The internal nasal skeleton in Monodelphis domestica, the gray short-tailed opossum, primarily su... more The internal nasal skeleton in Monodelphis domestica, the gray short-tailed opossum, primarily supports olfactory and respiratory epithelia, the vomeronasal organ, and the nasal gland. This scaffold is built by the median mesethmoid, and the paired vomer and ethmoid bones. The mesethmoid ossifies within the nasal septum cartilage. The bilateral ethmoid segregates respiratory and olfactory regions, and its geometry offers insight into the functional, developmental, and genomic organization of the nose. It forms through partial coalescence of separate elements known as turbinals, which in Monodelphis comprise the maxilloturbinal, nasoturbinal, five endoturbinals, and two ectoturbinals. Geometry of the ethmoid increases respiratory mucosal surface area by a factor of six and olfactory mucosal surface by nearly an order of magnitude. Respiratory epithelium warms and humidifies inspired air, recovers moisture as air is exhaled, and may help mediate brain temperature. In contrast, the olfactory skeleton functions as a series of small funnels that support growth of new olfactory neurons throughout life. Olfactory mucosa lines the mouth of each funnel, forming blind olfactory recesses known as the ethmoid cells, and neuronal axons are funneled from the epithelium through tiny olfactory foramina in the cribriform plate, into close proximity with target glomeruli in the olfactory bulb of the brain where each axon makes its first synapse. The skeleton may thus mediate topological correspondence between odorant receptor areas in the nose with particular glomeruli in the olfactory bulb, enabling growth throughout life of new olfactory neurons and proper targeting by their axons. The geometric arrangement of odorant receptors suggests that a measure of volatility may be a component in the peripheral olfactory code, and that corresponding glomeruli may function in temporal signal processing. Supporting visualizations for this study are available online at www.DigiMorph.org.
ABSTRACT-The Terlingua local fauna is a rich assemblage of predominantly terrestrial microvertebr... more ABSTRACT-The Terlingua local fauna is a rich assemblage of predominantly terrestrial microvertebrates from the Upper Cretaceous Aguja Formation ofTrans-Pecos Texas. Marine invertebrates (which include elements of both Cretaceous Western Interior and Gulf Coast zoogeographic provinces) from conformably underlying strata suggest that the fauna is of late Campanian age, probably correlative with Judithian assemblages of the Western Interior. A Judithian "age" for the fauna is further supported by its mammal and theropod assemblages, and by the faunas of overlying deposits. The previously reported diversity of the Aguja Formation, which we summarize, is significantly enriched by this new fauna. The fauna also fills a major gap in the biogeography of Campanian terrestrial vertebrates. Notable occurrences in the Terlingua local fauna include the therian mammal Gallolestes, previously known only from Baja California, and a hitherto unrecorded type of primitive 'tribothere.' At least 4 marsupial and 6 multituberculate taxa are present, several of which represent new taxa. Squamates comprise at least IO taxa, including xenosaurs, necrosaurs, glyptosaurines, scincids, teiids, and a snake, several of which represent new taxa. In addition, the fauna includes at least 7 dinosaurs, I pterosaur, 2 crocodylomorphs, 3 turtles, 3 lissamphibians, 3 actinopterygians, and 8 chondrichthyans. Wood, amber, leaves, seeds, pollen, molluscs, and dinoflagellates are also preserved. The fauna is not strictly comparable to others from the Western Interior. It includes taxa that are either endemic or otherwise known only from relatively low latitudes, indicating an appreciable degree oflatitudinal differentiation among Campanian terrestrial faunas bordering the Western Interior seaway.
Evidence from two early fossils suggests that brain enlargement and specialization proceeded in t... more Evidence from two early fossils suggests that brain enlargement and specialization proceeded in three pulses.
