Pterosaurs are an extinct group of highly modified flying reptiles that thrived during the Mesozo... more Pterosaurs are an extinct group of highly modified flying reptiles that thrived during the Mesozoic. This group has unique and remarkable skeletal adaptations to powered flight, including pneumatic bones and an elongate digit IV supporting a wing-membrane. Two major body plans have traditionally been recognized: the primitive, primarily long-tailed paraphyletic ''rhamphorhynchoids'' (preferably currently recognized as non-pterodactyloids) and the derived short-tailed pterodactyloids. These two groups differ considerably in their general anatomy and also exhibit a remarkably different neuroanatomy and inferred head posture, which has been linked to different lifestyles and behaviours and improved flying capabilities in these reptiles. Pterosaur neuroanatomy, is known from just a few three-dimensionally preserved braincases of non-pterodactyloids (as Rhamphorhynchidae) and pterodactyloids, between which there is a large morphological gap. Here we report on a new Jurassic pterosaur from Argentina, Allkaruen koi gen. et sp. nov., remains of which include a superbly preserved , uncrushed braincase that sheds light on the origins of the highly derived neu-roanatomy of pterodactyloids and their close relatives. A µCT ray-generated virtual endocast shows that the new pterosaur exhibits a mosaic of plesiomorphic and derived traits of the inner ear and neuroanatomy that fills an important gap between those of non-monofenestratan breviquartossans (Rhamphorhynchidae) and derived pterodactyloids. These results suggest that, while modularity may play an important role at one anatomical level, at a finer level the evolution of structures within a module may follow a mosaic pattern.
We present a new medium-sized basal sauropodomorph, Sefapanosaurus zastronensis gen. et sp. nov.,... more We present a new medium-sized basal sauropodomorph, Sefapanosaurus zastronensis gen. et sp. nov., from the Upper Triassic−Lower Jurassic Elliot Formation of South Africa. It is represented by parts of the postcranial skeleton of at least four individuals, including: cervical, dorsal, sacral and caudal vertebrae, most of the forelimb, and part of the hindlimb. Sefapanosaurus bears several autapomorphies of the astragalus, and referred material also shows autapomorphic features. The inclusion of Sefapanosaurus in a phylogenetic analysis places it within the group of sauropodomorphs more closely related to sauropods than to Massospondylus (i.e. Sauropodiformes), increasing the currently known diversity of the so-called ‘transitional forms’ leading to Sauropoda. Character optimization revealed the presence of several features that are common for taxa placed within the transitional branches basal to Sauropoda. Sefapanosaurus, together with other transitional sauropodomorphs reported during the last decade, highlights the importance of Gondwanan taxa for understanding the palaeobiodiversity, global distribution, and macroevolutionary changes in the group related to the rise of sauropods.
Cropping out on the southeastern margin of the Somún Cura Plateau, the La Colonia Formation (Cam... more Cropping out on the southeastern margin of the Somún Cura Plateau, the La Colonia Formation (Cam- panianeMaastrichtian) has yielded, over the last several decades, a varied fossil tetrapod fauna (mam- mals, ophidians, turtles, dinosaurs, plesiosaurs, anurans). For this study several field trips were carried out specifically to recover reptile remains. Three sections, located on the southeastern slope of the Sierra de La Colonia and in the vicinity of Cerro Bayo, Chubut Province (Argentina), were selected for particular attention. The prospected sections are composed of massive, laminated or heterolithic siltstones and claystones, with scarce and thin intercalations of massive, heterolithic o cross-bedded fine sandstones and of fossiliferous conglomerates. The most abundantly recovered reptiles are terrestrial and freshwater turtles, followed by plesiosaurs and dinosaurs. Among the chelonians, more than 16 specimens of Patagoniaemys gasparinae (Meiolaniformes), three specimens of Yaminuechelys aff. Y. gasparinii (Cheli- dae), and the remains of a new genus of Chelidae were identified. Among the dinosaurs, theropod metatarsal fragments, an incomplete abelisaurid theropod skeleton, sauropod vertebrae, ankylosaur osteoderms and appendicular fragments of hadrosaurs were found. Among the plesiosaurs there are several well preserved elasmosaurids (including two with associated gastroliths) and a polycotylid (Sulcusuchus erraini). Except for the plesiosaurs, all the reptiles are terrestrial or freshwater taxa. How- ever, analysis of the elasmosaurids indicates they are adult specimens of small body size, which could be related to forms that lived in restricted aquatic environments. Likewise, the polycotylid possesses deep rostral and mandibular grooves, and a conspicuous vascularization and/or innervation, that is consistent with the presence of some associated special sensory structures similar to those known in some ceta- ceans that inhabit modern rivers and estuaries. Sedimentological analysis suggests that deposition would have been mostly in low-energy restricted environments, like muddy plains, marshes and ponds cut by meandering channels, probably in the central mixed-energy zone within an estuary. This interpretation is consistent with the habitat inferred for the recovered reptiles, as well as with associated foraminifers and with the probable origin of gastroliths found associate with the plesiosaurs.
