Turtles (Testudinata) are a diverse group of amniotes that have a rich fossil record that extends... more Turtles (Testudinata) are a diverse group of amniotes that have a rich fossil record that extends back to the Late Triassic, but little is known about global patterns of disparity through time.We here investigate the cranial disparity of 172 representatives of the turtle lineage and their ancestors grouped into 20 time bins ranging from the Late Triassic until the Recent using two-dimensional geometric morphometrics. Three evolutionary phases are apparent in all three anatomical views investigated. In the first phase, disparity increases gradually from the Late Triassic to the Palaeogene with only a minor perturbation at the K/Textinct event. Although globalwarming may have influenced this increase, we find the Mesozoic fragmentation of Pangaea to be a more plausible factor. Following its maximum, disparity decreases strongly towards the Miocene, only to recover partially towards the Recent. The marked collapse in disparity is likely a result of habitat destruction caused by global drying, combined with the homogenization of global turtle faunas that resulted from increased transcontinental dispersal in the Tertiary. The disparity minimum in the Miocene is likely an artefact of poor sampling.
Turtles (Testudinata) are a diverse group of reptiles that conquered a broad set of habitats and ... more Turtles (Testudinata) are a diverse group of reptiles that conquered a broad set of habitats and feeding ecologies over the course of their well-documented evolutionary history. We here investigate the cranial shape of 171 representatives of the turtle lineage and the relationship of shape to different habitat and diet preferences using two-dimensional geometric morphometrics. The skull shape of extant turtles correlates with both ecological proxies, but is more affected by habitat than diet. However, the application of these correlations to extinct turtles produces mostly flawed results, as least when compared to external data such as sedimentary environment, highlighting that the morphospace held by extant turtles is not necessarily the optimal location in tree space for a particular ecology. The inability of this study to correctly predict the ecology of extinct turtles is likely related to the fact that the shape of turtle skulls is dominated by the emarginations and jaw closure mechanisms, two shape features unrelated to habitat or feeding ecology. This indicates that various specializations that are apparent in the skull only contribute little to overall shape.
Background: Archosauromorpha originated in the middle–late Permian, radiated during the Triassic,... more Background: Archosauromorpha originated in the middle–late Permian, radiated during the Triassic, and gave rise to the crown group Archosauria, a highly successful clade of reptiles in terrestrial ecosystems over the last 250 million years. However, scientific attention has mainly focused on the diversification of archosaurs, while their stem lineage (i.e. non-archosaurian archosauromorphs) has often been overlooked in discussions of the evolutionary success of Archosauria. Here, we analyse the cranial disparity of late Permian to Early Jurassic archosauromorphs and make comparisons between non-archosaurian archosauromorphs and archosaurs (including Pseudosuchia and Ornithodira) on the basis of two-dimensional geometric morphometrics.
Non-avian saurischian skulls underwent at least 165 million years of evolution and shapes varied ... more Non-avian saurischian skulls underwent at least 165 million years of evolution and shapes varied from elongated skulls, such as in the theropod Coelophysis, to short and box-shaped skulls, such as in the sauropod Camarasaurus. A number of factors have long been considered to drive skull shape, including phylogeny, dietary preferences and functional constraints. However, heterochrony is increasingly being recognized as an important factor in dinosaur evolution. In order to quantitatively analyse the impact of heterochrony on saurischian skull shape, we analysed five ontogenetic trajectories using two-dimensional geometric morphometrics in a phylogenetic framework. This allowed for the comparative investigation of main ontogenetic shape changes and the evaluation of how heterochrony affected skull shape through both ontogenetic and phylogenetic trajectories. Using principal component analyses and multivariate regressions, it was possible to quantify different ontogenetic trajectories and evaluate them for evidence of heterochronic events allowing testing of previous hypotheses on cranial heterochrony in saurischians. We found that the skull shape of the hypothetical ancestor of Saurischia likely led to basal Sauropodomorpha through paedomorphosis, and to basal Theropoda mainly through peramorphosis. Paedomorphosis then led from Orionides to Avetheropoda, indicating that the paedomorphic trend found by previous authors in advanced coelurosaurs may extend back into the early evolution of Avetheropoda. Not only are changes in saurischian skull shape complex due to the large number of factors that affected it, but heterochrony itself is complex, with a number of possible reversals throughout non-avian saurischian evolution. In general, the sampling of complete ontogenetic trajectories including early juveniles is considerably lower than the sampling of single adult or subadult individuals, which is a major impediment to the study of heterochrony on non-avian dinosaurs. Thus, the current work represents an exploratory analysis. To better understand the cranial ontogeny and the impact of heterochrony on skull evolution in saurischians, the data set that we present here must be expanded and complemented with further sampling from future fossil discoveries, especially of juvenile individuals.
