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L.S., Wanted to share this "mini ecosystem" in fossilized form. The photos below show a rhizome of Osmunda pluma Miller 1967, a member of the royal fern family, from the Paleogene of the Fort Union Group (probably the Sentinel Butte Fm.) near Glenn Ullin in Morton County, North Dakota. On the first photo you can see a central stele surrounded by "eyes", which are cross-sections through the petioles of the leaves of the fern (see for comparison this section made through an extant Osmunda cinnamomea rhizome). More to the top and bottom of the photo, parallel lines are visible. These are the remnants of a woody texture, probably of some kind of gymnosperm (see also the second image, a flatbed scan of the entire slab containing the fern rhizome). According to Miller (1967, p. 143) the fern was growing on a so-called "nurse log": when a tree in the woods falls over and starts to decay, this can provide an excellent opportunity for new plants to grow! See for example these lovely examples of modern nurse logs. Cheers, Tim Fern rhizome of Osmunda pluma Miller 1967 showing central stele and petioles The fern rhizome is embedded in a woody texture, interpreted as a nurse log.

Paleocene plants in Central North Dakota are among the first fossils I've collected. Despite this I haven't given them the attention they are due lately. The preservation is very nice but due to various reasons they've taken a back seat to other outcrops in the state like the Cretaceous ones and I haven't thought about them for awhile. I am now reorganizing some of my Paleocene collection and a spark was reignited in me. I've decided to post some of the best examples here as a result. Come spring hopefully I can collect in additional Fort Union sites. The terrestrial Paleocene deposits I've collected in all belong to the Fort Union Group, mostly the Sentinel Butte Formation and the Bullion Creek Formation. I see that some sources now list the Fort Union Group as a formation and the Sentinel Butte and Bullion Creek as members but for the purposes of this post I'll treat it as a group. First, petrified wood is a common constituent of the Fort Union Group. Some of the wood is rather spectacular though. Silicified patterns are often striking. This piece is Sentinel Butte Formation.