Saturday, November 12, 2011

Dictyonella reticulata from Lockport, NY

A well known fossil from the middle Silurian is Dictyonella. Those from the Rochester shale are called Dictyonella corallifera while those from the Waldron shale are called Dictyonella reticulata. The specimen below is from the Irondequoit limestone Rochester Shale so I'm calling it Dictyonella corallifera. It was found near Lockport, NY and it's age is 427mya (Sheinwoodian stage).

As you can tell the most obvious feature is the shell ornamentation. It's the only brachiopod that I have found with such a complex pattern.

It almost looks like a Bryozoan is coating the shell. I wonder what advantage the ornamentation would have given the brachiopod or was it just a evolutionary dead end?


  1. Nice find! I have only found two Dictyonella so far. The pattern on the surface is a mystery. Maybe it helped the creature attach to the seafloor?

  2. Dave,

    Look at the Permian Waggenoconcha montpelierensis (Productus humboldti) brachiopod and see the surface similarities. Find the info in the Index Fossils of North America (1944) page 351 and Plate 137 figures 35-38.
    The diamond pattern appears to have been the base for spines.

  3. Hmmm... Interesting idea. Spiny brachs seem to be more common in the Carboniferous and Permian periods but they are not unknown in the lower Paleozoic. I just got a copy of the "Index Fossils of North America" so I will look that plate up.

  4. Dave,
    Check out the posting about this brachiopod on the Fossils and Other Living Things blog:
    He points out that it has a new genus name as of 1994: Eodictyonella. Also cited is a theory published in 1981 that the openings on the surface grid pattern may have "contained organic caeca or sacks" that inhibited predatory drilling into the shell.

  5. Mike, Interesting post with some good info. Got another blog to read plus one more from his links: