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3-D modelling of megaloolithid clutches: insights about nest construction and dinosaur behaviour.

Vila B, Jackson FD, Fortuny J, Sellés AG, Galobart A - PLoS ONE (2010)

Bottom Line: Megaloolithid eggs have long been associated with sauropod dinosaurs.Tectonic deformation in the study area strongly influenced egg size and shape, which could potentially lead to misinterpretation of reproductive biology if 2D and 3D maps are not corrected for bed dip that results from tectonism.The distinct clutch geometry at Pinyes and other localities likely resulted from the asymmetrical, inclined, and laterally compressed titanosaur pes unguals of the female, using the hind foot for scratch-digging during nest excavation.

View Article: PubMed Central - PubMed

Affiliation: Institut Català de Paleontologia, Campus de la Universitat Autònoma de Barcelona, Barcelona, Spain. bernat.vila@icp.cat

ABSTRACT

Background: Megaloolithid eggs have long been associated with sauropod dinosaurs. Despite their extensive and worldwide fossil record, interpretations of egg size and shape, clutch morphology, and incubation strategy vary. The Pinyes locality in the Upper Cretaceous Tremp Formation in the southern Pyrenees, Catalonia provides new information for addressing these issues. Nine horizons containing Megaloolithus siruguei clutches are exposed near the village of Coll de Nargó. Tectonic deformation in the study area strongly influenced egg size and shape, which could potentially lead to misinterpretation of reproductive biology if 2D and 3D maps are not corrected for bed dip that results from tectonism.

Methodology/findings: Detailed taphonomic study and three-dimensional modelling of fossil eggs show that intact M. siruguei clutches contained 20-28 eggs, which is substantially larger than commonly reported from Europe and India. Linear and grouped eggs occur in three superimposed levels and form an asymmetric, elongate, bowl-shaped profile in lateral view. Computed tomography data support previous interpretations that the eggs hatched within the substrate. Megaloolithid clutch sizes reported from other European and Indian localities are typically less than 15 eggs; however, these clutches often include linear or grouped eggs that resemble those of the larger Pinyes clutches and may reflect preservation of incomplete clutches.

Conclusions/significance: We propose that 25 eggs represent a typical megaloolithid clutch size and smaller egg clusters that display linear or grouped egg arrangements reported at Pinyes and other localities may represent eroded remnants of larger clutches. The similarity of megaloolithid clutch morphology from localities worldwide strongly suggests common reproductive behaviour. The distinct clutch geometry at Pinyes and other localities likely resulted from the asymmetrical, inclined, and laterally compressed titanosaur pes unguals of the female, using the hind foot for scratch-digging during nest excavation.

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Egg features at Pinyes locality.(A)–Interpreted hatching window in two eggs from clutch 17E04-B. Note the elliptical outline and size of the truncations. Grid squares ∼10 cm. (B)–Rose diagram showing long axis direction for Pinyes eggs. Note the NE-SW alignment, coincident with the tectonic foliation. (C)–Computed Tomography scan images of egg A from cluster 13E02 showing vertical (YZ) cross section (left) and equatorial (XY) cross section (right) with respective three-dimensional miniature render (yellow arrow indicates top of the egg). Note that the grouped eggshell fragments are vertically embedded by sediment. White and red arrows indicate nodules and eggshell pieces, respectively. Scale bars  = 5 cm.
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pone-0010362-g002: Egg features at Pinyes locality.(A)–Interpreted hatching window in two eggs from clutch 17E04-B. Note the elliptical outline and size of the truncations. Grid squares ∼10 cm. (B)–Rose diagram showing long axis direction for Pinyes eggs. Note the NE-SW alignment, coincident with the tectonic foliation. (C)–Computed Tomography scan images of egg A from cluster 13E02 showing vertical (YZ) cross section (left) and equatorial (XY) cross section (right) with respective three-dimensional miniature render (yellow arrow indicates top of the egg). Note that the grouped eggshell fragments are vertically embedded by sediment. White and red arrows indicate nodules and eggshell pieces, respectively. Scale bars  = 5 cm.

Mentions: Most eggs exposed at the Pinyes locality were incompletely preserved because of recent erosion; however, excavation occasionally revealed relatively intact specimens in the subsurface. Some eggs exposed in cross-section revealed numerous eggshell fragments, predominantly oriented concave up within the mudstone matrix that filled the egg interior. Two clusters, 17E04-A and 17E04-B contained 8 and 20 eggs, respectively (Table 1). The upper portions of six eggs in 17E04-B appeared truncated and exhibited sizeable areas that lacked eggshell. After correction for dip, this missing eggshell formed an elliptical “opening” parallel to the bedding plane (Fig. 2A).


