Remoras could be classified as freeloaders, having evolved sucker discs on the top of their heads, which they use to attach themselves to their hosts. They hitch a ride on sharks or other large marine animals (rays, whales, turtles), even though they are fine swimmers on their own. They also eat the leftovers or possibly the feces of their host animal. Living on a large animal also protects remoras from predators.

Remoras cause no damage to their shark host, who don’t get much back from remoras, unless sharks find amusement in their oddly upside-down disc-shaped heads. Remarkably, these suckers evolved over time from the fishes’ dorsal fins.

Two recent studies, looking at a fossil remora and remora larvae, have determined how these fins develop over time into a strong sucking device.

The first study, led by Oxford University’s Matt Friedman, examined a 30 million year-old early remora fossil with a fully functioning sucker on its back.

“The remora sucker is a truly amazing anatomical specialization but, strange as it may seem, it evolved from a spiny fin,” Friedman says. “In this fossil the fin is clearly modified as a disc but is found on the back of the fish. It enables us to say that first fin spines on the back broadened to form wide segments of a suction disc. After the disc evolved, it migrated to the skull, and it was there that individual segments became divided in two, the number of segments increased, and a row of spines were developed on the back of individual segments.”

The second study looked at the development of remora from the earliest larval stages and compared it to the larval development of white perch, fish that have typical dorsal fins.

The research team found that up to a certain stage in the fish’s development, the dorsal fin develops in the same way and looks very similar in both fishes. Then, through a series of small changes, the remora’s dorsal fin begins to expand and shift toward the head. By the time the remora has reached about 30 millimeters (1.18 inches) in length, the dorsal fin has become a fully-formed two-millimeter sucking disc. It still has the components found in the dorsal fin—the tiny fin spines, spine bases and supporting bones—but the spine bases have greatly expanded.

The study confirms that the specialized sucking disc is formed by a massive expansion of the dorsal fin through small changes while the fish is developing. This completely new structure is homologous to other fish with dorsal fins and is not an evolutionary offshoot.

Fins turning into suckers? It sounds like a super-power! Well done, remoras.

Image: Dave Johnson, Smithsonian Institution

T. rex—hunter or scavenger? In this day and age of social freedoms, why not choose both? Because studying dinosaurs, especially fierce, glamorous ones like Tyrannosaurus rex, leads to fame and—well, if not fortune, then at least movie deals.

A study published this week in the Proceedings of the National Academy of Sciences determines, due to dental data, that T. rex was definitely a hunter.

In the Hell Creek Formation of South Dakota, researchers discovered a fossilized spine of a plant-eating hadrosaur that had an odd bone growth. Examining the fossil with a CT scan, the researchers found a tooth—belonging to a T. rex—within the bone. In fact, the bone had grown around the tooth.

“Lo and behold, the tooth plotted out just exactly with T. rex—the only known large theropod from the Hell Creek formation,” exclaims study author David Burnham of the University of Kansas. “We knew we had a T. rex tooth in the tail of a hadrosaur. Better yet, we knew the hadrosaur got away because the bone had begun to heal. Quite possibly it was being pursued by the T. rex when it was bitten. It was going in the right direction—away. The hadrosaur escaped by some stroke of luck.”

T. rex teeth had previously been found in the fossilized bones of a young ceratopsian (Triceratops or one of its kin), but there was no evidence to conclude whether the ceratopsian was alive or dead when the T. rex made a snack of it. The hadrosaur’s escape provides evidence that T. rex was a dangerous, if not always accurate, predator, according to the study’s authors.

Because T. rex regularly shed its teeth, the dinosaur went away hungry, but otherwise no worse for the encounter. It would have grown a new tooth to replace the one left behind in the hadrosaur’s tail. This could have been a typical example of T. rex’s hunting efforts, even if it didn’t result in a meal.

But the story doesn’t end there. Just because you hunt doesn’t mean that’s how you find all your meals, and most scientists agree that T. rex was likely an opportunistic scavenger, too. In fact, researchers and science writers that focus on dinosaurs are tired of the either-or question. “Whether or not T. rex hunted is the most-asked question I get at talks and on the radio. And that makes me sad,” tweeted Brian Switek Monday in response to this study. There are so many more exciting questions in the field, posted paleontologist John Hutchinson, in his blog response to the publication.

So we’ll put it to rest here… T. rex: hunter and scavenger.

Illustration by Robert DePalma II

Almost a year has passed since crane operator Brandon Valasik discovered a Columbian mammoth (Mammuthus columbi) tooth at the Transbay Transit Center. When the find was donated to the Academy, Peter Roopnarine, curator of Invertebrate Zoology and Geology, told Science Today, “If we’re able to put the recent find on display, it will be a great opportunity to tell the story of the recent fossil history of San Francisco.”

The Academy has seized that opportunity. On a daily basis, Naturalist Center staff point out the tooth and talk about the ice age animals that roamed the area where San Francisco now stands. Visitors express astonishment that these real giants walked on this very spot.

“Wow!” “No way!” “Here, in San Francisco?” “You’re kidding!” “That’s incredible!” “Cool!” “Awesome!” To quote a few responses…

And this awesome discovery might enable more paleontological finds. A number of workers from different Bay Area construction sites have come to the Academy just to see the tooth. They said they wanted to see what it looks like up close and personal so they know how to recognize another one if it turns up on the job. Visitors marvel that a construction worker spotted the tooth and “didn’t mistake it for just another rock.” Many are thrilled to learn that other workers have come to see it so they can be on the lookout at their construction sites.

