Helveticosaurus zollingeri is an unusual and poorly known diapsid from the Middle Triassic rocks of Monte san Giorgio, Switzerland. First described in 1955, it was initially identified as a primitive placodont and regarded as the only representative of the basal placodont group Helveticosauroidea. But this isn’t correct and Helveticosaurus lacks the features unique to both Placodontia and to Sauropterygia (Rieppel 1989).
Helveticosaurus was long-bodied and it had a long, flexible tail and – like mesosaurs, claudiosaurs, thalattosaurs and hupehsuchians – it was probably an axial undulatory swimmer. However, its pectoral girdle was robust, and in its forelimbs it exhibited several features commonly seen in secondarily aquatic tetrapods (SATs) that use their limbs as paddles or wings. Helveticosaurus therefore seems to have combined axial undulatory swimming with a rowing or flying motion of the forelimbs. It may therefore have exhibited an extremely unusual style of swimming. In marked contrast to that of most marine reptiles, the skull of Helveticosaurus is short and box-like, and it’s not immediately clear what it was doing with this skull, or what it was feeding on. Its long caniniform teeth show that was most likely a predator, but – as to what it was preying on – we have no idea.
Helveticosaurus is the only known member of its lineage and it doesn’t possess any obvious close relatives (although a pelvis from the Lower Triassic of Spitsbergen might represent a close relative: see the comments below). It does however exhibit several features unique to archosauromorphs and it probably fitted somewhere into this diapsid clade, though exactly where we don’t really know (I’d like to know if John Merck’s thesis included information on it).
Incidentally, I tried googling Helveticosaurus. The screen-capture included above shows the results. Virtually everything traces back to stuff I’ve done (including the astrapothere and tapir stuff). How embarrassing – is no-one else interested? You might think that you’ve never seen a photo of Helveticosaurus. However, if you own Mike Benton’s The Reign of the Reptiles (Kingfisher Books, 1990), there’s an excellent colour photo of the only known specimen on p. 114… unfortunately it’s labelled as ‘the nothosaur Ceresiosaurus‘, so most people have missed it. The life restoration shown above was originally posted here and there have been a few requests for further info. The text you’ve just read was recycled from a talk script (the talk was this one), so was one of those ‘post something quickly with minimum effort’ articles.
Refs – -
Rieppel, O. 1989. Helveticosaurus zollingeri Peyer (Reptilia, Diapsida): skeletal paedomorphosis; functional anatomy and systematic affinities. Palaeontographica A 208, 123-152.