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.

An Exceptional Fossil Insect

Cockroaches are known for surviving multiple extinction events on Earth. They evolved around the Carboniferous Period (360-300 million years ago) and modern versions appear in the fossil record in the middle of the Mesozoic Era.

A Madagascar hissing cockroach. From National Geographic Kids.

Now imagine if a cockroach evolved long, grasping arms, and giant eyes for hunting prey. That’s pretty terrifying, right? Well, that’s basically what a praying mantis is*.

A praying mantis. If you think about it, a praying mantis is really the insect form of a carnivorous giraffe. A carnivorous giraffe with knife hands. Photo from Wikipedia.

Today, praying mantises hunt prey by ambushing animals as they come close. Mantises are normally camouflaged to blend in with their surroundings. When a particularly tasty insect comes by, they attack! They have a single pair of arms they use for catching and holding prey (called raptorial arms). Each arm has a set of spikes that help hold the prey in place. But did they always use one pair of arms for this job?

Figure 1 from the article showing the fossil in the center. On the left, the different body parts are colored (eyes are dark blue, head is yellow, body and arms are the other colors). On the right is a close up of the second set of arms.

A new 110 million-ear-old [fossil] from Brazil shows us a different idea. This exceptionally preserved mantis shows a pair of wings, the head, part of the first body segment, and the first two pairs of arms.

The interesting thing is that both the first and the second pairs of arms have spikes on them. Since these spikes are used to catch and hold prey in modern mantises, we know that this fossil mantis was probably using its second pair of arms to help hold prey. This fossil shows us that extinct mantises may have hunted a little differently than what we see today.

A couple of praying mantis showing their colors. Photo by I. Siwanowicz.

*To be clear, mantises did not evolve from cockroaches. Both mantises and cockroaches evolved from an ancestor that looked more like a cockroach.

The Statue-Like Ankylosaur

Back in May, I told you about an [ankylosaur] that was found by an oil company in 2011. It took 6 years of careful preparation to remove the hard rock around the fossil, but it is finally complete. This week, its [official announcement] was published in the form of a scientific paper.

Figure 1 from the paper showing the amazing fossil.

This ankylosaur is a nodosaur, an armored dinosaur without a club tail. It is from Alberta, Canada, from 110 million years ago. The authors named it Borealopelta markmitchelli, meaning “Mark Mitchel’s Northern Shield” after the person who spent hours uncovering it from its rock, and after its armor and the location where it was found. It seems that when the animal died, it got washed out to sea, sank, and was quickly buried. It’s preserved in three dimensions, and its armor is beautiful.

In life, horns and armor are covered by a keratin sheath. Keratin is a hard substance that makes up our fingernails and hair, but also what gives rhinos their horns, covers the horns of other animals, and makes up the baleen that whales use to filter-feed.

A rhino skull without the keratin on the left (from Bone Clones) and a rhino skull with the keratin on the right (from Wikipedia). The keratin makes up most of the horn.

Keratin normally breaks down very quickly after the animal dies, so it’s not usually preserved. In the case of this nodosaur, much of the keratin is preserved, giving us a complete view of the armor it had.

Figure 2a from the paper showing the fossil in a top view. The dark grey is showing all the keratin, the yellow is showing the bone underneath.

Additionally, the authors found a unique chemical signature in the keratin. These chemicals are not melanosomes (the cells that make color), but are the products of the breakdown of melanosomes. By examining these chemicals, the authors were able to figure out what colors were present on different parts of the body.

A reconstruction of Borealopelta by the Royal Tyrrell Museum.

They found that the back of Borealopelta was a redish-brown color, and that the belly was a lighter color. This combination – a darker back and lighter belly – is called countershading, and it’s used by animals who are trying to hide themselves from predators. Today, you can see a similar color pattern in an antelope.

A pronghorn antelope showing counter shading. From Wikipedia.

Some mammals, like rhinos and elephants, are so big that they don’t have to hide from predators. Their size keeps them safe. Even though Borealopelta was very large (1300 kg), the fact that it has countershading means that theropod predators were still a threat.

There are some who think that the chemicals the authors found may be from the sediment or from bacteria. As always, science continues searching for answers! Even so, Borealopelta makes a welcome addition to the ankylosaur family tree.

