The species, described in 2003 by Prof. Jerzy Dzik, former director of the Institute of Paleobiology at the Polish Academy of Sciences (PAN), dates to roughly 230 to 225 million years ago, a period known as the Late Triassic.
For Poland, the Krasiejów finds carry outsized scientific weight.
The near-complete skeletons preserved there allow questions about anatomy, diet, and movement to be tested in detail, and they keep the “Silesian lizard from Opole” at the center of a debate that continues to shape our understanding of how dinosaurs began.
“Silesaurus is very well known among specialists studying the dawn of the dinosaur era, it appears in vertebrate paleontology textbooks written around the world,” said Mateusz Tałanda, a researcher at the University of Warsaw.
He added that the Krasiejów material remains pivotal because Poland holds an almost complete skeleton, missing only the tail tip and the hands, a level of preservation not yet matched at other sites.
The discovery reshaped how scattered early finds were classified. Since Silesaurus was named, researchers have identified about 10 close relatives on several continents, a group now called silesaurids, after the Polish species.
Bones attributed to this family have been reported from today’s United States, Brazil, Argentina, Morocco, Madagascar, Zambia and Tanzania, suggesting these animals were widespread when the supercontinent Pangaea still linked the landmasses.
The central dispute is taxonomic. Some scientists regard Silesaurus as an early member of the ornithischians, the “bird-hipped” branch of dinosaurs, while others place it just outside true dinosaurs as a near cousin.
The gap stems from a missing fossil record for the first 30 million years of ornithischian evolution, leaving few points of comparison.
“Silesaurus sits close to that boundary,” Tałanda said, noting that the debate is likely to continue until a transitional form is found that clearly links silesaurids with undisputed bird-hipped dinosaurs.
Silesaurus was a modest-sized animal, reaching up to 3 meters in length and standing roughly waist-high to an adult human. It had a short, beak-like snout on the lower jaw and relatively blunt teeth at the front of the upper jaw.
The head connected to a long neck and a body borne mainly on four limbs. The forelimbs were long and slender, better suited for support than speed, while the hind limbs were stronger but still slim, and the tail was long.
The combination is unusual for the earliest dinosaurs, which tend to have short, powerfully built forelimbs. Researchers are testing whether Silesaurus’ proportions represent an intermediate stage toward later dinosaur body plans, or a side track that eventually disappeared.
Diet is another open question. Fossilized droppings, known as coprolites, attributed to silesaurids contain abundant insect remains. This points to an insect-rich menu, possibly supplemented by soft plant matter or carrion.
If so, Silesaurus was likely omnivorous, feeding on foods that would leave few durable traces in the fossil record.
Scientists are also probing why silesaurids spread across parts of the Americas and Africa yet are known in Europe only from Poland, and when they finally vanished.
The youngest remains, including specimens from Poręba near the southern town of Zawiercie, are about 210 million years old, though researchers say the lineage may have persisted longer.
Current studies include computer simulations to reconstruct how Silesaurus moved, work that could clarify both its lifestyle and its place among the earliest dinosaurs.
(rt/gs)
Source: naukawpolsce.pl