Beach fossil (CA) ID

[Joelbaub]

Can this be identified?  Found at Huntington Beach in California.

[Darktooth]

I am gonna guess and say part of a shell, but can you take a pic of the other side?

[Tidgy's Dad]

I agree, it looks like part of a pectenid bivalve shell, but other angles and a scale would help. 

[caldigger]

It is a piece of modern barnacle.

[Brett Breakin' Rocks]

6 minutes ago, caldigger said:

It is a piece of modern barnacle.

Yep ...

 

[ynot]

+1 for  modern barnacle.

[Max-fossils]

+1 for fragment of modern barnacle. Nice color though  

 

 

 

 

 

@Darktooth @Tidgy's Dad just to inform you two, and explain why you were wrong, here is a picture of a fossil Chesapecten nefrens from the Calvert Cliffs (Miocene) in my collection. 

 

So at first sight, you could easily imagine that the piece in question is a part of a scallop. 

But here are the hard-to-see, yet critical differences:

The size of the ribs (or radial ridges) in a scallop are always (if you go from left to right) regular in their growth. The pattern is thin-thicker-thick-thinner-thin. And the difference in size between two consecutive ridges will usually be very small/barely noticeable. The angle between each ridge is also more or less steady.

Yet in the barnacle piece above, the ribs that could be mistaken as those of a scallop vary greatly in size and the angles between them is not steady. 

Also, you'll notice that in the barnacle, the "sub-ribs" (the smaller, very thin, radial ridges) only appear on the big ridges, and not in between. Yet in the scallop attached here, those "sub-ridges" are both on the big ridges and in between. 

Finally, in a scallop, all the ridges start together in that one spot on the bottom of the scallop, and then 'shoot out' from that spot, kinda like a cartoon explosion if you will, widening as they approach the edge of the shell. They all start in that one specific point in the middle. But in the barnacle, you can see that those ridges just start wherever, and not in a certain set point. (to show this I attached a quick drawing of what I mean. Scallop on left, barnacle on right. Yellow represents the big ribs.)

 

So, in summary: the ribs of a scallop are much more regular than those of a barnacle. 

 

Hopefully, Dave and Adam, you've learned something new from this, and now know how to recognize the difference between the two, even from just fragments  

 

Best regards,

 

Max