A Silurian maxillate placoderm illuminates jaw evolution.
一种志留纪全颌盾皮鱼揭示颌的演化

Authors / 作者: Zhu M, Ahlberg PE, Pan Z, Zhu Y, Qiao T, Zhao W, Jia L, Lu J.
Journal / 期刊: Science (New York, N.Y.)
Year / 年份: 2016
DOI: 10.1126/science.aah3764
Publisher / 出版社: https://www.science.org/doi/10.1126/science.aah3764
Abstract source / 摘要来源: https://europepmc.org/article/MED/27846567

Author abstract / 作者原文摘要
The discovery of Entelognathus revealed the presence of maxilla, premaxilla, and dentary, supposedly diagnostic osteichthyan bones, in a Silurian placoderm. However, the relationship between these marginal jaw bones and the gnathal plates of conventional placoderms, thought to represent the inner dental arcade, remains uncertain. Here we report a second Silurian maxillate placoderm, which bridges the gnathal and maxillate conditions. We propose that the maxilla, premaxilla, and dentary are homologous to the gnathal plates of placoderms and that all belong to the same dental arcade. The gnathal-maxillate transformation occurred concurrently in upper and lower jaws, predating the addition of infradentary bones to the lower jaw.

Summary basis / 解读依据
摘要解读依据已查看的索引作者摘要；如已保存全文，可用于进一步阅读。
Summary based on the inspected indexed author abstract; archived full text, when available, is provided for further reading.

Key findings / 主要发现
第二种志留纪全颌盾皮鱼填补传统盾皮鱼颌齿板与边缘颌骨之间的形态间隙。其解剖特征支持将上颌骨、前上颌骨和齿骨与盾皮鱼颌齿板视为同一齿列中的同源结构。
A second Silurian maxillate placoderm bridges conventional placoderm gnathal plates and marginal jaw bones. Its anatomy informs a proposed homology between the maxilla, premaxilla and dentary and placoderm gnathal plates within one dental arcade.

Conclusions / 结论
作者提出，颌齿板向边缘颌骨的转变在上下颌同步发生，早于下颌腹侧骨片的加入。本文新研究类群为麒麟鱼，并非全颌鱼。
The authors propose that the gnathal-to-maxillate transformation occurred in upper and lower jaws before infradentary bones were added. The main new taxon is Qilinyu, not Entelognathus.

Relevance / 关联说明
新研究物种为麒麟鱼；全颌鱼是边缘颌骨同源性的重要比较对象。
The new species is Qilinyu; Entelognathus supplies important comparative evidence for marginal jaw-bone homology.