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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.

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Right ischium in lateral (A) and medial (B) views; Left ischium in medial (C) and lateral (D) views; Both ischia in articulation in anterior view (E).Abbreviations: iscbt, Ischium boot. Scale: 5cm.
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pone.0118563.g004: Right ischium in lateral (A) and medial (B) views; Left ischium in medial (C) and lateral (D) views; Both ischia in articulation in anterior view (E).Abbreviations: iscbt, Ischium boot. Scale: 5cm.

Mentions: The right ischium is better preserved than the left one (Fig. 4). Both are dorso-ventrally elongated plate-like elements, with a more robust and smooth dorsal body and expanded proximal and distal ends. In the right ischium, the proximal area, in lateral view, displays a sinuous dorsal portion, and is bordered ventrally by a laterally expanded semi-circular ventroposterior border of the acetabulum. Posteroventrally to this area, a sheet of bone projects ventrally and expands to form an irregular lateromedially compressed surface that is more distinct on the first third of the ischium, that decreases in size posteriorly and continues along the body of the bone up to distal end. The distal ends of the ischia, in lateral view, display an expanded and posteriorly directed “ischium boot”.


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)

Right ischium in lateral (A) and medial (B) views; Left ischium in medial (C) and lateral (D) views; Both ischia in articulation in anterior view (E).Abbreviations: iscbt, Ischium boot. Scale: 5cm.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0118563.g004: Right ischium in lateral (A) and medial (B) views; Left ischium in medial (C) and lateral (D) views; Both ischia in articulation in anterior view (E).Abbreviations: iscbt, Ischium boot. Scale: 5cm.
Mentions: The right ischium is better preserved than the left one (Fig. 4). Both are dorso-ventrally elongated plate-like elements, with a more robust and smooth dorsal body and expanded proximal and distal ends. In the right ischium, the proximal area, in lateral view, displays a sinuous dorsal portion, and is bordered ventrally by a laterally expanded semi-circular ventroposterior border of the acetabulum. Posteroventrally to this area, a sheet of bone projects ventrally and expands to form an irregular lateromedially compressed surface that is more distinct on the first third of the ischium, that decreases in size posteriorly and continues along the body of the bone up to distal end. The distal ends of the ischia, in lateral view, display an expanded and posteriorly directed “ischium boot”.

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