page_title: Helveticosaurus
section_title: Relationship with other sauropsids
hierarchical_section_title: Helveticosaurus / Relationship with other sauropsids
caption_attribution_description: Deutsch: Künstlerische Interpretation von Helveticosaurus. English: Artist's depiction of Helveticosaurus.
context_page_description: Helveticosaurus is an extinct genus of diapsid marine reptile known from the Middle Triassic of southern Switzerland. It contains a single species, Helveticosaurus zollingeri, known from the nearly complete holotype T 4352 collected at Cava Tre Fontane of Monte San Giorgio, an area well known for its rich record of marine life during the Middle Triassic.
context_section_description: Upon its naming and description in 1955, Helveticosaurus was classified as a member of the order Placodontia, a group of robust, barrel-bodied marine reptiles similar in lifestyle to the extant marine iguana. It was seen as a basal member of the clade, being assigned to the new family Helveticosauridae of the Helveticosauroidea superfamily.
  Despite the dorsal vertebrae, which are very similar to those of placodonts, the genus lacks many of the autapomorphies characteristic of sauropterygians and thus evolved from a different ancestor, independently adapting a marine lifestyle.    
   
  Its affinities with other diapsids are unclear, as it differs greatly from any other known types of marine reptiles, with no apparent close relatives. It shares some characteristics with archosauromorphs, and may be related to that group. One 2013 analysis of fossil reptile relationships found Helveticosaurus, together with Eusaurosphargis and Saurosphargis, to be most closely related to either the ichthyopterygians or sauropterygians in a large clade of marine reptiles within archosauromorpha. Most recent phylogenetic analyses recover a sister taxon relationship between Helveticosaurus and Eusaurosphargis, with one analysis recovering them at successive positions instead. The following cladogram is simplified after the phylogenetic analysis of Li et al. (2014), which includes Eusaurosphargis, Helveticosaurus and all known saurosphargid species. The removal / inclusion of Ichthyopterygia was found to affect the topology the most - switching the positions of the Eusaurosphargis+Helveticosaurus and Thalattosauriformes clades, and altering the positions of several taxa within Eosauropterygia, which are not shown.
caption: Restoration by Darren Naish.
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