3-D modelling of megaloolithid clutches: insights about nest construction and dinosaur behaviour.

Vila B, Jackson FD, Fortuny J, Sellés AG, Galobart A - PLoS ONE (2010)

Egg features at Pinyes locality.(A)–Interpreted hatching window in two eggs from clutch 17E04-B. Note the elliptical outline and size of the truncations. Grid squares ∼10 cm. (B)–Rose diagram showing long axis direction for Pinyes eggs. Note the NE-SW alignment, coincident with the tectonic foliation. (C)–Computed Tomography scan images of egg A from cluster 13E02 showing vertical (YZ) cross section (left) and equatorial (XY) cross section (right) with respective three-dimensional miniature render (yellow arrow indicates top of the egg). Note that the grouped eggshell fragments are vertically embedded by sediment. White and red arrows indicate nodules and eggshell pieces, respectively. Scale bars  = 5 cm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2864735&req=5

pone-0010362-g002: Egg features at Pinyes locality.(A)–Interpreted hatching window in two eggs from clutch 17E04-B. Note the elliptical outline and size of the truncations. Grid squares ∼10 cm. (B)–Rose diagram showing long axis direction for Pinyes eggs. Note the NE-SW alignment, coincident with the tectonic foliation. (C)–Computed Tomography scan images of egg A from cluster 13E02 showing vertical (YZ) cross section (left) and equatorial (XY) cross section (right) with respective three-dimensional miniature render (yellow arrow indicates top of the egg). Note that the grouped eggshell fragments are vertically embedded by sediment. White and red arrows indicate nodules and eggshell pieces, respectively. Scale bars  = 5 cm.
Mentions: Most eggs exposed at the Pinyes locality were incompletely preserved because of recent erosion; however, excavation occasionally revealed relatively intact specimens in the subsurface. Some eggs exposed in cross-section revealed numerous eggshell fragments, predominantly oriented concave up within the mudstone matrix that filled the egg interior. Two clusters, 17E04-A and 17E04-B contained 8 and 20 eggs, respectively (Table 1). The upper portions of six eggs in 17E04-B appeared truncated and exhibited sizeable areas that lacked eggshell. After correction for dip, this missing eggshell formed an elliptical “opening” parallel to the bedding plane (Fig. 2A).

Bottom Line: Megaloolithid eggs have long been associated with sauropod dinosaurs.Tectonic deformation in the study area strongly influenced egg size and shape, which could potentially lead to misinterpretation of reproductive biology if 2D and 3D maps are not corrected for bed dip that results from tectonism.The distinct clutch geometry at Pinyes and other localities likely resulted from the asymmetrical, inclined, and laterally compressed titanosaur pes unguals of the female, using the hind foot for scratch-digging during nest excavation.

View Article: PubMed Central - PubMed

Affiliation: Institut Català de Paleontologia, Campus de la Universitat Autònoma de Barcelona, Barcelona, Spain. bernat.vila@icp.cat

ABSTRACT

Background: Megaloolithid eggs have long been associated with sauropod dinosaurs. Despite their extensive and worldwide fossil record, interpretations of egg size and shape, clutch morphology, and incubation strategy vary. The Pinyes locality in the Upper Cretaceous Tremp Formation in the southern Pyrenees, Catalonia provides new information for addressing these issues. Nine horizons containing Megaloolithus siruguei clutches are exposed near the village of Coll de Nargó. Tectonic deformation in the study area strongly influenced egg size and shape, which could potentially lead to misinterpretation of reproductive biology if 2D and 3D maps are not corrected for bed dip that results from tectonism.

Methodology/findings: Detailed taphonomic study and three-dimensional modelling of fossil eggs show that intact M. siruguei clutches contained 20-28 eggs, which is substantially larger than commonly reported from Europe and India. Linear and grouped eggs occur in three superimposed levels and form an asymmetric, elongate, bowl-shaped profile in lateral view. Computed tomography data support previous interpretations that the eggs hatched within the substrate. Megaloolithid clutch sizes reported from other European and Indian localities are typically less than 15 eggs; however, these clutches often include linear or grouped eggs that resemble those of the larger Pinyes clutches and may reflect preservation of incomplete clutches.

Conclusions/significance: We propose that 25 eggs represent a typical megaloolithid clutch size and smaller egg clusters that display linear or grouped egg arrangements reported at Pinyes and other localities may represent eroded remnants of larger clutches. The similarity of megaloolithid clutch morphology from localities worldwide strongly suggests common reproductive behaviour. The distinct clutch geometry at Pinyes and other localities likely resulted from the asymmetrical, inclined, and laterally compressed titanosaur pes unguals of the female, using the hind foot for scratch-digging during nest excavation.

Show MeSH