Ein neuer Fund des Urvogels Archaeopteryx mit besonders gut erhaltenen Abdrücken des Federkleids ... more Ein neuer Fund des Urvogels Archaeopteryx mit besonders gut erhaltenen Abdrücken des Federkleids und ein Vergleich mit anderen gefiederten Raubdinosauriern lässt erahnen: Federn entstanden nicht zum Fliegen – und die ersten »Flügel« der Vogelvorfahren wahrscheinlich auch nicht!
Chroniosuchians are an enigmatic Permian to Triassic group of crocodile-like basal tetrapods. The... more Chroniosuchians are an enigmatic Permian to Triassic group of crocodile-like basal tetrapods. Their conspicuous dorsal osteoderm systems include most of the group's yet documented postcranial morphological variability but have hardly been considered in cladistic approaches. Aiming at the clarification of the internal relationships of the Chroniosuchia, we have carried out a parsimony analysis including, among others, 23 morphological and osteohistological osteoderm characters and 12 chroniosuchian taxa. According to the most parsimonious trees, taxa usually referred to Chroniosuchidae form a paraphyletic succession with Madygenerpeton pustulatus and Chroniosaurus dongusensis as the basalmost chroniosuchians and Uralerpeton tverdochlebovae as the sister group of Bystrowianidae (hypothesis A). However, the concurrent hypothesis of a basal split into monophyletic subtaxa Chroniosuchidae and Bystrowianidae (hypothesis B) is only slightly less parsimonious and supported by an alternative analysis which includes embolomeres as the only reptiliomorph outgroup.
Auch mehr als 150 Jahre nach den ersten Funden des Urvogels Archaeopteryx halten die Fossilien di... more Auch mehr als 150 Jahre nach den ersten Funden des Urvogels Archaeopteryx halten die Fossilien dieses Tieres noch neue Erkenntnisse und neue Überraschungen bereit. Detaillierte Untersuchungen der bekannten Exemplare, oft mit neuen oder verbesserten Methoden, so wie der UV-Photographie oder Untersuchungen im Synchrotron-Computertomographen, und natürlich neue Exemplare helfen, strittige Fragen über die
Anatomie dieser »Ikone der Evolutionsbiologie« zu klären und somit ihren Lebensstil und ihre Bedeutung für unser Verständnis des Ursprunges der Vögel besser zu verstehen. Untersuchungen am Schädel des 10. (Thermopolis) und 7. (Münchener) Exemplares zeigen, dass der Schädel weniger dem der heutigen Vögel, aber sehr jenem der fortschrittlichen Raubdinosaurier ähnelt. Dem entgegen mutet das Gefieder des Urvogels schon sehr modern an, sowohl in Hinsicht auf die Körperbedeckung mit Konturfedern, als auch auf den Bau der Armschwingen. Der Hinterlauf war körpernah mit langen Federn bedeckt, die offenbar eine Art Federhose bildeten, ähnlich der heutiger Raubvögel. Die Schwanzfedern waren deutlich länger als bisher gedacht und standen mehr nach hinten ab, anstatt seitlich, wie in vielen Rekonstruktionen zu sehen. Offenbar spielte der Schwanz auch beim Flugvermögen von Archaeopteryx eine wichtige Rolle. Die echten Konturfedern entstanden bei den Raubdinosauriern offenbar nicht primär im Zusammenhang mit dem Flugvermögen; sie mögen ursprünglich hauptsächlich eine Signalfunktion gehabt haben. Nachdem solche Strukturen aber einmal vorhanden waren, konnten sie zu anderen Funktionen adaptiert werden. Eine dieser Funktionen ist der Flug, der eventuell bei den Raubdinosauriern mehr als einmal entstanden ist.
