Category Archives: Palaeontology

Horseshoe Crab Fossil named after Darth Vader

This is fun. From the New Mexico Museum of Natural History and Science, the press release for a recent fossil naming:

A 245 million-year-old fossil horseshoe crab recently discovered in Idaho has been named Vaderlimulus because the animal’s shield head resembles the helmet worn by Darth Vader from the Star Wars film series. Paleontologists from the New Mexico Museum of Natural History and Science in Albuquerque (Allan J Lerner, Spencer G. Lucas) and the University of Colorado at Denver (Martin Lockley) just published a scientific article describing the extinct fossil horseshoe crab. Their findings were published in the latest issue of the German paleontological journal Neues Jahrbuch für Geologie und Paläontologie, which is the world’s oldest paleontological journal.

Vaderlimulus is the first North American fossil horseshoe crab from rocks of the Triassic Period. The Triassic was the first period of the Mesozoic Era (252 to 201 million years ago). Dinosaurs and mammals were just beginning their evolutionary development during the Triassic, but horseshoe crabs were already ancient by that time. Their fossil record dates back at least 470 million years ago, but fossils of horseshoe crabs are generally rare. When horseshoe crab fossils are found they are often new to science, as is the case with Vaderlimulus.

There are only four species of horseshoe crabs alive today, and their populations are decreasing. They are not true crabs but are more closely related to scorpions and spiders. Modern horseshoe crabs are often considered ‘living fossils’ due to having shown little apparent change in physical appearance over a vast period of geologic time.

“Vaderlimulus, however, has unusual body proportions that give it an odd appearance,” said lead author Allan J Lerner. This in part led the paleontological team to conclude that Vaderlimulus belonged to an extinct family, the Austrolimulidae. Members of this family were expanding their ecological range from marine into freshwater settings during the Triassic and often exhibit body modifications that provide them with a bizarre appearance by modern standards.

Did humans kill off the last dinosaur?

Classic dinosaurs went extinct long before humans existed. But birds are dinosaurs, and birds still exist. So, no.

But birds are not classic dinosaurs mainly because they are not extinct (a tautology) and they are not big and scary. But some of them were.

One of the last (but not the last) big scary bird-dinosaur creatures may have gone extinct because humans ate them, or more likely, ate their eggs. In Australia. Perhaps.

Anyway, I wrote this new finding up here, at 10,000 birds.

Dinosaurs Biting Other Dinosaurs In The Face

The number one rule of the Taphonomy Club is don’t talk about marks on bones … without placing them in context. Many marks on bones could have multiple causes, such as putative cut marks caused by stone tools on animal bones found on early hominid sites. In that case, hard sharp stony objects in the ground can cause marks that are hard to tell apart from stone tool marks. But when you find almost all the possible stone tool marks in the exact locations they would be if a hominid was butchering or defleshing the animal, then you can assert that that butchery or defleshing with stone tools was highly likely to have happened.

A similar logic has been applied by paleontologists DWE Hone and DH Tanke in their study of the fossil remains of a dinosaur from Dinosaur Provincial Park in Alberta, Canada. The dinosaur exhibits numerous bite marks, and apparently (unlike stone tool cut marks) identification of these marks as caused by carnivorous dinosaur teeth is not in question. But the location of the marks and other features allowed these scientists to argue that some sort of combat regularly occurred between members of members of the same species, or similar species, during the animal’s life. Given what is known about animal behavior and the kinds of dinosaurs around at the time, they claim that it is most likely combat between members of the same species.

The dinosaur in question is a juvenile Daspletosaurus. This is a genus of dinosaur extant in western North America between 77 and 74 million years ago (Late Cretaceous).

Since everyone knows all about Tyrannosaurus, it is helpful to compare Daspletosaurus to Tyrannosaurus. Daspletosaurus was smaller and older. Daspletosaurus ranged around 8 or 9 meters long and 2.5 tonnes, while Tyrannosaurus could be over 12 meters long and 10 tonnes. Tyrannosaurus also lived later (68 million years ago up to about the time of the great extinction). Both had short arms but Daspletosaurus’s arms were longer. Note that this kind of dinosaur, suborder Theropoda, gave rise to birds.

This particular juvenile Daspletosaurus was well preserved. Many of the bones are present, and their position in the matrix that bore them is not too far off from anatomical location. A good number of the missing bones may have actually eroded away after this part of the bone bed was exposed by erosion. There are marks on some of the bones that indicate post-death scavenging. But, most of the tooth marks are of the kind one would expect if a theropod dinosaur was biting it, and most interestingly, most of these marks show evidence of healing, and all but one mark indicating damage is on the head. Normally, theropod inflicted bite marks are found on various different bones of their prey. It appears that this individual was engaged in combat with other individuals of the same sort … other theropods. And, since this is probably the only theropod of this size at the time in the area, it is reasonable to conclude that this is evidence of infraspecific combat or competition.

