Guiyu oneiros

i-e88a953e59c2ce6c5e2ac4568c7f0c36-rb.png

A fish is a fish, right? They’re just a blur of aquatic beasties that most people distinguish by flavor, rather than morphology or descent. But fish are incredibly diverse, far more diverse than terrestrial vertebrates, and there are significant divisions within the group. Most people know of one big distinction, between the Chondrichthyes (fish with cartilaginous skeletons, like sharks and rays) and the Osteichthyes (fish with bony skeletons), but there’s another particularly interesting split within the Osteichthyes: the distinction between Sarcopterygians (the word means “fleshy fins”, and we call them lobe-finned fishes colloquially) and the Actinopterygians, the ray-finned fishes. The lobe-finned fishes most distinctive feature is the muscular and bony central core of their fins — extant forms are the coelacanth and lungfish. It is this lineage that led to us terrestrial tetrapods, but other than that successful invasion of the land, the sarcops were something of an aquatic failure, with only a few genera surviving. The ray-finned fishes, on the other hand, are a major success story, with more than 28,000 species today. To put that in context, there are only about 5,500 species of mammals.

The Sarcopterygii and the Actinopterygii must have begun diverging a long time ago, and a couple of questions of interest are a) when did the last common ancestor of both groups live, and b) what did it look like? We don’t have a good and specific answer yet, because Osteichthyes origins are lost far, far back in time, over 400 million years ago, but every new discovery edges us a little closer. What we now have is a well-preserved fossil of a fish that has been determined to be an early sarcopterygian, and it tells us that a) the last common ancestor had to have lived over 419 million years ago, the age of this fossil, and the divergence probably occurred deep in the Silurian, and b) this animal has a mosaic of primitive Osteichthyan features, which tells us that that last common ancestor may well have shared some of these elements. It is another transitional fossil that reveals much about the gradual separation of two great vertebrate groups.

And here it is:

i-ba4ab7bcea24c3417d69b43fa74705c5-guiyu.jpeg
(Click for larger image)

a, b, A near-complete fish in part and counterpart. c, Close-up view of the anterior portion of the trunk shield in dorsal view, showing MD1 and MD2 flanked by rhomboid scales. d, Close-up view of the dorsal fin spine. MD1, first median dorsal plate; MD2, second median dorsal plate. Scale bar, 1 cm.

That may be a bit disappointing at first — it looks like Silurian road-kill — but really, that’s a remarkable good and useful specimen. The animal was covered with thick bony scales, and the skull was built of thick bony plates, and so while it was squashed flat by pitiless geology, the pieces are all there, and it can be reassembled into a much more fishy state. This drawing may be more satisfying:

i-79484c5905eacb406749c6e61d25ddb4-guiyu_resto.jpeg
(Click for larger image)

a, Restoration of the entire fish in lateral view. b, Interpretive drawing of the holotype V15541. Areas shaded in grey are unknown, and are reconstructed from other early osteichthyans. ano, anterior nostril; br, branchiostegal ray; cla, clavicle; cle, cleithrum; drs, dorsal ridge scale; dsp, dorsal fin spine; et, extratemporal; eta, accessory extratemporal; f.add, adductor fossa; f.gl, glenoid fossa; gu, gular; ju, jugal; l.ext, lateral extrascapular; lj, lower jaw; m.ext, median extrascapular; mx, maxillary; n.sp., spiracular notch; op, opercular; pa, parietal shield; pcl, postcleithrum; pop, preopercular; ppa, postparietal shield; psc, presupracleithrum; pt, post-temporal; scl, supracleithrum; sop, subopercular; sp., pectoral spine; tr, lepidotrichia; vrs, ventral ridge scale.

Now it looks like a kind of armored, spiky salmon with a thick muscular body (and yes, I too wonder about flavor, and would like to taste a slab of that). It’s definitely not a salmon, though — the bony structure is a curious set of compromises where some features are distinctly sarcopterygian, some look like they belong on a primitive actinopterygian, and others are unique or show affinities to characters of ancient extinct fishes, like rhipidistians. This is very cool. What we see here are relics of an ancient common osteichthyan ancestor, which are being honed into the specific characteristics of the Sarcopterygii. The analysis of the totality of the animal’s features, though, place it more in the lobe-finned than the ray-finned clade. That places it on a branch of the line leading to us…a very, very old branch, making this your many-times-great grand uncle, or cousin only a few million times removed. Now my curiosity about a taste-test is making me feel mildly cannibalistic.

i-d888d1f84f126c55eb104f249de00adb-guiyu_phylo.jpeg
(Click for larger image)

The topology is the most parsimonious tree arising from a matrix of 23 taxa coded for 153 morphological characters (tree length = 292, consistency index = 0.572, retention index = 0.737, rescaled consistency index = 0.421). The numbers at nodes indicate bootstrap support (where the value is greater than 50%) and Bremer decay index (bottom and top numbers, respectively). Eif., Eifelian; Ems., Emsian; Fam., Famennian; Fras., Frasnian; Giv., Givetian; Gor., Gorstian; Loch., Lochkovian; Lud., Ludfordian; Prag., Pragian.

