Limits...
First 'Rauisuchian' archosaur (Pseudosuchia, Loricata) for the Middle Triassic Santacruzodon assemblage zone (Santa Maria Supersequence), Rio Grande do Sul State, Brazil.

Lacerda MB, Schultz CL, Bertoni-Machado C - PLoS ONE (2015)

Bottom Line: In Brazil, their fossils are found only in the Santa Maria Formation (Paraná Basin) of the Rio Grande do Sul State, specifically in the Middle Triassic Dinodontosaurus assemblage zone (AZ) and the Late Triassic Hyperodapedon AZ (Rauisuchus tiradentes).Between these two cenozones is the Santacruzodon AZ (Middle Triassic), whose record was, until now, restricted to non-mammalian cynodonts and the proterochampsian Chanaresuchus bonapartei.Here we present the first occurrence of a rauisuchian archosaur for this cenozone, from the Schoenstatt outcrop, located near the city of Santa Cruz do Sul and propose a new species, based on biostratigraphical evidence and a comparative osteological analysis.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Geociências, Laboratório de Paleovertebrados, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.

ABSTRACT
The 'Rauisuchia' are a group of Triassic pseudosuchian archosaurs that displayed a near worldwide distribution. In Brazil, their fossils are found only in the Santa Maria Formation (Paraná Basin) of the Rio Grande do Sul State, specifically in the Middle Triassic Dinodontosaurus assemblage zone (AZ) and the Late Triassic Hyperodapedon AZ (Rauisuchus tiradentes). Between these two cenozones is the Santacruzodon AZ (Middle Triassic), whose record was, until now, restricted to non-mammalian cynodonts and the proterochampsian Chanaresuchus bonapartei. Here we present the first occurrence of a rauisuchian archosaur for this cenozone, from the Schoenstatt outcrop, located near the city of Santa Cruz do Sul and propose a new species, based on biostratigraphical evidence and a comparative osteological analysis.

Show MeSH

Related in: MedlinePlus

Temporal distribution of ‘rauisuchian’ taxa of South America and those with morphology of ilia and ischia similar to Dagasuchus santacruzensis, emphasizing the shape of the supra-acetabular crest and supra-acetabular ridge on the ilium and the outline of the section of the ischium:Stagonosuchus nyassicus (A) and Batrachotomus kupeferzellensis (B) based on [3]; Prestosuchus chiniquensis (C) based on [24] (2010); Rauisuchoidea indet. (D) based on [34]; Saurosuchus galilei based on [32]. On the right, comparative temporal distribution of these species, along with other South American ones (Modified from [5]). Comparative bones are not to scale.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4340915&req=5

pone.0118563.g006: Temporal distribution of ‘rauisuchian’ taxa of South America and those with morphology of ilia and ischia similar to Dagasuchus santacruzensis, emphasizing the shape of the supra-acetabular crest and supra-acetabular ridge on the ilium and the outline of the section of the ischium:Stagonosuchus nyassicus (A) and Batrachotomus kupeferzellensis (B) based on [3]; Prestosuchus chiniquensis (C) based on [24] (2010); Rauisuchoidea indet. (D) based on [34]; Saurosuchus galilei based on [32]. On the right, comparative temporal distribution of these species, along with other South American ones (Modified from [5]). Comparative bones are not to scale.

Mentions: Additional evidence to support a new taxon would be the biostratigraphical position of this specimen in the Santa Maria Supersequence. As presented earlier, all other ‘rauisuchian’ taxa have been limited to the Dinodontosaurus and Hyperodapedon assemblage zones. The Santacruzodon AZ is a unique third order sequence within the Santa Maria Supersequence, with paleofaunal correlation with the “Isalo II” fauna from Madagascar [22, 23, 25, 26], where no ‘rauisuchian’ has been described. However, the presence of Chanaresuchus [27, 30] in both the Dinodontosaurus and Santacruzodon assemblage zones, as well as in the Chañares and Ischigualasto faunas would indicate that at least one taxon continued across the Ladinian/Carnian transition. As such, the possibility of a previously described Ladinan ‘rauisuchian’ taxon that existed up to the Late Ladinian/ Early Carnian cannot be completely excluded. However, we consider that all the other evidences presented here (Fig. 6) along with the biostratigrafical data justifies the distinction of this specimen as unique among other ‘rauisichian’ taxa, and as such, would be more than only a “rauisuchian indet.” or a similar provisional designation.


