KUNMING, Nov. 17 (Xinhua) -- Chinese paleontologists have discovered what is potentially the earliest fossil evidence linking adult dinosaurs with nests.
They have reported that the eggshells may have been similar to leather, a finding that would deepen our understanding of dinosaur reproduction.
The study, published in National Science Review, said that fossils of an Early Jurassic dinosaur species had been found in a layer of purple, silty mudstone in Guizhou, southwest China. The find comprised five clutches of embryo-filled eggs and at least three adult skeletons that lived approximately 190 million years ago.
The specimens that are from a sauropodmorph family have been named Qianlong shouhu, literally meaning "a dragon in Guizhou that protects its embryos." Sauropodmorphs were a group of medium to large-sized, plant-eating, "lizard-hipped" dinosaurs with long necks and tails, and they were some of the largest animals to ever walk on the earth.
The research team included members from Yunnan University, China University of Geosciences in Wuhan, Chinese Academy of Sciences, Guizhou Provincial Museum and Pingba Institute of Cultural Relics Administration in Anshun. Together, they examined the eggshells using multiple techniques.
They found that Qianlong produced eggs that are relatively large, and have a relatively thick calcareous layer compared with other early-diverging sauropodmorph dinosaurs.
The preserved Qianlong egg clutches vary in size, with the smallest clutch containing three eggs and the largest containing 16, and most of the eggs would have been rounded to elliptical, according to the study.
Their analysis indicated that dinosaurs had eggs that were distinct from those of other reptilian groups, as they were moderately elongated and thin-shelled.
These Early Jurassic fossils provide strong evidence for the theory that the earliest dinosaur eggs would have had leathery shells. To test this hypothesis, the paleontologists assembled an egg database from 210 fossilized and extant reptilian species -- the largest database of reptile eggs to date and represent all major reptilian clades.
The similar ossification levels of the Qianlong embryos suggest Qianlong practiced synchronous breeding and hatching strategy at the unearthed colonial nesting site.
"Like modern turtles, they might have come out of their shells at the same time -- a strategy that would have aided their escape from predators," said Han Fenglu, the paper's first author, who works at the China University of Geosciences in Wuhan.
Also, the adult-embryo limb ratios indicate that a 6-meter-long adult individual of Qianlong would have walked on its hind limbs alone, but young individual would likely have used all four.
The team's findings are significant to the understanding of the reproductive biology of reptiles, and particularly that of dinosaurs, according to the researchers.
Southwest China is home to a rich collection of early dinosaur fossils. The skeleton of Lufengosaurus huenei, a herbivorous dinosaur that existed in the Early Jurassic period, was excavated in southwest China in 1938. It initialized China's systematic and professional dinosaur research and led to the discovery of one of the world's largest and most significant dinosaur fossil sites spanning the early and middle epochs of the Jurassic period. ■