In a recent paper, Zheng et al. (1) studied the presence and absence of sternal elements within t... more In a recent paper, Zheng et al. (1) studied the presence and absence of sternal elements within the pectoral girdle of three paravian theropods (Anchiornis, Jeholornis, and Sapeornis) from the Jehol Biota of China, which are each known from a number of specimens. Based on the consistent absence of any traces of sternal elements in Anchiornis and Sapeornis, but the frequent perseveration of soft tissues (e.g., feathers) in the sediments of the Jehol Biota, the authors conclude that sternal elements were completely absent in these taxa, even as chondral elements. Because of the lack of ossified sternal elements, Zheng et al. conclude the same for Archaeopteryx, and finally propose the complete absence of sternal elements as plesiomorphic condition for Avialae and that the sternal elements of basal birds are not homologous to those of Oviraptorosauria or Dromaeosauridae.
Discoveries of bird-like theropod dinosaurs and basal avialans in recent decades have helped to p... more Discoveries of bird-like theropod dinosaurs and basal avialans in recent decades have helped to put the iconic ‘Urvogel’ Archaeopteryx1 into context and have yielded important new data on the origin and early evolution of feathers. However, the biological context under which pennaceous feathers evolved is still debated. Here we describe a new specimen of Archaeopteryx with extensive feather preservation, not only on the wings and tail, but also on the body and legs. The new specimen shows that the entire body was covered in pennaceous feathers, and that the hindlimbs had long, symmetrical feathers along the tibiotarsus but short feathers on the tarsometatarsus. Furthermore, the wing plumage demonstrates that several recent interpretations are problematic. An analysis of the phylogenetic distribution of pennaceous feathers on the tail, hindlimb and arms of advanced maniraptorans and basal avialans strongly indicates that these structures evolved in a functional context other than flight, most probably in relation to display, as suggested by some previous studies. Pennaceous feathers thus represented an exaptation and were later, in several lineages and following different patterns, recruited for aerodynamic functions. This indicates that the origin of flight in avialans was more complex than previously thought and might have involved several convergent achievements of aerial abilities.
Melanosuchus niger is a caimanine alligatorid widely distributed in the northern region of South ... more Melanosuchus niger is a caimanine alligatorid widely distributed in the northern region of South America. This species has been the focus of several ecological, genetic and morphological studies. However, morphological studies have generally been limited to examination of interspecific variation among extant species of South American crocodylians. Here, we present the first study of intraspecific variation in the skull of M. niger using a two-dimensional geometric morphometric approach. The crania of 52 sexed individuals varying in size were analysed to quantify shape variation and to assign observed shape changes to different types of intraspecific variation, that is, ontogenetic variation and sexual dimorphism. Most of the variation in this species is ontogenetic variation in snout length, skull depth, orbit size and the width of the postorbital region. These changes are correlated with bite force performance and probably dietary changes. However, a comparison with previous functional studies reveals that functional adaptations during ontogeny seem to be primarily restricted to the postrostral region, whereas rostral shape changes are more related to dietary shifts. Furthermore, the skulls of M. niger exhibit a sexual dimorphism, which is primarily size-related. The presence of non-size-related sexual dimorphism has to be tested in future examinations.
