Limits...
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.


Bairdemys thalassica sp. nov.Dermal scales of the skull in (A) dorsal and (B) lateral view. On the identification of each scale (in lower case latin numbers, from i to viii) there is after the “=” mark the preliminary homology assessment in relation to the Sterli & de la Fuente (2013) system (see Dermal scales of the skull section).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4493680&req=5

fig-4: Bairdemys thalassica sp. nov.Dermal scales of the skull in (A) dorsal and (B) lateral view. On the identification of each scale (in lower case latin numbers, from i to viii) there is after the “=” mark the preliminary homology assessment in relation to the Sterli & de la Fuente (2013) system (see Dermal scales of the skull section).

Mentions: The scales i, iii, v, vi and iv (Fig. 4) are paired in Bairdemys thalassica and in all studied Pelomedusoides. Scales iii can be divided in two units in some pelomedusoids, e.g., Pelomedusa subrufa (Bonnaterre, 1789), Erymnochelys madagascariensis, and Podocnemis vogli (Müller, 1935), or absent, e.g., Podocnemis sextuberculata (Cornalia, 1849), and Peiropemys mezzalirai (Gaffney et al., 2011). Scales ii, vii and viii are unpaired in B. thalassica, as well as in most pelomedusoids, e.g., Peltocephalus dumerilianus. In some taxa, e.g., Pelomedusa subrufa, Podocnemis unifilis, and Neochelys fajumensis (Andrews, 1903), scale ii is paired. Scale viii is absent in Pelomedusa subrufa and Cordichelys antiqua, the. Scale i forms the ventral-most portion of the rostral edge of the skull, covering the premaxilla, maxilla, and a portion of the jugal. It contacts scales ii, dorsally (caudal to the orbit), and iii, caudally. This scale can be the homologue of scales J plus I of SF13. A large and single ii scale covers the prefrontal, frontal, and portions of the postorbital and jugal, and contacts scales iii lateroventrally, iv laterocaudally, and vii caudomedially. We suggest that scale ii of Pelomedusoides can be a total or partial fusion of scales F, Z, and Y of SF13. Scale iii covers parts of the jugal, postorbital and quadratojugal in the lateral region of the skull. In contrast to the condition in Peltocephalus dumerilianus, E. madagascariensis, and Podocnemis vogli, scale iii in B. thalassica does not reach the orbital margin. This condition is shared with Bairdemys hartsteini and may represent a synapomorphy of Bairdemys. Scale iii contacts scales iv, medially, v, laterocaudally and vi, caudally, and we suggest that it corresponds to scale E in SF13. Over parts of the postorbital, quadratojugal and parietal of B. thalassica lies a semi-circular paired scale iv, that contacts scales vii medially, iii laterally and vi caudally. This scale is not found in any of the other analyzed pelomedusoids and may be the homologue to scale H of SF13. Scale v is relatively large and covers the quadrate, squamosal and parts of the quadratojugal, contacting scale vi medially. In this region, there are two scales in meiolaniforms, K and C (Sterli & de la Fuente, 2013), and we suggest that both are fused into scale v of Pelomedusoides. Due to the presence of scale iv, scale vi is reduced in B. thalassica compared to the condition of other pelomedusoids, e.g., Peltocephalus dumerilianus. It contacts scales vii, medially, and viii, caudomedially. Scale vii (identified otherwise as “interparietal scale”) has parallel lateral margins and covers half of the parietals and a small portion of the frontals, contacting scale viii caudally. Scale viii is also unpaired and covers a small caudal portion of the parietals and supraoccipital. We suggest that scales vi, vii, and viii are respectively homologues of scales D, X, and A of SF13.


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)

Bairdemys thalassica sp. nov.Dermal scales of the skull in (A) dorsal and (B) lateral view. On the identification of each scale (in lower case latin numbers, from i to viii) there is after the “=” mark the preliminary homology assessment in relation to the Sterli & de la Fuente (2013) system (see Dermal scales of the skull section).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig-4: Bairdemys thalassica sp. nov.Dermal scales of the skull in (A) dorsal and (B) lateral view. On the identification of each scale (in lower case latin numbers, from i to viii) there is after the “=” mark the preliminary homology assessment in relation to the Sterli & de la Fuente (2013) system (see Dermal scales of the skull section).
Mentions: The scales i, iii, v, vi and iv (Fig. 4) are paired in Bairdemys thalassica and in all studied Pelomedusoides. Scales iii can be divided in two units in some pelomedusoids, e.g., Pelomedusa subrufa (Bonnaterre, 1789), Erymnochelys madagascariensis, and Podocnemis vogli (Müller, 1935), or absent, e.g., Podocnemis sextuberculata (Cornalia, 1849), and Peiropemys mezzalirai (Gaffney et al., 2011). Scales ii, vii and viii are unpaired in B. thalassica, as well as in most pelomedusoids, e.g., Peltocephalus dumerilianus. In some taxa, e.g., Pelomedusa subrufa, Podocnemis unifilis, and Neochelys fajumensis (Andrews, 1903), scale ii is paired. Scale viii is absent in Pelomedusa subrufa and Cordichelys antiqua, the. Scale i forms the ventral-most portion of the rostral edge of the skull, covering the premaxilla, maxilla, and a portion of the jugal. It contacts scales ii, dorsally (caudal to the orbit), and iii, caudally. This scale can be the homologue of scales J plus I of SF13. A large and single ii scale covers the prefrontal, frontal, and portions of the postorbital and jugal, and contacts scales iii lateroventrally, iv laterocaudally, and vii caudomedially. We suggest that scale ii of Pelomedusoides can be a total or partial fusion of scales F, Z, and Y of SF13. Scale iii covers parts of the jugal, postorbital and quadratojugal in the lateral region of the skull. In contrast to the condition in Peltocephalus dumerilianus, E. madagascariensis, and Podocnemis vogli, scale iii in B. thalassica does not reach the orbital margin. This condition is shared with Bairdemys hartsteini and may represent a synapomorphy of Bairdemys. Scale iii contacts scales iv, medially, v, laterocaudally and vi, caudally, and we suggest that it corresponds to scale E in SF13. Over parts of the postorbital, quadratojugal and parietal of B. thalassica lies a semi-circular paired scale iv, that contacts scales vii medially, iii laterally and vi caudally. This scale is not found in any of the other analyzed pelomedusoids and may be the homologue to scale H of SF13. Scale v is relatively large and covers the quadrate, squamosal and parts of the quadratojugal, contacting scale vi medially. In this region, there are two scales in meiolaniforms, K and C (Sterli & de la Fuente, 2013), and we suggest that both are fused into scale v of Pelomedusoides. Due to the presence of scale iv, scale vi is reduced in B. thalassica compared to the condition of other pelomedusoids, e.g., Peltocephalus dumerilianus. It contacts scales vii, medially, and viii, caudomedially. Scale vii (identified otherwise as “interparietal scale”) has parallel lateral margins and covers half of the parietals and a small portion of the frontals, contacting scale viii caudally. Scale viii is also unpaired and covers a small caudal portion of the parietals and supraoccipital. We suggest that scales vi, vii, and viii are respectively homologues of scales D, X, and A of SF13.

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.