Friday, August 17, 2012


Ctenoimbricata (ten-oh-im-bri-kah-tuh) was an early echinoderm that looked a lot like a trilobite. It lived in the Cambrian, and the only two known specimens were found in Spain. It was described by researchers at the Natural History Museum of London and the University of Birmingham in 2012.

Ctenoimbricata was teardrop shaped, with many flat, triangular feeding appendages in the front. Like modern marine detritivores, it may have used its feeding appendages to put sand into its mouth, sort out the food from the sand, and spit out the excess sand. I think it probably would have eaten a small marine worm if it happened to catch one, like today's deep sea sea cucumbers do. 

Ctenoimbricata crawling on the sea floor

Ctenoimbricata was only 20 millimeters long, so it needed to have defenses. These were in the form of spines all over its body, similar to modern sea urchins. It was also probably slow, like modern echinoderms, and used tube feet to move around. It had hundreds, or maybe even thousands, of these tube feet, which are tiny, clear, gooey sticks, often with a suction cup-like device on the bottom used for moving around. 


Ctenoimbricata is a very important discovery because it is the oldest fossil that is definitely an echinoderm. The fossil was scanned and reconstructed, and the scientists found out it was bilaterally symmetrical, unlike other echinoderms, which have radial symmetry. This adds to the evidence that echinoderms and chordates may be related. 

Fossil of Ctenoimbricata

Thanks to Dr. Alien for first telling me about Ctenoimbricata!


Wednesday, July 18, 2012

Opabinia (Part 2)

Opabinia was a Cambrian invertebrate probably related to today's velvet worms. It was also related to Anomalocaris, which probably sometimes ate Opabinia. 

Opabinia's main food source was presumably worms, which were pulled out of their burrows by Opabinia's long proboscis, then torn up and eaten in its "pineapple ring"-shaped mouth located in a scoop on the underside of the creature's head. Another presumed food source of Opabinia was carcasses, especially of large animals such as Anomalocaris and Hurdia

One striking feature about Opabinia is that it possessed five huge eyes. Because of where Opabinia's eyes are positioned, it might have had 360 degree vision. It is thought that the eyes probably only detected motion. 

Opabinia swam by undulating the lobes on its sides. Each side possessed eleven lobes. For a burst of speed, Opabinia would have flicked its fins very quickly, similar to how a modern fish does a burst of speed. But Opabinia had a different fin arrangement than a modern fish. 

Opabinia was two to three inches long and probably swam along the bottom of the ocean. 

Opabinia searching for food.

Opabinia's closest relative was the Australian Myoscolex. Unlike Opabinia, it had no tail fan, and the eyes closest to the back had long stalks that curved backwards. So Myoscolex basically had eyes on the back of its head. And it needed to have eyes on the back of its head, because Anomalocaris, a top predator, was also present in Australia in the Cambrian, and it would have eaten Myoscolex. 

Opabinia was found on the other side of the world from Myoscolex, in British Columbia. 

Opabinia (top) compared with Myoscolex (below)

Opabinia also has modern relatives called Onychophora, or velvet worms. They live on land, mostly in Australia, and inhabit wet forests. They normally live in families inside logs in the day, but at night they come out to find food. There are usually up to fifteen velvet worms in a family. Velvet worms usually grow up to about 1-1/2 inches. 

Opabinia is actually quite similar to velvet worms if you look at it the right way. Because Opabinia is now thought to have had legs, if you take away all the fins and the proboscis, leave only two tiny eyes and add antennae, you get a velvet worm. 

Another modern relative to Opabinia is the tardigrade, which looks like a very short, stubby, microscopic velvet worm. One striking feature about the tardigrade is that it is nearly impossible to naturally kill, although it is probably very easy to intentionally kill by smushing it. It can be frozen, heated, and even put into space. Scientists put tardigrades into space without a spacesuit or a jar of air...and they survived!!!

A modern velvet worm on a forest floor. 


