Kurochkin Evgeny N, Dyke Gareth J, Saveliev Sergei V, Pervushov Evgeny M, Popov Evgeny V
Paleontological Institute of Russian Academy of Sciences, Moscow GSP-7 117997, Russia.
Biol Lett. 2007 Jun 22;3(3):309-13. doi: 10.1098/rsbl.2006.0617.
Fossils preserving traces of soft anatomy are rare in the fossil record; even rarer is evidence bearing on the size and shape of sense organs that provide us with insights into mode of life. Here, we describe unique fossil preservation of an avian brain from the Volgograd region of European Russia. The brain of this Melovatka bird is similar in shape and morphology to those of known fossil ornithurines (the lineage that includes living birds), such as the marine diving birds Hesperornis and Enaliornis, but documents a new stage in avian sensory evolution: acute nocturnal vision coupled with well-developed hearing and smell, developed by the Late Cretaceous (ca 90Myr ago). This fossil also provides insights into previous 'bird-like' brain reconstructions for the most basal avian Archaeopteryx--reduction of olfactory lobes (sense of smell) and enlargement of the hindbrain (cerebellum) occurred subsequent to Archaeopteryx in avian evolution, closer to the ornithurine lineage that comprises living birds. The Melovatka bird also suggests that brain enlargement in early avians was not correlated with the evolution of powered flight.
在化石记录中，保存有软组织解剖痕迹的化石十分罕见；而能为我们了解生物生活方式提供线索的、与感觉器官大小和形状相关的证据则更为稀少。在此，我们描述了俄罗斯欧洲部分伏尔加格勒地区发现的一种独特的鸟类大脑化石。这种梅洛瓦特卡鸟的大脑在形状和形态上与已知的化石今鸟型类（包括现存鸟类的谱系）相似，比如海洋潜水鸟类黄昏鸟和鱼鸟，但它记录了鸟类感官进化的一个新阶段：在晚白垩世（约9000万年前）发展出的敏锐的夜间视觉，以及发达的听觉和嗅觉。这块化石还为最原始鸟类始祖鸟之前类似鸟类的大脑重建提供了新线索——在鸟类进化过程中，始祖鸟之后出现了嗅觉叶（嗅觉）的缩小和后脑（小脑）的增大，这一变化更接近包括现存鸟类的今鸟型类谱系。梅洛瓦特卡鸟还表明，早期鸟类的大脑增大与动力飞行的进化并无关联。
