the new 2025 Nature study.
Breakthrough in Flight Features
The most eye‑catching flight revelation involves a set of specialized inner secondary feathers, or tertials, identified on both wings of the Chicago Archaeopteryx. The Nature paper on FMNH PA 830 describes how these tertial feathers had not been clearly documented in previous Archaeopteryx fossils, in part because they blend into the body outline in normal light. Under ultraviolet illumination, however, the team could trace distinct soft‑tissue feather impressions that mapped out a row of tertials tucked against the torso.
These tertials matter because they help close the gap between the wing and the body, smoothing airflow where turbulence can sap lift and control. A major wire summary of the Nature findings explains that by filling this gap, the tertials would have improved aerodynamic performance in a way that aligns Archaeopteryx more closely with modern birds than previously appreciated. Reporting that synthesizes the Nature study’s flight analysis notes that these feathers support the idea of an animal capable of active, controlled flight, rather than a purely gliding or tree‑hopping dinosaur.
Surprising Feeding Adaptations
If the wings refine how Archaeopteryx flew, the head of FMNH PA 830 reshapes how it may have fed. A detailed anatomical report on the Chicago Archaeopteryx, published as a Primary study of feeding traits, describes evidence for an additional tongue‑supporting element in the throat region that is consistent with increased tongue mobility. Using CT‑based reconstructions of the skull and palate, the authors argue that this extra support structure would have given the tongue more freedom to move, a feature associated in modern birds with precise prey handling or nectar feeding.
The same Primary analysis identifies soft‑tissue traces on the palate that the researchers interpret as oral papillae, tooth‑like projections that help grip and guide prey inside the mouth. According to that feeding‑focused study of the Chicago Archaeopteryx, these papillae would have functioned somewhat like a built‑in conveyor, steering struggling prey toward the throat even as the jaws themselves remained relatively simple. Together, the mobile tongue support and palatal papillae push Archaeopteryx away from the old image of a generic toothed dinosaur and toward a more specialized, bird‑like feeder.
Methods That Uncovered the Secrets
None of these details would have been apparent from a casual look at the slab. The research team relied on a combination of ultraviolet light and CT scanning to peel back layers of rock and reveal hidden anatomy. In the Nature description of FMNH PA 830, the authors explain that UV light made faint soft‑tissue outlines glow against the limestone, exposing feather tracts and skin impressions that blend into the matrix under visible light. This approach was key to identifying the tertial feathers and subtle soft‑tissue structures around the head and neck.
High‑resolution CT scans did the heavy lifting for internal anatomy, particularly the skull and palate. By digitally slicing through the fossil, the team reconstructed the bony framework that supports the tongue and the complex joints between the upper jaw and braincase. Coverage that synthesizes these methods, such as a Valuable for overview of the Nature study, highlights how CT data also revealed scale‑covered foot pads that had been embedded in the rock. Earlier Archaeopteryx specimens had not been scanned at this level of detail, so the Chicago fossil effectively sets a new benchmark for what can be extracted from even long‑known species.
Why These Features Matter for Bird Evolution
All of these discoveries feed into a larger question: where exactly does Archaeopteryx sit on the path from non‑avian dinosaurs to modern birds? The Primary Nature analysis of the Chicago Archaeopteryx argues that FMNH PA 830 helps bridge that gap by tying advanced flight features and refined feeding tools to a skeleton that still looks unmistakably dinosaurian. Specialized tertials that close the wing‑body gap suggest a more efficient flier than earlier reconstructions, while the scale‑covered foot pads visible in the CT data keep one foot, literally, in the reptilian world.
On the feeding side, the tongue‑supporting element and oral papillae described in the Primary feeding report feed into ongoing debates about cranial kinesis, the ability of the upper jaw to move relative to the braincase. Contextual coverage that Includes expert reaction on the Nature findings notes that some specialists see the Chicago specimen’s palate and skull joints as early steps toward the highly kinetic beaks of modern birds. Others caution that the available data still allow for a more limited range of motion. Either way, the combination of feeding and flight adaptations in a single fossil sharpens Archaeopteryx’s role as a genuine transitional form rather than a simple icon on a museum wall.
Lingering Questions and Future Research
For all its detail, FMNH PA 830 does not settle every argument about Archaeopteryx. Interpretations of soft tissues are especially vulnerable to uncertainty, since UV outlines and CT densities can sometimes be ambiguous. The authors of the Primary feeding study acknowledge that their identification of oral papillae and a distinct tongue‑supporting element rests on patterns that could be tested only by comparing them with additional specimens. Likewise, the tertial feathers on the wings, while clearly mapped in UV, raise questions about how variable such structures were across different Archaeopteryx individuals and growth stages.
Researchers quoted in broader coverage of the Major Nature findings from Chicago emphasize that the next step is to apply the same UV and CT toolkit to other Archaeopteryx fossils and closely related species. If the tongue mobility, palatal papillae, tertials, and scale‑covered foot pads turn up elsewhere, they will start to look like standard features of early birds rather than quirks of a single specimen. For now, FMNH PA 830 stands as a vivid reminder that even the most iconic fossils can still surprise us when new technology, and a fresh look, hit them from the right angle.
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*This article was researched with the help of AI, with human editors creating the final content.
