如今威风凛凛的大白鲨,它的祖先其实……不说也罢

时间:2019-07-16 来源:www.destinotrip.com

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Palaeocarcharias stromeri化石。

鲨鱼头上有许多人们都熟悉的鲨鱼,如灰鲨(世界上最快的鲨鱼),大白鲨,以及世界上最大的掠食性鲨鱼齿鲨,曾经在世界各地旅行过。最近,奥地利维也纳大学的Patrick L. Jambura国际研究小组在这些顶级食肉动物的牙齿中发现了一个独特的特征,这使科学家能够将这些鲨鱼的祖先追溯到中侏罗世(165mya)。一种小型底栖鲨鱼,其结果最近发表在期刊《科学报告》上。

与人类相似,鲨鱼牙齿由两个矿化结构组成。由高矿化组织组成的硬壳(人类是珐琅,鲨鱼是牙釉质)和牙本质核心。根据牙本质的结构,我们可以将它分为两种类型:口腔正畸和骨齿。

口腔正畸学具有非常紧凑的外观,类似于我们在人类牙齿中发现的牙本质。在鲨鱼的牙齿中,正畸牙齿仅限于牙冠。相反,骨牙的结构更像海绵,通常在牙根中,其用于将牙齿固定在下颌中。然而,也可以在某些物种的冠部中找到用于支撑正畸牙齿的骨牙本质。

Patrick L. Jambura及其同事利用高分辨率CT扫描技术检查了大白鲨及其相关物种的牙齿组成。在这些动物的牙齿中发现了一种独特的现象:牙齿根部的骨骼延伸。转到牙冠并完全取代口腔正畸。这在任何其他鲨鱼中都没有发生过,它们在某种程度上都有正面的牙齿。

Another species studied is Palaeocarcharias stromeri, an extinct ancient shark that lived in the Middle Jurassic (165 million years ago) and has little in common with today's rat sharks. Palaeocarcharias stromeri is small, no more than one meter in length and inhabits the bottom of the ocean, and may prey on small fish in shallow water. To this day, its taxonomic status is still a mystery to scientists because its shape is like a shark but a fang-like tooth is similar to a rat shark. By studying the microstructure of the teeth, the researchers found that it has the above-mentioned tooth structure that only exists in the great white shark and its close relatives, which strongly suggests that this humble little shark evolved to produce the most iconic shark. One of the pedigrees.

“Almost all vertebrates, from fish to mammals, including all modern sharks except the sharks of the sharks, have orthodontics. The unique tooth structure found in ancient shark fossils strongly suggests that we found The oldest ancestors known to the great white shark, it also shows that even the fascinating giant sharks are not surprising at first,” said Patrick L. Jambura.

Original compilation: Max Review: Ximo Editor: Zhang Meng

Journal Source:《科学报告》

Journal number: 2045-2322

Original link:https://phys.org/news/2019-07-tracking-evolution-teeth-small-fry-ancestor.html

Chinese content is for reference only, all content is subject to the original English version. If reproduced, please indicate source.

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