A personal indulgence, but then what isn't with a blog? If you've got your copy of Tweet et al. (2012) handy, you'll see that the body of the paper describes 33 National Park Service units where there has been some reference to packrat middens. Two more were added in proof, and didn't get onto the map. I now have references for packrat middens in five additional NPS units, which will be described below, along with new information for one of the units added in press (City of Rocks National Preserve) and an updated map. There's nothing particularly earth-shaking, mostly anecdotal reports, but there's another geographic outlier in Glacier National Park (which can probably use all the climate proxies it can get). In further good news, the USGS/NOAA packrat midden database can once again be accessed, at http://geochange.er.usgs.gov/midden/.
Sunday, September 28, 2014
Sunday, September 21, 2014
Bryozoans make up one of the "B"s of the Decorah BBC (brachiopods, bryozoans, and crinoids), and may be the most abundant; I have seen rocks that are more or less bryozoan hash. Bryozoans are known colloquially as "moss animals", which is fair enough in terms of some of them encrusting things in the manner of carpets of moss, and also being animals. They are often compared to corals, but are quite different. A coral animal is a sack; food goes in and waste goes out the same passage. Bryozoans have a one-way flow with two holes. Coral animals are much larger than bryozoan animals; for example, for the Ordovician fossils of the Twin Cities, coral apertures typically measure several mm across, while the apertures in bryozoan colonies are sub-mm in scale. Finally, bryozoans have never gone in for the algal symbiont trick like corals have done. Not having symbionts, bryozoans must rely on filter-feeding, which the individual bryozoan animals do via a structure called a lophophore, a sort of ring of tentacles around the mouth. This structure is also found in some soft-bodied marine critters with very poor fossil records and the other "B" of the BBC, the brachiopods, showing that they were related, making up a group called the Lophophorata. Various extinct groups known from "worm tubes", like our old friends the cornulitids, may also have been lophophorates.
Sunday, September 14, 2014
No doubt you are sick of hearing about giant sauropods, and another post about Spinosaurus would cause headaches, nausea, and vomiting (if not, there's The Bite Stuff, Skeletal Drawing [one and two], The Theropod Database Blog, and Theropoda [one and two], as well as a bevy of news media accounts). What you need is an ornithopod, and fortunately we have one, a dryosaurid known as Eousdryosaurus nanohallucis by way of the Late Jurassic of Portugal. For those of you not fortunate enough to be an initiate (yet), dryosaurids were modestly-sized bipedal herbivores, mostly legs and tail, on the order of 3 or 4 meters long. Like all modestly-sized bipedal herbivores of an ornithischian persuasion that did not include any unusual skeletal features like frills or domeheads, they were once considered hypsilophodonts. Detailed study and the discovery of more "hypsilophodonts" showed that what we now call dryosaurids were more derived ("advanced", for you time-travelers from the past) ornithopods than most of the "hypsilophodonts", and formed a small knot of Middle Jurassic to Early Cretaceous dinosaurs known mostly from leg and pelvic remains. Dryosaurids as a whole are among the most obscure dinosaurs, being small herbivores with no unusual features. If you run across one in popular media, it's probably there to serve as background filler or carnivore chow. They are not to be confused with the considerably more threatening dyrosaurids, extinct crocodilians that lived from the Late Cretaceous to the Eocene. As if in warning of this, the Paleobiology Database currently has "Dryosaurus phosphaticus" (which ought to be Dyrosaurus) as a species of Dryosaurus. Dryosaurus is the flagship dryosaurid, and if you'd like to spend some time in contemplation of it, you can check the Carnegie Museum of Natural History's page on how they remounted their specimen (previously in a panel mount featuring the classic "bipedal dinosaur standing partially upright like a dope"), or Dinosaur National Monument's page.
|A more naturalistic stance. NPS photo of the Carnegie's new mount.|
Sunday, September 7, 2014
Dinosaur size is something that seems to reduce even otherwise sensible folks to fanboys or fangirls. One of the points that is inevitably addressed in a popular article on a new dinosaur (along with the de rigueur reference to Tyrannosaurus rex) is how big it was. Maybe it was the size of a dog, or a horse, or an elephant. They keep standard elephants in various cities for comparative purposes, just like the old prototype meters. (If a dinosaur is between the size of a dog and about half an elephant, it doesn't get press unless it's got some kind of schtick.) A classic of children's books is "the length of [x number of] school buses". One that seems largely retired is "could look into a [x]-story window". If you are familiar with the nuts and bolts of Wikipedia, and ever go spelunking under the "history" tab of dinosaur articles, you'll find that one of the most common sequences of edits is someone wedging an extra meter or five tons into a size estimate, followed by someone reverting them. You might think that these measurements are pretty darn solid and reliable, for all the passion they inspire. Well...
|"Faster than a beer-league softball player! More powerful than the disapproval of your peer group! Longer than the average school bus! Able to look into second-story windows without straining itself!"|