The Giant Extinct Otter and its Giant Bite

Last week, an [article] was published that talked about the biting ability of the extinct giant otter, Siamogale melilutra. The [discovery] of this otter in south-western China was published in January of this year. It lived during the Miocene (23-5.3 million years ago). Siamogale weighed about 50 kg (110 pounds) and is the largest otter to have been found.

A reconstruction of Siamogale by M. Antón.

Living otters have a range of sizes from 4 kg (9 pounds) to 45 kg (100 pounds). They live all over the world in fresh and marine waters. And they’re really cute.

Otters holding hands. From Wikipedia.

This new paper compared the jaw mechanics of all of the living otters. Jaw mechanics include things like how much force the jaw can handle, muscle volumes, jaw stiffness, and how efficient the jaw is when biting. The authors used the jaw mechanics information from the living species to calculate the mechanics of Siamogale. Then the authors made CT scans of all of the skulls and tested the mechanics using computer software.

Figure 4 from the paper showing the computer models for the Giant River Otter and Siamogale. Red areas have higher stress, blue areas have less stress.

They found that Siamogale had a jaw 6 times stiffer than any of the living otters! This means that Siamogale had a super powerful bite. It probably used this powerful bite to eat foods like clams that have to be cracked open to enjoy. Some of the living otters use tools to help them crack the shells. Other living otters use their powerful bite. Siamogale’s super powerful bite probably let them eat foods that other animals at the time couldn’t eat.

The Dinosaur Tree Debate Continues

This week, a [reply] to the new [dinosaur tree] from March was published. You might recall that the March paper found a new set of relationships for dinosaurs. Ornithischians and theropods were found as closest relatives, forming the group Ornithoscelida, and sauropods and a group of early dinosaurs formed another group.

Evolutionary tree of dinosaurs published in March. Made by me.

The reply paper itself is only 1 page long. The authors looked at all of the characters used in the March analysis and rewrote them based on their own examination of the fossils. They also added a few more dinosaurs that were in important places in the tree.

Evolutionary tree of dinosaurs given by this new analysis. Made by me.

The authors ran their updated characters in a new evolutionary relationship analysis. The analysis gave them the standard evolutionary tree for dinosaurs. Theropods and sauropods are closest relatives, forming the saurischians, and ornithiscians are their own group.

You might think – ok, problem solved! But in fact, the authors ran a statistical analysis on their tree to see how many changes would need to be made to find the March tree. This analysis shows that only a few would have to be made to get from their tree to the March tree. This means that the trees are not very different, statistically speaking.

Another possibility. Made by me.

The authors also found that another tree is almost equally possible – one where sauropods and ornithischians are closest relatives and the theropods are their own group! WOW! What we know for sure is that early dinosaurs from each group looked very alike and so working out how they are all related to each other is going to take more research.

A New Look for Sinosauropteryx

Last week, a [paper] came out discussing the color patterns on the theropod dinosaur Sinosauropteryx. This dinosaur was a small-bodied meat eating dinosaur from the Cretaceous (133-120 million years ago) of China.

Figure 1 from the paper showing one of the specimens of Sinosauropteryx.

The authors took photos of 2 specimens of Sinosauropteryx under special lighting conditions. This helped them see the feathers that surround the skeletons. Feathers that had color in them are preserved more easily than feathers without color. So looking at the fossils helps us understand how colors were distributed on the animal. Artists then made reconstructions to show how the colors appeared on the dinosaur. They found that Sinosauropteryx had a striped tail, a bandit mask around its eyes, and a brown back with a white belly.

Figure 2A from the paper showing the color reconstruction on Sinosauropteryx.

The authors also wanted to test what the colors could tell us about what kind of habitat Sinosauropteryx lived in. Animals that live in open habitats (like deserts or grasslands) usually have darker colors on their back and lighter colors on their bellies. This helps break up their body shape so that predators have a harder time seeing them. Animals that live in closed habitats (like forests) usually are darker everywhere and have fewer areas with lighter colors. Think of the color differences between an antelope that lives in the grasslands, and an okapi that lives in the rainforest.

