Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Xiwaidajie 142, PO Box 643, Beijing 100044, China.
Nat Commun. 2012 Apr 10;3:772. doi: 10.1038/ncomms1764.
Coelacanths are known for their evolutionary conservatism, and the body plan seen in Latimeria can be traced to late Middle Devonian Diplocercides, Holopterygius and presumably Euporosteus. However, the group's early history is unclear because of an incomplete fossil record. Until now, the only Early Devonian coelacanth is an isolated dentary (Eoactinistia) from Australia, whose position within the coelacanths is unknown. Here we report the earliest known coelacanth skull (Euporosteus yunnanensis sp. nov.) from the Early Devonian (late Pragian) of Yunnan, China. Resolved by maximum parsimony, maximum likelihood and Bayesian analyses as crownward of Diplocercides or as its sister taxon, the new form extends the chronological range of anatomically modern coelacanths by about 17 Myr. The finding lends support to the possibility that Eoactinistia is also an anatomically modern coelacanth, and provides a more refined reference point for studying the rapid early diversification and subsequent evolutionary conservatism of the coelacanths.
腔棘鱼以其进化保守性而闻名，拉蒂迈鱼的身体结构可以追溯到晚泥盆世的 Diplocercides、 Holopterygius 和可能的 Euporosteus。然而，由于化石记录不完整，该群体的早期历史尚不清楚。到目前为止，唯一的早泥盆世腔棘鱼是来自澳大利亚的孤立的齿骨（Eoactinistia），其在腔棘鱼中的位置尚不清楚。在这里，我们报告了来自中国云南早泥盆世（晚普里安期）的最早已知的腔棘鱼头骨（Euporosteus yunnanensis sp. nov.）。通过最大简约法、最大似然法和贝叶斯分析得到的结果表明，新种位于 Diplocercides 或其姊妹分类群的冠部，将解剖学上现代腔棘鱼的时间范围延长了约 1700 万年。这一发现为 Eoactinistia 也是一种解剖学上现代腔棘鱼的可能性提供了支持，并为研究腔棘鱼的快速早期多样化和随后的进化保守性提供了更精确的参考点。
