Topic
Najash
About: Najash is a research topic. Over the lifetime, 11 publications have been published within this topic receiving 491 citations.
Papers
TL;DR: The new fossil from the Upper Cretaceous period of Patagonia fills an important gap in the evolutionary progression towards limblessness and retains several features associated with a subterranean or surface dwelling life that are also present in primitive extant snake lineages, supporting the hypothesis of a terrestrial rather than marine origin of snakes.
Abstract: It has commonly been thought that snakes underwent progressive loss of their limbs by gradual diminution of their use. However, recent developmental and palaeontological discoveries suggest a more complex scenario of limb reduction, still poorly documented in the fossil record. Here we report a fossil snake with a sacrum supporting a pelvic girdle and robust, functional legs outside the ribcage. The new fossil, from the Upper Cretaceous period of Patagonia, fills an important gap in the evolutionary progression towards limblessness because other known fossil snakes with developed hindlimbs, the marine Haasiophis, Pachyrhachis and Eupodophis, lack a sacral region. Phylogenetic analysis shows that the new fossil is the most primitive (basal) snake known and that all other limbed fossil snakes are closer to the more advanced macrostomatan snakes, a group including boas, pythons and colubroids. The new fossil retains several features associated with a subterranean or surface dwelling life that are also present in primitive extant snake lineages, supporting the hypothesis of a terrestrial rather than marine origin of snakes.
190 citations
TL;DR: Najash rionegrina documents an important gap in the evolutionary development towards limblessness, because its phylogenetic affinities suggest that it is the sister group of all modern snakes, including the limbed Tethyan snakes Pachyrhachis, Haasiophis, and Eupodophis.
70 citations
TL;DR: Following the reevaluation of the anatomy of the type specimen and the removal from this taxon of the above-mentioned referred material, the phylogenetic analyses found no support for the hypothesis that Najash rionegrina occupies a position as the most basal snake.
Abstract: —The fossil snake Najash rionegrina, from the Cenomanian–Turonian (Upper Cretaceous) of Argentina, is reinterpreted after examination of the type and referred material. The current diagnosis is emended in the light of important considerations that cast doubt on the attribution of type and referred specimens (a braincase, a quadrate, and two dentary/lower jaw fragments) used to systematize this taxon. Alternative interpretations of the anatomy of the sacrum and hind limbs are proposed. Following the reevaluation of the anatomy of the type specimen and the removal from this taxon of the above-mentioned referred material, the phylogenetic position of N. rionegrina was tested in a series of maximum parsimony analyses that included all groups of extant snakes, all best-known fossil snakes (i.e., Pachyrhachis, Haasiophis, Eupodophis, Madtsoiidae, and Dinilysia), and alternative outgroups. Regardless of the outgroup used to polarize the character-state transformations, our phylogenetic analyses found no ...
31 citations
TL;DR: Seismophis septentrionalis as discussed by the authors is a snake genus and species from the Cenomanian (early Late Cretaceous) of the Alcântara Formation, Maranhao, northeastern Brazil.
Abstract: South American Mesozoic snake diversity is mostly represented by genera from the Cenomanian (Najash), Santonian— Campanian (Dinilysia), and Campanian—Maastrichtian (Alamitophis, Patagoniophis, Rionegrophis, and Australophis) of Patagonia, Argentina. In this paper, we describe a new snake genus and species, Seismophis septentrionalis, from the Cenomanian (early Late Cretaceous) of the Alcântara Formation, Maranhao, northeastern Brazil. The new snake comprises a posteriormost trunk vertebra and possibly a poorly preserved midtrunk vertebra. Both vertebrae share small size, zygosphene moderately thick with a rectilinear roof, absence of paracotylar foramina, presence of parazygantral foramina, and strongly marked parasagittal ridges of the neural arch. The new snake is here considered of uncertain systematic affinities, but probably close to the limbed snake Najash rionegrina. Although the material is very fragmentary and the systematic assignment is still unresolved, this snake represents the oldest, as wel...
24 citations
TL;DR: The dentary was found associated with several isolated snake vertebrae, most of which are referable to madt soiids, thus it probably belongs to one of the already known madtsoiid taxa.
Abstract: The first snake craniomandibular fossil specimen from the Campanian–Maastrichtian of South America is described herein. The specimen, from the Allen Formation in Rio Negro Province, consists of an incomplete anterior portion of a left dentary. The general morphology of the bone resembles that of the basal legged snake Najash Apesteguia and Zaher and the small madtsoiids from the Eocene–Miocene of Australia. The dentary was found associated with several isolated snake vertebrae, most of which are referable to madtsoiids, thus it probably belongs to one of the already known madtsoiid taxa.
8 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2019 | 3 |
| 2017 | 1 |
| 2015 | 1 |
| 2013 | 2 |
| 2012 | 1 |
| 2011 | 1 |