Podcast 337 - Smol Beeg Animals

The gang discusses two papers that look at early tetrapods. The first paper investigates the transition to terrestrial environments in early tetrapods, and the second paper looks at some very small Dimetrodon. Meanwhile, Amanda has a disproportionate cat, James talks smack about a dead synapsid, and Curt gives gardening tips.

Up-Goer Five (Amanda Edition): This week our friends look at two papers on animals with hard bits in their back and four legs. The first paper asks when did animals with hard bits in their backs and four legs first start doing a big change as they grew up. Today the sort of early group of animals with hard bits in their back and four legs are really not that early and are actually really different but a lot of people use them to talk about early animals with hard bits in their backs and four legs. They do a big change as they grow up. They start out using water to breathe and then change to breathing air. Some of them grow legs when they don't start with legs. People like to say that this means early animals with hard bits in their back and four legs also must have done a big change as they grew. But actually maybe not, because old animals with hard bits in their back and four legs don't show the big change at all. So it seems like maybe the big change either came about once before a big branch between groups, and then went away in animals with hard bits in their back that live on land, or it came about twice in two different groups of animals that do a big change as they grow, one of which might have become the living group of animals with hard bits in their back and four legs that do a big change and live in both water and on land. Both of those might have been the right answer but we can't tell right now, we need more old animals to find out. The second paper is about a animal with hard bits in its back and four legs that is close to animals with hair, but probably did not have hair. Instead it has a big back with things sticking out and skin on it. These ate other animals and were really important when they lived. But the paper looks at animals in this group that are small. It's very different too because many of these animals are found in one part of the world, but one of the small ones is found far away. It's the only one not found with all the others. The other small one is found with all the others. This paper wants to find out why are they small and do they get small in the same way, so they cut up the inside hard parts and look at them really close and find that they actually get small in different ways because they can see how they grow when they look at the inside hard parts up close. They also think that the animals that lived in the far away place from the others were small for a different reason, because the place they lived was not great and they maybe didn't have a lot of food to eat. The small ones that are found with all the other animals were small because there were all those other animals with big backs with things sticking out and skin on it that would fight it. So they probably lived more in water and ate fish, maybe.

References: Pardo, Jason D., and Arjan Mann. "Direct development of stem tetrapods across the fin-to-limb transition." Science 392.6804 (2026): 1292-1296. Canoville, Aurore, et al. "Contrasting life history in the diminutive Dimetrodon species from North America and Germany." Scientific Reports 16.1 (2026): 16279.