Two Back-to-Back Nature Papers Reveal the Oldest Known Bony Fish and the Silurian's Apex Predator, Pushing Vertebrate Origins Back 10 Million Years
Paleontologists report paired discoveries from China that rewrite the early chapter of bony fish evolution and, by extension, the evolutionary lineage leading to all living vertebrates including humans.
Overview
Two simultaneous cover stories published in Nature on 4 March 2026 have transformed paleontologists’ understanding of the earliest chapter in vertebrate evolution. A research team led by Academician Zhu Min, Professor Lu Jing, and Professor Zhu You’an of the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) at the Chinese Academy of Sciences describes two ancient bony fish from southwest China — one the oldest known bony fish ever found with its body intact, the other the Silurian Period’s largest apex predator — whose combined anatomy pushes the origin of core osteichthyan traits back by roughly 10 million years.
The Oldest Bony Fish: Eosteus chongqingensis
The first paper centers on Eosteus chongqingensis, a creature that lived approximately 436 million years ago during the Early Silurian and was recovered from the Huixingshao Formation in Xiushan, Chongqing Municipality. As reported by phys.org, the specimen is exceptionally complete — head to tail — measuring just 3 centimetres in total length, making it the world’s oldest articulated bony fish fossil.
Despite its diminutive size, Eosteus displays a mosaic of primitive and derived traits that place it squarely in the bony fish stem group, before the evolutionary split between ray-finned fish (Actinopterygii) and lobe-finned fish (Sarcopterygii). The latter lineage ultimately gave rise to tetrapods — the land-walking vertebrates that include reptiles, birds, and mammals.
A streamlined, fusiform body outline, a single dorsal fin, and specialized caudal fulcra scales are visible in the specimen. Notably, it lacks lepidotrichia (the bony fin rays typical of later bony fish) but retains serial median dorsal plates and pectoral fin spines previously considered hallmarks of early cartilaginous fish and certain placoderms. The presence of these features in such an early osteichthyan demonstrates that the core suite of bony fish characteristics emerged at least 10 million years earlier than previously thought.
The Silurian Apex Predator: Megamastax amblyodus
The companion paper, co-led by Brian Choo of Flinders University and Jing Lu of the Chinese Academy of Sciences, reinterprets Megamastax amblyodus, a Silurian predator known since 2014 from fragmentary remains. A newly discovered complete skull from the Kuanti Formation in Yunnan Province, southern China, dating to approximately 425 million years ago, has revealed its anatomy in far greater detail, according to The Conversation.
With a jaw that measured 17 centimetres when complete, Megamastax would have stretched roughly one metre in length — making it the largest known jawed vertebrate of the Silurian Period and the world’s oldest documented vertebrate apex predator. The skull has upended assumptions about what early bony fish ate: rather than using simple crushing teeth, Megamastax possessed extraordinary bony tooth cushions — circular structures that slotted onto raised lumps on the palate, each capped with clusters of sharp, piercing fangs. The arrangement was suited for seizing soft-bodied prey rather than pulverizing hard-shelled organisms.
Like Eosteus, phylogenetic analyses place Megamastax in the bony fish stem group, making it, as the researchers describe it, a kind of evolutionary “great-uncle” of all living bony vertebrates, positioned just before the ray-finned / lobe-finned divergence.
Why Both Papers Matter Together
The two fossils are complementary in a precise scientific sense. Eosteus provides the earliest known complete body and fin architecture of an osteichthyan; Megamastax provides the highest-resolution cranial anatomy available from the Silurian. Together, as summarized by phys.org coverage of both studies, they allow researchers to reconstruct the ancestral morphology of all osteichthyans — a group that today encompasses approximately 30,000 species of ray-finned fish plus all lobe-finned fish and every tetrapod alive, humans included.
The paired discoveries resolve a long-standing gap in the fossil record. Until now, the earliest known bony fish were understood primarily from isolated scales and fragmentary bones; complete or near-complete articulated specimens were absent from the Early Silurian entirely. The Chongqing and Yunnan deposits have now provided the evidence needed to anchor calibration points in molecular clock analyses of vertebrate phylogeny and to test competing hypotheses about when bony fish body plans first cohered.
Broader Context
The findings arrive against a backdrop of sustained productivity in Chinese Silurian and Devonian paleontology. Over the past decade, research groups centered on IVPP have produced a series of high-profile discoveries — including early jawed fish from Chongqing that made global headlines in 2022 and 2023 — that have systematically pushed back the origins of major vertebrate groups. The dual March 2026 papers represent a continuation and deepening of that program, now extending the articulated bony fish record into the earliest Silurian and providing the first detailed look at what the apex predator of that ancient world actually looked like and how it fed.