Calibrating human population dispersals across Earth’s surface is fundamental to assessing rates ... more Calibrating human population dispersals across Earth’s surface is fundamental to assessing rates and timing of anthropogenic impacts and distinguishing ecological phenomena influenced by humans from those that were not. Here, we describe the Hartley mammoth locality, which dates to 38,900–36,250 cal BP by AMS 14C analysis of hydroxyproline from bone collagen. We accept the standard view that elaborate stone technology of the Eurasian Upper Paleolithic was introduced into the Americas by arrival of the Native American clade ∼16,000 cal BP. It follows that if older cultural sites exist in the Americas, they might only be diagnosed using nuanced taphonomic approaches. We employed computed tomography (CT and μCT) and other state-of-the-art methods that had not previously been applied to investigating ancient American sites. This revealed multiple lines of taphonomic evidence suggesting that two mammoths were butchered using expedient lithic and bone technology, along with evidence diagn...
neopeptide in the thymus provides a new approach for exploring the role of peptide in the positiv... more neopeptide in the thymus provides a new approach for exploring the role of peptide in the positive selection of T cells. This strategy inverts the traditional one of starting with a T cell displaying a particular TCR and then attempting to define the requirements for its selection; rather, it begins with expression of a new peptide and permits one to study the T cells naturally selected on it. Our data show that the peptide sequence influences the sequence of the TCRs on selected cells, significant and systematic variations resulting from singleresidue changes at putative TCR-contact points. The relation between selecting peptide and selected TCR shows significant, but not complete, two-way degeneracy, analogous to what is seen with the responses of mature T cells. Taken together, these observations support the hypothesis that positive selection involves direct recognition of peptide features, but they do not entirely rule out the possibility that peptide plays primarily a structural role, its precise sequence impinging on the process when it leads to steric hindrance of the TCR (12).
CT visualization of the mandible and dentition of Hadrocodium wui, a stem mammaliaform from the L... more CT visualization of the mandible and dentition of Hadrocodium wui, a stem mammaliaform from the Lower Jurassic Lower Lufeng Formation of Yunnan, China has revealed new features not accessible by previous microscopic study of the fossil. Its mandible shows a postdentary trough with an overhanging medial ridge and a short Meckel's sulcus. An incomplete part of the ectotympanic and possibly a remnant of Meckel's element are preserved in the postdentary trough. Thus, Hadrocodium is similar to other mammaliaforms in retaining a mandibular middle ear, contrary to our earlier interpretation. The mandible exhibits a large postcanine diastema from shedding of anterior premolars without replacement, an age-dependent feature better developed in older adults. Another adult feature is the alignment of the ultimate molar to the coronoid process. This is consistent with age-dependent changes in other mammaliaforms where the last molars of the toothrow shift from medial of the coronoid process in the juvenile, to a position in front of the coronoid process in the adult. The mandible has a short mobile symphysis. The dentition consists of I5, C1 (two-rooted), P3 (including P1 position) and M2 (M2 with confluent roots), and i4, c1 (partially two-rooted), p3, and m2 (m2 with partially confluent roots). The two-rooted upper canines are more derived than other Early Jurassic mammaliaforms from the same fauna, although similar to docodontans. Hadrocodium is unique in that the lower m2 cusp a occludes in the embrasure between upper M1-M2, but the posterior part of m2 shows between-cusp occlusion with upper M2 main cusp A. M2 is half the size of the lower m2, and occludes only with the distal half of m2. The upper postcanines show a steep gradient of posteriorly decreasing tooth size, more so than other mammaliaforms. The CT examination corroborates that there are no unerupted teeth in the upper or lower jaws, and the holotype of H. wui is dentally and osteologically mature and capable of independent feeding.
Computed tomography X-ray imaging of the internal face in well-preserved primate fossil crania pe... more Computed tomography X-ray imaging of the internal face in well-preserved primate fossil crania permits reconstruction of the nature of their nasal anatomy, including some soft-tissue features. These features are diagnostic of the primate suborder Haplorhini, and allow reevaluation of the phylogenetic status of several purported early members of the group. Here we examine the nasolacrimal morphology of a broad sample of extant primates, as well as a number of Paleogene fossils. The extant sample confirms the distinctiveness of the two suborders. Of the fossils studied, only Shoshonius cooperi from the late-early Eocene exhibits evidence of a haplorhine nose. This suggests that the haplorhine oronasal complex may have evolved before the postorbital septum, and strengthens the claim that Shoshonius is a close relative of tarsiers and anthropoids. These results indicate that Omomyiformes is not a monophyletic group, and that few of its members possessed the derived oronasal morphology t...
