Susannah Porter

Susannah Porter

Office Location

Webb 1037


Precambrian and Cambrian Paleobiology, Early Eukaryote and Early Animal Evolution, the Evolution of Biomineralization.


Harvard University, Ph.D. Biology, 2002

Yale University, B.A. Mathematics, 1995, magna cum laude


The early evolution and radiation of eukaryotes and its relationship to environmental change, and the fossil record of the earliest skeletal animals. Research involves fieldwork, microscopy, descriptive systematics, and paleoecological and taphonomic analyses.


Citation Summary: Google Scholar

Porter Lab Publications

* denotes student; ° denotes postdoc

°Riedman, L.A., Porter, S.M., dos Santos, A., Lechte, M., Halverson, G.P. In revision. Late Paleoproterozoic fossils of the Limbunya Group, Birrindudu Basin, northern Australia. Papers in Palaeontology.

*Woltz, C.M., Anderson, R.P. Tosca, N.J., Porter, S.M. In revision. The role of clay minerals in the preservation of Precambrian organic-walled microfossils. Geobiology.

Dehler, C.M., Schmitz, M., Bullard, A., Porter, S.M., Timmons, M., Karlstrom, K., Cothren, H. In revision. Precise U-Pb age models refine Neoproterozoic western Laurentian rift initiation, correlation, and Earth system changes. Precambrian Research.

Porter, S.M., and °Riedman, L.A. In press. Frameworks for interpreting the early fossil record of eukaryotes. Annual Review of Microbiology.

Anderson, R., *Woltz, C.M., Tosca, N.J., Porter, S.M., Briggs, D.E.G. 2023. The importance of fossilisation to our reading of animal antiquity. Trends in Ecology and Evolution.

*Tingle, K., Porter, S.M., Raven, M., Czaja, A., Webb, S., Bloeser, B. 2023. Organic preservation of vase-shaped microfossils from the late Tonian Chuar Group, Grand Canyon, Arizona. USA. Geobiology.

Planavsky, N.J., Asael, D., Rooney, A.D., Robbins, L.J., Gill, B.C., Dehler, C.M., Cole, D.B., Porter, S.M., Love, G.D., Konhauser, K.O., and Reinhard, C.T. 2022. A sedimentary record of the evolution of the global marine phosphorous cycle. Geobiology. doi:10.1111/gbi.12536

Mänd, K., Planavsky, N.J., Porter, S.M., Robbins, L.J., Wang, C., Kreitsmann, T., Paiste, K., Paiste, P., Romashkin, A.E., Deines, Y.E., Kirsimäe, K., Lepland, A., Konhauser, K.O. 2022. Chromium evidence for protracted oxygenation during the Paleoproterozoic
Earth and Planetary Science Letters 584: 117501.

Wang, C., Lechte, M.A., Reinhard, C.T., Asael, D., Cole, D.B., Halverson, G.P., Porter, S.M., Galili, N., Halevy, I., Rainbird, R.H., Lyons, T.W., Planavsky, N.J. 2022. Strong evidence for a weakly oxygenated ocean-atmosphere system during the Proterozoic. Proceedings of the National Academy of Sciences 119: e2116101119.

Farrell, Ú. C., Samawi, R., Anjanappa, S., Klykov, R., Adeboye, O. O., °Agić, H., ... Porter, S.M., ... & Sperling, E. A. 2021. The Sedimentary Geochemistry and Paleoenvironments Project. Geobiology.

Shields-Zhou, G.A., Strachan, R.A., Porter, S.M., + 33 more authors. 2021. A template for an improved rock-based subdivision of the pre-Cryogenian time scale. Journal of the Geological Society 179

°Moore, J.L, Porter, S.M., Webster, M., and Maloof, A. 2021. Chancelloriid sclerites from the Dyeran–Delamaran (lower–middle Cambrian) boundary interval of the Pioche–Caliente region, Nevada, USA. Papers in Palaeontology 7:565-623.

°Riedman, L. A., Porter, S. M., and Czaja, A. 2021. Globally distributed phosphatic scale microfossils of the mid-Neoproterozoic. Geobiology.

*Woltz, C., Porter, S., °Agic, H., Dehler, C., Junium, C., °Riedman, L. A., Hodgkiss, M., Wörndle, S., and Halverson, G. 2021. Total organic carbon and the preservation of organic-walled microfossils in Precambrian shale. Geology 49,

Halverson, G., Porter, S., and Shields-Zhou. 2020. The Tonian and Cryogenian periods. In Gradstein, F., Ogg, J., Schmitz, M., and Ogg, G., Geologic Timescale 2020. Elsevier.