The early Middle Jurassic is regarded as the period when sauropods diversified and be- came majo... more The early Middle Jurassic is regarded as the period when sauropods diversified and be- came major components of the terrestrial ecosystems. Not many sites yield sauropod mate- rial of this time; however, both cranial and postcranial material of eusauropods have been found in the Cañadón Asfalto Formation (latest Early Jurassic–early Middle Jurassic) in Central Patagonia (Argentina), which may help to shed light on the early evolution of eusauropods. These eusauropod remains include teeth associated with cranial and man- dibular material as well as isolated teeth found at different localities. In this study, an assem- blage of sauropod teeth from the Cañadón Asfalto Formation found in four different localities in the area of Cerro Condor (Chubut, Argentina) is used as a mean of assessing sauropod species diversity at these sites. By using dental enamel wrinkling, primarily based on the shape and orientation of grooves and crests of this wrinkling, we define and describe three different morphotypes. With the exception of one taxon, for which no cranial material is currently known, these morphotypes match the local eusauropod diversity as assessed based on postcranial material. Morphotype I is tentatively assigned to Patagosaurus, whereas morphotypes II and III correspond to new taxa, which are also distinguished by as- sociated postcranial material. This study thus shows that enamel wrinkling can be used as a tool in assessing sauropod diversity.
The theropod clade Carcharodontosauridae is a broadly distributed group of large allosauroid ther... more The theropod clade Carcharodontosauridae is a broadly distributed group of large allosauroid theropods. The
carcharodontosaurids recorded in the Albian – Cenomanian of Gondwana are the youngest and most derived members of this
clade. Tyrannotitan chubutensis, from the Cerro Castan˜ o Member of Cerro Barcino Formation (Albian; Chubut Group),
Central Patagonia, Argentina, is of prime interest among Gondwanan carcharodontosaurids as it represents the oldest record
of the group. Here we offer a detailed osteological comparative description of the holotype and paratype of Tyrannotitan
chubutensis together with a new diagnosis of the species. The new information results in a better understanding of this taxon
and Carcharodontosauridae. Furthermore, a comparative study of the anatomy of the pectoral girdle of Giganotosaurus is
reinterpreted as very similar to that of Tyrannotitan and Mapusaurus. We also present a phylogenetic analysis of
Carcharodontosauridae that recovers Tyrannotitan as a derived carcharodontosaurid, being the sister group of the clade
formed by Giganotosaurus and Mapusaurus, all nested in the clade Giganotosaurini
Ornithosuchidae is a group of Late Triassic pseudosuchian archosaurs of controversial phylogeneti... more Ornithosuchidae is a group of Late Triassic pseudosuchian archosaurs of controversial phylogenetic affinities. This clade currently comprises three taxa: Venaticosuchus rusconii and Riojasuchus tenuisceps, both from Argentina, and Ornithosuchus longidens, from Scotland. V. rusconii was erected on the basis of an incomplete skull with
articulated lower jaws and some elements of the postcranium that are currently lost. Venaticosuchus rusconii is redescribed here and included for the first time in a phylogenetic analysis to test its affinities with ornithosuchids. The bizarre morphology of V. rusconii has a unique combination of traits that distinguishes it from the other ornithosuchids, such as basipterygoid processes directed ventrally, dentary with the dorsal margin of the anterior end dorsally expanded, articular without a foramen on its medial side, and the absence of a surangular foramen, corroborating the validity of this taxon. V. rusconii is recovered as an ornithosuchid more closely related to R. tenuisceps than to O. longidens, based on the presence of a nearly pointed anterior margin of the antorbital fenestra, and a vertical bony strut of the jugal that separates the antorbital fenestra from the infratemporal fenestra
Methods improving the performance of molecular dating of divergence time of clades have improved ... more Methods improving the performance of molecular dating of divergence time of clades have improved dramatically in recent years.