Thursday, June 14, 2012


Sacabambaspis is an Ordovician arandaspid, a kind of primitive armored jawless fish, that has been found in Bolivia in the Andes Mountains. It was about one foot long. Like all fish of its time, Sacabambaspis had no jaws, so its mouth was always open. It had no jaws and it didn't have any teeth either. If it did have teeth, it wouldn't have been able to use them, because it didn't have jaws. All Sacabambaspis ate must have been algae, plankton, and tiny pieces of carcass left behind by large predators such as Cameroceras, Endoceras, and Megalograptus

The only fin Sacabambaspis had on its body was the caudal fin, or tail fin. Its relative Astraspis didn't even have that. Scientists used to think that Sacabambaspis had a shark-like tail, but now they know that it had a tail similar to modern jawless fish, a sort of eel-like tail. 

The most striking feature about Sacabambaspis was the shell that covered its head. The armor that covered placoderm heads was more like a suit of armor. But Sacabambaspis had armor that was more like a clamshell. Placoderms had different plates of armor all over their head, which allowed different parts of their heads to move. Ostracoderms, armored agnathans, or jawless fish, had shell-like armor, which was usually two plates, one of the top of the head and one on the bottom. The shell on Drepanaspis, from the Devonian, gradually got smaller as Drepanaspis evolved, to form individual plates on the head, more like a placoderm, except it still had no jaws. 

Sacabambaspis had both of its eyes facing forward, which meant that it had 3D vision. Most other jawless fish did not have this feature. 

Sacabambaspis on a reef with a trilobite, an orthocone, a crinoid,
and rugose corals encrusted with bryozoans.

Sacabambaspis lived on reefs that were home to creatures such as trilobites, crinoids, orthocones, rugose coral, eurypterids, and bryozoans. At the time, any fish on a Bolivian reef almost had to be Sacabambaspis. There are no other known fish from the same place and time, in Bolivia 460 million years ago, when Sacabambaspis was found. 


Sacabambaspis, accompanied by rugose corals and bryozoan-encrusted rocks,
viewed from above.

The arandaspid family includes Astraspis, Arandaspis, and Sacabambaspis. They were all from the Ordovician. Astraspis was from North America, Arandaspis was from Australia, and Sacabambaspis was from South America. 


The arandaspid family: (from top) Astraspis, Arandaspis, Sacabambaspis

Arandaspis was more flattened on the sides than other arandaspids, and it was probably unstable and tilty. It had a rigid shell and was about four or five inches long. 

Astraspis was also about four or five inches long. It had no fins, not even a caudal fin, and a very bumpy shell. I hypothesize that with no caudal fin, it probably mostly slithered across the bottom, and from time to time it could have squirmed around and swam up into midwater to feed on plankton. It could then drift down again to feed on algae and scraps of leftover carcass, which is what it mostly ate. Astraspis is the oldest known North American vertebrate. 


The tail of the Ordovician fish Sacabambaspis

Super Little Giant Book of Prehistoric Creatures

Tuesday, May 29, 2012


Dinocaridida is the group which contains anomalacarids such as Opabinia and Anomalocaris. There has been much debate over what kind of animal members of Dinocaridida actually were. They possess jumbled-up features of two groups of modern animals, the arthropods and the onychophorans. They lived on every continent except Antarctica. Only one species has been found in Africa so far, an unnamed Ordovician anomalocarid very similar to Peytoia (formerly Laggania). Very few have been found in Europe. Most are found in North America and Greenland, with notable specimens from Asia too. 


From top to bottom: Jianshanopodia, Kerygmachela, Pambdelurion. Arrows represent method of capture.

The first Dinocaridids, from the early Cambrian, looked more like onychophorans than arthropods. Some had no eyes, like Kerygmachela and Pambdelurion. Kerygmachela had a tiny mouth, which would have meant it needed to chop up its prey before it ate it. It did that by means of its knife-like claws, which shredded prey. The inward-pointing hooks on the spines would have prevented escape. Although it sounds ferocious, Kerygmachela was only about the size of a human hand. Its relative Pambdelurion, which was the same size as Kerygmachela, was a peaceful filter feeder which captured millions of tiny plankton with its hairy claws, which it then "licked" off with its tiny mouth. On the other hand, Jianshanopodia had a unique method of capture. With a motion of its claws and the opening of the mouth, it sucked small creatures into its stomach. Jianshanopodia was also about the size of a human hand. 