Porter, S. M. 2020. Insights into eukaryogenesis from the fossil record. Interface Focus 10 (4), 20190105.

Cole, D., Mills, D., Erwin, D., Sperling, E., Porter, S., Reinhard, C., and Planavsky, N. 2020. On the co-evolution of surface oxygen levels and animals. Geobiology 18 (3), 260-281.

°Moore, J.L, Porter, S.M., Webster, M., and Maloof, A. 2020. Chancelloriid sclerites from the Dyeran–Delamaran (lower–middle Cambrian) boundary interval of the Pioche–Caliente region, Nevada, USA. Papers in Palaeontology

Dahl, T. W., Connelly, J. M., Li, D., Kouchinsky, A., Gill, B. C., Porter, S., Maloof., A., and Bizzarro, M. 2019. Atmosphere-ocean oxygen and productivity dynamics during early animal radiations. Proceedings of the National Academy of Sciences 116 (39), 19352-19361.

Gilbert, P., Porter, S., Sun, C-Y., Xiao, S., Gibson, B.M., Shenkar N., and Knoll. A. 2019. Biomineralization by particle attachment in early animals. Proceedings of the National Academy of Sciences 116 (36) 17659-17665.

Morais, L., Lahr D., Rudnitzki, I., Freitas, B., Romero, G., Porter, S., Knoll, A., and Fairchild, T. 2019. Insights into VSM diversity and Neoproterozoic biostratigraphy in the light of recent Brazilian discoveries. Journal of Paleontology 93(4): 612-627.

Porter, S. and °Riedman, L. A. 2019. Evolution: ancient fossilized amoebae find their home in the tree. Current Biology 29, R200-R223.

Porter, S.M., Agic°, H., and Riedman, L.A. 2018. Anoxic ecosystems and early eukaryotes. Emerging Topics in Life Sciences 2:299-309.

Lyons, T.W., Droser, M.L., Lau, K.V., and Porter, S.M. 2018. Early Earth and the rise of complex life. Emerging Topics in Life Sciences 2:121-124.

Halverson, G.P., Porter, S.M., Gibson, T.M. 2018. Dating the late Proterozoic stratigraphic record. Emerging Topics in Life Sciences 2:137-147.

Shields-Zhou, G., Halverson, G., and Porter, S. 2018. Descent into the Cryogenian. Precambrian Research.

Moore°, J.L., and Porter, S.M. 2018. Plywood-like shell microstructures in hyoliths from the middle Cambrian (Drumian) Gowers Formation, Georgina Basin, Australia. Palaeontology 61: 441-467.

Riedman*, L.A., Porter, S.M., and Calver, C. 2017. Vase-shaped microfossil biostratigraphy with new data from Tasmania, Svalbard, Greenland, Sweden and the Yukon. Precambrian Research.

Vendrasco, M. J., Checa. A.G., and Porter, S.M. 2017. Periostracum and fibrous shell microstructures in the unusual Cambrian hyolith Cupitheca. Spanish Journal of Paleontology 32:95-101. 

Dehler, C.M., Gehrels, G., Porter, S.M., Heizler, M., Cox, G., Karlstrom, K., Crossey, L., and Timmons, M. 2017. Synthesis of the 780-740 Ma Chuar Group, Uinta Mountain Group, and Pahrump (ChUMP) groups, western USA: Implications for Laurentia-wide cratonic marine basins. Geological Society of America Bulletin 129: 607-624. doi: 10.1130/B31532.1

Porter, S.M. 2016. Tiny vampires in ancient seas: evidence for predation via perforation in fossils from the 780–740 Ma Chuar Group, Grand Canyon, USA. Proceedings of the Royal Society B 283: 20160221.

Porter, S.M., and *Riedman, L. A. 2016. Systematics of organic-walled microfossils from the ~780–740 Ma Chuar Group, Grand Canyon, Arizona. Journal of Paleontology 90: 815-853.

*Riedman, L. A. and Porter, S.M. 2016. Organic-walled microfossils of the early to mid-Neoproterozoic Alinya Formation, Officer Basin, Australia. Journal of Paleontology 90: 854-897.

Shields-Zhou, G., Porter, S.M., and Halverson, G.P. 2016. A new rock-based definition for the Cryogenian Period (circa 720 – 635 Ma). Episodes 39: 3–8.

Brocks, J. J., Jarrett, A.J.M., Sirantoine, E., Kenig, F., Moczyd?owska, M., Porter, S. and Hope, J. 2015. Early sponges and toxic protists: possible sources of cryostane, an age diagnostic biomarker antedating Sturtian Snowball Earth. Geobiology. doi:10.1111/gbi.12165.