When you look at that diagram, what should jump out at you is all the diversity in the Devonian, the so-called Age of Fishes, and the paucity of representative fossils from the Silurian…which is exactly where all the interesting branch points in the fish family tree are located. Once again, paleontology is a predictive science, and this tells us where to look for the next batch of exciting and informative fossils.


Zhu M, Zhao W, Jia L, Lu J, Qiao T, Qu Q (2009) The oldest articulated osteichthyan reveals mosaic gnathostome characters. Nature 458:469-474.

Tianyulong

I’m not going to say much about this since Ed Yong has an excellent write-up, but a new feathered dinosaur has been discovered, called Tianyulong. As you can see in this image of the fossil, it was bristling with a fuzz of thin fibers — proto-feathers.

i-ffe71f424a82783f5c04dd1cd196d8b5-tianyulong_sm.jpeg
(Click for larger image)

a, Main slab of the holotype (STMN 26-3). b, Broken slab. The scale bar in b refers also to a. c, Close-up of skull and mandible. d, Interpretive drawing of skull and mandible. e, Close-up of dentition. Abbreviations: a, angular; aof, antorbital fossa; ca, caudal vertebrae; cv, cervical vertebrae; d, dentary; dv, dorsal vertebrae; emf, external mandibular fenestra; en, external naris; f, femur; h, humerus; isc, ischium; j, jugal; l, lacrimal; m, maxilla; n, nasal; pd, predentary; pf, prefrontal; pm, premaxilla; po, postorbital; pub, pubis; q, quadrate; qj, quadratojugal; scaco, scapulocoracoid; sa, surangular; tf, tibia and fibula.

There are a couple of noteworthy features in this creature. One is apparent: feathers just didn’t bloom suddenly in evolution, but appeared in steps. This animal has ‘feathers’ that don’t branch like those of modern birds, but instead form more of a furry coat than a set of flat blades.

The other cool thing is that this is an ornithischian dinosaur; most of the other dinosaurs that have been discovered to have feathers were saurischian. What that means might be made more clear by this diagram:

Feathered-dinos.jpg

It implies that just maybe the last common ancestor of the saurischia and ornithischia were also covered with proto-feathers, which means that feathers may be a primitive state in this lineage.


Zheng X-T, You H-L, Xu X, Dong Z-M (2009) An Early Cretaceous heterodontosaurid dinosaur with filamentous integumentary structures. Nature 458:333-336.

Octopods from the Cretaceous!

i-e88a953e59c2ce6c5e2ac4568c7f0c36-rb.png

Several new and spectacular cephalopod fossils from 95 million years ago have been found in Lebanon. “Spectacular” is not hyperbole — these specimens have wonderfully well-preserved soft parts, mineralized in fine-grained calcium phosphate, and you can see…well, take a look.

i-43b532f0c9279d4273f9faa4719ef92e-keuppia.jpeg
(Click for larger image)

Keuppia levante sp. nov. from the Upper Cenomanian (Metoicoceras geslinianum Zone) of Hâdjoula (Lebanon). A,
holotype, MSNM i26320a. B, sketch of the holotype.

[Read more…]

The Open University Annual Lecture

The Open University is having an open lecture on 17 March, and you’re all invited! The topic sounds historically, philosophically, and scientifically interesting:

Richard Dawkins suggests that there are four “bridges to evolutionary understanding” and illustrates this with four claimants to the discovery of natural selection: Edward Blyth, Patrick Matthew, Alfred Wallace and Charles Darwin.

The fifth bridge of evolutionary understanding is identified as modern genetics – which he terms digital Darwinism.

It’s all going to be streamed live on the web, if you are awake at 7:30 pm Natural History Museum time, which I won’t, or you can grab it from a webcast after the event.

Evolving our way to energy efficiency

This is a cool talk: Bill Gross talks about his efforts to tap into solar power. It’s a little bit over-optimistic — how much of the desert Southwest would we have to pave over to collect enough energy for the country? — but the really fun part is where he talks about using unguided evolutionary processes to design solar collectors and heat engines. People who claim that chance and selection can’t produce anything new have never tinkered with genetic algorithms.

Elephantine errors from Ray Comfort

So Ray Comfort is now complaining on the revered pages of the respected publication, World Net Daily about me. The article is full of dishonest misquotes, but let’s zip right to Ray’s scientific misunderstandings. They are deep and painful. He has this bizarre idée fixe that the necessity of every species having males and females somehow greatly reduces the probability that new species could arise. It’s total nonsense, and I dismissed it briefly when I commented on it before.

