Organic Matter - Natural History

Dinosaur Penises: Tyrannosaurus sex

Thu, 14 Feb 2008 23:26:44 -0800

If that title doesn't get hits, nothing will.

In celebration of President's Day (which I have off work), Valentine's Day (which I do not have off work), and Charles Darwin's birthday (which isn't even a holiday), Olivia Judson has written a brilliant article on the mating habits and physiology of Tyrannosaurus rex at her New York Times blog, The Wild Side.

Now if we stipulate that:

All little boys love dinosaurs.
- T. rex is the coolest dinosaur.
- Some little girls love dinosaurs too.
All big boys love sex.
- Again, some big girls too (probably a great many more than loved dinosaurs when they were little).
- Okay, I think we can agree that everybody loves sex.

We clearly see that Judson's choice of topic was well-calculated genius. Distilled by this genius is a terribly interesting look at both the evolutionary biology and natural history of dinosaurs and their closest living relatives...

So what can we say about dinosaurs? My guess is that the males had members — but it’s an educated guess. It’s based on an analysis of dinosaur relations.

Two living groups are most closely related to dinosaurs. One is the crocodiles. Male crocodiles have a penis — just one — which, most of the time, they keep tucked inside their cloacae. (In most species of crocodile, it’s hard to determine the sex of living animals without an intimate exam, never mind dead ones.) Compared with the mammalian penis, the crocodile’s has an oddity: sperm is transported along an external groove, rather than through an internal tube.

The other group related to dinosaurs is the birds. Indeed, to be strict about it, birds are dinosaurs. If you look at a family tree of dinosaurs, birds, and other reptiles, you see that the lineage that evolved into dinosaurs split off from the lineage that evolved into crocodiles. Birds, in contrast, evolved directly from a dinosaur lineage. Birds are more closely related to T. rex than they are to any living form.

Birds themselves divide into two main groups, formally known as the palaeognathous and the neognathous. The palaeos comprises the big flightless birds such as ostriches, emus, rheas, and cassowaries, as well as kiwis and an obscure (but flying) group of south American birds, the tinamous; the neos covers everything else. The palaeos have penises; like crocodiles, they keep them tucked into their cloacae. Again like crocodiles, the organ has an external groove for sperm. What’s more, the lineage leading to the other endowed birds, the ducks, geese, and swans, appears to have split off from that of the other neos relatively early.

This strongly suggests that the ancestor of all birds had a penis, and that at some point early in the evolution of the neognathous birds, the penis got lost. Since crocodiles have one, and ancestral birds almost certainly did, and since the two groups have such similar genital morphology, I think it’s a safe bet that the lineages between crocodiles and birds — that is, dinosaurs — had one, too.

Now, the next question — what did it look like? Was it large or small? Fancy or plain? I wouldn’t like to guess. The blue-billed duck (Oxyura australis) is just a little fellow — he weighs less than one kilogram (two pounds) — but his penis measures 28.5 centimeters (11 inches), and it’s covered with knobs. In contrast, the mighty ostrich (Struthio camelus), which can weigh as much as 160 kilograms (350 pounds), has a penis that’s a mere 20 centimeters (8 inches) long. But at least it’s bright red.

Happy Valentine's Day.

Tigers and Bears; Lions Not So Much

Wed, 16 Jan 2008 08:00:48 -0800

I’ve seen so much stuff I’d love to write about that it’s actually overwhelming. This happens from time to time, and the result is ironic in that I end up writing nothing. I’ve been tempted to just post a shitload of links to all of the things I’ve found interesting lately, but for a couple of the articles in question, the shotgun effect just won’t do them justice. I’ve been tempted to write about zoos before, and indeed I wondered whether or not I had, but the search function suggests that I have not. This cannot stand.

Like most kids, I loved going to the zoo. What isn’t cool about lions, tigers, and bears? It wasn’t until I was about thirteen or fourteen that I became aware that the animals at the Los Angeles Zoo were noticeably less excited about the cross-species experience than I was. They seemed bored at best, maybe even depressed. I’m sure anyone who’s made it to this particular corner of the Internet has noticed this about confined animals. And as we all know, teenagers aren’t very well attuned to moral ambiguity – I was no different – so I decided that zoos were bad, mmmkay? Undebatably, absolutely, unequivocally, evil.