Vendrasco, M. J., Rodríguez-Navarro, A. B., Checa, A. G., Devaere, L., and Porter, S.M. 2015. To infer the early evolution of mollusc shell microstructures. Pp. 113-133 in Biomineralization: From Fundamentals to Biomaterials and Environmental Issues, Marin, F., Brümmer, F., Checa, A., Furtos, G., Lesci, I.G., and Siller, L. (eds.). Key Engineering Materials, v. 672. 

*Riedman, L. A., Porter, S. M., Halverson, G. P., Hurtgen, M. T., and Junium, C.K. 2014. Organic-walled microfossil assemblages from glacial and interglacial Neoproterozoic units of Australia and Svalbard. Geology 42:1011-1014. 

*Moore, J.L., Porter, S.M., and Li, G.. 2014. Two unusual small shelly fossils from the lower Cambrian of southeastern Shaanxi Province, China. Journal of Paleontology 88(2): 348-358.

*Moore, J.L., Li, G., and Porter, S.M. 2013. Chancelloriid sclerites from the Lower Cambrian (Meishucunian) of eastern Yunnan, China, and the early history of the group. Palaeontology 57: 833-878. 

Dehler, C. M., Porter, S.M., Timmons, M., and *Nagy, R.M. 2012. The Neoproterozoic Earth System revealed from the Chuar Group of Grand Canyon. M. Timmons and K. E. Karlstrom (eds.), Geological Overview of the Butte Fault/East Kaibab Monocline Area of Grand Canyon. Geological Society of America Special Papers, 489: 49-72.

Vendrasco°, M. J., Kouchinsky, A., Porter, S. M., and C. Fernandez. 2011. Phylogeny and escalation in Mellopegma and other Cambrian molluscs. Palaeontologica Electronica 14(2):11A. 

Porter, S. M. 2011. The rise of predators. Geology 39: 607-608. pdf

Maloof, A.C., Porter, S.M., *Moore, J.L., Dudás, F.Ö., Bowring, S.A., Higgins, J. A., Fike, D. A., , and M. P. Eddy. 2010. The earliest Cambrian record of animals and ocean geochemical change. GSA Bulletin 122 (11/12): 1731-1774.

*Moore, J. L. Porter, S. M., Steiner, M., and G. Li. 2010. Cambrothyra ampulliformis, an unusual coeloscleritophoran from the lower Cambrian of Shaanxi Province, China. Journal of Paleontology 84(6): 1040-1060. 

Porter, S.M. 2010. Calcite and aragonite seas and the de novo acquisition of carbonate skeletons. Geobiology 8: 256-277.

Vendrasco°, M. J., Porter, S. M., Kouchinsky, A. G., Li, G., and C. Z. Fernandez. 2010. Shell microstructures in early mollusks. Festivus 42: 43-54. 

Maloof, A. C., Ramezani, J., Bowring, S. A., Fike, D. A., Porter, S. M., and M. Mazouad. 2010. Constraints on early Cambrian carbon cycling from the duration of the Nemakit-Daldynian-Tommotian boundary d13C shift, Morocco. Geology 38: 623-626.

Johnston, D. T., Poulton, S. W., Dehler, C. M., Porter, S. M., Husson, J., Canfield, D. E., and A. H. Knoll. 2010. An emerging picture of Neoproterozoic ocean chemistry: Insights from the Chuar Group, Grand Canyon, USA Earth and Planetary Science Letters 290: 64-73.

Halverson, G. P., Hurtgen, M. T., Porter, S. M., and A. S. Collins. 2009. Neoproterozoic-Cambrian biogeochemical evolution. Pp. 351-365 in: Gaucher, C., Sial, A., Halverson, G. P., and H. Frimmel (eds.). Neoproterozoic-Cambrian Tectonics, Global Change and Evolution: A Focus on Southwestern Gondwana. Elsevier, Developments in Precambrian Geology Series.

Vendrasco°, M. J., Porter, S. M., Kouchinsky, A. G., Li, G., and C. Z. Fernandez. 2010. New data on molluscs and their shell microstructures from the middle Cambrian Gowers Formation, Australia. Palaeontology 53: 97-135.

Vendrasco°, M. J. Li, G., Porter, S. M., and C. Z. Fernandez. 2009. New data on the enigmatic Ocruranus-Eohalobia group of early Cambrian small skeletal fossils. Palaeontology 52:1373-1396. 

*Nagy, R. M., Porter, S. M., Dehler, C. M., and Y. Shen. 2009. Biotic turnover driven by eutrophication before the Sturtian low-latitude glaciation. Nature Geoscience 2:414-417. 

Porter, S. M. 2008. Skeletal microstructure indicates chancelloriids and halkeriids are closely related. Palaeontology 51(4): 865-879. 