First 'Rauisuchian' archosaur (Pseudosuchia, Loricata) for the Middle Triassic Santacruzodon assemblage zone (Santa Maria Supersequence), Rio Grande do Sul State, Brazil.

Lacerda MB, Schultz CL, Bertoni-Machado C - PLoS ONE (2015)

Temporal distribution of ‘rauisuchian’ taxa of South America and those with morphology of ilia and ischia similar to Dagasuchus santacruzensis, emphasizing the shape of the supra-acetabular crest and supra-acetabular ridge on the ilium and the outline of the section of the ischium:Stagonosuchus nyassicus (A) and Batrachotomus kupeferzellensis (B) based on [3]; Prestosuchus chiniquensis (C) based on [24] (2010); Rauisuchoidea indet. (D) based on [34]; Saurosuchus galilei based on [32]. On the right, comparative temporal distribution of these species, along with other South American ones (Modified from [5]). Comparative bones are not to scale.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4340915&req=5

pone.0118563.g006: Temporal distribution of ‘rauisuchian’ taxa of South America and those with morphology of ilia and ischia similar to Dagasuchus santacruzensis, emphasizing the shape of the supra-acetabular crest and supra-acetabular ridge on the ilium and the outline of the section of the ischium:Stagonosuchus nyassicus (A) and Batrachotomus kupeferzellensis (B) based on [3]; Prestosuchus chiniquensis (C) based on [24] (2010); Rauisuchoidea indet. (D) based on [34]; Saurosuchus galilei based on [32]. On the right, comparative temporal distribution of these species, along with other South American ones (Modified from [5]). Comparative bones are not to scale.
Mentions: Additional evidence to support a new taxon would be the biostratigraphical position of this specimen in the Santa Maria Supersequence. As presented earlier, all other ‘rauisuchian’ taxa have been limited to the Dinodontosaurus and Hyperodapedon assemblage zones. The Santacruzodon AZ is a unique third order sequence within the Santa Maria Supersequence, with paleofaunal correlation with the “Isalo II” fauna from Madagascar [22, 23, 25, 26], where no ‘rauisuchian’ has been described. However, the presence of Chanaresuchus [27, 30] in both the Dinodontosaurus and Santacruzodon assemblage zones, as well as in the Chañares and Ischigualasto faunas would indicate that at least one taxon continued across the Ladinian/Carnian transition. As such, the possibility of a previously described Ladinan ‘rauisuchian’ taxon that existed up to the Late Ladinian/ Early Carnian cannot be completely excluded. However, we consider that all the other evidences presented here (Fig. 6) along with the biostratigrafical data justifies the distinction of this specimen as unique among other ‘rauisichian’ taxa, and as such, would be more than only a “rauisuchian indet.” or a similar provisional designation.

Bottom Line: In Brazil, their fossils are found only in the Santa Maria Formation (Paraná Basin) of the Rio Grande do Sul State, specifically in the Middle Triassic Dinodontosaurus assemblage zone (AZ) and the Late Triassic Hyperodapedon AZ (Rauisuchus tiradentes).Between these two cenozones is the Santacruzodon AZ (Middle Triassic), whose record was, until now, restricted to non-mammalian cynodonts and the proterochampsian Chanaresuchus bonapartei.Here we present the first occurrence of a rauisuchian archosaur for this cenozone, from the Schoenstatt outcrop, located near the city of Santa Cruz do Sul and propose a new species, based on biostratigraphical evidence and a comparative osteological analysis.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Geociências, Laboratório de Paleovertebrados, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.

ABSTRACT
The 'Rauisuchia' are a group of Triassic pseudosuchian archosaurs that displayed a near worldwide distribution. In Brazil, their fossils are found only in the Santa Maria Formation (Paraná Basin) of the Rio Grande do Sul State, specifically in the Middle Triassic Dinodontosaurus assemblage zone (AZ) and the Late Triassic Hyperodapedon AZ (Rauisuchus tiradentes). Between these two cenozones is the Santacruzodon AZ (Middle Triassic), whose record was, until now, restricted to non-mammalian cynodonts and the proterochampsian Chanaresuchus bonapartei. Here we present the first occurrence of a rauisuchian archosaur for this cenozone, from the Schoenstatt outcrop, located near the city of Santa Cruz do Sul and propose a new species, based on biostratigraphical evidence and a comparative osteological analysis.

Show MeSH
Related in: MedlinePlus