Claudius Aelianus (ca. 175-ca. 235), often seen as just Aelian, born at Praeneste, was a Roman author and teacher of rhetoric who flourished under Septimius Severus and probably outlived Elagabalus, who died in 222. He spoke Greek so perfectly that he was called "honey-tongued" (meliglossos); Roman-born, he preferred Greek authors, and wrote in a slightly archaizing Greek himself.
His two chief works are valuable for the numerous quotations from the works of earlier authors, which are otherwise lost, and for the surprising lore, which offers unexpected glimpses into the Greco-Roman world-view.
On the Nature of Animals, ("On the Characteristics of Animals" is an alternative title; usually cited, though, by its Latin title), is a curious collection, in 17 books, of brief stories of natural history, sometimes selected with an eye to conveying allegorical moral lessons, sometimes because they are just so astonishing.
Aelian's anecdotes on animals rarely depend on direct observation: they are almost entirely taken from written sources, often Pliny the Elder, but also other authors and works now lost, to whom he is thus a valuable witness. He is more attentive to marine life than might be expected, though, and this seems to reflect first-hand personal interest; he often quotes "fishermen". At times he strikes the modern reader as thoroughly credulous, but at others he specifically states that he is merely reporting what is told by others, and even that he does not believe them. Aelian's work is one of the sources of medieval natural history and of the bestiaries of the Middle Ages; in some ways an allegory of the moral world, an Emblem Book.
Conrad Gessner (or Gesner), the Swiss scientist and natural historian of the Renaissance, made a Latin translation of Aelian's work, to give it a wider European audience. The latest Latin translation is that of Friderich Jacobs (1832), based on both Gesner's translation and that of Petrus Gillius (1533). An English translation by A. F. Scholfield has been published in the Loeb Classical Library.
(text from Wikipedia: http://en.wikipedia.org/wiki/Claudius_Aelianus)