An antelope on the left showing coloration for open habitats. An okapi on the right showing coloration for closed habitats. Okapi from here.

To do this, the authors 3D printed models of the dinosaur and photographed it twice: once when it was fully sunny and once when it was completely cloudy. The full sun imitates the open habitat and the cloudy day imitates the closed habitat. They found that the shadows cast on the model on the sunny day match the color distribution found on the fossils. This means that Sinosauropteryx lived in open habitats.

Figure 2B from the paper showing how the open habitat where Sinosauropteryx lived and its coloration.

It probably used its bandit mask to reduce the sunlight entering its eyes. The striped tail, dark color on its back and light color on its belly helped camouflage it in open habitats, making it harder for predators to see it, and making it harder for prey to see it coming. This study shows us how new techniques can help us answer questions about how dinosaurs lived.

A Group of Reptiles Gets a New Head

This week, a [paper] came out describing a new fossil skull. The skull belongs to a reptile group called Drepanosaurs (dre-PAN-o-saurs). This group is well-known as we have several fossils of the bodies. Heads, however, have been harder to find.

A few different drepanosaurs. From here.

These reptiles evolved during the Permian (sometime around 260 million years ago), but did not become a diverse group until the Late Triassic (around 219 million years ago). That means they survived the biggest extinction event this planet has experienced – the Permo-Triassic Extinction Event. This occurred at 250 million years ago and around 90% of all life went extinct.

An approximation of what Earth looked like during the Permo-Triassic Extinction. (Just kidding – it’s Mordor).

The drepanosaurs lived on, though! These little reptiles looked very much like chameleons, but had some unique traits. The new fossil is called Avicranium renestoi (“avi” for bird, “cranium” for head, and “renesto” in honor of a paleontologist who works on this group).

Figure 2 from the paper showing the reconstruction of the skull bones. The long dotted line is the missing portion of the snout. The nose is to the left.

As its name suggests, the skull shows a mix of shapes, some looking very bird-like, and some looking very reptile-like. Let’s start with the bird-like features. The skull has is edentulous (has no teeth). Also, the part of the skull slightly back from the eyes is very domed. This leads to a bird-like braincase and [endocast]. These shapes are very similar to what we find in pterosaurs, modern birds, and some maniraptorans. Some of the features, like the back of the braincase and the ear, are very similar to other early reptiles. So Avicranium has a mix of bird-like and reptile-like features making up its skull.

An analysis of evolutionary relationships puts this group at the very base of the reptile tree. This shows us that some of these ‘bird traits’ evolved way earlier and in unrelated groups. It also shows us that the diversity in body shapes was much higher in the Triassic than we previously thought.

Baby Food for Ichthyosaurs

Last week, an [article] was published describing an old specimen that was hidden away in a museum collection at the University of Birmingham, United Kingdom. This specimen was of a baby ichthyosaur, only 70 cm long.

Some different ichthyosaurs. From here.

Ichthyosaurs were marine reptiles that lived during the Mesozoic Era. They had torpedo-shaped bodies, similar to modern dolphins and great white sharks. They came in all sorts of sizes and shapes!

Figure 1 from the paper showing the ichthyosaur fossil.

The authors know the specimen is a baby because some of its bones are still being developed and because of the proportions of the eyes and different bones in the skull. It was not found near an adult, so it wasn’t an embryo. This is the smallest specimen of Ichthyosaurus communis ever found!

Figure 9b from the article showing the hooklets in the stomach (by the black arrows). The long grey bones are ribs.

The interesting thing, though, is what they found in the stomach. Inside the ribs, the authors found several cephalopod hooklets. Remember, cephalopods are animals like octopus, squid, and nautilis. These hooklets are found on the underside of their tentacles, exactly where you’d find the suckers on an octopus arm.

A comparison of suckers and hooks on two different cephalopods. From here and here.

This indicates that the baby ichthyosaur was eating squid as its preferred food! Other species of ichthyosaur ate mostly fish as babies and transitioned to eating cephalopods as adults. This baby specimen shows that Ichthyosaurus communis ate cephalopods as babies, giving us a more thorough view of the diets of ichthyosaurs through their lifetimes.

