Archive for the 'Fossils'

The coelacanth genome has been sequenced, which is good news all around…except that I found a few of the comments in the article announcing it disconcerting. They keep calling it a “living fossil” — and you know what I think of that term — and they keep referring to it as evolving slowly The slowly evolving coelacanth The morphological resemblance of the modern coelacanth to its fossil ancestors has resulted in it being nicknamed ‘the living fossil’. This invites the question of whether the genome of the coelacanth is as slowly evolving as its outward appearance suggests. Earlier work showed that a few gene families, such as Hox and protocadherins, have comparatively slower protein-coding evolution in coelacanth than in other vertebrate lineages. Honestly, that’s just weird. How can you say its outward appearance suggests it is slowly evolving? The two modern species are remnants of a diverse group — it looks different than forms found in the fossil record. And then for a real WTF? moment, there’s this from Nature’s News section. It is impossible to say for sure, but the slow rate of coelacanth evolution could be due to a lack of natural-selection pressure, Lindblad-Toh says. Modern coelacanths, like their ancestors, “live far down in the ocean, where life is pretty stable”, she says. “We can hypothesize that there has been very little reason to change.” And it is possible that the slow genetic change explains why the fish show such a striking resemblance to their fossilized ancestors. Snorble-garble-ptang-ptang-CLUNK. Reset. Does not compute. Must recalibrate brain. None of that makes sense. The modern fish do not show a “striking resemblance” to their fossilize ancestors — they retain skeletal elements that link them to a clade thought to be extinct. This assumption that Actinistian infraclass has been unchanging undermines their conclusions — the modern...
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Another feathered dinosaur has been found in China, prompting Ken Ham to dig in his heels and issue denials. Yet another supposed “feathered dinosaur” fossil has come to light, again in China. (Dr. Elizabeth Mitchell, AiG–U.S., reported on another Chinese fossil of a supposed feathered dinosaur in April 2012) Now, one headline described the fossil as “almost birdlike,” and the authors of the report in Nature Communications note many features the fossil shares with living birds, particularly those that live on the ground. In fact, Dr. Elizabeth Mitchell and Dr. David Menton (AiG–U.S.) both examined the photos of the fossil and the criteria the authors used in classifying the fossil as a dinosaur. They agreed that it is a bird, not a feathered dinosaur. Oh, really? It’s just a bird? Take a look at this image of Eosinopteryx, and you tell me. Notice a few things about this animal: it’s got teeth. The forelimbs have clawed digits. It has a long bony tail. It lacks the bony keel that anchors breast muscles in modern birds. The only thing that might cause you to question its dinosaur nature (and it’s a criterion that’s proving more and more inappropriate) is that lovely gray fringe of feather impressions that surround the whole fossil. And look at those forelimbs! It looks like it has stubby wings. It does not, however, have the skeletal and muscular structure to allow for extended flapping flight, and the wings are way too short for it to have been an adequate flyer. But Mitchell and Menton and Ham looked at that and said ‘ALL BIRD’. They’re idiots. Ham goes on: there are no transitional forms, he squeaks, there can be no transitional forms, transitional forms don’t exist…all while looking at a winged, feathered reptile with teeth and claws and a bony tail. The fossil record doesn’t reveal any kind of dinosaur-to-bird evolution—and it certainly does not show a molecules-to-man...
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Eugene McCarthy, the author of that crackpot stabilization theory, has discovered my review and is now making a noise on twitter. He’s gone from thanking me profusely for mentioning him, to whining that I stole his figures, to complaining that I don’t understand his theory at all, all in the last 24 hours. But here’s the fun part. Recall that one of his bizarre claims is that whales did not evolve from terrestrial artiodactyls, but from mosasaurs, mesozoic marine reptiles, instead. But the anatomy shows that mosasaurs are derived squamates, reptiles, with a completely different skeletal organization than a mammal. This has attracted the attention of Darren Naish and Tom Holtz, fully qualified comparative anatomists and paleontologists, who actually know a great deal about the structure of these animals, and are giving him a spectacular ass-whooping. Browse it on Twitter. The basis of his claim is that mosasaur teeth “look like” sperm whale teeth. That’s not a good criterion, and it’s not true; as has been pointed out to him, basal mosasaurs are pleurodont (that is, the teeth are fused to the inner side of the jaw bone), not socketed as are sperm whale teeth. He’s also now claiming that mosasaurs swam by vertical motions of their tails, like whales…but he’s citing articles with poor comprehension. The cited articles show evidence that mosasaurs propelled themselves with axial motions of the tail, which is a far more general statement; they moved by sweeping their tails like oars, but it says nothing about vertical vs. horizontal undulations. So I went back to McCarthy’s book to see how he backed up this ridiculous claim. He doesn’t. He cites Pieter Camper, an 18th century anatomist, as proposing the idea that whales are related to mosasaurs. His critics are citing contemporary and detailed papers. This, however, is really the totality of McCarthy’s argument: The varanid theory was...
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It always seems to be the case that there are gaps in the fossil record just where things get interesting — probably with good reason, that forms in transition will be relatively rare. One such gap is the period where insects first emerge and begin to conquer the terrestrial world, a period called the arthropod gap, between 385 and 325 million years ago. Here’s a new specimen from that relatively barren stretch of time, Strudiella devonica. a, Photograph of the part. b, Reconstruction of general habitus. Scale bar, 1 mm. White arrows indicate legs visible on part. abd, abdomen; ant, antenna; h, head; md, mandible. It’s a classic insect: a body divided into three regions (head, thorax, abdomen), six legs, a fairly general set of omnivorous mouthparts. It lacks wings, but the small size suggests it may be in a nymphal stage (also, the genitals at the tip of the abdomen didn’t make it), so that may not mean much. Garrouste R, Clément G, Nel P, Engel MS, Grandcolas P, D’Haese C, Lagebro L, Denayer J, Gueriau P, Lafaite P, Olive S, Prestianni C, Nel A (2012) A complete insect from the Late Devonian period. Nature 488, 82–85. (Whew, that’s a lot of authors for a short paper.)

I don’t mind the portrayals of dinosaurs in coitus, but look at those two: did they have to have such lecherous grins? The disturbing thing is that that is the same expression they’d have on their face when they were ripping up a hadrosaur. Being a monkey-faced primate with a dependence on facial expressions really sets up inappropriate expectations when looking at stone-faced reptiles.