Several studies investigating macroevolutionary skull shape variation in fossil reptiles were pub... more Several studies investigating macroevolutionary skull shape variation in fossil reptiles were published recently, often using skull reconstructions taken from the scientific literature. However, this approach could be potentially problematic, because skull reconstructions might differ notably due to incompleteness and/or deformation of the material. Furthermore, the influence of intraspecific variation has usually not been explored in these studies. Both points could influence the results of morphometric analyses by affecting the relative position of species to each other within the morphospace. The aim of the current study is to investigate the variation in morphometric data between skull reconstructions based on the same specimen, and to compare the results to shape variation occurring in skull reconstructions based on different specimens of the same species (intraspecific variation) and skulls of closely related species (intraspecific variation). Based on the current results, shape variation of different skull reconstructions based on the same specimen seems to have generally little influence on the results of a geometric morphometric analysis, although it cannot be excluded that some erroneous reconstructions of poorly preserved specimens might cause problems occasionally. In contrast, for different specimens of the same species the variation is generally higher than between different reconstructions based on the same specimen. For closely related species, at least with similar ecological preferences in respect to the dietary spectrum, the degree of interspecific variation can overlap with that of intraspecific variation, most probably due to similar biomechanical constraints. Citation: Foth C, Rauhut OWM (2013) The Good, the Bad, and the Ugly: The Influence of Skull Reconstructions and Intraspecific Variability in Studies of
O.W.M. 2013. Macroevolutionary and morphofunctional patterns in theropod skulls: A morpho− metric... more O.W.M. 2013. Macroevolutionary and morphofunctional patterns in theropod skulls: A morpho− metric approach. Acta Palaeontologica Polonica 58 (1): 1-16.
Turtles (Testudinata) are a diverse group of amniotes that have a rich fossil record that extends... more Turtles (Testudinata) are a diverse group of amniotes that have a rich fossil record that extends back to the Late Triassic, but little is known about global patterns of disparity through time.We here investigate the cranial disparity of 172 representatives of the turtle lineage and their ancestors grouped into 20 time bins ranging from the Late Triassic until the Recent using two-dimensional geometric morphometrics. Three evolutionary phases are apparent in all three anatomical views investigated. In the first phase, disparity increases gradually from the Late Triassic to the Palaeogene with only a minor perturbation at the K/Textinct event. Although globalwarming may have influenced this increase, we find the Mesozoic fragmentation of Pangaea to be a more plausible factor. Following its maximum, disparity decreases strongly towards the Miocene, only to recover partially towards the Recent. The marked collapse in disparity is likely a result of habitat destruction caused by global drying, combined with the homogenization of global turtle faunas that resulted from increased transcontinental dispersal in the Tertiary. The disparity minimum in the Miocene is likely an artefact of poor sampling.
Turtles (Testudinata) are a diverse group of reptiles that conquered a broad set of habitats and ... more Turtles (Testudinata) are a diverse group of reptiles that conquered a broad set of habitats and feeding ecologies over the course of their well-documented evolutionary history. We here investigate the cranial shape of 171 representatives of the turtle lineage and the relationship of shape to different habitat and diet preferences using two-dimensional geometric morphometrics. The skull shape of extant turtles correlates with both ecological proxies, but is more affected by habitat than diet. However, the application of these correlations to extinct turtles produces mostly flawed results, as least when compared to external data such as sedimentary environment, highlighting that the morphospace held by extant turtles is not necessarily the optimal location in tree space for a particular ecology. The inability of this study to correctly predict the ecology of extinct turtles is likely related to the fact that the shape of turtle skulls is dominated by the emarginations and jaw closure mechanisms, two shape features unrelated to habitat or feeding ecology. This indicates that various specializations that are apparent in the skull only contribute little to overall shape.
