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Aging, Maturation and Growth of Sauropodomorph Dinosaurs as Deduced from Growth Curves Using Long Bone Histological Data: An Assessment of Methodological Constraints and Solutions.

Griebeler EM, Klein N, Sander PM - PLoS ONE (2013)

Bottom Line: According to an AIC-based model selection process, the LGM was the best model for our sauropodomorph sample.Sauropodomorph ages at death probably were lower than that of average scaled-up ratites and megaherbivores.Sauropodomorpha were older at maturation than scaled-up ratites and average mammals, but younger than scaled-up megaherbivores.

View Article: PubMed Central - PubMed

Affiliation: Department of Ecology, Zoological Institute, University of Mainz, Mainz, Germany.

ABSTRACT
Information on aging, maturation, and growth is important for understanding life histories of organisms. In extinct dinosaurs, such information can be derived from the histological growth record preserved in the mid-shaft cortex of long bones. Here, we construct growth models to estimate ages at death, ages at sexual maturity, ages at which individuals were fully-grown, and maximum growth rates from the growth record preserved in long bones of six sauropod dinosaur individuals (one indeterminate mamenchisaurid, two Apatosaurus sp., two indeterminate diplodocids, and one Camarasaurus sp.) and one basal sauropodomorph dinosaur individual (Plateosaurus engelhardti). Using these estimates, we establish allometries between body mass and each of these traits and compare these to extant taxa. Growth models considered for each dinosaur individual were the von Bertalanffy model, the Gompertz model, and the logistic model (LGM), all of which have inherently fixed inflection points, and the Chapman-Richards model in which the point is not fixed. We use the arithmetic mean of the age at the inflection point and of the age at which 90% of asymptotic mass is reached to assess respectively the age at sexual maturity or the age at onset of reproduction, because unambiguous indicators of maturity in Sauropodomorpha are lacking. According to an AIC-based model selection process, the LGM was the best model for our sauropodomorph sample. Allometries established are consistent with literature data on other Sauropodomorpha. All Sauropodomorpha reached full size within a time span similar to scaled-up modern mammalian megaherbivores and had similar maximum growth rates to scaled-up modern megaherbivores and ratites, but growth rates of Sauropodomorpha were lower than of an average mammal. Sauropodomorph ages at death probably were lower than that of average scaled-up ratites and megaherbivores. Sauropodomorpha were older at maturation than scaled-up ratites and average mammals, but younger than scaled-up megaherbivores.

No MeSH data available.


Related in: MedlinePlus

Growth mark record in polished sections of sauropodomorph individuals used in this study.Arrows indicate considered growth marks which are oriented parallel to the growth direction of the bone surface. The outer bone surface is at the top. Most samples extend from the outer cortex into the medullary region, but the center of medullary region is not covered by all samples. The primary bone tissue generally is laminar fibrolamellar bone. All samples except for the indeterminate mamenchisaurid sample are polished sections, which originate from core samples. Except for A) and G), which are photographed in normal incident light, all other images are in bright field illumination, with light reflected off the polished sample surface. A) Femur sample of Plateosaurus engelhardti (IFG 192.1; 740 mm) with 12 lines of arrested growth deposited. The outermost cortex does not show an external fundamental system (EFS), which indicates that this individual had not yet reached asymptotic growth, but growth rate clearly had decreased due to the close spacing of the growth marks in the outer cortex. B) Femur sample of Apatosaurus sp. (SMA 0014; 1,640 mm) with 20 growth marks consisting of lines of arrested growth and polish lines. The outer cortex is incomplete due to post mortem damage. C) Femur sample of Apatosaurus sp. (BYU 601-17328; 1,580 mm) with five growth marks consisting of polish lines. The outer cortex exhibits an EFS which contains another 13 resting lines deposited. D) Femur sample of Camarasaurus sp. (CM 36664; 1,452 mm) with five growth marks consisting of polish lines and lines of arrested growth. The outermost cortex exhibits an EFS, which contains another four resting lines. E) Femur sample of an indeterminate diplodocid (MfN.R.NW4; 1,350 mm) with 16 growth marks in form of lines of arrested growth and polish lines. The outermost cortex lacks an EFS. F) Humerus sample of an indeterminate diplodocid (MfN.R.2625, 610 mm) with nine growth marks in the form of lines of arrested growth and polish lines visible in the cortex. The outermost cortex lacks an EFS. G) Humerus sample of the indeterminate mamenchisaurid (SGP 2006/9; approx. 1,400 mm) showing 16 growth marks consisting of lines of arrested growth in the outer cortex and cyclic variation in vascularity (modulations) in the inner cortex. The outermost cortex shows an EFS which is too thin to see at the magnification of this image.
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pone-0067012-g001: Growth mark record in polished sections of sauropodomorph individuals used in this study.Arrows indicate considered growth marks which are oriented parallel to the growth direction of the bone surface. The outer bone surface is at the top. Most samples extend from the outer cortex into the medullary region, but the center of medullary region is not covered by all samples. The primary bone tissue generally is laminar fibrolamellar bone. All samples except for the indeterminate mamenchisaurid sample are polished sections, which originate from core samples. Except for A) and G), which are photographed in normal incident light, all other images are in bright field illumination, with light reflected off the polished sample surface. A) Femur sample of Plateosaurus engelhardti (IFG 192.1; 740 mm) with 12 lines of arrested growth deposited. The outermost cortex does not show an external fundamental system (EFS), which indicates that this individual had not yet reached asymptotic growth, but growth rate clearly had decreased due to the close spacing of the growth marks in the outer cortex. B) Femur sample of Apatosaurus sp. (SMA 0014; 1,640 mm) with 20 growth marks consisting of lines of arrested growth and polish lines. The outer cortex is incomplete due to post mortem damage. C) Femur sample of Apatosaurus sp. (BYU 601-17328; 1,580 mm) with five growth marks consisting of polish lines. The outer cortex exhibits an EFS which contains another 13 resting lines deposited. D) Femur sample of Camarasaurus sp. (CM 36664; 1,452 mm) with five growth marks consisting of polish lines and lines of arrested growth. The outermost cortex exhibits an EFS, which contains another four resting lines. E) Femur sample of an indeterminate diplodocid (MfN.R.NW4; 1,350 mm) with 16 growth marks in form of lines of arrested growth and polish lines. The outermost cortex lacks an EFS. F) Humerus sample of an indeterminate diplodocid (MfN.R.2625, 610 mm) with nine growth marks in the form of lines of arrested growth and polish lines visible in the cortex. The outermost cortex lacks an EFS. G) Humerus sample of the indeterminate mamenchisaurid (SGP 2006/9; approx. 1,400 mm) showing 16 growth marks consisting of lines of arrested growth in the outer cortex and cyclic variation in vascularity (modulations) in the inner cortex. The outermost cortex shows an EFS which is too thin to see at the magnification of this image.

