A New Dinosaur Family Tree

Last week, a [study] was published that changed the fundamental relationships among dinosaurs. Traditionally, and for the last 130 years, dinosaurs have been split into two main groups: saurischians (‘lizard hipped dinosaurs’) and ornithischians (‘bird hipped dinosaurs’). The saurischians include the giant, long-necked sauropods, the meat-eating theropods, and eventually modern birds. The ornithischians include the horned dinosaurs, the armored dinosaurs (like Triceratops and Ankylosaurus), and the duck-billed dinosaurs.

The traditional view of dinosaur relationships.

This main distinction occurs because of differences in the hips of these dinosaurs, hence the names. The hips are made of three bones: the ilium, the ischium, and the pubis. The ilium attaches the other two bones to the spine. The ischium forms the back of the hips. The pubis forms the front. In saurischians, the pubis points forward, very similar to the hips of modern lizards. In ornithischians, the pubis points backwards, very similar to the bones of modern birds. Now we know that birds are actually saurischian dinosaurs, but we didn’t know that when these groups were named.

The differences in dinosaur hips. The dinosaur’s head would be to the left in these images. The ilium is in blue, the ischium is in red, and the pubis is in yellow. In saurischian dinosaurs, the pubis points forward. In ornithischian dinosaurs, the pubis points backwards. Source of image unknown.

The new study focused on the earliest dinosaurs. Here are the specifics: they examined 74 species and 457 characteristics of their bones and ran an analysis in a computer program called TNT (Tree analysis using New Technology). This program looks for the simplest way the characteristics can fit on an evolutionary tree, while creating the fewest amount of changes (a principle called parsimony).

This analysis found that the ornithischian dinosaurs are more closely related to the theropod dinosaurs and that saurischian dinosaurs are most closely related to a group called Herrerasaurids.

The new relationships among dinosaurs.

So, saurischian dinosaurs were split into two groups. This leads to at least one major problem: the definition of Dinosauria. Dinosauria is defined as: Megalosaurus (the first theropod discovered), Iguanodon (the first ornithischian discovered), their most recent common ancestor, and all of its descendants. When dinosaurs were split into two main groups, using Megalosaurus and Iguanodon to anchor the definition made sense because it included all of the animals we recognize as dinosaurs within the definition. Now that theropods and ornithischians are closer relatives, this definition would exclude the sauropods and herrerasaurids from the definition.

The traditional definition of Dinosauria. With the new relationships, sauropods would be outside of the dinosaur tree.

To fix that, the authors redefined Dinosauria as the least inclusive clade that includes Passer domesticus (the sparrow: a theropod), Triceratops horridus (an ornithischian), and Diploducus carnegii (a sauropod). That includes all the dinosaurs, and will keep including everyone even if the relationships in the tree change.

The new definition of Dinosauria is anchored with a species from each group, so even if the relationships change, all the dinosaurs are still included in it.

As interesting as this analysis is, there are issues with it. The main issue is that it’s the only analysis that gets this result. That’s not to say that it’s wrong! We just need to get the same answer with a lot more analyses before we start re-writing textbooks. Some of the technical aspects of the methods seem… off… as well, but I won’t get into those details until I can do more research. Basically, this is an interesting result and one that we should keep our eyes on, but we need more data to support it before we’re all on board.

*All skeletal images from Scott Hartman. Passer image from Birds of the World Handbook.

My Little Pony

Climate Change. It’s a topic that’s been in the media recently for a number of reasons, namely because we’re experiencing it now. We know that because we have climate records going back to 800,000 years (possibly [1.5 million years]) from ice cores. The gases trapped in the ice are made up of the atmosphere that was around when the ice formed. The atoms that make up the gas, like oxygen, carbon, and hydrogen, have different values of positive and negative particles (different isotopes) that relate directly to the temperature the planet was at the time. That’s how we know what temperature the planet used to be and how we can plot the data and form predictions about what the future holds (spoiler alert: it’s gonna get hot). For more on that, watch the video at the bottom.

This graph shows carbon dioxide levels over time. The higher the level of carbon dioxide, the hotter the temperature. From NASA. Credit goes to Vostok ice core data/J.R. Petit et al.; NOAA Mauna Loa CO2 record.

