How to Draw Heterochrony

A big part of science is presentation. You can have a kickass idea or a really cool discovery, but if you disguise it with enough jargon, or hide your important results in the middle of long descriptive work, or just send your papers to sufficiently obscure journals, you can still have almost no impact. So: a good chunk of science is communication, and communication is all about clarity.

It is worth taking a few minutes to leaf through a biology or anatomy textbook and think about what you see. Most of the figures will be redrawn from journal articles. And the illustrations that are chosen for this peculiar form of immortality are the ones that are so clear that even freshmen can understand them. My guiding light in making figures is to aim for something that is clear enough to be included in a textbook. No luck yet, but the wheels of academia grind slowly. My day may come, and if it does, you'll hear all about it right here. And if it doesn't, textbook clarity is still a good goal to have in mind when drawing figures.

Heterochrony is the rearrangement of development. Not just recapitulation, in which development resembles an evolutionary parade, or neoteny, in which adults look like big goofy babies (think axolotls, or Kirsten Dunst), but a change in the order of developmental events. At least, that's how it should be. Some people include recapitulation and neoteny and any other change in developmental timing as kinds of heterochrony. Other people say that makes the term so broad that it becomes meaningless; everything is heterochrony and nothing is heterochrony. See? Already we're about knee-deep in the swamp of I've Already Lost Interest.

Here, like a breath of fresh air, is Florian Witzmann's figure showing the order of appearance of bony elements in salamander monsters from the dawn of time (a.k.a. temnospondyls). In the future, if anyone asks me what heterochrony is, I'm going to pull a photocopy of this out of my pocket, hold it up in the air, and say, "This."


Many thanks to Florian for giving me permission to post his figure. It is figure 6 from:

Witzmann, F. 2006. Developmental patterns and ossification sequence in the Permo-Carboniferous temnospondyl Archegosaurus decheni (Saar-Nahe Basin, Germany). Journal of Vertebrate Paleontology 26(1):7-17.

The new JVP

JVP is the Journal of Vertebrate Paleontology. There are lots of paleo journals, but I think it is fair to say that JVP is one of the flagships, at least for people working on vertebrates. It's always packed with data, but some issues are just more interesting than others. Sometimes it's all partial fish scales from the Apathian of South New Brunswick and heavily eroded rodent teeth from Devil's Outhouse National Monument.

But the current issue is a gold mine.

Witzmann (2006) reports on patterns of skeletal development in a Permo-Carboniferous temnospondyl (a pre-dinosaurian giant salamander relative). Hold on, there. It's more interesting than it may sound. These temnospondyls were filling the ecospace occupied by crocs and aquatic turtles and true salamanders today. Most of them went through a metamorphosis like living amphibians. Some have been shown to have two adult morphs, one metamorphosed and one neotenic, just like the living salamander Ambystoma with its axolotl form. Witzman's figures ROCK. Figs 5 and 6 show developmental patterns for several temnospondyls and other ancient salamanderish critters and for Ambystoma. The patterns are ossification sequences for various bones in the body, arranged into vertical stacks representing relative time, with lines connecting equivalent steps in adjacent columns so that you can see where the developmental deck has been heterochronically shuffled. Very cool.

UPDATE Florian gave me permission to post his figure. Check it out.

Trueb and Baez (2006)--yes, that Trueb, for you herp-savvy folks--redescribe some itty bitty pipoid frogs from the Cretaceous of Israel. The frogs are not terribly mind-blowing as frogs, unless you're really invested in pipoid phylogeny. I just like learning about all the other critters that were running around during the Cretaceous. It pleases me to think that if I was shot back in a time machine I might have just as good a chance at identifying some of the frogs and lizards as I would at the dinosaurs.

Gower and Nesbitt (2006) describe the braincase of Arizonasaurus and show that "rauisuchians", a group of terrestrial, predatory, pre-dinosaurian croc relatives, are not monophyletic. Some are closer to crocs than others. Arizonasaurus and its allies, which include such weirdos as Lotosaurus, are pretty far down the tree from crocs. Which is fine. If you saw one you would not think "terrestrial croc relative". You'd think, Why is that theropod trucking around on all fours, and why does it have a sail on it's back?" The bird-line archosaurs--pterosaurs and dinos, mostly--have been hogging the limelight for the past, well, forever, but that may be about to change. Effigia and Arizonsaurus are just the beginning.

