I am FWO postdoctoral fellow, based at the Free University of Brussels (VUB) and Royal Belgian Institute of Natural Sciences (RBINS), focussing on the bone and tooth histology of ornithopod dinosaurs, and the potential of preservation of biomolecules in millions of years old bones. Phone: http://koenstein.wix.com/koensteininfo
The Cretaceous–Palaeogene mass extinction around 66 million years ago was triggered by the Chicxu... more The Cretaceous–Palaeogene mass extinction around 66 million years ago was triggered by the Chicxulub asteroid impact on the present-day Yucatán Peninsula1,2. This event caused the highly selective extinction that eliminated about 76% of species3,4, including all non-avian dinosaurs, pterosaurs, ammonites, rudists and most marine reptiles. The timing of the impact and its aftermath have been studied mainly on millennial timescales, leaving the season of the impact unconstrained. Here, by studying fishes that died on the day the Mesozoic era ended, we demonstrate that the impact that caused the Cretaceous–Palaeogene mass extinction took place during boreal spring. Osteohistology together with stable isotope records of exceptionally preserved perichondral and dermal bones in acipenseriform fishes from the Tanis impact-induced seiche deposits5 reveal annual cyclicity across the final years of the Cretaceous period. Annual life cycles, including seasonal timing and duration of reproducti...
<p>A. Plot of osteocyte lacunar density on body mass of different taxa on a double logarith... more <p>A. Plot of osteocyte lacunar density on body mass of different taxa on a double logarithmic scale. Lines are the phylogenetic controlled regression lines of the respective taxonomic group. Solid lines represent significant regression models. The scattered line represents a regression model where the slope is not significant different from zero using a significant level of 0.05. For details of the regression models see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0077109#pone-0077109-t003" target="_blank">Table 3</a>. black circles = mammals, red circles = sauropodomorphs, blue open squares = amphibians, yellow squares = theropods, orange triangles = birds, green circles = reptiles, cross = diadectomorphs, star/pentagram = pterosaurs, square with triangle = “pelycosaurs”. <b>B</b>. Studied species in comparison to the mammal regression model (solid line). Scattered lines are 95% prediction intervals of the mammal regression model. Symbols as in <b>A</b>.</p
Advancing Methods, Analysis, and Interpretation, 2013
ABSTRACT To study the evolution of growth rates, it is necessary to develop two things: a sense o... more ABSTRACT To study the evolution of growth rates, it is necessary to develop two things: a sense of the ontogenetic patterns of individual species, and a phylogeny of the spe- cies in question. Studying ontogenies in phylogenetic context is the best approach to understanding how growth rates evolve.
Osteocytes harbour much potential for paleobiological studies. Synchrotron radiation and spectros... more Osteocytes harbour much potential for paleobiological studies. Synchrotron radiation and spectroscopic analyses are providing fascinating data on osteocyte density, size and orientation in fossil taxa. However, such studies may be costly and time consuming. Here we describe an uncomplicated and inexpensive method to measure osteocyte lacunar densities in bone thin sections. We report on cell lacunar densities in the long bones of various extant and extinct tetrapods, with a focus on sauropodomorph dinosaurs, and how lacunar densities can help us understand bone formation rates in the iconic sauropod dinosaurs. Ordinary least square and phylogenetic generalized least square regressions suggest that sauropodomorphs have lacunar densities higher than scaled up or comparably sized mammals. We also found normal mammalian-like osteocyte densities for the extinct bovid Myotragus, questioning its crocodilian-like physiology. When accounting for body mass effects and phylogeny, growth rates ...
