You may have seen the odd gecko on the ceiling of your home, or the red-eared sliders sunbathing on the banks of a pond in a nearby park. While these two creatures seem very different, they actually belong to the same group of animals we call reptiles!
But what are reptiles? The answer may be slightly complicated, but it is nonetheless every bit as surprising and fascinating.
The most common understanding of “reptiles” originated in the early 19th century.
French zoologist Pierre André Latreille classified Tetrapoda into the four taxa we commonly know of today: mammals, amphibians, birds, and reptiles. At that time, reptiles were categorized based on how they look and how they behave, such as being ectotherms (cold-blooded), having scales, and practising internal fertilisation [1]. In this day and age, biologists increasingly base taxonomy on phylogenetics, or the evolutionary relationships between organisms.
And the story phylogenetics tell may surprise you.
This diagram tells us which animals are most closely related to each other, based on their evolutionary history.
It’s like a family tree, where at each intersection you can find a common ancestor of each branch. Interestingly, you can see from the diagram that Crocodilians are more closely related to birds than they are to other “reptiles”.
Modern biologists have reconciled this by accepting that birds are, in fact, reptiles!
Many museums now use the term non-avian reptiles or “reptiles” (using quotation marks) to represent classically defined reptiles (Latreille’s definition of reptiles). Through the rest of this article, we will talk about reptiles as non-avian reptiles.
The Biodiversity of Singapore catalogue records 110 species of reptiles in Singapore separated into 3 living orders: Squamata (lizards and snakes), Crocodilia (crocodiles) and Testudines (turtles). However, the number is almost certain to be higher due to the cryptic nature of some of these animals, leading to new discoveries even till today.
For example, it was only in 2014 when researchers discovered the Blackwater mud snake (Phytolopsis punctata) for the first time in Singapore, caught in fish traps for a biodiversity survey. This elusive snake inhabits freshwater swamps, burrowing quickly into the mud to hide, eluding detection.
Reptiles are not the most well-loved group of animals, often being labelled as cold-blooded killers or scaly, squirmy critters. It is true that some reptiles are venomous or deadly to humans, and through history, we have learned to be wary of and to fear some reptiles which once helped our early human ancestors survive. This fear could be evolutionarily deeply ingrained into our instinct.
However, we now know that reptiles fill a vital niche in our ecosystems. They are the scavengers that clean up rotting flesh or the predators that keep other animal populations in check. Although scaly and squirmy, the diversity of reptiles you can find – even in our tiny red dot – are beautiful (and even cute!) in their own right.
Glossary:
Biodiversity survey – an ecological assessment to provide a baseline overview of a land, identifying any features of conservation importance. This might be flora, fauna or wildlife habitats. (Taken from Betts Ecology)
Niche – a role taken by a type of organism within its community
Order – a principal taxonomic category that ranks below class and above family
Phylogenetics – a part of systematics that addresses the inference of the evolutionary history and relationships among or within groups of organisms
Taxon – a taxonomic group of any rank, such as a species, family, or class
Taxonomy – the branch of science concerned with classification, especially of organisms
Tetrapoda – a superclass of animals that includes all limbed vertebrates
References
1. Lim, K.K.P., F.L.K. Lim, and Singapore Science Centre., A guide to the amphibians and reptiles of Singapore. 1992, Singapore: : Singapore Science Centre.