From the study’s abstract:

Trace marks on the bones of non-avian dinosaurs may relate to feeding by large carnivores or as a result of combat. Here the cranium and mandible of a specimen of Daspletosaurus are described that show numerous premortem injuries with evidence of healing and these are inferred to relate primarily to intraspecific combat. In addition, postmortem damage to the mandible is indicative of late stage carcass consumption and the taphonomic context suggests that this was scavenging. These postmortem bites were delivered by a large bodied tyrannosaurid theropod and may have been a second Daspletosaurus, and thus this would be an additional record of tyrannosaurid cannibalism.

I contacted lead study author Dave Hone with a few questions and he was kind enough to give me answers.

I asked him if he had any guess as to the sex of this individual. While it is possible to sex some dinosaurs, he told me that this was not possible in this case.

I asked Dr. Hone to comment further on the suggestions that the most likely species to have inflicted the pre-mortum wounds was another Daspletosaurus, even though another similar dinosaur, Gorgosaurus, was around at the time. He told me, “We favour Daspleto for the premortem as we think (and based on previous papers) this is a more likely case with more intra than interspecifc aggression leading to these kinds of interactions,” similar to what we see in modern animals that exhibit this behavior. I also wondered if the size of the teeth could indicate the size of the offending beast, and thus confirm the species. He told me they did not look at this too closely because there are various problems with that approach. “We did look at the patterns of tooth distribution briefly but between different sizes of animals (juveniles vs adults) different sizes of teeth within the jaws (front vs back) and then things like missing teeth etc. there’s no way of separating them out. There’s just way too many variables and they are only leaving limited marks. It’s mostly hard to tell even very different animals apart from bite marks let alone two similar and close relatives like this.”

I asked how common Daspletosaurus is in the fossil record and if this was one of the more common tyrannosaurids. He told me that “Actually it’s not that common. The Albertan Tyrannosaurs are generally pretty common but we do for example have more Gorgosaurus and Albertosaurus than Daspleto,” though Daspletosaurus is well represented.

Daspletosaurus is distinct in part because of various extra bony bits in the face and around the eyes, which could be for any of a number of functions. I asked if it is possible that Daspletosaurus was more involved with usually-but-not-always non-lethal infraspecific combat than other tyrannosaurids, if these features are related to what might have been extra protection (or signaling features that might arise from sexual selection). If so, would this indicate something about social structure? He told me, “I’m very wary of making these kinds of extrapolations as some things that look like certain classic signals turn out not to be. My personal opinion is that these hornlets in various Tyrannosaurs likely did function in sociosexual signaling (at the very least I suspect they wouldn’t do much to protect the eyes since that would be tricky place to bite) but it’s hard to say much. Sociality is misleading here as some things can be very social and fight lots and others almost never and vice versa for solitary animals.”

I also wondered about how infraspecific combat square with the individual being relatively young. Would this imply it was fighting off adults intent on cannibalism? Or, were juveniles fighting it out like hyenas do (new born hyena males from the same litter engage in deadly combat)? Or fighting over food? Or engaged in ritual fighting behavior that precedes, as preparation/practice, adult fighting behavior? I wondered if this would say anything about life history development of behaviors in this dinosaur. Dr Hone told me that “it is really hard to say. This isn’t an adult, but then nor is it really a juvenile. We know that some dinosaurs at least can reproduce before they are fully grown (so they are sexually mature when they are not osteologically mature – actually rather like humans, though obviously rather unlike most mammals, and certainly birds). So things get complex fast. This animals was certainly old enough to have been fully independent (though of course they may or may not have been gregarious / social etc.). I doubt cannibalism was normal, I’m sure there were the odd fights that resulted in deaths or adults killed the odd small juvenile (just like crocs do) but it’s a rare behaviour to go after other big carnivores for food – they are rare and dangerous, so stick to baby herbivores. After that it gets even harder so I’d prefer not to speculate too much, though I’d guess that IF solitary, smaller individuals would probably not be holding territories, since they are not big enough to defend them, and obviously immature animals would not be competing for mates or breeding sites or IF in a group to be an alpha of some kind (though that’s not to rule out some aggression to maintain even a lower rank), but it’s not much to go on – just too many unknowns.

What we need, obviously, is some way to bring these creatures back to life so we can observe them alive!


Caption for the figure at the top of the post: Figure 1: Skull in right lateral view showing numerous injuries indicated with black arrows and the relevant code letter (see the text for details).

The evolution of four-winged birds

…When we look at living species (A and B) that we know shared a common ancestor resembling one of them (A), we can guess that the features seen in A evolved in steps more or less linearly to eventually resemble the corresponding features seen in B. For example, we think that chimpanzees and humans shared a common ancestor that resembled chimps a lot more than humans, and in fact, we consider living chimps to be a pretty close analog to this common ancestor. Chimp teeth are somewhat larger in relation to body size than human teeth, and human teeth have somewhat thicker enamel than chimp teeth. This might suggest that chimp-like teeth transformed over time, step by step, in a linear fashion, to become human-like … slightly smaller and somewhat thicker enameled … over evolutionary time.

