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The last marine pelomedusoids (Testudines: Pleurodira): a new species of Bairdemys and the paleoecology of Stereogenyina.

Ferreira GS, Rincón AD, Solórzano A, Langer MC - PeerJ (2015)

Bottom Line: Here, we describe a new Stereogenyina species, based on an almost complete skull from the middle Miocene Capadare Formation, of Venezuela.Based on geometric morphometrics analyses, we related the development of the stereogenyin secondary palate with the acquisition of a durophagous diet.These two inferences allowed us to hypothesize that stereogenyins occupied an ecological niche similar to that of the extant Carettini sea turtles, and that the rise of the latter group may be related to the Stereogenyina diversity fall in the end of the Miocene.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratório de Paleontologia de Ribeirão Preto, FFCLRP, Universidade de São Paulo , Ribeirão Preto, SP , Brazil.

ABSTRACT
The extinct Stereogenyina turtles form a relatively diverse Podocnemididae lineage, with twelve described and phylogenetically positioned species. They are characterized by a wide geographic and temporal range, from the Eocene of Africa to the Pleistocene of Southeast Asia, and a peculiar palate morphology, with a secondary palate that is unique among side-necked turtles. Here, we describe a new Stereogenyina species, based on an almost complete skull from the middle Miocene Capadare Formation, of Venezuela. A new phylogenetic analysis supports the assignment of the new species to the genus Bairdemys. Based on geometric morphometrics analyses, we related the development of the stereogenyin secondary palate with the acquisition of a durophagous diet. Based on a review of the sedimentary environments where their fossils are found, we also propose that stereogenyins were a marine radiation of podocnemidid turtles, as corroborated by previous studies of fossil eggs and limb morphology. These two inferences allowed us to hypothesize that stereogenyins occupied an ecological niche similar to that of the extant Carettini sea turtles, and that the rise of the latter group may be related to the Stereogenyina diversity fall in the end of the Miocene.

No MeSH data available.


Results of the geometric morphometric analyses.Principal component analysis (A and C) derived from the first two principal components (PC1 and PC2) and comparison of the mean values of the coordinates (B and D) for the upper (A and B) and the lower jaws (C and D). D’Arcy Thompson grids correspond to extreme shape variation. Durophagous taxa are represented in blue, non-durophagous in green, and fossil taxa with unknown diet in purple.
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fig-7: Results of the geometric morphometric analyses.Principal component analysis (A and C) derived from the first two principal components (PC1 and PC2) and comparison of the mean values of the coordinates (B and D) for the upper (A and B) and the lower jaws (C and D). D’Arcy Thompson grids correspond to extreme shape variation. Durophagous taxa are represented in blue, non-durophagous in green, and fossil taxa with unknown diet in purple.

Mentions: Two geometric morphometric analyses were performed to test if the morphology of the triturating surface of the upper and lower jaws of Stereogenyina corresponds to that of a durophagous turtle (Claude et al., 2004). The morphometric analysis of the upper jaw employed 14 extant taxa and three Stereogenyina with well preserved upper jaws. The lower jaw analysis employed 15 extant taxa plus three Stereogenyina with well preserved mandibles. The extant taxa used in both analyses were chosen based on the knowledge of their feeding habits (Moll , 1976; Meylan, 1988; Burke, Morreale & Standora, 1994; Teran, Vogt & Gomez, 1995; Pérez-Emán & Paolillo, 1997; Claude et al., 2004; Polovina et al., 2004; Salmon, Jones & Horch, 2004; Garcia & Lourenco, 2007). The list of employed specimens is seen in Supplemental Information 3. The skulls were photographed in ventral view and the lower jaws in dorsal view, and landmarks were digitized using the software tpsDig2 (Rohlf, 2005). Twelve landmarks for the upper and ten for the lower jaw were chosen (Fig. 6; description of the landmarks on Supplemental Information 3), aiming at representing the size and general shape of those structures. The shape data were extracted from the landmark dataset by a Generalized Procrustes Analysis (GPA, Rohlf, 1999) in the software MorphoJ v. 1.06d (Klingenberg, 2011), taking into account object symmetry (Klingenberg & McIntyre, 1998; Klingenberg, Barluenga & Meyer, 2002). Principal Component Analysis (PCA) (Table 2; Figs. 7A and 7C) were conducted for each dataset and components that explained morphological variation were retained after analysis. We tested the normality of shape components for upper and lower jaws with the Shapiro–Wilk’s test and a MANOVA was performed to detect differences between durophagous, non-durophagous, and fossil species, using an a posteriori pairwise comparison test. All tests were performed using geomorph package (Adams & Otarola-Castillo, 2013; Adams, Collyer & Sherratt, 2015) in R environment software (R Development Core Team, 2013).