“I know Ray is rather stupid, but who knew he could be that stupid. This has been explained to him multiple times: evolution does explain this stuff trivially. Populations evolve, not individuals, and male and female elephants evolved from populations of pre-elephants that contained males and females. Species do not arise from single new mutant males that then have to find a corresponding mutant female – they arise by the diffusion of variation through a whole population, male and female.”

Ray has read that, and failed to grasp the central concept. Take a look at the workings of Ray Comfort’s mind as he attempts to wrestle with a simple idea: the hamster wheel is wobbling, but the poor beast lies dead with legs up in its cage, and nothing is turning over.

[Read more…]

Greg Laden has a big advantage over me

He was probably able to get home before midnight last night. You can now read his description of the social events around Dawkins’ visit, and a much more thorough account of the talk itself.

One other point that I should emphasize. This talk presented an overview of how we should look at the appearance of design in the universe, for a general public. While I heard some complaints that there was nothing new in it, that’s the way this had to be: it was a synthesis of a position.

Dawkins is often given a rap as one of those ultradarwinians who see every detail of life as the explicit product of carefully honed selection. For me, what was interesting in this talk was how clearly he repudiated that position. In several places, he contrasted what he called a “naive Darwinist” perspective with reality, and showed that the strawman didn’t hold up. A major point was also that features that may very well have evolved with a core that was selected for can have side-effects, and been subverted to non-adaptive purposes, and that these features may represent a significant element of the species’ character. He talked quite a bit about the flexibility of the human brain, a property that was the product of selection, yet that same flexibility means it can be reprogrammed into deleterious byways, such as religion or fanaticism or unthinking patriotism.

It was all stuff that I agreed with, and didn’t surprise me at all. Similarly, The God Delusion didn’t contain anything radical or new. The virtue of these kinds of talks and books is that they pull many commonly held ideas together into a coherent fusion that can be more readily absorbed by a larger number of people who haven’t yet taken in all of the underlying evidence.

Wild night on the town for a godless nerd

I may be getting too old for this.

Yesterday, I finished up teaching at 1 in the afternoon, then had to leap into the Pharyngulamobile and drive, drive, drive to Minneapolis. I got together with Lynn Fellman and Greg Laden for a hasty dinner before I had to go move my car and park prior to Richard Dawkins’ talk. This was almost a disaster; it turns out that last night, at the same time as the talk, there was a basketball game scheduled. The streets were packed, parking was a nightmare, and I only got to Northrop Auditorium with a whisker of time to spare. Many of the attendees seem to have run into the same problem, as I noticed that people were dribbling in well into the middle of the talk. (No, not dribbling large orange balls…dribbling as in trickling, and looking a little stressed from the struggle to get into the parking garages.)

I introduced Dawkins almost on time, though. I got applauded, even though I only spent less than a minute talking — or maybe because I spent less than a minute talking.

Dawkins’ talk was good. He’s trying to make a strong distinction with a word that’s already greatly overloaded in the English language: “purpose”. His point was clear, that we really can mean a lot of very different things when we describe the purpose of something, and that especially when we’re talking about biology, “purpose” does not imply “designed with intent”. One excellent example of the way “purpose” is abused was shown: Ray Comfort’s infamous banana rationalization. It made the bit even more hilarious to see after Dawkins had warned us of the habit of too many people to use “purpose” too freely to imply intent — Comfort was the perfect bad example. I’m a bit dubious that Dawkins’ word coinages — “archi-purpose” for describing the function of an evolved structure, like a bird’s wings, and “neo-purpose” for novelties produced as a consequence of prior innovations, and which are often subverted to undermine a Darwinian function — but that’s always the problem with attempts to introduce new terms. Language is a slippery beast that will twist beneath your efforts to tame it.

Dawkins did do a book-signing afterwards, at which a huge crowd appeared. I was very impressed at the man’s well-practiced signing technique — he got through everyone quickly, and he didn’t seem to suffer the slightest crippling of the wrist for his trouble.

We then had a pub night, at the Campus Club in Coffman Memorial Union. As you know, we’d kept it a bit mum so we wouldn’t be overwhelmed by a swarm descending on the place, but just by word of mouth we had well over a hundred people in attendance. Richard got his beer, I had non-alcoholic stuff (no fun, but I had a long drive ahead of me), and there was a buffet of good food that vanished amazingly fast. All thanks to Rick Schauer who set up and hosted the event! We had more mobs of people swarming Richard and getting photos taken with him; look for them to bloom all over Facebook today. It was a good opportunity to make a more informal acquaintance with the famous Dr Dawkins than the usual lecture followed by departure, so if you didn’t get the super-semi-secret directions to the party, you missed out on a splendid evening.