Over the past two decades, the development of methods for visualizing and analysing specimens dig... more Over the past two decades, the development of methods for visualizing and analysing specimens digitally, in three and even four dimensions, has transformed the study of living and fossil organisms. However, the initial promise that the widespread application of such methods would facilitate access to the underlying digital data has not been fully achieved. The underlying datasets for many published studies are not readily or freely available, introducing a barrier to verification and reproducibility, and the reuse of data. There is no current agreement or policy on the amount and type of data that should be made available alongside studies that use, and in some cases are wholly reliant on, digital morphology. Here, we propose a set of recommendations for minimum standards and additional best practice for three-dimensional digital data publication, and review the issues around data storage, management and accessibility.
Highlights d Cretaceous-aged dome-headed dinosaurs are convergent with Triassic-aged Triopticus d... more Highlights d Cretaceous-aged dome-headed dinosaurs are convergent with Triassic-aged Triopticus d Archosauromorph reptiles evolved extreme body plans after the end-Permian extinction d Dinosaurs repeated body plans present in their Triassic-aged relatives d The early evolution of body plans may constrain later body plans in the same group
Early sarcopterygians were aquatic, but from the latter part of the Carboniferous onward
that gr... more Early sarcopterygians were aquatic, but from the latter part of the Carboniferous onward
that group has been dominated by terrestrial forms commonly known as the tetrapods.
Fig. 1 illustrates relationships among extant Tetrapoda [1-4]. As the cladograms
in Figs. 2-20 demonstrate, however, extant groups represent only a small part
of the taxonomic and morphologic diversity of Tetrapoda. We hope to convey some
appreciation for the broad outlines of tetrapod evolution during its 300+ million year
history from late Mississippian to Recent times. In doing so, we summarize trees derived
from the distribution of over 972 characters among 83 terminal taxa of Tetrapoda.
More than 90% of the terminal taxa we discuss are extinct, but all of the subterminal
taxa are represented in the extant biota. This enables us to emphasize the
origins of living tetrapod groups while giving due consideration to the diversity and
antiquity of the clades of which they are a part.
Our 3D Phyloinformatics project concerns distributed data integration, data provenance and morpho... more Our 3D Phyloinformatics project concerns distributed data integration, data provenance and morphological image data management. The larger context is the uniting of information standards across the NSF grand challenge to assemble the tree of life (AToL), NIH model organism efforts (e.g. ZFIN), and global biodiversity information efforts (GBIF, TDWG). Our targeted effort is the creation of a productivity tool for systematic biologists. The tool enables users to create, organize and annotate an image database of morphological characters and features. Resulting illustrated ontologies may
Dilophosaurus wetherilli was the largest animal known to have lived on land in North America duri... more Dilophosaurus wetherilli was the largest animal known to have lived on land in North America during the Early Jurassic. Despite its charismatic presence in pop culture and dinosaurian phylogenetic analyses, major aspects of the skeletal anatomy, taxonomy, ontogeny, and evolutionary relationships of this dinosaur remain unknown. Skeletons of this species were collected from the middle and lower part of the Kayenta Formation in the Navajo Nation in northern Arizona. Redescription of the holotype, referred, and previously undescribed specimens of Dilophosaurus wetherilli supports the existence of a single species of crested, large-bodied theropod in the Kayenta Formation. The parasagittal nasolacrimal crests are uniquely constructed by a small ridge on the nasal process of the premaxilla, dorsoventrally expanded nasal, and tall lacrimal that includes a posterior process behind the eye. The cervical vertebrae exhibit serial variation within the posterior centrodiapophyseal lamina, which...
