The Mystery of the Rostral Appendage

In 1891, Elio Modigliani–an Italian biologist from Florence–collected an odd, male agamid lizard from northern Sumatra (type locality listed as “Si-Rambé Forest”). The specimen was brought back to Italy, and cataloged in the Museo Civico di Storia Naturale di Genova (Genova, Italy). More than 40 years later, this single specimen was described by Vinciguerra (1933) as Harpesaurus modiglianii. In his original description, Vinciguerra (1933) notes this Sumatran individual is a “notable lizard that is worth to be known,” and that it can be identified through a “[rostral appendage] as long as the head, simple, formed by a sickle-shaped compressed scale, upward and with its basis surrounded by some rather large scales” (Putra et al. 2020). It would be an injustice if I didn’t include the lovely plate featured in Vinciguerra’s original description (see below).

Vinciguerra’s 1933 illustration from his description of Harpesaurus modiglianii. After Modigliani’s collection of a single specimen, the species would be presumed extinct, and not seen again until 2018, just north of Toba Lake in Sumatra! The rediscovery was documented and published by Putra et al. (2020).

Harpesaurus tricinctus is an Asian agamid lizard described in 1851 from Java, Indonesia, and since then known only from its holotype located at the Paris Natural History Museum (MNHN-RA), supposedly a male, characterized by a long sickle-shaped rostral appendage. Ecological data are virtually lacking since no other specimen have ever been found. Here we review its morphology as compared with its congeners. We also review the morphology of other lizards and some snakes with rostral appendages and discuss their possible functional implications. We identified a South American dactyloid lizard, Anolis proboscis, the males of which show by their general habitus and a long, sword-shaped rostral appendage a striking convergence with the possibly extinct H. tricinctus. Anolis proboscis was also for long considered a rare and little-known lizard but recent field work allowing new observations provided additional data on its ecology. We suggest to use these new data on its habitat requirements which might be comparable to those of the externally so similar but allegedly extinct Indonesian agamid which might have survived in the canopy of tropical humid forests in one of the Greater Sunda Islands of Indonesia.