![]() Early in snake evolution, the Hox gene expression in the axial skeleton responsible for the development of the thorax became dominant. The axial skeleton of the snakes’ common ancestor, like most other tetrapods, had regional specializations consisting of cervical (neck), thoracic (chest), lumbar (lower back), sacral (pelvic), and caudal (tail) vertebrae. This is caused by the evolution of Hox genes, controlling limb morphogenesis. The earliest known true snake fossils (members of the crown group Serpentes) come from the marine simoliophiids, the oldest of which is the Late Cretaceous (Cenomanian age) Haasiophis terrasanctus, dated to between 112 and 94 million years old.īased on comparative anatomy, there is consensus that snakes descended from lizards. Pythons and boas-primitive groups among modern snakes-have vestigial hind limbs: tiny, clawed digits known as anal spurs, which are used to grasp during mating. The families Leptotyphlopidae and Typhlopidae also possess remnants of the pelvic girdle, appearing as horny projections when visible.įront limbs are nonexistent in all known snakes. Fossils readily identifiable as snakes (though often retaining hind limbs) first appear in the fossil record during the Cretaceous period. The fossil record of snakes is relatively poor because snake skeletons are typically small and fragile making fossilizationuncommon. The other term, serpent, is from French, ultimately from Indo-European *serp- (to creep), which also gave Ancient Greek hérpō (ἕρπω) "I crawl". The English word snake comes from Old English snaca, itself from Proto-Germanic *snak-an- (cf. Germanic Schnake "ring snake", Swedish snok "grass snake"), from Proto-Indo-European root *(s)nēg-o- "to crawl", "to creep", which also gave sneak as well as Sanskrit nāgá "snake". The word ousted adder, as adder went on to narrow in meaning, though in Old English næddre was the general word for snake. Nonvenomous snakes either swallow prey alive or kill by constriction. Some possess venom potent enough to cause painful injury or death to humans. Most species are nonvenomous and those that have venom use it primarily to kill and subdue prey rather than for self-defense. The oldest preserved descriptions of snakes can be found in the Brooklyn Papyrus. The diversity of modern snakes appeared during the Paleocene period ( c66 to 56 Ma ago). The fossil species Titanoboa cerrejonensiswas 12.8 meters (42 ft) long. Snakes are thought to have evolved from either burrowing or aquatic lizards, perhaps during the Jurassic period, with the earliest known fossils dating to between 143 and 167 Ma ago. More than 20 families are currently recognized, comprising about 500 genera and about 3,400 species. They range in size from the tiny, 10.4 cm-long thread snake to the reticulated python of 6.95 meters (22.8 ft) in length. Living snakes are found on every continent except Antarctica, and on most smaller land masses exceptions include some large islands, such as Ireland, Iceland, Greenland, the Hawaiian archipelago, and the islands of New Zealand, and many small islands of the Atlantic and central Pacific oceans. Additionally, sea snakes are widespread throughout the Indian and Pacific Oceans. Some species retain a pelvic girdle with a pair of vestigial claws on either side of the cloaca. To accommodate their narrow bodies, snakes' paired organs (such as kidneys) appear one in front of the other instead of side by side, and most have only one functional lung. Many species of snakes have skulls with several more joints than their lizard ancestors, enabling them to swallow prey much larger than their heads with their highly mobile jaws. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. However, they both ultimately stem from Proto-Indo-European *sneg- meaning "to crawl, a creeping thing". The word "snake" comes from Middle English snake which comes from Old English snaca which is descended from Proto-Germanic * snakô (hence Icelandic snákur). Snakes are elongated, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. A Black Mamba, the fastest snake on Earth ![]()
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