From top to bottom: Anomalmocaris, Opabinia, Petoyia

Typical anomalocarids from the middle Cambrian Burgess Shale were much more complex, looking like a cross between arthropods and onychophorans. Among these, Opabinia was unique. It had a long proboscis with a claw at the end. The mouth was not on the proboscis, but was actually under the head, as in all Dinocaridids. The proboscis was long and flexible, which helped it reach down worm burrows to grab hapless worms, which it ate. Opabinia was also a scavenger of dead arthropods and other animals, which it was very fit for, because of the flexibility of its proboscis, which enabled it to reach into cracks in the armor of a carcass and rip out chunks of internal organs and flesh from beneath the exoskeleton. It also had five huge eyes, which is not unusual in modern arthropods. Many insects have five eyes, except three of those eyes are tiny. In Opabinia they were all large. 

Anomalocaris was a top predator. It could grow to three, possibly even six feet long. It shattered exoskeletons of trilobites and other arthropods with its two seven-inch claws. Like all Dinocaridids (except Jianshanopodia), Anomalocaris had eleven lateral lobes, which it used for swimming. It would have been very stable, and also able to swim backwards. It could hover motionless in mid-water for a long time watching for prey. When it saw something promising, Anomalocaris would lunge forward with its claws flared out, and then grab the food item. It would then rip it to pieces and eat it. 

Peytoia was a filter feeder. I hypothesize that it rammed predators with its huge head, partially because the eyes and claws were set far back, which could have meant the head was doing something that its eyes and appendages should not be involved in, such as head-butting predators. I also think it could have been a mating display, where the males head-butted each other for the right to mate with the females. This could have been possible because only a few specimens showing the head have been found, and it's possible that all of them were males. I'm not really sure what that huge head was for, I just realize that Peytoia had a bigger head than any other Dinocaridid (except for Hurdia, which had strange headgear that made it look like an arrow). Peytoia also had no tail fin, and when wandering around it probably moved very slowly, although it could have been quite capable of bursts of speed. 

From top to bottom: unnamed Ordovician anomalocarid from Morocco, Schinderhannes bartelsi, Caryosyntrips

Recently, Ordovician fossils of a Peytoia-like anomalocarid have been found in Morocco. My drawing of this unnamed animal above is based on the pictures of the fossils that I saw. 

Schinderhannes bartelsi is the most recent anomalocarid (in geological time). It had two huge flaps right behind its head which propelled it through the water. It had a stingless spine at the rear and no lateral lobes along its sides. The only fossil was found in Germany. It was only about four inches long and it preyed on animals such as small shrimp and worms. 

Caryosyntrips is a new discovery from the Burgess Shale of the middle Cambrian. The feature that stands out about Caryosyntrips is its claws. Instead of grabbing down, as in Anomalocaris, they pinched together like crab claws. They have been compared to nutcrackers. 


Arthropod origins:$FILE/str.%20323-334.pdf

A giant Ordovician anomalocarid:

Monday, May 14, 2012

I've been doing my blog for one whole year!

My very first post was on May 15, 2011, when my mom took pictures of my Lego jawless fish and asked me if I wanted to start a blog. And I did! I've been doing this for a whole year. To celebrate the anniversary, I picked five of my favorite creatures that I've written about in the last year, and here they are:

1. Anomalocaris (here and here). Anomalocaris was a giant Cambrian predator related to today's velvet worms. It crushed hard-shelled animals with its two seven-inch claws and its "pineapple ring" mouth. It had eleven lobes along the side of its body which helped it hover and swim in mid-water. It also had no legs. It was at least three feet long, but it was almost definitely no more than six feet. Most of the complete fossils are of juveniles. Coprolites containing bits of trilobites have been found in Australia. I hypothesized that Anomalocaris may have given live birth just like today's velvet worms. 


2. Opabinia. A four-inch-long Cambrian predator, including its proboscis (three inches long without this appendage). Opabinia used its proboscis to poke around in worm holes and rip chunks of flesh off of carcass. Strangely, Opabinia had five mushroom-like eyes on top of its head, each one as large as the other. It was related to Anomalocaris and velvet worms, and I think it could have given live birth too. Opabinia also had eleven lobes along its sides and, like Anomalocaris, no legs. 


