Read Online Wonderful Life: The Burgess Shale and the Nature of History by Stephen Jay Gould - Free Book Online
Authors: Stephen Jay Gould
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next to nothing about Precambrian life, for everything from the first prokaryotic cells to the Ediacara fauna is a story of soft-bodied creatures.
As its primary fascination, the Burgess Shale teaches us about an amazing difference between past and present life: with far fewer species, the Burgess Shale—one quarry in British Columbia, no longer than a city block—contains a disparity in anatomical design far exceeding the modern range throughout the world!
Perhaps the Burgess represents a rule about the past, not a special feature of life just after the Cambrian explosion? Perhaps all faunas of such exquisite preservation show a similar breadth of anatomical design? We can only resolve this question by studying temporal patterns of disparity as revealed in other Lagerstätten .
The basic answer is unambiguous: the broad anatomical disparity of the Burgess is an exclusive feature of the first explosion of multicellular life. No later Lagerstätten approach the Burgess in breadth of designs for life. Rather, proceeding forward from the Burgess, we can trace a rapid stabilization of the decimated survivors. The magnificently preserved, three-dimensional arthropods from the Upper Cambrian of Sweden (Müller, 1983; Müller and Walossek, 1984) may all be members of the crustacean line. (As a result of oddities in preservation, only tiny arthropods, less than two millimeters in length, have been recovered from this fauna, so we can’t really compare the disparity in these deposits with the story of larger-bodied Burgess forms.) The Lower Silurian Brandon Bridge fauna from Wisconsin, described by Mikulic, Briggs, and Kluessendorf (1985a and 1985b), contains (like the Burgess) all four major groups of arthropods. It also includes a few oddballs—some unclassifiable arthropods (including one creature with bizarre winglike extensions at its sides) and four wormlike animals, but none so peculiar as the great Burgess enigmas like Opabinia, Anomalocaris , or Wiwaxia .
The celebrated Devonian Hunsrückschiefer, so beautifully preserved that fine details emerge in X-ray photos of solid rock (Stürmer and Bergström, 1976 and 1978), contains one or two unclassifiable arthropods, including Mimetaster , a probable relative of Marrella , the most common animal in the Burgess. But life had already stabilized. The prolific Mazon Creek fauna, housed in concretions that legions of collectors have split by the millions over the past several decades, does include a bizarre wormlike animal known as the Tully Monster (officially honored in formal Latin doggerel as Tullimonstrum ). But the Burgess motor of invention had been shut off by then, and nearly all the beautiful fossils of Mazon Creek fit comfortably into modern phyla.
When we pass through the Permo-Triassic extinction and come to the most famous of all Lagerstätten —the Jurassic Solnhofen limestone of Germany—we gain enough evidence to state with confidence that the Burgess game is truly over. No fauna on earth has been better studied. Quarrymen and amateur collectors have been splitting these limestone blocks for more than a century. (These uniform, fine-grained stones are the mainstay of lithography, and have been used, almost exclusively, for all fine prints in this medium ever since the technique was invented at the end of the eighteenth century.) Many of the world’s most famous fossils come from these quarries, including all six specimens of Archaeopteryx , the first bird, preserved with feathers intact to the last barbule. But the Solnhofen contains nothing, not a single animal, falling outside well-known and well-documented taxonomic groups.
Clearly, the Burgess pattern of stunning disparity in anatomical design is not characteristic of well-preserved fossil faunas in general. Rather, good preservation has permitted us to identify a particular and immensely puzzling aspect of the Cambrian explosion and its immediate aftermath. In a geological moment near the beginning of
As its primary fascination, the Burgess Shale teaches us about an amazing difference between past and present life: with far fewer species, the Burgess Shale—one quarry in British Columbia, no longer than a city block—contains a disparity in anatomical design far exceeding the modern range throughout the world!
Perhaps the Burgess represents a rule about the past, not a special feature of life just after the Cambrian explosion? Perhaps all faunas of such exquisite preservation show a similar breadth of anatomical design? We can only resolve this question by studying temporal patterns of disparity as revealed in other Lagerstätten .
The basic answer is unambiguous: the broad anatomical disparity of the Burgess is an exclusive feature of the first explosion of multicellular life. No later Lagerstätten approach the Burgess in breadth of designs for life. Rather, proceeding forward from the Burgess, we can trace a rapid stabilization of the decimated survivors. The magnificently preserved, three-dimensional arthropods from the Upper Cambrian of Sweden (Müller, 1983; Müller and Walossek, 1984) may all be members of the crustacean line. (As a result of oddities in preservation, only tiny arthropods, less than two millimeters in length, have been recovered from this fauna, so we can’t really compare the disparity in these deposits with the story of larger-bodied Burgess forms.) The Lower Silurian Brandon Bridge fauna from Wisconsin, described by Mikulic, Briggs, and Kluessendorf (1985a and 1985b), contains (like the Burgess) all four major groups of arthropods. It also includes a few oddballs—some unclassifiable arthropods (including one creature with bizarre winglike extensions at its sides) and four wormlike animals, but none so peculiar as the great Burgess enigmas like Opabinia, Anomalocaris , or Wiwaxia .
The celebrated Devonian Hunsrückschiefer, so beautifully preserved that fine details emerge in X-ray photos of solid rock (Stürmer and Bergström, 1976 and 1978), contains one or two unclassifiable arthropods, including Mimetaster , a probable relative of Marrella , the most common animal in the Burgess. But life had already stabilized. The prolific Mazon Creek fauna, housed in concretions that legions of collectors have split by the millions over the past several decades, does include a bizarre wormlike animal known as the Tully Monster (officially honored in formal Latin doggerel as Tullimonstrum ). But the Burgess motor of invention had been shut off by then, and nearly all the beautiful fossils of Mazon Creek fit comfortably into modern phyla.
When we pass through the Permo-Triassic extinction and come to the most famous of all Lagerstätten —the Jurassic Solnhofen limestone of Germany—we gain enough evidence to state with confidence that the Burgess game is truly over. No fauna on earth has been better studied. Quarrymen and amateur collectors have been splitting these limestone blocks for more than a century. (These uniform, fine-grained stones are the mainstay of lithography, and have been used, almost exclusively, for all fine prints in this medium ever since the technique was invented at the end of the eighteenth century.) Many of the world’s most famous fossils come from these quarries, including all six specimens of Archaeopteryx , the first bird, preserved with feathers intact to the last barbule. But the Solnhofen contains nothing, not a single animal, falling outside well-known and well-documented taxonomic groups.
Clearly, the Burgess pattern of stunning disparity in anatomical design is not characteristic of well-preserved fossil faunas in general. Rather, good preservation has permitted us to identify a particular and immensely puzzling aspect of the Cambrian explosion and its immediate aftermath. In a geological moment near the beginning of
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