|The Paleobiology Laboratory|
The laboratory is directed by Dr. Joseph
Pachut, Associate Professor of Geology
BA 1972 - State University of New York, Oneonta
PhD 1977 - Michigan State University.
Specialties: Invertebrate Paleontology, Paleoecology, Bryozoology, Biometrics, and Evolution.
My research has focused on four different aspects of
the paleobiology of bryozoans: 1, paleogenetics; 2, patterns of colony development under
different paleoenvironmental conditions; 3, diversity, origination, and extinction
patterns; and 4, pattern, tempo, and mode of bryozoan evolution.
Paleogenetics studies have focused on determining evolutionary potentials of Paleozoic (570-230 million years ago) bryozoans under different inferred environmental conditions. This has been accomplished statistically by comparing levels of variation in morphology occurring within-colonies (essentially non-genetic in these clonal organisms) to that among colonies (partially-genetic) of fossil populations. Findings indicate that populations from stable environments are morphologically conservative but genetically more varied than populations from less stable settings. These results have spawned models relating where, under what types of conditions, and at what tempo evolutionary changes occur.
Environmental conditions appear to be capable of modifying bryozoan colonial developmental patterns. Different environments trigger significantly different patterns of development between populations of a single species. This indicates that these animals are very flexible developmentally and underscores the need for detailed analyses of population-level variation when defining species.
Studies of diversity, originations, extinctions, and the paleobiogeography of bryozoans provide a glimpse into the responses of an organic group to different biological and environmental factors through time. I have studied patterns during the Ordovician, Silurian, and Devonian Periods and have extended diversity studies through the Mesozoic Era to the Recent. A recently completed study applied cladistic analytical techniques to the study of the paleobiogeography of Ordovician and Silurian bryozoans. Results produced a different perspective on the extent of bryozoan provinces and biomes and on the factors that controlled bryozoan distributions during this interval of time. These results, coupled with those for other organic groups illustrate temporal fluctuations in lifes variety and may have an impact on current analyses of environmental effects on biodiversity.
I continue to analyze patterns and rates of morphological evolution within species of Peronopora, a genus of Upper Ordovician bryozoans. Initial results from cladistic analysis indicate that there are eight valid species and that previously names species were based primarily on stratigraphic occurrences. Thirty-one characteristics were required to identify, uniquely, all 211 specimens that were examined over a 9.1 million year time interval; only 3 to 8 characteristics had been used in earlier studies. The next step is to evaluate cladistic and stratigraphic gaps in the data, the tempo and mode of morphologic changes, and to calculate selection coefficients for characteristics very much like the calculations made by population biologist working on living organisms. A more detailed picture of the evolution of fossil organisms should emerge.
What are Bryozoans?
Metrarabdotos images are the property of the Smithsonian Institution.
Web Pages for Courses
Fundamentals of Earth History - G109
Principles of Paleontology - G304
Data Analysis in the Geosciences - G595
Current Research Summaries
associations among bryozoans through the Ordovician-Silurian transition
Identifying Larval Type in Fossil Bryozoans
Phylogeny, Systematics, and Biostratigraphy of the Ordovician bryozoan Genus Peronopora
Rates of Evolution and Selection Intensity in Species Transitions Within the Ordovician Bryozoan Genus Peronopora
Bryozoan Taxonomic Checklists
Ordovician-Silurian NEXUS File and Database
Listing of my Publications
Links to Museums & Reference Sources
Links for Teachers
Access Science - Science
Ask a Geologist
Becoming Human - Details on Human Origins (Arizona State)
Berkeley Web Lift - Search for Taxonomic Information
Dictionary of Scientific Quotations
Dive and Discover - Expeditions to the Seafloor
Evolution Forum for Teachers
Explorer - Resources for K-12 Math & Science
Genome Gateway - The Human Genome project
Geology Link - a public forum for geology (Houghton Mifflin)
Human Origins - Smithsonian Institution
To Know Ourselves - The Human Genome Project
Online Earth Science Journals
Paleobiology Links - Arranged by Taxonomic Groups & by Topics
Plate Tectonics Links
Resources for Involving Scientists in Education
SEPM's (The Society for Sedimentary Geology) K-12 Earth Science Page
Teachers Helping Teachers
U.S. Geological Survey Learning Web
The ENSI/SENSI Program - Teaching Evolution in the Classroom
Terra Server - Aerial Photographs
Virtual Field Trips
Virtual Geoscience Professor
Web Resources for Sedimentary Geologists
- Arranged by
Taxonomic Group and by Topic
Questions? Comments? New links? Send e-mail!
Questions or comments concerning this or other World Wide Web pages at the Department of Earth Sciences, IUPUI can be directed to Bob E. Hall.