3. Scyphocrinites. Scyphocrinites was a strange Silurian-to-Devonian crinoid that floated upside down at the surface of the water by means of a balloon-like organ called a lobolith in place of the gripping root-like organs that most crinoids possess. Unlike most crinoids, Scyphocrinites could not purposely move (bottom-dwelling crinoids can un-anchor themselves and drag their bodies across the sea floor with their arms to find a better attachment place). Scyphocritinies could only move with the current. Fortunately, this meant that it was always in the same place as its microscopic food, plankton, which was also being swept around by the current. Scyphocritinies was large, but I can't say how large, because I've never found a source that talks about its size other than that its large. The calyx (body) has never been found attached to the lobolith, but we know the calyx and the loboliths found belong to the same species. The same exact stem has been found attached to the lobolith, and that kind of stem has also been found attached to the calyx.  All the pieces of Scyphocrinites were found in Morocco.


4. Helicoprion (here and here). Helicoprion was a bizarre shark from the Carboniferous to the Triassic. The only fossils that have ever been found of it are its mysterious "buzz saw" lower jaws, which helped it slice prey such as fish and squid. It is unlikely that Helicoprion ate hard-shelled animals such as ammonites, because if it ate mostly ammonites there would be a lot of broken teeth found in the tooth whorls. Broken teeth are nearly absent in the tooth whorls. And sharks tend to eat a lot. The biggest tooth whorls that have ever been found are about two feet across, which meant that Helicoprion would have been 30 to 50 feet long. A very long shark, which would have meant it needed a lot of food and would have had a monstrous appetite. It must have been a top predator. Helicoprion was related to other eugeneodontids such as Edestus and Ornithoprion. It is not known where exactly in the lower jaw the tooth whorl went, but the most modern idea is that it was embedded in cartilage to make a circular extension of teeth on the lower jaw. This idea also includes that the lower jaw was as long as the upper jaw, and that they were both quite long. Most reconstructions of Helicoprion show that it had little or no teeth in the upper jaw. 


5. Siphusauctum. Siphusauctum is a weird, newly-discovered Cambrian stalked animal. It looked reminiscent of a ctenophore on a stalk and was a filter feeder that fed on plankton. The body was roughly four inches tall. There is a very small amount of information on this animal because it is so newly discovered. It was found many years ago in the Burgess Shale, but was discovered in the collection at the Royal Ontario Museum in 2012. It was described by Jean-Bernard Caron and Lorna J. O'Brien. 


Monday, April 30, 2012

Fossil Fish Found Alive: Discovering the Coelacanth.

I read the book Fossil Fish Found Alive: Discovering the Coelacanth by Sally M. Walker, and it was very informative about Coelacanths. It didn't take long to read and it was great.

The book talks about how the earliest modern day Coelacanth to be found was caught in 1938 off the Camoros Islands, which are a French colony off the coast of Africa. This Coelacanth was named Latimeria chalumnae, after the person who discovered it, who had the last name Latimer. 

Latimer had no idea what the fish in her net was, so she took it to several places and asked what it was. They all said that they did not know. The last place she took it to said it looked like a Coelacanth, which at the time was thought to be extinct. The Coelacanth was believed to have gone extinct 65 million years ago, and at the time, the last Coelacanth fossils were 70 million years ago. No Cenozoic fossils of Coelacanths have ever been found, so to date the prehistory of Coelacanths stops in the Cretaceous. 

Prehistoric Coelacanths, from top to bottom: Allenypterus, Hoplophegis, Mawsonia, Axelrodicthys, and Miguashaia

Somebody named Smith came to see the Coelacanth and proved its identity. Smith wanted to find another Coelacanth. He caught an unusual fish in his net in the Camoros Islands. He thought it was a new species and named it Malania anjouanae. But then he realized his mistake. It was a Coelacanth. The dorsal fins and epicaudal fins were missing from this fish, so he thought it was a new species. The fins were probably just bitten off by another fish when the Coelacanth was young, or another such accident. It was not a different species. 