A [paper] was published this week that analyzed these same isotopes from the past. The Earth has gotten hotter in the past. One of these times, called the Paleocene-Eocene Thermal Maximum (PETM, 56 million years ago) lasted for 200,000 years and caused the Earth to rise 5°-8°C over 10,000 years. (Note: we’ve risen [0.7°C over 100 years, which is about 10 times faster] than the natural warming cycles the planet has experienced.)

Lots of information in this graph. Here’s the breakdown. Time, in millions of years, is on the bottom (the x-axis) with present day on the right at 0 million years ago. The abbreviations above the time are for the names of the period (Pal = Paleocene, Eo = Eocene). Along the right, the y-axis shows the amount of a particular isotope of oxygen that tells us temperature. The green line in the graph is the amount of that isotope over time, and gives us a sense of temperature. The higher the line is the hotter the temperature, and the lower the line is, the cooler the temperature. Right between the Paleocene and the Eocene, you can see the spike that indicates a sudden hot temperature. You can also see the cooling trend that lead to the ice ages (“Rapid Glacial Cycles”).

This new study examined a time after the PETM (about 2 million years later, at 53.7 million years ago), called the Eocene Thermal Maximum 2 (ETM2). The record of this time is pretty complete in the Big Horn Basin of Wyoming. The authors analyzed the temperature before, during, and after the ETM2 using the isotopes contained in the soil and in the teeth of an early horse, Arenahippus pernix, and a couple of other mammal species. They also calculated the body size of these animals using the size of the first molar. Molar size corresponds well to overall body size in mammals, so we can use the molar size to estimate body size when we only have teeth.

Arenahippus pernix at the Swedish Museum of Natural History. From Wikipedia.

The authors found that as temperature increased, the size of the horse shrank (from 7.7 kg to 6.6 kg). As temperature fell again after the ETM2, body size increased (from 6.6 kg to 7.9 kg). One of the reasons for this shrinkage is that it’s easier to cool off a smaller body than it is to cool off a larger body. If the environment is warming up, then being able to cool off faster is an advantage. Also, there may have been fewer nutrients available if droughts were happening, so the horses may not have been able to grow to their full size. The last reason could be related to how much rain was available. Less rain means less plants and less food for herbivores. Whatever the reason or combination of reasons, what we do know is that climate change, like what we’re seeing now, will affect mammals in ways we are still discovering.

Figure 3 (A and C) from the paper. The first two columns show the carbon isotope levels in the soil through time. The further the points move to the left, the hotter the climate was. The right column shows molar size in Arenahippus. Points to the left are smaller molars and points to the right are larger molars. The molars get smaller just as temperature is the hottest, and then grow again when the climate cools down.

Video on atmospheric carbon dioxide from the Earth System Research Laboratory at the National Oceanic and Atmospheric Administration. More sources can be made available on request.

Diets and DNA

This week an [article] was published that examined the teeth of Homo neanderthalensis: the Neanderthal. Neanderthals and humans (Homo sapiens – us) both lived in Europe for approximately 5000 years. They evolved at different times and look different. Neanderthals were shorter and stockier, whereas humans are taller and lankier. Neanderthals evolved to deal with colder weather. They had brow ridges, smaller chins, larger noses, thicker bones, and wider chests. There are many ideas as to why they went extinct, which I won’t discuss here.

Neanderthal man versus a human man showing the differences in their body proportions. From dreamstime stock images.

This new study analyzed the dental plaque (the gunk on your teeth that the dentist cleans off) on 4 individual Neanderthals, 2 from Spain and 2 from Belgium. The authors analyzed the plaque for all sorts of DNA. Since Neanderthals probably didn’t brush their teeth, this dental plaque contained bits of DNA from everything they ate. By analyzing it, we can understand what they were eating.

A neanderthal skull. From Wikipedia.

What they found is that the individuals from Belgium ate sheep, rhinoceros, and mushrooms. The individuals from Spain ate mushrooms, pine nuts, forest moss, and poplar. This shows that Neanderthals took advantage of whatever food they came across and that their diet was different in each environment. One of the individuals from Spain may have also been treating a dental abscess (a tooth infection). How, you ask? This individual was the only one who had traces of poplar, a natural source of salicylic acid (a pain killer), and Penicillin (an antibiotic) from moldy plant material.

Neanderthal diets in each location. Sheep, rhinoceras, and grey shag mushrooms in Belgium. Pine nuts, split gill mushrooms, moss, and poplar in Spain. Maps from Google, images from Wikipedia, PFAF.org, mushroomobserver.org, Iowa State University, and NHMPL.

