Edmontosaurus’ scales can be genuine fossil evidence even when the skin that made them has disappeared. In the specimens nicknamed Ed Junior and Ed Senior, a thin mineral layer records the body’s outer surface. Calling them dinosaur mummies describes their extraordinary body outlines; it does not establish that ancient flesh remains inside.
The surface preserves anatomy, while mineral analysis identifies what now carries that anatomy. Reading the two kinds of evidence together avoids mistaking a detailed outline for surviving flesh.
A skeleton and an exterior answer different questions
The two Edmontosaurus annectens specimens came from east-central Wyoming. The University of Chicago’s account of the 2025 study describes a late juvenile and an early adult from river deposits about 66 million years old. Researchers combined them to reconstruct an unusually complete external profile.
The scale texture, fleshy midline crest and toe coverings add information a skeleton cannot supply alone. Many scales were only one to four millimeters across. Wrinkles over the ribcage also recorded a much finer surface than a broad outline around the bones.
Bone constrains a reconstruction without supplying every external contour. Think of a hand skeleton: it would not independently show the exact thickness of each fingertip pad or the arrangement of surface creases. That comparison explains the information gap; it is not evidence that dinosaur tissue behaved exactly like human skin.
The UNED researchers’ report describes complementary preservation. Ed Junior includes the skull, trunk and beginning of the tail; Ed Senior extends from the back toward the tail tip. A reconstructed whole therefore combines specimens rather than revealing one untouched animal.
What the mineral boundary contains
The detailed 2026 analysis by Saitta and colleagues investigated structure and chemistry. It found little evidence of original organic material or internal tissue structure in these two specimens. The outer rendering is largely a clay layer less than a millimeter thick, dominated by kaolinite with some illite.
This is more specific than saying that everything “turned to stone.” The relevant object is a boundary marking where the body surface lay. Material on either side can look like ordinary sediment, while the interface retains scales and contours.
Imagine lifting your hand from a mold. The mold can retain a faithful shape without retaining your cells. That analogy helps separate information from substance, although the fossil process was more complex than pressing skin into soft material. Researchers propose a mineral template forming along a decaying surface.
Drying bought time; burial supplied support
The university reports describe a proposed sequence of partial drying followed by rapid burial in wet river sand. The carcass did not remain permanently embalmed. A microbial film associated with the decaying exterior helped create conditions in which clay accumulated along its surface.
Sand also entered the body. Support from within matters when reconstructing how an exterior could retain three-dimensional form after the material beneath it broke down. An unsupported shell and an infilled body present different mechanical situations.
In the 2026 paper, the precise clay-forming route remains a subject for investigation. The authors discuss both accumulation of existing particles and local formation of clay. The mineral layer is observed; the complete sequence of microbial and chemical events is a reconstruction from the surviving evidence.
That distinction changes how to read an illustration of the process. A diagram can put drying, flooding, infilling and clay accumulation into a comprehensible order. It cannot turn each pictured moment into a directly observed event. A proposed drought setting also does not establish the individual animal’s cause of death.
Fossilization is a family of processes
The National Park Service explains permineralization as minerals entering natural pores in material such as bone, wood or shell. Replacement instead substitutes minerals for original material that dissolves away. The processes can occur together, but they mean different things.
Clay templating focuses on a different piece of information: an external surface. Finding a detailed body outline therefore does not tell us, on its own, which molecules or tissue structures remain. Those require their own analyses. Our guide to how a dinosaur becomes a fossil explains why different parts of one animal can leave different kinds of record.
This is also why the word “preserved” needs an object. Preserved shape, preserved microscopic structure and preserved organic compounds are distinct claims. A result demonstrating the first should not silently become evidence for all three.
Reading the outline without inventing the animal
UNED’s account describes 3D recording and CT work used to assemble the external anatomy. Our earlier article on Edmontosaurus’ hoof-like toes follows that anatomical result. Here, the preservation mechanism explains why such an outline exists even though the original covering is gone.
A preserved crest supports including a crest in a reconstruction. It does not independently identify courtship behavior, sex or coloration. Likewise, a clay surface’s present color is not a reliable record of the living animal’s palette. The cover is an editorial reconstruction rather than a specimen photograph or evidence of original color.
There is a practical consequence for preparation. Chicago describes careful work exposing the delicate interface rather than simply removing all non-bone material. The scientifically valuable object can be the thin boundary beside a recognizable skeleton.
The observations establish a detailed exterior recorded in minerals. Partial drying, burial, infilling and clay accumulation offer a reconstruction of how it formed, with some chemical steps still unresolved. Keeping that reconstruction separate from the observed layer lets the scale and toe anatomy remain useful evidence even after the original covering disappeared.
