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Department of Paleobiology

  • Thomas R. Waller
  • Curator of Mollusks
  • Phone:   202-633-1359
  • Fax:   202-786-2832
  • E-mail Address:   wallertat SI dot edu
  • Mailing Address:
    Smithsonian Institution
    PO Box 37012, MRC 121
    Washington, DC 20013-7012
  • Shipping Address:
    Smithsonian Institution
    National Museum of Natural History
    10th & Constitution NW
    Washington, DC 20560-0121


Ph.D. Columbia University, 1966
M.S. University of Wisconsin, 1961
B.S. University of Wisconsin, 1959

Research Interests

My research area is the evolution of the molluscan class Bivalvia (clams, scallops, oysters) with emphasis on morphology, ecology, geologic history, phylogeny, and systematics.  Basically, I seek to erase the artificial boundary between zoology and paleontology by applying the results of detailed studies of living bivalves to the interpretation of their fossil counterparts on a worldwide basis and extending through their entire 550 million year fossil record.  On the geological side, my work interfaces with the subdisciplines of biostratigraphy,  paleogeography, paleoecology, and ocean history; on the zoological side, it interfaces with functional morphology, biogeography, molecular genetics, and systematics.  The direction of my research is both question-driven and opportunistic, as exemplified by three projects:

A description and analysis of a new Middle Triassic molluscan fauna by Waller & Stanley (2005) came about because of specimens sent to me for identification and dating by a geologist working on the evolution of Triassic coral reefs.  The fossil bivalves, from the Middle Triassic of Nevada, were found in association with the earliest development of colonial scleractinian corals known in the Americas.  Because the fossils presented a number of contradictions to previously published studies,  I visited the New Pass Range to examine stratigraphy in the canyon from which they were collected  and to collect more material there and in adjacent canyons.  What was originally a small identification project became a monographic study of a unique marine fauna.  Its uniqueness derives from the fact that the super-continent of Pangaea was still being formed in the Mesozoic Era by the collision of micro-continents with its western margin.  In the process,  much of the geologic  record of Triassic marine life living along the western shores of Pangaea was obliterated by subduction and mountain-building.  It turns out that this Nevada site provides a rare view of a marine fauna that lived on the continental shelf 235 million years ago. It is unlike any previously described Triassic fauna and provides new insight to the diversification and paleobiogeography of mollusks during the early recovery phase following the end-Permian mass extinction. 

A second project, which has occupied much of my research career, is a continuing  analysis of the evolution of scallops beginning with their origin in the Paleozoic Era 375 million years ago and extending to the diversification of modern scallops of the present day oceans.  The work has involved detailed study of the anatomy and shells of living scallops. including underwater studies of scallop behavior, as well as the collecting and examination of fossil scallops from Paleozoic, Mesozoic, and Cenozoic strata.  Resulting evolutionary trees with dated branching points have proven to be of great interest to molecular geneticists, who have provided independent tests of phylogenetic hypotheses, to fisheries biologist interested in commercial scallop stocks, and to geologists interested in the biostratigraphic and paleogeographic significance of morphological changes in scallop shells.

A third project, which is my current research focus, is an analysis of morphological changes through time and space of the Neogene fossil scallops of the northern Dominican Republic.  This study is part of a broad interdisciplinary project begun in the 1980s by a team of Swiss and French paleontologists and geologists, who measured stratigraphic sections in this area in detail and made meticulously documented collections of both micro- and macroinvertebrate fossils.  Because scallops are one of the most abundant macroinvertebrates present, this project  should provide new insights to the tempo and mode of evolution in this part of the Caribbean and to changing biogeographic patterns associated with the closure of seaways between the Atlantic and Pacific.


  • Fellow, American Association for the Advancement of Science.
  • Gilbert Harris Award, presented by the Paleontological Research Institution in recognition of excellence in systematic paleontology.

Selected Publications

1969.  WALLER, T.R.  The evolution of the Argopecten gibbus stock (Mollusca: Bivalvia), with emphasis on the Tertiary and Quaternary species of eastern North America.  Journal of Paleontology, Memoir 3 (vol. 43, suppl. to No. 5):v + 125p., 12 figs., 8 pls., 43 tables. 

1972a.  WALLER, T.R.  The Pectinidae (Mollusca: Bivalvia) of Eniwetok Atoll, Marshall Islands.  The Veliger, 14(3): 221-264, 22 figs., 8 pls., 13 tables. 

1972b.  WALLER, T.R.  The functional significance of some shell microstructures in the Pectinacea (Mollusca: Bivalvia).  Proceedings,  International Geological Congress, 24th Session, Montreal, Canada, Sect. 7, Paleontology: 48-56, 3 figs., 1 table. 

1973.  WALLER, T.R.  The habits and habitats of some Bermudian marine molluscs.  The Nautilus, 87(2): 31-52, 2 figs., 2 pls., 2 tables. 

1976.  WALLER, T.R.  The behavior and tentacle morphology of pteriomorphian bivalves: a motion-picture study.  Bulletin of the  American Malacological Union for 1975: 7-13, 2 figs., 1 table. 

1978.  WALLER, T.R.  Morphology, morphoclines and a new classification of the Pteriomorphia (Mollusca: Bivalvia).  Philosophical Transactions of the Royal Society of London, B, 284: 345-365, 2 figs., 2 tables. 

