Tuesday, October 31, 2006

Mongolian Stamps

Here are some Mongolian stamp sheets I picked up last summer. Click on each image to enlarge.

Those are Triceratops? Quite a wacky combination of dinos.

Cave Bear Claw Marks

The bear that left a 3-foot-long claw mark in an Ice Age clay bank was the largest bear species ever to walk the Earth, about 6 feet tall at the shoulder and capable of moving its 1,800 pounds up to 45 mph in a snarling dash for prey.
Art © Frank Frazetta from HERE.
From the Cleveland Plain Dealer:

The claw mark by the extinct giant short-faced bear still looks fresh today in a southwest Missouri cave that some scientists are calling a national treasure - an Ice Age time capsule sealed for thousands of years.

Riverbluff Cave, discovered accidentally five years ago on the outskirts of Springfield, is slowly yielding its fossil treasures as a small team of scientists and volunteers gingerly explores it while trying to preserve a rich bed of remains, from bones to tracks and dung.

"Remains in the cave date back at least 830,000 years and possibly over 1 million years. At some point at least 55,000 years ago, it was sealed by rocks and mud until a construction crew blasted a hole in one end while building a road on Sept. 11, 2001.

Monday, October 30, 2006

Fossil Footprints Found In Mexico

A trail of 13 fossilized footprints running through a valley in a desert in northern Mexico could be among the oldest in the Americas, Mexican archeologists said.

From Yahoo! News:

The footprints were made by hunter gatherers who are believed to have lived thousands of years ago in the Coahuila valley (photo) of Cuatro Cienegas, 190 miles (306 kms) south of Eagle Pass, Texas, said archaeologist Yuri de la Rosa Gutierrez of Mexico's National Institute of Anthropology and History.

"We believe (the footprints) are between 10,000 and 15,000 years old," De la Rosa said. "We have evidence of the presence of hunter gatherers in the Coahuila desert more than 10,000 years ago."

The oldest discovered footprints in the Western hemisphere are in Chile, and are believed to be 13,000 years old. There 6,000-year old footprints in the U.S. state of California, in Brazil and in Nicaragua.

The age of the Mexican footprints is dwarfed by those found in Africa. The oldest known hominid foot marks are in Laetoli, in Tanzania, and are believed to have been made 3.5 million years ago.
Photo from Reuters

Sunday, October 29, 2006

See Jane. See Jane Come to Cleveland Pt. 1

Last Wednesday, David Chapman, the CMNH Casting Technician, and I drove up to Beamsville, Ontario to pick up the ‘Jane’ mount that Research Casting International (RCI) produced for us. The CMNH acquired this mount through an exchange of cast material with the Burpee Museum who have the original skeleton.

Jane will go on display with Sue the T. rex from the Field Museum when that touring exhibit opens up at the CMNH Nov. 11, 2006. After that Jane will find a permanent place among our museum’s displays.

Photo © M. Ryan
To bring back our new dinosaur we rented a 17ft. U-haul van. Alas, this was not the one we took but ours did have an illo of some giant mushrooms reminiscent of the scene in the 1960 Version of The Lost World.

Photo © M. Ryan
Here’s a shot of part of their work area. That’s a bronze T. rex in the background and our unpainted Jane mount is in the lower left.

Photo © M. Ryan
David Chapman checks out another Jane mount that RCI was building they day we arrived.

Photo © M. Ryan
A close up of the bronze T. rex skull for comparison.

Photo © M. Ryan
Another shot of the bronze T. rex mount.

Photo © M. Ryan
Jane gets loaded in the van.

Photo © M. Ryan
Outside of the RCI building is a cast of the AMNH’s ‘Turtle Stone’.

Photo © M. Ryan
Another side of the stone.

See Jane. See Jane Come to Cleveland Pt.2

Our Wednesday started at 7:30am at the CMNH and David Chapman and I arrived back and unloaded the dinosaur about 9:30pm that evening. Aside from the problem caused by the Loading Dock being higher than the floor of the van, the two of us managed to get the mount out and into the loading bay in about 30 min. The next day we moved the mount (four ‘easy’ to assemble pieces) into the museum’s Kahn Hall where we (the VP and Exhibits Depts.) set it up the next day.

Photo © M. Ryan
That's VP volunteer Nicole helping David wheel the legs into the hall.

Photo © M. Ryan
Bolting the legs to their base.

