Snout–vent length (SVL) is a morphometric measurement taken in herpetology from the tip of the snout to the most posterior opening of the cloacal slit (vent)."direct line distance from tip of snout to posterior margin of vent" It is the most common measurement taken in herpetology, being used for all amphibians,

lepidosaurs The Lepidosauria (, from Greek meaning ''scaled lizards'') is a subclass or superorder of reptiles, containing the orders Squamata and Rhynchocephalia. Squamata includes snakes, lizard Lizards are a widespread group of squamate reptiles, ...

, and

crocodilia Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest livi ...

ns (for turtles, carapace length (CL) and plastral length (PL) are used instead). The SVL differs depending on whether the animal is struggling or relaxed (if alive), or various other factors if it is a preserved specimen. For fossils, an osteological correlate such as precaudal length must be used. When combined with weight and body condition, SVL can help deduce age and sex.

Advantages

Because tails are often missing or absent, especially in juveniles, SVL is seen as more invariant than total length. Even in the case of crocodiles, tail tips may be missing.

Methods

The measurements may be taken with dial calipers or

digital calipers A caliper (British spelling also calliper, or in plurale tantum sense a pair of calipers) is a device used to measure the dimensions of an object. Many types of calipers permit reading out a measurement on a ruled scale, a dial, or a digital dis ...

. Various devices are used to position the animal while the measurement is being taken, such as a snake tube, "Mander Masher", or a "Salamander Stick".

Advantages

Methods

References

Further reading