Here's a picture of Lotosaurus so that you may grok its prehistoric weirdness. The sailback is independently evolved in this group--it has nothing to do with Dimetrodon and Edaphosaurus, which are closer to mammals, or Ouranosaurus, Acrocanthosaurus, and Spinosaurus, which are all closer to birds. Sails were just popular back in the day.


Next up, a Berkeley-MSU paper: Mark Goodwin, Bill Clemens, Jack Horner, and Kevin Padian (2006) on a new dinky skull from a baby Triceratops. This one made the cover. The little skull is adorable, about 2/3 complete, and about a foot long. It already has little brow horns and a scalloped frill. Goodwin et al. take a swipe at the prevailing view that ceratopsians horns and frills were primarily for sexual display. Sexual display structures are usually sexually dimorphic--that's the whole idea, that an individual can tell the boys from the girls. Trouble is, demonstrating sexual dimorphism is not easy. It requires a large enough sample size that sex-related differences can be parsed out from differences related to growth and simple within-population variation. So far the only ceratopsian that meets those standards is Protoceratops. That doesn't mean that the horns and frills of more derived ceratopsians weren't used in sexual display, just that convincing evidence has not been presented for it. Goodwin et al. favor the hypothesis that the fancy headgear was mainly for species recognition: it varies a lot between closely related taxa, but not in a linear fashion that would indicate improving function. It is probably dumb to deny that horns would be useful in fending off tyrannosaurs, but it is worth remembering that centrosaurines started out with horns and then traded them in for big bosses of rough bone on their noses--not what you'd expect if horns were absolutely necessary for their survival. Finding decently developed horncores and shield morphology in a little baby is also more consistent with the species recognition hypothesis than the sexual display hypothesis, although Goodwin et al. allow that the three functions--species recognition, defense, and sexual display--are not mutually exclusive and could have all contributed to the weird heads of ceratopsians.

I don't have a picture of the little Triceratops, but here's a picture of its relative Pentaceratops. This unusually large individual from New Mexico has a skull 10.5 feet long, possibly the longest of any terrestrial vertebrate (unless there are some new Torosaurus specimens I don't know about). You can see that the hindlimb bones have been smooshed flat and parts of the skeleton have been reconstructed. The brow horns on that thing are a full meter long, and they would have been longer with the keratin sheath on (like the horns of cattle). I swiped the photo from http://sill-www.army.mil/pao/Photos/030626/pages/Pentaceratops.htm.


Conrad (2006) describes a new lizard from the Eocene (~50 million years ago) of Wyoming. The lizard is strikingly similar to the living Chinese crocodile lizard, which is cool, because up until now that thing had no fossil record at all. It's closest relatives are from the Cretaceous at least, which means that like the coelocanth it has survived for at least 65 million years without leaving any fossils--until now. Conrad plugged the crocodile lizard and its new Eocene relative into a phylogenetic analysis and found that they branched off from the monitor lizard lineage almost 100 million years ago. So as the last brachiosaurs in North America were going extinct, and as our ancestors were getting used to these newfangled placenta things, the first crocodile lizards were setting sail on their long, lonely voyage through time. And they're still around. Cretaceous survivors rock.

DeBlieux et al. (2006) describe an internal mandibular chamber in Eocene hyraxes that shows sexual dimorphism (it was a big issue for Eocene critters and testing sexual dimorphism). What's all that mean? Hyraxes are also known colloquially as coneys. They are little marmot-looking critters that you may have seen crawling around in rock piles at the zoo. Oddly enough, their closest living relatives are elephants and manatees. No shit. I should point out that the living hyraxes are little marmot-looking things, but for much of the Age of Mammals there were bigass hyracoids that looked tapirs and rhinos. In fact, they seem to have been replaced ecologically by tapirs and rhinos. These Eocene critters have big hollow chambers inside their lower jaws. Holes in bones have to be filled by something, and there are only so many possibilities. Basically it comes down to muscles, salivary glands, and air sacs. The muscular hypothesis is pretty easy to rule out. Muscles leave scars on bones, and the muscle scars on the hyrax jaws do not extend into the jaw cavities. Salivary glands are found in adjacent positions in living hyraxes, but in general glands are not found within bony cavities. Also, there's no obvious reason why one sex would need a lot more saliva than the other. (Yeah, I know how that sounds. If I can leave it alone, so can you.) What about air sacs? The case actually looks pretty good. The bony signature is similar to what you get with air-filled bones, and lots of mammals, including hyraxes, have air-filled pouches that develop from the larynx, trachea, or eustachian tubes. DeBlieux et al. posit that the jaw cavities were filled with air and functioned as resonators for making calls, like the inflated upper jaws of living pacas.

