Hornbills (Bucorvidae and Bucerotidae) are among the most recognizable groups of birds. Their large, curved beak topped by a casque is their most obvious feature. Here, we describe the earliest fossil of a hornbill, and more precisely a Bucerotidae, from the early Miocene of Napak, Uganda. This fossil is a proximal part of a maxilla that can be tentatively assigned to the genus Tockus and which attests to an ancient evolutionary origin of this particular beak shape. The new fossil, as well as several postcranial bones, represents the earliest record of the Bucerotidae dated to about 19 million years ago, and can serve as a calibration point in future molecular phylogenies.

中文翻译：

---

乌干达Napak中新世早期的Bucerotidae（东非）：最早的犀鸟，带有现代喙

犀鸟（Bucorvidae和Bucerotidae）是最容易辨认的鸟类之一。他们最明显的特征是大而弯曲的喙，上面饰有饰钉（casque）。在这里，我们描述了来自乌干达Napak的中新世早期的犀鸟化石，更确切地说是Bucerotidae。该化石是上颌骨的近端部分，可以暂时归类到Tockus属，并证明该特定喙形形状的古老进化起源。新的化石以及颅后骨骼代表了约1900万年前Bucerotidae的最早记录，并可作为未来分子系统发育的定点。