| Saurosphargids | |
|---|---|
 | |
| Life reconstruction ofSinosaurosphargis | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | †Saurosphargiformes |
| Family: | †Saurosphargidae Liet al.,2011 |
| Genera | |
Saurosphargidae is anextinctfamily ofmarine reptiles known from theEarly Triassic (Olenekian stage) and earlyMiddle Triassic (Anisian stage) ofEurope andChina.[1][2][3]
Thetype genus of the family isSaurosphargis, named byFriedrich von Huene in 1936 based on a single specimen collected from the lower AnisianLower Muschelkalk of Gogolin,Poland -- a section of 12 incompleteback vertebrae withribs. Thegeneric name ofSaurosphargis is derived fromGreeksauros, "lizard," andsphargis, the old genus name for theleatherback turtle, in reference to the dorsalosteoderm "body armor" and broadened ribs forming a closed chest rib basket, traits that are seemingly transitional betweenturtles and other reptiles. However, due to the only known specimen' destruction duringWorld War II, many authors consideredSaurosphargis to be anomen dubium. Nevertheless, even based on surviving descriptions alone, many differences were noted even from its closest known relative at the time,Eusaurosphargis dalsassoi from the Anisian-Ladinian boundary of the southernAlps. Various hypotheses existed for the affinities of these species, and together withHelveticosaurus, they were originally thought to beplacodonts, but later studies suggested relatedness to othersauropterygians and / orichthyopterygians.[1]
It wasn't until nearly a century after the discovery ofSaurosphargis, that other specimens closely related to it were found inChina. In 2011, Liet al. described and named three of these specimens,Sinosaurosphargis yunguiensis, referring to this species being the Chinese version ofSaurosphargis. The specimens ofSinosaurosphargis were collected from Member II of theGuanling Formation, dating to the Pelsonian (mid-lateAnisian). Based on very detailed descriptions and figures ofSaurosphargis in Huene (1936), and based on comparisons with the well-preservedSinosauropshargis, Liet al. (2011) resurrectedSaurosphargis volzi as a valid species, and erected the family Saurosphargidae to contain the two. Furthermore, they reported the discovery of material referable toSaurosphargis from the Lower Muschelkalk ofWinterswijk, theNetherlands, that is under preparation.Saurosphargis andSinosaurosphargis were included in aphylogenetic analysis, and were recovered in amonophyletic Saurosphargidae which was found to be thesister taxon ofThalattosauriformes.Sauropterygia was recovered as the sister taxon of their combined group, with a clade formed byEusaurosphargis andHelveticosaurus in a positionbasal to it.[1]
In 2014, Liet al. described a second species ofLargocephalosaurus, that was initially interpreted as aneosauropterygian due to the limited preparation of theholotype of its type speciesL. polycarpon. The second speciesL. qianensis, known from three specimens, and the newly prepared portions ofL. polycarponpostcranial skeleton, revealed the same osteoderm "body armor" and broadened rib basket that are unique to saurosphargids.[2][4] Thus,Largocephalosaurus was reinterpreted as a saurosphargid and a phylogenetic analysis recovered both species, forming a monophyleticLargocephalosaurus, as basal to theclade formed bySaurosphargis andSinosaurosphargis.[2] All four known specimens ofLargocephalosaurus came from theLuoping Biota, from Member II of the Guanling Formation, that yieldedSinosaurosphargis, alongside various invertebrates, fish, basalichthyosaurs,Atopodentatus, and several species ofeosauropterygian, including bothpachypleurosaurs andnothosaurids.[2][4][5]
The followingcladogram is simplified after Liet al. (2014)phylogenetic analysis, showing interrelationships of all known Saurosphargidae species, and the placement of the clade withinSauria.Saurosphargis was coded solely based on the holotype. 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.[2] The Saurosphargiformes are sometimes grouped together with Sauropterygia in a clade called Sauropterygomorpha.
Wolniewiczet al. (2023) recovered saurosphargids nested within Sauropterygia, more closely related toeosauropterygians than to placodonts:[3]
| Sauropterygomorpha |
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