The Phylogenetic Position of Lanthanotus based on its Head Masculature

Abstract

McDowell and Bogert (1954:51) concluded “that Lanthanotus is not a primitive pre-platynotan intermediate between the Helodermatidae and the Varanidae but rather is an advanced and specialised platynotan lizard…”. They considered Lanthanotus to be more closely related to varanoids than to Heloderma, and derived him from the closely related Cretaceous families Mosasauridae, Dolichosauridae and Aigialosauridae. This view has been maintained by McDowell in 1967 and in 1972. Russell (1967) on the other hand believes Lanthanotus to be derived from a varanid ancestor, and finds it to approach the fossil saniwid varanids most closely in a number of characteristics. However, the structure of the head musculature clearly supports a somewhat intermediate position of Lanthanotus between the Helodermatidae and the Varanidae.