Did T-Rex Teens Crush Carnivore Competition?

Curt Bright Author

02/25/2021 Added

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Kate Lyons asks why there were so few dinosaur species and suggests juvenile T-Rex's may be to blame.

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[00:00:00.006](inquisitive music)
[00:00:01.230]In this research, we were interested in
[00:00:03.400]really just understanding dinosaur community structure.
[00:00:06.530]And we wanted to try and understand
[00:00:08.240]why there are so few species of dinosaurs.
[00:00:10.630]You know, throughout the entire history of dinosaurs,
[00:00:12.850]there's only about 500-ish species.
[00:00:16.850]And so there's this big question about
[00:00:18.580]why there are so few dinosaurs.
[00:00:21.482](dinosaur roaring)
[00:00:24.171]The hypothesis for that is this idea
[00:00:27.400]that these big tyrannosaur dinosaurs,
[00:00:30.840]the babies, and then the teenage dinosaurs,
[00:00:34.060]would have eaten different things than their adults.
[00:00:37.160]If you look at what the babies
[00:00:39.810]and the juvenile skulls look like,
[00:00:41.710]they would have transitioned from eating insects early on
[00:00:46.280]to eating other small vertebrates
[00:00:49.090]that are in the environment,
[00:00:51.010]until you get to the really big ones.
[00:00:52.820]What you end up with is one species
[00:00:55.150]that specializes on different things
[00:00:57.460]throughout its lifetime.
[00:00:59.000]What that means is that one species
[00:01:01.000]is out-competing multiple other possible dinosaur species
[00:01:05.210]as it grows.
[00:01:06.280]And so within any local area,
[00:01:09.140]you have small dinosaurs, and you have big dinosaurs,
[00:01:12.620]but you don't have anything in between.
[00:01:15.100]And that's really weird.
[00:01:16.755](dinosaur roaring)
[00:01:19.610]If we take what we know about dinosaur growth rates
[00:01:23.060]from their bones, and ask how many individuals
[00:01:27.300]at each life stage you would expect,
[00:01:29.880]what we find is that the majority of the individuals
[00:01:33.300]of these mega theropod species
[00:01:34.900]fall in this juvenile range,
[00:01:37.500]and they also fall within the gap.
[00:01:39.840]And so what that tells us
[00:01:41.500]is that the reason there are so few dinosaur species
[00:01:44.540]is because these mega theropods
[00:01:46.300]were out-competing any other potential species in this gap.
[00:01:50.737](dinosaurs growling)
[00:01:54.640]We were actually able to take information about
[00:01:57.500]what we know about how mammal communities are put together
[00:02:00.070]in the present, and how the distribution of body sizes
[00:02:04.350]of mammal species within a community
[00:02:06.450]look like in the present,
[00:02:07.740]and make predictions about what we would expect
[00:02:09.800]in this system of dinosaurs.
[00:02:11.620]It's a really, really different system.
[00:02:13.700]And our predictions were upheld,
[00:02:15.060]which is really great 'cause what it suggests,
[00:02:18.020]to me anyway, is that we are getting at fundamental ideas
[00:02:22.500]about how the world works.
[00:02:24.590]And that if you can take what we think we know
[00:02:27.760]about how mammal communities work,
[00:02:29.720]and make predictions about dinosaur communities,
[00:02:32.140]and come out with what we would expect to see,
[00:02:34.810]that's just really amazingly cool.

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Did T-Rex Teens Crush Carnivore Competition?

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