Titanosaurian sauropods include the largest land animals that ever walked on Earth. However, some... more Titanosaurian sauropods include the largest land animals that ever walked on Earth. However, some of them evolved into dwarfed species, linked to their insular habitats. Here, we report on the long bone histology of several mature individuals of the small-sized titanosaur Atsinganosaurus velauciensis (Garcia et al., 2010) from the Upper Cretaceous of Velaux – La Bastide Neuve (Provence, South-Eastern France). The completely remodelled H bone tissue type in all specimens characterizes mature and fully grown individuals. Together with the extensive bone remodelling, the samples record HOS (Histological Ontogenetic Stages) 14 and range from RS (Remodeling Stages) 13 to 14. Considering the reduced size of the sampled femur and humeri, the remodelling process would have begun early in the ontogeny of this titanosaur compared to non-titanosaurian sauropods, at a rate that surpassed the apposition rate. Thus, size reduction of A. velauciensis has to be taken into account to explain the adv...
Long bone histology of basalmost and derived Sauropodomorpha: the convergence of fibrolamellar bo... more Long bone histology of basalmost and derived Sauropodomorpha: the convergence of fibrolamellar bone and the evolution of giantism and nanism Dissertation zur
Remains of Garrigatitan meridionalis nov. gen. et sp. were found in two bonebeds of sequence 2 fr... more Remains of Garrigatitan meridionalis nov. gen. et sp. were found in two bonebeds of sequence 2 from the upper Campanian site of Velaux-La Bastide Neuve (Aix-en-Provence Basin, Bouches du Rhône department). The vertebrate assemblage is dominated by dinosaurs, including the titanosaur Atsinganosaurus velauciensis. Garrigatitan meridionalis presents three diagnostic characters: hourglass-shaped humeri (proximal and distal thirds of almost the same transversal width) in anterior and posterior views, ilium with a broad rounded hollow slightly posterior to the base of the pubic peduncle, proximolateral margin of the femur only slightly medially deflected. Garrigatitan was a small to medium-sized sauropod (sub/adult individuals between 4–6 metres and 2–2.5 tonnes), showing anatomical differences with Atsinganosaurus, and with the other Late Cretaceous Ibero-Armorican titanosaurs. Large titanosaurian specimens found at Velaux-La Bastide Neuve could belong to adult Garrigatitan individuals r...
Many recent studies using next generation technologies to unravel exceptional molecular preservat... more Many recent studies using next generation technologies to unravel exceptional molecular preservation have changed our view on the limits of biomolecular stability during fossilization. Nevertheless, common hard tissues have not attracted much attention. Thus, the color change of vertebrate hard tissues from in vivo white to blackish-brown in many fossils is generally considered to be based on colored minerals. However, our results show that Maillard reaction products and porphyrins are the main staining agents in vertebrate hard tissues such as bones, eggshells, teeth, and fish scales. These hard tissue matrices yield structural proteins and glycosaminglycans extracellularly, which give rise to Maillard reaction products; intracellularly they represent a source of hemes. We analyzed samples of dinosaur, crocodile, mammal, and paleonisciform hard tissues covering a broad range of age, locality, and chemotaphonomic environments. Using Raman and UV/Vis spectrophotometry, ToF SIMS, EMPA and Powder XRD for demineralized fossil hard tissues, we identified a broad range of Maillard-based modifications in preserved oligopeptides with secondary structures derived from the extracellular matrix (ECM), and protein-cleaved, heme-derived porphyrins from within fossil osteocytes. All analyzed samples contained no brownish-staining crystalline minerals. This demonstrates that diagenetic staining is based on two different preservation phenomena: Firstly, Maillard-staining produces a brownish to blackish hue of the preserved ECM resulting from demineralization of bones (patches up to 500 µm), eggshells, teeth, and scales (patches up to 20 µm). Secondly, hemes clustering alongside osteocyte inner structures contribute to the diagenetic staining of bones by superimposing layers of dark orange-to reddish-brown osteocyte centers. The color of fossilized hard tissues is mainly determined by the type of amino acids reacting with the reducing sugar and their exposure time, as well as the character of post-Maillard modifications due to pH, Eh, and the water content of the surrounding sediment. This study not only rectifies a common misconception regarding the origin of diagenetic color in hard tissues, it also offers an explanation for the fossilization of peptide secondary structures: Intra-peptide Maillard-crosslinks between amino acids which are adjacent in a folded conformation may contribute to their preservation. The possibility that Maillard-crosslinks are the key to the fossilization of proteinaceous biomolecules suggests a new avenue for investigation.
