The gang discusses two papers that look at live birth in squamates. The first paper is fossil evidence of live birth in an ancient snake species, and the second paper looks at the evolutionary pressures that might drive some lizards towards live birth. Meanwhile, James has advice for reptiles, Curt celebrates a belated "spooky season", Amanda continues to have extreme face blindness, and we are all haunted by a corrupted PDF.

Up-Goer Five (Curt Edition):

Our friends talk about animals that have cold blood but also have babies inside of them. The first paper looks at some old animals that have cold blood and no legs that have babies inside of them. These parts of the old animal with babies inside of them might be one of the first times that this has been seen for this group at this time. It raises some interesting questions about how and why these animals that most do not have babies inside of them might change to having babies inside of them. One thought was that maybe this happens when these animals with cold blood have to live in cold places, but this paper is not able to say if that is the case.

The next paper looks at a different group of cold blooded animals that is close to the other one but has legs. In this group, there are some animals that have babies inside and some that do not. The people who worked on the paper looked at all of the things about these animals, from how cold they liked it, how warm they liked it, where they are found, how many babies they had and how big they got, and other things to try and see if having babies inside is something that happens when these animals move into cold. What they found was very cool. Animals with babies inside did like it colder than animals without babies inside. But they found that having babies inside did not match with where these animals lived, and that animals with babies inside could be in warm places, and animals without babies inside could be in colder places. It might make it easier to be in colder places, but it did not look like it was because they were in colder places. This means that having babies inside is part of a bigger thing, like do you want to live fast or do you want to live slow; because animals with babies inside would have less babies than animals without babies inside.

References:

Chuliver, Mariana, Agustín Scanferla, and Krister T. Smith. "Live birth in a 47-million-year-old snake." The Science of Nature 109.6 (2022): 1-5.

Domínguez-Guerrero, Saúl F., et al. "Exceptional parallelisms characterize the evolutionary transition to live birth in phrynosomatid lizards." Nature communications 13.1 (2022): 1-12.