The modern day Coelacanth Latimeria

A new species of Coelacanth was described around 1998 and it was named Latimeria menadoensis. It was found in Indonesia, which is in Asia. That's unusual because so far Coelacanths had only been found in Africa and Madagascar, never in Asia. 

Scientists were desperate to find a live Coelacanth in its natural habitat. They started diving down in submersibles to habitats of Coelacanths. On October 29, 2000, they were finally successful and found live Coelacanths in South Africa. At first they found one, but then, on the next dive, they found many. They noticed that when the submersible got close, the Coelacanths did bizarre headstands. It was later found out that these were probably because the Coelacanths use the earth's electrical field to navigate, and in the disturbance of the electrical field they automatically did the headstands because of disorientation. 

It was found out that in the daytime Coelacanths rest in caves and only come out at night. When scientists started tagging Coelacanths, they found that they drifted around in the current, and when prey such as small fish got near, the Coelacanths sucked them in. This is another adaptation that conserves energy. 

Latimeria resting in a cave in the daytime

The largest Latimeria chalumnae ever found was 6-1/2 feet long. This population of Coelacanths was also the shallowest-living ever found, with depths of 344 feet. They were filmed by divers, but diving at that depth can be dangerous. Coelacanths usually live at about 700 feet down, so normally they would never be filmed by scuba divers. 

Coelacanths are one of the two groups of lobe-finned fish, or sarcopterygians, alive today. The other group are the famous lungfishes, which have the ability to breath air and can live under dried-up lakes for years. Unlike lungfish, Coelacanths, or at least modern day Coelacanths, live in salt water. There were a few prehistoric Coelacanths, like Undina from the Jurassic, that spent their lives in fresh water. The largest Coelacanth ever was Mawsonia gigas, from the Cretaceous from Egypt and Niger. Mawsonia was also found in South America, but this makes sense if you know that Africa and South America were joined together in the Cretaceous (which also explains the distribution of lungfishes in South America and Africa).

I learned that Coelacanths are full of oil, which helps them maintain balance just above the sea floor without having to actually move. The oil also makes the Coelacanth very disgusting to eat, which is why fisherman don't usually fish for Coelacanths as food. The reason why Coelacanths are fished is normally for maintaining specimens. 

Friday, April 20, 2012


Gonioceras was a benthic actinocerid orthocone of the Ordovician. Its distribution included the eastern half of North America, including Canada and the North Pole area next to Greenland. This would not have meant that it was a polar animal, it just means that the continents have shifted a lot, and that the climate has also changed quite a bit. In the Ordovician, the whole world was tropical, even the poles.

Gonioceras had a convex top of the shell and the bottom was flat. This was ideal for living on the sea floor, because that meant Gonioceras would not sink into the muck. This is the same principle as the spines of many trilobite, which helped the trilobites keep themselves from sinking into soft mud. Trace fossils show that tubular-shelled nautiloids did sometimes rest on the bottom, but they did not live their whole life there as Gonioceras did. Tubular-shelled nautiloids such as Cameroceras also probably sometimes dragged across the bottom to catch trilobites and other benthic prey.

Gonioceras chasing a trilobite

Gonioceras was a unique nautiloid because it was flat. Unlike other nautiloids, it had a triangular form. The name Gonioceras, meaning "angle horn," well suits this animal, because few other nautiloids, except for other actinocerids, were flat and triangular like this.

Gonioceras grew up to about one foot long. I hypothesize that it probably had little or no need for a complex balancing system because it almost always stayed touching the bottom, and it probably never ventured into midwater. For a creature this shape, hatched on the bottom of the ocean, it would take quite a long time for it to get its flat shape into the water. The shell could be compared to a one-foot-long flat rock, and it would have been very hard for such a small animal to lift such a heavy object up into the water. The shell would have been heavy in the first place, and considering the weights Gonioceras would have needed to keep the gas in its shell from slowing making it float up to the surface, it would have been very heavy. So it would have been hard for Gonioceras to lift itself up more than a few inches off the sea floor.

Top and side view of Goniceras

Gonioceras was actually smaller than its shell, because only a small part of the shell houses the live animal, which would have been a couple of inches long. Its bottom-dwelling habits must have meant that it preyed on bottom-dwelling animals like trilobites or worms. Rays and flounders may have a similar place in the food chain today as Gonioceras did in the Ordovician.