Little Morning Bird

This week, a [paper] describing a new fossil bird was published. Lots of cool things going on with this fossil.

The fossil was found on Navajo lands in New Mexico. It is from the Early Paleocene (around 62 million years ago), only a few million years after the end-Cretaceous extinction. The fossil preserves parts of the arms and legs, a couple of vertebrae, and a tiny bit of the skull.

Figure 2 from the paper showing the different parts of the fossil.

Its feet are particularly interesting. This little bird had the ability to turn one of its toes backward whenever it wanted to. Most birds have 1 toe that’s permanently backwards for grasping branches. Some birds, like parrots and woodpeckers, have two toes like this. This new bird could decide when it wanted a second toe pointed backwards.

Different bird feet. The parrot and woodpecker have two toes turned backward. Most birds only have one toe turned backward. From here.

By comparing it to other birds in a phylogenetic analysis, the authors discovered that it’s the oldest mousebird ever found. Today, there are only 6 species of mousebirds and they all live in Africa.

A modern mousebird. From here.

The fossil is a new species of mousebird. The authors named it Tsidiiyazhi abini, meaning “little bird” and “morning” in Navajo. The cool thing is, because this fossil is so old, it pushes back the origin of several bird lineages into the Paleocene. This means that most of the modern bird groups were already present only 4 million years after the extinction! Birds evolved very quickly after the extinction event (a process called an explosive radiation). Flowering plants (the plants that produce fruits and nuts) were also explosively radiating at this time and probably provided homes and food for all of these bird groups.

An illustration of what Tsidiiyazhi abini might have looked like. By S. Murtha.

A New Whale with Crazy Teeth

This week, a [paper] came out that described a new fossil whale from South Carolina (USA). The fossil is from the Oligocene (~ 30 million years ago) and it has a basically complete skull, some vertebrae, and a few ribs.

A reconstruction of Coronodon by A. Gennari.

The authors named the fossil Coronodon havensteini, meaning ‘crown tooth.’ It was found by Mark Havenstein, so the specific epithet (the second part of the name) is in his honor. The teeth of this fossil are particularly interesting.

Figure 2 from the paper showing the teeth of Coronodon.

Instead of simple, conical teeth (like in dolphins), or baleen (like in the blue whale), Coronodon has teeth with many bumps, giving each tooth the appearance of a little crown. Food and other particles left little scrape marks on the teeth, which indicate the direction of water flow through the mouth, and how the teeth were used during feeding. When the mouth was closed, the upper teeth sat on the outside of the lower teeth, providing just enough space for water to escape through the teeth, leaving delicious food bits inside the mouth.

Figure 2f from the paper showing how water would have flowed between the teeth.

Coronodon was using its crazy teeth to filter feed! Why is this important? Because understanding how filter feeding began in whales is an ongoing question. Coronodon is one of the earliest relatives of the mysticetes (baleen whales), but it has no baleen itself. It used its teeth the same way mysticetes use their baleen. Later on in mysticete evolution, baleen began to develop and finally took over as the dominant feeding structure. Coronodon represents the first step in that process. Another idea is that whales went through a toothless, suction-feeding phase before filter-feeding with baleen came about, but Coronodon shows that suction-feeding wasn’t part of the evolution of filter-feeding.

We can learn a lot about how extinct animals ate their food through looking at the shape and tiny scrape marks on the teeth (called microwear), and Coronodon is new amazing example of that!

A Fluffy Double-Feature

This week, two articles were published that discussed feathers in two different dinosaurs. We’ll start with the cooler one…. uhhhh… I mean…. the…. one with better preservation. Yes, that’s it!

The first [article] described a bird fossil in amber, the third one from Myanmar that has been recently described. It is of an enantiornithine, an extinct lineage of toothed birds from the Cretaceous, and it’s spectacular. Most of the animal is preserved because it’s trapped in amber and many of the feathers are preserved in detail.

Figure 6c from the paper showing the 99 million year old enantiornithine foot in amber. Behold its beauty! Scale bar is 5 millimeters.

