A new fossil skull, dug out of purple siltstone in northern China, belongs to a creature that walked the planet about 259 million years ago. The animal was named Yinshanosaurus angustus, and the find helps fill a gap in the family tree of large plant‑eating reptiles that roamed just before the greatest die‑off in Earth’s history.
Unearthing Yinshanosaurus angustus
Dr. Jian Yi and Dr. Jun Liu of the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences (IVPP), compared two well‑preserved specimens from Shanxi and Inner Mongolia.
Both fossils include almost complete skulls, giving researchers a rare full view of the head and much of the spine.
“Pareiasauria are a bizarre herbivorous clade of tetrapods that existed in the Guadalupian and Lopingian and were victims of both the Late Capitanian and the end‑Permian mass extinction events,” reminded Liu.
The more complete of the two skulls measures 10 inches long yet barely 4 inches wide across the cheeks, the narrowest head known for any pareiasaur.
That unusual shape is not the only odd trait. The snout is as wide as it is high, the frontal bone is slender and twice as long as it is wide, and the upper‑jaw teeth stand almost vertical instead of tilting backward as in relatives.
What on Earth is a pareiasaur?
A pareiasaur is a stocky, barrel‑bodied tetrapod that carried a tiny tail and a head often ringed with bony knobs. Most species topped out at about 8 feet long and weighed as much as today’s American bison.
They thrived across the late Permian period, serving as key plant chompers in ecosystems from South Africa to Russia. Their success ended abruptly when roughly 90 percent of marine species and 70 percent of land vertebrates vanished at the close of the era.
Yinshanosaurus angustus foraged on the northern shoulder of Pangea, the single landmass that stitched together today’s continents.
At the time, the interior of the supercontinent swung between searing summers and bitter winters, pressuring animals to adapt or disappear.
China’s Naobaogou and Sunjiagou formations capture that turbulent landscape in stacked mudstones and siltstones.
Periodic floods buried carcasses quickly enough to preserve delicate skeletal links, a stroke of luck for modern paleontologists.
Clues written in bone
Yi and Liu spotted a forked rear projection on the nasal bone and a notch in the tabular bone at the back of the skull, features never seen together before.
They also noticed a U‑shaped paraoccipital process that differs from the V‑shaped version in close cousins.
“The skeleton of Yinshanosaurus angustus provides the complete cranial and articulated postcranial details of Chinese pareiasaurs for the first time,” added Jian Yi after months of lab preparation.
Using 183 anatomical characters, the team ran computer analyses that split Chinese pareiasaurs into three distinct branches, placing the new taxon beside Shihtienfenia completus within a fresh sub‑group.
Why the Permian still matters
The Permian ended with volcanic eruptions in what is now Siberia, pumping out enough carbon dioxide to warm oceans by at least 14°F.
That spike drove ocean anoxia, acid rain, and habitat collapse, setting the stage for the dinosaurs that would follow in the Triassic.
Each newly described pre‑extinction species sharpens models of how ecosystems responded to rising heat and disrupted carbon cycles.
Because pareiasaurs sat low on the land food chain, they reflect the health of primary plant production more directly than predators do.
From dig site to digital tree
CT scans of the Shanxi skull reveal replacement tooth buds waiting beneath worn crowns, confirming lifelong dental turnover like that in modern lizards.
The scans also expose internal canals that once carried blood vessels to horn‑like bosses, suggesting seasonal growth tied to mating display or species recognition
Digital models of those structures feed into the expanding open database hosted by the Chinese Academy of Sciences.
By pooling 3‑D files from separate labs, researchers can test competing family trees without moving fragile fossils across borders.
Yinshanosaurus angustus and the future
Work now shifts to beds just above the current fossil horizon, layers that may hold early Triassic survivors or fresh victims of the end‑Permian crisis.
Liu’s group plans a targeted survey during the next field season, armed with drone‑based photogrammetry to map promising outcrops.
The team also hopes to sample bone collagen, if any remains, for stable‑isotope studies that could reveal diet and seasonal water stress.
Combined with climate models, those data might show whether narrow‑snouted herbivores had a feeding edge in arid late Permian landscapes.
Understanding how a mid‑sized, flat‑snouted browser fit into the pre‑extinction puzzle helps scientists refine the timeline of faunal turnover.
Each added piece, however small, tests broader ideas about resilience and collapse as Earth’s systems tip past critical thresholds.
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Yinshanosaurus angustus image credit: Guo, Institute of Vertebrate Paleontology and Paleoanthropology (IVPP)
The study is published in Papers in Palaeontology.
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