Background: Archosauromorpha originated in the middle–late Permian, radiated during the Triassic,... more Background: Archosauromorpha originated in the middle–late Permian, radiated during the Triassic, and gave rise to the crown group Archosauria, a highly successful clade of reptiles in terrestrial ecosystems over the last 250 million years. However, scientific attention has mainly focused on the diversification of archosaurs, while their stem lineage (i.e. non-archosaurian archosauromorphs) has often been overlooked in discussions of the evolutionary success of Archosauria. Here, we analyse the cranial disparity of late Permian to Early Jurassic archosauromorphs and make comparisons between non-archosaurian archosauromorphs and archosaurs (including Pseudosuchia and Ornithodira) on the basis of two-dimensional geometric morphometrics.
Non-avian saurischian skulls underwent at least 165 million years of evolution and shapes varied ... more Non-avian saurischian skulls underwent at least 165 million years of evolution and shapes varied from elongated skulls, such as in the theropod Coelophysis, to short and box-shaped skulls, such as in the sauropod Camarasaurus. A number of factors have long been considered to drive skull shape, including phylogeny, dietary preferences and functional constraints. However, heterochrony is increasingly being recognized as an important factor in dinosaur evolution. In order to quantitatively analyse the impact of heterochrony on saurischian skull shape, we analysed five ontogenetic trajectories using two-dimensional geometric morphometrics in a phylogenetic framework. This allowed for the comparative investigation of main ontogenetic shape changes and the evaluation of how heterochrony affected skull shape through both ontogenetic and phylogenetic trajectories. Using principal component analyses and multivariate regressions, it was possible to quantify different ontogenetic trajectories and evaluate them for evidence of heterochronic events allowing testing of previous hypotheses on cranial heterochrony in saurischians. We found that the skull shape of the hypothetical ancestor of Saurischia likely led to basal Sauropodomorpha through paedomorphosis, and to basal Theropoda mainly through peramorphosis. Paedomorphosis then led from Orionides to Avetheropoda, indicating that the paedomorphic trend found by previous authors in advanced coelurosaurs may extend back into the early evolution of Avetheropoda. Not only are changes in saurischian skull shape complex due to the large number of factors that affected it, but heterochrony itself is complex, with a number of possible reversals throughout non-avian saurischian evolution. In general, the sampling of complete ontogenetic trajectories including early juveniles is considerably lower than the sampling of single adult or subadult individuals, which is a major impediment to the study of heterochrony on non-avian dinosaurs. Thus, the current work represents an exploratory analysis. To better understand the cranial ontogeny and the impact of heterochrony on skull evolution in saurischians, the data set that we present here must be expanded and complemented with further sampling from future fossil discoveries, especially of juvenile individuals.
Ein neuer Fund des Urvogels Archaeopteryx mit besonders gut erhaltenen Abdrücken des Federkleids ... more Ein neuer Fund des Urvogels Archaeopteryx mit besonders gut erhaltenen Abdrücken des Federkleids und ein Vergleich mit anderen gefiederten Raubdinosauriern lässt erahnen: Federn entstanden nicht zum Fliegen – und die ersten »Flügel« der Vogelvorfahren wahrscheinlich auch nicht!
Chroniosuchians are an enigmatic Permian to Triassic group of crocodile-like basal tetrapods. The... more Chroniosuchians are an enigmatic Permian to Triassic group of crocodile-like basal tetrapods. Their conspicuous dorsal osteoderm systems include most of the group's yet documented postcranial morphological variability but have hardly been considered in cladistic approaches. Aiming at the clarification of the internal relationships of the Chroniosuchia, we have carried out a parsimony analysis including, among others, 23 morphological and osteohistological osteoderm characters and 12 chroniosuchian taxa. According to the most parsimonious trees, taxa usually referred to Chroniosuchidae form a paraphyletic succession with Madygenerpeton pustulatus and Chroniosaurus dongusensis as the basalmost chroniosuchians and Uralerpeton tverdochlebovae as the sister group of Bystrowianidae (hypothesis A). However, the concurrent hypothesis of a basal split into monophyletic subtaxa Chroniosuchidae and Bystrowianidae (hypothesis B) is only slightly less parsimonious and supported by an alternative analysis which includes embolomeres as the only reptiliomorph outgroup.