Photo © Liz Russell/CMNH
Wiggling the body assembly into place. This was the only piece that gave us any real problems. That’s Arky Webber (top left), Gary Jackson, Nicole, Carl and me wrestling with the body rod.

Photo © Liz Russell/CMNH
Carl Jara gives the body assembly a shot of lube to help slide it into place.

Photo © M. Ryan
Half finished!

Photo © M. Ryan
Carl, Steve Green (long time VP volunteer) and David Chapman add the tail to the mount.

Photo © Liz Russell/CMNH
Nichole gets the honor of putting the head on.

Photo © Liz Russell/CMNH
All done!

Photo © M. Ryan
What’s the final mount look like? Well, I’ll hold that photo back until the show opens. Here’s a picture of the mount back in RCI before it was painted.

So, what is Jane? The Burpee Museum refers to it as a juvenile T. rex but there has been a lot of discussion about whether it is a Nanotyrannus (CMNH has the holotype) or whether Nanotyrannus is actually a T. rex. Mike Henderson of the Burpee is convinced of Jane’s status as T. rex, but his research has not been completed or published so for now the CMNH will be calling the mount a ‘juvenile tyrannosaur’.

Friday, October 27, 2006

Lucy Not Coming To the Smithsonian

The famous fossil of Lucy is scheduled to tour the United States, but one place it won't be on display is the Smithsonian's National Museum of Natural History.
From Yahoo! News:

"Not only is it not going to come to the Smithsonian Natural History Museum, it is our position that we don't think it should leave Ethiopia," museum spokesman Randall Kremer said Wednesday.

Smithsonian scientists feel certain objects, such as Lucy, are too valuable to travel and should remain in their homes, he said.

In announcing the plans to display the artifact, Ethiopian officials had listed Washington as a stop on Lucy's tour, though they didn't specify where in Washington the skeleton would go. The tour arrangements are being made by the Houston Museum of Natural Science and not all locations have been finalized.

The fossilized remains were discovered in 1974 in the remote, desert-like Afar region in northeastern Ethiopia. Lucy is classified as an Australopithecus afarensis, which lived in Africa between about 4 million and 3 million years ago, and is the earliest known hominid.

Most scientists believe afarensis stood upright and walked on two feet, but they argue about whether it had ape-like agility in trees. The loss of that ability would suggest crossing a threshold toward a more human existence.
Image Link.

New South American "Terror Bird"

Skull morphology of giant terror birds. 2006. Luis M. Chiappe and Sara Bertelli. Nature 443:929.

Artist's rendering of a new species of phorusrhacid ("terror bird"). The fossil skull of the new specimen—seen in the bottom photo alongside a modern California condor--represents the largest bird skull ever found. Skull photos by S. Bertelli; illo by S. Abramowicz.
From National Geographic News:

The new species of phorusrhacid is by far the largest terror bird yet, says paleontologist Luis Chiappe, director of the Dinosaur Institute at the Natural History Museum of Los Angeles County, California.

"Some of these birds had skulls that were almost a meter in length. [They] were colossal animals," he said.

The new, currently unnamed species stood about three meters tall and had a head as big as that of a horse.

The bird's most striking feature—literally—was its giant nose, a 46 cm beak with a sharp, curving hook shaped like an eagle's beak.

Terror birds were first discovered in the late 1800s and are believed to have become South America's top predators after the dinosaurs died off 65 million years ago. Chiappe and his colleagues examined the specimens and found that the fossils—a well-preserved skull and foot bones—are about 15 million years.

"We also have some of the foot bones [from] the same animal, which is great, because it allows us to make inferences about the speed of this animal."

Scientists have unearthed many examples of smaller phorusrhacid species that grew between 60 to 90 cm tall. But examples of the largest species, which like many ancient top predators lived in relatively small numbers, have been scarce.

Oldest Lamprey

Modern lampreys, such as the fish pictured above, haven't changed much from their ancient ancestors, according to a new study of a 360-million-year-old fossil. Photo USFWS.
Abstract: Lampreys are the most scientifically accessible of the remaining jawless vertebrates, but their evolutionary history is obscure. In contrast to the rich fossil record of armoured jawless fishes, all of which date from the Devonian period and earlier, only two Palaeozoic lampreys have been recorded, both from the Carboniferous period. In addition to these, the recent report of an exquisitely preserved Lower Cretaceous example demonstrates that anatomically modern lampreys were present by the late Mesozoic era.