The neocortex is characterized by lamination of its neuron cell bodies in six layers, but there a... more The neocortex is characterized by lamination of its neuron cell bodies in six layers, but there are few clues as to how this comes about and what is its function. Recent studies provide evidence that evolution from simple three-layer cortex may give insight into this problem. Three-layer cortex arose in the olfactory, hippocampal and dorsal cortex of the early amniote forebrain based on a cortical module of excitatory and inhibitory inputs to an intratelencephalic (IT) type of pyramidal neuron with feedback excitation and inhibition and related interneurons. We summarize recent evidence suggesting the hypothesis that the developmental program of three-layer olfactory cortex was co-opted to form six-layer mammalian neocortex, elaborating IT cortical units in layers 2-6 while adding layer 4 stellate cells, layer 5B pyramidal tract (PT) cells and layer 6 corticothalamic (CT) cells.
Highlights d Cretaceous-aged dome-headed dinosaurs are convergent with Triassic-aged Triopticus d... more Highlights d Cretaceous-aged dome-headed dinosaurs are convergent with Triassic-aged Triopticus d Archosauromorph reptiles evolved extreme body plans after the end-Permian extinction d Dinosaurs repeated body plans present in their Triassic-aged relatives d The early evolution of body plans may constrain later body plans in the same group
The internal nasal skeleton in Monodelphis domestica, the gray short-tailed opossum, primarily su... more The internal nasal skeleton in Monodelphis domestica, the gray short-tailed opossum, primarily supports olfactory and respiratory epithelia, the vomeronasal organ, and the nasal gland. This scaffold is built by the median mesethmoid, and the paired vomer and ethmoid bones. The mesethmoid ossifies within the nasal septum cartilage. The bilateral ethmoid segregates respiratory and olfactory regions, and its geometry offers insight into the functional, developmental, and genomic organization of the nose. It forms through partial coalescence of separate elements known as turbinals, which in Monodelphis comprise the maxilloturbinal, nasoturbinal, five endoturbinals, and two ectoturbinals. Geometry of the ethmoid increases respiratory mucosal surface area by a factor of six and olfactory mucosal surface by nearly an order of magnitude. Respiratory epithelium warms and humidifies inspired air, recovers moisture as air is exhaled, and may help mediate brain temperature. In contrast, the olfactory skeleton functions as a series of small funnels that support growth of new olfactory neurons throughout life. Olfactory mucosa lines the mouth of each funnel, forming blind olfactory recesses known as the ethmoid cells, and neuronal axons are funneled from the epithelium through tiny olfactory foramina in the cribriform plate, into close proximity with target glomeruli in the olfactory bulb of the brain where each axon makes its first synapse. The skeleton may thus mediate topological correspondence between odorant receptor areas in the nose with particular glomeruli in the olfactory bulb, enabling growth throughout life of new olfactory neurons and proper targeting by their axons. The geometric arrangement of odorant receptors suggests that a measure of volatility may be a component in the peripheral olfactory code, and that corresponding glomeruli may function in temporal signal processing. Supporting visualizations for this study are available online at www.DigiMorph.org.
ABSTRACT-The Terlingua local fauna is a rich assemblage of predominantly terrestrial microvertebr... more ABSTRACT-The Terlingua local fauna is a rich assemblage of predominantly terrestrial microvertebrates from the Upper Cretaceous Aguja Formation ofTrans-Pecos Texas. Marine invertebrates (which include elements of both Cretaceous Western Interior and Gulf Coast zoogeographic provinces) from conformably underlying strata suggest that the fauna is of late Campanian age, probably correlative with Judithian assemblages of the Western Interior. A Judithian "age" for the fauna is further supported by its mammal and theropod assemblages, and by the faunas of overlying deposits. The previously reported diversity of the Aguja Formation, which we summarize, is significantly enriched by this new fauna. The fauna also fills a major gap in the biogeography of Campanian terrestrial vertebrates. Notable occurrences in the Terlingua local fauna include the therian mammal Gallolestes, previously known only from Baja California, and a hitherto unrecorded type of primitive 'tribothere.' At least 4 marsupial and 6 multituberculate taxa are present, several of which represent new taxa. Squamates comprise at least IO taxa, including xenosaurs, necrosaurs, glyptosaurines, scincids, teiids, and a snake, several of which represent new taxa. In addition, the fauna includes at least 7 dinosaurs, I pterosaur, 2 crocodylomorphs, 3 turtles, 3 lissamphibians, 3 actinopterygians, and 8 chondrichthyans. Wood, amber, leaves, seeds, pollen, molluscs, and dinoflagellates are also preserved. The fauna is not strictly comparable to others from the Western Interior. It includes taxa that are either endemic or otherwise known only from relatively low latitudes, indicating an appreciable degree oflatitudinal differentiation among Campanian terrestrial faunas bordering the Western Interior seaway.
