About

Stephanie E. Pierce is a professor at Harvard University affiliated with the Museum of Comparative Zoology and the Department of Organismic and Evolutionary Biology. Her research focuses on major transitions in vertebrate evolution, particularly the complex evolutionary history of the mammalian regionalized spine. Her work involves utilizing advanced techniques such as 3D skeletal reconstructions and musculoskeletal modeling to investigate key evolutionary changes, including the sprawling-to-upright postural transition in mammals. Pierce's research also encompasses the study of stem tetrapods like Ichthyostega, where she has contributed to detailed flesh reconstructions and axial skeleton analyses. Collaborating with other experts, she explores muscle physiological properties through in vitro experiments and examines morphological and biomechanical disparity in Mesozoic crocodylomorphs. Her recent studies have contributed to understanding the origins of large predators in South America and the early rapid evolution and radiation of reptiles, highlighting the impact of global warming on these processes. Stephanie Pierce's work integrates paleontological data with biomechanical and evolutionary biology approaches to reveal the intricate history of vertebrate form and function.

Research topics

• Biology
• Computer Science
• Evolutionary biology
• Ecology
• Paleontology
• Artificial Intelligence
• Computational biology
• Medicine
• Geology
• Demography
• Genetics
• Physics

Selected publications

• Soft tissue constraints on hip joint mobility in a sprawling and parasagittal amniote

  Journal of Experimental Biology · 2026-04-10 · 1 citations

  articleSenior author

  Soft tissues, in addition to bones, are known to constrain joint mobility, yet the amount and type of influence remain underexplored. To investigate this further, we used XROMM to quantify ex vivo hip joint mobility during sequential removal of soft tissue layers (e.g. integument, extrinsic muscles, intrinsic muscles) in two amniotes that span a postural continuum: the sprawling tegu lizard (Salvator merianae) and the parasagittal Virginia opossum (Didelphis virginiana). We then compared ex vivo hip joint mobility spaces with in vivo joint excursions during steady-state walking recorded with bi-planar fluoroscopes. Our results demonstrate that integument passively restricts hip joint mobility in the tegu but not the opossum, while extrinsic muscles restrict mobility in the opossum but not the tegu due to the relatively bulky thighs of mammals. We further show that the tegu has greater ex vivo mobility than the opossum across tissue layers and during in vivo walking despite the classic ball-and-socket hip joint structure of mammals - a morphology traditionally interpreted as highly mobile. Finally, comparing in vivo hip joint excursion during walking with ex vivo mobility in both animals showed that soft tissues restrict stance phase excursions while swing phase movements approach the edge of viable ex vivo pose space. Collectively, our experimental findings provide novel insights and expand our understanding of the influence of soft tissues on joint mobility in vivo, ex vivo and in animals with unique postures, helping to aid future reconstructions of joint function and movement in extinct vertebrates.

  PublisherDOI

• Musculoskeletal function of stem tetrapod limbs

  Palaeontology · 2026-03-01

  articleSenior author

  Abstract The tetrapod water–land transition has been studied for more than a century, but questions about the locomotor function of early tetrapod limbs still remain. The limb and girdle skeletons of stem tetrapods are morphologically distinct from those of crown tetrapods, probably resulting in differences in range of motion and muscle leverage. To test hypotheses about their limb function, we built three‐dimensional musculoskeletal models of the stem tetrapods Acanthostega (Devonian) and Pederpes (Carboniferous), and of an extant salamander and lizard for comparison. We predicted that the joints of stem tetrapods would not be able to accommodate the full range of movements used by extant tetrapods during terrestrial walking, and that stem tetrapods would have less muscle leverage for resisting vertical forces and for hindlimb‐based propulsion. As expected, hip and shoulder mobility in the two stem tetrapods was incompatible with the kinematic patterns used by extant sprawling tetrapods. In contrast, their hip and shoulder depression muscle moment arms were similar to or greater than those of the crown tetrapods, and retraction moment arms were similar between the hip and shoulder in all four tetrapods, showing little evidence that the limbs of stem tetrapods were less adapted for weight support or HL‐driven locomotion. However, the moment arm results were sensitive to methodological choices such as joint angles and normalization. Comparison with additional extinct and extant tetrapods with different locomotor strategies could clarify how muscle moment arms are related to limb mechanics and aquatic versus terrestrial locomotion.

