Packrat middens across (parts of) America: update to Tweet et al. 2012

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/.

Bryozoans

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.

Eousdryosaurus

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.

On this occasion of receiving a new giant dinosaur: thinking about dinosaur size estimates

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!"

The Amazing Four-Sided Herringboned Ice Cream Cone (with creamy polyp center?)

The farther back you go, the less familiar the lifeforms. Obvious, no? And yet the pattern is not a simple one to one relationship. For example, the Cambrian was a relatively brief time in which the invertebrates collectively decided that "anything goes" and did their darnedest to fulfill that maxim. Many groups didn't hack it and disappeared before the Ordovician. From the Ordovician to the Permian, the shallow seas were filled with bryozoans, brachiopods, and crinoids, with growing numbers of rugose and tabulate corals, mollusks, and fish. The dominant groups of the Paleozoic were greatly reduced or wiped out altogether at the end of the Permian. Almost all of the enigmatic or otherwise difficult-to-classify groups kicked the bucket by the Permian–Triassic extinction, with a few exceptions such as the bellerophont snails (or monoplacophorans), the conodonts, and today's entry, which all persisted into the Triassic for reasons known only to them. The post-Cambrian bryo-brach-crinoid seafloor communities were replaced by Mesozoic communities dominated by mollusks, stony corals, echinoids (sea urchins), and cartilaginous and bony fish. With the end-Cretaceous subtraction of the ammonites, belemnites, certain groups of bivalves, and marine reptiles, and the addition of marine mammals, this becomes the typical modern marine assemblage. Today, many of the extinct Paleozoic groups appear strange, which is a bit unfair because they were just being the best filter feeders/detritivores/algal symbionts they could, and because there are plenty of unusual things alive in the ocean this very instant. Some of them, however, seemingly went out of their way to stand out. One example follows below the fold.

Corals of the Twin Cities

The Ordovician seas of the Twin Cities would have been unfamiliar in a lot of ways. There were no sharks, no bony fish, no marine mammals, no seabirds. No driftwood bobbed in the water. There were no octopuses or true squids, no lobsters or crabs scuttling about. The kings of the echinoderms were not sea stars, brittle stars, and sea urchins, but crinoids. A diver would see a Lilliputian sea-scape featuring cm-scale brachiopods, profusions of bryozoans, and "forests" of sea lilies, traversed by trilobites. Snails, of course, would provide a common point of reference. "Are there no corals?" you ask, thumbing through your waterproof guidebook as you try to figure out if you have just stepped on an inarticulate brachiopod, a bivalve, or a monoplacophoran. Well, yes, there are corals; it's just they are all representatives of groups that have been extinct since the end of the Permian (that pesky Permian–Triassic extinction).

Chuanqilong and Tambatitanis

So I finish the Generic History of Dinosaur Paleontology series on July 20th, and four new genera come along. Of course, it's not quantity but quality, and a year with Anzu and Kulindadromeus will be remembered fondly. Every dinosaur should have its day, though, even if they aren't enormous crested caenagnathids or feathered ornithischians. Two of the most recent genera are in freely accessible publications and represent significantly different but still generally overlooked branches of the dinosaurian tree. They are the titanosauriform sauropod Tambatitanis and the ankylosaur Chuanqilong.