The gang discusses two papers that use fossil material to assess the origin of animal groups. The first paper describes a new Early Devonian fish and its implications for the evolution of jaws, and the second paper reassesses the fossil material of turtles (and possible not turtles) to determine where turtles fit on the evolutionary tree of sauropsids. Meanwhile, James invents new flavors, Curt breaks things down, and Amanda sets boundaries.

Up-Goer Five (Amanda Edition):

Today our friends look at two papers that talk about things showing up for the first time. The first thing to show up for the first time are teeth. Animals with inside hard backs have teeth, but how those teeth first show up are a big question mark. Turns out that teeth first show up as not-teeth and can actually grow over each other and grow in weird ways that today's teeth can't grow in. It also turns out that these early animals with hard backs and mouths that open and close had these sort of teeth and they're pretty much from the same stuff as the teeth we have today, so these are the same thing over time. The second paper our friends look at has to do with animals with inside hard backs that also have outside hard backs. We didn't know for a long time where these animals came from. Now we know, and they look at a really old weird animal that we thought might be one of those animals with inside hard backs that also have outside hard backs. But it isn't, it is too old and has inside parts of its head that don't look right. So now we know that animals with inside hard backs that also have outside hard backs are actually closer to animals with cold blood and big long faces that sit in water all the time and attack animals that come to drink water.

References:

Olive, Sébastien, et al. "A new 'acanthothoracid'placoderm from the Arctic Canada (Early Devonian) and its bearing on the evolution of jaws and teeth." Royal Society open science 12.9 (2025).

Jenkins, Xavier A., et al. "The phylogenetic origin of turtles." Current Biology (2026).