Хятадаас олдсон 245 сая жилийн өстей эртний далайн хэвлэлийн чулуужсан үлдэгдлээс хоол боловсруулах систем нь бүтнээрээ шахам хадгалагдан үлджээ.
Хятад, Европ, АНУ-ын эрдэмтэд хамтран судласан Science Advances сэтгүүлд нийтлэгдсэн уг судалгаа нь Триасын гаTварын үед хамаарах, урт хүзүүтэй, жижиг биетэй Austronaga minuta нэртэй амьтанд төвлөрчээ. Ойролцоогоор 60 сантиметр урттай энэхүү хэвлэлийн скелет бараг бүрэн бүтэн олдсоноос гадна сүүл нь усанд сэлэх хөдөлгөөнийг үүсгэж, уртассан сэлүүр хэлбэртэй урд мөчүүд нь чиглүүлэгч болон тогтворжуулагчийн үүрэг гүйцэтгэж байсныг тогтоожээ. Их биеийн хэлбэр нь ихтиозавр, мозазавр зэрэг далайн хэвлэхүүнтэй төстэй боловч Austronaga нь үлэг гүрвэл, матар үүсэн хөгжихөд хүргэсэн эртний архозавруудын бүлэгтэй илүү ойр төрөл болох нь тогтоогджээ.
Судлаачид хэт ягаан туяаны гэрэл зураг болон массын спектрометрийн аргыг ашиглан хавирганы зав зай дахь хар өнгийн хэсгээс уут хэлбэртэй ходоод, гемоглобины ул мөр үлдсэн элэг, нарийн болон бүдүүн гэдэсний хоолой зэрэг дотоод эрхтнүүдийг илрүүлсэн байна. Уг амьтны биеийн галбир усанд амьдрахад сайн зохицсон байсан хэдий ч хоол боловсруулах систем нь харьцангуй энгийн бүтцтэй болох нь тогтоогджээ. Энэхүү олдвор нь хэвлэхүүний хоол боловсруулах систем бараг бүтнээрээ олдсон хамгийн эртний тохиолдол болж байна.
Өнөөгийн шувууд болон матар хоёр тасалгаат ходоодтой байдаг бол Austronaga ганцхан ходоодны тасалгаатай байснаараа эртний архозавруудын хоол боловсруулах систем анх илүү энгийн бүтцтэй байж, илүү мэргэжсэн хоёр хэсэгтэй бүтэц нь хожим үүссэн болохыг харуулж байна. Мөн уг амьтан нь орчин үеийн загас Iдэг хэвлэхүүнтэй төстэй богино, энгийн хоол боловсруулах замтай байжээ. Уг олдвор Бээжин хотод хадгалагдаж байгаа бөгөөд Триасын тэнгист амьдарч байсан хэвлэхүүний олон янз байдал болон хувьслын түүхийг судлахад чухал хувь нэмэр оруулж байна.
Дэлгэрэнгүйг эх сурвалжаас харах
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A fossil discovered in China has given scientists a rare look inside a marine reptile that lived about 245 million years ago. Alongside an almost complete skeleton, the specimen preserves much of its digestive system, making it the oldest known reptile fossil with a largely intact digestive tract.
The discovery offers an unusual opportunity to study both the external anatomy and internal organs of an early marine reptile. The study, published in Science Advances, focuses on Austronaga minuta, a small long-necked species whose exceptional preservation has revealed details that are almost never seen in fossils from the Triassic Period.
The research brought together scientists from China, Europe, and the United States, including paleontologist Dr. Stephan Spiekman of the State Museum of Natural History Stuttgart and the University of Hohenheim. Researchers say the fossil not only documents the anatomy of a single animal but also helps clarify how some reptiles adapted to life in the oceans after evolving on land.
An Early Marine Reptile With Surprising Adaptations
The fossil of Austronaga minuta is nearly complete and measures about 60 centimeters (24 inches) in length. Although relatively small, the reptile had an unusually long neck and tail, giving it a distinctive appearance among marine reptiles known from the Triassic.
Researchers found that the animal was already well suited to an aquatic lifestyle. Its long tail generated propulsion through the water, while elongated, fin-like forelimbs provided steering and stability. Its hind limbs had become greatly reduced and contributed little to swimming.
One of the most unexpected findings concerns its evolutionary relationships. While its body shape resembles that of marine reptiles such as ichthyosaurs and mosasaurs, Austronaga belongs to a different branch of the reptile family tree. It is closely related to early archosaurs, the group that later gave rise to dinosaurs and crocodiles. Dr. Stephan Spiekman said scientists had generally believed early archosaurs showed only limited adaptation to marine environments. He explained that:
“The discovery of Austronaga shows that early representatives of this lineage had already developed complex adaptations to life in the oceans, comparable to those of other, better-known groups of fossil marine reptiles.”
Ancient Organs Survived Inside the Fossil
As mentioned in the study, the most remarkable feature of the specimen was hidden inside its rib cage. A dark area between the ribs turned out to be the remains of a largely preserved digestive system after scientists examined it using modern analytical techniques.
Using UV-light photography and mass spectrometry, the research team identified several internal organs, including a large sac-like stomach, a liver that still preserved traces of hemoglobin, and a long digestive tube corresponding to the small and large intestines.
Lead author Dr. Wei Wang of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing said the reptile’s internal anatomy appeared much less specialized than its skeleton. While its body had clearly adapted to efficient swimming, its digestive system remained relatively simple in structure.
“The overall arrangement shows that the digestive system of Austronaga was relatively simple in structure. This fossil is the oldest known example of a largely complete digestive system in a reptile,” he said.
A Gut That Changed Evolution
The preserved organs also offer new clues about the evolution of archosaurs. Today, both birds and crocodiles possess a stomach divided into two chambers. Austronaga, by contrast, had only a single stomach chamber.
Nick Fraser of National Museums Scotland said this indicates that the earliest archosaurs likely began with a much simpler stomach, with the more specialized two-part structure evolving later.
He also noted that Austronaga had a short, uncomplicated digestive tract similar to those found in modern fish-eating reptiles. Together with the preserved skeleton, these internal organs provide one of the clearest pictures yet of the biology of an early marine reptile.
The fossil is now housed in Beijing, where it supports ongoing research into the diversity of reptiles that inhabited the Triassic seas. The team hopes future discoveries will continue to improve understanding of the evolutionary history of marine reptiles and their terrestrial relatives.
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