Several things impress me about this paper. The first is the careful way in which the authors evaluate the competing hypotheses. They admit that they can't rule out the glandular hypothesis, it just has a lot less going for it than the air sac hypothesis. And they are also careful to separate the anatomical hypothesis (the cavity contained an air sac) from the functional one (the air sac was used as a resonator for making calls). Finally, their review of the literature on air sacs in mammals is a godsend to anyone who is interested in this arcane topic. I didn't even know that horses had guttural sacs, but evidently there was a paper on their function in Nature in 2000. This is exactly the kind of thing I have in mind when I write about how much enjoyment I get out of being surprised by the living world.

One more and then I'm packing it in. Henderson and Peterson (2006) describe a neck vertebra of an azhdarchid pterosaur from the Hell Creek Formation. Hell Creek is where the first skeletons of Tyrannosaurus were found. In fact, this pterosaur vert came out of a plaster jacket thrown around some tyrannosaur bones! Azhdarchids are the group that includes Quetzalcoatlus, Arambourgenia, and Hatzegopteryx, all of which are contenders for the largest flying animals of all time. The find is cool for several reasons. It's the first diagnostic piece of pterosaur to be published from the whole Hell Creek Formation. Hell Creek is not good country for finding pterosaurs. Like most non-lagoon deposits, it's just too coarse to preserve immensely fragile pterosaur bones, which on average were even more lightly built than the bones of birds. It's not that the pterosaurs weren't there, just that they very rarely made it into the fossil record. The vert is also wicked slender. Azhdarchids are weird; they've got just a double handful of very, very long neck vertebrae, which would not have made for a very flexible neck (or a very strong one, you would think). You can grok some azhdarchid weirdness and read up on what they were doing with those wicked necks here.

Now, I know from long-ass necks. Sauroposeidon (which, yes, I am obligated to mention in every single post--deal with it) was no slouch in the long neck department. Its most slender vertebrae have a length to diameter ratio of about 6.5. There are maybe one or two sauropods out there with vertebrae as extreme. Mamenchisaurus youngi and the newly-named Erketu are the only ones that come to mind. But these 'pods were pikers compared to azhdarchids. The vertebra described by Henderson and Peterson is 37 cm long. It's crushed, but the ends aren't in too bad of shape. The diameter at the posterior end was probably no more than 2.5 cm, which would give it a length to diameter ratio of, gulp, 15.

I know you're dying to see Sauroposeidon get its 50-ton ass handed to it by a pterosaur the mass of a turkey, so here you go.

The pterosaur vert I traced from Henderson and Peterson (2006:fig. 3). Both verts are shown with the front end to the right. The upper pterosaur drawing is the vert from above, and the lower is from the right side. It is worth remembering that not only is that vertebra more slender than most limb bones, but it was also about 80-90% air (same goes for Sauroposeidon, come to think of it). If that doesn't blow your mind, then I pronounce your mind unblowable. And I pity you.

That's just the tip of the iceberg. Those are just seven papers out of 25 in this issue. I didn't mention the new fish, or the other new amphibians, or the new ichthyosaur, or two other new lizards, or the new jumping mouse, or the new pangolin, or the new whale. And, shockingly, I didn't discuss the one sauropod paper, Jerry Harris's description of the skull material of Suuwassea.

I'll probably never do this again. It has taken up half the day. But I was jazzed by all the new hotness, and I just had to share it.

Here are those refs.

-------------------------------------------------

DeBlieux, D.D., et al. 2006. Sexual dimorphism of the mandibular chamber in Fayum Pliohyracidae (Mammalia). JVP 26(1):160-169.

Conrad, J. 2006. An Eocene shinisaurid (Reptilia, Squamata) from Wyoming, U.S.A. JVP 26(1):113-126.

Goodwin, M.B., et al. 2006. The smallest known Triceratops skull: new observations on ceratopsid cranial anatomy and ontogeny. JVP 26(1):103-112.