Porter, S. M. 2007. Seawater chemistry and early carbonate biomineralization. Science 316:1302. 

Dehler, C. M.,  Porter, S.M., D. A Sprinkel, and L.D. DeGrey. 2007. The Neoproterozoic Uinta Mountain Group revisited: a synthesis of recent work on the Red Pine Shale and undivided clastic strata, northeastern Utah. Pp. 151-166 in Link, P.K., & Lewis, R. (eds.): Proterozoic Geology of Western North America and Siberia. SEPM Special Publication 86. 

Porter, S. M. 2006. The Proterozoic fossil record of heterotrophic protists. In Xiao, S., and Kaufman, A.J. (eds.), Neoproterozoic Geobiology. Geobiology Series. 

*Nagy, R.M., and Porter, S.M.. 2005. Paleontology of the Neoproterozoic Uinta Mountain Group. In Dehler, C.M., Pederson, J.L., Sprinkel, D.A., and Kowallis, B.J. (eds.), Uinta Mountain Geology. Utah Geological Association Publication 33, p. 49-62. 

Dehler, C.M., D. A. Sprinkel, and S. M. Porter. 2005. Neoproterozoic Uinta Mountain Group of northeastern Utah: pre-Sturtian geographic, tectonic, and biologic evolution. In Pederson, J., and Dehler, C.M. (eds.), Interior Western United States. Geological Society of America Field Guide 6, p.1-26.

Porter, S. M. 2004. Halkieriids in Middle Cambrian phosphatic limestones from Australia. Journal of Paleontology 78(3): 574-590.

Porter, S. M., A. H. Knoll, and P. Affaton. 2004. Chemostratigraphy of a Neoproterozoic ‘cap’ carbonate from the Volta Basin, West Africa. Precambrian Research 130: 99-112. 

Porter, S. M. 2004. Closing the ‘phosphatization window’: implications for interpreting the record of small shelly fossils. Palaios 19: 178-183. 

Porter, S. M. 2004. The fossil record of early eukaryotic diversification. Paleontological Society Papers 10: 35-50. 

Porter, S. M., R. Meisterfeld, and A. H. Knoll. 2003. Vase-shaped microfossils from the Neoproterozoic Chuar Group, Grand Canyon: a classification guided by modern testate amoebae. Journal of Paleontology 77(3): 409-429. l

Porter, S. M., and A. H. Knoll. 2000. Neoproterozoic testate amoebae: evidence from vase-shaped microfossils in the Chuar Group, Grand Canyon. Paleobiology 26(3): 360-385. 

Karlstrom, K. E., S. A. Bowring, C. M. Dehler, A. H. Knoll, S. M. Porter, D. J. Des Marais, A. B. Weil, Z. D. Sharp, J. W. Geissman, M. B. Elrick, J. M. Timmons, L. J. Crossey, and K. L. Davidek. 2000. Chuar Group of the Grand Canyon: record of breakup of Rodinia, associated change in the global carbon cycle, and ecosystem expansion by 740 Ma. Geology 28: 619-622. 

Dehler, C., S. Porter, and K. Karlstrom. 1999. Grand Canyon Supergroup. Grand Canyon River Guides 12(3): 31-35.


Earth 2: Physical geology

Introduction to the science of the Earth; properties and processes of its surface and interior, including plate tectonics, volcanism, earthquakes, glaciation, mountain building, formation of rocks, minerals, and the structural basis of landforms. 


Earth 7: Age of Dinosaurs

The origin and diversification of dinosaurs, and the evolutionary relationship of dinosaurs (including their living descendents) to other major groups of vertebrates. Broad introduction including discussion of dinosaur ecology, anatomy, extinction, and paleogeography. 


Earth 111/EEMB 136: Principles of Paleontology (with Prof. Bruce Tiffney)

The ecologic structure and evolution of the biosphere as illustrated by the fossil record. 


Earth 143: The Early Evolution of Life and its Environmental Context

The first 3.5 billion years of life and the environmental context in which it evolved. Highly multidisciplinary, drawing on evidence from geology, geochemistry, paleontology, and comparative biology. 


Earth 144: Invertebrate Paleontology

Important topics in paleobiology are discussed in the context of the evolutionary history of invertebrate animal life. These include macroevolutionary theory, diversification and extinction events, ecological and geobiological interactions through time, and the incompleteness of the fossil record. 


Earth 270: Paleoclub Seminar

Selected topics in paleobiology. Past seminar topics include: the Cambrian explosion, the history of paleontology, the rise of oxygen, Tree-thinking, snowball Earth, eukaryote diversity, the writings of Stephen Jay Gould, and the evolution of development.