Timothy B. Rowe

University of Texas at Austin | UT · Department of Geological Sciences

Thrinaxodon – Digital Atlas of the Skull, is the first work to exploit the extraordinary power of the emergent digital technology of high-resolution X-ray computed tomographic (CT and µCT) scanning. for interpreting fossils. This CD-ROM presents a complete digital analysis of the skull, some 767 individual slices of the skull, that reveals minute a...

Living birds (Aves) have bodies substantially modified from the ancestral reptilian condition. The avian pelvis in particular experienced major changes during the transition from early archosaurs to living birds1,2. This stepwise transformation is well documented by an excellent fossil record2–4; however, the ontogenetic alterations that underly it...

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 bon...

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 incom...

The armoured dinosaurs, Thyreophora, were a diverse clade of ornithischians known from the Early Jurassic to the end of the Cretaceous. During the Middle and Late Jurassic, the thyreophorans radiated to evolve large body size, quadrupedality, and complex chewing mechanisms, and members of the group include some of the most iconic dinosaurs, includi...

As computed tomography and related technologies have become mainstream tools across a broad range of scientific applications, each new generation of instrumentation produces larger volumes of more-complex 3D data. Lagging behind are step-wise improvements in computational methods to rapidly analyze these new large, complex datasets. Here we describ...

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 sp...

This is a definition and discussion of the clade Pan-Biota.

Here we define and discuss the clade Biota.

We describe X-ray computed tomography (CT) datasets from three specimens recovered from Early Cretaceous lakebeds of China that illustrate the forensic interpretation of CT imagery for paleontology. Fossil vertebrates from thinly bedded sediments often shatter upon discovery and are commonly repaired as amalgamated mosaics grouted to a solid backin...

Fossils of mammals and their extinct relatives among cynodonts give evidence of correlated transformations affecting olfaction as well as mastication, head movement, and ventilation, and suggest evolutionary coupling of these seemingly separate anatomical regions into a larger integrated system of ortho-retronasal olfaction. Evidence from paleontol...

The Glen Canyon Group spans a period of Earth history that records the Triassic-Jurassic boundary and a biotic response to the end-Triassic mass extinction. Owing to the absence of dateable ash beds or useful biostratigraphic invertebrate fossils, the Early Jurassic has been poorly constrained in western North American and its chronology has been c...

Rooneyia viejaensis is a North American Eocene primate of uncertain phylogenetic affinities. Although the external cranial anatomy of Rooneyia is well studied, various authors have suggested that Rooneyia is a stem haplorhine, stem strepsirrhine, stem tarsiiform, or stem anthropoid. Here we describe the internal cranial anatomy of the Rooneyia holo...

The 'canonical model' of semicircular canal orientation in mammals assumes that 1) the three ipsilateral canals of an inner ear exist in orthogonal planes (i.e., orthogonality), 2) corresponding left and right canal pairs have equivalent angles (i.e., angle symmetry), and 3) contralateral synergistic canals occupy parallel planes (i.e., coplanarity...

ABSTRACT The late Campanian?aged (= Judithian) squamates from the Terlingua Local Fauna of the Aguja Formation, southern Texas, includes four scincomorphans: a new taxon (Catactegenys solaster, gen. et sp. nov.), referable to Xantusiidae, that has massive teeth and tooth crown morphology similar to that of contogeniid lizards; an indeterminate scin...

Features that were once considered exclusive to modern birds, such as feathers and a furcula, are now known to have first appeared in non-avian dinosaurs. However, relatively little is known of the early evolutionary history of the hyperinflated brain that distinguishes birds from other living reptiles and provides the important neurological capabl...

significantly in the last decade, and has augmented or even supplanted conventional mechanical preparation techniques in vertebrate paleontology laboratories. CT is dependent upon X-ray contrast between matrix and fossil material, and allows paleontologists to study otherwise unobservable morphological features in specimens. The articulated left fo...

The late Campanian-aged squamates from the Terlingua local fauna of the Aguja Formation of southern Texas are represented by numerous isolated specimens of fragmentary jaws, vertebrae, and osteoderms. The fauna includes four scincomorphans: a new taxon referable to Xantusiidae that has massive teeth with crown morphology similar to that of more del...

Within the nasal cavity of mammals is a complex scaffold of paper-thin bones that function in respiration and olfaction. Known as turbinals, the bones greatly enlarge the surface area available for conditioning inspired air, reducing water loss, and improving olfaction. Given their functional significance, the relative development of turbinal bones...

Several new specimens of the Triassic therocephalian Tetracynodon darti have become available in recent years, allowing substantial corrections and expansions to previous descriptions. We here analyze T. darti in the context of therocephalian relationships and biology, using computed tomographic (CT) scanning to reveal details of the skull. Histolo...

The interplay of evolution and development has been at the heart of evolutionary theory for more than a century. Heterochrony—change in the timing or rate of developmental events—has been implicated in the evolution of major vertebrate lineages such as mammals, including humans. Birds are the most speciose land vertebrates, with more than 10,000 li...

