What Is This Colonial Creature?

[Harry Pristis]

I've had this on my shelf for decades with no identification. I collected it from a stream in Indiana. It is probably Mississippian in age. It is a silicified pseudomorph after some sort of colonial animal.

The fossil gives no hint of any stucture within the living chamber, though much of the surface has been broken down. I suspect that it is a sponge or sclerosponge such as a chaetetid, but I don't know. I don't see any evidence of zoned growth. The variable-size calicles are polygonal. The form is subglobular.

The "bottom" has a depression in which the calicles are unformed or amorphous -- it seems to be the base of the colony which perched on some rounded projection on the seabottom. (See the close-up image.)

Anyone here recognize this fossil?

Edited October 20, 2009 by Harry Pristis

[tracer]

according to wikipedia, there's even a town in indiana, Oolitic, named for the oolite found in the area. and i believe that your specimen is oolite.

[Auspex]

By Jove!

http://en.wikipedia.org/wiki/Oolite

[Harry Pristis]

By Jove!

http://en.wikipedia.org/wiki/Oolite

I guess I forgot to mention that these tubes or chambers are polygonal or prismatic in form. They are not egg-shaped in any dimension.

[tracer]

i know, but oolite can be polygonal. google "oolite + polygonal".

[kauffy]

Harry, looking at your images i would have said some form of Tabulate coral? I have found some nice examples from the missisipian of Indiana.

http://en.wikipedia.org/wiki/Tabulate_coral

http://www.museum.state.il.us/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=617&g2_serialNumber=3

[Mike Murphy]

I've had this on my shelf for decades with no identification. I collected it from a stream in Indiana. It is probably Mississippian in age. It is a silicified pseudomorph after some sort of colonial animal.

The fossil gives no hint of any stucture within the living chamber, though much of the surface has been broken down. I suspect that it is a sponge or sclerosponge such as a chaetetid, but I don't know. I don't see any evidence of zoned growth. The variable-size calicies are polygonal. The form is subglobular.

The "bottom" has a depression in which the calicies are unformed or amorphous -- it seems to be the base of the colony which perched on some rounded projection on the seabottom. (See the close-up image.)

Anyone here recognize this fossil?

Harry:

I believe the fossil is a tabulate coral,possibly Favosites, either from the Devonian or Mississippian. I don't believe that the specimen is an oolite or pisolite, which are generally circular and concentrically developed.

Regards,

Mike

[Harry Pristis]

Harry:

I believe the fossil is a tabulate coral,possibly Favosites, either from the Devonian or Mississippian. I don't believe that the specimen is an oolite or pisolite, which are generally circular and concentrically developed.

Regards,

Mike

The thing certainly could be a favositid. It's possible that all traces of mural pores and septal spines could have been worn away. (I don't think that's probable, though.) The thing does look like a denuded favositid skeleton!

I'm gonna' have to get out a dissecting microscope, and look closer than I can with my hand-lens.

[tracer]

well, i don't know. i was basing the thought that it might be oolite in part on the observation in a search-engine hit that oolites can become compressed while still plastic during formation, or can form polygonally when restricted in space during their growth/formation. although it's not a good analogy (so why am i saying it?), soap bubbles go from round to polygonal fast when they get together.

i had also noted that it looked like there might be a cross-section of a structure shaped like an ooid in the lower left corner of the zoomed-in picture of the surface. other points were that the shapes of the surface actually seemed quite variable both in size and form, and i didn't see anything that looked like an organic structure at all. i realized that the thing certainly didn't look like "classic", pearly oolite, but nature doesn't work the same way everywhere and the mineral contents vary also, so i thought it might could be. i guess my final thought was that the same forces forming the oolite might have formed the larger, overall shape of the thing and that it then looked a bit "squished" down, which would account for the lack of form on the bottom, the polygonal shapes in some places, etc.

having said all that, i'm sure that the collective experience of the others posting here far surpasses mine in looking at these kinds of things. i definitely don't have a reference sample in my collection, so maybe it is a tabulate coral and i'm just not seeing it.

[Bear]

*watches with great interest*

[MOROPUS]

Triying to nail it, looks a lot to Micheliniidae tabulated members. Here is an example:

[Harry Pristis]

Triying to nail it, looks a lot to Micheliniidae tabulated members. Here is an example:

Thanks, 'Moropus'. Micheliniidae is an interesting guess.

Class Anthozoa Ehrenberg, 1834

Subclass Tabulata Milne-Edwards, 1850

Order Favositida Wedekind, 1937

Family Micheliniidae Waagen & Wentzel, 1856

All the references I looked at suggest that the Micheliniidae are a Western European/Siberian/Chinese/Japanese taxon. I found no record for North America.

I did look at on-line images of some representative Micheliniidae as well as your own image. I don't see much resemblance.

The coralla (if it's a coral) diameter of my specimen range from roughly 5.6mm to <1mm with only a few at the larger size and many coralla in the 3-4mm size.

I still have get the thing under a microscope to look for traces of pores and spines.

[ashcraft]

For what it is worth, my initial thought was poorly preserved recepticulates, or sunflower coral.

Brent Ashcraft

[Frank Menser]

Ok...I am looking a this thing and (not an expert ) it looks for all the world to me like a fossilized Bee Hive or Hornet Nest.

But that's just me.

[jkfoam]

You know, Harry, a couple of 100 million years from now some one is going to dig up an old landfill and find an old sofa. The polyurethane foam in that sofa will have fossilized and will look pretty much like what you have found.

JKFoam ( an old foam chemist)

[Harry Pristis]

For what it is worth, my initial thought was poorly preserved recepticulates, or sunflower coral.

Brent Ashcraft

Okaaay! Brent may have hit on it! My fossil may be a colonial algae!

I had never considered algae, but FOSSILS OF OHIO lays it out like this:

KINGDOM PLANTAE

DIVISION CHLOROPHYTA

Class Ulvophyceae

Order Dasycladales

Family Receptaculitaceae

It would take an experienced worker to go from there; but, I like the look and description of

Tribe Cyclocriniteae

Genus

Cyclocrinites

But, that's just a guess.

I have looked at this fossil under a dissecting 'scope. I can find no evidence that would suggest coral (except for its colonial nature). No traces of septal spines (or even septa) nor of tabula.

On the recessed, smooth basal area I can see polygonal outlines. The smooth (and smooth is relative here) surface is made up of what appears to be polished large grains - like coarse sandstone. There is still a bit of matrix in the cells; that is the whitish material in some images.

I do see some tiny bits of debris adherent to the fossil. There is, for example, a section of crinoid stem.

Thanks, Brent. Any other ideas?

[abyssunder]

Maybe reef-builder polychaete worm tubes, similar to Sabellaria?

 

 

Bibliography of North American Geology, 1968. Geological Survey Bulletin 1268. (page 831)

Edited August 4, 2017 by abyssunder