Paleontologists have unveiled Haolong dongi, a remarkable new iguanodontian dinosaur from China’s Yixian Formation, whose 125-million-year-old juvenile specimen preserves the first-ever hollow, cutaneous spikes in any dinosaur—structures eerily reminiscent of a hedgehog’s or porcupine’s quills.

Unearthed in northeastern China’s Lujiatun Member and described in Nature Ecology & Evolution (February 2026), the near-complete fossil reveals an Early Cretaceous herbivore belonging to the lineage that later produced duck-billed hadrosaurs. Exceptionally preserved skin shows non-overlapping body scales interspersed with hollow, cylindrical keratinous spikes of varying lengths (mostly 2–3 mm, some longer), growing directly from the dermis—distinct from scales, proto-feathers, or bony osteoderms.

Lead author Jiandong Huang (Anhui Geological Museum) emphasizes the unprecedented cellular detail: “Individual cell nuclei remain visible, offering a window into dinosaur integument never seen before.” The spikes’ hollow interiors suggest lightweight yet effective defenses, possibly deterring predators like the porcupine’s quills while potentially aiding thermoregulation or sensory perception.

Named “spiny dragon” (Haolong = spiny dragon in Chinese) in honor of the late paleontologist Dong Zhiming, this juvenile specimen challenges ᴀssumptions about ornithischian skin evolution. Previously, only scale impressions existed from Early Cretaceous iguanodontians; here, a mosaic of scales and hollow spikes hints at greater diversity in skin appendages than imagined.

The find underscores the Yixian Formation’s status as a Lagerstätte, yielding insights into a lush, volcanic landscape teeming with feathered dinosaurs and early birds. As further CT scans and comparative studies proceed, Haolong dongi promises to illuminate how these “spiny dragons” defended themselves—and how such structures may have prefigured later hadrosaur armor. A true hedgehog of the Cretaceous, reborn from the rocks of China.