Evidence from two early fossils suggests that brain enlargement and specialization proceeded in t... more Evidence from two early fossils suggests that brain enlargement and specialization proceeded in three pulses.
Calibrating human population dispersals across Earth’s surface is fundamental to assessing rates ... more Calibrating human population dispersals across Earth’s surface is fundamental to assessing rates and timing of anthropogenic impacts and distinguishing ecological phenomena influenced by humans from those that were not. Here, we describe the Hartley mammoth locality, which dates to 38,900–36,250 cal BP by AMS 14C analysis of hydroxyproline from bone collagen. We accept the standard view that elaborate stone technology of the Eurasian Upper Paleolithic was introduced into the Americas by arrival of the Native American clade ∼16,000 cal BP. It follows that if older cultural sites exist in the Americas, they might only be diagnosed using nuanced taphonomic approaches. We employed computed tomography (CT and μCT) and other state-of-the-art methods that had not previously been applied to investigating ancient American sites. This revealed multiple lines of taphonomic evidence suggesting that two mammoths were butchered using expedient lithic and bone technology, along with evidence diagn...
neopeptide in the thymus provides a new approach for exploring the role of peptide in the positiv... more neopeptide in the thymus provides a new approach for exploring the role of peptide in the positive selection of T cells. This strategy inverts the traditional one of starting with a T cell displaying a particular TCR and then attempting to define the requirements for its selection; rather, it begins with expression of a new peptide and permits one to study the T cells naturally selected on it. Our data show that the peptide sequence influences the sequence of the TCRs on selected cells, significant and systematic variations resulting from singleresidue changes at putative TCR-contact points. The relation between selecting peptide and selected TCR shows significant, but not complete, two-way degeneracy, analogous to what is seen with the responses of mature T cells. Taken together, these observations support the hypothesis that positive selection involves direct recognition of peptide features, but they do not entirely rule out the possibility that peptide plays primarily a structural role, its precise sequence impinging on the process when it leads to steric hindrance of the TCR (12).
CT visualization of the mandible and dentition of Hadrocodium wui, a stem mammaliaform from the L... more CT visualization of the mandible and dentition of Hadrocodium wui, a stem mammaliaform from the Lower Jurassic Lower Lufeng Formation of Yunnan, China has revealed new features not accessible by previous microscopic study of the fossil. Its mandible shows a postdentary trough with an overhanging medial ridge and a short Meckel's sulcus. An incomplete part of the ectotympanic and possibly a remnant of Meckel's element are preserved in the postdentary trough. Thus, Hadrocodium is similar to other mammaliaforms in retaining a mandibular middle ear, contrary to our earlier interpretation. The mandible exhibits a large postcanine diastema from shedding of anterior premolars without replacement, an age-dependent feature better developed in older adults. Another adult feature is the alignment of the ultimate molar to the coronoid process. This is consistent with age-dependent changes in other mammaliaforms where the last molars of the toothrow shift from medial of the coronoid process in the juvenile, to a position in front of the coronoid process in the adult. The mandible has a short mobile symphysis. The dentition consists of I5, C1 (two-rooted), P3 (including P1 position) and M2 (M2 with confluent roots), and i4, c1 (partially two-rooted), p3, and m2 (m2 with partially confluent roots). The two-rooted upper canines are more derived than other Early Jurassic mammaliaforms from the same fauna, although similar to docodontans. Hadrocodium is unique in that the lower m2 cusp a occludes in the embrasure between upper M1-M2, but the posterior part of m2 shows between-cusp occlusion with upper M2 main cusp A. M2 is half the size of the lower m2, and occludes only with the distal half of m2. The upper postcanines show a steep gradient of posteriorly decreasing tooth size, more so than other mammaliaforms. The CT examination corroborates that there are no unerupted teeth in the upper or lower jaws, and the holotype of H. wui is dentally and osteologically mature and capable of independent feeding.