The authors wrote a thorough report of each part of the specimen, along with descriptions of the feathers found on each portion of the body. By CT scanning and examining it under dissecting microscopes, the authors were able to see both bone and feather morphologies. The morphologies indicated that the specimen was a juvenile. The feathers show that enantiornithines were precocial at hatching. Precocial means that they were able to walk around, and potentially even fly, from the day they hatched (like a chicken or a brush-turkey). Baby birds that need a lot of care before they can manage by themselves are altricial. This new specimen, along with other enantiornithines, are pointing to most enantiornithines being precocial. They are also known to be mostly arboreal (tree-dwellers). The combination of precocial and arboreal is not something that modern birds are doing: the precocial birds of today are ground-dwellers and the altricial birds of today are tree-dwellers. This means that enantiornithines were superficially similar to modern birds, but living different sorts of lifestyles than what we see today and this could have impacted the places they could live in and the body-shapes they had.

The graphical abstract from the paper showing the amber chunk with the fossil (bottom), the CT scan (middle), and a line drawing interpretation (top).

The second [article] was about tyrannosaurids. This group contains Tyrannosaurus rex, Gorgosaurus, Tarbosaurus, and a few other large-bodied theropods that are known for their large heads and tiny arms. There has been an ongoing debate on whether or not they had feathers covering their bodies. This debate originated because we know feathers were present on a lot of other theropods, including on the most basal members of the group, like Dilong. The issue is that we’ve never found a larger bodied tyrannosaur with feathers preserved on it.

An illustration of Dilong by P. Sloan.

To address this question, the authors examined fossilized skin impressions of several specimens of this group. They found that scales covered parts of the neck, abdomen, hips, and tail and concluded that most of these large-bodied tyrannosaurids were covered in scales. If feathers were present, they would have been limited to the back of the animal. There are many hypotheses (testable scientific ideas) out there about why these big tyrannosaurids lost their feathers, but I’m not going to address those here.

Figure 1b from the article showing a piece of fossilized skin from T.rex. You can see the outline of each scale.

The main point I want to make about this paper, and I’m going to quote my undergraduate mentor (Dr. Tom Holtz) here, the absence of evidence is not evidence of absence. That means just because we haven’t found feathers preserved on big tyrannosaurids, does not mean they didn’t have them. The conditions needed for feather preservation are very specific, and the places where we find these big tyrannosaurids are not the same types of places that preserve feathers. So maybe T. rex had feathers and they just weren’t preserved. Maybe T.rex didn’t have any feathers. Maybe it had feathers as a baby and lost them as an adult. Maybe it had feathers in some places on its body. For now, we don’t really know. We might never know. And that’s ok because science is a process of continuous discovery and interpretation. We’ll just have to keep digging.

Oceans, Whales, and Time

I don’t always talk about whales on this blog, but when I do, I prefer to talk about their size or echolocation. This time it’s about size. We all know many whales are really, really big. What we hadn’t quite understood yet is when they got big, or why.

A photo of several baleen whales surfacing as they engulf tiny krill. Source unknown.

Thankfully, a new [article] ran an analysis to figure out these two missing pieces. The authors used a dataset of 13 living and 63 extinct whales, including DNA (for the living ones) to create an evolutionary tree with time estimates for each branching point (called branch lengths). Using this tree and a dataset of body sizes, the authors used a model-testing approach to assess how the timing of whale evolution took place.

What’s a model testing approach? A model-testing approach is when we use computers to test the fit of different models to the data we give it. In this case, the authors gave the computer the tree and the body size data. The authors picked several different models for the computer to test. One of the models was based on random events driving evolution. One of them was based on evolution with a trend towards one trait. Some of the models were combinations of the others, where the model changes at a certain point during evolution. Once the computer is done testing each model, it produces a few statistical values that tell us how well each model fit the data.

A representation of the authors hard at work.

For this study, the authors wanted to know which model of evolution best fit the evolution of giant sizes in whales. The computer’s analysis showed that body size evolved randomly until around 3 million years ago when there was a shift to evolution with a trend of becoming very large. Even though filter feeding using baleen had been present in whales since 25 million years ago, it wasn’t until recently that they became very large. Around 3 million years ago, during the Plio-Pleistocene, wind-driven upwelling (where wind patterns on the surface bring up nutrients from the ocean floor) started getting stronger. This concentration of small food items is probably what lead to whales getting gigantic.

How upwelling works. Higher winds on the surface push the warmer surface water away from the coast. Colder, nutrient-filled water from the bottom gets pulled up. From NOAA.