Crab-Eating Hadrosaurs

Last week, a [paper] was published that described some fossil poops. That’s right, poops! When a poop fossilizes, it’s called a coprolite (‘copro’ for poop and ‘lite’ for stone).

A coprolite. From Wikipedia.

These coprolites came from Grand Staircase-Escalante National Monument in Utah and they date back to around 76-74 million years ago. The coprolites contain decayed wood bits that had been chewed up before swallowing. Of the dinosaurs known from this area and time, it is most likely that hadrosaurs were responsible for creating the poops. Hadrosaurs have specialized teeth that are really good at crushing and breaking tough vegetation to make it easier to digest. Instead of having a single row of teeth, hadrosaurs unite dozens of teeth into a thick collection of teeth (called a dental battery). All of the teeth work together to create a large, flat surface for grinding.

A dental battery with one tooth outlined in white. At the top of the battery, there is a flat surface for grinding. Photo by V. Williams.

The hadrosaur coprolites had more than just plants and decayed wood, though. They also contained bits of crab shell! And it wasn’t only 1 coprolite that had crab shell in it. Several different coprolites from different areas and different times had crab shell in them. This means that it wasn’t an accidental swallowing of a crab, but rather, that the hadrosaurs were eating them on purpose.

Figure 2b from the article showing the coprolite.

How can we be so sure though? We know how wide a hadrosaur mouth was and we know how big the crabs were. It turns out, the crabs would have taken up a large portion (20-60%) of the hadrosaur’s mouth! If the dinosaur didn’t want to eat the crab, it would have noticed it and spit it out. The authors think that during times where plant matter was harder to find, these dinosaurs would eat the decaying logs that crabs also ate. As the dinosaurs munched away on the wood, they’d eat the crabs as well, providing a good source of protein.

My own reconstruction of a hadrosaur, Maiasaura finding a crab. Drawing found on Pinterest. Log photo by C. Perrin. Crab photo by The Daily Dot.

This study shows us that even though we think teeth are specialized for one type of food, animals might eat a larger variety of items that we thought.

Cretaceous Hell Ants

At the beginning of September, a [paper] was published that described a new species of ant. Not just any ant! A hell ant from the Cretaceous. That was preserved in amber from Burma.

A photo of the hell ant in amber. The authors called the new species Linguamyrmex vladi.

This group of ants is extinct and known only from the Cretaceous (specifically around 98 million years ago). The amber is see-through, so the authors took high-resolution images of the ant through the amber. They also CT scanned it.

Figure 3 from the paper showing a reconstruction of the ant.

They found that this ant had a large horn coming off the head and a scythe-like jaw. A scythe is a curved metal tool for cutting tall grasses. It’s also what Death carries around.

Death, holding its scythe. From here.

These jaws were used to pin and pierce soft larvae, but could not be used to chew their prey. Instead, the authors think that after piercing the prey, the jaws would funnel blood down into the bend of the jaw, and then small hairs and suction would direct the blood into the ant’s mouth. This ant sucked blood like a vampire!

Figure 4 from the paper showing the hell ant and its prey.

Lastly, the CT analysis showed that the jaws are denser than the rest of the head. This analysis also showed that the increased density was due to metals in the jaw. These ants absorbed metals from their environment and used them to make their jaws stronger. It’s too bad that this group is extinct – it would have made for a killer nature show!

A Plesiosaur with a Sieve-Mouth

A couple of weeks ago, in late August, a [paper] was published that re-examined a fossil that has been known for 30 years. This fossil is a partial skull of a plesiosaur. Plesiosaurs were aquatic reptiles that lived in the oceans during the Mesozoic. They all had large, paddle-like limbs to help swim in the water. Some of them had big heads and short necks and some had small heads and a long neck.

Some of the different plesiosaurs. This image is made with children’s toy models, but it shows how some plesiosaurs have big heads and some had small heads. From here.

The fossil plesiosaur from this paper is called Morturneria seymourensis and it’s from Seymour Island, Antarctica. Even though we’ve had this fossil for a long time, paleontologists couldn’t figure out how the bones fit together. A discovery of a different plesiosaur fossil helped put the pieces of Morturneria together.