Many hypotheses have been postulated regarding the early evolution of the mammalian brain. Here, x-ray tomography of the Early Jurassic mammaliaforms Morganucodon and Hadrocodium sheds light on this history. We found that relative brain size expanded to mammalian levels, with enlarged olfactory bulbs, neocortex, olfactory (pyriform) cortex, and cer...

Sauropodomorph dinosaurs originated in the Southern Hemisphere in the Middle or Late Triassic and are commonly portrayed as spreading rapidly to all corners of Pangaea as part of a uniform Late Triassic to Early Jurassic cosmopolitan dinosaur fauna. Under this model, dispersal allegedly inhibited dinosaurian diversification, while vicariance and lo...

To analyze an abnormal gait pattern in mutant mice (Hugger), we conducted coarse-grained motion capture. Using a simple retroreflective marker-based approach, we could detect high-resolution mutant-specific gait patterns. The phenotypic gait patterns are caused by extreme vertical motion of limbs, revealing inefficient motor functions. To elucidate...

The recent discovery of early dinosauromorphs from North America demonstrates that they were con-temporaries with dinosaurs and other basal archosaurs during a substantial portion of the Late Triassic Period. Hindlimb material (femora, tibiae, a fibula, astragalocalcanea, and phalanges) of Dromomeron romeri, a non-dinosauriform dino-sauromorph from...

We report the occurrence of a furcula (fused clavicles) in both species of the Early Jurassic coelophysid theropod dinosaur Syntarsus (Coelophysidae sensu Holtz, 1994; Coelo-physis and Syntarsus and all descendants of their most recent common ancestor). The furcula is a median pectoral element formed by ontogenetic fusion of the left and right clav...

Fossils of the Early Cretaceous dinosaur, Nigersaurus taqueti, document for the first time the cranial anatomy of a rebbachisaurid sauropod. Its extreme adaptations for herbivory at ground-level challenge current hypotheses regarding feeding function and feeding strategy among diplodocoids, the larger clade of sauropods that includes Nigersaurus. W...

Acrocanthosaurus atokensis, a large carcharodontosaurid theropod, is known from several specimens collected in the 1990s, as well as the two original specimens collected in the 1940s. The holotype, OMNH 10146, contains a well-preserved and complete braincase that was scanned at the High Resolution X-ray Computed Tomography (CT) Facility at The Univ...

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 meseth-moid ossifies within the nasal septum cartilage. The bilateral et...

This panel brings together researchers and practitioners to describe and discuss current research efforts in 3D imaging technologies. Each panelist will provide a brief summary of current research activities followed by a discussion of how these activities fit into the panorama of building information communities.

Ceratosauria represents the first widespread and diverse radiation of theropod dinosaurs comprising two main sister clades, Neoceratosauria and Coelophysoidea. This chapter discusses the diagnostic features, phylogenetic placement, and paleobiology of ceratosaurians. The fossil record for Ceratosauria spans a minimum of 155 million years, from the...

The respiratory turbinates of mammals are complex bony plates within the nasal chamber that are covered with moist epithelium and provide an extensive surface area for the exchange of heat and water. Given their functional importance, maxilloturbinate size and structure are expected to vary predictably among species adapted to different environment...

Archaeopteryx, the earliest known flying bird (avialan) from the Late Jurassic period, exhibits many shared primitive characters with more basal coelurosaurian dinosaurs (the clade including all theropods more bird-like than Allosaurus), such as teeth, a long bony tail and pinnate feathers. However, Archaeopteryx possessed asymmetrical flight feath...

The horn sharks (Heterodontidae: Chondrichthyes) represent one of four independent evolutions of durophagy in the cartilaginous fishes. We used high-resolution computed tomography (CT scanning) to visualize and quantify the mineralized tissue of an ontogenetic series of horn sharks. CT scanning of neonatal through adult California horn sharks (Hete...

CT imaging was undertaken on the skull of 20-Myr-old Miocene Tremacebus har-ringtoni. Here we report our observations on the relative size of the olfactory fossa and its implications for the behavior of Tremacebus. The endocranial surface of Tremacebus is incomplete, making precise estimate of brain size and olfactory fossa size imprecise. However...

Comparison of birds and pterosaurs, the two archosaurian flyers, sheds light on adaptation to an aerial lifestyle. The neurological basis of control holds particular interest in that flight demands on sensory integration, equilibrium, and muscular coordination are acute. Here we compare the brain and vestibular apparatus in two pterosaurs based on...

High-resolution computed tomography provides an alternative to serial sectioning and other destructive techniques of studying fossils (data available at http://www.DigiMorph.org). This technology was used to study the oldest aistopod Lethiscus stocki. The fossil is found to have approximately 30 closely spaced teeth on its maxilla and dentary, a sh...

We present a novel point-based rendering approach based on object-space point interpolation. We introduce the concept of a transformation-invariant covariance matrix of a set of points to efficiently determine splat sizes in a multiresolution hierarchy. ...