The calibration of molecular dating using the first appearance of a clade in the fossil record is a crucial step towards inferring the
minimal diversification time of various groups and the choice of extinct taxa can strongly influence the molecular dates. Here, we
evaluate the uncertainty on the phylogenetic position of extinct taxa through non-parametric bootstrapping. The recognition of
phylogenetic uncertainty resulted in the definition of the Bootstrap Uncertainty Range (BUR) for the age of first appearance of a
given clade. The BUR is calculated as the interval of geological time in which the diversification of a given clade can be inferred to
have occurred, based on the temporal information of the fossil record and the topologies of the bootstrap trees. Divergence times
based on BUR analyses were calculated for three clades of turtles: Testudines, Pleurodira and Cryptodira. This resulted in extensive
uncertainty ranges of topology-dependent minimal divergence dates for these clades.
Annual Review of Earth and Planetary Sciences, May 2013
The idea that South America was an island continent over most of the Cenozoic, during which its u... more The idea that South America was an island continent over most of the Cenozoic, during which its unusual mammalian faunas evolved in isolation, is outstandingly influential in biogeography. Although large numbers of recent fossil discoveries and related advances require that it be significantly modified, the original isolation concept is still repeated in much current literature. The persistence of the idea inspired us to present here an integrated paleobiogeographic account of Jurassic to Paleogene mammals, reptiles, and plants from Patagonia, which has by far the richest fossil record on the continent. All three groups show distribution patterns that are broadly consistent with South America's long separation history, first from Laurasia by the Late Jurassic, then from Africa and India-Madagascar during the late Early Cretaceous, and finally from Antarctica and Australia during the early-middle Eocene, after which "isolation" finally commenced. We highlight areas of promising future research and provide ...
Pterosaurs are an extinct group of highly modified flying reptiles that thrived during the Mesozo... more Pterosaurs are an extinct group of highly modified flying reptiles that thrived during the Mesozoic. This group has unique and remarkable skeletal adaptations to powered flight, including pneumatic bones and an elongate digit IV supporting a wing-membrane. Two major body plans have traditionally been recognized: the primitive, primarily long-tailed paraphyletic ''rhamphorhynchoids'' (preferably currently recognized as non-pterodactyloids) and the derived short-tailed pterodactyloids. These two groups differ considerably in their general anatomy and also exhibit a remarkably different neuroanatomy and inferred head posture, which has been linked to different lifestyles and behaviours and improved flying capabilities in these reptiles. Pterosaur neuroanatomy, is known from just a few three-dimensionally preserved braincases of non-pterodactyloids (as Rhamphorhynchidae) and pterodactyloids, between which there is a large morphological gap. Here we report on a new Jurassic pterosaur from Argentina, Allkaruen koi gen. et sp. nov., remains of which include a superbly preserved , uncrushed braincase that sheds light on the origins of the highly derived neu-roanatomy of pterodactyloids and their close relatives. A µCT ray-generated virtual endocast shows that the new pterosaur exhibits a mosaic of plesiomorphic and derived traits of the inner ear and neuroanatomy that fills an important gap between those of non-monofenestratan breviquartossans (Rhamphorhynchidae) and derived pterodactyloids. These results suggest that, while modularity may play an important role at one anatomical level, at a finer level the evolution of structures within a module may follow a mosaic pattern.
