Palaeo After Dark

The gang discusses two papers that have very little in common with each except for the word "stem". The first paper uses birth death models to simulate the fossil record in order investigate if neutral models can produce patterns similar to the "crown"/"stem" evolutionary dynamics that have been observed in real data. The second paper investigates stem mandibulate fossils to investigate the timing of major key innovations in the evolutionary history of this arthropod group. Meanwhile, Amanda decides, James bullies, and Curt explains.   Up-Goer Five (Curt Edition): The friends talk about two papers that have very little to do with each other, other than the fact that they have one of the same words in them. The first paper looks at the ways in which animals change over time and how they make more of each other and how the ways things live and die can make it look like there are some groups that do better than others. The paper shows that some of this is something we should see even if it is just because of how things make more things and the fact that we care more about the things that live today than the things that do not live today. The second paper looks at how animals that have many parts that repeat make their arms and legs. This paper looks at very very old animals from groups that are not around today but maybe could be close to those groups. The group of animals today that this group is close to has a lot of things that all of them share, like that they make mouths from a lot of arms, and also they have things on the front they use to feel things, and that they are three parts. This paper is using these old animals that are close to this group to try and see which things today in this group appeared first, and which things may have taken some time before they appeared.   References: Budd, Graham E., and Richard P. Mann. "The dynamics of stem and crown groups." Science Advances 6.8 (2020): eaaz1626. Liu, Yao, et al. "A tiny Cambrian stem-mandibulate reveals independent evolution of limb tagmatization and specialization in early euarthropods." Scientific Reports 15.1 (2025): 19115.

The gang discusses two papers that investigate injuries in fossil bones. The first paper tests hypotheses about the causes of facial injuries in herrarasaurids, and the second paper tests if inferred hunting strategies map onto injury patterns in predators from the La Brea Tar Pits. Meanwhile, Curt provides some hypotheses, Amanda gets spiritual, and James is photogenic.   Up-Goer Five (Curt Edition): The friends talk about two papers that look at why animals from a long time ago got hurt. The first paper looks at some very old and angry animals with no hair that all got hurt in the face. They try to see why these animals got hurt in the face. They look at all the ways that they could have got hurt in the face and find that it was probably other animals just like them that they lived with that probably hurt them in the face. The second paper looks at two groups of animals that eat other animals. One group of animals is man's best friend, and the other group of animals is from a group that does not care if man lives or dies. Since these two groups of animals are old and from a long time ago we don't know really what they ate but we use other things to come up with thoughts on how they could eat. We look to animals today that are like these animals and think that maybe these old animals ate the same way. But, trying to eat other animals is hard and can get you hurt, and you can get hurt in a lot of the same ways if you jump or run. This paper looks at how they got hurt to see if this fits with how we think they would eat. Turns out that the ways they were hurt makes sense if they ate way we think they ate, with man's best friend running and man's not best friend running.   References: Garcia, Mauricio S., Ricardo N. Martínez, and Rodrigo T. Müller. "Craniofacial lesions in the earliest predatory dinosaurs indicate intraspecific agonistic behaviour at the dawn of the dinosaur era." The Science of Nature 112.2 (2025): 1-12. Brown, Caitlin, et al. "Skeletal trauma reflects hunting behaviour in extinct sabre-tooth cats and dire wolves." Nature Ecology & Evolution 1.5 (2017): 0131.