The wonder and pride extend to the Transbay Transit Center. Recently, the Senior Geotechnical Engineer at the site came in to show the tooth to some friends. He boasted, “I was the third person to ever hold the tooth, and I set it aside in a box for safe keeping for the paleontologist!”

A member of the Academy’s PR department shared that a Transbay Joint Powers Authority employee called and inquired, “Can you confirm if the mammoth tooth is still on display? We have members of the community inquiring.” And just this week, Transbay staff was hard at work, installing a display of the Center’s human-made found objects in their lobby at 201 Mission Street. In doing so, a staff member called the Academy’s Geology Research department to request photos because they plan to display a banner that features the tooth at the Academy. (Click here to see their exhibit.)

So yes… cool! And incredible! And awesome! It’s a foot-long piece of dentition once strong enough to grind up 320 kg (700 lbs) of vegetation a day for an animal weighing eight metric tons (18,000 lbs) that 11,000 years later retains a powerful hold on our imagination.

Additional ice age fossils wowing visitors in the Naturalist Center include a saber-toothed cat partial lower jaw with teeth, an American mastodon partial lower jaw with teeth, and a dire wolf skull. The latter item has numerous visitors asking, “Dire wolves really exist? They’re not just on Game of Thrones?”

The Naturalist Center features two other items of note from the Academy’s Geology Research collections: a 1.07-meter (3.5-foot) sauropod (herbivorous dinosaur) leg bone which visitors love to touch and a 20-centimeter (eight-inch) round sauropod coprolite (fossilized poop). The typical reaction from the coprolite’s biggest fans—groups of five- to seven-year-old boys—is an instantaneous holding of noses, squinting of eyes, and a collective shout of “Ewwwwww!” because, after all, why wouldn’t it still be stinky after 150 million years?

As always, the educational opportunities in the Naturalist Center are endless.

Nan Sincero is a naturalist and Program Lead in the Academy’s Naturalist Center.

What if the bacteria in your gut could produce a cleaner fuel for cars and trucks? It turns out, with a little fiddling, they can!

Researchers in the United Kingdom took the common gut bacteria, Escherichia coli, and added genes from the camphor tree, blue-green algae and two other bacteria (Photorhabdus luminescens and Bacillus subtilis). The addition of genes from blue-green algae and the two bacteria allow E.coli to make hydrocarbons from fatty acids; the camphor tree genes makes the hydrocarbons a similar length to those found in fossil fuels.

So when the scientists fed the glucose from plants to the souped-up E. coli, the gut bacteria turned the food into a fuel very similar to the diesel fuel derived from crude oil. Voilà! Gut Fuel!

The remarkable thing about this biofuel—a fuel derived directly from living matter— is that it can be pumped into current gas tanks with absolutely no modifications. Most other biofuels require vehicle owners to adjust their engines to operate with the more sustainable liquids, or involve mixing the biofuel with traditional fossil fuels.

John Love, of the University of Exeter, says this was a priority. “Producing a commercial biofuel that can be used without needing to modify vehicles has been the goal of this project from the outset. Replacing conventional diesel with a carbon neutral biofuel in commercial volumes would be a tremendous step towards meeting our target of an 80% reduction in greenhouse gas emissions by 2050.”

Well, not so fast… Producing this new biofuel en masse will take a lot more work. The scientists are hoping to wean the E. coli off plants and use animal or agriculture waste instead. Otherwise, they foresee a similar problem for their new biofuel as that faced by current biofuels—it’s tough to argue that we should be devoting our farmlands to growing fuels over growing food.

In addition, E. coli hydrocarbons cost more to produce than fossil fuel hydrocarbons. At least on paper. But in the long run, probably not.

The research is published in this week’s Proceedings of the National Academy of Sciences.

Image: Marian Littlejohn

“It looked too perfect to be a rock,” he told the Associated Press.

This is a great example of citizen science, says the Academy’s Peter Roopnarine, curator of Invertebrate Zoology and Geology.

Initial dating by the Transbay’s paleontology consultant put the fossil’s age at around 11,000 years old. The huge tooth—“about a foot in length and 8 inches tall,” according to The Bay Citizen—will be donated to the Academy.

The Academy has other mammoth teeth in its collection, including three specimens found in San Francisco. Other collections from that time period in California include a saber-tooth cat skeleton, bison and dire wolves.

Peter says if we’re able to put the recent find on display, it will be a great opportunity to tell the story of the recent fossil history of San Francisco.

The late Ice Age in California had a rich diversity of mammals—large saber-tooth cats, horses, wolves, bison and of course, mastadons and mammoths. Peter explains that the area was a series of lush valleys with open plains. The nearby ocean provided a very moderate climate—making this region a cooler version of today’s African savannah.

Peter says that it’s always difficult to reconstruct the past in modern, metropolitan areas, where fossils are moved or buried without a second thought. That’s what makes Brandon Valasik’s discovery such a treasure. And the fact that Valasik himself recognized it.

We’re not sure when we will receive the tooth here, but when it does arrive, our scientists will examine the specimen for more clues to the species and age. Stay tuned!