Mentions: Polished sections were examined with a Leica DMLP compound microscope (1.6× to 40× magnification of the objective lenses) in reflected light bright field illumination and with a binocular microscope. Growth marks were counted and recorded in the polished sections either with a binocular microscope with a camera lucida attached in normal light (Figure 1) or on high-resolution digital images of the sections using reflected light (Figure 1). Thin sections were examined by standard light microscopic techniques (normal transmitted light, polarized light) with a Leica DMLP compound microscope (1.6× to 40.0× magnification of the objective lenses).


Aging, Maturation and Growth of Sauropodomorph Dinosaurs as Deduced from Growth Curves Using Long Bone Histological Data: An Assessment of Methodological Constraints and Solutions.

Griebeler EM, Klein N, Sander PM - PLoS ONE (2013)

Growth mark record in polished sections of sauropodomorph individuals used in this study.Arrows indicate considered growth marks which are oriented parallel to the growth direction of the bone surface. The outer bone surface is at the top. Most samples extend from the outer cortex into the medullary region, but the center of medullary region is not covered by all samples. The primary bone tissue generally is laminar fibrolamellar bone. All samples except for the indeterminate mamenchisaurid sample are polished sections, which originate from core samples. Except for A) and G), which are photographed in normal incident light, all other images are in bright field illumination, with light reflected off the polished sample surface. A) Femur sample of Plateosaurus engelhardti (IFG 192.1; 740 mm) with 12 lines of arrested growth deposited. The outermost cortex does not show an external fundamental system (EFS), which indicates that this individual had not yet reached asymptotic growth, but growth rate clearly had decreased due to the close spacing of the growth marks in the outer cortex. B) Femur sample of Apatosaurus sp. (SMA 0014; 1,640 mm) with 20 growth marks consisting of lines of arrested growth and polish lines. The outer cortex is incomplete due to post mortem damage. C) Femur sample of Apatosaurus sp. (BYU 601-17328; 1,580 mm) with five growth marks consisting of polish lines. The outer cortex exhibits an EFS which contains another 13 resting lines deposited. D) Femur sample of Camarasaurus sp. (CM 36664; 1,452 mm) with five growth marks consisting of polish lines and lines of arrested growth. The outermost cortex exhibits an EFS, which contains another four resting lines. E) Femur sample of an indeterminate diplodocid (MfN.R.NW4; 1,350 mm) with 16 growth marks in form of lines of arrested growth and polish lines. The outermost cortex lacks an EFS. F) Humerus sample of an indeterminate diplodocid (MfN.R.2625, 610 mm) with nine growth marks in the form of lines of arrested growth and polish lines visible in the cortex. The outermost cortex lacks an EFS. G) Humerus sample of the indeterminate mamenchisaurid (SGP 2006/9; approx. 1,400 mm) showing 16 growth marks consisting of lines of arrested growth in the outer cortex and cyclic variation in vascularity (modulations) in the inner cortex. The outermost cortex shows an EFS which is too thin to see at the magnification of this image.
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Related In: Results  -  Collection

