Snakes and Their History
Snakes as a species are around 130 million years old. The first indications from early fossils places them in the Cretaceous period but the fossil evidence is inconclusive as small reptiles don’t leave good clear fossils as their small bones breakdown easily and become scattered. However, it is largely believed that the split genetic split between lizards and snakes happened around the Cretaceous period.
The earliest fossil records of the ancestors of snakes and lizards appeared as long ago as 200 million years, during the Triassic period along with the first dinosaurs. Snakes and Lizards are classified as Reptiles and form a class of vertebrate animals that sit between fish and amphibians on one side and birds and mammals on the other side.
Early fossils of snake like animals showed that they were short and heavy and were a combination of features from both lizards and snakes as we know them today. Unfortunately the link between these early reptiles and modern day snakes is lacking evidence and incomplete, and is based largely on theory.
It is most popularly believed that snakes evolved from a primitive burrowing type of lizard which would feed off subterranean creatures and avoid larger surface based predators. Early snakes would probably have lost the use of sight as their world was in total darkness. Similarly, ears would have been impractical and modern snakes developed a mechanism to detect sound through vibrations and sophisticated abilities for smelling scents and acute touch sensors.
Today, there is no family of lizards that provide a conclusive link between lizards and snakes. The Legless Amphisbaenians, or worm-lizard, was once thought to be a lizard evolving into a snake but research has discovered unique differences in this species that indicates it has evolved separately from lizards and snakes.
There are about 3000 species of modern snakes broken into 11 families and 354 genera or sub-family. Snakes form one of the four sub-orders of the Reptile class called Squamata, the others being;
Chelonia – tortoises and turtles,
Crocodylia – crocodiles and alligators
Rhynchocephalia – Tuatara.
Squamata includes lizards, amphisbaenians and snakes. Snakes form a sub-order of Squamata known as Serpentes – hence the term serpents which is derived from the Latin name serpens, a crawling animal or snake.
In more generic terms the classes of vertebrate animals are orgainsed into six classes:
5. Bony Fish
6. Cartilaginous Fish
Reptiles have unique characteristics that make them different from all other vertebrates. The most recognizable characteristic is that all reptiles have scaly skin, they respire (breathe) by means of lungs and they are cold blooded. No other vertebrate possess this unique combination of characteristics.
Snakes and their reptilian families increase in size with geographic locations closer to the equator. This is believed to be a result of the increased activity through the year due to climates that provide higher temperatures through the year. There are also many more species located in the warmer climates than in the cooler climates. Also, as altitude increases temperatures fall so there are fewer species of snakes (and other reptiles) in regions of high altitudes.
In spite of the constraints due to environmental preferences and needs, remarkably, snakes have populated a very high percentage of the earth’s surface. They are here to stay.