That would be a reasonable hypothesis, but it would be wrong. When we look at the teeth found among fossil remains of human ancestors and their relatives, we clearly see that the creatures that arose form a chimp-like ancestor bore teeth are as different from both chimp and human teeth as one might see anywhere in the fossil record of mammals evolving over a few million years. …

Read all about it here in my latest post on 10,000 Birds.

The seductive siren of soft tissue preservation: Ancient dinosaur flesh wasn’t ancient. Or dinosaur flesh.

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An ugly fact killing a beautiful hypothesis
I’m not mentioning any names, and don’t ask me any details. In fact, don’t repeat this story.

Some years ago, when I was a mere graduate student, a fellow student working in an unnamed country in Africa discovered a very very old stone artifact. To this day, this bit of chipped stone debris, representing the activities of an ancient very pre-human hominid, is one of the oldest well dated, in situ objects of its kind known.

The stone had some yeck on it, and for giggles, this stone got passed on to a physicist who had invented a new way of looking at small things. He was going to look at the tool to see what the yeck was. I should point out that this physicist had no knowledge to speak of of either archaeology or geology.

Right away results came back clearly indicating that the yeck was made of apatite. Apatite is, of course, the primary mineral constituent of bone. Was this a piece of ancient bone jammed into the micro-bumpy surface of an ancient stone tool?
Continue reading The seductive siren of soft tissue preservation: Ancient dinosaur flesh wasn’t ancient. Or dinosaur flesh.

An Evolutionary View of Humans 3: Remembering Names

Efe people
Ituri Forest
Anthrophoto is an
excellent source for
anthropology stock
photos

How good are you at remembering names? If you are really good … if you can hear someone’s name once and always remember it … you have a calling as a politician. If you would otherwise suck as a politician, but are good at explaining things, maybe a job as a teacher (but that requires other skills as well). In any event, you are a rare bird.

Humans have typically lived in small groups. This is especially true of foragers. Not only are these groups fairly small, but they are also fairly stable. The movement that does occur between groups is typically restricted to a larger “meta-group” consisting of a few different small groups. In other words, if you are a forager sitting around with the people you live with … the people in your “residence group” as we call it … the person sitting across from you is most likely someone whom you’ve known all your life (or visa versa, depending on your relative age).

Just as importantly, the total number of people you will know during your entire life well may stay in the hundreds. That’s total. Compare that to your own “Western” experience. Count the people in each neighborhood you’ve ever lived in (whom you knew), the people in all the different grades of school you’ve been in, and the people at all the different workplaces you’ve worked in. That is probably a large number. If it is a small number, then you don’t’ get out enough. You should get out more. At least go see a movie or something…

The point of this is that remembering names is something we have not evolved to do well for at least two reasons: 1) Everybody you run into is someone you already know (most of the time) and 2) Everybody you know is someone you’ve known for a long time, so you get a long time to remember their names.

There may be another aspect of this as well, but I simply do not know how broadly this applies across forager societies. In at least some societies, it is typical to use personal names only rarely. The day to day conversation among people in many camps and villages of which I am aware makes reference to people by kinship or other generic terms, not names. During my research in the Ituri, I participated in a long term project (as a trained helper) in which we collected demographic and physical data from a large sample of people. This was something all participants in the project agreed to do in order to maintain and grow a large and important data base. As part of this a couple of us would show up in some camp (of Efe) or village (of the horticultural Lese people in the same area) and run down the list, checking off who was still in the village, getting a body weight, a few other bits of information, etc.

There were times when I would ask, say, Joe, who that person over there was (to avoid the embarrassment of not knowing) and Joe would say “oh, that’s my sister.” Then I would say “what’s her name, you have two sisters” and Joe would yell across the compound “Hey dad, what’s my older sister’s name…”

Wow.

This would be partly because Joe would normally refer to his sister as “my sister” rather than by her name, and partly because nine years ago, Joe’s sister had a baby boy named, say, Frank, and has been since known as “mother of Frank.”

(There are of course other occasions, well known in anthropological circles, where a person cannot say a certain other person’s name. Maybe your culture prohibits you from naming an inlaw, for instance. I am not talking about this situation here.)

The point is that the Western concept of personal names and how they are used is fairly culturally specific. What seems like a common deficit, the general difficulty we have in remembering names when we first hear them, is actually quite expected.

There reason you can’t remember anyone’s name is because there are too many names to remember and you haven’t had a chance yet. And evolution. Not your fault.

An Evolutionary View of Humans 1: Introduction
An Evolutionary View of Humans 2: Sleep
An Evolutionary View of Humans 3: Remembering Names
An Evolutionary View of Humans 4: Sharing
An Evolutionary View of Humans 5: The Opposite Sex