Here we report a marine/estuarine fossil lamprey from the Famennian (Late Devonian) of South Africa, the identity of which is established easily because many of the key specializations of modern forms are already in place. These specializations include the first evidence of a large oral disc, the first direct evidence of circumoral teeth and a well preserved branchial basket.

This small agnathan, Priscomyzon riniensis gen. et sp. nov., is not only more conventionally lamprey-like than other Palaeozoic examples, but is also some 35 million years older. This finding is evidence that agnathans close to modern lampreys had evolved before the end of the Devonian period. In this light, lampreys as a whole appear all the more remarkable: ancient specialists that have persisted as such and survived a subsequent 360 million years.

Read more at National Geographic News.

Wednesday, October 25, 2006

Warsaw Dinosaurs

Dr. Eric Snively was recently in Warsaw on a research trip and filed this report for the Palaeoblog. All the photos and text are by Eric. Enjoy!
North American palaeontologists are rarely able to visit the Institute of Paleobiology in Warsaw and associated exhibits at the Museum of Evolution, which harbor specimens collected during the Polish-Mongolian expeditions in the 1960s and 1970s. The expeditions are familiar to most of us through scientific and secondary descriptions of collected dinosaurs, and were led by the great Zofia Kielan-Jawoworska and detailed in her book Hunting for Dinosaurs. Despite a creationist-tinged contemporary government, Poland has a grand and still extraordinarily vital tradition in geology and palaeontology. On a recent visit to photograph Cretaceous lizards, I took general photographs that may be of interest to Palaeoblog readers. Thanks to Madgelena Borsuk-Bialynika and Karol Sabath for scientific guidance and hospitality.

The picture above depicts the Palace of Culture and Science in Warsaw (the city's tallest building), a gift from Joseph Stalin. It contains the Museum of Evolution (with paleo exhibits from ZPAL), subtly shouting "Dear AMNH: Take THIS to your grave!! Love, J.S." The Institute of Palaeobiology is in a nearby building.

The Museum of Evolution itself is in one of the four integrated buildings around the tower. It's guarded by the Triceratops sculpture above, with me (5'8'') on a cool windy day for scale. According to Karol Sabath there is an (*ahem*) healthy competition between dinosaur sculpture parks in Poland, with rivalry driving up the accuracy of respective artwork.

Marta Szubert is the main sculptor for the museums of evolution and geology in Warsaw, and has done everything from fake taxidermy mounts of Smilodon, coccolithophores, working volcano models, Lucy the austalopithcine, karst caverns, to a full conodont apparatus. Her sculptures of Teratosaurus (now known from excellent material in Krasiejow) and Silesaurus are in the photograph above.

Karol Sabath is in charge of exhibits at the Museum of Evolution. He (and the same versatile sculptor) are mounting the large Tarbosaurus that he and Jorn Hurum recently described, seen in the next picture above. The scale on the lower jaw is about 15 cm.

Karol also does exhibits at the Museum of Geology, part of the Institute of Geology in the southern part of town. This is somewhat difficult to find, so at the intersection of the museum's street and that from the metro they have a life-sized mammoth sculpture to show the way. Among the museum's exhibits is a provocatively feathered sculpture of Dilophosaurus.

Monday, October 23, 2006

Gogonasus, The Latest Tetrapod Link

An exceptional Devonian fish from Australia sheds light on tetrapod origins. John A. Long, et al. Nature advance online publication 18 October 2006

The ancient fish Gogonasus. Photograph courtesy John Broomfield, Museum Victoria/Nature
Gogonasus, a fish that swam on an ancient barrier reef in Australia 380 million years ago had fins and nostrils remarkably similar to the limbs and ears of the first four-limbed creatures to walk on land, according to a new study.
From National Geographic News:

The new finding suggests that certain aspects of tetrapod ears and limbs can be traced much further back in "fishy looking" fish than had been previously known, says John Long, head of sciences at Museum Victoria in Melbourne, Australia.

Previously the lobed-finned fish—which was about 12 inches (30 centimeters) long and covered in diamond-shaped scales—was known only from crushed or fragmented fossil remains. But the new specimen, discovered last year in Western Australia, is nearly complete, with an almost intact skull, body, and fin bones.

"In simple terms, Gogonasus is a missing link between fishes that look like fish and the more amphibian-like elpistosteglians [tetrapod-like fishes such as Tiktaalik]," Long said.