The last marine pelomedusoids (Testudines: Pleurodira): a new species of Bairdemys and the paleoecology of Stereogenyina.

Ferreira GS, Rincón AD, Solórzano A, Langer MC - PeerJ (2015)

Results of the geometric morphometric analyses.Principal component analysis (A and C) derived from the first two principal components (PC1 and PC2) and comparison of the mean values of the coordinates (B and D) for the upper (A and B) and the lower jaws (C and D). D’Arcy Thompson grids correspond to extreme shape variation. Durophagous taxa are represented in blue, non-durophagous in green, and fossil taxa with unknown diet in purple.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493680&req=5

fig-7: Results of the geometric morphometric analyses.Principal component analysis (A and C) derived from the first two principal components (PC1 and PC2) and comparison of the mean values of the coordinates (B and D) for the upper (A and B) and the lower jaws (C and D). D’Arcy Thompson grids correspond to extreme shape variation. Durophagous taxa are represented in blue, non-durophagous in green, and fossil taxa with unknown diet in purple.
Mentions: Two geometric morphometric analyses were performed to test if the morphology of the triturating surface of the upper and lower jaws of Stereogenyina corresponds to that of a durophagous turtle (Claude et al., 2004). The morphometric analysis of the upper jaw employed 14 extant taxa and three Stereogenyina with well preserved upper jaws. The lower jaw analysis employed 15 extant taxa plus three Stereogenyina with well preserved mandibles. The extant taxa used in both analyses were chosen based on the knowledge of their feeding habits (Moll , 1976; Meylan, 1988; Burke, Morreale & Standora, 1994; Teran, Vogt & Gomez, 1995; Pérez-Emán & Paolillo, 1997; Claude et al., 2004; Polovina et al., 2004; Salmon, Jones & Horch, 2004; Garcia & Lourenco, 2007). The list of employed specimens is seen in Supplemental Information 3. The skulls were photographed in ventral view and the lower jaws in dorsal view, and landmarks were digitized using the software tpsDig2 (Rohlf, 2005). Twelve landmarks for the upper and ten for the lower jaw were chosen (Fig. 6; description of the landmarks on Supplemental Information 3), aiming at representing the size and general shape of those structures. The shape data were extracted from the landmark dataset by a Generalized Procrustes Analysis (GPA, Rohlf, 1999) in the software MorphoJ v. 1.06d (Klingenberg, 2011), taking into account object symmetry (Klingenberg & McIntyre, 1998; Klingenberg, Barluenga & Meyer, 2002). Principal Component Analysis (PCA) (Table 2; Figs. 7A and 7C) were conducted for each dataset and components that explained morphological variation were retained after analysis. We tested the normality of shape components for upper and lower jaws with the Shapiro–Wilk’s test and a MANOVA was performed to detect differences between durophagous, non-durophagous, and fossil species, using an a posteriori pairwise comparison test. All tests were performed using geomorph package (Adams & Otarola-Castillo, 2013; Adams, Collyer & Sherratt, 2015) in R environment software (R Development Core Team, 2013).

Bottom Line: Here, we describe a new Stereogenyina species, based on an almost complete skull from the middle Miocene Capadare Formation, of Venezuela.Based on geometric morphometrics analyses, we related the development of the stereogenyin secondary palate with the acquisition of a durophagous diet.These two inferences allowed us to hypothesize that stereogenyins occupied an ecological niche similar to that of the extant Carettini sea turtles, and that the rise of the latter group may be related to the Stereogenyina diversity fall in the end of the Miocene.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratório de Paleontologia de Ribeirão Preto, FFCLRP, Universidade de São Paulo , Ribeirão Preto, SP , Brazil.

ABSTRACT
The extinct Stereogenyina turtles form a relatively diverse Podocnemididae lineage, with twelve described and phylogenetically positioned species. They are characterized by a wide geographic and temporal range, from the Eocene of Africa to the Pleistocene of Southeast Asia, and a peculiar palate morphology, with a secondary palate that is unique among side-necked turtles. Here, we describe a new Stereogenyina species, based on an almost complete skull from the middle Miocene Capadare Formation, of Venezuela. A new phylogenetic analysis supports the assignment of the new species to the genus Bairdemys. Based on geometric morphometrics analyses, we related the development of the stereogenyin secondary palate with the acquisition of a durophagous diet. Based on a review of the sedimentary environments where their fossils are found, we also propose that stereogenyins were a marine radiation of podocnemidid turtles, as corroborated by previous studies of fossil eggs and limb morphology. These two inferences allowed us to hypothesize that stereogenyins occupied an ecological niche similar to that of the extant Carettini sea turtles, and that the rise of the latter group may be related to the Stereogenyina diversity fall in the end of the Miocene.

No MeSH data available.