The gang discusses two papers that use taphonomic experiments to test hypotheses about the paleo-environmental conditions of the Crato Formation. Meanwhile, Amanda has her daily requirements, James longs for the rack, Curt launched a new podcast concept, and no one on this podcast can keep to a topic for longer than five minutes.   Up-Goer Five (Curt Edition): The friends talk about two papers that look at rocks that come from the same place. This place is a spot where you get a lot of soft things from animals in the rocks which would usually not be able to be in the rocks because they would get broken up and lost. These two papers look at the types of animals we see in these rocks to see if that can tell us about the place where these animals with very soft parts were able to be saved. The first paper looks at small animals with many legs that stick their food with points on their mouth. When these animals die their legs are pulled under them. But in these rocks, the legs are not like that. The people who wrote this paper took some of these animals and put them in water and also water with stuff in it that you put on food and makes food good to eat. They found that the animals in the water with the stuff that makes food good had legs that look like looked like the rocks. This would mean that these animals were in water that had this stuff in it. The second paper looks at other small animals with soft things. These animals need to live in water and would not do well if the water had the stuff in it that the other paper said it did. Some people have said that maybe this means the animals got put in here and did not live in here. So the people who wrote this paper took dead animals and shook them to make it like they were moved to see what happened. They found that they could not have been moved because they break up easy when you try to move them. This means that the water must have had some times when it was just water and some times when the water had lots of stuff in it that makes food good.   References: Downen, Matt R., Paul A. Selden, and Stephen T. Hasiotis. "Spider leg flexure as an indicator for estimating salinity in lacustrine paleoenvironments." Palaeogeography, Palaeoclimatology, Palaeoecology 445 (2016): 115-123. Storari, Arianny P., et al. "Taphonomy of aquatic insects from the Crato Formation Lagerstätte (Aptian, Lower Cretaceous) under an actualistic look." Plos one 20.9 (2025): e0331656.

The gang discusses two papers that provide nuanced information to test when key innovations in vertebrate evolution occurred. The first paper looks at unique semi-terrestrial trace fossils in the early Devonian in order to determine the trace maker, and the second paper looks at fossils that could provide information about the origins of teeth. Meanwhile, Curt has theme park ambitions, James provides Amanda with new anxieties, and Amanda leaves it all to chance.   Up-Goer Five (James Edition): The group talk about two papers that are looking at the earliest time things have been seen in the rocks. The first paper looks at some tracks in the rock left by animals with no legs that live in the water but can gasp air. We have looked at tracks from the same place before where the animals stuck their faces into the ground. The new tracks come in two forms. The first is where the animal took a rest and its bits that it uses to move in the water stuck in the ground. The other track is where it had to come out of the water and moved around on land. It used its head to pull it along as it moved. The track made by this is the same as tracks made by the same type of animal that still lives today. This is the oldest case of this type of animal moving on land and shows that animals with hard parts inside them began to move onto land in lots of different ways. The other paper looks at the supposed earliest time we find teeth growing on skin. This is interesting because there are several ideas about why the teeth began to grow on the skin, so when it first started could help tell which of these reasons is true. The skin teeth bit has been considered the same as an animal with no legs that lived in the water that was found in younger rocks from a different place, but when studied up close it does not look like the thing it is named as. By using lights to look inside the rock and seeing whether it looks the same as skin teeth on living animals it is shown that the old skin teeth are not skin teeth at all but actually are parts of the skin of a different animal with no hard parts inside that has legs that move in many places.   References: Haridy, Yara, et al. "The origin of vertebrate teeth and evolution of sensory exoskeletons." Nature (2025): 1-6. Szrek, P., et al. "Traces of dipnoan fish document the earliest adaptations of vertebrates to move on land." Scientific Reports 15.1 (2025): 28808. Falkingham, Peter L., and Angela M. Horner. "Trackways produced by lungfish during terrestrial locomotion." Scientific Reports 6.1 (2016): 33734.

The gang discusses two papers that deal with fossil brains. The first paper looks at a fossil arthropod from the Cambrian and uses neurological characters to determine its phylogenetic placement. The second paper looks at a synapsid braincase and tries to infer why this one species has lost its parietal eye when other members of the species have he eye. Meanwhile, Curt invents some new sponsors, Amanda has plans for James, and James discusses some personal growth.   Up-Goer Five (Curt Edition) The friends talk about two papers that look at very old brains in animals that are long gone. The first paper is the brain of animal from a very long time ago that would grow by taking off its skin when it needs to get bigger and is made of many small bits stuck together. This animal was really weird for a long time, but the people who wrote this paper found one of them that had its brains still in it. They looked at the brains and they looked at the brains of other animals from the past and animals around today and they saw that this brain looked a lot like the brains of a group around today that some of the animals make things to catch food and live in out of their bottom. So the people who wrote the paper say this could mean that is maybe a very very very old animal from that group or close to it. The second paper looks at the hard bits that hold the brain in for an animal that is close to the animals today that have hair and are warm. This animal may not have had hair and may not have been warm, but what the people who wrote the paper are looking at is the spaces in the hard bits that hold the brain. In animals that do not have hair and are cold, there is a space at the top of the head for an eye that can see light and dark. In animals that are warm, they lose this eye. The old animal they are looking at has some animals in the group that have that eye who live in cold places. The animal they are looking at does not have this eye, and so the question is why? They look at everything and they think that it is because the animal without the eye lives in places that are always warm and where day and night don't change that much. This would mean they would not need this light dark eye as much.   References: Strausfeld, Nicholas J., David R. Andrew, and Frank Hirth. "Cambrian origin of the arachnid brain." Current Biology 35.15 (2025): 3777-3785. Benoit, Julien, and Jaganmoy Jodder. "The palaeoneurology of a new specimen of the Middle Triassic dicynodont synapsid Kombuisia frerensis." Acta Palaeontologica Polonica 70.2 (2025): 369-374.