Sunday, October 22, 2006

New Fossil Dwarf Buffalo Discovered

The bones of an extinct dwarf species of buffalo were recently unearthed on the Philippine island of Cebu.

From LiveScience.com comes this report of a new discovery by CMNH VP Research Associate, Dr. Darin Croft:

Bubalus cebuensis, the miniature buffalo stood at just more than two feet, three times smaller than today’s domestic buffalo, and weighed a mere 350 pounds. It probably lived during the Pleistocene (Ice Age) or Holocene Epochs, between 10,000 and 100,000 years ago.

"Natural selection can produce dramatic body-size changes. On islands where there is limited food and a small population, large mammals often evolve to much smaller size," said lead researcher Darin Croft of Case Western Reserve University in Ohio.

Fossils are rare in the tropical environments of the Philippines, a region lacking open rocky patches where fossils are often buried and preserved, and this is the first fossil mammal of any age reported from Cebu Island. The fossil remains were found 50 years ago in a phosphate mine by engineer Michael Armas. Nearly four decades later, he showed them to physician Hamilcar Intengan, who recognized their importance and brought them to The Field Museum for study in 1995.

The partial skeleton included two teeth, two vertebrae, two upper arm bones, a foot bone and two hoof bones. The species had relatively large teeth, which is typical of island dwarfs, but also relatively big feet, which are generally reduced along with other body features in dwarfing.

The finding supports the idea that the earliest water buffalo were large and first evolved in Southeast Asia. The animals likely traveled from the mainland to the Philippine islands when sea levels dropped roughly 400 feet during the peak of the “Ice Age” about 20,000 years ago.

At The Earth's Core

Long-Term Sustainability of a High-Energy, Low-Diversity Crustal Biome. Li-Hung Lin, et al. Science 314: 479 – 482.
Researchers have discovered an isolated community of bacteria nearly two miles underground that derives all of its energy from the decay of radioactive rocks rather than from sunlight.
The self-sustaining bacterial community, which thrives in nutrient-rich groundwater found near a South African gold mine, has been isolated from the Earth's surface for several million years. It represents the first group of microbes known to depend exclusively on geologically produced hydrogen and sulfur compounds for nourishment. The extreme conditions under which the bacteria live bear a resemblance to those of early Earth, potentially offering insights into the nature of organisms that lived long before our planet had an oxygen atmosphere.

Hunting trilobites at the Earth’s core. Sketch by late-18th century explorer/illustrator Mark Schultz and available now in his recently published book “Various Drawings Vol. 2”from Flesk Publications HERE.

The scientists had to burrow 2.8 kilometers beneath our world's surface to find these unusual microbes, leading the scientists to their speculations that life could exist in similar circumstances elsewhere in the solar system.

"These bacteria are truly unique, in the purest sense of the word," said Lin, now at National Taiwan University. " We found that the hydrocarbons in the environment did not come from living organisms, as is usual, and that the source of the hydrogen needed for their respiration comes from the decomposition of water by radioactive decay of uranium, thorium and potassium."

That subterranean world is a lightless pool of hot, pressurized salt water that stinks of sulfur and noxious gases humans would find unbreathable. But the newly discovered bacteria, which are distantly related to the Firmicutes division of microbes that exist near undersea hydrothermal vents, flourish there.

"These bacteria are probably close to the base of the tree for the bacterial domain of life," he said. "They might be genealogically quite ancient. To find out, we will need to compare them to other organisms such as Firmicutes and other such heat-loving creatures from deep sea vents or hot springs."

Saturday, October 21, 2006

Permo-Triassic Extinction Not Caused By Zombie Apocalypse

USC earth scientists turn up clues to explain disappearance of 90 percent of ancient species in the Permian-Triassic extinction event.

Photos © Kipling West.
From the press release:

What really caused the largest mass extinction in Earth's history?

The most likely explanation for the disappearance of up to 90 percent of species 250 million years ago, said David Bottjer, is that "the earth got sick." Bottjer, professor of earth sciences in the USC College of Letters, Arts and Sciences, leads a research group presenting several new pieces of the P-T extinction puzzle.

Pedro Marenco, a doctoral student in Bottjer's lab, has been testing a leading theory for the P-T extinction: that a warming of the earth and a slowdown in ocean circulation made it harder to replace the oxygen sucked out of the water by marine organisms. According to the theory, microbes would have saturated the water with hydrogen sulfide, a highly toxic chemical.