We present a new medium-sized basal sauropodomorph, Sefapanosaurus zastronensis gen. et sp. nov.,... more We present a new medium-sized basal sauropodomorph, Sefapanosaurus zastronensis gen. et sp. nov., from the Upper Triassic−Lower Jurassic Elliot Formation of South Africa. It is represented by parts of the postcranial skeleton of at least four individuals, including: cervical, dorsal, sacral and caudal vertebrae, most of the forelimb, and part of the hindlimb. Sefapanosaurus bears several autapomorphies of the astragalus, and referred material also shows autapomorphic features. The inclusion of Sefapanosaurus in a phylogenetic analysis places it within the group of sauropodomorphs more closely related to sauropods than to Massospondylus (i.e. Sauropodiformes), increasing the currently known diversity of the so-called ‘transitional forms’ leading to Sauropoda. Character optimization revealed the presence of several features that are common for taxa placed within the transitional branches basal to Sauropoda. Sefapanosaurus, together with other transitional sauropodomorphs reported during the last decade, highlights the importance of Gondwanan taxa for understanding the palaeobiodiversity, global distribution, and macroevolutionary changes in the group related to the rise of sauropods.
Cropping out on the southeastern margin of the Somún Cura Plateau, the La Colonia Formation (Cam... more Cropping out on the southeastern margin of the Somún Cura Plateau, the La Colonia Formation (Cam- panianeMaastrichtian) has yielded, over the last several decades, a varied fossil tetrapod fauna (mam- mals, ophidians, turtles, dinosaurs, plesiosaurs, anurans). For this study several field trips were carried out specifically to recover reptile remains. Three sections, located on the southeastern slope of the Sierra de La Colonia and in the vicinity of Cerro Bayo, Chubut Province (Argentina), were selected for particular attention. The prospected sections are composed of massive, laminated or heterolithic siltstones and claystones, with scarce and thin intercalations of massive, heterolithic o cross-bedded fine sandstones and of fossiliferous conglomerates. The most abundantly recovered reptiles are terrestrial and freshwater turtles, followed by plesiosaurs and dinosaurs. Among the chelonians, more than 16 specimens of Patagoniaemys gasparinae (Meiolaniformes), three specimens of Yaminuechelys aff. Y. gasparinii (Cheli- dae), and the remains of a new genus of Chelidae were identified. Among the dinosaurs, theropod metatarsal fragments, an incomplete abelisaurid theropod skeleton, sauropod vertebrae, ankylosaur osteoderms and appendicular fragments of hadrosaurs were found. Among the plesiosaurs there are several well preserved elasmosaurids (including two with associated gastroliths) and a polycotylid (Sulcusuchus erraini). Except for the plesiosaurs, all the reptiles are terrestrial or freshwater taxa. How- ever, analysis of the elasmosaurids indicates they are adult specimens of small body size, which could be related to forms that lived in restricted aquatic environments. Likewise, the polycotylid possesses deep rostral and mandibular grooves, and a conspicuous vascularization and/or innervation, that is consistent with the presence of some associated special sensory structures similar to those known in some ceta- ceans that inhabit modern rivers and estuaries. Sedimentological analysis suggests that deposition would have been mostly in low-energy restricted environments, like muddy plains, marshes and ponds cut by meandering channels, probably in the central mixed-energy zone within an estuary. This interpretation is consistent with the habitat inferred for the recovered reptiles, as well as with associated foraminifers and with the probable origin of gastroliths found associate with the plesiosaurs.
The early Middle Jurassic is regarded as the period when sauropods diversified and be- came majo... more The early Middle Jurassic is regarded as the period when sauropods diversified and be- came major components of the terrestrial ecosystems. Not many sites yield sauropod mate- rial of this time; however, both cranial and postcranial material of eusauropods have been found in the Cañadón Asfalto Formation (latest Early Jurassic–early Middle Jurassic) in Central Patagonia (Argentina), which may help to shed light on the early evolution of eusauropods. These eusauropod remains include teeth associated with cranial and man- dibular material as well as isolated teeth found at different localities. In this study, an assem- blage of sauropod teeth from the Cañadón Asfalto Formation found in four different localities in the area of Cerro Condor (Chubut, Argentina) is used as a mean of assessing sauropod species diversity at these sites. By using dental enamel wrinkling, primarily based on the shape and orientation of grooves and crests of this wrinkling, we define and describe three different morphotypes. With the exception of one taxon, for which no cranial material is currently known, these morphotypes match the local eusauropod diversity as assessed based on postcranial material. Morphotype I is tentatively assigned to Patagosaurus, whereas morphotypes II and III correspond to new taxa, which are also distinguished by as- sociated postcranial material. This study thus shows that enamel wrinkling can be used as a tool in assessing sauropod diversity.
