The gang discusses two papers that look at the complicated path tetrapods took to getting on land. The first paper looks at a more derived stem tetrapod that went back into the water, and the second paper uses trace fossils to investigate the foodweb of a community dominated by some early tetrapods. Meanwhile, Amanda has a friend over, James knows how to be silent, and Curt teaches everyone that things continue to exist even when we don’t see them.

Up-Goer Five (Curt Edition):

Our friends talk about two animals that are great great great great great great father and mother to all of the animals that are on the land. But these animals did not all make their way on to the land in a simple way. The first paper looks at an animal that looks like it went back into water. This animal has all of the parts that you need to live well in the water, even though it also has parts from animals that would be on the land, or at least spending some time on the land. This means that the way on to the land has a lot more steps forward and back than we like to think.

The second paper looks at the places these animals were living in and tries to use the parts that are around and how they were hurt to see what may have been eating what. People have thought that these animals went on to the land to get away from things that might have been eating them. This paper shows that those animals might have been the things that were eating other animals. It seems like being one of these animals that lives in the water was a pretty good way to live.

References:

Robin, Ninon, et al. "Vertebrate  predation in the Late Devonian evidenced by bite traces and  regurgitations: implications within an early tetrapod freshwater  ecosystem." Papers in Palaeontology 8.4 (2022): e1460.

Stewart, Thomas A., et al. "A new elpistostegalian from the Late Devonian of the Canadian Arctic." Nature 608.7923 (2022): 563-568.

The gang discusses two papers that look at the evolutionary changes occurring in early synapsids. The first paper suggests that some synapsids may have evolved a mammal-like walking gate and respiration earlier than we expected, and the other paper uses the inner ear of synapsids to infer body temperature. Meanwhile, James is adapting to a new environment, Amanda drinks some “tea”, and Curt gives acronym advice.

Up-Goer Five (Curt Edition):

Our friends talk about two papers that look at animals which are not the animals today with hair and warm blood but are part of the group that is brother and sister to those animals. These animals were around a long long time ago. These papers show that some of the things we see in animals with hair and warm blood today also happened in some of these other animals too. The first paper looks at a hard part inside the chest of these other animals. Most of these other animals have a hard part that is very different from the one we see in the animals with hair and warm blood. However, on group of these other animals seems to have a hard part that looks a lot like the ones we see today in animals with hair. This hard part is important for how we breathe and also how we move. This means that this group may have walked and breathed like the animals who have hair today, even though animals with hair got this hard part much later.

The second paper looks at the ear to see how warm the blood is for these other animals that are not animals with hair but are part of the group. This paper uses the water stuff in the ear to try and figure out how warm these animals would be. They look at the ear for a lot of dead animals from this group, as well as animals around today that we can see how warm they are. When they use what they find today on the very old dead animals, they see that there is a point in the past of these animals where they start to really get warm. This is still earlier in the group than our animals we have around today with hair that are warm.

References:

Bendel, Eva-Maria, et al. "The  earliest segmental sternum in a Permian synapsid and its implications  for the evolution of mammalian locomotion and ventilation." Scientific Reports 12.1 (2022): 1-9.

Araújo, Ricardo, et al. "Inner ear biomechanics reveals a Late Triassic origin for mammalian endothermy." Nature (2022): 1-6.