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National Fossil Day Post #2: The Most Common Fossils of Arkansas

NFD_2015_Oval

NFD_2015_Oval

National Fossil Day is today. The Museum of Discovery is having their second annual National Fossil Day event this Saturday. In celebration of these events, I am reviewing important fossils of Arkansas. Last post I stated my picks for the most famous fossils of Arkansas. This time I will discuss what I think are the most common fossils in particular regions of the state.

crinoidal-imo-faceIn the Ozarks, you can find an abundance of marine fossils. There are ammonoids, bryozoans, brachiopods, clams, corals, echinoids, and many others. The Pitkin limestone is so chocked full of Archimedes bryozoans that it is sometimes referred to as the Archimedes limestone. But overall, I have to go with crinoids as the most commonly found fossil in the Ozarks. Crinoids lived throughout the Paleozoic Era, making them potential finds throughout the region. They survived even up to the present day in deep marine settings, but in the Paleozoic, they lived throughout the shallow marine realm, which is where fossils are most common.

Stellar examples of crinoids in all their fossilized glory. This image and more information can be found at www.ucmp.berkeley.edu/echinodermata/crinoidea.html

Stellar examples of crinoids in all their fossilized glory. This image and more information can be found at http://www.ucmp.berkeley.edu/echinodermata/crinoidea.html

Known as sea lilies today due to their plant-like appearance, they are actually echinoderms, making them relatives of sea urchins and sea stars. While not common today, they were quite abundant during the Paleozoic. Most of the fossils of crinoids are of their stems, which look like stacks of circles with the centers punched out, sort of like flattened rings. But occasionally, you can find the tops of the crinoids with the body (called a calyx) and the arms still intact. These are rare because, like all echinoderms, the body is made of plates that fall apart into indistinguishable fragments shortly after death.

Graptolites from the Womble shale. www.geology.ar.gov

Graptolites from the Womble shale. http://www.geology.ar.gov

DSC_1582You will not find many fossils in the Ouachitas, but two types of fossils are commonly found there, conodonts and graptolites. Conodonts are the toothy remains of the earliest vertebrates. Unfortunately, you can place several of them on the head of a pin, so unless you are looking at rocks under a microscope, you probably won’t see them. That leaves graptolites, which can be found in several places fairly easily. Unless you know what you are looking at, they can be easy to miss. On black shale, they often appear as pencil scratches that are easy to overlook. But look closely and you will see that many of them look like tiny saw blades. These are what remains of animals we call today pterobranchs. These animals are the closest an animal can get to being a chordate, the group that includes vertebrates, without actually being one. So the Ouachita mountains have fossils that bracket that hugely important transition from spineless to having a backbone.

exogyraFor the third choice, one could always argue for shark teeth, which are commonly found in southwest Arkansas, but can be found most anywhere in the state. But if we limit our discussion to the southwest part of the state, the easiest to find on the basis of quantity and size I think has to go to Exogyra ponderosa. These are Cretaceous aged oysters known for their thick shells adorned with a curled hornlike shape. They are big, sturdy, and can be found by the thousands. One can only imagine that the Cretaceous was a great time to be an oyster. At that time, southwest Arkansas was beachfront property. with lots of shoreline and shallow marine deposits of sand, shale, limestone, and the famous Cretaceous chalk deposits. Dinosaurs walked along the beach, marine reptiles like mosasaurs and elasmosaurs plied the waters, along with sharks and fish of all kinds. And between them lay mountains of oysters.

You may notice that I left out pretty much all of eastern Arkansas. That is because that region of the state is covered in fairly recent Mississippi river sediment, so you don’t find that many fossils in that part of the state. Some have been found, such as the Hazen mammoth, mastodons, sea snakes, and the occasional giant ground sloth or whale, but the fossils are few and far between. So while they have several fascinating fossils, they aren’t going to show up on anyone’s list of commonly found fossils.

So those are my choices. Do you have other suggestions?

National Fossil Day in 3 Days

Here are some brachiopods you will see at the National Fossil Day event. They look much like clams, but are unrelated.

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Here are some bryozoans, which look like they should be related to coral, but are thought to be more related to brachiopods because they share the same odd feeding structure.

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Speaking of corals…

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and a sponge, among other things.IMG_20140822_150020

Mystery Monday and Walking With Dinosaurs Movie Review

Mystery Monday

Last Friday I posted clues to a mystery fossil. The clues were 1) I lived in AR during the Mississippian Period roughly 330 million years ago and am a very common fossil to find here. 2) Many people think I’m a coral, but I’m not. 3) I am named after a famous Greek mathematician and inventor. Who, or more precisely, what am I? Allie Valtakis got the right answer as the bryozoan, Archimedes.  Here is what the Arkansas Geological Survey says about it.

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The Bryozoa grow attached to the sea-floor as do corals, but they differ significantly from corals in terms of soft-part anatomy.  The bryozoans are exclusively colonial and fall into two broad groups, the lacy colonies and the twig-shaped colonies.  Individual “houses” (zooeciums) lack the radial partitions found in corals, but they are divided transversely by partitions called diaphragms (Fossils of Arkansas).  Bryozoans can also grow as incrustations on the shells of other organisms and are commonly associated with reef structures.

“Bryozoans are tiny colonial marine animals that are present in marine and fresh water today.  They are sessile benthonic animals (fixed to seabed) that are filter feeders and prefer shallow seas, living fairly close to shore (neritic).  One bryozoan called Archimedes (see picture below) is abundant in Mississippian age rocks in Arkansas and is so plentiful that one of the rock formations called the Pitkin Limestone was once referred to as the “Archimedes Limestone”.  Generally, only small pieces of bryozoans that resemble “fronds” are preserved in Mississippian and Pennsylvanian age rocks in the Ozark Plateaus Region.

References:

Freeman, Tom, 1966, Fossils of Arkansas:  Arkansas Geological Commission

Bulletin 22, 53 p., 12 pls., 15 figs., 1 map.

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Archimedes “fronds”

Way to go, Allie!

Can you guess this week’s fossil? I will do things a bit differently this time. Unlike previous fossils, in which I told people on the Facebook page as soon as someone provided the correct answer, I will not reveal the answer until Friday, so you have plenty of time to give it a try. In addition to the picture (note the scale) below, I will provide one clue every day until Friday. Good luck!

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Clue 1: It’s from the Cretaceous.

Clue 2: It’s modern day relatives are widely considered a delicacy.

Clue 3:  This is no wilting lily. This creature is big and bold. It shows how twisted it is on the outside for all the world to see. Dude, that’s heavy.

Come back tomorrow for the answer! You can also find it on the Facebook page.

 

Walking with Dinosaurs 3D movie review

I went to see Walking With Dinosaurs 3D this weekend. My kids were interested in seeing the movie and I liked the BBC “Walking with Dinosaurs” TV mini-series, so we were all eagerly anticipating the movie. I had read a few reviews of the movie, some by paleo people, who said the dinosaurs were great, but the voices were terrible, which gave me pause, but it’s a BBC movie on dinosaurs, how bad could it be, right?

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Sadly, not like this.

Sad to say, I have to agree with most of the reviewers. This movie may be much more enjoyable if you can’t hear it. To begin with, whatever expectations you may have, forget them. If you are going in expecting to see a big screen version of the BBC “Walking with Dinosaurs,” you will be disappointed by the cartoon voices and plot. If you are looking for light entertainment for little kids, you might be a bit surprised by the rather jarring breaks providing a subpar, documentary-style educational interlude which will kick everyone out of the story.

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More like this, but with better graphics.

The film reminded me nothing so much as a cross between the BBC documentary-style series and The Land Before Time movie series, failing at both. I think the reason for this is because it seemed to clearly start off with the idea of it being a kid-friendly movie along the lines of the TV series, but some executive decided after it was made that it was not going to draw enough kids. So the movie was recut and really bad dialogue added to it instead of the normal narration one would expect in a nature documentary, along with completely superfluous modern scenes bookending the film, wasting the talents of otherwise fine actors. The voices were obviously added as an afterthought because the dinosaurs do not act like they are speaking. I could even occasionally hear the original dinosaurian bleating and honking in the background even as they are supposedly talking. The dialogue, as Brian Switek noted in his review, destroyed any emotion that may have been evoked by the scenes that were supposed to be emotionally powerful. What should have been poignant, heart-tugging scenes were drained of any impact by juvenile pratterings that never ceased. I found myself wishing for the dinosaurs to just shut up once in a while. As a result, it is a movie that may be enjoyable for a little kid, but eminently forgettable. Bambi was a much more riveting emotional experience, not to mention more educational about the lives of deer.

The story line was inconsistent with the idea of a nature documentary and a poor choice for a dinosaur movie. Whether or not the worst aspects of it were in the original script, I don’t know, but the final plot, while suitable for a cartoon Land Before Time, was wholly inappropriate for a nature “fauxmentary.” For a film that was supposedly educational, it pushed moral viewpoints which are only valid in human cultural environments and completely invalid in the natural world. The idea that intelligence and courage will overcome the thoughtless, testosterone-fueled belligerence of the larger alpha males is a noble sentiment and may work in a human context, but not in the depicted dinosaur society. Control of a herd of large herbivores that have evolved extravagant displays will never pass to the runt of a litter because he saves the herd in a time crisis due to his quick thinking. The plot line for the movie is far more appropriate to an after-school special involving actual, human children, not dinosaurs. As such, it completely destroys any educational effectiveness of the movie. The only education that remains is that dinosaurs lived in a snowy Alaska and that some dinosaurs had feathers, particularly the smaller theropod carnivores. I really like this aspect of the movie, but its authenticity in these aspects was completely undermined by the silliness of the rest of the movie.

To make it even more confusing in terms of genre plotting, the movie shows that females in the herd are dominated by the alpha male, but glosses over what that means in terms of sexual dominance. In a kid-based movie, this understandably only goes as far as hanging out with each other. In the natural world (and post-adolescent human worlds), as every adult in the audience will understand, it means the female submits to the alpha male’s sexual advances. In terms of a human kid’s movie, it sends very poor messages about the role of females in society. In terms of an educational nature show, it is intentionally misleading to spare the typical parental sensibilities of what is appropriate for kids to see.

In short, if you go to see this movie (which I would really recommend waiting until a rental, as it is not worth spending the price for a 3D movie), go expecting to see a mindless 80 minutes of passable, but forgettable, entertainment for children with no real educational value other than to say look, aren’t dinosaurs neat? Enjoy the graphics, ignore the rest.