It’s Big Bird! No, it’s Gigantoraptor!

This is Gigantoraptor erlianensis, a newly described oviraptorosaur from late Cretaceous of China. It’s a kind of nightmare version of Big Bird — it’s estimated to have weighed about 1400kg (1½ tons for non-metric Americans).

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Histological examination of the growth structure of the bones suggests that this fellow was a young adult, about 11 years old, and that they grew rapidly and reached nearly this size by the time they were 7. And since it is a young adult, there were probably bigger gigantoraptors running around. They also compared limb length to other dinosaurs, like the tyrannosaurs—gigantoraptor had longer, slimmer legs and was more of a runner than they were.

There’s no sign whether it was covered with bright yellow feathers.

Xu X, Tan Q, Wang J, Zhao X, Tan L (2007) A gigantic bird-like dinosaur from the Late Cretaceous of China. Nature advance online publication, 13 June 2007.

Stone soup; or, extracting protein fragments from T. rex bones

Science magazine has an article today on extracting and sequencing proteins from T. rex bones, and I’m already getting email from people wondering whether this is believable, whether it challenges the stated age of dinosaurs, whether this means we can soon reconstruct dinosaurs from preserved genetic information, and even a few creationists claiming this is proof of a young earth. Short answers: it looks like meticulous and entirely credible work to me, these fossil bones are really 68 million years old, and it represents a special case with limits to how far it can be expanded, so scratch “reassemble dinosaur from fragments” off your to-do list.

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Orthozanclus

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Reconstruction of O. reburrus by M. Collins. The precise arrangement of the anteriormost region remains somewhat conjectural.

Halkieriids are Cambrian animals that looked like slugs in scale mail; often when they died their scales, called sclerites, dissociated and scattered, and their sclerites represent a significant component of the small shelly fauna of the early Cambrian. They typically had their front and back ends capped with shells that resembled those we see in bivalve brachiopods. Wiwaxiids were also sluglike, but sported very prominent, long sclerites, and lacked the anterior and posterior shells; their exact position in the evolutionary tree has bounced about quite a bit, but some argument has made that they belong in the annelid ancestry, and that their sclerites are homologous to the bristly setae of worms. One simplistic picture of their relationship to modern forms was that the halkieriids expanded their shells and shed their scales to become molluscs, while the wiwaxiids minimized their armor to emphasize flexibility and became more wormlike. (Note that that is a very crude summary; relationships of these Cambrian groups to modern clades are extremely contentious. There’s a more accurate description of the relationships below.)

Now a new fossil has been found, Orthozanclus reburrus that unites the two into a larger clade, the halwaxiids. Like the halkieriids, it has an anterior shell (but not a posterior one), and like the wiwaxiids, it has long spiky sclerites. In some ways, this simplifies the relationships; it unites some problematic organisms into a single branch on the tree. The question now becomes where that branch is located—whether the halwaxiids belong in a separate phylum that split off from the lophophorate family tree after the molluscs, or whether the halwaxiids are a sister group to the molluscs.

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No more microcephalics

Zimmer describes some of the more recent work on Flores Man — people are still arguing over whether the fossil is of a peculiarly abnormal human with microcephaly, or whether there was a species of ‘miniaturized’ Homo living on the islands of the Pacific. Trying to establish common characteristics of microcephalics is an interesting project, but it doesn’t answer the question. We need more fossils! Among the good news Carl mentions is the report that more excavations will be underway this year.

Save the Doushantuo embryos!

I reported a while back that there was a possibility that the phosphatized pre-Cambrian Doushantuo specimens might not be embryos—they might be a particular class of bacteria—but there may be evidence against that hypothesis. John Lynch finds a description of more advanced embryos, intermediate stages that would link at least some of the blastulae described so far to unambiguous multicellular organisms.

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.