Najash rionegrina
Encyclopedia
Najash is an extinct genus
of basal
snake
. Like a number of other Cretaceous
snakes (see below), it had two hind-limbs. The fossils were found in a land-based deposit, and the robust backbone vertebrae and rear legs of the snake were adapted to a burrowing, subterranean environment. This is significant, as it suggests that snakes had a terrestrial
origin, and presents new evidence in the complicated sequences that led to limb reduction and loss as snakes developed from their lizard
ancestors.
The snake was no more than 1.5 meters (5 feet) long, and lived during the Late Cretaceous
period (ca. 90 million years ago) in what is now the Rio Negro province (hence its specific name rionegrina) of Patagonia
, Argentina
.
This burrowing creature had not lost its sacrum
, the pelvic bone composed of several fused vertebrae, nor its pelvic girdle which are absent in modern snakes, and in all other known fossil snakes as well.
This discovery does not support the hypothesis, first offered by the nineteenth-century paleontologist Edward Drinker Cope
, that snakes share a common marine ancestry with mosasaur
s. The marine origin hypothesis received new impetus with the discovery in the 1990s of basal snakes with vestigial limbs in marine sediments in Lebanon.
The generic name comes from the biblical legged snake of Genesis, Nahash, who tempted Adam and Eve
to eat from a forbidden fruit tree.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
snake
Snake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...
. Like a number of other Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
snakes (see below), it had two hind-limbs. The fossils were found in a land-based deposit, and the robust backbone vertebrae and rear legs of the snake were adapted to a burrowing, subterranean environment. This is significant, as it suggests that snakes had a terrestrial
Terrestrial animal
Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...
origin, and presents new evidence in the complicated sequences that led to limb reduction and loss as snakes developed from their lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...
ancestors.
The snake was no more than 1.5 meters (5 feet) long, and lived during the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
period (ca. 90 million years ago) in what is now the Rio Negro province (hence its specific name rionegrina) of Patagonia
Patagonia
Patagonia is a region located in Argentina and Chile, integrating the southernmost section of the Andes mountains to the southwest towards the Pacific ocean and from the east of the cordillera to the valleys it follows south through Colorado River towards Carmen de Patagones in the Atlantic Ocean...
, Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
.
This burrowing creature had not lost its sacrum
Sacrum
In vertebrate anatomy the sacrum is a large, triangular bone at the base of the spine and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two hip bones. Its upper part connects with the last lumbar vertebra, and bottom part with the coccyx...
, the pelvic bone composed of several fused vertebrae, nor its pelvic girdle which are absent in modern snakes, and in all other known fossil snakes as well.
This discovery does not support the hypothesis, first offered by the nineteenth-century paleontologist Edward Drinker Cope
Edward Drinker Cope
Edward Drinker Cope was an American paleontologist and comparative anatomist, as well as a noted herpetologist and ichthyologist. Born to a wealthy Quaker family, Cope distinguished himself as a child prodigy interested in science; he published his first scientific paper at the age of nineteen...
, that snakes share a common marine ancestry with mosasaur
Mosasaur
Mosasaurs are large extinct marine lizards. The first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764...
s. The marine origin hypothesis received new impetus with the discovery in the 1990s of basal snakes with vestigial limbs in marine sediments in Lebanon.
The generic name comes from the biblical legged snake of Genesis, Nahash, who tempted Adam and Eve
Adam and Eve
Adam and Eve were, according to the Genesis creation narratives, the first human couple to inhabit Earth, created by YHWH, the God of the ancient Hebrews...
to eat from a forbidden fruit tree.