Found in yard outside Seattle

[Shauna206]

I found this under a few inches of dirt in my yard. I've lived here since 2004 so surprised to find it. This novice is curious to figure out what it is, how common this is to find, possible age...

I'm about 5 miles from the Puget Sound outside Seattle and at 500 ft above sea level so guessing it was brought to where I found it. Can almost make out tiny shells in some of the holes. It's quite heavy and slightly larger than a football.

Thanks community!

[Thomas.Dodson]

The holes are shipworm burrows. It's a bit harder to age without more info. A geologic map of your area can be used to pinpoint more probable formations and ages. Don't discount the possibility it came from nearby either, sea levels and changing elevation can mean marine fossils where you found it. However, buried under a few inches of dirt and no real bedrock suggests it was moved from somewhere, possibly by man or natural forces. Any outcrops of bedrock nearby?

[Fossildude19]

Wrinkled rock borers and Cliona  sp. sponges can make these types of holes as well.

[DPS Ammonite]

I think that we are looking at a secreted mass of “worm” tubes such as those made by serpulids. The tubes are too small and meandering to have been made by shipworms (mollusks) and too deep for sponges such as Cliona. Borings are usually placed more randomly in a rock. The hollow tubes are packed too closely to be burrows. A rock soft enough to be this burrowed would probably not be strong enough to have survived this amount of burrowing.

 

 

I see a larger carbonate tube made by a serpulid or mollusk.

 

Do the tubes fizz in acid?

 

https://en.m.wikipedia.org/wiki/Serpulidae

 

 

Edited August 6, 2021 by DPS Ammonite

[Thomas.Dodson]

26 minutes ago, DPS Ammonite said:

I think that we are looking at a secreted mass of “worm” tubes such as those made by serpulids. The tubes are too small and meandering to have been made by shipworms (mollusks) and too deep for sponges such as Cliona. Borings are usually placed more randomly in a rock. The hollow tubes are packed too closely to be burrows. A rock soft enough to be this burrowed would probably not be strong enough to have survived this amount of burrowing.

 

 

Possibly, but I don't think size of the burrows is a good indicator. You might be right about the meandering although I've seen very closely packed shipworm burrows (see below).

 

My understanding is shipworm burrows are calcareous lined and thus fossilize even when the surrounding wood decays/isn't replaced and you can end up with some blobs of rock that contain the borings without any trace of wood. Then there's also the issue that ever since they discovered modern rock boring shipworms you can't assume shipworm burrows mean the presence of wood. It is possible it was a species that bored carbonate rock. I did see the bigger serpulid/mollusk tube but figured it was unrelated to the main borings.

 

Rather tightly placed and small. I never found a indicator of wood for this piece, just sandstone.

 

So this might just add to the confusion but I think shipworms are still a distinct possibility.

 

[ChristineR]

I am thinking pacific fission worm colony. Or false brain coral, which seems less likely, because the spaces the space between burrows appear more robust . 

 

https://seagrant.oregonstate.edu/visitor-center/found-beach/false-brain-coral

 

https://seagrant.oregonstate.edu/sites/seagrant.oregonstate.edu/files/sgpubs/onlinepubs/g03002.pdf

 

I will let you know once I have ID'd mine pictured below.

[Thomas.Dodson]

29 minutes ago, Christine.Rowland said:

I am thinking pacific fission worm colony. Or false brain coral, which seems less likely, because the spaces the space between burrows appear more robust . 

 

https://seagrant.oregonstate.edu/visitor-center/found-beach/false-brain-coral

 

https://seagrant.oregonstate.edu/sites/seagrant.oregonstate.edu/files/sgpubs/onlinepubs/g03002.pdf

 

I will let you know once I have ID'd mine pictured below.

Looking at it this seems like a good possibility. That said, it appears false brain coral and pacific fission worm are just two names for the same organism, colonies of Dodecaceria fewkesi.

[ChristineR]

7 hours ago, DPS Ammonite said:

I think that we are looking at a secreted mass of “worm” tubes such as those made by serpulids. The tubes are too small and meandering to have been made by shipworms (mollusks) and too deep for sponges such as Cliona. Borings are usually placed more randomly in a rock. The hollow tubes are packed too closely to be burrows. A rock soft enough to be this burrowed would probably not be strong enough to have survived this amount of burrowing.

 

 

I see a larger carbonate tube made by a serpulid or mollusk.

 

Do the tubes fizz in acid?

 

https://en.m.wikipedia.org/wiki/Serpulidae

 

 

I agree with your assessment.  The walls between each “tube” are too thin to be borings. There is also a lack of intersections. The sites with a photo of similar specimens are not scholarly sources and may be incorrectly attributing these to fission worms.