A new species of <i>Varanus</i> (Anguimorpha: Varanidae) from the early Miocene of the Czech Republic, and its relationships and palaeoecology

<p>Skeletal remains of a new early Miocene (Ottnangian, MN 4 mammal zone) monitor lizard, <i>Varanus mokrensis</i> sp. nov., are described from two karst fissures in the Mokrá-Western Quarry (1/2001 Turtle Joint; 2/2003 Reptile Joint), Czech Republic, providing the first documented example of a European varanid for which osteological data permit a well-supported assignment to the genus <i>Varanus</i>. The new species is morphologically similar to the Recent Indo-Asiatic varanids of the <i>Varanus bengalensis</i> group. It differs from all other <i>Varanus</i> species on the basis of a single autapomorphy and a combination of 11 characters. As a distinguishing feature of <i>V. mokrensis</i>, the parietal and squamosal processes of the postorbitofrontal form a narrowly acute angle. The teeth show distinct, smooth cutting edges along the mesial and distal margins of the apical portion of their crowns. This feature is not observed in most extant Asiatic <i>Varanus</i> species and may represent a plesiomorphic condition. The results of parsimony phylogenetic analyses, with and without character reweighting, reveal poor resolution within <i>Varanus</i>. A Bayesian analysis shows <i>V. mokrensis</i> to be closely related to extant representatives of the Indo-Asiatic <i>Varanus</i> clade, with close affinities to the <i>V. bengalensis</i> species group. The topology of the Bayesian tree supports the hypothesis that Miocene monitors from Mokrá are representatives of a lineage that is ancestral to the well-defined clade of extant African varanids, including the early Miocene <i>V. rusingensis</i>. In addition, our results support a Eurasian origin for the varanid clade. The extant African <i>Varanus</i> species probably originated in the late Oligocene. The radiation of African varanids probably occurred during the late Oligocene to early Miocene time interval. The occurrence of <i>Varanus</i> in the early Miocene of Mokrá-Western Quarry corresponds to the warm phase of the Miocene Climatic Optimum. Remains of a diverse aquatic and heliophobe amphibian fauna at the 2/2003 Reptile Joint site indicate more humid conditions than those at the 1/2001 Turtle Joint site.</p> <p><a href="http://zoobank.org/urn:lsid:zoobank.org:pub:B1553295-8AC7-42F0-91C4-51C4C13F1C9D" target="_blank">http://zoobank.org/urn:lsid:zoobank.org:pub:B1553295-8AC7-42F0-91C4-51C4C13F1C9D</a>