Gower, D.J., and Nesbitt, S.J. 2006. The braincase of Arizonasaurus babbitti--further evidence for the non-monophyly of 'rauisuchian' archosaurs. JVP 26(1):79-87.

Harris, J.D. 2006. Cranial osteology of Suuwassea emilieae (Sauropoda: Diplodocoidea: Flagellicaudata) from the Upper Jurassic Morrison Formation of Montana, USA. JVP 26(1):88-102.

Henderson, M.D., and Peterson, J.E. 2006. An azhdarchid pterosaur cervical vertebra from the Hell Creek Formation (Maastrichtian) of southeastern Montana. JVP 26(1):192-195.

Trueb, L., and Baez, A.M. 2006. Revision of the Early Cretaceous Cordicephalus from Israel and an assessment of its relationships among pipoid frogs. JVP 26(1):44-59.

Witzmann, F. 2006. Developmental patterns and ossification sequence in the Permo-Carboniferous temnospondyl Archegosaurus decheni (Saar-Nahe Basin, Germany). JVP 26(1):7-17.

Bird parts

In my day job I work on pneumatic (air-filled) bones in dinosaurs and birds. Here are some cool examples.


A beak of a toucan, cut away to show the core of "bone foam". This specimen and the next two are on display at the Natural History Museum in London.


The skull of this rhinoceros hornbill shows a nice separation between functional parts. The beak has to resist forces and so it is filled with struts of bone, like the rest of the highly pneumatized skull. The "horn" is just for show and has little internal reinforcement. It would be interesting to know if the bony wall of the horn is thicker in the unreinforced part--anyone out there have any data on this?


Here's a similar shot for the helmeted hornbill. Males of this species butt heads in midair, and consequently the crest is strongly reinforced. The reinforcing struts converge toward the top of the braincase, which is missing. Compare this photo to the one previous and you'll see where the braincase ought to be, in the semicircular hollow on the right.


Finally, my specialty: some vertebrae. An ostrich neck, in this case. Like birds, we have some air-filled skull bones--our sinuses (ours are not nearly as lightly built as those of birds). But only birds, dinosaurs, and pterosaurs have pneumatic bones in the rest of their skeletons. The bones are pneumatized by diverticula, blind-ended tubes, that develop from the lungs and air sacs.


A 3D model of a swan vertebra, reconstructed from micro CT slices. A couple of intersecting slices are shown on the left. You can see that the vertebra is mostly air space, with a skin of bone and just a few bony struts inside. Same goes for the vertebrae of many dinosaurs and pterosaurs. I'll post some pix the next time I'm in a photo-blogging mood.

Forbidden fruit

Anyone can look smart eating an apple.

You pluck one off the table and toss it lightly into the air. It falls into your other hand with reckless speed, a shiny botanical cannon ball. The casual carelessness of the move is underlined with quiet menace. But then you take a bite and the looming threat is diffused. CRUNCH. It's an authoritative noise, and it feels good, your incisors and canines punching through the oddly brittle fruit. Subsequent chewing is audible even though your mouth is closed. Your masticatory apparatus is blasting this lowly plant organ to bits, and everyone knows it. You swallow, use the apple to gesture at your comapanions, and say something penetrating and witty. They look at you admiringly, the young sage with the cool hair, perched artlessly on the edge of the table, crunching an apple.

No one looks intelligent eating a banana.

You pick up the bunch and start looking for the one that is most ripe but has the fewest bad spots. Already you've been reduced to subhuman status. You're not even eating. You're foraging. God forbid that anyone is actually watching while you go through this demeaning ritual. Finally you've made your choice. You take a couple tries getting your grips just right, cock your elbows out to the side like a chicken, and tear off your chosen banana. RIIIP! It's a crude, jungle noise. Then you peel it, the suburban ape manipulating its insensate prey. The peel splits with a barely audible tear, like a fleshy zipper. Now you're standing there with a banana clutched in one hand. A big soft lollipop, peels drooping over your fingers like dead vines. What to do with the other hand? You can't cock it on your hip--you're eating a banana, for crying out loud, not posing for a photo on top of Everest. You toy with putting it in your pocket, just to get rid of it, but finally you let it hang at your side, defeated and useless. You couldn't look stupider if you were using it to scratch your ass. At last, forty-seven subjective minutes into this tawdry little drama, you take a bite. Instantly you know you've bitten off too much. This is no hunk of apple that you can reduce with a few decisive strokes of the jaw. No, this is a big cylinder of mush, and as your teeth slog through it most of it gets squeezed into your cheek. There you are, shoulders hunched, one arm sticking straight out from the elbow like you're a moron holding some balloons, other arm hanging bonelessly, cheeks bulging with a bolus of simian indignity. You look up suddenly, painfully aware that she is in the room. She is on the edge of the couch, already leaning toward the door, watching you with the eyes of a terrified child. You start to say something but catch yourself, and barely avoid drooling banana pudding down your chin. From her perspective it looks like you just choked back some vomit. You glance down to gather your thoughts and finally, mercifully, you can swallow. As you look up, your lungs tense and your mouth opens, ready to ingratiate, to cajole, to plead. Your words die on a cold wind blowing through the open door.

