Eophyllium messelensis

Any other fans of the Phasmatodea out there? For years, we kept a collection of stick insects — they are extremely easy to raise, and although they aren’t exactly dynamos of activity, they’re weird enough to be entertaining — and so I perk up when I notice a paper on them. The latest news is the discovery of a fossil leaf insect (also a member of the Phasmatodea, but a smaller subgroup specialized to resemble leaves rather than twigs) from 47 million years ago that resembles modern forms very closely. The cryptic camouflage of this group is ancient, and probably coevolved with the emergence of angiosperms.

Here’s the specimen.

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Photo (A) and line drawing (B) of holotype of fossil leaf insect E. messelensis gen. et sp. nov. from the Eocene Messel Pit, Germany (MeI 12560). a3–a10, abdominal segments 3–10; ant, antennae; cer, cerci; fl, foreleg; fw, forewing; hl, hindleg; hw, hindwing; int, intestinal tract; ml, midleg; vom, vomer.

In case you were wondering about relationships, here’s a very nice cladogram. One other detail is that there are about 3000 species of phasmids with the stick form, but only 37 that are leaflike, and all are confined to Southeast Asia; this fossil was found in Europe, where no such species are native.

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E. messelensis gen. et sp. nov. in evolutionary and biogeographical context. (A) Simplified cladogram with a partial geochronologic scale showing the phylogenetic position of E. messelensis and the temporal sequence of character evolution. Oldest fossil records of determined adult representatives of Timematodea and Euphasmatodea are depicted. M, Messel fossil site; B, Baltic Amber. Dating of splitting events of crown-group Phasmatodea is unknown. Euphasmatodea represent an unknown number of lineages. Figures are not to scale. (B) Distribution of extant and fossil leaf insects.

Now I’m pining for our old insect pets — we had to leave them behind in one of our many moves. Anyone want to mail me some phasmid eggs?

Wedmann S, Bradler S, Rust J (2007) The first fossil leaf insect: 47 million years of specialized cryptic morphology and behavior. Proc Nat Acad Sci USA 104(2):565-569.

Doushantuo embryos dethroned?

Almost ten years ago, there was a spectacular fossil discovery in China: microfossils, tiny organisms preserved by phosphatization, that revealed amazing levels of fine detail. These specimens were identified as early animal embryos on the basis of a number of properties.

  • The cells were dimpled and shaped by adjoining cells, suggesting a flexible membrane—not a cell wall. This rules out algae, fungi, and plants.
  • The number of cells within each specimen was usually a power of 2. This is something we typically see in cleaving embryos, the sequence from 1 to 2 to 4 to 8 to 16 cells.
  • They were big. Typical somatic cells in animals are 5-10 µm in diameter, but ova can be a millimeter or more in diameter, and individual blastomeres (the cells in the cleavage stage embryo) can be several hundred µm across. These cells and the whole assemblage were in that size range.
  • The individual cells were uniform in size, as seen in many cleavage stage embryos, and contained organelles arranged in a consistent pattern.
  • They were often found encapsulated in a thin membrane, similar to the protective membrane around embryos.

There are some concerns about the interpretation, though. One troubling aspect of their distribution is that they are all only in the cleavage stage: we don’t see any gastrulas, the stage at which embryonic cells undergo shape changes and begin to move in a specific, directed manner. Studies of taphonomy (analyses of the processes that lead to fossilization) have shown that these later stages are particularly difficult to preserve, which potentially explains why we’re seeing a biased sample. Another unusual bias in the sample is that all of the embryos exhibit that regularity of division that produces equal-sized blastomeres—yet many invertebrate embryos have early asymmetric cleavages that produce recognizable, stereotyped distributions of cells. That asymmetry could be a feature that evolved late, but at the same time, some of the fossils were described as resembling molluscan trefoil embryos. Why aren’t the examples of early asymmetry translated into a later asymmetry?

Now there’s another reason to question the identity of the Doushantuo microfossils: they may be bacterial.

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Turiasaurus

Oh, man, I feel for the kids nowadays. When I was an itty-bitty dinosaur-happy tyke, it seemed like there was a manageable amount of Latin nomenclature you had to memorize to keep up with the dinosaur clan. Now it’s like there’s a new one added every week, and you’ve got to be a freakin’ genius to be able to follow them all. Kids do still go wacky over dinosaurs, right? We haven’t gone so far down the tubes that the little nerds are neglecting their paleontology, have we?

Anyway, there’s a new one out of Spain, Turiasaurus riodevensis, an old school sauropod, and it’s a big one. Pictures below the fold…

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Volaticotherium antiquus

This sad jumble of bones is all that remains of Volaticotherium antiquus, a small rat-sized mammal that was recently dug up in China. There are two particularly outstanding things about this creature.

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One is that browner layer in the rock: that isn’t an artifact, it’s a bit of soft tissue that was preserved, called a patagium. A patagium is a thin membrane stretched between the limbs, and is used for…flying! This animal probably lived much like a modern flying squirrel (although it is definitely not a squirrel), gliding from tree to tree.

