Najash

Najash Temporal range: Late Cretaceous, 90  Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Sacral region of the holotype of the “legged snake” Najash rionegrina
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Clade:	Ophidia
Genus:	† Najash Apesteguía & Zaher, 2006
Type species
Najash rionegrina Apesteguía & Zaher, 2006

Najash is an extinct genus of basal snake from the Late Cretaceous Candeleros Formation of Patagonia. ^[1] Like a number of other Cretaceous and living snakes it retained hindlimbs, but Najash is unusual in having well-developed legs that extend outside the rib cage, and a pelvis connected to the spine.

Discovery and description

Fossils of Najash were found in the terrestrial Candeleros Formation, in Rio Negro Province, Argentina, and date to roughly 90 million years ago. The skull and spine of Najash show primitive features that resemble other Cretaceous snakes, such as Dinilysia patagonica and Madtsoiidae. ^[2] Also, several characteristics of the neck and tail of Najash and Dinilysia patagonica show how the body plan of snakes evolved from a lizard-like ancestor. ^[3]

Najash 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. ^[4] Nearly all phylogenetic analyses place Najash as an early offshoot of the snake tree, outside of all living snakes. ^{[1] [2] [3] [5]}

Ecology

The cranial morphology of Najash suggests that it had only limited unilateral movements of the mandibles, and lacked the attributes of macrostomatan snakes to ingest large prey, Apesteguía suggests, presumably based on the associated fauna, that this snake preyed on a variety of small vertebrates, such as ‘lizards’, micro-mammals and dinosaur hatchlings. This assumption is well supported by the snake body size. ^[6]

References

1. Apesteguía, S.; Zaher, H. (2006). "A Cretaceous terrestrial snake with robust hindlimbs and a sacrum". Nature . 440 (7087): 1037–1040. Bibcode:2006Natur.440.1037A. doi:10.1038/nature04413. PMID   16625194. S2CID   4417196.
2. Garberoglio, Fernando F.; Gómez, Raúl O.; Apesteguía, Sebastián; Caldwell, Michael W.; Sánchez, María L.; Veiga, Gonzalo (2019-02-04). "A new specimen with skull and vertebrae of Najash rionegrina (Lepidosauria: Ophidia) from the early Late Cretaceous of Patagonia". Journal of Systematic Palaeontology. 17 (18): 1313–1330. Bibcode:2019JSPal..17.1533G. doi:10.1080/14772019.2018.1534288. ISSN   1477-2019. S2CID   91780191.
3. Garberoglio, Fernando F.; Gómez, Raúl O.; Simões, Tiago R.; Caldwell, Michael W.; Apesteguía, Sebastián (2019). "The evolution of the axial skeleton intercentrum system in snakes revealed by new data from the Cretaceous snakes Dinilysia and Najash". Scientific Reports. 9 (1): 1276. Bibcode:2019NatSR...9.1276G. doi:10.1038/s41598-018-36979-9. ISSN   2045-2322. PMC   6362196 . PMID   30718525.
4. Other known fossil snakes with developed hindlimbs, Haasiophis , Pachyrhachis and Eupodophis —all found in marine environments—all lack a sacral region.
5. Longrich, N. R.; Bhullar, B.-A. S.; et al. (2012). "A transitional snake from the Late Cretaceous period of North America" (PDF). Nature. 488 (7410): 205–208. Bibcode:2012Natur.488..205L. doi:10.1038/nature11227. PMID   22832579. S2CID   4411744.
6. Adriana M. Albino (2011). "Evolution of Squmata Reptiles in Patagonia based on the fossil record". Biological Journal of the Linnean Society. 103 (2): 441–457. doi:10.1111/j.1095-8312.2011.01691.x.

External links

• Pelvic region of a Najash fossil