Later, as you watch Friends reruns and cry into your second pint of ice cream, you make a mental note. Buy some apples.

I got cancer at the beach

I took the tooth to Berkeley to get an ID from people who actually know they're marine critters. Somewhere along the way, I started to have doubts that it was a tooth. For one thing, the base is almost perfectly rectangular, and teeth tend to have round roots. For another, it seemed to be made of something much lighter than enamel.

Jane Mason, the UCMP's preparator, said it was probably a claw from a big crustacean.

Crissy Huffard, former fellow grad student, recent Ph.D., and expert on all things tentacled and horrible (try Googling "walktopus") was able to narrow it down considerably. My "sea lion tooth" is the mobile outer crushing claw of a crab in the genus Cancer. The archetypal crab, the one in the zodiac, the one you've eaten at Long John Silver's and Red Lobster.

Perhaps not as exciting as a giant tooth. Definitely a warning talisman against letting wishes and emotion affect one's identifications (cryptozoology crowd, are you listening?). But still the coolest thing I ever found on a beach.

The coolest pocketable thing, anyway. This dead sea lion at Morro Bay was pretty sweet.

About that sea monster

This morning I went beachcoming. It was low tide and we've had some high seas lately, so it was a great time for it. I found a bunch of stuff. Here are the best bits. The tooth in the middle is the best thing I've found on a beach ever, and possibly the best thing I've found period. It's clearly mammalian, probably the canine of a sea lion. I've got a friend who works on marine mammals, so I'll ask him for a definitive ID. Stay tuned.

If you're wondering about the odd bit up in the left corner, it's a piece of granodiorite or some near relative. Slow cooling intrusive igneous rock, at any rate. I kept finding little pieces, which was odd. There are exposed plutons around Morro Bay--the eponymous Morro, Spanish for rock, refers to the hundreds-of-feet-tall igneous plug that sticks up out of the beach like God dropped his bowling ball. But that's more than a hundred miles south of here. All the land around here is uplifted Miocene sandstone and other shallow marine junk, including some conglomerates. Then I found a lime-sized chunk of conglomerate with, ta-da, pieces of granodiorite in it. Some long-lost batholith was exposed and eroded and shed those pebbles, which fell into the ocean with a bunch of sand and gravel and ended up as conglomerate, which was itself uplifted and eroded and has now shed this complicated little piece of history on the beach down the street from my apartment. Cool, huh?

I see that I forgot to include a scale bar. The tooth is about an inch and a half long. I'm still pissed at myself for dumping all of these things into my pocket together. That's how the holes got into the sand dollar, which was flawless when I plucked it from the beach. Oh well. Thursday morning London will be at daycare and the tide will be out.



UPDATE: Uh, yeah. My "clearly mammalian" tooth turned out to be nothing of the sort.

Drawings

Nothing spectacular, just a couple of sketches I've done since I started drawing again. I used the white trash scanner (i.e., digital camera) and cropped out the backgrounds, but otherwise didn't mess with them. The opossum skull is one that I found in the woods in Oklahoma and cleaned up myself. I think it was the first skull I ever cleaned. The shell is one that Vicki brought me as a present from someplace. I think. I might also have picked it up in a shop in Monterrey. Hard to say.

Mania

In a recent message, Mike Taylor wrote, "I know from many, many years' experience (in programming as well as palaeo) that my phases of enthusiasm drift in and out of being in a totally random way, so I need to sieze each one as it comes past and squeeze it till it bleeds productivity."

I was comforted to hear this, because it's the first time I've heard anyone discuss one of the ruling phenomena of my life: manias.

