The repeated sightings of the extinct thylacine (marsupial tiger)...


The J'ba Fofi (giant spiders) of the Congo...


And sightings of enormous snakes...


Are reported by quite a few people.
But is it possible?
Or is it misidentification/misjudged size?

As a young kid, I'd have believed they're out there!




ETA - I was a huuuge fan of UFOs and Creatures of Legend stuff,
         checking out multiple books weekly at school and local libraries,
         as well as watching weekend tv matinee "Creature Features."

         

I've watched a program or three on the thylacine. I wouldn't be surprised if some survived in remote areas. I hope they did, I just haven't seen any "smoking gun" evidence for it. Some of the vids are compelling though. It's a known species that hasn't been extinct (if it is) that long. I'm not even sure I'd consider it a cryptid. Other species thought to be extinct have been rediscovered, so this one might be as well. Fingers crossed.

The largest terrestrial arachnids (currently) are about 12" in leg span. In the fossil record, they get about half again that big. The supposed limitation is how their respiratory systems process oxygen, and even in the distant past when oxygen levels were an astonishing 35% (as opposed to the 20% today), they just didn't get that big. Aquatic specimens, notably the sea scorpions, got huge...as large as people, or even larger. But that's just not really possible today, without a completely different respiratory system. Interestingly enough, the coconut crab, another arthropod, developed exactly that, and now reaches sizes upwards of 3' in leg span. They are exclusively terrestrial, and will drown if put in the water. They aren't spiders though, they're crabs, so, there's that. I wouldn't say a spider 3x larger than the largest known species would be impossible, but it's highly unlikely.

The snake? Meh. The largest reticulated python on record is almost 33 feet long. The long-extinct Titanoboa reached up to 47-50 feet by some estimates. It's no great stretch of the imagination to see a gigantic snake, maybe a 30-footer or larger, and over-estimate the size of it while circling around on a helicopter. It's also not impossible snakes larger than the ones we've found exist. There's a lot of unexplored jungle out there.

I feel certain the thylacine is going to eventually show up. Too many hints of its presence for it not to be there.
I agree that respiratory function in an oversized spider requires much more oxygen in the atmosphere. Who knows? Maybe local conditions in dense jungle provide enough boost.
"The snake? Meh."
That pretty much sums it.

60 Minutes program on the thylacine