Colubridae

Colubrids are a very diverse group of snakes. They can exhibit many different body styles, body sizes, colours, and patterns. They can also live in many different types of habitats including aquatic, terrestrial, semi-arboreal, arboreal, desert, mountainous forests, semi-fossorial, and brackish waters. A primarily shy and harmless group of snakes, the vast majority of colubrids are not venomous, nor do most colubrids produce venom that is medically impactful to mammals. However, the bites of some can escalate quickly to emergency situations. Furthermore, within the Colubridae, the South African boomslang and twig snakes, as well as the Asian keelback snakes (Rhabdophis sp.) have long been notorious for inflicting the worst bites on humans, with the most confirmed fatalities. Some colubrids are described as opisthoglyphous (often simply called "rear-fanged"), meaning they possess shortened, grooved "fangs" located at the back of the upper jaw. It is thought that opisthoglyphy evolved many times throughout the natural history of squamates While feeding, colubrids move their jaws backward to create a cutting motion between the posterior edge and the prey's tissue. Colubrids can also be proteroglyphous (fangs at the front of the upper jaw, followed by small solid teeth) Characteristics of Colubridae include limbless bodies, left lung that is reduced or absent with or without a tracheal lung, well-developed oviducts, premaxillaries that lack teeth, maxilaries oriented longitudinally with teeth that are solid or grooved, mandible without a coronoid bone, dentary that has teeth, only a left carotid artery, intracostal arteries arising from the dorsal aorta every few trunk segments, no cranial infrared receptors occurring in pits or surface indentations, and optic foramina that typically traverse the frontal–parietal–parasphenoid sutures. == Reproduction ==

mating Most Colubridae are oviparous (mode of reproduction where an egg is produced that will later hatch) with clutch size varying by size and species of snake. However, certain species of snakes from the subfamilies of Natricinae and Colubrinae are viviparous (mode of reproduction where young are live birthed). These viviparous species can birth various amounts of offspring at a time, but the exact number of offspring depends on the size and species of snake. ==Classification==

In the past, the Colubridae were not a natural group, as many were more closely related to other groups, such as elapids, than to each other. This family was historically used as a "wastebasket taxon" Until recently, colubrids were basically colubroids that were not elapids, viperids, or Atractaspis. However, recent research in molecular phylogenetics has stabilized the classification of historically "colubrid" snakes and the family as currently defined is a monophyletic clade, although additional research will be necessary to sort out all the relationships within this group. As of May 2018, eight subfamilies are recognized. Current subfamilies Sibynophiinae – three genera Natricinae – 36 genera (sometimes given as family Natricidae) (grey and yellow) , Thamnophis sirtalis Pseudoxenodontinae – two genera Dipsadinae – over 100 genera (sometimes given as family Dipsadidae) , Sibon longifrenis Grayiinae – one genus • Grayia Calamariinae – seven genera Ahaetuliinae – five genera Colubrinae – 93 genera , Dolichophis jugularis, preying on a legless lizard, a sheltopusik Sub-family currently undetermined Former subfamilies These taxa have been at one time or another classified as part of the Colubridae, but are now either classified as parts of other families, or are no longer accepted because all the species within them have been moved to other (sub)families. • Subfamily Aparallactinae (now a subfamily of Lamprophiidae, • Subfamily Philothamninae (now part of Colubrinae) • Subfamily Psammophiinae (now a subfamily of Lamprophiidae) • Subfamily Pseudoxyrhophiinae (now a subfamily of Lamprophiidae) • Subfamily Xenoderminae (now family Xenodermidae, sometimes incorrectly spelled Xenodermatidae) • Subfamily Xenodontinae (which many authors put in Dipsadinae/Dipsadidae) ==Fossil record==

The oldest colubrid fossils are indeterminate vertebrae from Thailand and specimens of the genus Nebraskophis from the U.S. state of Georgia, both from the Late Eocene. The presence of derived colubrids in North America so early on, despite their presumed Old World origins, suggests that they originated even earlier. ==References==