Palaeo After Dark

The gang takes some time to discuss two papers about agnostids, a strange group of trilobite-like arthropods whose evolutionary history has been the subject of considerable debate. First, we discuss a short paper summarizing the history of the agnostid debate, and then we discuss a brand new paper using new material and Bayesian phylogenetics to offer a fresh new hypothesis. Also, James channels frustration into fun, Amanda nearly has her house destroyed by cats, and Curt asks the Star Wars questions no one wanted answered.


Up-Goer Five (Amanda Edition):

Today our friends talk about small animals that have no eyes that might be sisters of animals that live in the water that have three parts and big eyes, many legs, and can make themselves into a ball. The first paper talks about the small animals with no eyes and how hard it is to make one of these animals for people to look at. They talk about the past of the animal and where it lived, and who it might be close sisters to. They say that a very cool area where we find these animals lets us see the legs and that they are different, also that they have a different mouth, and that maybe they actually do have eyes but they are on the mouth? They are weird animals. The second paper also talks about these animals, but does not focus on making the animals for people to look at. It looks at these animals from a different very cool area and shows their legs are sort of like the legs of animals that live in the water that have three parts and big eyes, many legs, and can make themselves into a ball. The paper is different from others, though, because it says that these animals are really either part of or sister to animals that live in the water that have three parts and big eyes, many legs, and can make themselves into a ball. But that is the only part of the tree that really is strong, so maybe who knows still? Our cat friend is writing this and did not really know what was going on that day, and does not know much about these cool animals with maybe no eyes that might really be animals that live in the water that have three parts and big eyes, many legs, and can make themselves into a ball.



Eriksson, Mats E., and Esben Horn. "Agnostus pisiformis—a half a billion-year old pea-shaped enigma." Earth-Science Reviews 173 (2017): 65-76. 

 Moysiuk, J., and J-B. Caron. "Burgess Shale fossils shed light on the agnostid problem." Proceedings of the Royal Society B286.1894 (2019): 20182314.

Direct download: Podcast_169_-_Learning_about_Agnostids.mp3
Category:general -- posted at: 3:00am EDT

The gang discusses two papers that look at the diets of past and present crocodylomorphs using patterns in teeth shape and enamel. It turns out, past relatives of crocodiles were likely a lot more experimental in the types of feeding strategies they implemented than we might expect. Meanwhile, Curt comes up with a great name for a Lamsdell lab bowling league, Amanda loves possums, and James has some very strong opinions about the “Cats” trailer.


Up-Goer Five (Curt Edition):

The friends talk about two papers that look at the teeth of these big angry animals that hide and eat a lot of animals. It turns out that lots of these big angry animals are sons and daughters of older big angry animals which may have ate other things besides animals. These two papers look at the teeth of the living big angry animals and the older big angry animals to see what we can learn about what they may have ate. The first paper looks at the hardest bits that cover the teeth. In living big angry animals, they find that the teeth furthest back in the mouth have more hard parts covering them than the teeth near the front. This makes sense, because these teeth in the back hold on to animals and so need to be more covered. What they also find is that these big angry animals have way less hard parts covering their teeth than other other animals which are warm, but who do not grow new teeth every time they lose one. The hard parts are the same as some other big angry animals from the past, though some of the big angry animals that might have ate more than just animals have the parts where their teeth are hard being different.

The second paper looks at the ways the teeth look. There is a number that can be looked at which shows if the teeth are simple or if they are very different. Simple teeth usually means that the animal eats other animals. But the more different the teeth are, the more the animal may eat both animals and not animals, or just not eat animals at all. They use this number to study what past big angry animals would eat. What they find is that past big angry animals probably ate way more different things than we see today. While most big angry animals today eat only animals, it seems that not eating animals at all, or eating both animals and not animals, happened way more often in these past big angry animals. It means that maybe these big angry animals have been a lot more different in the past, and our living big angry animals are maybe more "weird" than we think.



 Sellers, K. C., A. B. Schmiegelow, and C. M. Holliday. "The significance of enamel thickness in the teeth of Alligator mississippiensis and its diversity among crocodyliforms." Journal of Zoology

 Melstrom, Keegan M., and Randall B. Irmis. "Repeated Evolution of Herbivorous Crocodyliforms during the Age of Dinosaurs." Current Biology (2019). 

Direct download: Podcast_168_-_Alligator_Teeth_and_Too_Small_Cats.mp3
Category:general -- posted at: 3:00pm EDT