The Cretaceous–Palaeogene mass extinction around 66 million years ago was triggered by the Chicxu... more The Cretaceous–Palaeogene mass extinction around 66 million years ago was triggered by the Chicxulub asteroid impact on the present-day Yucatán Peninsula1,2. This event caused the highly selective extinction that eliminated about 76% of species3,4, including all non-avian dinosaurs, pterosaurs, ammonites, rudists and most marine reptiles. The timing of the impact and its aftermath have been studied mainly on millennial timescales, leaving the season of the impact unconstrained. Here, by studying fishes that died on the day the Mesozoic era ended, we demonstrate that the impact that caused the Cretaceous–Palaeogene mass extinction took place during boreal spring. Osteohistology together with stable isotope records of exceptionally preserved perichondral and dermal bones in acipenseriform fishes from the Tanis impact-induced seiche deposits5 reveal annual cyclicity across the final years of the Cretaceous period. Annual life cycles, including seasonal timing and duration of reproducti...
<p>A. Plot of osteocyte lacunar density on body mass of different taxa on a double logarith... more <p>A. Plot of osteocyte lacunar density on body mass of different taxa on a double logarithmic scale. Lines are the phylogenetic controlled regression lines of the respective taxonomic group. Solid lines represent significant regression models. The scattered line represents a regression model where the slope is not significant different from zero using a significant level of 0.05. For details of the regression models see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0077109#pone-0077109-t003" target="_blank">Table 3</a>. black circles = mammals, red circles = sauropodomorphs, blue open squares = amphibians, yellow squares = theropods, orange triangles = birds, green circles = reptiles, cross = diadectomorphs, star/pentagram = pterosaurs, square with triangle = “pelycosaurs”. <b>B</b>. Studied species in comparison to the mammal regression model (solid line). Scattered lines are 95% prediction intervals of the mammal regression model. Symbols as in <b>A</b>.</p
Advancing Methods, Analysis, and Interpretation, 2013
ABSTRACT To study the evolution of growth rates, it is necessary to develop two things: a sense o... more ABSTRACT To study the evolution of growth rates, it is necessary to develop two things: a sense of the ontogenetic patterns of individual species, and a phylogeny of the spe- cies in question. Studying ontogenies in phylogenetic context is the best approach to understanding how growth rates evolve.
Osteocytes harbour much potential for paleobiological studies. Synchrotron radiation and spectros... more Osteocytes harbour much potential for paleobiological studies. Synchrotron radiation and spectroscopic analyses are providing fascinating data on osteocyte density, size and orientation in fossil taxa. However, such studies may be costly and time consuming. Here we describe an uncomplicated and inexpensive method to measure osteocyte lacunar densities in bone thin sections. We report on cell lacunar densities in the long bones of various extant and extinct tetrapods, with a focus on sauropodomorph dinosaurs, and how lacunar densities can help us understand bone formation rates in the iconic sauropod dinosaurs. Ordinary least square and phylogenetic generalized least square regressions suggest that sauropodomorphs have lacunar densities higher than scaled up or comparably sized mammals. We also found normal mammalian-like osteocyte densities for the extinct bovid Myotragus, questioning its crocodilian-like physiology. When accounting for body mass effects and phylogeny, growth rates ...
Titanosaurian sauropods include the largest land animals that ever walked on Earth. However, some... more Titanosaurian sauropods include the largest land animals that ever walked on Earth. However, some of them evolved into dwarfed species, linked to their insular habitats. Here, we report on the long bone histology of several mature individuals of the small-sized titanosaur Atsinganosaurus velauciensis (Garcia et al., 2010) from the Upper Cretaceous of Velaux – La Bastide Neuve (Provence, South-Eastern France). The completely remodelled H bone tissue type in all specimens characterizes mature and fully grown individuals. Together with the extensive bone remodelling, the samples record HOS (Histological Ontogenetic Stages) 14 and range from RS (Remodeling Stages) 13 to 14. Considering the reduced size of the sampled femur and humeri, the remodelling process would have begun early in the ontogeny of this titanosaur compared to non-titanosaurian sauropods, at a rate that surpassed the apposition rate. Thus, size reduction of A. velauciensis has to be taken into account to explain the adv...