Lastly, the authors found one species of archaea (a group of microorganisms) that is present in both humans and Neanderthals. The interesting thing is that this species permanently split into two species (one for humans, one for Neanderthals) around 143-112 thousand years ago. Humans and Neanderthals split from each other around 750-450 thousand years ago, so this species of archaea was being transferred between humans and Neanderthals long after they evolved. This tells us that humans and Neanderthals were sharing food, maybe kissing, or interacting in some other way that led to the transfer of spit between species.

A neanderthal possibly thinking about dinner. From AFP/Getty images.

And if you haven’t checked out our [kickstarter] yet, what are you waiting for? It’s to fund the publication of an amazing children’s book called She Found Fossils, filled with stories of women paleontologists from history, present day, and up-and-coming students. It will be published in English and Spanish.

Mary Anning, drawn by Amy Gardiner.

4 Stories

This week was jam-packed with news, so instead of only talking about one story, I’m going to cover 4 of them.

First: A new catfish from the Upper Eocene (56-33 million years ago) of Egypt. This [paper] was published by lead author Sanaa El-Sayed, who is now the first woman from the middle east to lead an international vertebrate paleontology paper. She describes the oldest marine catfish from the Eocene, which she named Qarmountus hitanensis (“the catfish from Hitan”). The specimen includes much of the head and the shoulders. It comes from a site called Wadi El-Hitan, which translates to the Valley of the Whales. Because it is only one specimen, we will need to find more before really understanding how it is related to other catfishes.

Figure 2 from the paper showing the new catfish fossil.

Second: A new fossil penguin from New Zealand. This [paper] describes the foot of a new penguin from the mid-Paleocene (66-56 million years ago). The size of the foot is larger than that of Waimanu, an extinct penguin the size of the modern emperor penguin (4 feet tall). Because it’s from the mid-Paleocene, it’s one of the oldest penguins known. Its giant size tells us that penguins became giant early in their evolution and stayed that way for 30 million years.

Figure 1 from the paper showing the new penguin fossil.

Third: The debate about Tully Monster continues. Last year I wrote about [this study] that said that Tully Monster had a notochord, making it a vertebrate. [This study] came out at the same time showing that Tully Monster has eyes like a vertebrate. The authors found that Tully’s eyes had melanosomes (pigment forming cells) in 2 layers. These 2 layers form a Retinal Pigment Epithelium (a fancy name for the cell layers that give the retina, which senses vision, nutrients). These layers are only found in vertebrates, lending more evidence that Tully is a vertebrate. Now a new [paper] contradicts the first study, and argues that the structures the authors found in the first study are also found in groups that aren’t vertebrates. The latest study does not say anything about the eyes, though, so there is still evidence towards Tully Monster being a vertebrate.

Figure 1 from the paper showing the Tully Monster.

Fourth: I’m writing a book with two colleagues (Abby West and Amy Gardiner)! Last week I launched a kickstarter project, called [She Found Fossils] to fund the publication of this project. The book is for children and it details the history women in paleontology, present diversity, and up-and-coming students. The book will be available in English and Spanish, and potentially some other languages depending on how much money we raise. Check it out!

Original art from Amy Gardiner of Mary Anning.

The Fish that Lived

Marjorie Courtenay Latimer was born on February 24, 1907 in East London, South Africa. Her parent (I assume her father) was a station master for South Africa Railways. Marjorie always loved nature. When she was 11 she decided that she would be an expert on birds.

She started school at Holy Cross Convent, where her love for natural history grew. One of the sister’s there has a collection of fossil fish that fascinated Marjorie. When she finished school, there did not seem to be jobs in natural science, so she was going to become a nurse. Fortunately, the East London Museum was looking for a curator in 1931 and Marjorie took the job. She was 24 at the time.

Marjorie Courtenay Latimer. Photo from PBS.

When she started there, the museum’s collection only had a few birds, a pig, and some photos, so Marjorie quickly began collecting everything she could from places she visited. She even included her mother’s beadwork collection dating back to 1858 and her aunt’s dodo egg! She collected fossils from nearby field sites as well.

