Rio Claro municipality (Permian of Brazil)

Also known as Paraná Basin

Where: São Paulo, Brazil (22.5° S, 47.6° W: paleocoordinates 44.1° S, 24.4° W)

• coordinate based on nearby landmark

• outcrop-level geographic resolution

When: Assistencia Member (Irati Formation), Artinskian (290.1 - 279.3 Ma)

• Soares (2003) states that the fossils come from the Irati Formation but only gives "Permian" as the most precise age specification. However, in a quite recent publication it is stated that the Irati Formation is Artinskian in age, based on absolute ages obtained from zircons from a bentonite layer (Santos et al., 2006, Gondwana Res. 9). Presence of dolomites within the succession (see lithology description) suggests that the fossils comes from the Assistência Member of the Irati Fm. (see Santos et al., 2009, J. S. Am. Earth Sci., Article in Press, doi:10.1016/j.jsames.2008.12.002).

• group of beds-level stratigraphic resolution

Environment/lithology: dolomitic limestone and tabular mixed carbonate-siliciclastic

• A thick dolomite bed occurs at the base of the sequence, which consists mainly of laminated dolomitic calcilutites with undulated lamination. Interleaved with the calcilutites there are dolomitic calcarenite horizons rich in bioclasts (mesosaur bones, crustacean shells, ostracodes, foraminifera and stromatolite clasts). This carbonate facies assemblage (the so-called “dolomitic bank”) is overlain by dark-grey and bituminous black shales interbedded with limestones and dolomites (“rhythmic zone”; Fig. 5). Crustacean shell-beds also occur in this facies. According to Lavina (1991) this rhythmic facies, with recurrently associated carbonates and shales, are distal tempestites linked to deposition from turbulent currents induced by storms and deposited below the baselevel of the storm wave action. Most of the articulated mesosaur specimens (Class I) have been collected from the top of the lower dolomitic bed, close to its boundary with the overlying rhythmic facies. Semi-articulated (Class II) and disarticulated (Classes IIIA and IIIB) bone-bed materials occur both at this level and in the rhythmically stratified deposits." (Soares, 2003).

Size class: macrofossils

Collection methods: UFRGS PV = vertebrate palaeontoloogy collections of the Universidade Federal do Rio Grande do Sul, Porto Alegre

•DGM = Divisão de Geologia e Mineralogia, Departamento Nacional de Produção Mineral

•PI = specimens in private collections

Primary reference: M. B. Soares. 2003. A taphonomic model for the Mesosauridae assemblage of the Irati Formation (Paraná Basin, Brazil). Geologica Acta 1(4):349-361 [J. Mueller/T. Liebrecht]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 90429: authorized by Johannes Mueller, entered by Torsten Liebrecht on 20.07.2009

Creative Commons license: CC BY (attribution)

Taxonomic list

• Soares (2003) gives no specific assignment of the mesosaurs. Since all mesosaur genera are considerd monotypic the Stereosternum specimens listed by Soares (2003) are referred to as Stereosternum tumidum and the Brazilosaurus specimens are referred to as Brazilosaurus sanpauloensis in the taxonomic list.
Show authors, comments, and common names
Osteichthyes
 Sauropsida - Mesosauridae
Mesosauridae indet., Brazilosaurus sanpauloensis, Stereosternum tumidum
Mesosauridae indet. Baur 1889 amniote
UFRGS PV0245P to PV0251P, PV0252P*, PV0253P to PV0256P, PV0258P, PV0259P, PV0263P; RI-1*, RI-2, RI-3*, RI-4*, RI-5*, RI-6*, RI-7*, RI-8*, RI-9*; asterisks mark partially articulated skeletons
Brazilosaurus sanpauloensis Shikama and Ozaki 1966 amniote
UFRGS PV0267P; DGM 539-R
Stereosternum tumidum Cope 1885 amniote
UFRGS PV0170P to PV0172P, PV0174P to PV0176P, PV0180P, PV0181P, PV0345P; DGM542-R