Monthly Archives: September 2012

Earthling Bulletin #9

by Piter Kehoma Boll

Lesula (Cercopithecus lomamiensis) the newly discovered monkey with a disturbing-to-look-at human-like face. Photo by Maurice Emetshu.

News

Blog

Art

I had no particular art works to post this month, so I made some random search on deviantART and found some interesting paintings and I thought they would be worth sharing!

Books

Scientific Articles

(If you are willing to read some of the articles but got no access to them, please contact us and we’ll send you a copy through e-mail!)

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Review: Dinosaur Art – The World’s Greatest Paleoart

By Carlos Augusto Chamarelli

Hey everybody, PK here once more. It was LONG time since my last proper article, but it’s not like my life (or yours) exist solely around EN. I, for one, enjoyed the break. Today I’m here to review one of the spotlights of the year for dinosaur publications; like other dinosaur blogs out there EN was granted the chance to receive and review Dinosaur Art – The World’s Greatest Paleoart by Titan Books, containing the artwork of 10 contemporary paleoartists ranging from veterans like Gregory Paul and John Sibbick to newcomers like John Conway and Julius Csotonyi.

It was originally going to be a collaboration post with RSN, but since the mail agencies in Brazil went on strike (which is pretty much the standard situation at this point), his copy might take some more time to arrive*, so I’ll just go on and make my review solo so I don’t disappoint anyone.

Giant crocodiles are dinosaurs too.

Right off the bat I can say the cover is a good indicative of the quality level the book offers, with a gorgeously detailed and a now somewhat classic scene of a supercroc attacking a dinosaur in the dustcover, in this case, Deinosuchus and Albertosaurus, by Raul Martin. While he’s certainly one of the best choices of cover for this book (as opposed to… I’ll talk about him in due time). It strikes me as odd though because the scene seems to emphasize the crocodile more. It’s DINOSAUR Art after all, and the star is about to be eaten by his humongous cousin.

But hey, that’s just the dust jacket. Removing it will reveal two superb illustrations in negative: on the front there are two Homalocephale skeletons fighting by John Sibbick, and a group of Albertosaurus, one Edmontonia, one Edmontosaurus and what seems to be a Velociraptor super-jumping above them in the back by Julius Csotonyi. I thought it looked beautiful in the glossy-black paper and deserved to be shared.

The dinosaurs gather around the Mesozoic monolith.

The text about the history of paleontology and paleoart is relatively short, or may feel so despite spanning through four pages, three columns each, but the reading is so fluid that you’ll be at the end before you notice. That’s not to say it’s bad, I really liked it and thought it did a good job in giving a little of backstory about the changes in our views on dinosaurs and the mission paleoartists are tasked with in a concise manner.

Each artist interview has a collection of pictures that in some cases occupies the entire page, some are two-page spreads, and some even have folding pages that open to reveal a much grander scene. From sketches and studies to museum murals depicting various species together, the quality of the pictures is also impressive: most of them you find around the internet, but see, their resolution make them no justice since you can’t see the finer details that compose it as they appear in the book. I mean, just looking at the cover with the Deinosuchus, a picture so easily found by googling it, I realize that even the higher resolution available fails miserably to show the level of quality the picture really possess.

The Cretaceous was pretty in spring. Troodons under magnolia, picture by John Conway.

In the interviews we get to know about the artists own history, from the first attempts at drawing dinosaurs with nothing but a pencil, paper and loads of child-like imagination to the pursuit of professional career (with art being or not their main goal), their opinions on different media and the adaptation to the digital tools, influences and opinions of their approach in their own work. Along the interviews there is usually a profile for a specific creature that’s important for the artist in question (i.e. Giraffatitan for GSP, Smilodon for Mauricio Antón), but they’re unfortunate for being placed right in the middle of the interview, messing with the reading flow.

Glad to see prehistoric mammal still count as “dinosaurs”. Smilodons and Columbian Mammoths, picture by Mauricio Antón.

Now, I was going to make a more elaborated critique on each artist, but I decided it would take too much time and/or delay this review even further than it needs to be, so I might still do it as a separated post, so for the time being I’ll just say I feel disappointed about the choice of one of them: Todd Marshall.

I mean, I can see the reasons he probably was included. I know about some complaints about many other great paleoartists like Mark Hallet and Larry Felder who were left out of the books, but I understand this was probably done because the book focus more in contemporary paleoartists, and we don’t hear much, if at all, from these artists nowadays; Peter Schouten is also a notably absence despite still active, but that could be because (much for RSN’s utter disgust) he’s comparatively more of obscure and very much underappreciated. Even though they included this Robert Nicholls person who I’ve never heard about before (but I was pleased with his work nonetheless). Still, I’m not much of a fan of Marshall’s reconstructions since I think they aren’t on par with the rest, I definitely wouldn’t have included him. Well, more on this on the later post.

In closing words, considering the overall quality of a book this size with high-resolution illustrations in high quality paper (man, that paper), it’s absolutely great value for money (but that could just be me since it would cost over 200 bucks if it was ever released in Brazil) and a real treat for anyone who’s into dinosaurs or is yet to discover is into dinosaurs.

Just go and see it for yourself, it’s really worth it!

Reenactment of The Matrix included. Sinusonasus fighting. Picture by Luis Rey.

* As I wrote this the strike seems to have ended, but they still might delay the delivery. Efficiency.