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pone-0067012-g001: Growth mark record in polished sections of sauropodomorph individuals used in this study.Arrows indicate considered growth marks which are oriented parallel to the growth direction of the bone surface. The outer bone surface is at the top. Most samples extend from the outer cortex into the medullary region, but the center of medullary region is not covered by all samples. The primary bone tissue generally is laminar fibrolamellar bone. All samples except for the indeterminate mamenchisaurid sample are polished sections, which originate from core samples. Except for A) and G), which are photographed in normal incident light, all other images are in bright field illumination, with light reflected off the polished sample surface. A) Femur sample of Plateosaurus engelhardti (IFG 192.1; 740 mm) with 12 lines of arrested growth deposited. The outermost cortex does not show an external fundamental system (EFS), which indicates that this individual had not yet reached asymptotic growth, but growth rate clearly had decreased due to the close spacing of the growth marks in the outer cortex. B) Femur sample of Apatosaurus sp. (SMA 0014; 1,640 mm) with 20 growth marks consisting of lines of arrested growth and polish lines. The outer cortex is incomplete due to post mortem damage. C) Femur sample of Apatosaurus sp. (BYU 601-17328; 1,580 mm) with five growth marks consisting of polish lines. The outer cortex exhibits an EFS which contains another 13 resting lines deposited. D) Femur sample of Camarasaurus sp. (CM 36664; 1,452 mm) with five growth marks consisting of polish lines and lines of arrested growth. The outermost cortex exhibits an EFS, which contains another four resting lines. E) Femur sample of an indeterminate diplodocid (MfN.R.NW4; 1,350 mm) with 16 growth marks in form of lines of arrested growth and polish lines. The outermost cortex lacks an EFS. F) Humerus sample of an indeterminate diplodocid (MfN.R.2625, 610 mm) with nine growth marks in the form of lines of arrested growth and polish lines visible in the cortex. The outermost cortex lacks an EFS. G) Humerus sample of the indeterminate mamenchisaurid (SGP 2006/9; approx. 1,400 mm) showing 16 growth marks consisting of lines of arrested growth in the outer cortex and cyclic variation in vascularity (modulations) in the inner cortex. The outermost cortex shows an EFS which is too thin to see at the magnification of this image.
Mentions: Polished sections were examined with a Leica DMLP compound microscope (1.6× to 40× magnification of the objective lenses) in reflected light bright field illumination and with a binocular microscope. Growth marks were counted and recorded in the polished sections either with a binocular microscope with a camera lucida attached in normal light (Figure 1) or on high-resolution digital images of the sections using reflected light (Figure 1). Thin sections were examined by standard light microscopic techniques (normal transmitted light, polarized light) with a Leica DMLP compound microscope (1.6× to 40.0× magnification of the objective lenses).

Bottom Line: According to an AIC-based model selection process, the LGM was the best model for our sauropodomorph sample.Sauropodomorph ages at death probably were lower than that of average scaled-up ratites and megaherbivores.Sauropodomorpha were older at maturation than scaled-up ratites and average mammals, but younger than scaled-up megaherbivores.

View Article: PubMed Central - PubMed

Affiliation: Department of Ecology, Zoological Institute, University of Mainz, Mainz, Germany.

ABSTRACT
Information on aging, maturation, and growth is important for understanding life histories of organisms. In extinct dinosaurs, such information can be derived from the histological growth record preserved in the mid-shaft cortex of long bones. Here, we construct growth models to estimate ages at death, ages at sexual maturity, ages at which individuals were fully-grown, and maximum growth rates from the growth record preserved in long bones of six sauropod dinosaur individuals (one indeterminate mamenchisaurid, two Apatosaurus sp., two indeterminate diplodocids, and one Camarasaurus sp.) and one basal sauropodomorph dinosaur individual (Plateosaurus engelhardti). Using these estimates, we establish allometries between body mass and each of these traits and compare these to extant taxa. Growth models considered for each dinosaur individual were the von Bertalanffy model, the Gompertz model, and the logistic model (LGM), all of which have inherently fixed inflection points, and the Chapman-Richards model in which the point is not fixed. We use the arithmetic mean of the age at the inflection point and of the age at which 90% of asymptotic mass is reached to assess respectively the age at sexual maturity or the age at onset of reproduction, because unambiguous indicators of maturity in Sauropodomorpha are lacking. According to an AIC-based model selection process, the LGM was the best model for our sauropodomorph sample. Allometries established are consistent with literature data on other Sauropodomorpha. All Sauropodomorpha reached full size within a time span similar to scaled-up modern mammalian megaherbivores and had similar maximum growth rates to scaled-up modern megaherbivores and ratites, but growth rates of Sauropodomorpha were lower than of an average mammal. Sauropodomorph ages at death probably were lower than that of average scaled-up ratites and megaherbivores. Sauropodomorpha were older at maturation than scaled-up ratites and average mammals, but younger than scaled-up megaherbivores.

No MeSH data available.


Related in: MedlinePlus