The gang discusses two papers about skin preservation in fossil tetrapods. The first paper describes skin impressions from a Permian synapsid, and the second paper identifies feather-like structures in an early Triassic diapsid. Meanwhile, James considers the horse, Amanda shames extinct animals, and Curt quotes "philosophy".   Up-Goer Five (Amanda Edition): Today our friends talk about things that are sort of close to things with hair but not that close to things with hair. They are closer to things with hair than to things with dry skin with no hair or long many-part skin things. Anyway for a long time we did not know what the skin of the animals that are sort of close to things with hair looked like. Did they have dry skin with no hair like the things today? Or did they maybe have hair? We didn't know, but now we have found marks in the ground that show that they had dry skin with no hair, but it looks different than the animals with dry skin and no hair today. So hair comes around after the dry skin with no hair does. Then our friends talk about a very weird little animal that is sort of somewhere close to animals with dry skin and no hair, but it has these really weird things that come off of its back that look kind of like the many-part skin things on the most flying animals that are around today. But it's really not the same many-part skin things, because all the parts are not really same. And also there is only one of them and not one on each side. So it might be that many-part skin things come earlier than people thought they might have.   References: Marchetti, Lorenzo, et al. "Early Permian synapsid impressions illuminate the origin of epidermal scales and aggregation behavior." Current Biology 35.11 (2025): 2752-2759. Spiekman, Stephan NF, et al. "Triassic diapsid shows early diversification of skin appendages in reptiles." Nature (2025): 1-7.

The gang ends "Wet Hot Archosaur Summer" with the final podcast recorded from our undisclosed location in the woods. For this podcast, we indulge Amanda by talking about birds and trace fossils. The first paper looks at the remains of nesting sites that date back to the Cretaceous, and the second paper investigates sources of error in estimates of avian maximum speeds from trace fossils. Meanwhile, Amanda has a message for the bears, James proposes an alliance with the crows, and Curt does an "homage".   Up-Goer Five (Curt Edition): The friends talks about two papers that will make one of them very happy because they are all about the ways that animals that fly can make marks on the ground to let us know about how they move. The first paper looks at where these animals that fly will make their home. This paper shows that animals that fly have been found in this cold place near the top of the world for a really long time. This place would not have been as cold as it is today, but would have been dark for half the year. Some of the animals they find in this area look like they would have moved in when things were good and left when things got bad. This is something we see animals that fly do today in the top of the world as well. The second paper looks at how we try and use how these animals make marks on the ground to see how fast they would move. The paper shows that the way we were doing it in the past kind of worked, but also didn't work. This is because when these animals that can fly move, they do not move in the same way as other animals all the time. And so the way that these things walk is important if we want to try and understand more about how fast they could move from the marks on the ground.   References: Wilson, Lauren N., et al. "Arctic bird nesting traces back to the Cretaceous." Science 388.6750 (2025): 974-978. Prescott, Tash L., et al. "Speed from fossil trackways: calculations not validated by extant birds on compliant substrates." Biology Letters 21.6 (2025): 20250191.

