About

I study how the extinct can inform the extant and how the extant can inform the extinct

Research topics

• Biology
• Evolutionary biology
• Anatomy
• Ecology
• Zoology
• Neuroscience
• Demography
• Genetics
• Paleontology

Selected publications

• New data on the Triassic temnospondyls from the Karoo rift basins of Tanzania and Zambia

  The Catalogue of Life · 2026-02-16

  datasetOpen access
  PublisherDOI

• Braincase anatomy and palaeoneurology of <i>Venetoraptor gassenae</i> , a lagerpetid pterosauromorph from the Late Triassic of southern Brazil

  Palaeontology · 2026-03-01

  articleOpen access

  Abstract There is a growing consensus that pterosaurs and the flightless Lagerpetidae are closely related. This relationship is supported by apomorphies throughout the skeleton, including endocranial character states such as a well‐developed floccular fossa and a tall anterior semicircular canal. Our knowledge of lagerpetid anatomy has been improved by recent discoveries. Among them, the Brazilian record plays a significant role, having produced two described species, Ixalerpeton polesinensis and Venetoraptor gassenae , and several more fragmentary specimens. In this study, we used an x‐ray micro‐computed tomographic scan to describe the endocranial anatomy of the holotype of Venetoraptor gassenae . The endocranial anatomy of Venetoraptor gassenae is similar in shape to that of other described lagerpetids, and we reach the following conclusions: (1) in pterosaurs, the metotic foramen exits posteriorly, whereas in lagerpetids and dinosauromorphs it exits through the lateral wall of the braincase; and (2) Venetoraptor gassenae is unique among lagerpetids in having only one exit for cranial nerve XII, expanding its differential diagnosis. These differences highlight that the braincase anatomy of lagerpetids is aligned with the anatomical disparity observed in the group. Finally, we discuss why future studies should focus on comprehending patterns of braincase pneumaticity in avemetatarsalians.

  PublisherDOI

• A new taxon of saurischian dinosaur from the <i>Coelophysis</i> Quarry of New Mexico, <scp>USA</scp> (Triassic: latest Norian or Rhaetian) highlights herrerasaurian diversity in the latest Triassic

  Papers in Palaeontology · 2026-03-01

  articleSenior author

  Abstract The most complete record of the earliest dinosaur lineages is from the Carnian from the higher latitudes of Pangea (e.g. present‐day Brazil, Argentina), but dinosaurian assemblages from the upper stages of the Upper Triassic are better known from the low latitudes of Pangea (present day southwestern USA). How early carnivorous dinosaurian diversity matches or mismatches at various latitudes remains to be documented because of uncertainty around the spatio‐temporal ranges and phylogenetic relationships of early dinosaur lineages. We examine low‐latitude diversity patterns through the lens of the saurischian dinosaur Tawa hallae and close relatives, including a new species, Ptychotherates bucculentus gen. et sp. nov. The new taxon is known from an incomplete but well‐preserved skull (CM 31368) from the uppermost Triassic Coelophysis Quarry in northern New Mexico. The new taxon clearly shares synapomorphies with Tawa hallae , such as distinctive fossae on the quadrate and otoccipital and a dorsoventrally tall and laterally flat jugal. However, the new taxon is distinguishable from all other coeval ornithodirans by a combination of many character states, including the proportionally dorsoventrally deepest jugal known for any Triassic‐aged dinosaur. Higher‐palaeolatitude ecosystems across Pangea show a complete turnover of carnivorous dinosaurs by neotheropods in the Norian and Rhaetian, but the ‘ Chindesaurus – Tawa ’ clade (Morphoraptora clade nov.) coexisted with neotheropods possibly until the End‐Triassic Extinction Event. This suggests a low‐latitude ‘museum’ where early‐diverging lineages survived much longer than at higher latitudes, and that the End‐Triassic Extinction Event affected dinosaur diversity more than previously hypothesized.

  PublisherDOI

• Comparative histological analysis of vertebrates reveals Triassic climate variability across southern Pangea