The theropod clade Carcharodontosauridae is a broadly distributed group of large allosauroid ther... more The theropod clade Carcharodontosauridae is a broadly distributed group of large allosauroid theropods. The
carcharodontosaurids recorded in the Albian – Cenomanian of Gondwana are the youngest and most derived members of this
clade. Tyrannotitan chubutensis, from the Cerro Castan˜ o Member of Cerro Barcino Formation (Albian; Chubut Group),
Central Patagonia, Argentina, is of prime interest among Gondwanan carcharodontosaurids as it represents the oldest record
of the group. Here we offer a detailed osteological comparative description of the holotype and paratype of Tyrannotitan
chubutensis together with a new diagnosis of the species. The new information results in a better understanding of this taxon
and Carcharodontosauridae. Furthermore, a comparative study of the anatomy of the pectoral girdle of Giganotosaurus is
reinterpreted as very similar to that of Tyrannotitan and Mapusaurus. We also present a phylogenetic analysis of
Carcharodontosauridae that recovers Tyrannotitan as a derived carcharodontosaurid, being the sister group of the clade
formed by Giganotosaurus and Mapusaurus, all nested in the clade Giganotosaurini
Ornithosuchidae is a group of Late Triassic pseudosuchian archosaurs of controversial phylogeneti... more Ornithosuchidae is a group of Late Triassic pseudosuchian archosaurs of controversial phylogenetic affinities. This clade currently comprises three taxa: Venaticosuchus rusconii and Riojasuchus tenuisceps, both from Argentina, and Ornithosuchus longidens, from Scotland. V. rusconii was erected on the basis of an incomplete skull with
articulated lower jaws and some elements of the postcranium that are currently lost. Venaticosuchus rusconii is redescribed here and included for the first time in a phylogenetic analysis to test its affinities with ornithosuchids. The bizarre morphology of V. rusconii has a unique combination of traits that distinguishes it from the other ornithosuchids, such as basipterygoid processes directed ventrally, dentary with the dorsal margin of the anterior end dorsally expanded, articular without a foramen on its medial side, and the absence of a surangular foramen, corroborating the validity of this taxon. V. rusconii is recovered as an ornithosuchid more closely related to R. tenuisceps than to O. longidens, based on the presence of a nearly pointed anterior margin of the antorbital fenestra, and a vertical bony strut of the jugal that separates the antorbital fenestra from the infratemporal fenestra
Methods improving the performance of molecular dating of divergence time of clades have improved ... more Methods improving the performance of molecular dating of divergence time of clades have improved dramatically in recent years.
The calibration of molecular dating using the first appearance of a clade in the fossil record is a crucial step towards inferring the
minimal diversification time of various groups and the choice of extinct taxa can strongly influence the molecular dates. Here, we
evaluate the uncertainty on the phylogenetic position of extinct taxa through non-parametric bootstrapping. The recognition of
phylogenetic uncertainty resulted in the definition of the Bootstrap Uncertainty Range (BUR) for the age of first appearance of a
given clade. The BUR is calculated as the interval of geological time in which the diversification of a given clade can be inferred to
have occurred, based on the temporal information of the fossil record and the topologies of the bootstrap trees. Divergence times
based on BUR analyses were calculated for three clades of turtles: Testudines, Pleurodira and Cryptodira. This resulted in extensive
uncertainty ranges of topology-dependent minimal divergence dates for these clades.
