Two-pronged bristletails (Diplura) are a group of non-insect hexapods, living alongside springtails and proturans as one of the earliest branches in hexapod evolution. Because they are closely related to insects, they are key to understanding how insects originated and evolved. Two-pronged bristletails live almost everywhere, in caves, soil, and leaf litter, and play a role in soil ecosystems. Their most striking feature is a pair of highly specialized cerci. But their soft bodies and underground lifestyle make them hard to fossilize, so their fossil record is extremely sparse. The oldest known fossil before this study came from the Early Cretaceous of Brazil.
Now, a team led by Prof. HUANG Diying at the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), has described a rare giant two-pronged bristletail from the Middle Jurassic Daohugou Biota (~ 165 myr) in Inner Mongolia. They named it Sinojapyx giganteus and established a new family, Sinojapygidae. The find offers fresh anatomical evidence for the group's evolutionary history and new clues for rethinking hexapod mouthpart evolution and Jurassic soil ecosystems. The results were published online in Proceedings of the Royal Society B.
1. Mouthparts: "Hidden" jaws may have evolved more than once
Hexapods include insects plus three early-diverging groups: proturans, springtails, and two-pronged bristletails. Traditionally, only insects were thought to have exposed mouthparts (ectognathy), while the other three had mouthparts hidden inside the head capsule (entognathy) — which is why they were once grouped as "Entognatha." But Sinojapyx giganteus, though clearly a two-pronged bristletail, has exposed mouthparts, especially visible mandibles. The team proposes that the common ancestor of all hexapods had exposed mouthparts, and that the "hidden" condition evolved independently in the three non-insect groups rather than from a single shared origin.+
2. Pincer-like cerci: a snapshot of evolution in progress
One of the best-known groups of two-pronged bristletails, the superfamily Japygoidea, is famous for its hard, pincer-like tail cerci, usually used for hunting and defense. Evolutionary analysis places Sinojapyx giganteus on the stem lineage of living Japygoidea. Unlike modern forms with highly specialized, tooth-bearing pincers and tightly fused abdominal segments, this Jurassic giant had symmetric pincers with smooth inner edges and an abdomen that was neither shortened nor heavily armored. This mix of features suggests the fossil captures a transitional stage, cerci shifting from sensory organs into efficient hunting weapons, and points to an arms race between predator and prey lasting hundreds of millions of years.
3. Over 5 cm long: a top predator in the Jurassic underground
Living two-pronged bristletails are usually tiny (mostly under 2 cm) and hide deep in the soil. Sinojapyx giganteus was over 5 cm long, larger than almost all living species, making it the oldest confirmed and largest two-pronged bristletail fossil known. The team notes it had very strong mandibles with sharply curved teeth and thick, robust pincers. In the warm, humid Daohugou forest soil 165 million years ago, this giant likely played a role similar to modern centipedes or scorpions — lurking in leaf litter and soil cracks, ambushing small invertebrates with its powerful pincers and jaws, sitting at the top of the Jurassic soil food web.
Notably, although the Daohugou Biota has yielded hundreds of thousands of insect fossils, no two-pronged bristletail had ever been found there. The specimen was collected 20 years ago, and after decades of fieldwork and screening hundreds of thousands of specimens, the team found just this one. The study is part of the institute's ongoing research on the origin and evolution of modern ecosystems; the team has previously reported the earliest fleas, webspinners, and gladiators from Daohugou. Researchers from the University of Valencia, Spain, contributed to the work. The study was supported by the National Key Research and Development Programme of China.
Reference: Wang Y, Cai C, Sánchez-García A, Sendra A, Huang D. 2026. A giant Jurassic hunter: the earliest dipluran and its implications for hexapod body pattern evolution. Proc. R. Soc. B 293: 20261207. https://doi.org/10.1098/rspb.2026.1207.
Fig.1 General morphology of Sinojapyx giganteus
Fig.2 Holotype details of Sinojapyx giganteus and comparison with extant taxa
Fig.3 Phylogeny and evolutionary framework of Diplura
Fig.4 Palaeoecological reconstruction of Sinojapyx giganteus
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