Эрдэмтэд нейтроны шинжилгээний тусламжтайгаар овираптор үлэг гүрвэлийн үр хөврөлүүд харилцан адилгүй хурдаар хөгжиж байсныг тогтоов.
Боннын их сургууль, Тайвань, Швейцарийн судлаачид болон Garching дахь Heinz Maier-Leibnitz Zentrum (MLZ)-ийн эрдэмтэд Хятадын Жянши мужийн Ганьжоу сав газраас олдсон, 67 сая жилийн настай овираптор төрлийн үлэг гүрвэлийн гурван өндгийг судалжээ. Эдгээр өндөг нэг дор, нэг чулуулагт бэхлэгдсэн байдалтай олдсон нь судлаачдад тэдгээрийг нэг үүрэнд хамаарах эсэхийг тодорхойлох боломж олгосон байна. Өмнө нь ийм олдворуудыг байгалийн нөхцөлөөс нь салгаж авдаг байсан тул нэг үүрнийх эсэхийг тогтооход хүндрэлтэй байжээ.
Судлаачид өндөгний дотоод бүтцийг нарийвчлан харахын тулд рентген томографийн оронд нейтроны үүсгүүр ашигласан байна. Нейтроны нэвтрэх чадвар өндөр тул чулуулгийн доторх үр хөврөлийн ясны бүтэц, хөгжлийн үе шатыг тодорхой дүрслэх боломжтой болжээ. Шинжилгээгээр ясны урт, тэдгээрийн хоорондын холбоос, өндөгний хальсны зузааныг харьцуулан үр хөврөл бүрийн хөгжлийн түвшинг үнэлсэн байна.
Судалгааны үр дүнгээс үзэхэд, нэг өндөг нь бусад хоёр өндгөөсөө түрүүлж гарсан байх магадлалтай бөгөөд хос өндөгний үр хөврөлүүд хүртэл харилцан адилгүй хөгжилтэй байжээ. Энэхүү олдвор нь овираптор үлэг гүрвэлийн үр төл бүгд нэгэн зэрэг хатдаггүй, харин орчин үеийн шувуудын адил ялгаатай хугацаанд хатдаг байсныг харуулж байна. Энэхүү дүгнэлт нь үр төл нь нэгэн зэрэг гардаг матрын төрлийн амьтдын нөхөн үржихүйн стратегиас ялгаатай болохыг илтгэж байгаа юм.
Integrative Organismal Biology сэтгүүлд хэвлэгдсэн энэхүү судалгаа нь чулуужсан олдворуудыг нейтроны тусламжтайгаар судлах нь шинжлэх ухаанд шинэ мэдлэг нэмэрлэх боломжтойг нотоллоо. Судлаачдын үзэж байгаагаар, үр хөврөл хөгжлийнхөө явцад хальсан дахь кальцийг өөрийн ясандаа шингээдэг тул хальс нимгэрэх явц нь хөгжлийн түвшинг илэрхийлэх гол үзүүлэлт болдог байна.
Дэлгэрэнгүйг эх сурвалжаас харах
↓Эх сурвалжийг нээх ↓
Three fossilized eggs from China have given paleontologists a rare glimpse of dinosaur reproduction. Using a neutron source, researchers found that oviraptorid embryos developed at different speeds, which suggests the chicks did not all hatch together.
Oviraptorids were two-legged dinosaurs that lived in Central Asia during the Upper Cretaceous, from 88 to 66 million years ago. Until now, researchers had assumed their reproductive biology sat somewhere between that of modern crocodiles and birds. Crocodiles bury their eggs, and the young hatch at the same time, while birds often hatch at different times in the nest.
A team from the University of Bonn, working with scientists from Taiwan, Switzerland and the Heinz Maier-Leibnitz Zentrum (MLZ) in Garching, set out to see how differently the embryos in three oviraptorid eggs had progressed.
A Clutch Found Together
The remains were about 67 million years old and came from the Ganzhou Basin in Jiangxi Province, China. What set them apart was that they were found together. According to Thomas Engler of the University of Bonn’s Institute for Geosciences, oviraptorid eggs turn up fairly often in Central Asia, but most are removed from the context of their discovery. Once that happens, it is frequently impossible to tell whether the fossil specimens came from a single clutch.
Here, a pair of eggs and another one were embedded together in one block of rock. Dr. Tzu-Ruei Yang, who found them during an excavation near the city of Ganzhou, concluded that a female oviraptorid had laid the 7-inch (18 cm) eggs almost at the same time.
Seeing Through Stone
Knowing they belonged together was one thing; looking inside them was another. The Bonn institute’s own X-ray microcomputer tomograph could not tell the bones apart from the surrounding rock, Engler says. So the team took the eggs to the research neutron source of the Technical University of Munich at the MLZ. Dr. Malgorzata Makowska, who was in charge of measurements and analyses at the MLZ and now carries out research at the Swiss neutron source PSI, says that:
“The high penetration depth of the neutrons at the NECTAR and ANTARES facilities made it possible to visualize the internal structures.”
Decoding the Ancient Remains
Working out how far each embryo had progressed inside its egg came down to a handful of clues. Bone length, for one, plays an important role here:
“The embryo with comparatively longer bones is more developed,” explains Yang. Another is how far the bones are connected to each other, since a more strongly connected skeleton suggests a higher developmental stage.
On that basis, the length and position of the bones led the researchers to conclude that the single egg was laid earlier than the pair. The two eggs of the pair were also at different developmental stages.
Thin sections confirmed these results, published in the journal Integrative Organismal Biology. The researchers used them to measure eggshell thickness, because a developing embryo absorbs part of the shell for the calcium its growing skeleton needs. As reported by the team, the more material removed from the shell, the more advanced the embryo.
From these indications, the scientists concluded that oviraptorid reproductive biology resembled that of modern birds, whose chicks hatch at different times. The findings argue against the strategy of crocodiles or turtles, where all the young emerge together. Engler adds that:
“Furthermore, the study shows that exploring fossils with neutrons yields novel scientific results.”
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