\u201cYou\u2019re in the desert walking around on mountains, but at the same time you feel like you\u2019re scuba diving,\u201d Smith says.<\/p>\n
To the untrained eye, the rocks don\u2019t look like much. But under a microscope, a thin cross section swarms with shapes resembling segmented donuts and dark, sinuous veins. This abstract motif is the fossilized vestige of the archaeocyaths, a diverse group of filter-feeding sponges.<\/p>\n
![\"A](\"https:\/\/hakaimagazine.com\/wp-content\/uploads\/2021-10-20-14.56.28-900x1350.jpg\")
Up close, the rocks in the Nevada desert bristle with the fossilized remains of ancient life. Photo by Mary Lonsdale<\/p><\/div>\n
Archaeocyaths were the world\u2019s first reef builders. Common just after the Cambrian explosion, archaeocyaths predate reef-building corals by 40 million years. Like their modern equivalents, archaeocyaths grew on the calcified skeletons of their forebearers, adding their own tubular and branching bodies to build immense structures over generations.<\/p>\n
These thriving ecosystems were relatively short lived. Globally, archaeocyathan reefs only persisted for around 20 million years, a mere blip in oceanic history. It is a mystery why they went extinct, but the Gold Point reef, which offers one of the last known examples of these reef-building sponges, holds a clue.<\/p>\n
Fossilized archaeocyathan reefs have been found everywhere from Siberia to Morocco. But the reef high up in the mountains of southwestern Nevada is a particular boon to scientists\u2019 understanding of the volatile conditions after the Cambrian explosion. The fossilized reef is 70 meters thick in certain spots, says Sara Pruss, a paleontologist at Massachusetts\u2019 Smith College who was involved in the research. \u201cYou can look at the fine-scale changes through time because you get this big, thick period of deposition,\u201d she says. \u201cYou can actually see how the environment changes.\u201d<\/p>\n
Within the fossilized remains, Pruss and Smith have found evidence of an abrupt change in the climate<\/a>. By around 515 million years ago, a large slab of ancestral North America known as Laurentia had splintered from a southern supercontinent, spewing massive amounts of carbon into the atmosphere, which siphoned oxygen from the oceans and acidified the water in an event known as the archaeocyath extinction carbon isotope excursion.<\/p>\n This event, says Pruss, mirrors how the ocean\u2019s chemistry has changed today, though in a much more dramatic fashion: \u201cThere are so many commonalities between the archaeocyath extinction and the decline [of] modern coral reefs,\u201d says Pruss.<\/p>\n The detailed preservation of the Gold Point reef also paints a picture of what it would have looked like in its heyday.<\/p>\n The fossils encapsulate a spectrum of coastal habitats and archaeocyath species, from nearshore inhabitants that preferred the wave-battered shallows, to those that could only tolerate quiet deepwater enclaves. This breadth of archaeocyath lifestyles echoes modern-day coral diversity, says Pruss. \u201cIf you go to the Bahamas and snorkel around, you see the same [pattern] of different corals living in different places.\u201d<\/p>\n A fossilized archaeocyath as seen in Cambrian limestone unearthed in South Australia. Photo by The Natural History Museum\/Alamy Stock Photo<\/p><\/div>\n Yet while the Gold Point reef shares structural similarities with a modern coral-encrusted Caribbean key, David Cordie, a paleontologist at Wisconsin\u2019s Edgewood College, says it probably would not have made for great snorkeling. Nearshore and extremely shallow, these reefs would have been swamped by nutrients and sediment washing in from the coasts. \u201cIf you were to go back in time, it was probably murky, really shallow, with not nearly as much activity as you might expect in reef environments today,\u201d says Cordie, who was not involved in the new Gold Point research. \u201cSo maybe a little underwhelming by some peoples\u2019 standards.\u201d<\/p>\n However, if you could peer through the cloudy water, you would be greeted by an outlandish group of reef inhabitants. Spiny trilobites<\/a> scuttled along the seafloor, swerving around the featherlike arms of crinoids<\/a> and cactus-like stalks of chancelloriids<\/a>, an enigmatic group of sessile creatures encased in hundreds of star-shaped plates of armor. Other excavations nearby have yielded fossilized hyoliths, a bizarre group of ancient brachiopods<\/a> seemingly ripped from the pages of a science fiction novel. Some hyolith species propped themselves up on the seafloor using a pair of long spines and deployed a roving set of tentacles between their two shells\u2014the lower of which tapered off into a cone\u2014to gather planktonic prey. (Their fossils look a little like an ice cream cone with arms<\/a>.)<\/p>\n Like their modern analogs, archaeocyathan reefs \u201cwere hubs of diversity,\u201d says Smith. And the Gold Point reef\u2019s wonderful preservation\u2014which includes its complex three-dimensional structure\u2014has allowed the paleontologists to pinpoint the nooks and crannies where trilobites and early crinoids hunkered down between the stalks of sponges. \u201cYou really get a sense of the little houses that things lived in,\u201d says Mary Lonsdale, a graduate student pursuing her doctorate in Smith\u2019s lab at Johns Hopkins. \u201cIt\u2019s a thriving ecosystem.\u201d<\/p>\n \u201cReefs are incredible places of diversity, and they\u2019re quite beautiful,\u201d Lonsdale says. \u201cReef environments are just delightful in the modern world\u2014but they are equally as delightful in the past.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":" In the mountains of Esmeralda County, high above the parched expanse of southwestern Nevada and just across the border from California\u2019s Death Valley, Emmy Smith is on the hunt for the signs of what seems unimaginable in such a scorched <\/p>\n![\"A](\"https:\/\/hakaimagazine.com\/wp-content\/uploads\/body-archaecyanth-900x765.jpg\")