Fossil hunting is both a profession and a hobby. It has led to an unraveling of Earth’s Phanerozoic history, the time of “visible” life that stretches back over a half billion years. Because the fossil record contains the bias of erosion, destruction, and burial of rocks, a bias that makes the record incomplete, paleontologists and hobbyists do not have a perfect retelling of life. Not all ancient life has been preserved, and among the fossil lineages, there are gaps either because nothing in the time period was fossilized or because those individuals that were once preserved were later destroyed.
Enter Brachiospongia. Now sponges are the simplest of animals. No nervous system. No tissues. Just a couple of layers of specialized cells all somehow acting in unison. No means of locomotion. Sponges just sit filtering water for microscopic food; they are sessile creatures, encrusting whatever hard material is available or standing solitary. Some are very colorful—though they usually lose their color quickly when they are removed from their marine environment.
Fossils of Brachiospongia digitata and B. turberculata James might be mistaken for a starfish. There is a central disk from which fingerlike lobes protrude. Both species are Ordovician in age; that puts them way back in life history, sometime between 485.4 and 443.8 million years ago. At that time Ohio, Kentucky, Tennessee, and Ontario all lay on or near the equator, and all were covered by tropical waters. This was Brachiospongia’s environment.
So, there is a fossil record of Brachiospongia in North America. Its fossils are found nowhere else in the world except in Scotland. Scotland? That’s across the Atlantic, isn’t it? Not then. There was no Atlantic. Since the Ordovician, the place has moved. At that time it was either attached to or very near North America.
Geologists are used to seeing widely separated fossils of a genus or species because they know that sea-floor spreading has moved the continents—and is still moving them. All places have in their long histories moved. We see the effects of movement today in earthquakes, such as those that occur along the San Andreas Fault or those that devastate places like Italy. Fossiliferous rocks move with the moving seafloors and neighboring continents. Thus, Brachiospongia fossils of North America and Scotland were at one time neighbors whose marine residences, now preserved in rock, moved.
Here’s a human analog: Birds of a feather flock together. Wait! That’s not human, is it? Okay, people of like minds flock together, often becoming sessile in their thinking. Changes to underlying ideologies are often as slow as sea-floor spreading (in Iceland, it’s a centimeter per year) interrupted by convulsive earthquake-like revolutions of thought that become locked in place until the next convulsion. But the general trend is slow and inexorable, and the process is a repeating one. We’ve established the “continents” of thought, and most ideologies are fossilized in those “rocks.” True, we might find some separated by continent or country, but their origins lie in the deep human past. And just as Brachiospongia might be mistaken for a starfish fossil, some ideologies might be mistaken for superficially similar forms.
By the end of the Ordovician Period, most, if not all the modern phyla (the body types or forms) had been established. And long ago, in human terms, the ideologies some consider to be “new” were established and even fossilized. But the Orodovician is known for another event, an extinction. Brachiospongia didn’t survive. Its dead remnants moved passively with spreading seafloors. Because of the time involved, those fossils are widely separated, but they are still related, and they were of singular origin.
How have the variations of your fossilized ideology spread across the planet? How has it been mistaken for something it was not? What extinction processes might be at work to bury it in the rocks of human history?
Enter Brachiospongia. Now sponges are the simplest of animals. No nervous system. No tissues. Just a couple of layers of specialized cells all somehow acting in unison. No means of locomotion. Sponges just sit filtering water for microscopic food; they are sessile creatures, encrusting whatever hard material is available or standing solitary. Some are very colorful—though they usually lose their color quickly when they are removed from their marine environment.
Fossils of Brachiospongia digitata and B. turberculata James might be mistaken for a starfish. There is a central disk from which fingerlike lobes protrude. Both species are Ordovician in age; that puts them way back in life history, sometime between 485.4 and 443.8 million years ago. At that time Ohio, Kentucky, Tennessee, and Ontario all lay on or near the equator, and all were covered by tropical waters. This was Brachiospongia’s environment.
So, there is a fossil record of Brachiospongia in North America. Its fossils are found nowhere else in the world except in Scotland. Scotland? That’s across the Atlantic, isn’t it? Not then. There was no Atlantic. Since the Ordovician, the place has moved. At that time it was either attached to or very near North America.
Geologists are used to seeing widely separated fossils of a genus or species because they know that sea-floor spreading has moved the continents—and is still moving them. All places have in their long histories moved. We see the effects of movement today in earthquakes, such as those that occur along the San Andreas Fault or those that devastate places like Italy. Fossiliferous rocks move with the moving seafloors and neighboring continents. Thus, Brachiospongia fossils of North America and Scotland were at one time neighbors whose marine residences, now preserved in rock, moved.
Here’s a human analog: Birds of a feather flock together. Wait! That’s not human, is it? Okay, people of like minds flock together, often becoming sessile in their thinking. Changes to underlying ideologies are often as slow as sea-floor spreading (in Iceland, it’s a centimeter per year) interrupted by convulsive earthquake-like revolutions of thought that become locked in place until the next convulsion. But the general trend is slow and inexorable, and the process is a repeating one. We’ve established the “continents” of thought, and most ideologies are fossilized in those “rocks.” True, we might find some separated by continent or country, but their origins lie in the deep human past. And just as Brachiospongia might be mistaken for a starfish fossil, some ideologies might be mistaken for superficially similar forms.
By the end of the Ordovician Period, most, if not all the modern phyla (the body types or forms) had been established. And long ago, in human terms, the ideologies some consider to be “new” were established and even fossilized. But the Orodovician is known for another event, an extinction. Brachiospongia didn’t survive. Its dead remnants moved passively with spreading seafloors. Because of the time involved, those fossils are widely separated, but they are still related, and they were of singular origin.
How have the variations of your fossilized ideology spread across the planet? How has it been mistaken for something it was not? What extinction processes might be at work to bury it in the rocks of human history?
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