| Eusaurosphargis | |
|---|---|
 | |
| Eusaurosphargis dalsassoi PIMUZ A/III 4380 | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Family: | †Helveticosauridae |
| Genus: | †Eusaurosphargis Nosotti & Rieppel2003 |
| Species: | †E. dalassoi |
| Binomial name | |
| †Eusaurosphargis dalassoi Nosotti & Rieppel 2003 | |
Eusaurosphargis is anextinctgenus of adiapsid reptile, known from theMiddle Triassic (Anisian andLadinian age)Besano Formation of northernItaly andProsanto Formation of south-easternSwitzerland. It contains asingle species,Eusaurosphargis dalsassoi.[1] It was a small reptile, measuring 20 cm (7.9 in) long.[2]
Theholotype ofEusaurosphargis dalsassoi (BES SC 390) is a partialskeleton of a single individual found disarticulated but in close association. BES SC 390 was collected from an oil shale at Cava di Besano of theBesano Formation (Grenzbitumenzone). Theselagoonal beds are equivalent to those atMonte San Giorgio, dating to theAnisian-Ladinian boundary, probably to the latest Anisian at this location, of the earlyMiddle Triassic, about 243million years ago.[1] Nicole Klein and Oliver J. Sichelschmidt (2014) described disarticulated remains they referred toEusaurosphargis sp. These remains were collected from theDutchWinterswijk Quarry III of theVossenveld Formation, dating to the late Anisian stage.[3]
A new, complete and almost entirely-articulated specimen was described in 2017 from Ducanfurgga, nearDavos,Canton Grisons (Graubünden) in Swiss Alps (PIMUZ A/III 4380).[4] This specimen is of a juvenile and displays extensiveosteoderm armor and morphology that indicates that the animal was not aquatic as previously thought. Although a semi-aquatic lifestyle was not ruled out.
Eusaurosphargis was first described and named by Stefania Nosotti and Olivier Rieppel in2003 and thetype species isEusaurosphargis dalsassoi. Thegeneric name is derived fromGreekeu, meaning "true/well",sauros, meaning "lizard", andsphargis, the old genus name for theleatherback turtle, in reference to the many similaritiesEusaurosphargis shares withSaurosphargis, a taxon whose holotype was lost and was thus considered a mystery. Like the name ofSaurosphargis itself, it also refers toEusaurosphargis appear haveseemingly transitional traits betweenturtles and other reptiles. Thespecific namedalsassoi honors the paleontologistCristiano Dal Sasso at theMilan Natural History Museum who was the first to realize the importance of BES SC 390.[1]
Eusaurosphargis was first included in aphylogenetic analysis in its original description. Nosotti and Rieppel (2003) recovered it as thesister taxon ofHelveticosaurus, and based on the description in the literature available forSaurosphargis (whose holotype is lost), they considered it to fall in the sameclade. This group was found to be the sister-group of the clade that comprisesthalattosauriforms andsauropterygians.[1]
The anatomy ofSaurosphargis was finally clarified by comparisons with the well-preserved specimens ofSinosaurosphargis, and as a resultSaurosphargis was no longer considered to be anomen dubium, and thus could be included in a phylogenetic analysis. Liet al. (2011) foundSaurosphargis andSinosaurosphargis to form a clade separate from that ofEusaurosphargis andHelveticosaurus, which they termedSaurosphargidae.[5] The followingcladogram is simplified after the phylogenetic analysis of Liet al. (2014), which includesEusaurosphargis,Helveticosaurus and all known saurosphargid species. The removal / inclusion ofIchthyopterygia was found to affect thetopology the most - switching the positions of theEusaurosphargis+Helveticosaurus andThalattosauriformes clades, and altering the positions of several taxa withinEosauropterygia, which are not shown.[6]
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