Her most important contribution came in 1938 when a call came in from the docks saying that a ship had come in with a strange fish. She rushed to the docks and picked off the slime. She revealed the most beautiful fish she had ever seen, “It was a pale mauvy blue, with faint flecks of whitish spots; it had an iridescent silver-blue-green sheen all over. It was covered in hard scales, and it had four limb-like fins and a strange puppy-dog tail.”

A coelacanth. Photo from National Geographic.

She sent a description and a sketch to a nearby ichthyologist (a fish expert), James Smith. He was stunned! This fish was a coelacanth – a fish that had been extinct for almost 70 million years. These fish were still alive! He excitedly wrote her back for more information. He named the fish Latimeria chalumnae after Marjorie and the location where the fish was caught. It took another 14 years before a second coelacanth was found, this time near Madagascar in 1952.

The sketch Marjorie sent to James. Image from PBS.

Marjorie retired from the museum and received an honorary doctorate from Rhodes University 1973. She lived the rest of her days loving natural history in all its forms.

And if you like posts like this one, stay tuned for an important announcement later in the week!

Live Birth in Aquatic Reptiles!

This week, a [study] was published that unveiled an amazing new fossil from the Middle Triassic (247-237 million years ago) of South China. This fossil is of a pregnant archosauromorph. An archosauromorph is a reptile that’s closely related to archosaurs (crocodiles, birds, their ancestor and all of its descendants). So it’s not quite an archosaur, but it’s not more closely related to any other reptile. This particular archosauromorph is a very long necked Dinocephalosaurus.

The Archosauromorpha family tree. Pictures from various online coloring books, Benton (1983) and Liu et al. (2017).

This fossil is the first archosauromorph to show pregnancy. How do we know it was pregnant? Great question, and one that the authors had to answer. We know the baby is the same species as the adult because of the shape of the bones and the crazy long neck found in this species. We know the adult didn’t just die on top of a baby and get fossilized like that because the baby is completely inside the body outline of the adult. We know that the adult didn’t eat the baby because aquatic animals usually eat fish head first (as seen by a partially digested fish in the gut of the adult), and the baby is oriented the other way. The authors also note that the baby is curled up in a typical way for developing babies. Lastly, we know that this adult wasn’t on her way to lay an egg containing the baby because usually eggs are laid with a much less developed baby in them. There’s no evidence of eggshell around the baby either.

Figure 3 from the paper showing the fossil on the left and the interpretation on the right. The baby is drawn in pink on the right.

We know that crocodiles and birds (archosaurs) lay hard eggs and there aren’t any crocs or birds that give live birth. We have fossils of other reptiles (like ichthyosaurs, plesiosaurs, and mosasaurs), along with several living snakes and lizards that give live birth. This fossil is the first example of a close relative of archosaurs that do this.

Figure 3c from the paper showing a reconstruction of the pregnant Dinocephalosaurus.

Mind the Teeth!

This week a [study] announced a reappraisal (when you examine something again) of an early mammal relative. This animal, a therocephalian, is more closely related to mammals than the dicynodont, Bulbsaurus, we talked about [last week].

A therocephalian, Moschorhinus. From Wikipedia.

This animal is called Euchambersia mirabilis. It was thought to have a groove in its canine tooth (the long, pointy tooth). This characteristic lead the original author to think that Euchambersia was venomous. Animals that have venom need to have three things: 1) a gland to produce and store the venom, 2) a transport system to get the venom to the teeth, and 3) a way to make an injury in another animal so that the venom can enter the animal’s body.

Figure 1A from the paper showing the CT scan of the skull of Euchambersia. Top is the right side of the skull. Bottom is the top of the skull. Nose is to the right in both images.

The author’s CT scanned the skull of Euchambersia and compared it to the skulls of three other early mammal relatives and two snakes. They found that Euchambersia has all of the features necessary for venom to be present. It has a depression in its upper jaw, called a maxillary fossa that could have contained the venom glad. There is a canal that links the fossa to the canine and ridged teeth to create wounds. So, even though the authors did not find the groove in the canine described by the original author, the other features in Euchambersia point to it being venomous.

A reconstruction of Euchambersia by A. Bernardini, showing the possible location of the venom gland in pink.

The Fossil Bulbasaur

This week, a [study] was published that named a new dicynodont. Let’s talk about it!

Dicynodonts eating plants. By V.O. Leshyk and the University of Utah.

