There are many theories abounding about which of today’s animals lived alongside dinosaurs, like the shark, which actually patrolled the waters long before dinosaurs walked the Earth, but unfortunately we have no proof that sharks ever walked on land. However, in almost every single one of the theories about which animals walked alongside the dinosaurs, the reference is to a relative, a genetic descendent, or an evolutionary sub-species. And that is exactly what they are, theories, as none have yet to be proven as fact.
In order to prove any animals that currently live on Earth walked alongside dinosaurs, skeletal remains would have to be found, dated to 65 to 250-plus Million years ago. And the skeletal remains would have to match an animal still here on Earth, living amongst us. It is now widely believed that birds either evolved from dinosaurs or were around at the same time, but there is no irrefutable proof that any modern-day birds were flying around while T. Rex was backing up Midge and the Megalosaurs at the Dinosaur Woodstock.
Lizards, namely the giant Ghila monsters from the Galapagos Islands, are similarly theorised as to have evolved from dinosaurs, but none have been proven to have lived, forgoing evolution, since over 65 million years ago. Even mankind has not been around for 65 million years, but the dinosaurs managed to rule the world for over 200 million years, a lot longer than mankind has been walking tall.
The first hominid, or human-like beings, were walking around a mere 3 million years ago, some 62 million years after the extinction event that wiped out the remaining dinosaurs, leaving mankind out as walking alongside dinosaurs. Birds evolved from dinosaurs, mostly leaving them out, except for the birds that were alive while the dinosaurs were still living on Earth. The bird-dinosaur relation is still in it’s infancy as a scientific theory, and is nowhere near being proven as fact yet.
There are so many animals and fish in the depths of the Oceans that we know absolutely nothing about, there may just be some that were swimming or even walking alongside dinosaurs, but we have no irrefutable proof of them doing so.
Lizards are the only real animals left on earth that fit the definition of dinosaur, that being a large, lizard type animal that ruled the planet from 250 to 65 million years ago. Lizards may not be 100 feet long, and they weigh in pounds what dinosaurs weighed in tonnes, but the similarities are astounding. Many a science fiction movie from the early days of horror films (think Jason and the Golden Fleece) had used Ghila Monsters and other lizards to portray dinosaurs. The reasoning behind this was the literal translation of dinosaur, which is Greek for terrible lizard.
Theories also abound that the duck-billed platypus and the crocodile are both basically unchanged through Millennia of evolutionary change and the Continental divide. That means they are pretty much unchanged from the times that dinosaurs walked the planet. Most scientists also agree that the cockroach is one of the elder “animals” on the Planet, and will be here long after mankind has become extinct. All existing insect groups either existed during or before the Mesozoic era, meaning that they all walked, crawled or slithered alongside dinosaurs.
Which of today’s animals lived alongside dinosaurs may be a longer list than any scientist or enthusiast theorizes. The only problem is that it is mostly conjecture as far as any animals larger than insects goes, if we assume that the Oceanic creatures do not belong on this list, since they were not walking alongside dinosaurs, but swimming.
The only proven animals to have been walking alongside dinosaurs would be cockroaches, and they will purportedly still be here on this pretty blue planet, third from the Sun, long after mankind has left the planet, or become extinct.