  Journal of Anatomy · 2026-04-29

  article

  Climate highly influenced the distribution of major animal groups that emerged during the Triassic throughout the supercontinent Pangea. The earliest dinosaurs and associated assemblages (Carnian Stage, Late Triassic, ~230 Ma) are recovered along a paleolatitudinal climate belt spanning southern Pangea. However, developmental responses of different amniotic clades to climate across these environments remain unknown. Characterizing developmental variability, presumably driven in part by climatic variability within this belt, helps constrain the climatic ranges that shaped the earliest dinosaurs prior to their worldwide dispersal, while also providing insights into developmental plasticity of Triassic fauna. We analyzed the bone histology of five vertebrate taxa from the Carnian of Zimbabwe, including sauropodomorph and herrerasaurid dinosaurs, a gomphodontosuchine cynodont, a hyperodapedontine rhynchosaur, and a suchian archosaur (?aetosaur) as a proxy to assess probable climatic influence by comparing various growth strategies/metabolisms of these clades across southern Pangea. The dinosaurs are continuously growing individuals that exhibit well-vascularized woven-parallel and parallel-fibered cortical bone with no apparent growth marks. The cynodont is an immature specimen with a well-vascularized fibrolamellar matrix that has anastomosing vascular canals throughout the cortex and a single growth mark, indicating rapid growth. The rhynchosaurian femur and suchian tibia show moderate to poorly vascularized parallel-fibered and woven-fibered matrixes possessing multiple lines of arrested growth along with an external fundamental system, suggesting these were slow-growing individuals that had reached skeletal maturity at the time of death. Comparing this histology to that of similar assemblages from current-day Brazil, Argentina, and India (which fell along the same paleolatitudinal zone during the Triassic), the mid-continent (i.e., Zimbabwean) dinosaurs exhibit continuous uninterrupted growth in contrast to other histologically sampled dinosaurs from different localities along this climatic belt, whereas the Zimbabwean rhynchosaur and suchian exhibit patterns with more frequent cessation of growth than their South American counterparts. Slower-growing Zimbabwean taxa-presumably, more susceptible to climatic stressors-exhibit characteristics suggestive of a less resource-rich environment (e.g., frequent cessations, more interrupted growth) compared with rhynchosaurs and aetosaurs from South America. Taxa with faster growth rates and higher metabolic regimes (i.e., dinosaurs, cynodont) from this same assemblage apparently grew rapidly-and roughly continuously-throughout the year. This is consistent with an overall more arid but less seasonal climate in Zimbabwe compared to the signals recovered in Brazil, Argentina, and India.

  PublisherDOI

• Author response for "Rethinking thecodonty: the influence of two centuries of comparative dental anatomy on our understanding of tooth evolution"

  2025-08-02

  peer-review
  PublisherDOI

• Silesaurid ( <scp>Archosauria: Dinosauriformes</scp> ) remains from the base of the <scp>Dockum Group</scp> ( <scp>Late Triassic: Otischalkian</scp> ) of Texas provide new insights to the <scp>North American</scp> record of dinosauriforms

  The Anatomical Record · 2025-05-07 · 1 citations

  articleOpen accessSenior author

  Silesaurids (Archosauria: Dinosauriformes) are found in Middle to Upper Triassic deposits across Pangea, but few stratigraphic sections record the evolution of the group in one geographic area over millions of years. Here, we describe silesaurid remains from the oldest of the Upper Triassic stratigraphic sequence from the base of the Dockum Group, from the type locality of the Otischalkian faunachronozone. Isolated limb bones diagnostic of silesaurids include humeri, femora, and tibiae of a seemingly unique Silesaurus-like taxon from the same locality (Otis Chalk Quarry 3). The femora consist of four specimens of different lengths that sample the variation of character states associated with ontogeny, also sampled previously in both silesaurids (e.g., Asilisaurus kongwe and Silesaurus opolensis) and within neotheropods within Dinosauria (e.g., Coelophysis bauri). Our observations of the variation in the silesaurid sample further reinforce the interpretation of high variation of morphological features common in dinosauriforms. Furthermore, we show that overpreparation of bone surfaces has hidden some of this variation in previous interpretations. The tibia growth series shows that the fibular crest of the tibia develops during ontogeny, yet another phylogenetically informative character for dinosaurs and their kin that is at least ontogenetically variable in silesaurids. The presence of silesaurids at the base of the Dockum Group (late Carnian or early Norian) conclusively shows that the group was present near the onset of deposition of Upper Triassic rocks and survived for millions of years in the same geographic area at low latitudes throughout the Late Triassic.

  PublisherOA PDFDOI

• New specimens of <i>Eucoelophysis baldwini</i> from the Upper Triassic Chinle Formation, northern New Mexico, U.S.A., and their implications for the evolution of Silesauridae (Dinosauriformes)

  Journal of Vertebrate Paleontology · 2025-09-01

  article

  <i>Eucoelophysis baldwini</i> is a silesaurid dinosauriform known only from a single fragmentary postcranial skeleton from the Petrified Forest Member of the Upper Triassic Chinle Formation near Ghost Ranch in northern New Mexico, U.S.A. The relative incompleteness of that specimen has hampered the ability to diagnose <i>Eucoelophysis baldwini</i> and determine its phylogenetic relationships. However, abundant dinosauriform material has been recovered at the nearby Hayden Quarry from a similar stratigraphic level to the holotype. Our examination of all available specimens indicates that the holotype and the Hayden Quarry pelvic and hindlimb materials share a unique combination of character states which distinguish them from all other avemetatarsalians, including a reduction in the size of the fourth trochanter of the femur and a flat surface along the lateral margin of the tibia. Although the isolated Hayden Quarry cranial material cannot be directly compared with the holotype of <i>Eucoelophysis baldwini</i>, it does possess silesaurid synapomorphies (e.g., leaf-shaped teeth with delayed ankylosis, or fusion to the jaw) and there is no evidence to suggest more than one silesaurid taxon in the Hayden Quarry. Taken together, these data support the referral of the Hayden Quarry material to <i>Eucoelophysis baldwini</i>. The results of our study indicate that the diversification of most Late Triassic silesaurid lineages occurred by the Carnian Stage, approximately coincident with the initial radiation of saurischian dinosaurs.

