Mary T Silcox

Mary T Silcox
University of Toronto | U of T · Department of Anthropology

BSc, PhD

About

143
Publications
46,408
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3,298
Citations
Introduction
My main research focus is the earliest phases of Primate Evolution, as documented by the fossil record. I'm also interested in the evolution of the brain in primates, and in Early Tertiary mammals more generally.
Additional affiliations
July 2010 - present
University of Toronto
Position
  • Professor (Associate)
July 2002 - July 2010
The University of Winnipeg
Position
  • Professor (Associate)
August 2000 - July 2010
Pennsylvania State University
Position
  • Research Assistant
Description
  • Research Assistant to Alan Walker
Education
September 1995 - June 2001
Johns Hopkins Medicine
Field of study
  • Functional Anatomy and Evolution
September 1991 - June 1995
University of Toronto
Field of study
  • Zoology, Anthropology

Publications

Publications (143)
Article
Full-text available
The evolution of the remarkably complex primate brain has been a topic of great interest for decades. Multiple factors have been proposed to explain the comparatively larger primate brain (relative to body mass), with recent studies indicating diet has the greatest explanatory power. Dietary specialisations also correlate with dental adaptations, p...
Article
Full-text available
The petrosal lobules (in whole or part homologous with the paraflocculi) of the cerebellum regulate functions associated with vision including smooth pursuit and velocity control of eye movements, suggesting a possible relationship between the petrosal lobules and behavioral adaptation. Previous studies have produced diverging conclusions regarding...
Article
Full-text available
Diet has been linked to the diversification of the bat superfamily Noctilionoidea, a group that underwent an impressive ecological diversification within Mammalia. For decades, studies have explored morphological adaptations and diversity of noctilionoid bats to reveal traits associated with their ecological diversity. Surprisingly, despite such in...
Article
Postmenopausal osteoporosis is a serious concern in aging individuals, but has not been explored for its potential to alter the shape of the inner ear by way of increased remodelling in the otic capsule. The otic capsule, or bony labyrinth, is thought to experience uniquely limited remodelling after development due to high levels of osteoprotegerin...
Article
Objectives Intraspecific shape variation in the recent Homo sapiens bony labyrinth has been assessed for association with sexual dimorphism, body size, and genetic differences, but has not been fully assessed for association with extrinsic factors, such as subsistence strategy and climate. While the skull overall is known to vary with these variabl...
Article
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Variation in postcanine teeth is relevant to answering questions about both taxonomy and diet. In such contexts, understanding the patterns and the amounts of variation present in a single species is fundamentally important. Here we use dental topographic analysis (DTA) to study variation in functional aspects of the lower second molar (n = 51) and...
Article
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Dental cavities or caries is a common disease among modern humans, affecting almost every adult. Caries frequency has been used to study dietary change in humans over time, based on an inferred tie between the incidence of caries and a carbohydrate-rich diet. However, the disease is not unique to our species. Among non-human primates, there is also...
Preprint
Full-text available
Diet has been linked to the diversification of the bat superfamily Noctilionoidea, a group that underwent an impressive ecological adaptive radiation within Mammalia. For decades, studies have explored morphological adaptations and diversity of noctilionoid bats to reveal macroevolutionary trajectories in their ecological diversity. Surprisingly, d...
Article
Full-text available
Due to their global distribution, invasive history, and unique characteristics, European rabbits are recognizable almost anywhere on our planet. Although they are members of a much larger group of living and extinct mammals [Mammalia, Lagomorpha (rabbits, hares, and pikas)], the group is often characterized by several well-known genera (e.g., Oryct...
Article
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Microsyopidae is a family of plesiadapiforms known from over 1500 stratigraphically controlled specimens from the southern Bighorn Basin of Wyoming spanning the first three million years of the early Eocene. The early Eocene is characterized by rapid fluctuations in climate during the period represented by this collection of microsyopids, making th...
Article
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How do brain size and proportions relate to ecology and evolutionary history? Here, we use virtual endocasts from 38 extinct and extant rodent species spanning 50+ million years of evolution to assess the impact of locomotion, body mass, and phylogeny on the size of the brain, olfactory bulbs, petrosal lobules, and neocortex. We find that body mass...
Article
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Maternal malnutrition during gestation and lactation is known to have adverse effects on offspring. We evaluate the impact of maternal diet on offspring bony labyrinth morphology. The bony labyrinth develops early and is thought to be stable to protect vital sensory organs within. For these reasons, bony labyrinth morphology has been used extensive...
Article
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The early Eocene of the southern Bighorn Basin, Wyoming, is notable for its nearly continuous record of mammalian fossils. Microsyopinae (?Primates) is one of several lineages that shows evidence of evolutionary change associated with an interval referred to as Biohorizon A. Arctodontomys wilsoni is replaced by a larger species, Arctodontomys nuptu...
Article
