China News Service, Beijing, May 1 (Reporter Sun Zifa) The early evolution of mammalian auditory organs, including humans, has always attracted the attention of the paleontological community.
Among them, McBride's cartilage, which plays an important role in the evolution of mammals, still has many unsolved mysteries, and we look forward to more fossil discovery research to solve it.
"Nine Buddha Hall Chuan Kui Beast" positive specimen.
Photo by China News Agency reporter Sun Zifa
120-million-year-old fossils of new species of early true mammals discovered
The team of Wang Yuanqing, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences (Institute of Paleoanthropology, Chinese Academy of Sciences), together with Peking University Stomatological Hospital and colleagues in the United States, recently discovered an early true beast about 120 million years ago in the fossil research of the Jehol Biota in Liaoning, China. A new species, named "Nine Buddha Hall Chuan Kui Beast".
The most important research result of this time is the discovery of the ossified McBurby cartilage preserved in Chuankui beast, which is slender and short, and is likely to lose substantial connection with the ossicles of the middle ear.
This is the first time that the existence of ossified McBurby cartilage has been discovered and confirmed in true mammals, which fills the gap in the evolution of ossified McBurby cartilage in early mammals, and also confirms that some adults of early mammals still retain relatively Degenerated ossified McFarland's cartilage.
Wang Haibing introduced the fossil discovery and research results of "Nine Buddha Hall Chuan Kui Beast".
Photo by China News Agency reporter Sun Zifa
This important fossil discovery and research paper on the evolution of early eutherians has recently been published in the international professional academic journal "Philosophical Transactions of the Royal Society B". Provide important evidence for the evolution of mammalian hearing organs.
The first author and corresponding author of the paper, associate researcher Wang Haibing of the Institute of Paleo-Spine of the Chinese Academy of Sciences, recently accepted an exclusive interview with a reporter from China News Agency in Beijing and said that true mammals are a branch of mammals, which includes all living placental mammals such as humans. and their closest relatives.
The name Chuankui beast is dedicated to Li Chuankui, a paleontologist at the Institute of Paleontology of the Chinese Academy of Sciences, to commemorate his contribution to the study of early mammal evolution.
On the right mandible of Chuankui beast, the yellow is the ossified McBurby cartilage, and the blue is the hyoid bone.
Photo courtesy of Wang Haibing
The evolution of hearing in Chuankui beast has the strongest hearing among contemporary mammals
After a long period of meticulous repair of the fossil specimens, high-precision computed tomography (CT) and comparative studies, the research team found that the morphology of the ossified McBride cartilage preserved in the Chuankui beast was similar to that of the roughly contemporaneous true tricuspids, It is the most degraded ossified McNair cartilage known among Mesozoic mammals.
Wang Haibing pointed out that this indicates that the middle ear of Chuankui beast is likely to be completely separated from the lower jaw, which represents the key node of the separation of the mammalian middle ear from the lower jaw, and reflects the gradual degeneration of the McBurby cartilage in mammals.
At the same time, the contact relationship between the ossified McFarland cartilage and the bones of the mandible and middle ear preserved in Chuankui beasts also provides a more precise reference standard for perfecting the definition of each evolutionary stage of the mammalian middle ear.
Through the high-precision scanning analysis of the fossils of Chuankui beasts, the inner ear morphology of the early Cretaceous true beasts was reconstructed for the first time.
Photo courtesy of Wang Haibing
He said that the research team also reconstructed the inner ear morphology of the early Cretaceous true beasts for the first time through high-precision scanning analysis of Chuankui beast fossils.
The inner ear of Chuankui beast is relatively intact, and its morphology is both primitive and progressive, filling the gap in the evolution of the inner ear of basal mammals and true mammals in the Late Cretaceous.
Among them, the curling degree of the snail of Chuankui beast is close to 360 degrees, which is higher than that of other mammals of the same period, and is close to most of the true mammals of the Late Cretaceous, which also means that the evolution of the ear of Chuankui beast has already evolved in the same generation. Animals have the strongest hearing, so they can better prey and avoid danger.
Chukui beast is a key node in the evolution of mammalian middle ear detachment from mandible
With regard to McBride's cartilage, Wang Haibing said that McBerlin's cartilage is ubiquitous during the development of vertebrates. Although its morphology and function are different in different groups, the ossification of McBurney's cartilage in adults has so far only been reported in fossils. found in mammals.
Ecological restoration map based on the fossil specimen of "Nine Buddha Hall Chuan Kui Beast".
Photo by Chen Yu
Embryonic development and fossil evidence suggest that McBurby's cartilage played an important role in mammalian evolution: during the evolution of the middle ear ossicles that separated from the mandible, McBurby's cartilage supported and stabilized the ossicles until the middle ear was complete Separated from the mandible and stabilized at the base of the skull; the connection between McBurby's cartilage and the mandible and middle ear skeleton is the core element to define the evolutionary stages of the mammalian middle ear, and it is also an important information to reflect the different evolutionary stages of early mammals.
At present, paleontologists have found ossified McBurby cartilage in some primitive mammals of the Jehol biota (such as true tricuspids, Zhang and beasts), which are closely connected with the middle ear auditory ossicles, indicating that their middle ear The ear is in the evolutionary stage of the transitional middle ear.
This fossil study shows that in the evolution of mammals, the 120-million-year-old Hereditary beast was a key node in the separation of the middle ear from the lower jaw.
Wang Haibing believes that, as one of the most important structures in the early evolution of mammals, the palaeontological community still has limited understanding of its evolution process. Degeneration mechanism of cartilage and other issues.
He looks forward to more relevant fossil discoveries in the future and further in-depth research.
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