Friday, November 19, 2010

Tough Questions

What are the answers to these questions, anyway? For the first one, clearly not any single individual deinonychosaur would be able to spontaneously fly if it belongs to a taxon that can't fly to begin with. However, we do know that some small deinonychosaurs could probably fly. Presumably, a newly-hatched deinonychosaur wouldn't be able to fly, but we don't know how long it took for them to fledge.

For the second question, I suppose it also depends on what kind of neornithine we're talking about. Flightless ones will never be able to fly no matter how much they eat, but what about flying ones? Some birds feed their young every fifteen minutes. Assuming it generally takes around twenty days for these birds to fledge, they'd have eaten around two thousand insects by the time they leave the nest!

I don't think we can give a definite answer to the last question. My guess would be "a lot".

Wednesday, November 17, 2010

Puggles Part III

It's not uncommon these days to see paleo art depicting Mesozoic maniraptors feeding their young in the manner that many living maniraptors do now. But, in truth, this may not have been the case for most Mesozoic maniraptors.

Mesozoic maniraptors appear to have been most similar in reproductive habits to more basal modern birds such as palaeognaths, the tinamous and their flightless relatives such as ostriches and emus. Like many palaeognaths, male oviraptorosaurs and deinonychosaurs appear to have took multiple mates, who then laid their eggs in one big clutch. The males were probably the ones responsible for brooding the nests.

Also like palaeognaths (as well as basal neognaths such as the gallianseres - the pheasant and duck group), young oviraptorosaurs and deinonychosaurs could run and walk well as soon as they were out of the egg. As a result, they were probably quite capable of feeding themselves. One or both of their parents may have helped shelter them from predators and lead them to food sources, but when it came down to actually procuring the food, the hatchlings were most likely on their own.

So, unlike the blind and helpless young that early mammals probably had, theropods in general likely had very precocial young!

Now, it's still possible that these theropods fed their young on some occasions, as crocodiles (which are also archosaurs that have hatchlings which can hunt for themselves) have been observed feeding their young in captivity. But given the apparent rarity of this behavior, it's still safer to assume that most Mesozoic theropods didn't feed their young most of the time, if they did at all.

Wednesday, November 10, 2010

Puggles Part II

The intelligence of Mesozoic maniraptors is frequently exaggerated by pop culture and dinosaur fans, but it's good to point out that Mesozoic mammals probably weren't a whole lot more intelligent when the mammal enthusiasts get too above themselves.

Regarding Zahavi's line, the handicap principle is a hypothesis put forth by biologist Amotz Zahavi to explain why sexual selection often selects for characteristics that hinder their owners. According to this, these characteristics evolved because they hinder their owners. The idea is that, if a male can escape from enough predators and find enough food to survive to maturity in spite of such handicaps, he must be a very fine male indeed. There's a show on Animal Planet called The Most Extreme. Each episode focuses on a certain aspect of zoology (such as "Biters", or "Predators", or "Global Conquerors") and then lists the "top ten" animal contenders for that category. This isn't decided through anything particularly rigorous or scientific, but the show does contain some good information and I find it entertaining when I happen to catch it on TV. (It really messed up badly when one episode claimed that Tyrannosaurus rex was the ancestor of the Komodo dragon, however.) Either way, there was one episode I saw called "Fashion Disasters", which talked about how the physical features of some animals can cause difficulties for them, even eventually killing them. It's no surprise that seven out of ten of the contenders were in thanks to features they gained through sexual selection.

Of course, for the handicap principle to manifest at such a young age as a newly hatched monotreme would be detrimental and so probably wouldn't occur.