''Pachyrhachis'' (from el, παχύς , 'thick' and el, ῥάχῐς , 'spine') is an
extinct
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
of
snake
Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more ...
with well developed hind legs known from
fossils
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
discovered in
Ein Yabrud
Ein Yabrud ( ar, عين يبرود) is a Palestinian people, Palestinian town in the Ramallah and al-Bireh Governorate in the central West Bank. It is located approximately 7 km northeast of the city of Ramallah and its elevation is 800 m ...
, near
Ramallah
Ramallah ( , ; ar, رام الله, , God's Height) is a Palestinian city in the central West Bank that serves as the ''de facto'' administrative capital of the State of Palestine. It is situated on the Judaean Mountains, north of Jerus ...
, in the central
West Bank
The West Bank ( ar, الضفة الغربية, translit=aḍ-Ḍiffah al-Ġarbiyyah; he, הגדה המערבית, translit=HaGadah HaMaʽaravit, also referred to by some Israelis as ) is a landlocked territory near the coast of the Mediter ...
. It is a relatively small snake, measuring more than long at maximum.
''Pachyrhachis'' appears to have been an ancient marine snake; the fossils occur in a marine limestone deposit, and the thickened bone of the ribs and vertebrae would have functioned as ballast to decrease the buoyancy of the animal, allowing it to dive beneath the ancient Cretaceous seas that it once inhabited.
''Pachyrhachis'' is one of three genera of
Cenomanian
The Cenomanian is, in the ICS' geological timescale, the oldest or earliest age of the Late Cretaceous Epoch or the lowest stage of the Upper Cretaceous Series. An age is a unit of geochronology; it is a unit of time; the stage is a unit in ...
snakes with hindlimbs. Although many modern
pythons
The Pythonidae, commonly known as pythons, are a family of nonvenomous snakes found in Africa, Asia, and Australia. Among its members are some of the largest snakes in the world. Ten genera and 42 species are currently recognized.
Distribution ...
and
boas still retain remnants of legs, in the form of small spurs, the tiny legs of Pachyrhachis included a hip, knee, and ankle joint. ''Pachyrhachis'' was originally described by Haas (1979, 1980) who noted it had a puzzling melange of snake and lizard features; its status as an early snake was later confirmed (Caldwell and Lee 1997).
The position of ''Pachyrhachis'' within snakes has been debated (e.g. Lee and Scanlon 2002; Rieppel et al. 2003). ''Pachyrhachis'' is among the oldest known snakes and retains well-developed hind limbs, suggesting it represented a transitional form linking snakes to marine lizards (Lee and Scanlon 2002), though other studies place ''Pachyrhachis'' within the modern snake radiation
Macrostomata (Zaher & Rieppel, 1999).
See also
Other known fossil snakes with legs:
*''
Eupodophis
''Eupodophis'' is an extinct genus of snake from the Late Cretaceous period. It has two small hind legs and is considered a transitional form between Cretaceous lizard
Lizards are a widespread group of squamate reptiles, with over 7,000 sp ...
''
*''
Haasiophis''
*''
Najash
''Najash'' is an extinct genus of basal snake from the Late Cretaceous Candeleros Formation of Patagonia. Like a number of other Cretaceous and living snakes it retained hindlimbs, but ''Najash'' is unusual in having well-developed legs that e ...
''
*''
Tetrapodophis''
References
* Caldwell, M. W. & Lee, M. S. Y. (1997). A snake with legs from the marine Cretaceous of the Middle East. Nature 386: 705–709.
* Haas, G. 1979 On a new snakelike reptile from the Lower Cenomanian of Ein Jabrud, near Jerusalem. Bull. Mus. Nat. Hist. Nat., Paris, Ser. 4, 1, 51–64.
* Haas, G. 1980 Pachyrhachis problematicus Haas, snakelike reptile from the Lower Cenomanian: ventral view of the skull. Bull. Mus. Nat. Hist. Nat., Paris, Ser. 4, 2:87-104.
* Haas, G. 1980 Remarks on a new ophiomorph reptile from the Lower Cenomanian of Ein Jabrud, Israel. In Aspects of Vertebrate History, in Honor of E.H. Colbert (ed. L.L. Jacobs), pp. 177–102. Flagstaff AZ: Museum of Northern Arizona Press.
* Lee, M.S.Y. and Caldwell, M.W. 1998. Anatomy and relationships of Pachyrhachis, a primitive snake with hindlimbs. Philosophical Transactions of the Royal Society of London: Biological Sciences 353: 1521–1552.
* Lee, M.S.Y., Scanlon, J.D. 2002. Snake phylogeny based on osteology, soft anatomy and behaviour. Biological Reviews 77: 333–401.
* et al. 2003 "The Anatomy and Relationships of Haasiophis terrasanctus, a Fossil Snake with Well-Developed Hind Limbs from the Mid-Cretaceous of the Middle East" ''Journal of Paleontology'' 77(3):536-558
* Scanlon, J.D., Lee, M.S.Y., Caldwell, M.W. and Shine, R. 1999. Paleoecology of the primitive snake Pachyrhachis. Historical Biology 13: 127–152.
External links
Picture
Cretaceous snakes
Late Cretaceous reptiles of Asia
Transitional fossils
Fossil taxa described in 1979
Fossils of Palestine
{{snake-stub