  PublisherDOI

• The Effects of Neuromuscular Training and Additive Visual Biofeedback on Landing Biomechanics and Sensorimotor Brain Activity in Young Female Athletes

  Medicine & Science in Sports & Exercise · 2026-02-19

  article

  INTRODUCTION: Anterior cruciate ligament (ACL) injuries are debilitating, often requiring surgical reconstruction and prolonged recovery. Female adolescent athletes are at particularly high risk for ACL injury and display distinct neuromuscular control patterns during jump landing that further increase injury risk. Neuromuscular training (NMT) designed to reduce injury risk can be enhanced with automated movement corrective biofeedback to improve neuromuscular control and landing biomechanics, however the central nervous system responses to targeted NMT that underlie adaptative biomechanical responses are not well-understood. PURPOSE: This study aimed to identify the effects of NMT on landing biomechanics and task-related brain activity, examine the relationship of changes in these variables, and determine if additive visual biofeedback (augmented versus sham) provides meaningful impact on injury-related outcomes. METHODS: This study included 55 female middle- and high-school athletes (agemean = 15.73 ± 1.40 years) who participated in ~6 weeks of NMT (3x/week; 18 sessions), which included up to 12 sessions of additive biofeedback (augmented: n = 28; sham: n = 27). Testing at pre- and post-NMT included a drop vertical jump task to assess landing biomechanics (sagittal and frontal plane hip and knee kinematics and kinetics) and a supine bilateral leg press task during functional magnetic resonance imaging to assess brain activity during a complex sensorimotor movement task. RESULTS: NMT improved landing biomechanics (η 2 range = 0.04-0.41, Ps < 0.049) and reduced task-related brain activity in sensorimotor regions (Prange = 0.015-0.032). Pre-post increases in postcentral gyrus brain activity predicted a reduction in left knee peak abduction moment (OR = 22.61, 95% CI [2.41, 212.21], P = 0.048). Additive biofeedback did not appear to influence outcomes of interest. CONCLUSIONS: NMT improved sensorimotor efficiency and landing biomechanics. However, increased somatosensory activity emerged as a critical predictor of improved landing patterns, highlighting the role of enhanced sensory processing in biomechanical risk reduction.

  PublisherDOI

• Functional trade-offs and innovation shape the adaptive landscape of aquatic mammal feeding

  iScience · 2025-12-05

  articleOpen access

  Functional trade-offs are inherent in phenotypes due to the need to balance multiple competing selection pressures. Traditionally regarded as constraints on evolution, trade-offs have recently been reframed as facilitators of adaptation via the changing relative importance of competing functions. Here, we examine these ideas through the lens of aquatic mammal feeding, testing a behavioral aquatic feeding framework where feeding strategies form an evolutionary continuum from terrestrial to increasingly more specialized water-based feeding styles. Specifically, we hypothesized that suction, suction filter, and ram filter feeding would have adaptive peaks closer together than raptorial feeding, and that taxa follow the functionally optimal evolutionary path (Pareto front) between adaptive peaks. Constructing morphofunctional adaptive landscapes from cetacean mandibles revealed strong support for this framework. Surprisingly, most cetaceans do not lie along the Pareto front between peaks, suggesting that novel functional innovations- most likely the specialized cetacean auditory pathway-are also influencing mandibular evolution.

