A collaboration between Sapienza University and the Universidad Nacional Autónoma de México, published in the journal Amphibia-Reptilia, identified a new species of spiny lizard called Sceloporus geminus characterised by a unique combination of several characters, including a distinctive colour pattern of the scale collar at the base of the head. This species, which had previously been confused with others, was discovered in the southernmost region of the Sierra Madre Oriental mountain range in Mexico.

The research team, which has been carrying out field missions for 15 years to study the systematic biology of Mexican reptiles in the states of Chiapas and Jalisco, compared the individuals under study with over 160 specimens of other species of the genus Sceloporus preserved in 15 different museums, analysing their genetic and morphological characteristics.

"The morphological study", says Riccardo Castiglia of Sapienza University, "was based on 30 different characteristics and a phylogenetic analysis that included the examination of mitochondrial and nuclear genetic markers, highlighting the uniqueness of the new species compared to other related species. Its bright ventral colouration, on the other hand, is also present in other species of the genus Sceloporus and serves to communicate the individual's state of health, being indicative of the physical strength and competitive ability of the males. In this way, females can choose a male in better physical condition".

Like other related species, Sceloporus geminus is a viviparous animal, in that the female does not lay eggs but gives birth to already-formed babies. This particular strategy seems to be advantageous in preventing increased egg mortality due to low temperatures.

This study adds a new vertebrate species to the Mexican fauna, confirming the rich and still partly unexplored biodiversity of this region.

References:

More cryptic diversity among spiny lizards of the Sceloporus torquatus complex discovered through a multilocus approach - Gustavo Campillo-García, Oscar Alberto Flores-Villela, Brett Oliver Butler, Miriam Benabib, and Riccardo Castiglia - Amphibia-Reptilia 2023 DOI:10.1163/15685381-bja10163

Further Information

Riccardo Castiglia
Charles Darwin Department of Biology and Biotechnology 
riccardo.castiglia@uniroma1.it