China has discovered the most complete platypus embryos recorded so far

Fossil restoration of duck-billed dragon embryos. (Courtesy of the research group)

“Impebe” duck-billed dragon embryo. (Courtesy of the research group)

On May 11, scholars from the Yingliang Stone Natural History Museum in Fujian Province, China University of Geosciences (Beijing), the Natural Science Museum of Taiwan and the Canadian Museum of Natural History jointly published a paper describing two dinosaur embryos from the Cretaceous Estuary Formation in the Ganzhou Basin of Jiangxi Province, China, recording the most complete duck-billed dragon embryos recorded so far. The specimens are in the Yingliang Stone Natural History Museum in Fujian Province, which nicknames the collection “Ying Baby” and uses them to answer important questions about dinosaur development and reproduction. The paper was recently published in BMC Ecology and Evolution.

Around 2000, the chairman of Yingliang Group collected a batch of suspected egg fossils. Since 2015, during the preparation of the Yingliang Stone Natural History Museum in Fujian Province, the museum director Niu Kecheng has comprehensively sorted out the existing specimens in the warehouse and started to clean up some potential research objects, in the process, a number of embryos and specially preserved egg fossils were found. In 2019, the Xing Lida Research Group of China University of Geosciences (Beijing) cooperated with the Yingliang Stone Natural History Museum in Fujian Province to start a detailed study of this batch of specimens, and used technical means such as synchrotron radiation and MCT scanning to examine the specimens and achieved a series of results.

The duck-billed dragon embryo “Yingbeibei” published this time is native to the late Cretaceous strata in the Gannan region, dating from about 72 million to 66 million years ago. The egg in which the Abbe embryo is located is an ellipsoid with a length of about 9 cm in diameter, a volume of about 660 ml, and the embryonic part accounts for about 40% of the entire egg, the embryonic egg has a thin eggshell of about 0.4 mm thick, and its microscopic structure shows that it belongs to the round egg family.

Based on the unique shape of the skull, spine, and limb bones of the dinosaur embryos, it can be inferred that the fossil embryos contained in the eggs belong to the platypus. This is a large plant-eating dinosaur that lived at the end of the dinosaur era, and they all had a highly recognizable duck-like flat mouth. Platypus embryos are not the first to be discovered globally, but these new platypus embryos are by far the best preserved embryos of their kind.

However, it is difficult for scholars to know exactly which genus this group of embryos represents the duck-billed dragons; the identification characteristics of specific species often do not manifest themselves until later in life. However, the unique shape of the in situ scales preserved at the posterior edge of the upper part of the embryonic skull, the posterior projection is high and blunt, reminiscent of some platypus superfamily dinosaurs, such as Levonis, Tansaurus and Nanning, all from Asia, suggesting the possible affinity of the new specimen with these species.

The size of the egg and embryo fossils found this time is comparable to the more specific duck-billed dragons of the Upper Cretaceous of North America. These platypus have traditionally been divided into two groups: the subfamily Lysosaurus with a delicate hollow ridge crown on the skull, and the ctenophorae or duck-billed dragon subfamily without such crests.

In general, the duck-billed dragon subfamily produces much smaller eggs than the Lyceum subfamily (900 ml and 4000 ml, respectively), so the hatchings are also smaller. Not only that, but the young dragons of the duck-billed dragon subfamily are thought to be less developed than the subfamily Rydonosaurus, especially in the formation of limb bones.

That is to say, the young dragons of the duckbill subfamily are late-formed, and they do not fully grow up until they hatch for a long period of time before the limb bones fully grow. In contrast, the larger Lysaurus subfamily chicks are early-formed and can join the group soon after birth.

It is reported that this interesting difference for evolutionary biologists naturally raises a question about the ancestral traits of duck-billed dragons: Were the ancestors of duck-billed dragons late or early in the process of hatching? Among the embryonic eggs found this time, the eggs and embryos are very small, similar to the subfamily duckbill, which indicates that the small eggs and late-adult chicks are the original traits of the duck-billed dragons, while the larger eggs of the Lai family are derived from the early adult chicks, which is the most important scientific new knowledge told by the “Inbebe” dinosaur embryos. (Source: China Science Daily Cui Xueqin)

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