High-resolution X-ray computed tomography (HRCT) is a non-invasive approach to 3D visualization and quantification of biological structure. The data, based on differential X-ray attenuation, are analogous to those otherwise obtainable only by serial sectioning. Requiring no fixing, sectioning or staining, HRCT produces a 3D digital map of the speci...

High-resolution and ultra-high-resolution X-ray computed tomography are rapid, non-destructive and extremely powerful techniques for three-dimensional examination and measurement of a great variety of geological materials and specimens with sizes from several millimetres to several decimetres. A review of recent applications in petrology, meteoriti...

An NSF-sponsored (EAR-IF) shared multi-user facility dedicated to research applications of high-resolution X-ray computed tomography (CT) in the geological sciences has been in operation since 1997 at the University of Texas at Austin. The centerpiece of the facility is an industrial CT scanner custom-designed for geological applications. Because t...

High-resolution X-ray computed tomography (CT) generates three-dimensional imagery of solid objects depicting X-ray attenuation, which is a function of density and atomic number. It is thus ideal for studying many features and quantities that are best observed, understood, and characterized in 3D, in objects from millimeter to decimeter scale. The...

We describe a new fossil crocodyliform archosaur from the Early Jurassic Kayenta Formation of the Navajo Nation that is surprisingly derived for so ancient a specimen. High-resolution X-ray CT analysis reveals that its long snout houses an extensive system of pneumatic paranasal cavities. These are among the most distinctive features of modern croc...

The Archaeoraptor fossil was announced as a 'missing link' and purported to be possibly the best evidence since Archaeopteryx that birds did, in fact, evolve from certain types of carnivorous dinosaur. It reportedly came from Early Cretaceous beds of China that have produced other spectacular fossils transitional between birds and extinct non-avian...

Comparative anatomists since the time of Richard Owen ([1][1]) have observed that birds and crocodilians have a four-chambered heart and have speculated that such a heart was present in extinct archosaurs as well. Until recently, no direct evidence of the cardiovascular system had been reported in

Early Cretaceous terrestrial vertebrates are poorly known on a worldwide basis (e.g., Clemens et al., 1979; Weishampel, 1990). Of the few units in North America that have yielded them, only those in the West - the Cloverly Formation of Montana and Wyoming (Jenkins and Crompton, 1979; Jenkins and Schaff, 1988; Cifelli et al., 1998) and the Trinity G...

An exceptionally complete skeleton, dating back roughly 140-150 million years, offers our closest look yet at the last common ancestor of modern mammals.

Phylogenetic analysis with x-ray computed tomography of fossilized and recent crania implicates differential growth of the neocortex in the evolution and development of the mammalian middle ear. In premammalian tetrapods, the middle ear evolved as a chain of bones attached to the mandible and cranium, but in adult mammals the chain is detached from...

EXTANT marsupials are distinctive in their pattern of dental development1, in that only one tooth is replaced postnatally in each jaw. Interpretation of this pattern for marsupials ancestrally is disputed2-5, partly because ontogenetic data in fossils have been unobtainable. Here we present an ultra-high-resolution X-ray computed tomography (CT) st...

The recent discovery of a nearly complete ceratopsid skull in the Aguja Formation of southwest Texas supports previous conclusions that the Aguja ceratopsid represents a distinct species, Chasmosaurus mariscalensis. The diagnostic features of C. mariscalensis include an extensive anteromedian projection of the nasal between the premaxillae, erect s...

The Terlingua local fauna is a rich assemblage of predominantly terrestrial micro vertebrates from the Upper Cretaceous Aguja Formation of Trans-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 Ca...

Until now, Syntarsus was based on a single species, S. rhodesiensis, known only from southern Africa. The discovery of Syntarsus in North America adds significantly to the increasingly detailed resemblance of African and North American Early Jurassic terrestrial vertebrate faunas. The new species, Syntarsus kayentakatae, is based on a complete skul...

Mammalia is defined by its ancestry as the taxon originating with the most recent common ancestor of extant Monotremata and Theria. To diagnose Mammalia as so defined, 176 character transformations in the skull and postcranial skeleton, distributed among Placentalia, Marsupialia, Multituberculata, Monotremata, Morganucodontidae, Tritylodontidae, an...

— Several prominent cladists have questioned the importance of fossils in phylogenctic inference, and it is becoming increasingly popular to simply fit extinct forms, if they are considered at all, to a cladogram of Recent taxa. Gardiner's (1982) and Løvtrup's (1985) study of amniote phylogeny exemplifies this differential treatment, and we focused...

Several prominent cladists have questioned the importance of fossils in phylogenetic inference, and it is becoming increasingly popular to simply fit extinct forms, if they are considered at all, to a cladogram of Recent data. Gardiner's (1982) and Lovtrup's (1985) study of amniote phylogeny exemplifies this differential treatment, and we focused o...

Data from adult birds, crocodilians, Sphenodon, squamates, turtles, and from the chick embryo are compared to test conflicting hypotheses of homology of the deep dorsal thigh muscles of birds and other reptiles. This comparison suggests that: (1) avian Mm. iliofemoralis externus and iliotrochantericus caudalis (herein renamed “iliofemoralis cranial...

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