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Modern vertebrate tracks from Lake Manyara, Tanzania and their paleobiological implications

Published online by Cambridge University Press:  08 February 2016

Andrew S. Cohen ,
James Halfpenny ,
Martin Lockley  and
Ellinor Michel
Andrew S. Cohen
Affiliation:
Department of Geosciences, University of Arizona, Tucson, Arizona 85721
James Halfpenny
Affiliation:
Institute of Arctic and Alpine Research, University of Colorado, Boulder, Colorado 80309
Martin Lockley
Affiliation:
Department of Geology, University of Colorado at Denver, Denver, Colorado 80204
Ellinor Michel
Affiliation:
Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona 85721
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Abstract

We studied mammal and bird track formation at the northern edge of Lake Manyara, Tanzania, to develop models for interpreting fossil tracks and trackways. Lake Manyara is a closed-basin, alkaline lake in the East African Rift System. The area has a high vertebrate diversity, allowing us to investigate tracks in an environment similar to that of many ancient track-bearing sequences. Three study sites, two on mud flats adjacent to the lake margin and a third on a delta floodplain, provided contrasting environments in which to assess the types of biological data that can potentially be extracted from fossil trackways.

Our censuses of mammals and their tracks revealed that most species that occur within the study area leave a track record, and that common species leave abundant tracks, although numbers of trackways are not proportional to numbers of individuals. Logarithmic increases in track sampling area yield a linear increase in the proportion of both the medium and large-sized local mammals represented in a track record. Transect vs. area mapping methods produced different censusing results, probably because of differences in monitoring periods and areal coverage.

We developed a model of expected track production rates that incorporates activity budget and stride length data in addition to abundance data. By using these additional variables in a study of diurnal birds, we obtained a much better estimator relating track abundance to trackmaker abundance than that provided by census data alone. Proportions of different types of tracks predicted by the model differ significantly from the observed proportions, almost certainly because of microenvironmental differences between the censusing and track counting localities. Censuses of fossil tracks will be biased toward greater numbers of depositional-environment generalists and away from habitat-specific species.

Trackways of migratory animals were dominantly shoreline-parallel, whereas trackways of sedentary species were more variable. A strong shoreline-parallel environmental zonation at the Alkaline Flats site exerted an influence on trackmaker distribution patterns, initial track formation, and track preservation. Variations in habitat usage by different species, as well as species abundance and directionality of movement, were all important in determining the number of preservable tracks a species produced within a given environmental zone.

Fossil trackways are time-averaged, although over entirely different temporal scales than are bones. Unlike bones, tracks are not space-averaged. Therefore, wherever possible, fossil track and bone studies should be used to complement each other, as they provide fundamentally different pictures of paleocommunities. Tracks provide “snapshot” views of localized assemblages of organisms useful in reconstructing autecological relationships, whereas bones yield a broader image of a local fauna in which seasonal and microenvironmental variation are more commonly smoothed out.

Type
Articles
Information
Paleobiology , Volume 19 , Issue 4 , Fall 1993 , pp. 433 - 458
Copyright
Copyright © The Paleontological Society 

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References

Literature Cited

Behrensmeyer, A. K., Western, D., and Dechant Boaz, D. E. 1979. New perspectives in vertebrate paleoecology from a recent bone assemblage. Paleobiology 5:12–21.CrossRefGoogle Scholar
Cohen, A. S., Lockley, M., Halfpenny, J., and Michel, A. E. 1991. Modern vertebrate track taphonomy at Lake Manyara, Tanzania. Palaios 6:371–389.CrossRefGoogle Scholar
Farlow, J. O. 1981. Estimates of dinosaur speeds from a new trackway site in Texas. Nature 294:747–748.CrossRefGoogle Scholar
Greenway, P. J., and Vesey-Fitzgerald, D. F. 1969. The vegetation of Lake Manyara National Park, Tanzania. Journal of Ecology 57:127–149.CrossRefGoogle Scholar
Halfpenny, J. C. 1986. A field guide to mammal tracking in North America. Johnson Books, Boulder, Colo.Google Scholar
Laporte, L. F., and Behrensmeyer, A. K. 1980. Tracks and substrate reworking by terrestrial vertebrates in Quaternary sediments of Kenya. Journal of Sedimentary Petrology 50:1337–1346.Google Scholar
Leakey, M. D., and Hay, R. L. 1979. Pliocene footprints in the Laetoli Beds at Laetoli, northern Tanzania. Nature 278:317–323.CrossRefGoogle Scholar
Leakey, M. D., Hay, R. L., Curtis, G. H., Drake, R. E., Jackes, M. K., and White, T. D. 1976. Fossil hominids from the Laetoli Beds. Nature 262:460–466.CrossRefGoogle Scholar
Leonardi, G. 1981. Ichnological data on the rarity of young in North East Brazil dinosaur populations. Anais Acad. Brasil. Ciencias 53:345–346.Google Scholar
Lockley, M. G. 1991a. Tracking dinosaurs: a new look at an ancient world. Cambridge University Press, New York.Google Scholar
Lockley, M. G. 1991b. The Moab megatracksite: a preliminary description and discussion of millions of Middle Jurassic tracks in eastern Utah. Pp. 59–65In Averett, W. R., ed. Dinosaur quarries and tracksite tour: western Colorado and eastern Utah. Grand Junction Geological Society, Colorado.Google Scholar
Lockley, M. G. 1992. Vertebrate tracks and sequence stratigraphy: an unusual combination of disciplines or a natural marriage? Pp. 25–27In Warme, J. E., Weimer, P., Sonnenberg, S. A., Basse, R. and Posamentier, H. W., eds. Applied sequence stratigraphy—a symposium. Colorado School of Mines, Golden, Colo.Google Scholar
Lockley, M. G., Hunt, A., Holbrook, J., Matsukawa, M., and Meyer, C. 1992a. The dinosaur freeway: a preliminary report on the Cretaecous megatracksite, Dakota Group, Rocky Mountain Front Range, and High Plains, Colorado, Oklahoma and New Mexico. Pp. 39–54In Flores, R. M., ed. Mesozoic of the western interior field guidebook Society of Economic Paleontologists and Mineralogists-Rocky Mountains Section 1992 Theme Meeting, Fort Collins, Colo.Google Scholar
Lockley, M. G., Conrad, K., Paquette, M., and Hamblin, A. 1992b. Late Triassic vertebrate tracks in the Dinosaur National Monument area. Pp. 383–391In Wilson, J. R., ed. Field guide to geological excursions in Utah and adjacent areas of Nevada, Idaho, and Wyoming. Utah Geological Survey Miscellaneous Publication 92–3.Google Scholar
Lockley, M. G., Conrad, K., Paquette, M., and Farlow, J. O. 1992c. Distribution and significance of Mesozoic vertebrate trace fossils in Dinosaur National Monument. Pp. 74–85In Plumb, G. E. and Harlow, H. J., eds. University of Wyoming National Park Service Research Center 16th Annual Report.CrossRefGoogle Scholar
Schult, M. F., and Farlow, J. O. 1992. Vertebrate trace fossils. Pp. 34–63In Maples, C. G. and West, R., eds. Trace fossils: short courses in paleontology, no. 5. Paleontological Society, Lawrence, Kans.Google Scholar
Scrivner, P., and Bottjer, D. 1986. Neogene avian and mammalian tracks from Death Valley National Monument, California: their context, classification and preservation. Palaeogeography, Palaeoclimatology, Palaeoecology 57:285–331.CrossRefGoogle Scholar
Thulborn, T. 1990. Dinosaur tracks. Chapman and Hall, New York.CrossRefGoogle Scholar