For a mass extinction "you really needed a good killer, and it [hydrogen sulfide] is really nasty stuff," Bottjer said.

USC earth scientists will reveal new clues at the annual meeting of the Geological Society of America in Philadelphia Oct. 22-25.
Yes, yes, GSA and SVP meetings are all well and good but I REALLY wish that I had been at the 2nd Annual Zombie Walk in Calgary. Grr…!
Thanks to Sukie and The 7 Deadly Sinners!

Tuesday, October 17, 2006

SVP Pleistocene Field Trip In Quebec

No, the Palaeoblog is not on hiatus—work and SVP has kept me busier than usual, and the ‘free’ time I’d normally devote to the blog is taken up with family matters. Things should hopefully return to a more normal schedule by the end of the month.

The Society of Vertebrate Paleontology 66th Annual Meeting started today here in Ottawa with the field trips. I co-lead the ‘Late Pleistocene’ (Late Wisconsinan-Early Holocene) trip along the NW margin of the old Champlain Sea with Andrew Milner from the St. George Dinosaur Discovery Center in Utah. Like me, Andrew spent a lot of time in Ottawa growing up, and, unlike myself, did a LOT of collecting of vertebrate material in and around the area. Sixteen participants joined us for a full day of exploration in the Gatineau hills of Quebec in cool (9°C), grey and rainy weather.

Looking for concretions at ‘Eardley Beach' that has produced abundant marine verts and inverts. That's Peter Dodson 2nd from the left.

Hiking into the ‘Eardley Creek’ locality. Lots of Atlantic Capelin (Mallotus villosus) have been found in the nodules here.

'Eardley Creek'. Stephen Godfrey is holding the bag on the left.

Dr. Kevin Seymour of the Royal Ontario Museum picks up a bird for the comparative collections. Little Known Fact: Kevin and I were in the same home room in High School.

Jim Kirkland in the creek.

In the Laflèche Caverns cut out of the “Grenville Marble” of the Canadian Shield (about 1 billion yrs). Hundreds of fossil bones have been collected from the recent sediments accumulated in the caves including Arctic fox, Snowy owls, Arctic hare and many others.

Checking out the fossil material in the Visitor Center at the Caverns.

Part of the crew at the Luskville Falls, our lunch stop.

Some video of some glacial scour marks on vertical rock faces in a quarry in Quebec

Sunday, October 08, 2006

Dale Russell's Dead Gator

From the Jacksonville Daily News:

Dale Russell, an N.C. State paleontologist and N.C. Museum of Natural Sciences dinosaur research coordinator, along with fellow museum specialists Walt Sturgeon and Becky Browning spent most of Tuesday searching the piles of refuse for the 12-foot, 475-pound alligator killed early last week when it was struck by a vehicle on U.S. 17 outside Jacksonville. The gator, estimated by state wildlife officials to be 85 years old, was killed Sept. 25.

“I read (the story) in the newspaper last week and thought, ‘Boy, that’s a big alligator,'" Russell (right) said. He was subsequently contacted by Indiana-Purdue
University professor James Farlow, who is conducting research on the physiology of crocodilians and crocodile-like animals.

“Because of the animal’s large size and northerly occurrence, he very much (wanted) to examine a thigh bone of the specimen microscopically for evidence of its growth and general condition,” said Russell. “He contacted me and told me to see if I could get a crew from the museum to come down here.”

“We want to know about the prehistory of North Carolina, and we’re interested in the Ice Age fauna here,” said Russell. “We’re going to study the growth rate, environment and diet of this alligator from its bones to compare it with Ice Age alligators that lived here before. We’d like to get some extremities — teeth, pieces of bones from the body… We’ll rebury the body after we take the samples.”

As time continued to pass with no gator in sight, hopes of a successful recovery soon began to fade. At 2:30 p.m. — after two additional hours were allotted by Horne to continue with the search — workers stopped searching. Russell, Sturgeon and Browning were left empty-handed.

Friday, October 06, 2006

Mark Schultz Interview

Comic Book Legal Defense Fund art © Mark Schultz
Our good friend Chad over at the excellent Digital Dream Machine Blog has posted a two-part interview with Mark Schultz HERE. Well worth a read.

