Jon M. Mallatt
School of Biological Sciences,
and Basic Medical Sciences
Washington State University
Pullman, WA U.S.A. 99164-4236
As a scientist, I study the origin of the major animal groups, vertebrates and invertebrates, from the perspective of molecular phylogeny and evolutionary morphology. It is exciting to reconstruct events that occurred up to three-quarters of a billion years ago. For years, I have investigated the origin of vertebrates and the origin of jaws in vertebrates based on their anatomy. Since the middle 1990’s, however, I have used molecular phylogeny to study animal interrelationships. Whereas many laboratories use 18S ribosomal RNA gene sequences to determine relationships among major groups of organisms, we are one of the first labs to use the larger, 28S ribosomal rRNA gene for studying the phylogeny of animals. Actually, we combine 18S and 28S sequences, and have found that these combined sequences produce more accurate phylogenies than do 18S sequences alone. Specifically, we found that 28S+18S sequences uphold the division of protostome invertebrates into moulting and non-moulting groups (Ecdysozoa and Lophotrochozoa, respectively); that the jawless fishes, lampreys and hagfishes, are likely interrelated as cyclostomes; and, in an investigation of the relations of elasmobranchs, we found that skates and rays did not arise from a group of sharks called squaliforms, as is commonly believed. My next project will use 28S and18S sequences to investigate sub-groups of the great group of moulting animals, especially arthropods.
The figure below shows the relationships of major animal groups based on their 28S and 18S ribosomal RNA sequences, as we calculated using maximum parsimony and other methods. Most of the gene sequences were generated in our lab.
The figure below shows my reconstruction of the head
of the ancestor of all vertebrates, which lived about half
a billion years ago.
Jon Mallatt: Selected Publications:
1. Mallatt, J., and C. Winchell. Testing the new animal phylogeny: first use of combined large-subunit and small-subunit rRNA gene sequences to classify the protostomes. Manuscript submitted to Molecular Biology and Evolution.
2. Winchell, C., J. Sullivan, C. Cameron, B. Swalla, and J. Mallatt. In Press. Evaluating hypotheses of deuterostome evolution with new LSU and SSU ribosomal DNA phylogenies. Molecular Biology and Evolution.
3. Mallatt, J., J. Sullivan, and C. Winchell. 2001. The relationships of lampreys to hagfishes: a spectral analysis of ribosomal DNA sequences. P. Ahlberg, editor. Major Events in Early Vertebrate Evolution: Palaeontology, phylogeny, and Development. Taylor and Francis Ltd., London.
4. Marieb, E., and J. Mallatt. 2001. Human Anatomy. Third Edition. Addison Wesley Longman.
5. Mallatt, J., and J. Sullivan. 1998. 28S and 18S ribosomal DNA sequences support the monophyly of lampreys and hagfishes. Molecular Biology and Evolution 15:1706-1718.
6. Mallatt, J. 1997/8. Crossing a major morphological boundary: the origin of jaws in vertebrates. Zoology, Applied and Complex Systems (ZACS) 100:128-140.
7. Mallatt, J. 1997. Shark pharyngeal muscles and early vertebrate evolution. Acta Zoologica, Stockholm 78:279-294.
8. Mallatt, J. 1996. Ventilation and the origin of jawed vertebrates: a new mouth. Zoological Journal of the Linnean Society 117:329-404.
9. Mallatt, J. 1986. Reconstructing the life cycle and the feeding of ancestral vertebrates. In: Evolutionary Biology of Primitive Fishes. R. Foreman, A. Gorbman, J. Dodd, and R. Olsson, editors. Plenum Publishing Corp. New York. pp. 59-68.
10. Mallatt, J., and C. Paulsen. 1986. Gill ultrastructure of the Pacific hagfish Eptatretus stouti. American Journal of Anatomy 177:243-269.
11. Mallatt, J. 1985. Fish gill structural changes induced by toxicants and other irritants: a statistical review. Canadian Journal of Fisheries and Aquatic Sciences 42:630-648.
12. Mallatt, J. 1984. Early vertebrate evolution: pharyngeal structure and the origin of gnathostomes. J. Zool., London. 204:169-183.
13. Mallatt, J. 1984. Feeding ecology of the earliest vertebrates. Zoological Journal of the Linnean Society 82:261-272.
Papers in Manuscript:
1. The fossil sister group of craniates: predicted and found. J. Mallatt and J. Chen. To Journal of Morphology.
2. Phylogeny of the elasmobranchs: evaluating morphology-based hypotheses with LSU and SSU ribosomal RNA gene sequences. C. Winchell, A. Martin, J. Mallatt. To Systematic Biology.
More Professional Information:
Education: B.S. 9/70-6/74 University of Wisconsin, Madison, Dept. Zoology
Ph.D. 9/74-12/79 University of Chicago, Dept. Anatomy
Associate Professor, Departments of Zoology (Biological Sciences) and Basic Medical Sciences, Washington State University, 8/84-present
Affiliate Associate Professor, University of Washington, Department of Biological Structure, 3/84-present
International Society of Vertebrate Morphologists
American Association for the Advancement of Science
Human anatomy to health professionals, including Histology and Gross Anatomy of the Trunk to WWAMI medical students of the University of Washington School of Medicine, 1980 to present.
Site last updated, August 2001.