Annual Review of Earth and Planetary Sciences, May 2013
The idea that South America was an island continent over most of the Cenozoic, during which its u... more The idea that South America was an island continent over most of the Cenozoic, during which its unusual mammalian faunas evolved in isolation, is outstandingly influential in biogeography. Although large numbers of recent fossil discoveries and related advances require that it be significantly modified, the original isolation concept is still repeated in much current literature. The persistence of the idea inspired us to present here an integrated paleobiogeographic account of Jurassic to Paleogene mammals, reptiles, and plants from Patagonia, which has by far the richest fossil record on the continent. All three groups show distribution patterns that are broadly consistent with South America's long separation history, first from Laurasia by the Late Jurassic, then from Africa and India-Madagascar during the late Early Cretaceous, and finally from Antarctica and Australia during the early-middle Eocene, after which "isolation" finally commenced. We highlight areas of promising future research and provide ...
Entrevista a Federico Agnolin, Juan Canale, Marcelo Isasi, Leonardo Salgado y Diego Pol, más una ... more Entrevista a Federico Agnolin, Juan Canale, Marcelo Isasi, Leonardo Salgado y Diego Pol, más una nota de la autora sobre la historia de los dinosaurios procedentes de la Patagonia
Uploads
Papers by Diego Pol
the Upper Triassic−Lower Jurassic Elliot Formation of South Africa. It is represented by parts of the postcranial
skeleton of at least four individuals, including: cervical, dorsal, sacral and caudal vertebrae, most of the forelimb,
and part of the hindlimb. Sefapanosaurus bears several autapomorphies of the astragalus, and referred material
also shows autapomorphic features. The inclusion of Sefapanosaurus in a phylogenetic analysis places it within
the group of sauropodomorphs more closely related to sauropods than to Massospondylus (i.e. Sauropodiformes),
increasing the currently known diversity of the so-called ‘transitional forms’ leading to Sauropoda. Character optimization
revealed the presence of several features that are common for taxa placed within the transitional branches
basal to Sauropoda. Sefapanosaurus, together with other transitional sauropodomorphs reported during the last
decade, highlights the importance of Gondwanan taxa for understanding the palaeobiodiversity, global distribution,
and macroevolutionary changes in the group related to the rise of sauropods.
carcharodontosaurids recorded in the Albian – Cenomanian of Gondwana are the youngest and most derived members of this
clade. Tyrannotitan chubutensis, from the Cerro Castan˜ o Member of Cerro Barcino Formation (Albian; Chubut Group),
Central Patagonia, Argentina, is of prime interest among Gondwanan carcharodontosaurids as it represents the oldest record
of the group. Here we offer a detailed osteological comparative description of the holotype and paratype of Tyrannotitan
chubutensis together with a new diagnosis of the species. The new information results in a better understanding of this taxon
and Carcharodontosauridae. Furthermore, a comparative study of the anatomy of the pectoral girdle of Giganotosaurus is
reinterpreted as very similar to that of Tyrannotitan and Mapusaurus. We also present a phylogenetic analysis of
Carcharodontosauridae that recovers Tyrannotitan as a derived carcharodontosaurid, being the sister group of the clade
formed by Giganotosaurus and Mapusaurus, all nested in the clade Giganotosaurini
articulated lower jaws and some elements of the postcranium that are currently lost. Venaticosuchus rusconii is redescribed here and included for the first time in a phylogenetic analysis to test its affinities with ornithosuchids. The bizarre morphology of V. rusconii has a unique combination of traits that distinguishes it from the other ornithosuchids, such as basipterygoid processes directed ventrally, dentary with the dorsal margin of the anterior end dorsally expanded, articular without a foramen on its medial side, and the absence of a surangular foramen, corroborating the validity of this taxon. V. rusconii is recovered as an ornithosuchid more closely related to R. tenuisceps than to O. longidens, based on the presence of a nearly pointed anterior margin of the antorbital fenestra, and a vertical bony strut of the jugal that separates the antorbital fenestra from the infratemporal fenestra
The calibration of molecular dating using the first appearance of a clade in the fossil record is a crucial step towards inferring the
minimal diversification time of various groups and the choice of extinct taxa can strongly influence the molecular dates. Here, we
evaluate the uncertainty on the phylogenetic position of extinct taxa through non-parametric bootstrapping. The recognition of
phylogenetic uncertainty resulted in the definition of the Bootstrap Uncertainty Range (BUR) for the age of first appearance of a
given clade. The BUR is calculated as the interval of geological time in which the diversification of a given clade can be inferred to
have occurred, based on the temporal information of the fossil record and the topologies of the bootstrap trees. Divergence times
based on BUR analyses were calculated for three clades of turtles: Testudines, Pleurodira and Cryptodira. This resulted in extensive
uncertainty ranges of topology-dependent minimal divergence dates for these clades.
