How Long Does Something Have to Be In the Ground Before It's Considered a Fossil?

iStock
iStock

Jelle Zijlstra:

The other answers here say that to be a fossil, something has to be mineralized in some way. The other answers are wrong.

At least, they don’t agree with common definitions in dictionaries and in paleontology. Usually, any remains or traces of an organism preserved in the ground are counted as fossils. People are less likely to use the term fossil for remains from the last 10,000 years (the Holocene, our geological period), but that is obviously arbitrary.

Here is the Oxford English Dictionary’s definition of fossil:

Something preserved in the ground, especially in petrified form in rock, and recognizable as the remains of a living organism of a former geological period, or as preserving an impression or trace of such an organism.

Especially in petrified form, not always in petrified form. They also say that “the term fossil is usually reserved for remains older than 10,000 years."

My textbook on paleobotany (Taylor et al., 2009, Paleobotany, Academic Press) doesn’t give a definition of the word fossil, but it does provide a nice catalog of the various kinds of plant fossils. Those include petrified wood, but they also include compression fossils, which are the result of the original plant material being compressed. No mineralization necessary. Pollen grains are a very common kind of plant fossil, and they are usually preserved unmineralized. Amber can isolate organic material sufficiently that it is preserved virtually unchanged.

Most paleontologists don’t discuss the definition of fossil, because it’s not terribly controversial. In one of my own papers I used the word for remains of the fossil rodent Cordimus hooijeri that are only a few hundred years old and not noticeably mineralized. Nobody called me out on it.

I did find one paper that explicitly discusses definitions: "A New Species of Fossil Ptinus from Fossil Wood Rat Nests in California and Arizona" (Coleoptera, Ptinidae), with a postscript on the definition of a fossil. This was in the context of beetles from woodrat middens, which were preserved as mostly unchanged exoskeletons. The author settled on “A specimen, a replacement of a specimen, or the work or evidence of a specimen that lived in the past and was naturally preserved rather than buried by man.” Again, no reference to mineralization. He discussed using the term fossil only for remains that are more than 10,000 years old; subfossil for remains before recorded history; and nonfossil for remains from recorded history. But that seemed arbitrary and unworkable; recorded history started at different times in different places.

Fossils are the remains of organisms of the past, regardless of their mode of preservation. Where exactly you draw the line between “organisms of the past” and “organisms of the present that just happen to be dead” is arbitrary and it usually doesn’t matter. If you need a definition (for example, if you’re making a list of fossil and nonfossil species), you come up with a reasonable if arbitrary definition. If you don’t need a precise definition, you don’t.

This post originally appeared on Quora. Click here to view.

Why Do Dogs Eat Grass?

iStock/K_Thalhofer
iStock/K_Thalhofer

If something is edible (or even if it's not), many dogs will gladly make a meal of it. But if you see your pet grazing on your front lawn like cattle, it may be driven by something more than its undiscerning appetite. Eating grass frantically can be a sign that a dog is sick.

It's not unusual to see a dog vomit after consuming grass, prompting some pet owners to wonder if their dog ate the grass to soothe its own upset stomach or if the grass is what caused its symptoms in the first place. According Dr. Jerry Klein, chief veterinary officer for the American Kennel Club, this behavior is sometimes a response to symptoms that were already present. "When dogs go outside and gobble grass really quickly, there's usually a reason, an instinctual behavior to try to induce some kind of gastrointestinal reaction," he tells Mental Floss. "When they realize they're nauseous or something else, the only thing they know how to do is to force themselves to vomit. Some dogs that eat grass chomp it down without really chewing it, and often times may vomit something up and that's how they treat themselves."

Despite it being a common issue for pet owners, little research has been done into why dogs eat grass. It's likely that stomach problems only explain this behavior part of the time. In other situations, a dog may eat grass for the same reason it eats your shoes or the groceries you left on the kitchen counter: Because it's hungry, anxious, or bored.

So how can you tell when your dog is munching grass for pleasure and when it's trying to induce itself to vomit? Pay attention to the way it eats. Dogs are omnivorous, meaning they eat both plants and animals, so just eating grass alone normally won't be enough to make it sick. But if a dog is gorging on grass faster than it can chew it, that may be an indication that something is wrong. Whole blades of grass can irritate a dog's throat and stomach lining, potentially causing them to throw up if they swallow a lot of them in a short amount of time.

No matter the reason for your dog's grass-eating habits, Klein says that they aren't a major issue. The behavior shouldn't be encouraged, as grass in public places can potentially carry harmful chemicals like pesticides, so stop your dog if you see it grazing. But if it shows no signs of illness or discomfort afterward, there's no need to rush it to the vet. "If I see a dog eating grass, I'm not going to panic. I would try to stop it and then monitor it to see how it acts in the next 15 to 20 minutes. Look at how the dog's acting, its body shape and movement, and the feeling you get from the dog."

One condition related to vomiting that would warrant a trip to the vet is something called bloat. This happens when a dog's stomach fills with air, causing it to retch without actually throwing anything up. This is a medical emergency and can be deadly if left untreated.

A dog who vomits after eating grass and looks happy afterward, on the other hand, is probably not a cause for concern—though you may argue otherwise when you're steam-cleaning your carpet.

Have you got a Big Question you'd like us to answer? If so, send it to bigquestions@mentalfloss.com.

How Do Airplanes Land in Water?

iStock/oblong1
iStock/oblong1

Joe Shelton:

At least in terms of the physical act of landing, seaplanes and floatplanes land on the water pretty much in the same way that land based airplanes land on the ground.

They start with an appropriate approach airspeed, a slight flaring just before touching down, feeling it as the aircraft touches the water, and then it's slightly different. Because of the water's drag the aircraft will slow very quickly and settle into the water. Brakes aren't really needed. And that's good because they don't have any brakes that work in the water.

Once in the water they are as controllable as a boat. Which is to say, not that much. In fact, in the water they are navigated pretty much just like a boat.

Most if not all seaplanes and floatplanes have "water rudders" that allow them to steer in the water just like a boat. But as they approach a pier or beach you'll usually see the engine stopped and the pilot out on the float or leaning out of the aircraft with an oar rowing the boat to shore (sounds like a Peter, Paul, and Mary lyric).

If the question wonders why the aircraft don't sink, it's because they are designed to float.

Floatplanes are typically normal aircraft that have been outfitted with floats, usually two, one under each wing. Seaplanes, on the other hand, are designed specifically for water operations.

Many or even most floatplanes and seaplanes are what's called amphibious. That means that they can land and take off from both water and land. Typically they have retractable/extendable wheels (landing gear).

While it's important that an aircraft's landing gear has been extended when landing on the ground, it's equally important, if not more so, that the landing gear is retracted when landing on water.

Here's why:

The aircraft in the video is a "floatplane" with aftermarket floats.

a firefighting seaplane
iStock/Paolo Seimandi

This is a seaplane where the fuselage is designed to float like a boat. It also has floats, but they are part of the design.

a Piper Apache floatplane
Phil Hollenback, Flickr // CC BY-NC 2.0

This is a Piper Apache on floats. It's also the aircraft that I earned my Commercial Multiengine Seaplane rating in.

This post originally appeared on Quora. Click here to view.

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