[...]... creatures of the Cambrian stick out like a sore thumb There does seem to be a suddenness about them, one not explicable on the basis of gradual evolution Today we understand that the Cambrian fauna were preceded by a strange and motley collection of often symmetrical soft-bodied forms These are the Ediacarans, eponymous subheroes of the Australian outcrop where the first such fossils were found The Ediacarans’... the Ediacaran biota They have also been called the Ediacaran fauna, but because the term fauna implies animals, and paleontologists are not confident that all of the Ediacaran forms were animals; prudence requires the less specific term Ediacaran biota, or simply Ediacarans Diverse communities of multicellular creatures appear with the first members of the Ediacaran biota My recent find in Mexico of. .. time (the bang hypothesis), or do they have long histories that happened to leave virtually no fossil record (the whimper hypothesis)? Some authors advocate the whimper,20 others the bang.21 The whimperers are forced to admit that there is a major evolutionary radiation at the beginning of the Cambrian, although they try to keep the perceived number of new phyla appearing at this time to a minimum The. .. meaning that they represented an alien body form no longer represented in the world.30 Later work has demonstrated that these forms survived well into the Cambrian However, the newer research has not settled the question of what these forms were, or how they fed Many mysteries remain The solutions may well involve a fuller understanding of the phenomenon of symbiogenesis The question of the origin of life... tossed aside the anomalocarid specimens as if they were worthless matrix 14 • The Sand Menagerie Medusoids are both the youngest and the oldest of the Ediacarans They are also the most common, and were the first to be noted by scientists, although from the start there were questions about the biological nature of these structures In 1877 E Hill and T G Bonney reported “curious arrangements of concentric... theory, the concept that these medusoids were actually bowl-shaped solar collectors Many Ediacaran medusoids are three-dimensional fossils filled with fine sediment The Mexican specimen (figure 2.1) is one of these, as is the Irish find How did sand get inside these medusoids? Do they represent a sand casting of the impression in the sediment where a soft body once was, or was the sand part of the creature... the University of California at Santa Barbara, I already appreciated the appeal of Ediacaran paleontology In fact, I embarked on a study of the Ediacaran fossils for my postgraduate work These fossils are still as mysterious as when Tribrachidium was illustrated by the Time-Life Nature Library in the 1960s With the Ediacaran fossils, or Ediacarans, paleontologists work a complex interface between the. .. may have been, before animals proper, the first organisms to evolve heads Which, as in the knowledge gained from the Tree of Good and Evil in the redolent Garden of Eden, may have spelled the beginning of the end xii • Foreword For despite the scene drawn by some evolutionists of a planet of pure contingency, devoid of direction, certain patterns do have a way of cropping up again and again in evolution... concentration of a suite of sense organs (some, perhaps, like the magnetodetecting abilities of some bacteria, alien to us) in the head, McMenamin intuits, may well have been an Ediacaran foreshadowing of the headstrong human theme The consequences of this, as of Eve’s bite, were severe With eyes animal predecessors began to sense who was tasty, who was vulnerable—and to eat them The evil empire of carnophagy... perished from lack of protection Sashimi, it seemed, was everywhere The arms races of predators and prey, the coevolutionary gamesmanship of becoming faster, smarter, and more deadly, on the one hand, and still faster, outsmarting, and quicker to hide or get away, on the other, came into being The continents shifted Ediacarans suffered The innocence, or at least the languor, of the primeval Garden was lost . collection of often symmetrical soft-bodied forms. These are the Ediacarans, eponymous subheroes of the Australian outcrop where the first such fossils were found. The Ediacarans’ global garden, ” more. case of indi- gestion, these larger cells benefitted from the metabolic independence of the preplants now dwelling Jonah-like inside them. McMenamin’s Garden of Ediacara hypothesis explains the. animals proper, the first organisms to evolve heads. Which, as in the knowledge gained from the Tree of Good and Evil in the redolent Garden of Eden, may have spelled the beginning of the end. Foreword