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Why thymine instead of uracil?

by Piter Kehoma Boll

ResearchBlogging.org About a year ago, while I was in my class of Techniques of Molecular Diagnosis, an interesting doubt sprouted: why does DNA use thymine instead of uracil as RNA does?

I hope everybody reading this knows about nucleic acids and the difference between DNA and RNA. As a very quick review:

RNA (ribonucleic acid) is a polymer made of ribonucleotides, compound molecules made of three parts, or smaller molecules: a nitrogenous base (adenine, uracil, cytosine or guanine), a ribose sugar and a phosphate group.

DNA (deoxyribonucleic acid) is similar, but instead of uracil it has thymine, and instead of a ribose sugar is has a deoxyribose, so that it is made of deoxyribonucleotides. Another difference is that DNA is a double chain twisted helicoidally, where two nitrogenous bases (each from one of the chains) are connected. Adenine is always connected to thymine and cytosine always to guanine, so that one chain is always dependent on the other.

Currently it’s highly accepted that RNA was the first nucleic acid to exist and that DNA evolved from it, so the changes in the sugar and one of the nitrogenous bases must have some advantage.

To understand that, let’s take a look at the structure of the uracil:

Uracil

The only difference between it and thymine is the presence of a methyl group thymine:

Thymine

In fact, thymine is also called 5-methyluracil. But let’s go to the explanation:

While nucleotides are synthesized, the nucleotide-monophosphates (NMPs), i.e., the set nitrogenous base + sugar + phosphate is dehydroxylated, creating 2’-deoxy-nucleotide-monophosphate (dNMPs), i.e., GMP, AMP, CMP and UMP (for guanine, adenine, cytosine and uracil) are changed to dGMP, dAMP, dCMP and dUMP.

This modification by dehydroxylation has been shown to make the phosphodiester bonds (the bonds of phosphates on the sugar) less susceptible to hydrolysis and damage by UV radiation. It assures that a DNA molecule will not be as easy to be broken as an RNA molecule, which is very useful since DNA carries all the information to build up the organism.

After the dehydroxilation of the nucleotide-monophosphates, the next step, catalyzed by folic acid, add a methyl group to the uracil to form a thymine, so turning dUMP into dTMP.

There are many explanations for that:

1. Despite uracil’s tendency to pair with adenine, it can also pair with any other base, including itself. By adding a methyl group (which is hydrophobic) and turning it into thymine, its position is reorganized in the double-helix, not allowing those wrong pairings to happen.

2. Cytosine can deaminate to produce uracil. You can see in the picture below that the only difference between them is the change from an O in uracil to an NH2 in cytosine. The problem is that, if uracil were a component of DNA, the repair systems would not be able to distinguish original uracil from uracil originated by deamination of cytosine. So using thymine instead makes it way easier and more stable, as any uracil inside DNA must come from a cytosine and so it can be replaced by a new cytosine.

Cytosine

This didn’t evolve for that purpose, of course. Evolution cannot predict what happens. Probably during the earliest times of life, eventually an error changed uracil for thymine and it was found to be more stable to carry information, since such a molecule wouldn’t be destroyed so easily and thus would succeed in passing its “layout” to the next generation.

It makes me wonder… Could some alien life form have found an alternative way to deal with RNA’s (or something equivalent) instability?

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Main Reference:

Jonsson, J. (1996). The Evolutionary Transition from Uracil to Thymine Balances the Genetic Code Journal of Chemometrics, 10, 163-170 DOI: 10.1002/(SICI)1099-128X(199603)10:2

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Filed under Evolution, Molecular Biology

Friday Fellow: Cramer’s Eighty Eight

by Piter Kehoma Boll

ResearchBlogging.orgThis Friday I’ll talk about one of the most charismatic species of butterflies, at least here in Southern Brazil. Diaethria clymena, known as Cramer’s Eighty Eight or simply 88 Butterfly, is a small species which features a pattern of black and white spots and stripes on the underside of the back wings that look like a number 88. Its distribution goes from Guatemala to Southern Brazil and there are several subspecies through its range.

Male (?) Diaethria clymena meridionalis in Floresta Nacional de São Francisco de Paula, Southern Brazil. Photo by Piter Kehoma Boll.*

Adults of this species are often seen near fruit trees, being attracted by rotting fruits. Males can also be seen near ponds, streams or even urine-soaked sand, searching for dissolved minerals to consume.

Larvae of this species often feed on plants from genus Trema (family Cannabaceae), something unusual, since most of the closely related butterflies feed on Sapindaceae. The last larval instars, with a green color, just like the following crysalid, have two long spiny “horns” at the anterior end and when disturbed start to move their head rapidly from side to side.

Despite being a rather common species often found near human settlements, it’s not that well known concerning its ecology and physiology.

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References:

Barbosa, E. P., Kaminski, L. A., & Freitas, A. V. L. 2010. Immature stages of the butterfly Diaethria clymena janeira (Lepidoptera: Nymphalidae: Biblidinae). Zoologia, 27 (5), 696-702 DOI: 10.1590/S1984-46702010000500005

Learn about Butterflies. “88 Butterfly”. Available at: <http://www.learnaboutbutterflies.com/Amazon%20-%20Diaethria%20clymena.htm>. Access on September 7, 2012.

Wikipedia. Diaethria clymena. Availabe at: <http://en.wikipedia.org/wiki/Diaethria_clymena>. Access on September 7, 2012.

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