Dicynodonts are extinct herbivores from the Permian Period (298-252 millions of years ago). They are named for the two tusks that most of them had: di – two, cyno – dog, dont – tooth. Dicynodonts are not dinosaurs, though. They are synapsids. Land animals (mammals, reptiles, turtles, birds, and their extinct relatives) are divided into three main groups based on the openings in their skulls. Every skull needs to have openings for eyes, the nose, ears, and mouth, but some additional openings around the temple can appear for muscles of the jaw. Anapsids, the turtles, have no temporal openings. Diapsids, the reptiles, have two temporal openings. Synapsids, the mammals, have one temporal opening.

An explanation of temporal openings. Anapsids across the top, with a turtle skull as an example. Synapsids in the middle row, with a dicynodont as an example. Diapsids along the bottom, with a crocodile as an example. Red circle is the nose, blue circle is the orbit (for the eye). Green and purple circles are the temporal openings.

Dicynodonts are early synapsids, so they are more closely related to mammals than to other animals, even though they look like reptiles. This new dicynodont is named Bulbasaurus phylloxyron: bulb – for the bulb on its nose, saurus – for lizard, phyllo – for leaf, and xyron – for razor (referring to the edge of the jaw that was sharp and used for cutting plants).

Figure 2 from the paper showing the new fossil skull in front view (A), the right side (B), and the left side (C).

Bulbasaurus had a small skull (13-16 cm long), but had adult features, meaning it was an adult even though it was small. It’s also the earliest dicynodont of its family, the Geikiids, which allows us to adjust the timing of the evolution of this group.

Artistic representation of Bulbasaurus by M. Celesky.

The Dinosaur Lady

Joan Wiffen was born in 1922 in New Zealand. Her father thought education was wasted on girls, so Joan didn’t get to go to high school. When she grew up, she joined the Women’s Auxiliary Airforce during World War II.

Joan got married in 1953. After a time, her husband signed up to take a geology class, but got sick and couldn’t go. Joan eagerly took his spot in the class, remembering her love of fossils as a child. She saw on a geologic map that a nearby valley had ‘old reptilian bones’ and went out fossil hunting near her house. In 1975, she found a fossil! She knew it was a vertebra, part of the backbone of an animal, but didn’t know from what animal.

A replica of the vertebra Joan found. Photo by Marianna Terezow/GNS Science.

In 1979 she went on vacation to Australia and visited the Queensland Museum. She met Ralph Monar, a paleontologist there and noticed a familiar looking bone on his desk. It was a vertebra exactly like the one she had found! He told her it was part of a dinosaur tail. She had found the first dinosaur fossil from New Zealand!

Joan Wiffen at the site where she found her first fossils. Photo by NZPA/John Cowpland.

Ralph and Joan worked together on many projects and published dozens of papers. Because of Joan’s hard work, she was known as the Dinosaur Lady. Even though Joan had not gone to school, she received an honorary doctorate from the Massey University of New Zealand in 1994. She also received a special award from the Queen.

Trilobite Eggs

Last week, a new [fossil] was unveiled. This one comes from the oceans of the Ordovician period (around 450 million years ago) and it’s a trilobite.

(Above: Trilobites from Dinopedia and Pinterest)

Trilobites are extinct arthropods (spiders, insects, millipedes, centipedes, crabs, lobsters, scorpions and more). They only lived during the Paleozoic Era (542-251 million years ago), but they had around 17,000 species (there’s only 5,400 species of mammals)! Trilobites came in a huge variety of shapes and sizes. Some of them were over 70 cm long and some were only 1 cm long.

The largest trilobites. From here.

The name “trilobite” comes from the three lobes that make up its body – the two side lobes (pleural lobes) and the central lobe. Note: they are not named for their cephalon (head), thorax, and pygidial (butt) lobes.

2 ways to divide a trilobite.

Since arthropods shed their exoskeletons to grow, we have many fossils of the same species, showing how an individual develops.

A growth series of a single species of trilobite. From here.

This new fossil shows something egg-straordinary. It has eggs preserved with it! The eggs are located under the cephalon of the trilobite. Even though trilobite eggs have been found before, they’ve never been found with an adult trilobite!

Figure 1a, d, and e from the paper showing the fossil and the eggs underneath the cephalon.

From this we understand that trilobites carried their eggs outside of their body, but tucked underneath their heads. Not on [kite strings] like other extinct arthropods.