For everyone paying attention I am now back from my extended summer field work including the past two months in Mongolia. But I'm not quite back in Cleveland yet. When I touched down on NA soil last week I immediately flew to Ottawa to deal with a family emergency. So, my apologies to everyone I've not got in touch with or owe e-mails to--most of my time has been waiting in hospital rooms or shuttling back and forth between various offices. I have squeezed in time to give a lecture to the Biogeography class at Carleton U. and do some footwork for the SVP field trip that I'm co-leading in a week and a bit, but I'm more or less limited in e-mail/internet access for the next little while.

When Hornworts Stalk The Earth

New findings to be be published online this week in the Proceedings of the National Academy of Sciences help resolve long-debated questions about the origin and evolution of land plants.

Plants exhibit a phenomenon known as alternation of generations, in which two alternating forms with different amounts of DNA make up a complete life cycle. One form, known as a sporophyte, produces spores, which grow into individuals of the other form, called gametophytes. Gametophytes produce gametes—eggs and sperm—which unite to form a fertilized egg capable of becoming a new sporophyte, thus completing a life cycle. While all plants exhibit alternation of generations, some spend most of their life cycle as sporophytes, and others spend more time in the gametophyte phase.

"Early in the history of plant evolution, a shift occurred between 'lower' plants (algae, liverworts and mosses) with a gametophytes cycle and plants like ferns, pines and flowering plants that spend most of their time with a sporophyte cycle. Geneticists, developmental biologists and evolutionists have been wondering how the switch happened and have put forth competing hypotheses."

Qiu's group used three complementary sets of genetic data, involving more than 700 gene sequences, to resolve relationships among the four major lineages of land plants: liverworts, mosses, hornworts and vascular plants (which include ferns, pines and flowering plants). Their analysis showed that liverworts—tiny green, ribbon-like plants often found along river banks—represent the first lineage that diverged from other land plants when charophyte algae first came onto land, and an obscure group called hornworts, often found in abandoned corn fields, represents the progenitors of the vascular plants.

"Basically we captured a few major events that happened in the first few tens of millions of years of land plant evolution," Qiu said. The results make sense in light of the plants' life cycle patterns. Charophyte algae, liverworts and mosses spend most of the cycle in a free-living gametophyte phase; the sporophyte is a small, short-lived organism that lives on the gametophyte. Vascular plants, on the other hand, spend most of their time as free-living sporophytes, with small, short-lived, gametophytes that often live on the sporophytes. Hornworts may hold a clue to understanding how this shift happened, as they spend most of their life cycle in the gametophyte phase, but their sporophytes---unlike those of liverworts and mosses—show a tendency to become free-living.

Thursday, October 05, 2006

Chased By A Viper

As promised, here is the QT clip of the viper who visited our Tarbosaurus quarry (one of the them anyways) at Altan Ula IV.

I video looks great on my laptop but has been slightly 'artifacted' in it's uploading to YouTube. Once I figure out how to correct this I'll repost it, but it's here for now. Enjoy.

Fossils Help Explain Present Biodiversity

Out of the Tropics: Evolutionary Dynamics of the Latitudinal Diversity Gradient. David Jablonski, Kaustuv Roy,James W. Valentine. Science 314: 102-106.
A team of scientists has completed a study that explains why the tropics are so much richer in biodiversity than higher latitudes.
From the U of Chicago press release:

Why the tropics are so much richer in species and evolutionary lineages than elsewhere on Earth has loomed as one of the largest questions facing biologists for more than a century. For the past 30 years, they have tended to view the tropics either as a cradle of diversity, where new species originate, or as a museum of diversity, where old species persist. And no resolution has been in sight.

The fossil data of the past 11 million years has broken this logjam. It shows that it's not an either/or proposition. The new study is the first to amass enough data to dissect the roles of extinction, origination and immigration directly. "I think we've killed the idea that the tropics is either a cradle or a museum of biodiversity. It's both," said Valentine, of UC Berkeley.

The fossil record indicates that the tropics have enjoyed a richness of biodiversity spanning at least 250 million years. The team acquired its data for the Science study by analyzing 150 bivalve lineages back through time and answer a series of key questions: Where do they start? How long do they last? Where do they persist? And where do they spread?

As the paleontologists traced the lineages back into geologic time, they found a consistent pattern in each slice of time, regardless of the prevailing climatic conditions. Over the entire 11-million-year period, they found that more than twice as many bivalve lineages started in the tropics than at higher latitudes. Meanwhile, only 30 varieties of organisms that lived only in the tropics went extinct, compared to 107 that lived outside the tropics, or at all latitudes.