On the systematic position of the oldest insular ruminant <i>Sardomeryx oschiriensis</i> (Mammalia, Ruminantia) and the early evolution of the Giraffomorpha

<p><i>Sardomeryx oschiriensis</i> is the oldest insular ruminant known (Burdigalian of Oschiri, Sardinia, Italy). Only two isolated upper dentitions compose the type material. The first phylogenetic hypothesis proposed <i>Sardomeryx</i> to be closely related to the Giraffoidea and especially the Late Miocene Sardinian derived giraffid <i>Umbrotherium</i>. Description of new specimens from Laerru (Burdigalian, Sardinia, Italy), including lower teeth and decidual premolars, leads to a reinterpretation of the phylogenetic position of <i>Sardomeryx</i> and of the early evolutionary history of the Giraffomorpha. Based on our phylogenetic hypothesis, <i>Sardomeryx</i> is nested within the Giraffomorpha as a basal Palaeomerycoidea. <i>Sardomeryx</i> may have originated from south-western Europe before the separation of the Corsica-Sardinia Block during the earliest Miocene. The enigmatic latest Oligocene <i>Bedenomeryx</i> from the south-west France is also considered as a basal (and the most ancient) member of the Palaeomerycoidea. Including <i>Bedenomeryx</i> in the Palaeomerycoidea lineage would place the origin of the Giraffoidea, the sister family of Palaeomerycoidea, within the Oligocene. <i>Bedenomeryx</i> is characteristic of arid south-western France, directly echoing the advanced condition observed in the <i>Sardomeryx</i> dentition (e.g. high crowned teeth, absence of the external postprotocristid on lower molar, reduction in length of the premolar row) typical for insular ruminants in arid environments.</p>