Purranisaurus potens is known from a single partial specimen from
the left margin of the Arroyo del Cajón Grande in southeast Malargüe
Department, Mendoza Province, in the Neuquún Basin of west-central Argentina.
It was first described in 1948 as a Plesiosaur, then reclassified as a
Nothosaur in 1967. Since this time it has generally been considered to be a Metriorhynchid
Thalattosuchian, a sort of Mesozoic Marine Crocodyliform, and a close
relationship to two Chilean species, Metriorhynchus
casamiquelai and Metriorhynchus
westermanni, and it has been suggested that the three species be placed in
a single genus, though these analyses have been based upon photographs and
descriptions from the original papers describing the specimen, rather than
re-examination of the material.
In a paper published in the
Journal of Vertebrate Paleontology on 20 February 2015, Yanina Herrera, Zulma
Gasparini and Marta Fernández of the División Paleontología Vertebrados at the
Museo de La Plata at the Universidad Nacional de La Plata redescribe the Purranisaurus potens, following
repreparation of the original specimen at the Museo de La Plata during which
more of the skull was exposed from the matrix.
The single known specimen of Purranisaurus potens comprises a
three-dimensionally preserved skull with damage to the orbital region (area
around the eyes) caused by post-mortem compression, as well as a partial left
lower jaw. The original description also included several ribs and vertebrae,
however these could not be located and appear to have been lost.
Purranisaurus potens in left
lateral view. (A) Photograph; (B) line interpretation. Abbreviations: eor,
external otic recess; fr, frontal; gd, nasal gland duct; j, jugal; la,
lacrimal; ls, laterosphenoid; mx, maxilla; na, nasal; or, orbit; pa, parietal;
pfr, prefrontal; po, postorbital; pro, prootic; q, quadrate; sq, squamosal;
sqs, squamosal flat surface. Scale bar equals 10 cm. Herrera et al. (2015).
Based upon the new description
Herrera et al. were able to
re-analyse the phylogenetic position of Purranisaurus
potens. This new analysis suggests that the species belongs firmly within
the Geosaurine group of Metriorhynchids, and shows no close relationship with Metriorhynchus casamiquelai
and Metriorhynchus westermanni, and
the true relationships of these two species remains unclear, with Herrera et al.’s analysis suggesting they occupy
a basal position within the Geosaurinae, and are not closely related to other
members of the genus Metriorhynchus.
Strict consensus topology of the unordered phylogenetic analysis.
Herrera et al. (2015).
See also…
The Rosso Ammonitico Veronese is a red nodular limestone found on the Trento Plateau in northern Italy, and Middle to Late Jurassic in age. It is noted for its numerous Ammonite fossils, but also produces occasional Marine Reptiles, notably Thalattosuchian Crocodylomorphs and Plesiosaurians. The earliest recorded discovery of such a Reptile is a...
The Thalattosuchians were a group of marine Crocodiliformes (the group of Archosaurs that includes modern Crocodiles and a diverse range of Mesozoic animals) that were found in seas around the world from the Early Jurassic to the Early Cretaceous. They...
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