They seem to work on 4-6 week cycles. When I am in the grip of one, it is what is on my mind most of the time. I can't predict when the next one is coming or what it will be. And most of them come around more than once.

Earlier this year it was bonsai. Then model rockets. For the past several weeks it has been natural history in general. I have been ODing on David Attenborough videos checked out four at a time from the local library. (I watch one a day while rocking London, usually half for the afternoon nap and half for bedtime.) The natural history one is odd, because I don't think it is going away. It shows signs of escaping the narrow bounds of a mania and becoming a predominant obsession.

I'm reading E.O. Wilson's biography, Naturalist. It's phenomenal. I am usually scrupulous to a fault when it comes to the condition of my books, and some that I've read two or three times still look brand new (unless I've had the questionable judgment to loan them out). But I've dog-eared half a dozen pages in Naturalist so I can go back and write down some quotations. Here's one of my favorites: "Hands-on experience at a critical time, not systematic knowledge, is what counts in the making of a naturalist."

That made me think about turtles. My childhood was ruled by dinosaurs, but turtles were in a close second, with whales, mammoths, airplanes, and rockets forming a tight pack right behind. This was when I was in single digits, before I saw Star Wars and my brain shipped off for a long tour of duty in a galaxy far, far away. I found an abridged, illustrated copy of Moby Dick in the school library when I was in second grade, with a lurid cover showing old Ahab duking it out with the titular monster. Whales became a frequent recurring mania. I would fold up the bottom third of an 8xll" sheet of paper, tape down the sides, cut scallops on the top margin of the folded third and draw clouds on the exposed third. This was my ocean. From another sheet of paper I cut a three-masted whaler, several whaling boats, and several whales (usually sperm, blue, and right, if you're curious). Then I would spend an afternoon reenacting fierce battles and bloody slaughter on the high seas.

So, to illustrate, my manias go way back. All the way back, as far as I can remember. But I was talking about turtles.

My maternal Grandpa taught me to fish and play cards and gave me my first pocketknife when I was nine. He had promised it to me when I was seven, but Mom and Grandma made me wait two agonizing years to get it (by the time my youngest brother, Ryan, came around a few years later, the legal limit was down to seven). Grandpa was the consumate outdoorsman. He was a hunter of winged and legged creatures, kept a garden and an orchard, canned his own fruits and vegetables, caught fish with rods or shot them with a bow and arrow, and raised minnows for bait. In short, any living thing in his demesne, be it flower, pea, or tree, fish, bird, or mammal, was something he could grow, catch, and/or cook. He also--crucially--practiced taxidermy. The entryway to my grandparent's spacious house was a veritable museum. On long summer visits I would retire to entryway with my sketchbook and spend hours drawing animals from his menagerie. I think he must have had one of every common waterfowl and shorebird in Nebraska, most of the smaller mammals, and a few of the larger ones. My favorites were the skunk, badger, porcupine, and coyote, although the antlered buck and the pronghorn antelope were also very impressive. Oh, and a couple of prairie rattlers. All things he had hunted, cleaned, and mounted himself.

If the slaughter of so many beautiful creatures seems offensive to modern tastes, keep in mind that Grandpa was born in 1911 and made his collection when doing so was not thought ill of, and when animal populations were in better shape than they are today. But I was talking about turtles.

When I was five Grandpa brought me and my brother Todd (Ryan's conception was still two years off) some box turtles, Terrapene ornata. I became an instant turtle nut. Dad built a chicken-wire turtle run in the back yard, and the turtles promptly climbed out. Version 2.0 was the last version we would ever need: a turtle tire. A turtle tire is a worn-out tractor tire six or so feet in diameter. Lay it on its side on a flat patch of ground. Place bricks underneath the bottom lip on the inside. Fill it with sand and soil until the bricks and the interior of the tire are filled up to the bottom lip. Dig out a one- or two-foot section of the inside--this will be the pond. Put in your turtles. Feed them every day, with unusable bits of vegetables and fruits from the kitchen, plus whatever worms and insects two energetic preadolescent boys can catch in an afternoon. Melon guts and crippled grasshoppers are special favorites. Keep the pond filled with water. The turtles now have all they need: land and water, sun and shade at all hours of the day, dirt to dig in (but bricks to force them down instead of out, and thus keep them from escaping), the companionship of other turtles, a steady stream of nutritious food, and the constant attention of two boys. The boys also have all they need: a domain of their own, a little world to manage, animals to care for, responsibilities, and a constant source of entertainment and education. "Hands-on experience at a critical time, not systematic knowledge, is what counts in the making of a naturalist."

