Research

Our research: Using anatomy to understand ecology
and evolution

We use the fossil record to investigate changes in mammalian morphology over millions of years during the Oligocene and Miocene (ca. 30 to 5 Million years ago). Our goal is to understand the evolution of modern mammalian communities and their responses to diverse dramatic climatic and environmental perturbations. We combine comparative anatomy, museum work, and biostatistics to infer the taxonomic and ecological affinities of extinct taxa and shed light on the tempo and mode of mammalian evolution.

We seek to answer three main questions:

1. What was the pattern of taxonomic change within mammalian communities during the Oligo-Miocene?

2. What was the ecology of Cenozoic mammals?

3. How did environmental change impact mammalian Biodiversity 30 to 15 million years ago?

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1. What was the pattern of taxonomic change within mammalian communities during the Oligo-Miocene?

Introduction:

The study of the taxonomic affinities and phylogenetic relationships of fossil mammals helps resolve patterns of diversity through time. Large sample sizes of fossils identified to fine taxonomic levels (i.e. species or genus levels) are necessary to determine changes in biodiversity through time and space, including species richness and relative abundances. To build large datasets of well-identified fossils, we combine studies of homologies, linear morphometrics, and geometric morphometrics in modern and fossil mammals and investigate the potential of isolated elements of the vertebrate skeletons to be taxonomically informative. The study of the systematics and phylogenetic affinities of fossil mammals also helps decipher biogeographic patterns. By understanding the evolutionary history of key taxa, my students and I can determine immigration events during the Oligocene and Miocene.

Current projects:

  • We are studying the cranial and dental variation within and across species of modern as well as extinct pocket gophers to refine our understanding of the rise and demise of the dominant burrowing rodent group ca. 28 to 23.5 million years ago. We are working to develop a phylogenetic framework for the very species-rich family Geomyidae. This will enable an analysis of the evolution of burrowing in gophers and their fossil relatives.
  • We are also working towards resolving the taxonomic and phylogenetic affinities of the beavers from the Cabbage Patch beds of western Montana, where we did field work from 2011 to 2015.

Relevant publications:

Calede, J. and Glusman, J. 2017. Geometric morphometric analyses of worn cheek teeth help identify extant and extinct gophers (Rodentia: Geomyidae). Palaeontology 60: 281-307.

Davis, E. B., and Calede, J. 2012. Extending the utility of artiodactyl postcrania for species-level identifications using multivariate morphometric analyses Paleontologia Electronica 15.1.1A. → Full text/PDF

Calede J., and Hopkins, S.S.B. 2012. Intraspecific versus interspecific variation in Miocene Great Basin mylagaulids: implications for evolutionary history. Zoological Journal of the Linnean Society 164:427–450.

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2. What was the ecology of Cenozoic mammals?

Introduction:

We use fossil and modern specimens from museums and our own collecting combined with comparative anatomy and morphometrics to characterize the ecology of fossil mammals from their morphology including diet, locomotion, and body mass. We focus on select clades of mammals that are abundant in fossil assemblages or represent potential keystone taxa that had a disproportionate effect on their ecosystem. This work is a critical step in reconstructing the interactions of extinct organisms with each other and their environment as well as the evolution of specific locomotions or dietary ecologies.

Current projects:

  • We are studying the locomotion of a fossil beaver from Montana using the morphology of its ankle bones and comparisons with modern rodents.
  • We are collaborating with Drs. Joshua Samuels and Meng Chen on the locomotion of extinct gophers.
  • We are working with Drs. Nicholas Famoso and Samantha Hopkins on better understanding the changes in tooth morphology in mylagaulids with environmental change.

Relevant publications:

Calede, J., Kehl, W.A., and Davis, E.B. (in press). Craniodental morphology and diet of Leptarctus oregonensis (Mammalia, Carnivora, Mustelidae) from the Mascall Formation (Miocene) of central Oregon. Journal of Paleontology

Wilson, G., Ekdale, E., Hoganson, J., Calede, J., and Vander Linden, A. 2016. A large carnivorous mammal from the Late Cretaceous and the North American origin of marsupials. Nature Communications 7: 13734. → Full text/PDFPress release

Calede, J. 2014. Skeletal morphology of Palaeocastor peninsulatus (Rodentia, Castoridae) from the Fort Logan Formation of Montana (Early Arikareean): ontogenetic and paleoecological interpretations. Journal of Mammalian Evolution 21: 223-241.

Calede, J., and Hopkins, S.S.B. 2012. New material of Alphagaulus pristinus (Mammalia: Rodentia: Mylagaulidae) from the Deep River Formation (Montana, USA): implications for ecology, ontogeny, and phylogeny. Journal of Vertebrate Paleontology 32:151–165.

 

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3. How did environmental change impact mammalian Biodiversity 30 to 15 million years ago?

Introduction:

The analyses of the taxonomic and ecological affinities of individual fossil mammals contributes to reconstructing the evolutionary history of specific lineages. Combined together, they enable more comprehensive analyses of entire mammalian faunas through time. We analyze large samples of ecomorphological data collected from specimens using univariate and multivariate statistics to track mammalian biodiversity over evolutionary timescales.

Current projects:

  • We are studying changes in diet and locomotion through time in mammalian communities of the Cabbage Patch Beds of western Montana. In addition to uncovering intriguing correlations between changes in the ecological composition of mammalian communities and changes in the environment through time, we are analyzing links between taxonomic and ecological turnovers.
  • We are working to expand our analysis to other deposits of the Rocky Mountains.

Relevant publications:

Calede, J. 2016. Comparative taphonomy of the mammalian remains from the Cabbage Patch beds of western Montana (Renova Formation, Arikareean): contrasting depositional environments and specimen preservation. Palaios 31: 497-515. → Cover article

Calede, J., Hopkins, S.S.B., and Davis, E.B. 2011. Turnover in burrowing rodents: the role of competition and habitat change. Palaeogeography, Palaeoclimatology, Palaeoecology 311:242–255.