Палеонтологчид Хятадын нутгаас олдсон үлэг гүрвэлийн өндөгний бүрхүүлийн бүтцэд шинжилгээ хийж, шинэ зүйлийн ангилал тогтоон, эртний амьтдын өсөлт хөгжлийн талаарх мэдээллийг баяжуулжээ.
Хятадын Аньхуй мужийн Цяньшань сав газраас олдсон ойролцоогоор 13 сантиметр диаметртэй хоёр өндөгний дотроос ямар нэгэн яс, шүд, үр хөврөлийн ул мөр олдсонгүй. Үүний оронд өндөгний хальс гэмтсэний улмаас дотогш нэвтэрсэн эрдэс бодисоор баялаг гүний усны нөлөөгөөр үүссэн цайвар өнгийн кальцитын талстууд илэрчээ. Судлаачид өндөгний хальсны бичил бүтцийг нарийвчлан судалсны дүнд үүнийг Shixingoolithus qianshanensis хэмээх шинэ зүйл болохыг тогтоож, Stalicoolithidae овогт хамааруулсан байна.
Үүний зэрэгцээ Цзянси мужийн Ганьжоу сав газраас олдсон өөр нэгэн бүлэг өндөгнөөс хадрозавроид үлэг гүрвэлийн үр хөврөлүүд илэрсэн нь палеонтологийн ховор олдвор боллоо. Ойролцоогоор 660 миллилитрийн эзэлхүүнтэй эдгээр өндөгний доторх үр хөврөлийн яс бүрэн хөгжөөгүй байсан бөгөөд нэгэн сорьцын дунд чөмөгний яс нь ердөө 26 миллиметр урттай байжээ.
Эдгээр олдворууд нь нугасан хошуут үлэг гүрвэлүүдийн өсөлт хөгжлийн онцлогийг ойлгоход чухал ач холбогдолтой юм. Судлаачдын үзэж буйгаар, жижиг хэмжээтэй өндөгнүүд нь том өндөгтэй төрлүүдээс ялгаатай хувьслын шинж чанартай байж болох талтай. Гэвч Цзянсийн олдворын насжилтыг тогтоох тал дээр зарим эрдэмтэд маргаантай байр суурьтай байгаа бөгөөд одоогоор 71.4-65.0 сая жилийн өмнөх үед хамаарна гэсэн таамаглал илүү хүлээн зөвшөөрөгдөөд байна.
Дэлгэрэнгүйг эх сурвалжаас харах
↓Эх сурвалжийг нээх ↓
Open up a dinosaur egg and you might expect to see bones. In one fossil from eastern China paleontologists found crystals instead.
The eggs are two nearly spherical specimens that were recovered from the Qianshan Basin in Anhui Province. There are no teeth, no bones, no recognizable embryo remains inside. But a damaged section of shell instead exposes clusters of pale calcite crystals that formed after burial when mineral-rich groundwater seeped into the hollow interior.
The eggs each measure approximately 13 centimeters across. They have an obvious shape, but the real evidence was hidden in the shell itself in microscopic structural
Shell Structure, Not Contents
Those shell details led researchers to identify a previously unknown fossil egg species, Shixingoolithus qianshanensis, described in a study published in the Journal of Palaeogeography.
Shixingoolithus qianshanensis is the first report of this oogenus (egg genus) discovered in the Qianshan Basin.
Although an embryo is needed for the taxonomic classification of an egg-fossil, scientists are able to separate eggs based on their shapes, sizes and the microscopic structure of their shells. Therefore, a parallel nomenclature system has been developed which includes oofamily, oogenus and oospecies categories in addition to others.
Scientists classified these eggs into the family Stalicoolithidae due to their relatively large size, tight spacing of individual egg-shell units, similar structural patterns at the microscopic level and unique internal-surface structures. There was no single feature that provided conclusive evidence regarding their identity. Rather, it was the combination of characteristics that were used to determine the scientific classification.
Using methods such as comparison of the total dimensions of the eggs with the relative density and pattern of the microscopic structural components present in each egg-shell, scientists determined that the new species name would be assigned to a type of fossilized egg rather than to a specific species of dinosaur.
Additionally, the research team demonstrated through the discovery of dinosaur related fossils in the Qianshan Basin that they represent the first evidence of dinosaurs found in this basin area. Furthermore, they documented paleontologic evidence that can aid in classifying and correlating Upper Cretaceous to lower Paleogene stratigraphy located in Anhui province.
A Clutch From Jiangxi With Embryos Inside
A separate Chinese discovery, from another province and another geological formation, preserved something much rarer.
Construction blasting in the Upper Cretaceous red beds of the Ganzhou Basin in Jiangxi Province exposed a clutch of subspherical dinosaur eggs, and at least two held identifiable hadrosauroid embryos, described for the first time in a study published in BMC Ecology and Evolution.
Assigned to Spheroolithidae, the eggs are thin-walled and small, with an estimated volume of roughly 660 milliliters.
Field records noted at least 13 eggs in the clutch at the time of excavation.
Near the rear of the skull, the shape of the embryonic squamosal resembles that seen in the Late Cretaceous hadrosauroids Levnesovia transoxiana, Tanius sinensis, and Nanningosaurus dashiensis. The resemblance points to possible affinities, though the researchers treated those comparisons as tentative rather than definitive.
The embryos were nowhere near fully developed when they died. In one of the better-preserved specimens, the femur is just 26 millimeters long, and the skeleton occupies only about 40 percent of the egg’s interior by area, leaving it several developmental stages short of hatching.
Just 26 millimeters.
What the Size of the Eggs Reveals
The Jiangxi embryos feed into a longstanding question about how duck-billed dinosaurs and their relatives grew.
Their small egg size, similar to those of Hadrosaurinae, indicates that the larger eggs and hatchlings typical of Lambeosaurinae, a separate hadrosaurid subfamily, are an evolutionarily derived trait rather than the ancestral condition. Lambeosaurine eggs can approach 4,000 milliliters in volume, roughly six times the size of the Jiangxi specimens.
The age of the Hekou Formation, where the Jiangxi eggs were found, remains unsettled. Some researchers have argued for a Coniacian-Santonian age, but a Maastrichtian age is more commonly accepted, based partly on palaeomagnetic studies that dated the host rock unit to between 71.4 and 65.0 million years ago.
The Anhui eggs offer no comparable glimpse of the animal that laid them.
What survives there is shell microstructure and the calcite crystals left behind by mineralizing groundwater. That was enough to establish Shixingoolithus qianshanensis as a species new to science, despite there being no trace of the creature inside.
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