A fossil discovery in southwestern China has brought to light the oldest known dinosaur embryos, dating back 190 million years. The remains show different stages of development and even contain traces of organic material, something rarely seen in fossils this old.
The embryos were found near Lufeng in Yunnan province and belong to Lufengosaurus, a long-necked sauropodomorph from the Early Jurassic. Most known dinosaur embryos come from the Cretaceous, so this find pushes the timeline much further back.
What makes this site stand out is the variety of specimens. Instead of a single nest frozen in time, researchers uncovered bones from several embryos at different stages.
A Fossil Site That Captures Multiple Stages Of Life
More than 200 bones were recovered, representing around 20 embryonic individuals. According to Dr Robert Reisz from the University of Toronto Mississauga, these bones likely came from several nests grouped together.
“We are opening a new window into the lives of dinosaurs. This is the first time we’ve been able to track the growth of embryonic dinosaurs as they developed. Our findings will have a major impact on our understanding of the biology of these animals.”
That kind of setup is rare. Most fossilized embryos are found in single nests, which only show one moment in development. As reported in Nature, the Lufeng site reads more like a timeline, with multiple stages of growth preserved in one place.
Organic material was discovered in embryonic bones unearthed in Lufeng, China. Credit: Robert R. Reisz & al
Scientists Spot Fast Growth in Egg
To understand how these embryos grew, scientists focused on the femur and they identified a striking growth pattern. The bone doubled in length from 12 to 24 millimeters during incubation. As explained in the study, that points to a fast growth rate inside the egg.
This finding indicates that these early dinosaurs moved before hatching, a behavior previously confirmed in modern birds but never directly demonstrated in dinosaurs. According to Dr Reisz :
“This suggests that dinosaurs, like modern birds, moved around inside their eggs,” he added that “it represents the first evidence of such movement in a dinosaur.”
A data snapshot highlighting key percentages and distribution patterns across multiple segments. Credit: Nature
Organic Material Preserved Against All Odds
Another surprising result came from the chemical analysis of the bones. Using targeted infrared spectroscopy, researchers detected traces consistent with collagen fibers, a protein normally found in bone. The team reported that finding this kind of material in fossils this old is extremely rare. These embryos are more than 100 million years older than other fossils where similar organic traces have been found.
“A find such as the Lufeng bonebed is extraordinarily rare in the fossil record, and is valuable for both its great age and the opportunity it offers to study dinosaur embryology. It greatly enhances our knowledge of how these remarkable animals from the beginning of the Age of Dinosaurs grew.”
Semi-transparent reconstruction of a dinosaur embryo inside its egg. Credit: D. Mazierski