Varanus sp.

Suraprasit, Kantapon, Jaeger, Jean-Jacques, Chaimanee, Yaowalak, Chavasseau, Olivier, Yamee, Chotima, Tian, Pannipa & Panha, Somsak, 2016, The Middle Pleistocene vertebrate fauna from Khok Sung (Nakhon Ratchasima, Thailand): biochronological and paleobiogeographical implications, ZooKeys 613, pp. 1-157 : 58

Taxon classification Animalia Squamata Varanidae

Varanus sp.

Referred material.

Two trunk vertebrae-DMR-KS-05-03-08-36 and DMR-KS-05-03-29-36.

Material description.

The vertebra DMR-KS-05-03-08-36 is more complete than the specimen DMR-KS-05-03-29-36 (for measurements, see Tab. 17). The pre- and postzygapophyses are slightly broken at the second specimen. In both specimens, the neural spines are unfortunately broken away. In anterior view, the cotyle is oval in outline, dorsoventrally compressed, and ventrally oriented (Fig. 35J). The prezygapophyses lack a part of the prezygapophyseal process and are dorsally inclined about 45°. The neural canal is narrow. The neural arch lacks a part of the zygosphene. No paracotylar foramina are present. In posterior view, the condyle and the postzygapophyses show a mirrored morphology with the anterior part. No zygantrum is observed. In dorsal view, the prezygapophyseal facets are drop-shaped and project laterally. The interzygapophyseal constriction is also present. In ventral view, the synapophyses protrude laterally and the centrum is triangular in outline (Fig. 35K).

Taxonomic remarks and comparisons.

We assign these two vertebrae to the the family Varanidae due to the following morphological characters: a centrum tapering posteriorly, a precondylar constriction, a ventrally facing cotyle, and a large and flared condyle ( Romer 1956, Averianov and Danilov 1997). The Khok Sung vertebrae match well the genus Varanus because the condyle is much wider than the posterior end of the centrum and none of the articulatory surface is visible in ventral view. They are also similar in morphology to Varanus according to an amphicoelous centrum, condyles facing very dorsally (anterodorsal direction), an oval-shaped cotyle, a short neural spine, and an absence of the zygosphenes and zygantra ( Lee 2005). Varanus sp. is reported from the Middle Pleistocene of Phnom Loang ( Beden and Guérin 1973). Two varanid species, Varanus cf. komodoensis (larger) and Varanus salvator , are described from the Middle Pleistocene of Trinil H. K. ( Hocknull et al. 2009). The Khok Sung specimens are comparable in size to the recent (e.g., Varanus salvator : NMW 39446/1) and fossil (e.g., Varanus sp.: RMNH DUB 3 and RMNH DUB 5792 recovered in Trinil H. K., Java) specimens. Identifying these vertebrae more precisely to the species-level, more detailed morphological comparisons need to be made in the future.