Let's talk brachiopods!

[GeschWhat 2,677]

Hi all,

 

I don't know much about brachiopods beyond general recognition. Since I found that little unidentified echinoid(?) I have decided to prep some of the loose brachs that I found on a recent trip to Fillmore Co., MN. The complete brachiopod here appears to have been attached to another brachiopod shell. So here are my questions.

 

1. Can anyone identify the brachiopod? (I am assuming they are the same species)

2. Would this be considered an unarticulated brachiopod?

3. I haven't finished prepping the interior of partial brachiopod. I wasn't sure what to call it so I referred to it as the host shell in the photo. It has what almost looks like an open crack. Any idea what might have caused this? There are little black specs surrounding it. Could this have been caused by another brach pedicle? When I was prepping it, it kind of reminded me of a burrow lined with tiny fecal pellets - but my imagination does tend to get the best of me.

 

As always, thanks for your help!

 

@minnbuckeye @Bev @Tidgy's Dad

[Spongy Joe 247]

Hey, Lori! I'll let the others have the last word, so this is me sneaking in first to do the bits I can!

 

1. Not a clue. I'll go as far as 'orthid'...

2. The complete one is an articulated articulate brachiopod. 'Articulated' versus 'disarticulated' refers to whether the two shells are still together as in life. These clear are. 'Articulate' versus 'inarticulate' refers to the arrangement of muscles and hinge structures, and is a taxonomic term; broadly, articulates have calcite shells, and inarticulates have phosphatic ones. It actually gets a bit complicated (craniids have inarticulate phosphatic shells...), and the terminology is now rather outdated. We mostly now use 'lingulate' for inarticulates, and 'rhynchonelliform' for calcitic, articulate brachiopods like this one.

3. I don't think it was attached in life; the pedicle was soft, and came from a tiny hole in the middle of the umbo (look in the middle of the projecting bit of the pedicle valve in the ventral view). In this case, if the holes in each lined up, then I'm wondering at a boring organism (e.g. a sipunculan) that burrowed its way through the two shells. The crack looks like post-mortem damage to me (crushing of the shell, probably after burial), with some sort of iron minerals growing in the microenvironment.

 

Now, lets see what the brachiopodophiles can add or disagree with..!

 

[Peat Burns 2,758]

Compare with Dalmanella / Onniella.  Onniella quadrata?

[fifbrindacier 4,739]

5 hours ago, Spongy Joe said:

2. The complete one is an articulated articulate brachiopod. 'Articulated' versus 'disarticulated' refers to whether the two shells are still together as in life. These clear are. 'Articulate' versus 'inarticulate' refers to the arrangement of muscles and hinge structures, and is a taxonomic term; broadly, articulates have calcite shells, and inarticulates have phosphatic ones. It actually gets a bit complicated (craniids have inarticulate phosphatic shells...), and the terminology is now rather outdated. We mostly now use 'lingulate' for inarticulates, and 'rhynchonelliform' for calcitic, articulate brachiopods like this one.

I think you're disarticulated.

[GeschWhat 2,677]

10 hours ago, Spongy Joe said:

In this case, if the holes in each lined up, then I'm wondering at a boring organism (e.g. a sipunculan) that burrowed its way through the two shells.

Thanks, Joe! The holes do line up, that's why I thought it was a pedicle. If it is a boring, that makes it even cooler! Ichnofossils are my favorite. You know, I have grown up around brachiopods my whole life and never really took the time to understand them. Of course these are a bit different than those in my neighborhood. Here are photos I took when the two broke apart. Hopefully you can see in the photos where they lined up.

 

Again, I'm not familiar with naming. Is the side I labeled ventral view actually the bottom. I labeled the views thinking the hole was a pedicle.

 

 

[GeschWhat 2,677]

9 hours ago, Peat Burns said:

Compare with Dalmanella / Onniella.  Onniella quadrata?

I'll have to take some photos from the sides for comparison, but the articulated brach looks a bit like this Dalmanella sp. from @palaeopix gallery. 

 

[Tidgy's Dad 15,169]

Paucicrura perhaps? 

[GeschWhat 2,677]

49 minutes ago, Tidgy's Dad said:

Paucicrura perhaps? 

That seems to fit too. Here are some (bad) photos from the sides of the articulated brach. I had a hard time getting the camera to focus where I wanted it to. Ugh!

 

[Tidgy's Dad 15,169]

Hmmm. 

It doesn't look like any of those mentioned from the side! 

[GeschWhat 2,677]

5 hours ago, Tidgy's Dad said:

Hmmm. 

It doesn't look like any of those mentioned from the side! 

Do you want me to put these aside for you? I think I have a few other loose ones like this that I haven't prepped - this one appears to be the best.

[Tidgy's Dad 15,169]

Just now, GeschWhat said:

Do you want me to put these aside for you? I think I have a few other loose ones like this that I haven't prepped - this one appears to be the best.

Yes, please! 

Whatever it is, it's a lovely specimen. 

Thanks, Lori.