The second surprise is the age. This is a Mesozoic mammal, from Chinese beds that are roughly dated to somewhere around the mid Jurassic to early Cretaceous—it was a contemporary of the dinosaurs. I’m tickled to imagine a diplodocid stretching up its long neck to strip the foliage from a tree branch, and this little guy squeaking angrily and leaping off to fly to the next tree.

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Now one more thing we need, but are extremely unlikely to find, is a Mesozoic moose.

Mang J, Hu Y, Wang Y, Wang X, Li C (2006) A Mesozoic gliding mammal from northeastern China. Nature 444:889-893.

Evidence is always the best way to resolve a debate

You know how we great clumsy gallumphing unsophisticated atheists are always comparing belief in gods to belief in fairies at the bottom of the garden or tooth fairies or whatever? We may have to revise those arguments.

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Now we really have to worry. If some space probe snaps a picture of an orbiting teapot, we’ll have nothin’.

Crap. Sean knocks the props out from under my godlessness. Now I’m going to have to convert to something…what does everyone recommend? Catholicism, LDS, Scientology, etc., or should I just go all the way primitive, erect a phallus-shaped rock in my backyard, and start worshipping that?

The Cambrian as an evolutionary exemplar

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I’ve been reading Valentine’s On the Origin of Phyla(amzn/b&n/abe/pwll) lately, and I have to tell you, it’s a hard slog. This is one of those extremely information-dense science texts that rather gracelessly hammers you with the data and difficult concepts on page after page. I am convinced that James W. Valentine is ten times smarter than I am and knows ten thousand times as much, and it’s a struggle to squeeze that volume of knowledge into my miniscule brain pan.

One thing I would like to greatly condense and simplify is his discussion of the Cambrian ‘explosion’. Misinterpretation of the Cambrian is one of the many prongs of the creationist assault on science; both old school Biblical creationists and the new stealth creationists of the ID movement have seized upon it as evidence of an abrupt creation—that a Designer poofed the precursors to all modern forms into existence suddenly, and without precursors, and that this observation contradicts evolutionary theory.

It doesn’t. Valentine has an excellent diagram that shows how wrong the creationists are.

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The sea urchin genome

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Oh happy day, the Sea Urchin Genome Project has reached fruition with the publication of the full sequence in last week’s issue of Science. This news has been all over the web, I know, so I’m late in getting my two cents in, but hey, I had a busy weekend, and and I had to spend a fair amount of time actually reading the papers. They didn’t just publish one mega-paper, but they had a whole section on Strongylocentrotus purpuratus, with a genomics mega-paper and articles on ecology and paleogenomics and the immune system and the transcriptome, and even a big poster of highlights of sea urchin research (but strangely, very little on echinoderm development). It was a good soaking in echinodermiana.

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A Devonian lamprey, Priscomyzon

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Reconstruction of Priscomyzon in dorsal (top) and left lateral (bottom) views. b, Macropthalmia stage of Lampetra showing anterior location of orbit and smaller oral disc, both positioned in front of the branchial region. The total length of the specimen is 116 mm. Drawings in a and b are scaled to show equivalent head lengths: from anterior limit of the oral disc to rear of the branchial region. Horizontal bars indicate the anterior–posterior span of the oral disc in each species.

The life of a parasite must be a good one, and often successful; the creature at the top of the drawing above is a primitive lamprey from the Devonian, 360 million years ago, and the similarities with the modern lamprey (at the bottom) are amazing. It’s less eel-like and more tadpole-like than modern forms, but it has the same disc-shaped mouth specialized for latching on to the flank of its host, it has similar circumoral teeth for rasping through scales and skin for its blood meal, the same pharyngeal adaptations for a life spent clamped to a fish.

I’ve put a photo of the fossil and a cladogram below the fold.

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Lucy is going on tour

The remains of Lucy, the famous fossil australopithecine, are going to be touring the US for the next few years. Start lining up. It’s opening in Houston.

The six-year tour will also go to Washington, New York, Denver and Chicago. Officials said six other U.S. cities may be on the tour. But they would not release the names, saying all the details had not yet been ironed out.

Minneapolis, maybe? I hope? Otherwise I’m going to have to make a trip to Chicago.

No word yet on whether the Answers in Genesis museum near Cincinnati will be bidding on the exhibit.

Dissecting embryos from half a billion years ago

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There is a treasure trove in China: the well-preserved phosphatized embryos of the Doushantuo formation, a sampling of the developmental events in ancient metazoans between 551 and 635 million years ago. These are splendid specimens that give us a peek at some awesomely fragile organisms, and modern technology helps by giving us new tools, like x-ray computed tomography (CT), scanning electron microscopy (SEM), thin-section petrography, synchrotron X-ray tomographic microscopy (SRXTM), and computer-aided visualization, that allow us to dig into the fine detail inside these delicate specimens and display and manipulate the data. A new paper in Science describes a survey of a large collection of these embryos, probed with these new techniques, and rendered for our viewing pleasure…that is, we’ve got pretty pictures!

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