Helveticosaurus

Helveticosaurus; Temporal range: Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
	Fossil at Paleontology Museum of Zurich
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Archosauromorpha (?)
Family:	†Helveticosauridae
Genus:	†Helveticosaurus; Peyer, 1955
Type species
	†Helveticosaurus zollingeri; Peyer, 1955 (type)

Helveticosaurus is an

extinct genus of diapsid marine reptile known from the Middle Triassic (Anisian-Ladinian boundary) 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.^[1]

Description and paleobiology

Helveticosaurus is known from a nearly complete

thalattosaurs, and it probably propelled itself through the water by means of lateral undulation. However, Helveticosaurus also possessed a robust pectoral girdle and forelimbs that were well adapted for paddle like propulsion as a supplementary method of locomotion, as seen in secondarily aquatic tetrapods

. This unique combination of undulation and paddling is highly unusual for an aquatic reptile.

The caniniform teeth suggest a predatory lifestyle for Helveticosaurus. Unlike most other marine reptiles which exhibited a lengthening and narrowing of the skull, the head of Helveticosaurus was more robust and boxlike. It is unknown what purpose the shortness of the skull would have had in feeding.[3]

Relationship with other sauropsids

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.^[1]

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

Eosauropterygia, which are not shown.^[6]

	Helveticosaurus zollingeri

	Eusaurosphargis dalsassoi

Sauropterygia

	Placodontia

	Eosauropterygia

Saurosphargidae

	Largocephalosaurus polycarpon

	Largocephalosaurus qianensis

	Saurosphargis volzi

	Sinosaurosphargis yunguiensis

Possible relatives

Pelvic material from SVT 203, found from older

phalanges suggest that it is not from an ichthyopterygian

, therefore making it more probable that it belongs to a taxon related, and possibly ancestral, to Helveticosaurus, although more material is needed to give a definitive confirmation. The small size of material comprising SVT 203 in relation to Helveticosaurus, along with the compression seen on both ends of the femur, may indicate that it is a juvenile form of the species to which it belongs, but both temporal and geographical separation of SVT 203 with Helveticosaurus makes size comparison as a means of determining immaturity unnecessary, as it is possible that Helveticosaurus evolved from an ancestor that was smaller in overall size.

References

^ ^a ^b ^c Bernhard Peyer (1955). "Die Triasfauna der Tessiner Kalkalpen. XVIII. Helveticosaurus zollingeri, n.g. n.sp". Schweizerische Paläontologische Abhandlungen. 72: 3–50.
S2CID 252750395
.

^ Naish, D. (2008). "One of so many bizarre Triassic marine reptiles." Weblog entry. Tetrapod Zoology. 13 September 2008. Accessed 24 July 2009.

^
PMID 23535642
.

S2CID 130698779
.

^
S2CID 84534618
.

doi:10.1111/1475-4983.00115
.

^ Mazin, J.-M. (1981). "Grippia longirostris Wiman, 1929, un Ichthyopterygia primitif du Trias inférieur du Spitsberg". Bulletin du Muséum National d'Histoire Naturelle. 4: 317–340.

External links

Helveticosaurus in the Paleobiology Database

Tetrapod Zoology post on Helveticosaurus

Paleontology portal

Retrieved from "https://en.wikipedia.org/w/index.php?title=Helveticosaurus&oldid=1218558802"

[Helveticosaurus-1] Bernhard Peyer (1955). "Die Triasfauna der Tessiner Kalkalpen. XVIII. Helveticosaurus zollingeri, n.g. n.sp". Schweizerische Paläontologische Abhandlungen. 72: 3–50.

[2] S2CID 252750395
.

[3] Naish, D. (2008). "One of so many bizarre Triassic marine reptiles." Weblog entry. Tetrapod Zoology. 13 September 2008. Accessed 24 July 2009.

[Palatodonta-4] 
PMID 23535642
.

[Sinosaurosphargis-5] S2CID 130698779
.

[L.qianensis-6] 
S2CID 84534618
.

[7] :10.1111/1475-4983.00115
.

[8] Mazin, J.-M. (1981). "Grippia longirostris Wiman, 1929, un Ichthyopterygia primitif du Trias inférieur du Spitsberg". Bulletin du Muséum National d'Histoire Naturelle. 4: 317–340.

[1]

[6]