The Tropidurus Genus & Struggling with Taxonomy
Ah taxonomy…thou art a beautiful and heartless bitch. If you’ve ever looked into the tropidurus genus post 1979, you know what I’m talking about!
It’s not uncommon for friends and family to send or show me photographs of reptiles and amphibians they encounter during their holidays. They often ask me to identify the species, and usually, this can be done fairly easily - especially when you know exactly where the individual was found. However, some species can be very hard to differentiate by image and location alone.
My brother found the individual displayed in the above photograph in Rio de Janeiro a few years ago. Truthfully, I had never paid much attention to this genus before, and figuring out the species became even more complicated the more I looked into it. As Frost, et al. (2001, pp.352) very eloquently put in their publication, “from 1979 to present (…) effort on the elucidation of the systematics of the taxon has increased, seemingly exponentially”. In his 1987 paper, Rodrigues gives us a brief history of the genus and the species that were once recognised under it. Boulenger (1885) was the first attempt at revising the then established norm that the genus encompassed about 15 different species but Boulenger maintained only 3 species from the fifteen - Tropidurus hygomi, Tropidurus torquatus and Tropidurus hispidus.
In 1930, Burt & Burt classified T. hispidus as a subspecies of T. torquatus and made other changes seemingly without many valid reasons. It was only in 1963 and 1969 that some of these issues really started to be addressed and by the time that Rodrigues started his main study on the species of the Tropidurus genus, he based them on 11 recognised species that occurred south of the Amazon River. His study was made possible by the ever growing collection of the University of Sao Paulo Zoology Museum (MZUSP) that included 6,200 individuals collected from 305 different localities. His 1987 paper concluded by recognising seven Tropidurus species - T. cocorobensis, T. erythrocephalus, T. insulanus, T. itambere, T. montanus, T. mucujensis and T. oreadicus.
Since then, species of the Tropidurus genus were described and mentioned in subsequent pieces of research and I’ve had much fun (not) trying to figure out to which species the little guy from the photograph belongs.
You too may have heard scientists discuss issues with language barriers when it comes to earlier scientific publications and a questionable translation of said earlier papers. While I appreciate that this occurs from time to time, I would expect this to be less of an issue nowadays. In this instance, although one of the main earlier publications on the Tropidurus genus by Rodrigues in 1987 was in Portuguese, subsequent publications were issued in English, such as Frost, et al. (2001) - in which Rodrigues is actually one of the co-authors - and Domingos, et al. (2017).
With all that in mind, when I was attempting to identify this individual, my main obstacle (apart from the obvious lack of data on the individual) was determining the current taxonomic nomenclature being used. While reading Gomes de Carvalho (2013) on the distribution and conservation of the genus, I settled on this individual possibly belonging to the Tropidurus torquatus species based on its distribution (see map below).
To end the post on a positive note, a bit of a ‘fun’ fact about this genus - locals tend to call pretty much every species of the Tropidurus genus ‘calango’. Now, as you probably gathered, I am not certain I got the species right so if you have any insights, I am all ears! Drop me a line at firstname.lastname@example.org and help me unravel this mystery!
Domingos, F.M.C.B., Colli, G.R., Lemmon, A., Lemmon, E.M., Beheregaray, L.B., (2017). In the shadows: Phylogenomics and coalescent species delimitation unveil cryptic diversity in a cerrado endemic lizard (Squamata: Tropidurus). Molecular Phylogenetics and Evolution, 107, p.455-465.
Frost, D.R., Rodrigues, M.T., Grant, T., Titus, T.A., (2001). Phylogenetics of the Lizard Genus Tropidurus (Squamata: Tropiduridae: Tropidurinae): Direct Optimization, Descriptive Efficiency, and Sensitivity Analysis of Congruence Between Molecular Data and Morphology. Molecular Phylogenetics and Evolution, 21(3), p.352-371.
Gomes de Carvalho, A.L., (2013). On the distribution and conservation of the South American lizard genus Tropidurus Wied-Neuwied, 1825 (Squamata: Tropiduridae). Zootaxa, 3640(1), p.42-56.
Rodrigues, M.T., (1987). Sistematica, Ecologia e Zoogeografia dos Tropidurus do Grupo Torquatus ao Sul to Rio Amazonas (Sauria, Iguanidae). Arquivos de Zoologia: Museu de Zoologia da Universidade de Sao Paulo, 31(3), p.105-230.