The eastern long-tailed hornbill (Horizocerus cassini) is a species of bird in the hornbill family Bucerotidae found in humid forests of West Africa. It was formerly considered to be conspecific with the western long-tailed hornbill (Horizocerus albocristatus) with the English name "white-crested hornbill".
The eastern long-tailed hornbill was formally described in 1903 by the German naturalist Otto Finsch based on a specimen from Gabon in West Africa. He coined the binomial name Ortholophus cassini.[1] [2] The specific epithet was chosen to honour the American ornithologist John Cassin.[3] The species is now placed in the genus Horizocerus that was introduced in 1899 by the American ornithologist Harry C. Oberholser. The eastern long-tailed hornbill was formerly considered to be conspecific with the western long-tailed hornbill (Horizocerus albocristatus) with the English name "white-crested hornbill".[4]