Two new Jurassic species — species similar to Morganucodontan Dianoconodon Yonggi and pseudotribosphenicshotelide Feredkodon Chowi — Provides important information about the evolutionary transition from temporomandibular joint bones to middle ear bones in early mammals.
Dianoconodon Yonggi. Image credit: Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences.
both Dianoconodon Yonggi and Feredkodon Chowi It lived in China more than 150 million years ago (Jurassic period).
type specimen of Feredkodon Chowi It was discovered in Dahugou, Ningchen Basin, Inner Mongolia Autonomous Region.
of Dianoconodon Yonggi The fossil was discovered in the Heiguopeng area of the Lufeng Formation in Yunnan Province.
The specimen exhibits remarkable physical features, suggesting that the function of the temporomandibular joint was gradually changing toward specialized hearing.
“The significance of this discovery is that both species have a mandibular middle ear, and the Morganucodontan-like species has a new postdentary bone structure,” researchers from Monash University and Museums Victoria said Professor Patricia Vickers Rich.
“Dianoconodon Yonggi The quadratus joint is losing its load-bearing function, Feredkodon Chowi It exhibits properties suitable for purely auditory functions. ”
This fossil provides important evidence of a transitional period in the evolution of the mammalian middle ear.
As the load-bearing capacity of the main joint of the jaw gradually decreases, the postdental bone separates from the dentition.
This discovery revises previous ideas about the natural state of the mammalian middle ear.
These will improve our understanding of mammalian development by answering questions about the evolution of the middle ear in mammalian relatives.
“Studying transitional periods in evolutionary history is extremely important,” Professor Vickersrich said.
“The fossils show gradual changes and demonstrate the complex adaptive processes that led to the sophisticated auditory systems seen in modern animals.”
The results also provide insight into how tissues, such as ossified tissue, change. Meckel cartilage It helped with the transition from jaw movement to hearing.
Paleontologists can track the steady evolution of the middle ear ossicles by studying features such as the medial displacement of the quadrate relative to the joint.
“Newly identified well-preserved fossils from the Jurassic period of China shed much light on how one of the most remarkable transitions in vertebrate history took place,” said Monash University and said Dr Thomas Rich of Museums Victoria.
“So many of the bones in the reptile's lower jaw changed into the small bones in the mammal's middle ear.”
of study Published in today's diary Nature.
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F. Mao other. Fossils document the evolutionary transformation of the temporomandibular joint into the middle ear of mammals. Nature, published online on April 3, 2024. doi: 10.1038/s41586-024-07235-0
Source: www.sci.news
