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ACADEMIC INTERESTS

FIRST QUESTION

WHY STUDY FOSSILS IN THIS AGE OF MOLECULAR BIOLOGY?

Most of the animal and plant species that ever existed on earth are extinct, and the proof of their existence can only be found in fossils (if they are lucky enough to be preserved). Studies of these extinct organisms is a big challenge to science: we have to figure out what we can say about animals that once lived on earth based on very limited information available in fossils. So, paleontology is a very complex science, requiring the integration of broad knowledge from various branches of science.

Also, fossils are the only direct record of the evolution of life. Fossils preserve very limited information, yet the fossil record adds the fourth dimension, i.e., the time axis, to the data available to evolutionary biologists. Both paleontological and neontological data are important for evolutionary biologists, and integration of the two, rather than omission of one, should be the way the evolutionary biology proceeds.

LARGE TOPICS

UNDERSTANDING THE EVOLUTION OF THE SHAPES OF ANIMALS THROUGH FUNCTION, DEVELOPMENT, AND PHYLOGENY

The shapes of animals change in evolution. Such changes can be affected by how the ancestor was shaped (phylogenetic constraint), how a given structure develops during ontogeny (developmental constraint), and how a given structure interact with the physical environment (functional constraint). It is important to identify how each of these factors might have influenced the evolution of shape in vertebrates. I try to see the evolution of a marine reptilian group (ichthyosaurs) from these aspects. You can see an example in Motani (1999), which talks about the forefin (forelimb) of the group.

SECONDARY AQUATIC ADAPTATIONS

Many land vertebrates gave rise to secondarily aquatic descendants (for example, mesonychid mammals gave rise to whales). It is called secondary since all land vertebrates had an aquatic ancestor, sarcopterygian 'fish'. Carroll (1985) counted at least seven separate aquatic groups just within diapsids. Each group has its own way to deal with aquatic lives, but different groups often take similar approaches, probably because of the three constraints mentioned in the entry above.

ICHTHYOSAURS

My research has been mostly based on data from ichthyosaurs, an extinct group of marine reptiles that lived in the ocean when dinosaurs walked on land. These noble reptiles, although having had been derived from a lizard-looking ancestors, were fish-shaped. Isn't this amazing? Please visit my Ichthyosaur Page to learn more about these fascinating animals.

PHYLOGENY OF NON-MAMMALIAN VERTEBRATES, ESPECIALLY DIAPSIDS

Although I am widely interested in the phylogeny of vertebrates, the relationships among basal diapsids are the major interest at the moment. The base of the clade Sauria (the group containing living reptiles- birds) is still controversial: several groups, including ichthyosaurs, may or may not belong to the Sauria.

METHODOLOGICAL ISSUES

GEOLOGICAL DEFORMATION OF FOSSILS

The shape of fossils changes during preservation, although the extent of change may not be significant in many cases. In other cases, however, the deformation of fossil shapes is so extreme that it has led to misunderstanding. It is therefore important to make sure that you are not being deceived by such deformations. It is sometimes possible to restore the original shape under certain conditions, and paleontologists have been doing this since 1940s. Please see Motani (1997d) for details.

ALLOMETRIC EQUATION

Among the assumptions of the standard allometric equation is that the structures being compared start their developments simultaneously. However, some body parts, especially some bones, start their development much later than the other parts of the body. I am interested in what effect such a violation may have. Please see Motani and You (1998b) for details.

PHYLOGENETIC METHODOLOGIES

Reconstruction of phylogeny is a difficult task, and you cannot be too careful when running an analysis. There are many methodologies around based not only on different algorithm but also different philosophies. Morphological data are usually analyzed by parsimony, or the maximum parsimony method, and I want to be aware of any possible problem with this method that I use. One question I had was the incidental inclusion of the true ancestor in the data set (see abstract from 1995).

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