Dogs, as a species, are amazingly diverse.

They come with a variety of ear types, nose lengths, expressions, eye colors, and all sorts of fur coats. They also come in almost every size imaginable. Here are some of the dogs (both individual dogs and breeds) that some extremes among these variables.

The Tallest Dog

A Great Dane appropriately named "Zeus" is considered to be the tallest dog on record. His height from foot to withers (the top of his shoulder) was 44 inches. On his hind feet, he stretched up to 7 feet, 4 inches. That's one big dog! If you thought Great Danes were the tallest breed, though, you're wrong. As a breed, the tallest dogs are Irish Wolfhounds. The American Kennel Club (AKC) standards for Irish Wolfhounds, as measured from feet to withers, are 32 inches minimum for males and 30 inches for females. The overall standards for Great Danes are 30-34 inches for males and 28-32 inches for females.

The Shortest Dog

The tiny end of the dog spectrum touts a couple of dogs about the size of a guinea pig. One of these is "Milly", a Chihuahua who is only 3.8 inches tall. Although most of the tiniest dogs are Chihuahuas, the smallest dog on record was actually a dwarf Yorkshire Terrier who was only 2.8 inches tall, a full inch shorter. The breed standard for Chihuahuas states a height of 6 to 9 inches. The Yorkshire Terrier standard height range is 7 to 8 inches, right in the middle of the standard for Chihuahuas.

The Heaviest Dog

There are several dogs, all English Mastiffs, that are heavy dogs by anyone's standards. These include "Hercules" at 282 pounds, "Kell" at 294 pounds, and the giant "Zorba," who weighed a whopping 343 pounds and was 8 feet long. English Mastiffs are a heavy breed, with AKC standard weights of 160-230 pounds for males and 120-170 pounds for females.

The Lightest Dog

Chihuahuas rule the lightweight world. Two of the lightest dogs on record were both Chihuahuas: "Boo Boo" weighed in at only 1.5 pounds, and "Ducky" tipped the scales at a minuscule 1.4 pounds.

The Oldest Dog

One of the oldest dogs we know of, if not the oldest, was an Australian Cattle Dog named "Bluey." He lived an incredibly long life of 29 years and 5 months. Australian Cattle Dogs as a breed have a life expectancy of 12-16 years, so Bluey lived about twice as long as the standard for this breed.

Breeds that Live Longest

Although the life span of any one dog can vary greatly depending on the specific dog, health issues he may or may not have, care he received, exposure to dangerous situations, and countless other specifics, some breeds typically have longer life expectancies. As a rule of thumb, small dogs live longer than larger dogs. Both Chihuahuas and Yorkshire Terriers have a life expectancy of up to 20 years. Some other breeds with longer life spans include Australian Cattle Dogs and Pomeranians, both of which have life expectancies of 12 to 16 years. A number of breeds have life expectancies of 12 to 15 years, including Dachshunds, Toy Poodles, Malteses, Lhaso Apsos, Pugs, Beagles, and Miniature Schnauzers.

Breeds with the Shortest Life Spans

Unfortunately, there are other breeds with very short life expectancies. These are mainly larger dog breeds, including Bogue de Bordeaux, French Mastiff, Great Dane, and Bernese Mountain Dogs, all of which have a maximum life expectancy of 8 years. Neapolitan Mastiffs and Leonbergers may live to be 9. Irish Wolfhounds, Newfoundlands, Saint Bernards, and Scottish Deerhounds have a standard life of up to 10 years. Of course, any specific dog may life a longer or shorter life than the breed standards suggest. But the breed standards give you a good yardstick to help you determine when your dog is entering his twilight years. And if you have a mixed-breed dog—one of the best breeds of all—then it's all but impossible to know how long your dog may live. But whether your dog is 3 feet or 3 inches tall, weighs 2 pounds or 200 pounds, and is 18 months or 18 years old, you and he both know he's the best dog in the world.