Computed tomography X-ray imaging of the internal face in well-preserved primate fossil crania pe... more Computed tomography X-ray imaging of the internal face in well-preserved primate fossil crania permits reconstruction of the nature of their nasal anatomy, including some soft-tissue features. These features are diagnostic of the primate suborder Haplorhini, and allow reevaluation of the phylogenetic status of several purported early members of the group. Here we examine the nasolacrimal morphology of a broad sample of extant primates, as well as a number of Paleogene fossils. The extant sample confirms the distinctiveness of the two suborders. Of the fossils studied, only Shoshonius cooperi from the late-early Eocene exhibits evidence of a haplorhine nose. This suggests that the haplorhine oronasal complex may have evolved before the postorbital septum, and strengthens the claim that Shoshonius is a close relative of tarsiers and anthropoids. These results indicate that Omomyiformes is not a monophyletic group, and that few of its members possessed the derived oronasal morphology t...
Over the past two decades, the development of methods for visualizing and analysing specimens dig... more Over the past two decades, the development of methods for visualizing and analysing specimens digitally, in three and even four dimensions, has transformed the study of living and fossil organisms. However, the initial promise that the widespread application of such methods would facilitate access to the underlying digital data has not been fully achieved. The underlying datasets for many published studies are not readily or freely available, introducing a barrier to verification and reproducibility, and the reuse of data. There is no current agreement or policy on the amount and type of data that should be made available alongside studies that use, and in some cases are wholly reliant on, digital morphology. Here, we propose a set of recommendations for minimum standards and additional best practice for three-dimensional digital data publication, and review the issues around data storage, management and accessibility.
Highlights d Cretaceous-aged dome-headed dinosaurs are convergent with Triassic-aged Triopticus d... more Highlights d Cretaceous-aged dome-headed dinosaurs are convergent with Triassic-aged Triopticus d Archosauromorph reptiles evolved extreme body plans after the end-Permian extinction d Dinosaurs repeated body plans present in their Triassic-aged relatives d The early evolution of body plans may constrain later body plans in the same group
Early sarcopterygians were aquatic, but from the latter part of the Carboniferous onward
that gr... more Early sarcopterygians were aquatic, but from the latter part of the Carboniferous onward
that group has been dominated by terrestrial forms commonly known as the tetrapods.
Fig. 1 illustrates relationships among extant Tetrapoda [1-4]. As the cladograms
in Figs. 2-20 demonstrate, however, extant groups represent only a small part
of the taxonomic and morphologic diversity of Tetrapoda. We hope to convey some
appreciation for the broad outlines of tetrapod evolution during its 300+ million year
history from late Mississippian to Recent times. In doing so, we summarize trees derived
from the distribution of over 972 characters among 83 terminal taxa of Tetrapoda.
More than 90% of the terminal taxa we discuss are extinct, but all of the subterminal
taxa are represented in the extant biota. This enables us to emphasize the
origins of living tetrapod groups while giving due consideration to the diversity and
antiquity of the clades of which they are a part.
