Эрдэмтэд Хятадын өмнөд хэсгээс олдсон 37 зүйлийн 200 орчим эртний хөхтөн амьтны шүдний чулуужсан олдворт шинжилгээ хийж, тэдний хувьслын явцыг тодрууллаа.
Судалгааны баг өндөр нарийвчлалтай 3D загварчлалын тусламжтайгаар Палеоцений эрин буюу үлэг гүрвэлүүд мөхсөнөөс хойших эхний 10 сая жилийн хугацаанд хөхтөн амьтдын шүд хэрхэн өөрчлөгдсөнийг судалжээ. Үр дүнгээс үзэхэд, хөхтөн амьтад идэш тэжээлийн онцлогт тохирсон нарийн бүтэцтэй шүд хөгжүүлэхийн өмнө эхлээд том хэмжээтэй, энгийн хэлбэрийн шүдтэй болсон байна. Энэхүү үйл явцыг судлаачид “хүч чадал нь хазалтаас түрүүлсэн” хэмээн тодорхойлжээ.
Хятадын Шинжлэх ухааны академийн судлаач Цянь Лигийн тэмдэглэснээр, шүд нь хүрээлэн буй орчинтой шууд харьцдаг эрхтэн тул тэдгээрийн бүтэц нь тухайн амьтны идэш тэжээл болон экологийн нөхцөлийг тодорхойлоход чухал ач холбогдолтой аж. Мөн тухайн бүс нутагт хуурайшилт тэсвэрлэх чадвартай ургамал олшрохын хэрээр хөхтөн амьтдын шүдний хэлбэр өөрчлөгдөж, илүү төвөгтэй, муруй бүтэцтэй болсон нь байгаль орчны өөрчлөлт хувьсалд хэрхэн нөлөөлснийг харуулж байна.
Калифорнийн их сургуулийн (UC Berkeley) дэд профессор Жэк Цэнгийн удирдсан энэхүү судалгаа нь хөхтөн амьтдын хувьслын эхэн үеийн мэдээлэл Хойд Америкаас гадна бусад бүс нутагт хэрхэн хомс байдгийг онцоллоо. Дэлхий даяар олдсон тухайн үеийн чулуужсан олдворуудын дөнгөж 3 хувь нь Ази тивд хамаардаг байна. Энэхүү нээлт нь Хойд Америк болон Европоос өмнө нь ажиглагдаж байсан хувьслын ижил хэв шинж Ази тивд ч мөн адил үйлчилж байсныг баталж байгаа юм.
Дэлгэрэнгүйг эх сурвалжаас харах
↓Эх сурвалжийг нээх ↓
A collection of fossil teeth from southern China is shedding new light on one of the biggest turning points in Earth’s history. By analyzing 200 teeth from 37 early mammal species, researchers found that mammals evolved larger teeth before developing the specialized features that later helped them diversify into new diets.
When the dinosaurs vanished 66 million years ago, mammals suddenly found themselves in a world full of new opportunities. The first few million years after that mass extinction marked the beginning of the Age of Mammals, yet scientists still have relatively little fossil evidence from that period, particularly outside North America.
A study published in eLife helps fill part of that gap. Researchers examined fossils recovered from the Nanxiong, Qianshan and Chijiang basins in southern China, all dating to the Paleocene Epoch; the first 10 million years after the end-Cretaceous extinction.
Bigger Teeth Came First
Rather than evolving specialized teeth right away, early mammals appear to have taken a more gradual path. Using high-resolution 3D models, the researchers found that the earliest placental mammals first developed relatively large teeth that were simple in shape and showed little variation.
More specialized features appeared only later, allowing the animals to process a wider variety of foods as they spread into new ecological niches.
The researchers describe this pattern as “brawn before bite.” Instead of becoming dietary specialists immediately after the extinction event, mammals first increased the size of their teeth before refining their function over the following millions of years.
“The fact that teeth interact directly with the environment through biting and chewing behaviours makes them crucial in helping us identify potential links between their structure and ecological context,” co-author Qian Li of the Chinese Academy of Sciences said in a statement.
A Rare Look at Asia’s Early Mammals
The findings reveal how much remains unknown about the earliest stages of mammal evolution outside North America. Lead author Jack Tseng, an associate professor at the University of California, Berkeley, said fossil records from the first 10 million years of the Age of Mammals remain heavily concentrated in North America. Only 3% of known fossil sites from that period are located in Asia.
How Environment Shaped Teeth?
The changing teeth tell only part of the story. The researchers also noticed that dental evolution closely matched changes taking place in the surrounding environment. As drought-tolerant plants became more common across southern China, mammal teeth grew more complex and more curved. Co-author Suyin Ting said that:
“As ecosystems recovered and transformed following the end-Cretaceous period, so did tooth shape and function, which indicates changing evolutionary pressures and ecological opportunities.”
The same “brawn before bite” pattern has already been identified in ancient mammals from North America and Europe, suggesting this sequence was not unique to Asia.
“Our work provides initial insights into the changes that occurred in placental mammals outside of North America after the end-Cretaceous Period, and unearths opportunities for further research to explore some of these associations in more detail,” said Tseng, adding that: “We hope the insights will be useful for developing predictive models and conservation strategies aimed at understanding how modern animals could respond to biodiversity crises in future.”
Enjoyed this article? Subscribe to our free newsletter for engaging stories, exclusive content, and the latest news.