Figure 2 from the paper showing the parts of the skull on the left, the interpretation in the middle, and the reconstruction on the right. All of the images are in side view, with the tip of the nose pointing upward.

Now that the authors knew what the skull looked like, they made some interesting observations. The jaw is wide and can open very far. The teeth are loosely held in place and they come out to the sides of the jaw, instead of up and down.

Figure 10 from the paper showing an artist reconstruction of Morturneria.

They think that these characteristics show that Morturneria was using its mouth like a sieve. It would take in a large amount of water or sediment around its food and push out the water and sediment through its teeth. This would move the water out of its mouth, but keep the food in. Modern baleen whales do the same thing, except they use baleen instead of teeth. Mortuneria is the first marine reptile to have filter-fed!

Bird Discoveries in Argentina

I’m going to let me very obvious biases (prejudice for or against something – in this case, for something) come forward this week.

An Argentinian newspaper, El Clarin, announced the [discovery] of three large birds in Mar del Plata, Argentina. I am Argentine, and I like birds, so of course I’m choosing to talk about this even though there isn’t yet a scientific paper to go with it.

A map of Mar del Plata, Argentina. From Google.

Paleontologists working in a canyon between Mar del Plata and Miramar found the bones of three different birds. One is a terror bird, one is a condor, and one is an eagle. They are all from 5.5-3 million years ago, part of the Pliocene epoch.

The terror bird is a juvenile of Mesembriornis milneedwardsi. This species is one of the phorusrhacids – a group of giant terrestrial predatory birds. This particular species was 1.8 meters tall.

The phorusrhacids. A is the modern cariama, which is not a phorusrhacid, but is their closest living relative. B is Mesembriornis. From here.

They identified the condor partially from a femur, which is 33 centimeters long! Lastly, the eagle. It’s thought to be bigger than the modern crowned eagle. The crowned eagle is around 3 feet long and has a wingspan of 6 feet!

A crowned eagle with a person (Simon Thomsett) for scale. From here.

The canyon where these fossils were found is continuously eroded by waves. The more the waves hit the rocks, the more fossils come out. Paleontologists there say that they never go home empty handed, so they’ll have to keep their eyes peeled for more specimens.

An Old Dinosaur with New Information

Earlier this month, a study was [published] with a surprising result about the early history of dinosaurs. As we have previously discussed, dinosaurs come in 2 general flavors: Ornithischians and Saurischians [or maybe not]. Ornithischians include the diverse herbivores like Stegosaurus, Triceratops, Pachycephalosaurus, and others. They all have a predentary bone (a bone in the front of the upper jaw) and a pubis that points backwards (part of the hip). The predentary bone supported a beak for chopping plants and the backwards pointing pubis allowed for more space for guts – both necessary features for eating a lot of plants. Saurischians include the long-necked sauropods, and meat-eating theropods, like Tyrannosaurus rex, Velociraptor, Coelophysis, and others. They have a pubis that points forward and no predentary bone.

A comparison of saurischian (top) and ornithischian (bottom) hips. The pubis is in green. From Britannica and Everything Dinosaur.

The early history of dinosaurs is a bit unclear partly because many of the earliest dinosaurs look very similar. This study examined a dinosaur named Chilesaurus diegosuarezi, which had been previously identified as a theropod. It has a backwards pointing pubis, but no predentary bone. This is not a combination that is seen in any other dinosaur.

Figure 2 B and D from the paper showing the dentary (left) and hips (right) of Chilesaurus.

The authors put Chilesaurus into a data set with 75 other dinosaurs and over 450 characters. The computer then ran a phylogenetic analysis (an analysis of evolutionary relationships) using the data set. Their new analysis concluded that this dinosaur was actually an early ornithischian and not a theropod! It shows us that the traits that helped ornithischians eat more plants evolved in stages and not all at once. First, the pubis turned backwards to allow for more gut space. Later on, the predentary bone formed and created a beak to easily chop plants.

This analysis shows that sometimes we need to go back and retest our results to get a clearer picture of the past.