Sunday, April 8, 2018

Phycodes: bundles of burrows

I'm going out of the office again, so, like last year, I'm tossing up a few pictures of something I find interesting, in this case an invertebrate trace fossil called Phycodes (not to be confused with Phycodes the moth). I touched on Phycodes briefly a few years ago, using the image included below:

That pale gray color is characteristic of the Brickyard in Lilydale, for whatever reason(s).

The whole piece looks like this:

"Licrophycus ottawaensis" in older literature.

I collected it on a Geological Society of Minnesota visit back in 2006 and it has since become one of the pieces I like to take to events because it's a great teaching fossil. I ask people what it is and let them explain their choice if they want to, and then I identify it. I get a lot of plant-based guesses (which of course is what a lot of paleontologists and geologists thought this kind of structure was decades ago). What Phycodes really is is an invertebrate trace fossil recording the behavior of some kind of wormy animal probing in the mud for food and returning to a central point. This resulted in splayed bundles of burrows, giving the trace fossil a characteristic root-like or mop-like appearance. It doesn't have quite the oomph of a dinosaur bone, but it looks interesting, it's good for conversation, and worms are more familiar than, say, crinoids.

When space is an issue, I have a more compact specimen.

Phycodes turns up every so often in the Decorah. It's not as common as Rauffella (which has turned up in a half-dozen posts so far), but it certainly makes a striking fossil.

Suitable for framing: this chunk is almost entirely Phycodes, with little matrix, which also makes it more fragile than the first two specimens (too bad, because it's also the best). The individual tubes are a bit smaller in diameter than those of the first two as well.

The makers of Decorah Phycodes differed from the makers of Rauffella in a couple of notable ways: Phycodes-makers were smaller (a few mm in diameter versus finger thickness for many Rauffella) and apparently smoother (no surficial striations in Phycodes).

This piece is one of the group from the construction site last year. I'm not certain what kind of ichnofossil it is. It resembles Phycodes templus, but it's also kind of poorly preserved and it's not clear if the burrows are bundled, so it might not be Phycodes at all. (Another possibility is poorly preserved "Camarocladia".) Note the brassy ooids.

Saturday, March 31, 2018

"Prorichthofenia": brachiopod horn corals

April Fools' Day not only falls on a weekend this year, but Easter, so I wouldn't be surprised if the typical crop of spoof news articles and blog entries is thinner due to other time commitments. Not that I mind too much; the whole thing gets old, year after year. Still, with April 1 in mind, here are some fossils that aren't what they seem: brachiopods from the Permian of Texas that put a lot of effort into being horn corals.

Sunday, March 25, 2018

Three weeks of ankylosaurs and pterosaurs

March has been busy over at The Compact Thescelosaurus, with ten new entries adding three ankylosaurs, four pterosaurs, and three theropods. There's still a week to go, too. Sometimes people talk about following taxonomy as another kind of stamp collecting. I have a more artistic point of view, with each specimen as more along the lines of tiles in an incomplete mosaic or notes in an unfinished song, each contributing to a greater whole. It just so happens that the currency of the realm is in species and genera. (I also keep track because you can't tell the players without a program!) As usual, I'll leave the theropods to others, except to say that it's nice to see Arkansaurus finally graduate from informal name to the big leagues, thanks to Hunt and Quinn (2018) (the name has figured in print since 1983, after all). A few comments on the ankylosaurs and pterosaurs:

Sunday, March 11, 2018

Marshalls Creek Mastodon

This is something of an apology. I gave a paleontological presentation for the folks at Delaware Water Gap National Recreation Area last September, and after I finished someone brought up the Marshalls Creek Mastodon. I'd been focusing on other topics, so the mastodon hadn't made the cut (for shame on my account!). I am now remedying that omission. For the rest of you who haven't been introduced to the fossil in question, you can also find accounts in Hoff (1969, 2001), which are my primary sources. The Monroe County Historical Association also has a brief online account.

Sunday, March 4, 2018

Jinyunpelta

Ankylosaurs have had a good few weeks, publicity-wise. First we get some actual science done on the long-held belief that they were prone to "bloat and float" (if you don't like to contemplate recently deceased animals, I will simply say yes, it looks pretty good; if you'd like a less-technical summary, go here). We've also now got the oldest record of a true tail club, wielded by the newly minted Jinyunpelta sinensis.

Sunday, February 25, 2018

Rectogloma problematica

What sounds like a kidney disorder, looks kind of like a flattened straight nautiloid possibly with a little curl (or maybe a Devonian Hot Pocket), and remains enigmatic more than a century after its description? It's Rectogloma problematica, which illustrates that even though we're past the Cambrian, the fossil record can still throw some oddballs.

From Van Tuyl and Berckhemer (1914). It's difficult to maintain "natural size" a few generations removed from original illustrations; this is one reason why you should use scale bars instead!

