With a new discovery, lizard studies get an edge

  • With the description of a new species of lizard, Agasthyagama edge, in Kerala, one more species gets added to the genus Agasthyagama.
  • Commonly called kangaroo lizards, they derive their name from their distinct behaviour of running on their hindlimbs when threatened.
  • Not very different from Agasthyagama beddomii in its appearance, the identity of the new lizard was ascertained after combing through specimens available in Indian and international museums and conducting genetic and morphological analyses.  

In a stroke of serendipity, a team of researchers stumbled upon a new-to-science species of lizard while conducting a survey of the landscape for the habitat of another new discovery, Nasikabatrachus sahyadrensis, commonly known as the purple frog or the Mahabali frog. The frog which lives underground emerges only once annually.

The diminutive lizard that the researchers spotted measures approximately 3 to 4.5 cm from head to tail. It was crawling along the roadside near a stream in the Kulamavu area of Idukki district in 2014-2015.

Agasthyagama edge is the new species of lizard in the genus Agasthyagama that was spotted in Kerala a decade ago. Photo by Sandeep Das.

This new lizard species has been named Agasthyagama edge in honour of the Edge of Existence programme by the Zoological Society of London dedicated to conserving species that are evolutionarily distinct and globally endangered (EDGE) across various regions of the world. Furthermore, it provides support to conservation research projects led by early-career researchers in countries such as India through their Edge Fellowship programme, which benefited two members in this research group — Sandeep Das and Rajkumar K.P.

Have you heard about the new kangaroo lizard?

A chance encounter

Sandeep Das from the Department of Zoology, University of Calicut, recalls that initially, the team didn’t pay much attention to the lizard because it resembled Agasthyagama beddomii, also known as the northern kangaroo lizard, found in the Agasthyamalai range. “We recorded it but then forgot about it,” he says. It wasn’t until they decided to share the photos with their colleague Deepak Veerappan, an Agamid specialist in Southeast Asia, that the narrative took a turn.

Veerappan pointed out that Idukki was a distant location for Agasthyagama beddomii, which is endemic to Agasthyamalai, over 100 kilometres away from where the new species was discovered. “He suggested we investigate the genetic and morphological differences between the two species,” Das explains. Subsequent genetic and morphological analyses confirmed that the lizard in Idukki was indeed a new species within the Agasthyagama genus, which until then was thought to be monotypic or a genus with only one species.

Agasthyagama edge differs morphologically from Agasthyagama beddomii by the number of scales in the throat region and the colour of the scales in the throat of the breeding males. Photo by Sandeep Das.

In a paper published in the journal Vertebrate Zoology, the authors describe the species as “superficially similar to Agasthyagama beddomii in overall shape, size and colour but can be distinguished by combination of characters.” The distinct morphological characters include the number of scales in the throat region which was found to be lesser in A. edge in comparison to A. beddomii. The colour of the scales in the throat region of the breeding males were also found to be different. Both species differed genetically as well. A. edge now joins A. beddomiias another kangaroo lizard species in India.

Run like a kangaroo

Kangaroo lizards possess several distinguishing features and characteristics that set them apart from other Agamids. Unlike typical lizards, they are not arboreal but terrestrial, often found dwelling in soil and among foliage. “This behaviour may have evolved as a form of resource partitioning with other Agamids,” suggests Das. Their common name – kangaroo lizards, likely stems from their unique threat behaviour of sprinting on their hindlimbs at considerable speed. Additionally, they follow a carnivorous diet, with small animals and insects comprising a significant portion of their food intake.

A female Agasthyagama edge. Agasthyagama lizards are commonly called kangaroo lizards for their distinct threat behaviour of sprinting on their hindlimbs. Photo by Sandeep Das.

In order to conduct a more detailed study of the species, the team returned to the location in subsequent years and captured a few individuals for analysis. Additionally, they sought out museum specimens available in India, although these proved to be scarce. Recognising that the specimens of Agasthyagama beddomii collected in 1935 and the late 1980s are housed at the Chicago Field Museum and the Natural History Museum in London, the team patiently awaited an opportunity for comparison. Veerappan undertook the challenging task of visiting the Field Museum in Chicago, where a substantial collection of Agasthyagama beddomii samples, gathered in the 1980s, was accessible. The whole process took a decade, which the researchers believe was worth the wait.

“Once we had this information our sample size increased and we were confident with the one morphological character which is species-specific. We did have a pretty convincing molecular difference to confirm that we had a new species, but one has to be thorough when naming species so we checked all possible diagnostic characters,” Veerappan informs Mongabay-India.

The discovery stands as yet another testament to the vast diversity of species present in the Western Ghats. Veerappan emphasises that the researchers’ prior assumption regarding the comprehensive documentation of reptile fauna in the Western Ghats was inaccurate. “The discovery and inclusion of genetic data for new species enable scientists worldwide to grasp the evolutionary patterns and diversification of different groups of organisms,” Veerappan concludes.

Read more: New species of parachute gecko recorded in Mizoram


Banner image: Agasthyama edge is the new kangaroo lizard spotted in Kerala. It took a decade for the researchers to ascertain the identity of the new species since it was similar in size, shape and has many features of Agasthyagama beddomii. Photo by Sandeep Das.

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