  PublisherDOI

• Gross anatomy and histological analysis of manual unguals of Drepanosauromorpha (Sauropsida: Diapsida) and description of a new taxon from the Sonsela Member of the Chinle Formation (Late Triassic) of the southwestern United States

  The Anatomical Record · 2025-10-23

  articleOpen accessSenior author

  Unguals ("claws") are important tools that allow terrestrial vertebrates to navigate their environments, from subduing prey to climbing, running, and digging, with the shape of the element being broadly correlated with their ecological niche. Middle Triassic-Late Triassic drepanosauromorphs (Sauropsida: Diapsida) have been hypothesized to occupy various niches and functional modes from arboreality to fossoriality based on a range of evidence including claw anatomy. Hypertrophied manual unguals are present in many members of Drepanosauromorpha and vary in shape from the strongly curved, mediolaterally compressed, and dorsoventrally tall Drepanosaurus-like forms to the shallowly curved and mediolaterally wide unguals of Skybalonyx. Here, we detail and compare the external and internal features of western North American drepanosauromorph unguals. Using osteohistology and micro-computed X-ray tomography, we find that drepanosauromorph manual unguals possess a combination of characteristics that differentiate drepanosauromorph taxa. Using external and internal characteristics, we identify a new taxon of drepanosauromorph, Fabanychus monos gen. et sp. nov., from the upper Sonsela Member of the Upper Triassic Chinle Formation (~214 Ma) at Petrified Forest National Park in northeastern Arizona. More broadly, we find that drepanosauromorph manual unguals share a set of unique character states compared to other extant and extinct reptilian and mammalian unguals. Each drepanosauromorph ungual morphotype is diagnostic to a distinct taxon, revealing biostratigraphic patterns of the clade. The spatiotemporal and lithostratigraphic occurrence of drepanosauromorphs in equatorial Pangaea reveal a long record of the group, co-occurring taxa, and possible genus-level turnover in the middle Norian (~215 Ma).

  PublisherOA PDFDOI

• Rethinking thecodonty: the influence of two centuries of comparative dental anatomy on our understanding of tooth evolution

  Biology Letters · 2025-09-01 · 1 citations

  articleOpen access

  'Thecodont' refers to teeth implanted in sockets within the jaw, a condition traditionally associated with living mammals and crocodylians, which also coincidentally have teeth attached by ligaments to the socket walls (gomphosis). For over a century, the bony periodontium of many other amniotes has been described as a single tissue, 'bone of attachment', causing confusion over dental tissue homology. The conventional definitions of 'thecodonty' exclude species with fused teeth ('ankylothecodonts'), implying a fundamental difference between mammals, crocodylians and most other vertebrates. However, the stereotypically 'thecodont' attachment tissues have been discovered in representatives of all major amniote clades, showing that gomphosis and ankylosis likely stem from heterochronic changes in the timing and extent of cementum and alveolar bone mineralization. This challenges (i) previous hypotheses regarding the evolution of the amniote periodontium, (ii) the 'bone of attachment' paradigm, and (iii) the significance of 'thecodonty'. We suggest a new nomenclatural approach that incorporates recent histological and evolutionary research and divides thecodonty into anatomical categories to clarify their origin and evolution. We propose the terms anisothecodont and isothecodont to denote, respectively, asymmetric and symmetric implantation of teeth in their sockets. Regardless of the geometry of the connection, we propose using ankylosis and gomphosis to denote the mode of tooth attachment.

  PublisherOA PDFDOI

• Origin of conglomerate-hosted bonebeds at the base of the upper Permian Usili Formation, Ruhuhu Basin, Tanzania

  Journal of Vertebrate Paleontology · 2025-01-01 · 5 citations

  articleOpen access

  International audience

  PublisherOA PDFDOI

Recent grants

• Collaborative Research: An exceptional window into Late Triassic terrestrial ecosystems in the Western United States

  NSF · $62k · 2014–2018

• CAREER: Persistent vertebrate communities in deep time and the great Triassic-Jurassic vertebrate transition

  NSF · $622k · 2020–2026

Frequent coauthors

• Randall B. Irmis

  University of Utah

  131 shared

• Alan H. Turner

  101 shared

• Michelle R. Stocker

  Virginia Tech

  79 shared

• Nathan D. Smith

  77 shared

• Adam C. Pritchard

  Virginia Museum of Natural History

  65 shared

• Lovasoa Ranivoharimanana

  University of Antananarivo

  59 shared

• John J. Flynn

  American Museum of Natural History

  59 shared

• J. Michael Parrish

  57 shared

Education

• PhD, Geosciences

  Columbia University

  2009

• BA, Integrative Biology

  University of California Berkeley

  2004

Awards & honors

• Teaching Honors and Awards