Obviously my understanding of what zoos can and do accomplish has developed since then, and while I’m still a little uncomfortable visiting them (which is why I’m unable to illustrate this post with a photo of some captive exotic species), I appreciate that they work to conserve threatened species, and introduce the public to majestic, charismatic creatures.

Obviously, the zoo news of the day is the escape of Tatiana, one of the San Francisco zoo’s Siberian tigers (Panthera tigris altaica). Her escape and subsequent killing suggests that for some species, the good work done by zoos may not always outweigh the harm.

Life in a zoo isn't necessarily oppressive for all animals. Most animals didn't evolve to explore as much space as tigers. But tigers in most zoos are like people spending their lives locked in an empty living room. They are confined to tiny spaces, with nothing to do. Life is intensely boring, year after year. Some animal observers say zoo life may also be stressful. Tigers, who like to lurk, skulk and hide, are on display, with groups of strangers staring at them. Freedom is absent, and so are choice and control.

[…]

Roberts […] has no patience with the defense of zoos, either for their genetic storage programs or their ambassador roles. "The tiger is a perfect example of the way that zoos are missing the point about conservation," he says. Money spent on zoo tigers should be spent on protecting habitat for wild tigers. "There's an expenditure of millions if not tens of millions of dollars on captive tigers. If we really want tigers and not just a shell of the beast we call the tiger, the real emphasis needs to be first and foremost in the field."

Of course, with tigers more than perhaps any other animal, protecting habitat is more complicated than simply throwing money at the problem. Like many other exotic species, tigers are sought for specific parts of their anatomy, including their bones, organs, eyes, and even their penises, all of which are thought by some medicinal traditions to have curative properties. But cultural relativism is a sensitive issue, and not at all what I sat down to write about. What actually spurred me to write about zoos was an article from Time about a different species that is raising questions about how animals live in captivity:

Earlier this week [Germany]'s tabloid press agonized over the deaths of two tiny Eisbär cubs in a Nuremberg zoo, who were presumably eaten by their inexperienced mother, Vilma, after zookeepers decided not to intervene. Then on Wednesday, a fresh round of photographs and videos revealed that a third cub at the same zoo had been "rescued" by zookeepers after another mother, Vera, showed signs of rejecting her offspring.

Much in the same way that tigers can’t behave instinctively in captivity, captive polar bears seem to have trouble properly raising cubs. And if the ‘rescued’ cub is raised by zoo employees it is deprived of the change to learn the behaviors of its species from the mother. Still, alive is better than dead, right? Or does practice make perfect’ for mother bears that need to learn how to care for their young in captivity? Is the purpose of the zoo to keep these animals alive at any cost, or is there a point at which we’ve only saved an empty husk of the beast that once was?

In other news, tomorrow is my first day at my new job. Wish me luck.

Formicidae Imports: The Argentine Ant

Wed, 27 Jul 2005 04:07:24 -0700

Here in Southern California it’s the height of ant season, and while I hear a lot of bitching and moaning about ants on peoples’ counters and ruining peoples’ food, I don’t hear much about ‘common’ ‘household’ ants as an invasive species. And yet, if you live in the southern United States, they probably are.

Linepithema humile. Image care of BugGuide.net.

Araucariaceae Ancestors

Tue, 17 May 2005 08:38:46 -0700

By now most people have heard of the ivory-billed woodpecker. News of its presumed extinction and seemingly miraculous rediscovery spread quickly after it was reported just over two weeks ago. Of course, the ivory-billed woodpecker is by no means the first species to be called extinct only to resurface years or decades later; in fact, only a week after the rediscovery of the ivory-billed woodpecker, three “extinct” species of snail were discovered in Alabama. The snails in question – the Cahaba pebblesnail (Clappia cahabaensis), the Cobble elimia (Elimia vanuxemiana), and the Nodulose Coosa river snail (Elimia lachryma) – didn’t get as much press though, because they aren’t what biologists call “charismatic megafauna,” a term used to describe large, attractive, and popular animals.

My favorite story of un-extinction is also not about charismatic megafauna. In fact, it’s not about fauna at all. It’s about flora.

A fossil of the thought-to-be-extinct Wollemi pine (Wollemia nobilis), along with a specimen from a living tree. Photo by J.Plaza RBG Sydney, care of WollemiPine.com.