  PublisherDOI

• Identifying Performance Variables Affecting Function in Children With SYNGAP1 Syndrome

  American Journal of Occupational Therapy · 2025-07-30

  article

  Abstract Date Presented 04/04/2025 SYNGAP1-related disorder (SYNGAP1-RD) is characterized by intellectual disability and developmental delay. Our study found significant correlations between functional independence, cognition, and fine motor skills in individuals with SYNGAP1-RD. Primary Author and Speaker: Charlene Woo Additional Authors and Speakers: Kristin Cunningham Contributing Authors: Sam Pierce

  PublisherDOI

• Adaptive landscapes unveil the complex evolutionary path from sprawling to upright forelimb function and posture in mammals

  PLoS Biology · 2025-06-24 · 2 citations

  articleOpen accessSenior authorCorresponding

  The 'sprawling-parasagittal' postural transition is a key part of mammalian evolution, associated with sweeping reorganization of the postcranial skeleton in mammals compared to their forebears, the non-mammalian synapsids. However, disputes over forelimb function in fossil synapsids render the precise nature of the 'sprawling-parasagittal' transition controversial. We shed new light on the origins of mammalian posture, using evolutionary adaptive landscapes to integrate 3D humerus shape and functional performance data across a taxonomically comprehensive sample of fossil synapsids and extant comparators. We find that the earliest pelycosaur-grade synapsids had a unique mode of sprawling, intermediate between extant reptiles and monotremes. Subsequent evolution of synapsid humerus form and functional traits showed little evidence of a direct progression from sprawling pelycosaurs to parasagittal mammals. Instead, posture was evolutionarily labile, and the ecological diversification of successive synapsid radiations was accompanied by variation in humerus morphofunctional traits. Further, synapsids frequently evolve toward parasagittal postures, diverging from the reconstructed optimal evolutionary path; the optimal path only aligns with becoming increasingly mammalian in derived cynodonts. We find the earliest support for habitual parasagittal postures in stem therians, implying that synapsids evolved and radiated with distinct forelimb trait combinations for most of their recorded history.

  PublisherDOI

• Digital volumetric modeling reveals unique body plan experimentation in the Devonian tetrapod Ichthyostega

  iScience · 2025-04-19 · 1 citations

  articleOpen accessSenior author

  and highlight a hitherto underappreciated level of morphological experimentation during the tetrapod transition to land.

  PublisherDOI

• The lower jaw of Devonian ray‐finned fishes ( <i>Actinopterygii</i> ): Anatomy, relationships, and functional morphology

  The Anatomical Record · 2025-07-21 · 1 citations

  articleOpen access

  Actinopterygii is a major extant vertebrate group, but limited data are available for its earliest members. Here we investigate the morphology of Devonian actinopterygians, focusing on the lower jaw. We use X-ray computed tomography (XCT) to provide comprehensive descriptions of the mandibles of 19 species, which span the whole of the Devonian and represent roughly two-thirds of all taxa known from more than isolated or fragmentary material. Our findings corroborate previous reports in part but reveal considerable new anatomical data and represent the first detailed description for roughly half of these taxa. The mandibles display substantial variation in size, spanning more than an order of magnitude. Although most conform to a generalized pattern of a large dentary and one or two smaller infradentaries, XCT data reveal significant differences in the structure of the jaw and arrangement of teeth that may be of functional relevance. We report the presence of a rudimentary coronoid process in several taxa, contributed to by the dentary and/or infradentaries, as well a raised articular region, resulting in a mandible with an offset bite and that functions as a bent level arm. Among the most striking variation is that of tooth morphology: several taxa have heterodont dentary teeth that vary in size and orientation, and multiple variations on enlarged, whorl-like and posteriorly-oriented anterior coronoid dentition are observed. We use these new data to revise morphological characters that may be of phylogenetic significance and consider the possible functional implicationds of these traits. The observed variation in mandible form and structure suggests previously unappreciated functional diversity among otherwise morphologically homogenous Devonian ray-finned fishes.

