Morphometric analysis of chameleon fossil fragments from the Early Pliocene of South Africa: a new piece of the chamaeleonid history

Abstract

The evolutionary history of chameleons has been predominantly studied through phylogenetic approaches as the fossil register of chameleons is limited and fragmented. The poor state of preservation of these fossils has moreover led to the origin of numerous nomen dubia, and the identification of many chameleon fossils remains uncertain. We here examine chameleon fossil fragments from the Early Pliocene Varswater formation, exposed at the locality of Langebaanweg "E" Quarry along the southwestern coast of South Africa. Our aim was to explore whether these fossil fragments could be assigned to extant genera. To do so, we used geometric morphometric approaches based on microtomographic imaging of extant chameleons as well as the fossil fragments themselves. Our study suggests that the fossils from this deposit most likely represent at least two different forms that may belong to different genera. Most fragments are phenotypically dissimilar from the South African endemic genus Bradypodion and are more similar to other chameleon genera such as Trioceros or Kinyongia. However, close phenetic similarities between some of the fragments and the Seychelles endemic Archaius or the Madagascan genus Furcifer suggest that some of these fragments may not contain enough genus-specific information to allow correct identification. Other fragments such as the parietal fragments appear to contain more genus-specific information, however. Although our data suggest that the fossil diversity of chameleons in South Africa was potentially greater than it is today, this remains to be verified based on other and more complete fragments.

First description of a fossil chamaeleonid from Greece and its relevance for the European biogeographic history of the group

“…The new identification of Chamaeleo cf. andrusovi in Aliveri further confirms the already proposed ecological settings of the locality, as the presence of chamaeleonids is well known to be indicative of warm climates (Moody and Roček 1980) and further suggests relatively dense vegetation (Maul et al 2011), although several extant genera are known to occur in both closed and open habitats (Tolley et al 2008;Dollion et al 2015).…”

“…The idea of two or more sympatric chamaeleonid species in the same locality is reminiscent of a similar situation in several extant species (Raselimanana and Rakotomalala 2003;Tolley and Menegon 2013). Such higher species diversity within a single region has been also recently inferred for fossil chamaeleonids (Dollion et al 2015). On the other hand, many regions harbour only monospecific communities of extant chamaeleonids (Tolley and Menegon 2013).…”

“…We acknowledge here, however, that on several occasions, even fragmentary fossils can bear diagnostic characters. This is the situation, for example, when geometric morphometric approaches are used (Bastir et al 2014;Cornette et al 2015), a case study that has also been recently applied to fossil chamaeleonids (Dollion et al 2015). The latter authors characteristically noted that even small fragments such as parts of the maxilla and the parietal could be useful in taxonomic identification.…”

“…Molecular data support a Cretaceous dichotomy between chamaeleonids and other Acrodonta, although the exact dates vary among different researches (Raxworthy et al 2002;Wiens et al 2006;Townsend et al 2011;Bolet and Evans 2013;Dollion et al 2015). Africa and Madagascar have long been proposed as potential centres of origin for chamaeleonids (Hillenius 1959(Hillenius , 1978bBlanc 1972;Klaver 1977;Dollion et al 2015). More specifically, suggested, on the base of molecular data, that chamaeleonids originated in Africa around the Late Cretaceous, after the break-up of the supercontinent Gondwana, with two independent oceanic dispersals to Madagascar (their modern biodiversity hotspot) during the Palaeocene and the Oligocene.…”

“…Stem representatives of Chamaeleonidae are not known or at least they have not yet been identified, rendering their early evolutionary history tantalizing and obscure (Bolet and Evans 2013;Simões et al 2015). Molecular data support a Cretaceous dichotomy between chamaeleonids and other Acrodonta, although the exact dates vary among different researches (Raxworthy et al 2002;Wiens et al 2006;Townsend et al 2011;Bolet and Evans 2013;Dollion et al 2015). Africa and Madagascar have long been proposed as potential centres of origin for chamaeleonids (Hillenius 1959(Hillenius , 1978bBlanc 1972;Klaver 1977;Dollion et al 2015).…”