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Objectives: One role of dental pulp is in the upkeep and maintenance of dentine. Under wear, odontoblasts in the pulp deposit tertiary dentine to ensure the sensitive internal dental tissues are not exposed and vulnerable to infection. It follows that there may be an adaptive advantage for increasing molar pulp volume in anthropoid primate taxa th...
Article
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Identifying developmental explanations for the evolution of complex structures like mammalian molars is fundamental to studying phenotypic variation. Previous study showed that a “morphogenetic gradient” of molar proportions was explained by a balance between inhibiting/activating activity from earlier developing molars, termed the inhibitory casca...
Article
Full-text available
Reconstructing locomotor behaviour for fossil animals is typically done with post-cranial elements. However, for species only known from cranial material, locomotor behaviour is difficult to reconstruct. The semicircular canals (SCCs) in the inner ear provide insight into an animal's locomotor agility. A relationship exists between the size of the...
Article
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Treeshrews are small, Indomalayan mammals closely related to primates. Previously, three-dimensional geometric morphometric analyses were used to assess patterns of treeshrew lower second molar morphology, which showed that the positions of molar landmarks covary with intraordinal systematics. Another analysis used dental topographic metrics to tes...
Article
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Gummivory poses unique challenges to the dentition as gum acquisition may often require that the anterior teeth be adapted to retain a sharp edge and to resist loading because they sometimes must penetrate a highly obdurate substrate during gum extraction by means of gouging or scraping. It has been observed previously that the enamel on the labial...
Article
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Early lagomorphs are central to our understanding of how the brain evolved in Glires (rodents, lagomorphs and their kin) from basal members of Euarch-ontoglires (Glires + Euarchonta, the latter grouping primates, treeshrews, and colugos). Here, we report the first virtual endocast of the fossil lagomorph Megalagus turgidus, from the Orella Member o...
Article
Full-text available
Osipov and colleagues [American Journal of Physical Anthropology, 2(151) 2013] previously posited that the dimensions of the bony labyrinth exhibit sexual dimorphism. Using a recent sample of known sex, they produced an age-independent, multivariate equation to predict biological sex using several of these dimensions. We aim to test the applicabili...
Article
Full-text available
The Microsyopidae are extinct mammals from the late Paleocene–late Eocene of North America and the late Paleocene of Europe. While results from phylogenetic analyses support euarchontan affinities, specific relationships of microsyopids to other plesiadapiforms (plausible stem primates), Euprimates (crown primates), Scandentia (treeshrews), and Der...
Chapter
Full-text available
Evolution, Ecology and Conservation of Lorises and Pottos - edited by K. A. I. Nekaris March 2020
Chapter
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Evolution, Ecology and Conservation of Lorises and Pottos - edited by K. A. I. Nekaris March 2020
Chapter
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Evolution, Ecology and Conservation of Lorises and Pottos - edited by K. A. I. Nekaris March 2020
Article
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Molar morphology plays a key role in the systematics and behavioral interpretation of fossil taxa, so understanding the developmental patterns that shape occlusal morphology in modern taxa is of central importance to informing analysis of the fossil record. The shape of the outer enamel surface (OES) of a tooth is largely the result of the forming...
Article
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The ecology, and particularly the diet, of treeshrews (order Scandentia) is poorly understood compared to that of their close relatives, the primates. This stems partially from treeshrews having fast food transit times through the gut, meaning fecal and stomach samples only represent a small portion of the foodstuffs consumed in a given day. Moreov...
Article
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Little is known about the early evolution of the brain in rodents. We report on nine new virtual endocasts for one of the most primitive family of rodents, Ischyromyidae, based on five specimens of Pseudotomus and Notoparamys (Paramyinae) and four specimens of Reithroparamys and Rapamys (Reithroparamyinae), dating from the early Eocene to the late...
Article
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Landmark‐based 3D geometric morphometrics has rarely been employed to understand the relationship between endocranial shape, phylogeny and ecology. The goal of this study is to examine the endocranial morphology of members of the squirrel‐related clade by using these methods, and to develop a multi‐faceted framework for studying brain evolution app...
Article
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Paromomyidae has been thought to represent the longest-lived group of stem primates (plesiadapiforms), extending from the early Paleocene to late Eocene. We analyzed primate material from the late-middle Eocene of southern California that had initially been ascribed to cf. Phenacolemur shifrae. This material falls at the lowest end of the size rang...
Article
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Aplodontia rufa (mountain beaver) is the only extant member of the Aplodontidae. The fossil record indicates that this family displayed greater taxonomic and ecological diversity in the past, and that the burrowing adaptations of Aplodontia might be derived. We describe the first virtual endocasts of A. rufa and of three fossil aplodon-tids: Prosci...
Article
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Plesiadapiforms represent the first radiation of Primates, appearing near the Cretaceous-Paleogene boundary. Eleven families of plesiadapiforms are recognized, including the Paromomyidae. Four species of paromomyids from the early Eocene have been reported from Europe: Arcius fuscus Russell et al., 1967, Arcius lapparenti Russell et al., 1967, and...