the Upper Triassic−Lower Jurassic Elliot Formation of South Africa. It is represented by parts of the postcranial
skeleton of at least four individuals, including: cervical, dorsal, sacral and caudal vertebrae, most of the forelimb,
and part of the hindlimb. Sefapanosaurus bears several autapomorphies of the astragalus, and referred material
also shows autapomorphic features. The inclusion of Sefapanosaurus in a phylogenetic analysis places it within
the group of sauropodomorphs more closely related to sauropods than to Massospondylus (i.e. Sauropodiformes),
increasing the currently known diversity of the so-called ‘transitional forms’ leading to Sauropoda. Character optimization
revealed the presence of several features that are common for taxa placed within the transitional branches
basal to Sauropoda. Sefapanosaurus, together with other transitional sauropodomorphs reported during the last
decade, highlights the importance of Gondwanan taxa for understanding the palaeobiodiversity, global distribution,
and macroevolutionary changes in the group related to the rise of sauropods.
carcharodontosaurids recorded in the Albian – Cenomanian of Gondwana are the youngest and most derived members of this
clade. Tyrannotitan chubutensis, from the Cerro Castan˜ o Member of Cerro Barcino Formation (Albian; Chubut Group),
Central Patagonia, Argentina, is of prime interest among Gondwanan carcharodontosaurids as it represents the oldest record
of the group. Here we offer a detailed osteological comparative description of the holotype and paratype of Tyrannotitan
chubutensis together with a new diagnosis of the species. The new information results in a better understanding of this taxon
and Carcharodontosauridae. Furthermore, a comparative study of the anatomy of the pectoral girdle of Giganotosaurus is
reinterpreted as very similar to that of Tyrannotitan and Mapusaurus. We also present a phylogenetic analysis of
Carcharodontosauridae that recovers Tyrannotitan as a derived carcharodontosaurid, being the sister group of the clade
formed by Giganotosaurus and Mapusaurus, all nested in the clade Giganotosaurini
articulated lower jaws and some elements of the postcranium that are currently lost. Venaticosuchus rusconii is redescribed here and included for the first time in a phylogenetic analysis to test its affinities with ornithosuchids. The bizarre morphology of V. rusconii has a unique combination of traits that distinguishes it from the other ornithosuchids, such as basipterygoid processes directed ventrally, dentary with the dorsal margin of the anterior end dorsally expanded, articular without a foramen on its medial side, and the absence of a surangular foramen, corroborating the validity of this taxon. V. rusconii is recovered as an ornithosuchid more closely related to R. tenuisceps than to O. longidens, based on the presence of a nearly pointed anterior margin of the antorbital fenestra, and a vertical bony strut of the jugal that separates the antorbital fenestra from the infratemporal fenestra
The calibration of molecular dating using the first appearance of a clade in the fossil record is a crucial step towards inferring the
minimal diversification time of various groups and the choice of extinct taxa can strongly influence the molecular dates. Here, we
evaluate the uncertainty on the phylogenetic position of extinct taxa through non-parametric bootstrapping. The recognition of
phylogenetic uncertainty resulted in the definition of the Bootstrap Uncertainty Range (BUR) for the age of first appearance of a
given clade. The BUR is calculated as the interval of geological time in which the diversification of a given clade can be inferred to
have occurred, based on the temporal information of the fossil record and the topologies of the bootstrap trees. Divergence times
based on BUR analyses were calculated for three clades of turtles: Testudines, Pleurodira and Cryptodira. This resulted in extensive
uncertainty ranges of topology-dependent minimal divergence dates for these clades.