  PublisherDOI

• Evolutionary rate incongruences in squamates reveal contrasting patterns of evolutionary novelties and innovation

  2025-05-06 · 1 citations

  preprintOpen accessSenior author

  Understanding the rate of phenotypic evolution can reveal fundamental aspects of organismal evolutionary trajectories. Hence, several studies have attempted to detect the tempo of evolution for multiple organisms, although based on radically different datatypes (e.g., discrete and morphometric) and methods (phylodynamic vs comparative methods). Here, we ask whether these competing approaches provide comparable rate trajectories using an expanded squamate phylogenetic dataset that is matched (to the species-level) with new geometric morphometric data, while also assessing method robustness to fossil sampling. Our new squamate total-evidence time-tree suggests a new placement for putative stem iguanians while matching divergence time estimates of recent phylogenomic studies. We show that low fossil sampling inadvertently removes entire regions of the morphospace and contraction of crown clade phenotypic diversity, as morphospace boundaries are frequently delimited by transitional fossils. Critically, different datatypes produce radically incongruent rate patterns, which are further exacerbated by methodological differences. We suggest that phylogenetic discrete data (i.e., characters) are strongly influenced by neomorphisms and reveal phenotypic novelties, while morphometric data (i.e., shape) reflects changes in phenotypic refinement leading to phenotypic innovation. This conceptual distinction conciliates discrepant macroevolution trajectories across squamates, which we expect to be generalizable to other systems across the Tree of Life.

  PublisherOA PDFDOI

• Evolutionary Rate Incongruences in Squamates Reveal Contrasting Patterns of Evolutionary Novelties and Innovation

  Systematic Biology · 2025-09-27

  articleOpen accessSenior author

  Understanding the rate of phenotypic evolution can reveal fundamental aspects of organismal evolutionary trajectories. Hence, several studies have attempted to detect the tempo of evolution for multiple organisms, although based on different data types (e.g., discrete and morphometric) and methods (phylodynamic vs. comparative methods). Here, we ask whether these competing approaches provide comparable estimates of rate trajectories using an expanded squamate phylogenetic dataset that is matched (to the species-level) with new geometric morphometric data, while also assessing method robustness to fossil sampling. Our new squamate total-evidence time-tree suggests a new placement for several putative stem pleurodontan iguanians (Temujinidae) as stem acrodontans, whereas matching divergence time estimates of recent phylogenomic studies. We show that low fossil sampling inadvertently removes entire regions of the morphospace and leads to contraction of crown clade phenotypic diversity, as morphospace boundaries are frequently delimited by transitional fossils. Critically, different data types produce incongruent rate patterns, which are further exacerbated by methodological differences. We suggest that phylogenetic discrete data (i.e., characters) are strongly influenced by neomorphisms and reveal phenotypic novelties, whereas morphometric data (i.e., shape) reflect changes in phenotypic refinement leading to phenotypic innovation. This conceptual distinction conciliates discrepant macroevolution trajectories across squamates, which we expect to be generalizable to other systems across the Tree of Life.

  PublisherOA PDFDOI

Recent grants

• DISSERTATION RESEARCH: The Evolution of Crocodylian Cranial Development

  NSF · $22k · 2017–2020

• DISSERTATION RESEARCH: Macroevolutionary drivers of digit reduction in fossil horses

  NSF · $16k · 2017–2019

• Collaborative Research: Evolving the mammalian forelimb: modeling musculoskeletal transformation in the forerunners of mammals

  NSF · $646k · 2018–2023

• Integrating the fossil record with computer simulation to reconstruct posture and locomotor evolution in the ancestors of mammals

  NSF · $544k · 2021–2025

• Collaborative Research: Functional evolution of the mammalian backbone: insights from the forerunners of mammals

  NSF · $323k · 2015–2018

Frequent coauthors

• John R. Hutchinson

  Royal Veterinary College

  39 shared

• Tiago R. Simões

  Princeton University

  32 shared

• Michael W. Caldwell

  University of Alberta

  26 shared

• Katrina E. Jones

  University of Manchester

  21 shared

• Kenneth D. Angielczyk

  Field Museum of Natural History

  19 shared

• Júlia Molnár

  New York Institute of Technology

  18 shared

• Lionel Hautier

  Institut de Recherche pour le Développement

  15 shared

• Andrew A. Biewener

  15 shared