If they have the hands-on experience, they will acquire the systematic knowledge when they need it, or for sheer pleasure. Mom and Dad got me the Golden Guide to Reptiles & Amphibians, by Herbert Zim. That led to other Golden Guides. I enjoyed leafing through Rocks & Minerals, Insects, Spiders & Their Kin, Fishes, and Mammals (somehow I missed birds), but I devoured Reptiles and Amphibians. I read it more times than I can count. I memorized it. "Digging long tunnels is characteristic," it said of the Gopher Tortoise. I was six, and I didn't know what 'characteristic' meant. I thought it was some kind of special dirt for digging long tunnels in.

Eventually the Golden Guide to Reptiles & Amphibians was replaced by the Audubon guide to same, with glossy full-color photos of every species and detailed information on their ranges and habitats. Even that would be replaced by the Peterson Field Guide to Eastern Reptiles and Amphibians when I took herpetology with Laurie Vitt at OU (the paintings in Peterson's show the field markings better than the photos in Audubon's, doncha know). Dr. Vitt--I am too much a student to call him Laurie, then or now--also served on my master's thesis committee, which brings us full circle: back to dinosaurs.

Sometimes a predominant obsession becomes the fodder for a mania. Paleontology is elevated from something I do to something I do all the time. I stop reading. I stop watching television. I stay up until 3:00 in the morning poring over monographs, building tables of data, calculating percentages, having insights, digging around the margins of the Big Picture to see how much is left to discover. Writing, for ten or twelve or eighteen hours a day. I don't know if this happens to everyone else, or anyone else. I suspect it must. I hope so, because it's what I live for. I hardly ever talk about it except to Vicki, and when I do I call it being On.

I've never been able to pin down the schedule or the necessary preconditions for being On. It has always just seemed to come over me. Alexander the Great talked about being possessed by the gods. Ridden by them, like a man rides a horse. That's what being On has always felt like.

A ready supply of new data is probably a necessary condition, but it is not sufficient. Last June I went to Chicago to meet Mike and spend two and a half days rocking out at the Field Museum. The data came in buckets, in torrents. In one day we took over 500 digital photographs. The evenings we spent banging through calculations and outlining papers. It was exhilarating, but when I went home I went back to business as usual. I was not On.

A month later I went to BYU and almost immediately did turn On. Maybe it was the long drive across Nevada, where the Earth shows its anatomy so plainly that you can count the ribs. For whatever reason, when I got to Provo I fell into a typical On schedule. Every morning I would rise, shower, and grab a pastry and some caffeine on my way to the museum. Then work tirelessly until noon. Nip out for a quick lunch, and work until just before lockup time in the evening. Grab a slightly more leisurely dinner, and then back to the motel room to download the day's photos, crank data, process images, and make figures until 2:00 or 3:00 in the morning.

Who knows, maybe some people work that hard all the time. I certainly do not. On a typical day I would put in eight or nine hours at the museum and another seven or eight in my room. On second thought, I really doubt that many people do. That's basically a full work day of physical labor, climbing ladders, pushing carts, and lugging around sauropod bones, and another full work day of computer time. By nature and inclination I am not used to working sixteen hour days, and on the rare occasions when I have to, I am usually a zombie after a day or two of it. But when I'm On... Well, for one thing, it's not work. It's not even play. It's a drug, and I'm a junkie.

So. Why can't the junkie turn on his fix whenever he wants? Why do the bouts of being On come on suddenly and unpredictably and wane just as mysteriously? When I started writing this post, I had no idea, but now I have a hypothesis and I telegraphed it above. I think being On is like a spring tide, the convergence of two powerful forces--my Predominant Obsession and my manias--that reinforce each other and boost the signal of the former to an undeniable level.

Which leaves the mystery of where the manias come from. I have a hypothesis about that, too. I think my attention must run in 4-6 week cycles. At times I find myself bored and restless. I cast about. I scan my bookshelves and take long walks, looking for inspiration. Then I fix on something. A bonsai tree in a shop window. An online story about a commercial space launch. Or, just maybe, figuring out the mass of a Brachiosaurus neck.

