My son is five, and so dinosaurs are a huge part of his world. Perhaps not as huge as Star Wars, but he still loves some terrible lizards. As a result, we watch a lot of dinosaur-theme programming. Walking with Dinosaurs is probably his favorite, but we watch others as well.
One day, I put on Walking with Beasts instead, which worked well. Giant prehistoric animals are giant prehistoric animals, after all, and he also loves saber-tooths. So we’re watching, and he’s oohing and ahing and telling me he doesn’t like the giant birds, and then he hits me with a question: “were the elephants alive with the dinosaurs?”
Clearly, the answer is “no”. And I believe he sort of understands that – he’s a little fuzzy about chronology, though (anything that happened in the past is still “yesterday” to him, even if it was last year), and all of them are giant prehistoric animals. So it makes sense, in a five-year-old sort of way, that they could have been contemporaries.
When did the dinosaurs live?
To paraphrase Grandmother Fish, dinosaurs lived a long, long, long, long, long time ago. How long? Well, as of 2012, the oldest known dinosaur is the Tanzanian fossil Nyasaurus parringtoni, which is around 240 million years old.
Despite the picture, we don’t actually know much about what it looked like – we only know it from an upper arm and some spine bones. It’s been estimated at 2 to 3 meters (6.5 to 10 feet) long, and we have no idea what it ate or whether it was a biped or a quadruped. We don’t even know for certain if it was a dinosaur or not, although we do know that it had an elongated deltopectoral crest – a feature that is found on pretty much all dinosaurs.
What is a dinosaur?
“Dinosaur” – derived from the Greek words for “terrible lizard” – is the common name for the Dinosauria clade, which is under the phylum Chordata, which is under the kingdom Animalia. All of which is a fancy way of saying that all dinosaurs have a common ancestor and represent a single “branch” on the “tree of life”.
The question “when did the dinosaurs live” is a tricky one, because they are actually still around. The clade Dinosauria contains the order Saurischia, which contains a suborder called Theropoda. One of the clades within Theropoda is Averaptora, which contains a clade called Avialae. And Avialae (meaning “bird wings”) is the direct ancestor of Aves, which are modern birds. That means that if you’re an American and you eat the traditional Thanksgiving dinner, you eat a dinosaur (specifically, an avian dinosaur) every November. Along with an estimated 92.1 pounds of dinosaur annually.
When did the last non-avian dinosaur live?
The last known non-avian dinosaur was a Triceratops excavated in the Hell Creek formation in Montana in 2011. This fossil was found just five inches below the K-T boundary, which is the geologic layer that marks the transition from the Cretaceous to the Tertiary periods. It’s significant because, before this find, no fossils had been found less than ten feet below that boundary. The K-T boundary is 65 million years ago, and this specific dinosaur lived within a few tens of thousands of years of that boundary line.
What is a mammal?
Mammals are animals within class Mammalia – from the Latin word mamma, meaning breast – which is part of the clade mammaliaformes, which is part of the clade Synapsida, which is part of the clade Amniota, which is within the phylum Chordata, which is part of the Animalia kingdom. Mammals are distinguished from birds and reptiles by the possession of a neocortex, hair, three middle ear bones, and mammary glands.
When did the first mammal show up?
How long? About 195 million years, based on the discovery of a fossil skull of a shrew-like mammal in Yunnan Province in China. Grandmother Mammal has been named Hadrocodium wui, and was about the size of a paperclip and may have weighed as much as 2 grams. Details are sketchy, since all we have is a skull, but Hadrocodium wui had a mammal-like set of inner ear bones, and teeth that are consistent with animals that suckle their young.
What was the first elephant, and when did it live?
Elephants – to continue the taxonomy lessons – are part of the Elephantidae family, which is part of the Proboscidea order, which is part of Mammalia. The oldest known member of Proboscidea is Eritherium azzouzorum.
Eritherium was discovered in the Sidi Chennane quarries in Morocco in “bed IIa”, which is dated to 60 million years ago. It is known from skull fragments and teeth, and the “estimated body mass of Eritherium azzouzorum, inferred from allometric relation of tooth size [regression equations from Damuth et al. and Janis], varies between 3 and 8 kg”. That’s a range of 6.5 to 17.5 pounds for US metric-illiterate Americans, meaning that the oldest known elephant was about the size of my cocker spaniel.
So. Were the elephants alive with the dinosaurs?
Yes. And they still are. Here’s photographic evidence.
Of course, if we go with the common understanding of “dinosaur” (i.e. non-avian dinosaur), then they weren’t. But they came close. Really close. Eritherium was around about 5 million years after the last of the dinosaurs. And while 5 million years is a long time, it’s not all that long compared to how long dinosaurs lived (about 135 million years) and how long elephants have been around (60 million years, in one form or another).