Auch mehr als 150 Jahre nach den ersten Funden des Urvogels Archaeopteryx halten die Fossilien di... more Auch mehr als 150 Jahre nach den ersten Funden des Urvogels Archaeopteryx halten die Fossilien dieses Tieres noch neue Erkenntnisse und neue Überraschungen bereit. Detaillierte Untersuchungen der bekannten Exemplare, oft mit neuen oder verbesserten Methoden, so wie der UV-Photographie oder Untersuchungen im Synchrotron-Computertomographen, und natürlich neue Exemplare helfen, strittige Fragen über die
Anatomie dieser »Ikone der Evolutionsbiologie« zu klären und somit ihren Lebensstil und ihre Bedeutung für unser Verständnis des Ursprunges der Vögel besser zu verstehen. Untersuchungen am Schädel des 10. (Thermopolis) und 7. (Münchener) Exemplares zeigen, dass der Schädel weniger dem der heutigen Vögel, aber sehr jenem der fortschrittlichen Raubdinosaurier ähnelt. Dem entgegen mutet das Gefieder des Urvogels schon sehr modern an, sowohl in Hinsicht auf die Körperbedeckung mit Konturfedern, als auch auf den Bau der Armschwingen. Der Hinterlauf war körpernah mit langen Federn bedeckt, die offenbar eine Art Federhose bildeten, ähnlich der heutiger Raubvögel. Die Schwanzfedern waren deutlich länger als bisher gedacht und standen mehr nach hinten ab, anstatt seitlich, wie in vielen Rekonstruktionen zu sehen. Offenbar spielte der Schwanz auch beim Flugvermögen von Archaeopteryx eine wichtige Rolle. Die echten Konturfedern entstanden bei den Raubdinosauriern offenbar nicht primär im Zusammenhang mit dem Flugvermögen; sie mögen ursprünglich hauptsächlich eine Signalfunktion gehabt haben. Nachdem solche Strukturen aber einmal vorhanden waren, konnten sie zu anderen Funktionen adaptiert werden. Eine dieser Funktionen ist der Flug, der eventuell bei den Raubdinosauriern mehr als einmal entstanden ist.
In a recent paper, Zheng et al. (1) studied the presence and absence of sternal elements within t... more In a recent paper, Zheng et al. (1) studied the presence and absence of sternal elements within the pectoral girdle of three paravian theropods (Anchiornis, Jeholornis, and Sapeornis) from the Jehol Biota of China, which are each known from a number of specimens. Based on the consistent absence of any traces of sternal elements in Anchiornis and Sapeornis, but the frequent perseveration of soft tissues (e.g., feathers) in the sediments of the Jehol Biota, the authors conclude that sternal elements were completely absent in these taxa, even as chondral elements. Because of the lack of ossified sternal elements, Zheng et al. conclude the same for Archaeopteryx, and finally propose the complete absence of sternal elements as plesiomorphic condition for Avialae and that the sternal elements of basal birds are not homologous to those of Oviraptorosauria or Dromaeosauridae.
Discoveries of bird-like theropod dinosaurs and basal avialans in recent decades have helped to p... more Discoveries of bird-like theropod dinosaurs and basal avialans in recent decades have helped to put the iconic ‘Urvogel’ Archaeopteryx1 into context and have yielded important new data on the origin and early evolution of feathers. However, the biological context under which pennaceous feathers evolved is still debated. Here we describe a new specimen of Archaeopteryx with extensive feather preservation, not only on the wings and tail, but also on the body and legs. The new specimen shows that the entire body was covered in pennaceous feathers, and that the hindlimbs had long, symmetrical feathers along the tibiotarsus but short feathers on the tarsometatarsus. Furthermore, the wing plumage demonstrates that several recent interpretations are problematic. An analysis of the phylogenetic distribution of pennaceous feathers on the tail, hindlimb and arms of advanced maniraptorans and basal avialans strongly indicates that these structures evolved in a functional context other than flight, most probably in relation to display, as suggested by some previous studies. Pennaceous feathers thus represented an exaptation and were later, in several lineages and following different patterns, recruited for aerodynamic functions. This indicates that the origin of flight in avialans was more complex than previously thought and might have involved several convergent achievements of aerial abilities.
