The Septuagint was made long before "modern science", and it says "monoceros".
I have done some studying into unicorns, and among other things, there are pictures on the Gates of Ishtar in Iraq that show one horned creatures that differ to rhinoceroses.
There are pictures and descriptions of one-horned animals from various ancient civilisations.
These picture from the Indus Valley Civilisation shows an Indian Buffalo with two horns (so that people cannot say that the unicorn is a two horned creature shown in relief), a unicorn and a rhino.