We wrapped up and left about 11pm. I know, the night was still young! Alas, I had a three hour drive home ahead of me. I survived it, got home, passed out…briefly. Now I’m up getting ready for my 8am class. Fortunately, it’s student presentations today, so I just have to be awake enough to listen attentively. Have pity on one of my students in that class (Hi, Levi!) who was also in attendance last night, and has to describe frequency shifting in bat calls this morning. It’s good practice for the madcap life of the scientist!

Of course, I’m older than my students. I may just have to drag myself into a dark corner after class and fall into a coma for a few hours in order to recover. I hope you aren’t expecting voluminous posting today…my exhausted brain needs to reboot, I think.

I don’t know how Dawkins does it. He’s just come off of a trip to Michigan, and will be in Oklahoma tomorrow. He is clearly made of tougher stuff than I am.

A brief moment in the magnificent history of mankind

i-ebda22d9414804e9fb97ebb631a7ddac-kenya_footprint.jpeg
i-e88a953e59c2ce6c5e2ac4568c7f0c36-rb.png

Isn’t that beautiful? It’s an ancient footprint in some lumpy rocks in Kenya…but it is 1½ million years old. It comes from the Koobi Fora formation, familiar to anyone who follows human evolution, and is probably from Homo ergaster. There aren’t a lot of them; one series of three hominin trails containing 2-7 prints, and a stratigraphically separate section with one trail of 2 prints and an isolated single print. But there they are, a preserved record of a trivial event — a few of our remote relatives taking a walk across a mudflat by a river — rendered awesome by their rarity and the magnitude of the time separating us.

Here’s one of the trails:

i-29b11c67e34d0e717d2e089fcca99b5d-trail.jpeg
(Click for larger image)

Tessellated swath of optical laser scans of the main footprint trail on the upper footprint surface at FwJj14E. Color is rendered with 5-mm isopleths.

It’s an interesting bridge across time. There they were, a couple of pre-humans out for a stroll, perhaps on their way to find something for lunch, or strolling off to urinate, probably nothing dramatic, and these few footprints were left in drying mud to be found over a million years later, when they would be scanned with a laser, digitized, and analyzed with sophisticated software, and then uploaded to a digital network where everyone in the world can take a look at them. Something so ephemeral can be translated across incomprehensible ages…I don’t know about you, but I’m wondering about the possible future fate of the debris of my life that has ended up in landfills, or the other small smudges across the landscape that I’ve left behind me.

And what have we learned? The analysis has looked at the shape of the foot, the angle of the big toe, the distribution of weight as the hominins walked across the substrate, all the anatomical and physiological details that can be possibly extracted from a few footprints.

i-998d4e49530f96030c27394d1d8f4fe3-prints.jpeg
(Click for larger image)

Optical laser scan images color-rendered with 5-mm isopleths for footprints at both FwJj14E and GaJi10. (A) Isolated left foot (FUI1) on the upper footprint surface at FwJj14E. (B) Photograph of FUI8 on the upper footprint surface at FwJj14E, showing good definition of the toe pads; the second toe is partially obscured by the third toe. (C) Second trail on the upper footprint surface at FwJj14E, showing two left feet. (D) Third trail on the upper footprint surface at FwJj14E, showing a right and a left foot. (E) Print R3 from GaJi10 (22), re-excavated and scanned as part of this investigation. (F) Partial print (FUT1-2) on the upper footprint surface at FwJj14E; the heel area has been removed by a later bovid print. (G) Print FLI1 on the lower footprint surface at FwJj14E, rendered with 5-mm alternating black and white isopleths. (H) Inverted image of the toe area of print FUT1-1 with alternating 5-mm black and white isopleths. Note the locations of the pads of the small toes and the presence of a well-defined ball beneath the hallucial metatarsophalangeal joint. The first, third, and fifth toes are marked D1, D3, and D5, respectively.

The answer is that these beings walked just like us. The tracks are noticeably different from the even older footprints of australopithecines found at Laetoli, from 3.5 million years ago. The foot shape and the stride of Homo ergaster was statistically indistinguishable from those of modern humans, even though we know from the bones associated with these species that they were cranially distinct from us. This is not a surprise; it’s been known for a long time that we evolved these bipedal forms long ago, and that the cerebral innovations we regard as so characteristic of humanity are a relative late-comer in our history.

Remember, though, these are 1½ million years old, 250 times older than the age of the earth, according to creationists. That’s a lot of wonder and history and evidence to throw away, but they do it anyway.


Bennet MR, Harris JWK, Richmond BG, Braun DR, Mbua E, Kiura P, Olago D, Kibunjia M, Omuombo C, Behrensmeyer AK, Huddart D, Gonzalez S (2009) Early Hominin Foot Morphology Based on 1.5-Million-Year-Old Footprints from Ileret, Kenya. Science 323(5918):1197-1201.