Melanosuchus niger is a caimanine alligatorid widely distributed in the northern region of South ... more Melanosuchus niger is a caimanine alligatorid widely distributed in the northern region of South America. This species has been the focus of several ecological, genetic and morphological studies. However, morphological studies have generally been limited to examination of interspecific variation among extant species of South American crocodylians. Here, we present the first study of intraspecific variation in the skull of M. niger using a two-dimensional geometric morphometric approach. The crania of 52 sexed individuals varying in size were analysed to quantify shape variation and to assign observed shape changes to different types of intraspecific variation, that is, ontogenetic variation and sexual dimorphism. Most of the variation in this species is ontogenetic variation in snout length, skull depth, orbit size and the width of the postorbital region. These changes are correlated with bite force performance and probably dietary changes. However, a comparison with previous functional studies reveals that functional adaptations during ontogeny seem to be primarily restricted to the postrostral region, whereas rostral shape changes are more related to dietary shifts. Furthermore, the skulls of M. niger exhibit a sexual dimorphism, which is primarily size-related. The presence of non-size-related sexual dimorphism has to be tested in future examinations.
Several studies investigating macroevolutionary skull shape variation in fossil reptiles were pub... more Several studies investigating macroevolutionary skull shape variation in fossil reptiles were published recently, often using skull reconstructions taken from the scientific literature. However, this approach could be potentially problematic, because skull reconstructions might differ notably due to incompleteness and/or deformation of the material. Furthermore, the influence of intraspecific variation has usually not been explored in these studies. Both points could influence the results of morphometric analyses by affecting the relative position of species to each other within the morphospace. The aim of the current study is to investigate the variation in morphometric data between skull reconstructions based on the same specimen, and to compare the results to shape variation occurring in skull reconstructions based on different specimens of the same species (intraspecific variation) and skulls of closely related species (intraspecific variation). Based on the current results, shape variation of different skull reconstructions based on the same specimen seems to have generally little influence on the results of a geometric morphometric analysis, although it cannot be excluded that some erroneous reconstructions of poorly preserved specimens might cause problems occasionally. In contrast, for different specimens of the same species the variation is generally higher than between different reconstructions based on the same specimen. For closely related species, at least with similar ecological preferences in respect to the dietary spectrum, the degree of interspecific variation can overlap with that of intraspecific variation, most probably due to similar biomechanical constraints. Citation: Foth C, Rauhut OWM (2013) The Good, the Bad, and the Ugly: The Influence of Skull Reconstructions and Intraspecific Variability in Studies of
O.W.M. 2013. Macroevolutionary and morphofunctional patterns in theropod skulls: A morpho− metric... more O.W.M. 2013. Macroevolutionary and morphofunctional patterns in theropod skulls: A morpho− metric approach. Acta Palaeontologica Polonica 58 (1): 1-16.
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Papers by Christian Foth
of disparity through time.We here investigate the cranial disparity of 172 representatives of the turtle lineage and their ancestors grouped into 20 time bins ranging from the Late Triassic until the Recent using two-dimensional geometric morphometrics. Three evolutionary phases are apparent in all three anatomical views investigated. In the first phase, disparity increases gradually from the Late Triassic to the Palaeogene with only a minor perturbation at the K/Textinct event. Although globalwarming may have influenced this increase, we find the Mesozoic fragmentation of Pangaea to be a more plausible factor. Following its maximum, disparity decreases strongly towards the Miocene, only to recover partially towards the Recent. The marked collapse in disparity is likely a result of habitat destruction caused by global drying, combined with the homogenization of global turtle faunas that resulted from increased transcontinental dispersal in the Tertiary. The disparity minimum in the Miocene is likely an artefact of poor sampling.
