‘The family tree of the horse is beautiful and continuous only in the textbooks. In the reality provided by the results of research it is put together from 3 parts, of which only the last can be described as including horses. The forms of the first part are just has much little horses as the present-day damans are horses. The construction of the whole Cenozoic family tree of the horse is therefore a very artificial one, since it is put together from non-equivalent parts, and cannot therefore be a continuous transformation series.’

Prof. Heribert Nilsson, ‘Synthetische Artbildung’, Verlag CWE Gleerup, Lund, Sweden, 1954.