1980.  WALLER, T.R.  Scanning electron microscopy of shell and mantle in the order Arcoida (Mollusca: Bivalvia).  Smithsonian Contributions to Zoology, 313: iii + 58p., 46 figs., 1 table. 
1981.  WALLER, T.R.  Functional morphology and development of veliger larvae of the European oyster, Ostrea edulis Linné.  Smithsonian Contributions to Zoology, 328: iii + 70p., 152 figs., 1 table. 

1982.  WALLER, T.R., and I.G. MACINTYRE.  Larval settlement behavior and shell morphology of Malleus candeanus (d'Orbigny) (Mollusca: Bivalvia).  pp. 489-497, 4 figs., 2 tables.  In K. RÜTZLER and I.G. MACINTYRE, The Atlantic Barrier Reef ecosystem at Carrie Bow Cay, Belize, vol. 1: Structure and communities.  Smithsonian Contributions to the Marine Sciences, 12. 

1984.  WALLER, T.R.  The ctenolium of scallop shells: functional morphology and evolution of a key family-level character in the Pectinacea (Mollusca: Bivalvia).  Malacologia, 25(1): 203-219, 5 figs., 1 table. 

1986.  WALLER, T.R.  A new genus and species of scallop (Bivalvia: Pectinidae) from off Somalia, and the definition of a new tribe Decatopectinini.  The Nautilus, 100(2): 39-46, 2 figs. 

1988.  WARD, L.W., and T.R. WALLER.  A new species of Pulvinites (Mollusca: Bivalvia) from the Upper Paleocene Paspotansa Member of the Aquia Formation in Virginia.  Journal of  Paleontology, 62(1): 51-55, 4 figs. 

1990.  WALLER, T.R.  The evolution of ligament systems in the Bivalvia.  pp. 49-71, 2 figs., 2 pls.  In. B. Morton (editor), The Bivalvia -- Proceedings of a Memorial Symposium in Honour of Sir Charles Maurice Yonge, Edinburgh, 1986.  Hong Kong University Press, Hong Kong. 

1991.  WALLER, T.R.  Evolutionary relationships among commercial scallops.  pp. 1-73, 11 figs., 8 pls., 1 table.  In S.E. SHUMWAY (editor), Scallops: biology, ecology and aquaculture.  Elsevier, Amsterdam. 

1991.  BERKMAN, P.A., T.R. WALLER, and S.P. ALEXANDER.  Unprotected larval development in the Antarctic scallop Adamussium colbecki (Mollusca: Bivalvia: Pectinidae).  Antarctic Science, 3(2): 151-157, 3 figs., 1 table.   

1992.  WALLER, T.R., and L. MARINCOVICH, JR.  New species of Camptochlamys and Chlamys (Mollusca: Bivalvia: Pectinidae) from near the Cretaceous/Tertiary boundary at Ocean Point, North Slope, Alaska.  Journal of Paleontology, 66(2): 215-227, 2 figs., 2 pls. 
1993.  WALLER, T. R.  The evolution of "Chlamys" (Mollusca: Bivalvia: Pectinidae) in the tropical Western Atlantic and Eastern Pacific.  American Malacological Bulletin, 10(2): 195-249, 14 figs. (including 7 plates), 2 tables. 

1995.  WALLER, T.R.  The misidentified holotype of Argopecten circularis (Bivalvia: Pectinidae).  The Veliger, 38(4): 298-303, 14 figs. 

1996.  WALLER, T.R.  Bridging the gap between the eastern Atlantic and eastern Pacific: a new species of Crassadoma (Bivalvia: Pectinidae) in the Pliocene of Florida.  Journal of Paleontology, 70(6): 941-946, 2 figs.

1998.  WALLER, T.R.  Origin of the molluscan class Bivalvia and a phylogeny of major groups.  pp. 1-45, 5 figs. In P.A. Johnston and J.W Haggart (Editors), with a Foreward by Stephen Jay Gould, Bivalves: An eon of evolution.  Paleobiological Studies honoring Norman D. Newell.  University of Calgary Press. 

2001.  WALLER, T.R.  Dhondtichlamys, a new name for Microchlamys Sobetski, 1977 (Mollusca: Bivalvia: Pectinidae), preoccupied by Microchlamys Cockerell, 1911 (Rhizopoda: Arcellinida).  Proceedings of the Biological Society of Washington, 114(4): 858-860. 

2005.  WALLER, T.R., & G.D. Stanley, Jr.  Middle Triassic pteriomorphian Bivalvia (Mollusca) from the New Pass Range, west-central Nevada: systematics, biostratigraphy, paleoecology, and paleobiogeography.  Journal of Paleontology Memoir 61, supplement to Journal of Paleontology, 79(1): ii + 64 pp.  

2006a.  WALLER, T.R.  New phylogenies of the Pectinidae (Mollusca: Bivalvia): Reconciling morphological and molecular approaches.  Pp. 1-44, in S.E. Shumway & G.J. Parsons (Eds.), Scallops: Biology, Ecology and Aquaculture.  Developments in Aquaculture and Fisheries Science, 35, xxxix + 1,460 pp.  Elsevier B.V., London. 

2006b.  WALLER, T.R.  Phylogeny of families in the Pectinoidea (Mollusca: Bivalvia): importance of the fossil record.  Zoological Journal of the Linnean Society, 148(3): 313-342. 

2007 (in press).  WALLER, T.R.  The evolutionary and biogeographic origins of the endemic Pectinidae (Mollusca: Bivalvia) of the Galápagos Islands.  Journal of Paleontology.