Anatomie dieser »Ikone der Evolutionsbiologie« zu klären und somit ihren Lebensstil und ihre Bedeutung für unser Verständnis des Ursprunges der Vögel besser zu verstehen. Untersuchungen am Schädel des 10. (Thermopolis) und 7. (Münchener) Exemplares zeigen, dass der Schädel weniger dem der heutigen Vögel, aber sehr jenem der fortschrittlichen Raubdinosaurier ähnelt. Dem entgegen mutet das Gefieder des Urvogels schon sehr modern an, sowohl in Hinsicht auf die Körperbedeckung mit Konturfedern, als auch auf den Bau der Armschwingen. Der Hinterlauf war körpernah mit langen Federn bedeckt, die offenbar eine Art Federhose bildeten, ähnlich der heutiger Raubvögel. Die Schwanzfedern waren deutlich länger als bisher gedacht und standen mehr nach hinten ab, anstatt seitlich, wie in vielen Rekonstruktionen zu sehen. Offenbar spielte der Schwanz auch beim Flugvermögen von Archaeopteryx eine wichtige Rolle. Die echten Konturfedern entstanden bei den Raubdinosauriern offenbar nicht primär im Zusammenhang mit dem Flugvermögen; sie mögen ursprünglich hauptsächlich eine Signalfunktion gehabt haben. Nachdem solche Strukturen aber einmal vorhanden waren, konnten sie zu anderen Funktionen adaptiert werden. Eine dieser Funktionen ist der Flug, der eventuell bei den Raubdinosauriern mehr als einmal entstanden ist.
of disparity through time.We here investigate the cranial disparity of 172 representatives of the turtle lineage and their ancestors grouped into 20 time bins ranging from the Late Triassic until the Recent using two-dimensional geometric morphometrics. Three evolutionary phases are apparent in all three anatomical views investigated. In the first phase, disparity increases gradually from the Late Triassic to the Palaeogene with only a minor perturbation at the K/Textinct event. Although globalwarming may have influenced this increase, we find the Mesozoic fragmentation of Pangaea to be a more plausible factor. Following its maximum, disparity decreases strongly towards the Miocene, only to recover partially towards the Recent. The marked collapse in disparity is likely a result of habitat destruction caused by global drying, combined with the homogenization of global turtle faunas that resulted from increased transcontinental dispersal in the Tertiary. The disparity minimum in the Miocene is likely an artefact of poor sampling.
Anatomie dieser »Ikone der Evolutionsbiologie« zu klären und somit ihren Lebensstil und ihre Bedeutung für unser Verständnis des Ursprunges der Vögel besser zu verstehen. Untersuchungen am Schädel des 10. (Thermopolis) und 7. (Münchener) Exemplares zeigen, dass der Schädel weniger dem der heutigen Vögel, aber sehr jenem der fortschrittlichen Raubdinosaurier ähnelt. Dem entgegen mutet das Gefieder des Urvogels schon sehr modern an, sowohl in Hinsicht auf die Körperbedeckung mit Konturfedern, als auch auf den Bau der Armschwingen. Der Hinterlauf war körpernah mit langen Federn bedeckt, die offenbar eine Art Federhose bildeten, ähnlich der heutiger Raubvögel. Die Schwanzfedern waren deutlich länger als bisher gedacht und standen mehr nach hinten ab, anstatt seitlich, wie in vielen Rekonstruktionen zu sehen. Offenbar spielte der Schwanz auch beim Flugvermögen von Archaeopteryx eine wichtige Rolle. Die echten Konturfedern entstanden bei den Raubdinosauriern offenbar nicht primär im Zusammenhang mit dem Flugvermögen; sie mögen ursprünglich hauptsächlich eine Signalfunktion gehabt haben. Nachdem solche Strukturen aber einmal vorhanden waren, konnten sie zu anderen Funktionen adaptiert werden. Eine dieser Funktionen ist der Flug, der eventuell bei den Raubdinosauriern mehr als einmal entstanden ist.