This post was inspired by a prompt in the Worldbuilding Community - [Worldbuilding Prompt #998 - Aquatic fossil](https://peakd.com/hive-191038/@worldbuilder/worldbuilding-prompt-998-aquatic-fossil)

Enjoy !


![cKz0dExV3X8NgOtOO7nz--2--yj1q6.jpg](https://files.peakd.com/file/peakd-hive/alonicus/AK27ntVtQBSYmW53qh71X5FEGcxjUuQASTGmPXWkFWSCP7VfsDa43WZ9HHgYaQH.jpg)
*Image created by AI in NightCafe Studio*

"Commander, we're getting some very peculiar readings here."

The voice from the speaker was tinny and muted. But that was to be expected, with the command ship orbiting a thousand kilometres above the planet's surface and the submersible nearly two kilometres beneath the waves.

"That's okay, Doctor Zindrell. We're just a preliminary survey mission, we're expected to find interesting and unusual things. Tell me what you are seeing."

Commander Havmar was putting on his best impression of being the calm, collected senior officer. It was almost an unwritten rule that this was how expedition commanders were supposed to behave. But inwardly all he felt was a bubbling curiosity which, he had to admit to himself, was part of a burning desire to find something truly unique. Unique enough to get his name added to the Wall of Pioneers in the Great Hall of the Ministry of Exploration and Surveillance.

"We've descended to the designated peak of the mountain range, Commander, the one we've provisionally named as the Equatorial Girdle Range. It's a mess of caverns and undersea tubes, all packed with seaweed and corals, not to mention fish. My God, this place is going to export so many fish if we get permission for a colony !"

"That's very nice, Doctor, but what is unusual about a sea world having lots of fish ?" the commander's voice was dry; he couldn't hide his irritation. Sea worlds had fish, that wasn't exactly unusual.

"It's the mountain, Commander. We dropped a probe and it came back with a reading of 64 percent calcium and 14 percent phosphorous. Consistent across four different locations. It's like the whole mountain surface is made of bone ! The water is slightly higher than usual in those minerals, but that could be explained if it was gradually dissolving the mountain."

Havmar scratched his head, then turned to his second in command.

"Lieutenant Mibbir, can you drop extra-atmospheric probes onto a couple of the other mountains to see what you get ?"

"Yes, sir. Give me an hour."

It didn't take quite that long. Fifty minutes later, a dozen probes had dropped from space into the ocean depths. Every one of them came back with similar readings.

The communicator chimed again. This time it was from Doctor Yenable, who had been sent to conduct anthropological research on one of the many islands scattered across the world-spanning ocean.

"Commander, I've been following the comms from the undersea team. But I didn't have to ask the locals, they told me all about it."

"What, they told you the mountains were made of bone ?" Havmar asked, his voice clearly showing his incredulity.

"Not exactly. Their language is very advanced for a primitive tribal species living by subsistence fishing. They told us of their myth; that their forefathers a thousand years ago had a civilisation so advance they thought they were like gods, but that the true gods were offended. These gods live in a place called The Sky Island, and I think they mean the gas giant orbiting further out in this system. The gods supposedly sent a giant serpent down from The Sky Island which encircled the world and crushed their ancestors. All except one family who knew their place, who gave birth to every one of the Folk, as they call themselves. Then the serpent died and sank to the bottom of the sea."

Havmar stopped for a long while, thinking hard.

"Okay, all teams come back to base."

He waved everyone on the bridge to their seats.

"Let's go and visit this gas giant. We'd better be on the lookout for thirty-thousand kilometre long serpents. A thousand years is a bit too recent to take chances. I'm not going to recommend a colony for this place until we're absolutely, totally, one hundred percent sure it won't ever be visited by another one of these monsters."