Article
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Numerous factors have stimulated new enthusiasm for understanding the process of primate origins, including new fossil discoveries, improvements to methods for analyzing molecular data, and technological advances. These novel approaches have led to a better appreciation of the complexities of early primate evolution. Eight fundamental questions pro...
Presentation
Extant Sciuridae are diverse in term of taxonomy and ecology, unlike their closest relative the mountain beaver (Aplodontia rufa), which is the only extant species included in Aplodontoidea. The fossil record indicates that this group displayed more taxonomic and ecological diversity in the past. Previous studies suggest that the burrowing adaptati...
Article
Full-text available
Palaechthonid plesiadapiforms from the Palaeocene of western North America have long been recognized as among the oldest and most primitive euarchontan mammals, a group that includes extant primates, colugos and treeshrews. Despite their relatively sparse fossil record, palaechthonids have played an important role in discussions surrounding adaptiv...
Data
Electronic Supplementary Material: Oldest skeleton of a plesiadapiform provides evidence for an exclusively arboreal radiation of stem primates in the Paleocene
Chapter
Full-text available
Purgatorius is the oldest genus that has been attributed to the Order Primates. It appears near the Cretaceous–Paleogene boundary, approximately 66 million years ago, just as the nonavian dinosaurs are going extinct. Fossils attributed to this genus have been described from both the United States (Montana) and Canada (Saskatchewan). Mostly known fr...
Chapter
Full-text available
Plesiadapiforms are extinct mammals from the Paleocene and Eocene of North America, Europe, and Asia. They include the oldest forms that have been considered members of the Order Primates, dating to just after the extinction of the nonavian dinosaurs. There are 11 distinct families of plesiadapiforms, including over 140 named species, documenting a...
Article
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Very shortly after the disappearance of the non-avian dinosaurs, the first mammals that had features similar to those of primates started appearing. These first primitive forms went on to spawn a rich diversity of plesiadapiforms, often referred to as archaic primates. Like many living primates, plesiadapiforms were small arboreal animals that gene...
Article
Full-text available
Plesiadapiforms, appearing near the Cretaceous-Paleogene boundary, represent the first primate radiation and show a diverse array of tooth morphologies. Dental topographic metrics provide quantitative data on occlusal surface shape. We used three metrics, Dirichlet Normal Energy, Relief Index, and 3D Orientation Patch Count Rotated, to assess chang...
Article
Primate species typically differ from other mammals in having bony canals that enclose the branches of the internal carotid artery (ICA) as they pass through the middle ear. The presence and relative size of these canals varies among major primate clades. As a result, differences in the anatomy of the canals for the promontorial and stapedial branc...
Article
Well-preserved crania of notharctine adapiforms from the Eocene of North America provide the best direct evidence available for inferring neuroanatomy and encephalization in early euprimates (crown primates). Virtual endocasts of the notharctines Notharctus tenebrosus (n = 3) and Smilodectes gracilis (n = 4) from the middle Eocene Bridger formation...
Article
Paleogene micromomyids are small (∼10–40 g) euarchontan mammals with primate-like molars and postcrania suggestive of committed claw-climbing positional behaviors, similar to those of the extant arboreal treeshrew, Ptilocercus. Based primarily on evidence derived from dental and postcranial morphology, micromomyids have alternately been allied with...
Article
Full-text available
Dental topographic metrics provide quantitative, biologically meaningful data on the threedimensional (3D) form of teeth. In this study, three dental topographic metrics (Dirichlet normal energy (DNE), relief index (RFI), and orientation patch count rotated (OPCR)) are used to evaluate the presence of dietary niche overlap between North American pl...
Article
Full-text available
The evolution of the brain in rodents has rarely been studied from the perspective of the fossil record. Here we describe the first virtual endocast of a fossil rodent, pertaining to Ischyromys typus (ROMV 1007; Orellan North American Land Mammal Age [NALMA], Nebraska), and form comparisons with partial and complete natural endocasts pertaining to...
Data
The evolution of the brain in rodents has rarely been studied from the perspective of the fossil record. Here we describe the first virtual endocast of a fossil rodent, pertaining to Ischyromys typus (ROMV 1007; Orellan North American Land Mammal Age [NALMA], Nebraska), and form comparisons with partial and complete natural endocasts pertaining to...
Article
Full-text available
Understanding the pattern of brain evolution in early rodents is central to reconstructing the ancestral condition for Glires, and for other members of Euarchontoglires including Primates.We describe the oldest virtual endocasts known for fossil rodents, which pertain to Paramys copei (Early Eocene) and Paramys delicatus (Middle Eocene). Both speci...
Data
Full-text available
Understanding the pattern of brain evolution in early rodents is central to reconstructing the ancestral condition for Glires, and for other members of Euarchontoglires including Primates.We describe the oldest virtual endocasts known for fossil rodents, which pertain to Paramys copei (Early Eocene) and Paramys delicatus (Middle Eocene). Both speci...
Article
Full-text available
Objectives: The disappearance of the North American plesiadapoids (stem primates, or plesiadapiforms) in the latest Paleocene has been attributed to competition with rodents over dietary resources. This study compares molar morphology of plesiadapoids and early rodents to assess whether all taxa were adapted to consuming foods of the same structur...