Dr. Mary T. Silcox, PhD

Dr. Mary T. Silcox

Dr. Mary T. Silcox

Dr. Silcox is an Associate Professor in the Department of Anthropology at the University of Toronto Scarborough (UTSC), and a Research Associate at the Royal Ontario Museum and the Florida Museum of Natural History.

She received her PhD in 2001 from the Center for Functional Anatomy and Evolution at the Johns Hopkins School of Medicine as a student of Dr. Kenneth D. Rose, and completed a research assistantship/postdoc with Dr. Alan Walker at Penn State from 2000-2002.  From 2002-2010, she was a member of the Anthropology department at the University of Winnipeg.  She has been at UTSC since 2010.

Dr. Silcox’s full CV: SilcoxCV November 2017

Research Interests

1.  Anatomy and evolution of stem primates

 

Dr. Silcox studying microsyopid teeth from the Bighorn Basin

Dr. Silcox studying microsyopid teeth from the Bighorn Basin

Much of Dr. Silcox’s work focusses on plesiadapiforms. Plesiadapiforms are Paleocene-Eocene fossil mammals known from North America, Europe and Asia—their temporal distribution stretches from approximately 65 to 40 million years ago.  Her analyses suggest that they represent the most primitive primates known (Silcox, 2001; Bloch et al., 2007; Silcox et al. 2010).  Dr. Silcox has a particular expertise in craniodental anatomy.  She is involved in collaborative work (with Drs. J.I. Bloch and D.M. Boyer) to describe several new cranial specimens for the group.  She is also studying (with Drs. Ken Rose and Amy Chew) a collection of over 1500 microsyopid plesiadapiforms from known stratigraphic levels in the Bighorn Basin, Wyoming.  As the largest sample known for any single group of stem primates, this material allows for an unprecedented understanding of evolutionary change through time.

 

2.  Understanding the evolution of the brain in early primates

 

On average, living primates have larger brains than members of other mammalian groups, and this feature has long been emphasized as a key feature of the Order.  Until recently, very little was known about the earliest phases in the evolution of this trait in primates. Dr. Silcox and her colleagues (Silcox et al., 2009a, 2010a) published the first virtual endocasts for plesiadapiforms, which provide a preliminary basis to test some of the competing ideas about why primates evolved large brains.  In particular, they suggest that significant brain size increase did not occur until the crown primate (euprimate) node, perhaps in association with improved visual processing.  Moving forward, Dr. Silcox is continuing to study endocasts from plesiadapiforms, primitive euprimates, and closely related non-primate groups including treeshrews and rodents, with the goal of better characterizing the process of early brain expansion and elaboration in primates and their relatives.

 

3.  The ecological context of the early primates from the Bighorn Basin

 

Work at the Dorsey Creek Quarry (Bighorn Basin, Wyoming)

Work at the Dorsey Creek Quarry (Bighorn Basin, Wyoming)

The Bighorn Basin is one of the most productive areas in the world to find fossils from the latest Paleocene and earliest Eocene.  Much of this material comes from prospecting (i.e., walking around looking for fossils).  There are a limited number of very rich concentrations of material which can be quarried to produce samples that are taxonomically rich, and well controlled in terms of temporal and spatial extent.  These quarry samples provide very high resolution windows into the past that lack some of the issues (e.g., size bias in favour of larger forms) associated with prospected samples.  Dr. Silcox worked on some of these samples during her graduate work (Silcox and Rose, 2001), and her team re-opened the particularly rich Dorsey Creek Quarry (DCQ) in 2013.  Moving forward, she plans to continue to excavate DCQ, and to work with collaborators Drs. K.D. Rose and Amy Chew to seek other high concentration sites that can be quarried.

 

4.  Refining the phylogenetic framework of Euarchonta (Primates + Dermoptera + Scandentia)

 

Most workers agree that the closest living relatives of primates are dermopterans (gliding mammals from Southeast Asia, referred to as mitten gliders or colugos) and scandentians (treeshrews, also from Southeast Asia).  However, the branching order amongst these groups remains a matter of debate, with various analyses recovering different sister taxa for Primates.  Resolving this issue was one of the goals of the NSF-funded Assembling the Tree of Life (AToL) for mammals project, upon which Dr. Silcox was a co-PI.  The results of the analysis (O’Leary et al., 2012) suggest that the sister taxon of Primates is Sundatheria (Scandentia + Dermoptera).  However, this project was limited by restrictive taxon sampling (e.g., only one fossil primate species, and no plesiadapiforms), so more work is definitely needed.  Moving forward, we need to significantly increase the number of relevant fossil taxa studied in the context of the AToL character list, and probably add in characters that are specifically pertinent to the problem of euarchontan relationships.

 

5.  Primates from the Crazy Mountains Basin

 

Since 2004 Dr. Silcox has been involved in a collaborative project with Drs. J.I. Bloch (Florida Museum of Natural History) and D.M. Boyer (Duke University) to collect Paleocene mammals in the Crazy Mountains Basin of Montana (CMB).  She is working on a project to describe material from the CMB that pertains to the very primitive plesiadapiform group, Palaechthonidae.  They are also currently working at a very productive fossil quarry (Donald Quarry), which is from a poorly understood period in terms of broad scale patterns of mammalian evolution in North America:  the Torrejonian-Tiffanian boundary.  Ultimately, they hope to gain a better understanding of the early evolution of primates in one of the classic areas for discovering plesiadapiforms.

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