中国云南曲靖早泥盆世大眼小瓣鱼的三维形态数据

3D morphological data of Pauropetalichthys magnoculus from the Early Devonian of Qujing,Yunnan,China

盾皮鱼类作为泥盆纪(4.19亿年前至3.59亿年前)最为繁盛的鱼类,曾一度被认为是一类已经灭绝了的类群。随着新的化石被发现,最近的比较解剖学和系统学研究表明,盾皮鱼类代表了早期有颌脊椎动物的集合,由它演化出了现生的软骨鱼类、硬骨鱼类和四足动物。因而盾皮鱼类的起源与演化已成为早期脊椎动物研究中的一个重点。发现于云南早泥盆世埃姆斯期的大眼小瓣鱼,隶属盾皮鱼类中的瓣甲鱼目,其形态学的研究有助于我们理解早期脊椎动物的演化型式。我们在中国科学院脊椎动物演化与人类起源重点实验室对大眼小瓣鱼正型标本进行了高精度断层扫描,后借助Mimics 18.0对采集到的三维形态学数据进行了重建,发现其保存了部分由软骨膜骨包裹的鼻囊。之前,我们主要依据盾皮鱼类颅顶甲上的印痕来推测其脑颅结构。现在借助高精度断层扫描技术,我们可以对保存有软骨膜骨的化石进行重建,得到更精细的脑颅结构。大眼小瓣鱼鼻囊的发现在瓣甲鱼类中属首次,为我们理解盾皮鱼类间的相互演化关系提供了重要的形态学证据。

The Placodermi is a diversified jawed vertebrate group that underwent a highly successful radiation in the Devonian period(419.2–358.9 Ma).Recent anatomical and systematic studies,along with new fossil findings,have shown that placoderms represent an assemblage of primitive jawed vertebrates,which form the paraphyletic crownward part of the gnathostome stem group.As such,placoderms illuminate the step-wise character acquisition in the origin of crown gnathostomes or modern jawed vertebrates(including chondrichthyans,bony fishes and tetrapods).Pauropetalichthys magnoculus,an early member of petalichthyids(a subgroup of placoderms),was discovered from the late Emsian(Early Devonian)of Qujing,Yunnan,China.We investigated Pauropetalichthys using the high-resolution computed tomography(HRCT)apparatus at the Key Laboratory of Vertebrate Evolution and Human Origins,and generated the virtual reconstruction of the skull roof and neurocranium using Mimics(version 18.0).We found that Pauropetalichthys preserved part of nasal capsules which are surrounded by perichondral bones.We used to infer the shape of the neurocranium from the depression on the visceral surface of skull roof in placoderms.By means of HRCT,we can obtain the anatomical details of the neurocranium by reconstructing the preserved perichondral bones,and show for the first time the perichondral lining of the nasal capsules in petalichthyids.The research on Pauropetalichthys adds to our understanding on the morphological diversity in placoderms and helps to evaluate the interrelationships of petalichthyids.