英国伯明翰大学Richard P. Dearden等研究人员发现最古老的三维保存脊椎动物神经颅骨。这一研究成果于2023年9月20日在线发表在国际学术期刊《自然》上。

研究人员使用计算机断层扫描技术描述了奥陶纪干群有颌类的颅骨解剖结构：美国科罗拉多州哈丁砂岩中的Eriptychius americanus。Eriptychius的头部化石保留了一组对称的软骨，研究人员将其解释为眶前神经颅，包括侧面的眼眶、末端的口、嗅球和松果体。这表明，在最早的有颌类中，神经颅填充了真皮骨架和大脑之间的空间，就像在无颌类、骨甲鱼类和盾皮鱼类一样，而不像在圆口类中。然而，这些软骨并没有融合成一个单一的神经颅骨单元，这表明这是有颌类的一个衍生特征。Eriptychius填补了人们对有颌类头部演化在时间和系统发育上的一个重大空白，揭示了与之前描述的脊椎动物不同的神经颅解剖结构。

据介绍，神经颅是脊椎动物头部不可分割的一部分，其本身就是演化过程中的一大创新。然而，人们对神经颅的早期历史仍然知之甚少，现存的两个脊椎动物类群：有颌类（有颌脊椎动物）和圆口类（盲鳗和七鳃鳗）的神经颅形态差异很大。寒武纪脊椎动物的出现与保存下来的最早的三维脊椎动物神经颅之间相差1亿年，这进一步模糊了现代状态的起源。

附：英文原文

Title: The oldest three-dimensionally preserved vertebrate neurocranium

Author: Dearden, Richard P., Lanzetti, Agnese, Giles, Sam, Johanson, Zerina, Jones, Andy S., Lautenschlager, Stephan, Randle, Emma, Sansom, Ivan J.

Issue&Volume: 2023-09-20

Abstract: The neurocranium is an integral part of the vertebrate head, itself a major evolutionary innovation1,2. However, its early history remains poorly understood, with great dissimilarity in form between the two living vertebrate groups: gnathostomes (jawed vertebrates) and cyclostomes (hagfishes and lampreys)2,3. The 100Myr gap separating the Cambrian appearance of vertebrates4,5,6 from the earliest three-dimensionally preserved vertebrate neurocrania7 further obscures the origins of modern states. Here we use computed tomography to describe the cranial anatomy of an Ordovician stem-group gnathostome: Eriptychius americanus from the Harding Sandstone of Colorado, USA8. A fossilized head of Eriptychius preserves a symmetrical set of cartilages that we interpret as the preorbital neurocranium, enclosing the fronts of laterally placed orbits, terminally located mouth, olfactory bulbs and pineal organ. This suggests that, in the earliest gnathostomes, the neurocranium filled out the space between the dermal skeleton and brain, like in galeaspids, osteostracans and placoderms and unlike in cyclostomes2. However, these cartilages are not fused into a single neurocranial unit, suggesting that this is a derived gnathostome trait. Eriptychius fills a major temporal and phylogenetic gap in our understanding of the evolution of the gnathostome head, revealing a neurocranium with an anatomy unlike that of any previously described vertebrate.

DOI: 10.1038/s41586-023-06538-y

Source: https://www.nature.com/articles/s41586-023-06538-y