If I could harness the manias, I would. I've tried. When I feel that familiar restlessness coming on, I sometimes try to seed the ground with something broad and provocative. Usually a book, like D'Arcy Thompson's On Growth and Form, or Stephen J. Gould's The Structure of Evolutionary Theory. Or something less lofty, like How to Draw Comics the Marvel Way or the Guinness Book of World Records or the Estes Model Rockets 2006 Catalog.

It has never, ever worked. The problem is that when I am bored and restless I am bored by everything I can think of. So I have to search for things that I have not thought of, or at least not thought of for a while (e.g., model rockets). By their very nature, manias are unpredictable and undirectable.

I'm not complaining, mind you. Life is almost unendurably interesting. Since my last post I have not drawn every day, but I have drawn frequently. I have learned how to juggle, thought I'm still not very good at it. I've marveled at frogs brooding tadpoles in their throat sacks and birds nesting behind waterfalls, while London snores in my lap and David Attenborough patiently and cogently explains the natural world. I've compiled data and run statistical analyses and learned surprising things about the world, things that I didn't suspect and in fact predicted against.

I walked the beach this morning and found the tooth of a terrible monster. Honest.

I will blog about all of this in due time. Honest.

I hope your life is constantly, variously, unendurably interesting as well.

A new adventure, in which Dr. Vector fights to free himself from the tyranny of silicon

I know that from the outside I appear to be basically perfect. A fine specimen of a man, bit over six two, dashingly handsome, as smart as one of those evil floating brains from the midnight movies, and astonishingly proficient at not just turning phrases, but twisting them like balloon animals into the shapes of Greek gods. In fact, I wouldn't be surprised to learn that as you sit there, prisoner in your own squalid existence, in which you do not write papers about the biggest animals that ever lived, or eat six and a half Big Macs in one sitting, and certainly do not conceive, let alone publish in print or online, sentences as utterly unparseable as this one--all things that I have done--you wonder if there is any point in going on. Such is my awesomeness.

But take heart, dear reader. Stay that suicidal hand. All is not as it appears. I have a weakness.

It's this damn machine. I've been pouring my life into it. If I'm not writing (and I'm usually not) I'm making up figures in Photoshop. If I'm not making figures I'm checking my e-mail. If I'm not checking e-mail I'm catching up on the handful of sites I visit regularly. If I'm not hitting the regulars I'm trolling reddit for interesting bits. If I'm not surfing the web I'm playing video games--not the primo stuff either, but addictive junk like FreeCell or the falling sand game (go on, Google it, I dare ya). And if I'm not playing video games I'm blogging.

I can't remember when the last time was that I drew anything by hand. I mean actual drawing, not doodling in the margins of notebook during staff meetings, and not for research--sketches of specimens don't count. I mean drawing for fun. I used to draw all the time. When I was a kid I filled sketchbook after sketchbook.

I also used to spend a heck of a lot more time outdoors. Usually hunting for turtles, but I used to go stomp around in rivers and creeks and just roam through pastures looking for cool stuff. There's a word for someone who does that: naturalist. I used to be one. What does that make me now?

I can't turn The Damn Machine off. I need it to get my dissertation done, and I need e-mail to keep in touch with the world. (I don't need to keep in touch with the world every half hour.)

I don't even want to turn it off. I love the net. Without it I wouldn't have found Paul Graham and Andrew Rilstone and PostSecret and Darren Naish's blog and a handful of other things that add measureable enjoyment to my life.

But. There is a difference between time spent and time wasted. I could get through all of those truly enjoyable bits in less than one hour per week. It's the web surfing that's killing me an hour or two at a time. That, and stupid FreeCell. I hit game #617 today and probably blew five hours trying to beat it. I finally decided that any FreeCell game that can keep me down for that long must be a legend, so I Googled it. The first hit was a guy who spent a week and a half beating #617, and who is now scouring the net for a solution to #11982, which may actually be unbeatable.

See? See? WTF! I constantly bitch to myself about not having enough time, and then I pour it away like wine down a rat hole.

Anyway, I decided that an alpha FreeCell dork like my Google find might be able to spend a week and a half beating one game, but I can't. I ain't even going to try. FreeCell game #617 is the end of the road for me.

Tomorrow I am going to buy a sketchbook, and I'm going to draw in it every day. And I'm going to learn how to juggle. And I'm finally going to learn the constellations.

Just don't expect any progress reports here.