Our 3D Phyloinformatics project concerns distributed data integration, data provenance and morpho... more Our 3D Phyloinformatics project concerns distributed data integration, data provenance and morphological image data management. The larger context is the uniting of information standards across the NSF grand challenge to assemble the tree of life (AToL), NIH model organism efforts (e.g. ZFIN), and global biodiversity information efforts (GBIF, TDWG). Our targeted effort is the creation of a productivity tool for systematic biologists. The tool enables users to create, organize and annotate an image database of morphological characters and features. Resulting illustrated ontologies may
Dilophosaurus wetherilli was the largest animal known to have lived on land in North America duri... more Dilophosaurus wetherilli was the largest animal known to have lived on land in North America during the Early Jurassic. Despite its charismatic presence in pop culture and dinosaurian phylogenetic analyses, major aspects of the skeletal anatomy, taxonomy, ontogeny, and evolutionary relationships of this dinosaur remain unknown. Skeletons of this species were collected from the middle and lower part of the Kayenta Formation in the Navajo Nation in northern Arizona. Redescription of the holotype, referred, and previously undescribed specimens of Dilophosaurus wetherilli supports the existence of a single species of crested, large-bodied theropod in the Kayenta Formation. The parasagittal nasolacrimal crests are uniquely constructed by a small ridge on the nasal process of the premaxilla, dorsoventrally expanded nasal, and tall lacrimal that includes a posterior process behind the eye. The cervical vertebrae exhibit serial variation within the posterior centrodiapophyseal lamina, which...
The neocortex is characterized by lamination of its neuron cell bodies in six layers, but there a... more The neocortex is characterized by lamination of its neuron cell bodies in six layers, but there are few clues as to how this comes about and what is its function. Recent studies provide evidence that evolution from simple three-layer cortex may give insight into this problem. Three-layer cortex arose in the olfactory, hippocampal and dorsal cortex of the early amniote forebrain based on a cortical module of excitatory and inhibitory inputs to an intratelencephalic (IT) type of pyramidal neuron with feedback excitation and inhibition and related interneurons. We summarize recent evidence suggesting the hypothesis that the developmental program of three-layer olfactory cortex was co-opted to form six-layer mammalian neocortex, elaborating IT cortical units in layers 2-6 while adding layer 4 stellate cells, layer 5B pyramidal tract (PT) cells and layer 6 corticothalamic (CT) cells.
Highlights d Cretaceous-aged dome-headed dinosaurs are convergent with Triassic-aged Triopticus d... more Highlights d Cretaceous-aged dome-headed dinosaurs are convergent with Triassic-aged Triopticus d Archosauromorph reptiles evolved extreme body plans after the end-Permian extinction d Dinosaurs repeated body plans present in their Triassic-aged relatives d The early evolution of body plans may constrain later body plans in the same group
Uploads
Papers by Timothy Rowe
that group has been dominated by terrestrial forms commonly known as the tetrapods.
Fig. 1 illustrates relationships among extant Tetrapoda [1-4]. As the cladograms
in Figs. 2-20 demonstrate, however, extant groups represent only a small part
of the taxonomic and morphologic diversity of Tetrapoda. We hope to convey some
appreciation for the broad outlines of tetrapod evolution during its 300+ million year
history from late Mississippian to Recent times. In doing so, we summarize trees derived
from the distribution of over 972 characters among 83 terminal taxa of Tetrapoda.
More than 90% of the terminal taxa we discuss are extinct, but all of the subterminal
taxa are represented in the extant biota. This enables us to emphasize the
origins of living tetrapod groups while giving due consideration to the diversity and
antiquity of the clades of which they are a part.
that group has been dominated by terrestrial forms commonly known as the tetrapods.
Fig. 1 illustrates relationships among extant Tetrapoda [1-4]. As the cladograms
in Figs. 2-20 demonstrate, however, extant groups represent only a small part
of the taxonomic and morphologic diversity of Tetrapoda. We hope to convey some
appreciation for the broad outlines of tetrapod evolution during its 300+ million year
history from late Mississippian to Recent times. In doing so, we summarize trees derived
from the distribution of over 972 characters among 83 terminal taxa of Tetrapoda.
More than 90% of the terminal taxa we discuss are extinct, but all of the subterminal
taxa are represented in the extant biota. This enables us to emphasize the
origins of living tetrapod groups while giving due consideration to the diversity and
antiquity of the clades of which they are a part.