The gang is all back together in one place again as they unite in an undisclosed cabin in the woods to record the last two podcasts for Wet Hot Archosaur Summer. For this episode, the gang talks about herbivorous pterosaurs and wadding T-rex. Meanwhile, James experiences relative sobriety, Curt welcomes everyone to the Great Northern, Amanda is fueled by spite, and we all get completely off track.   Up-Goer Five (Curt Edition): The friends are together for the first time in a long time and so they have a lot of fun together and sometimes they talk about a paper or two. The first paper that they sort of talk about is about big angry animals that fly and are no longer around. This paper looks at one group of these big angry animals and finds that they have bits and pieces of things that are found in green things that make their own food from the sun. They do a lot of things to make sure that these bits are found inside these animals and they use this to say that this one group of big angry animals probably ate these green things. The second paper looks at how big angry animals moved and how fast they could move in air or in water. This is because some big angry animals that are in all of the movies are said to maybe not be as fast as the things they would eat. This paper says maybe they chased food into water where they would be faster. The friends point out that other animals today do not have to be faster than the animals they eat, but sure... go off.   References: Blanco, R. Ernesto. "Tyrannosaurus rex runs again: a theoretical analysis of the hypothesis that full-grown large theropods had a locomotory advantage to hunt in a shallow-water environment." Zoological Journal of the Linnean Society 198.1 (2023): 202-219. Jiang, Shunxing, et al. "First occurrence of phytoliths in pterosaurs-evidence for herbivory." Science bulletin (2025): S2095-9273.

Wet Hot Archosaur Summer continues as the gang discusses two papers that look at the evolution and biogeography of early archosaurs. Specifically, one paper describes new material from an early dinosaur group, and the other paper looks at the niche preferences of early pterosaurs and their closest sister group, the lagerpetids. Also, James tries out a new flavor, Curt likes consistency, and Amanda provides some ASMR.   Up-Goer Five (Curt Edition): The friends look at two papers about the early types of animals that would give us lots of different types of big angry animals like the big ones that everyone thinks of and the ones that can fly. The first paper looks at one of these early animals which we don't know much about because there is not a lot of it left. This paper talks about some new stuff that was found which helps us better know what this animals is. We first thought that maybe it was one of the earliest animals, but this paper says that it may be more like some of the big animals that we talk about all the time because they are in big movies like the one that came out this year. The second paper looks at two groups of animals that are close to each other, one of them can fly and one that does not fly. These two groups were around at the same time. This paper looks to see where they lived and what types of places they wanted to live in. They find that these two groups did live sort of the same place, but places where the things that fly would like to live were also places that the other group that did not fly did not like to live as much. The other thing they find is that, even though the group that did not fly was not as long lived as the group that did fly, during the time they are looking at it lived in a lot of places and did very well. A big bad thing happened at the end of this time that is probably why this group went away and the group that could fly was able to do better.   References: Müller, Rodrigo Temp. "A new "silesaurid" from the oldest dinosauromorph-bearing beds of South America provides insights into the early evolution of bird-line archosaurs." Gondwana Research 137 (2025): 13-28. Foffa, Davide, et al. "Climate drivers and palaeobiogeography of lagerpetids and early pterosaurs." Nature Ecology & Evolution (2025): 1-14.

The gang discusses two papers about the ecology of sauropods. The first paper investigates the biomechanics of the Plateosaurus tail, and the second paper looks at direct evidence of sauropod diet from gut contents. Meanwhile, James "makes it interesting", Amanda may have recorded on the wrong microphone, Curt makes a bold rebrand, and everyone vaguely remembers "Denver: The Last Dinosaur".   Up-Goer Five (Curt Edition): The friends talk about two papers that look at animals with along necks from a long time ago that kids love and were in a movie where one of them called Little Foot went to a great low place between big places. The first paper looks at one of the oldest groups of animals with long necks that had really long things coming out of their bottoms. Some animals use these long things to match how heavy and long their necks are, but some use these long things to hit other animals. Since this group did not have a lot of things to hit other animals that may try to eat them, it would make sense that maybe they used their long things off their bottom to do it. They look at other animals from today and the past to see if this animal could use its long thing from its bottom to hit other animals. And they find that it could. The second paper looks at what one of these long neck animals would eat. They find some parts of one of these animals that died when it was eating, and the bits that it ate were still in its body when it died. They find bits and pieces of things that can make their own food, and they also find that the animal was not very good at breaking up its food in its mouth.   References: Poropat, Stephen F., et al. "Fossilized gut contents elucidate the feeding habits of sauropod dinosaurs." Current Biology 35.11 (2025): 2597-2613. Filek, Thomas, et al. "Tail of defence: an almost complete tail skeleton of Plateosaurus (Sauropodomorpha, Late Triassic) reveals possible defence strategies." Royal Society Open Science 12.5 (2025): 250325.