Monster mouse

Blogging on Peer-Reviewed Research

The capybara is the current champion for rodents of unusual size — it weighs about 60kg (about 130 pounds); another large rodent is the pakarana, which weighs about a quarter of that. Either one is far too much rattiness for most people to want hanging around.

Now there’s another king of the rodents: Josephoartigasia monesi, which is estimated to have tipped the scales at about 1000kg, over a ton. Don’t worry about getting bigger rat traps; these beasties have been extinct for perhaps 2 million years. I’ve put a few pictures from the paper describing this new species below the fold.

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Load-bearing adaptation of women’s spines

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Blogging on Peer-Reviewed Research

Those of you who have been pregnant, or have been a partner to someone who has been pregnant, are familiar with one among many common consequences: lower back pain. It’s not surprising—pregnant women are carrying this low-slung 7kg (15lb) weight, and the closest we males can come to the experience would be pressing a bowling ball to our bellybutton and hauling it around with us everywhere we go. This is the kind of load that can put someone seriously out of balance, and one way we compensate for a forward-projecting load is to increase the curvature of our spines (especially the lumbar spine, or lower back), and throw our shoulders back to move our center of mass (COM) back.

Here’s the interesting part: women have changed the shape of individual vertebrae to better enable maintenance of this increased curvature, called lordosis, and fossil australopithecines show a similar variation.

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Jaekelopterus

If you’ve been following Lio lately, you know he has a new arthropod friend, rescued from the dinner pot.

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Unfortunately, Lio missed the big news.

The fossil record has yielded various gigantic arthropods, in contrast to their diminutive proportions today. The recent discovery of a 46cm long claw (chelicera) of the pterygotid eurypterid (‘sea scorpion’) Jaekelopterus rhenaniae, from the Early Devonian Willwerath Lagerstätte of Germany, reveals that this form attained a body length of approximately 2.5m–almost half a metre longer than previous estimates of the group, and the largest arthropod ever to have evolved. Gigantism in Late Palaeozoic arthropods is generally attributed to elevated atmospheric oxygen levels, but while this may be applicable to Carboniferous terrestrial taxa, gigantism among aquatic taxa is much more widespread and may be attributed to other extrinsic factors, including environmental resources, predation and competition. A phylogenetic analysis of the pterygotid clade reveals that Jaekelopterus is sister-taxon to the genus Acutiramus, and is among the most derived members of the pterygotids, in contrast to earlier suggestions.

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This isn’t some casual graspy sort of claw, either—it’s a great spiky wicked looking claw, with pointy daggery bits sticking out that make it look like some medieval weapon of terror.

This is a much more Lio-like creature than the dainty little bug in the cartoon. I wouldn’t mind having one of these for a pet myself! It’s too bad they’ve all been dead for 390 million years.

Braddy SJ, Poschmann M, Tetlie OE (2007) Giant claw reveals the largest ever arthropod. Biology Letters doi:10.1098/rsbl.2007.0491.

Nigersaurus, a Cretaceous hedge-trimmer

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Last August, when I was at the Sci Foo camp, Paul Sereno brought along the skull of one of his latest discoveries…and whoa, is it ever a weird one. This is Nigersaurus taqueti, an herbivorous dinosaur with specializations for ground-level grazing. Look at this picture; in reality, it’s even more striking.

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Those jaws and teeth—they are so neatly squared off and flat-edged. In addition, the skull itself on the spinal column is turned habitually downward. This is a creature that kept its face pressed to the ground as it nibbled its way across the landscape.

Another feature that was apparent is that the skull is awesomely light — it’s mostly empty spaces with a delicate webwork of bony struts holding it together. It’s so specialized it’s almost comical, and you can imagine something like this appearing on the Flintstones as a lawn mower or hedge trimmer.

Bora has more, and you can read the original on PLoS.

Sereno PC, Wilson JA, Witmer LM, Whitlock JA, Maga A, et al. (2007) Structural Extremes in a Cretaceous Dinosaur. PLoS ONE 2(11): e1230. doi:10.1371/journal.pone.0001230

Yicaris dianensis

Blogging on Peer-Reviewed Research

Early Cambrian shrimp! I just had to share this pretty little fellow, a newly described eucrustacean from the lower Cambrian, about 525 million years ago. It’s small — the larva here is about 1.8mm long, and the adults are thought to have been 3mm long — but it was probably numerous, and I like to imagine clouds of these small arthropods swarming in ancient seas.

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The head limbs are drawn in median view and the trunk limbs in lateral view.

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Lucy’s legacy

As I’ve mentioned before, Lucy is going to be in Houston at the end of this week for an extended stay. This is not entirely a joyous occasion in the scientific community: many people, including Richard Leakey, are not happy that such a precious specimen has been subjected to the risks of travel. I sympathize. The bones of Lucy must be treated with the utmost care and regard, and any loss or damage would be an awful tragedy. However, there’s more to it than preserving an important fossil: Lucy is a touchstone to our past and is a symbol of the importance of our long history. We need to bring the ancient world to life for our citizens, and for not entirely rational reasons, people will want to see the real thing. I see that someone else shares my sentiment:

There is a wanton arrogance alive and kicking within the general scientific community. An arrogance that clings stubbornly to fact while at the same time stridently denying reality. And it pisses me the hell off. The facts in this case are clear: Lucy is one of the oldest hominid fossils ever discovered, and is very valuable for researchers. The reality of the situation is equally clear-cut, if a bit harder for the critics to swallow: Nobody gives a shit about replicas. Does it look the same? Sure. Can 99.9 percent of the population not tell the difference? You betcha. Does that matter? Not one iota. You see, for all the cranial capacity human beings have developed since little Lucy made do with a glob of gray matter the size of a key lime, we are not rational thinkers. Homo sapiens are, first and foremost, irrational and emotional.

I wouldn’t go so far as to call it arrogance, but there is a little selfishness to it, and most importantly, there’s a deep appreciation of the importance of that long-dead individual and a greater fear of its loss. What balances that fear, though, should be the recognition that other people could also stand to learn to love that tiny scrap of our long-past ancestry — the Lucy exhibit is an opportunity to teach.

Shouldn’t that be part of our mission? In addition to our own intimate learning of science, the task of sharing it with everyone else?