Long bone histology of basalmost and derived Sauropodomorpha: the convergence of fibrolamellar bo... more Long bone histology of basalmost and derived Sauropodomorpha: the convergence of fibrolamellar bone and the evolution of giantism and nanism Dissertation zur
Remains of Garrigatitan meridionalis nov. gen. et sp. were found in two bonebeds of sequence 2 fr... more Remains of Garrigatitan meridionalis nov. gen. et sp. were found in two bonebeds of sequence 2 from the upper Campanian site of Velaux-La Bastide Neuve (Aix-en-Provence Basin, Bouches du Rhône department). The vertebrate assemblage is dominated by dinosaurs, including the titanosaur Atsinganosaurus velauciensis. Garrigatitan meridionalis presents three diagnostic characters: hourglass-shaped humeri (proximal and distal thirds of almost the same transversal width) in anterior and posterior views, ilium with a broad rounded hollow slightly posterior to the base of the pubic peduncle, proximolateral margin of the femur only slightly medially deflected. Garrigatitan was a small to medium-sized sauropod (sub/adult individuals between 4–6 metres and 2–2.5 tonnes), showing anatomical differences with Atsinganosaurus, and with the other Late Cretaceous Ibero-Armorican titanosaurs. Large titanosaurian specimens found at Velaux-La Bastide Neuve could belong to adult Garrigatitan individuals r...
Many recent studies using next generation technologies to unravel exceptional molecular preservat... more Many recent studies using next generation technologies to unravel exceptional molecular preservation have changed our view on the limits of biomolecular stability during fossilization. Nevertheless, common hard tissues have not attracted much attention. Thus, the color change of vertebrate hard tissues from in vivo white to blackish-brown in many fossils is generally considered to be based on colored minerals. However, our results show that Maillard reaction products and porphyrins are the main staining agents in vertebrate hard tissues such as bones, eggshells, teeth, and fish scales. These hard tissue matrices yield structural proteins and glycosaminglycans extracellularly, which give rise to Maillard reaction products; intracellularly they represent a source of hemes. We analyzed samples of dinosaur, crocodile, mammal, and paleonisciform hard tissues covering a broad range of age, locality, and chemotaphonomic environments. Using Raman and UV/Vis spectrophotometry, ToF SIMS, EMPA and Powder XRD for demineralized fossil hard tissues, we identified a broad range of Maillard-based modifications in preserved oligopeptides with secondary structures derived from the extracellular matrix (ECM), and protein-cleaved, heme-derived porphyrins from within fossil osteocytes. All analyzed samples contained no brownish-staining crystalline minerals. This demonstrates that diagenetic staining is based on two different preservation phenomena: Firstly, Maillard-staining produces a brownish to blackish hue of the preserved ECM resulting from demineralization of bones (patches up to 500 µm), eggshells, teeth, and scales (patches up to 20 µm). Secondly, hemes clustering alongside osteocyte inner structures contribute to the diagenetic staining of bones by superimposing layers of dark orange-to reddish-brown osteocyte centers. The color of fossilized hard tissues is mainly determined by the type of amino acids reacting with the reducing sugar and their exposure time, as well as the character of post-Maillard modifications due to pH, Eh, and the water content of the surrounding sediment. This study not only rectifies a common misconception regarding the origin of diagenetic color in hard tissues, it also offers an explanation for the fossilization of peptide secondary structures: Intra-peptide Maillard-crosslinks between amino acids which are adjacent in a folded conformation may contribute to their preservation. The possibility that Maillard-crosslinks are the key to the fossilization of proteinaceous biomolecules suggests a new avenue for investigation.
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