The only reported specimens of Rectogloma problematica were collected by Columbia University students on a field trip to the Delaware Water Gap area. They were found in red shale in the Upper Devonian Catskill Formation in a cut along the Delaware, Lackawanna & Western Railroad near the Henryville station, per Van Tuyl and Berckhemer (1914) ["Henrysville" of their spelling]. The fossils were discovered by Van Tuyl and another student, C. W. Honess, which just goes to show that you should always pay attention on field trips. A couple of the better specimens were collected, and have today made their way into the collections of the American Museum of Natural History (AMNH FI 22377A and B).

The fossils, as illustrated and described by Van Tuyl and Berckhemer (1914) and Conway Morris and Grazhdankin (2005), are a few cm long, roughly rectangular but broader at one end than the other, and have an oval cross-section. They were found oriented vertically, with the wide end pointed up, which as noted by Conway Morris and Grazhdankin (2005) indicates that they are not flattened by compression, but really did have an oval cross-section in life. The broader "sides" are marked with numerous parallel lines 1 to 3 mm apart, each gently arched. Van Tuyl and Berckhemer (1914) described them as "sutures", but they don't go all the way around the fossil. Only one of the two presumed "ends" can be seen in the fossils, so it's not known how the wide end, er, ended. The other end that *can* be seen is also controversial. Van Tuyl and Berckhemer (1914) illustrated a sort of "spit curl" or coil coming off an otherwise rounded termination, but Conway Morris and Grazhdankin (2005) could not confirm this.

Figuring out what Rectogloma problematica is has proven difficult. Van Tuyl and Berckhemer (1914) thought it kind of resembled an abnormal cephalopod, but noted that the incomplete "sutures", lack of a siphuncle, and undivided coil argue against this. (Incidentally, a putative second species, "Rectogloma" zaplensis Turic et al. 1982, did prove to be a nautiloid [Cichowolski 2008].) Knight (1941) noted that it only superficially resembled a gastropod, which is true, but at the same time it's unclear who thought it was a gastropod to start with. Knight instead thought it was more likely a coprolite, which he repeated in 1960 (Knight et al. 1960). While the specimens do indeed appear to be reasonably poop-shaped lumps in basic form, it is rather difficult to produce droppings with smooth sides marked by closely spaced parallel thin features that do not continue all the way around, and a coprolitic identity has been rejected (Häntzschel 1975; Conway Morris and Grazhdankin 2005). Conway Morris and Grazhdankin (2005) did not make any firm classifications; about all they were willing to say was that it may have been "some sort of tube, with a relatively thick wall" of unknown composition. The apparent rarity of Rectogloma fossils and absence of obvious relatives suggest to me that Rectogloma lacked mineralized structures and just lucked out this one time in terms of fossilization. The "sutures" seem more like slits or structural features involved in flexure. Maybe it was some kind of tubular or goblet-like soft-bodied creature, stuck to the sea floor? Or perhaps some kind of fish egg case?

References

Cichowolski, M. 2008. The orthocerid Dawsonoceras? (Nautiloidea) from the Lipeón Formation (Silurian), northwestern Argentina. Ameghiniana 45(4):791–793.

Conway Morris, S., and D. Grazhdankin. 2005. Enigmatic worm-like organisms from the Upper Devonian of New York: an apparent example of Ediacaran-like preservation. Palaeontology 48(2):395–410.

Häntzschel, W. 1975. Treatise on invertebrate paleontology. Part W. Miscellanea. Supplement I. Trace fossils and problematica. Geological Society of America, Boulder, Colorado, and University of Kansas Press, Lawrence, Kansas.

Knight, J. B. 1941. Paleozoic gastropod genotypes. Geological Society of America Special Paper 32.

Knight, J. B., R. L. Batten, E. L. Yochelson, and L. R. Cox. 1960. Supplement. Paleozoic and some Mesozoic caenogastropoda and Opisthobranchia. Pages I310–I331 in R. C. Moore, editor. Treatise on invertebrate paleontology. Part I. Mollusca 1. Geological Society of America, Boulder, Colorado, and University of Kansas Press, Lawrence, Kansas.

Turic, M. A., V. A. Ramos, and J. Oliver Gascón. 1982. "Rectogloma" zaplensis (problemática) de la Formación Lipeón, Provincia de Jujuy, Argentina. Revista del Instituto de Ciencias Geológicas 5.9–14.

Van Tuyl, F. M., and F. Berckhemer. 1914. A problematic fossil from the Catskill Formation. American Journal of Science, 4th series, 38:275–276.

Sunday, February 18, 2018

Identifying invertebrate fossils

Pop quiz! (don't worry, it's not for credit)

Romance *and* brachiopods

Here we have an assortment of fossils, tastefully arranged in a holiday-appropriate setting. They're all the typical local Ordovician stuff, but many Paleozoic shallow marine formations will have a lot of the same general things. What are they, and how can you tell?