Fossil Friday. Sub-category: Things I found and have been carrying around for 50 years but only figured out what they are recently.
This item is from Eckerty, Indiana, a famous locality for Mississippian-age (about 330 million years ago) fossils including especially blastoids, Archimedes bryozoans, brachiopods, and occasional corals and crinoids. They are often somewhat silicified and well-preserved and weather out nicely from their host limestone.
When I was there sometime between 1968 and 1970, I collected those usual suspects, and also picked up the thing in this photo. It’s been rattling around in a little pile of broken fossils that I hadn’t deemed worthy of putting in a cute little box.
But recently, while clicking around the internet for some unrelated reason, I chanced on a photo that reminded me of this. And now I know what it is. It’s a conulariid.
Since I’m a mineralogist and not a paleontologist, I had no idea what a conulariid is or was. As it turns out, they were animals whose place in the grand family tree of life is poorly understood. Although they are relatively uncommon world-wide, their existence spanned about 340 million years, from sometime in the very late Precambrian (Ediacaran, about 545 million years ago) to the late Triassic (about 205 million years ago). They even survived the great end-Permian extinction, but apparently declined and died out before the end-Triassic extinction event.
At least 36 genera have been described, but their taxonomic affinities are quite speculative. It seems that the prevailing (but rather debated) idea is that they are related to Cnidarians, a phylum which includes corals, sea anemones, and some jellyfish. Members of phylum Cnidaria were formerly included with Ctenophores (comb jellies) in phylum Coelenterata, but those two groups are now separate phyla and coelenterate is an informal name. Conulariids are usually reconstructed to look like sea anemones within a long open-ended four-sided ribbed shell. Some taxonomists think conulariids represent a phylum that was distinct from any phylum that exists today, but I have the impression that most place them in an early branch of the Cnidarians, but not very confidently (see Van Iten and others, 2023, Conulariid soft parts replicated in silica from the Scotch Grove Formation (lower Middle Silurian) of east-central Iowa: Journal of Paleontology 97:5, p. 961-970).
The specimen in my photo is black because the ribbed shells are phosphatic rather than either silica or calcium carbonate. Phosphatic materials are common in the biologic world – human bones, teeth, and kidney stones, trilobite exoskeletons, and some shelly animals like Lingula brachiopods. Those biological calcium phosphates are the mineral apatite (calcium phosphate) with 5% to 8% substitution of carbonate for the phosphate ion, and that’s what these conulariid fossils are made of as well.
My specimen is about 2 cm by 2 cm and the photos show front and back. Each side shows a bilateral symmetry, so it adds up to a four-fold symmetry which is typical of conulariids. This one has been squashed (it’s only about 3 mm thick), but imagine it as an elongate, four-sided tapering boxy cone-like body, something like the reconstruction above.
Conulariid is from Latin root words meaning small cone. As near as I can tell, the first examples, from what is now Estonia, were described and named by Karl Eduard von Eichwald in 1840 (Ueber das silurische Schichten-system in Esthland: Zeitschrift für Natur- und Heilkunde 1-2, 1-210).
Cnidaria is from Greek for stinging nettle, in allusion to the fact that many corals, anemones, and jellyfish are stinging animals. Coelenterate means hollow intestine, and Ctenophore means comb-bearing.
My conulariid is now in a cute little box. Stay curious. Never throw anything away.
For me it's fossils-shmossils, but the story is nice, and rewarding to learn finally what it is. I appreciate too the " poorly understood" awareness.
It was finding like-ish fossils as a child in NW Ohio that started my interest in geology. Thanks!