The only living relatives of Gonioceras are of the genera nautilus or allonautilus. Actinocerids like Gonioceras only lived in the Ordovician, but other orthocones lived to the Triassic, and orthocone-like ammonites such as Baculites lived in the Cretaceous.

Gonioceras was probably preyed on by eurypterids and larger nautiloids. Like all cephalopods, they had many tentacles surrounding a beak-like mouth, a syphon propelling them through the water, and a mantle behind their head. Nautiloids and aminoids are the only shelled cephalopods, besides the modern genus argonauta, a shelled octopus. Members of this genus can leave their shells at any time, and only the females have shells. The shells of Gonioceras were probably more delicate than those of other orthocones, because they were flatter and thinner. The whole shell is very rarely preserved in a fossil.

Gonioceras could probably partially bury itself in sand with backward shovel-like motions of its shell being propelled by the syphon,and its tentacles throwing sand on top of its body, similar to living rays and flounders, who do this with their fins. Some living cephalopods sometimes bury themselves by throwing sand on top of their body with their tentacles.

Gonioceras resting on the sea floor

Although nautiloids like Gonioceras and the modern nautilus do not have suckers on their tentacles, they have a very strong grip. Modern nautiloids can hardly ever be pulled off of their prey without ripping off their tentacles because the grip is so strong. Nautiloids also have more tentacles than other cephalopods.

Because of its flat shape, Gonioceras probably would have been very hydrodynamic on the sea floor, jetting itself quickly just above the bottom. Since the ventral side of its shell was flat, it would have been much easier for Gonioceras to rest on a flat surface such as sand or mud than on rocks, which meant it probably lived closer to sandy shores. Orthocones could not have lived in the deep sea because their shells would have cracked due to the pressure. Coiled nautiloids could have easily gone into deep water because their tightly-packed shells would have offered more protection.


Thursday, April 5, 2012


Lepidodendron was a giant lycopod tree that flourished in Carboniferous wetlands. It was up to 130 feet tall. 

For half of its life Lepidodendron lived as a telephone pole-like plant sticking out of the forest floor. Then it began branching. Finally, the branching growth stopped and spore cones formed at the end of the branches. Growth stopped. The tree was putting all its energy into making and releasing spores. 

In some species of Lepidodendron the tree died after it was finished releasing its spores, probably because they spent all their energy on doing just that, shedding and making spores. This is like salmon who die right after laying eggs because they use up all their energy swimming up rivers and jumping up waterfalls, and spend the last bit of energy laying eggs and transferring sperm to the female. 


Lepidodendron and other lycopod trees had the shallowest roots I've ever heard of. The roots barely went a couple feet into the ground for an enormous 100 foot tree. One of the reasons 
Lepidodendron didn't fall down was probably that, despite its enormous size, the trunk was probably pretty light. Inside the thick bark there was a cotton-like substance, which was the vascular system. Another reason Lepidodendron didn't fall down is probably that the roots were fat and also surprisingly long. But they barely went into the ground and were nearly unbranched. The bark of Lepidodendron was a couple of inches thick, which held the tree in an upright position. 


Lepidodendron had bark covered in scaly leaf scars. In the "telephone pole" stage, the leaves were gradually moving up the trunk. As the tree got larger, and older leaves fell off. Finally this process stopped as Lepidodendron started to grow its first branches. The first branches it grew were forked, and then off of those forks it grew branches that looked somewhat like those of conifers. 

Some people used to think that the bark was the remains of a giant snake or lizard, which turned out to be totally wrong. 



Prehistoric Life: The Definitive Visual History of Life on Earth, pg. 145

Friday, March 23, 2012

Cameroceras (Part 2).

I've written about Cameroceras before, but there is more about this relative of the modern nautilus that I would like to explain. 

Cameroceras is a species of Ordovician nautiloid that had a straight shell right behind its head. It belongs to a group of nautiloids called orthocones, along with Orthoceras, Endoceras, and Gonioceras. 


Although the widely accepted size estimate of Cameroceras's length is 20 feet, there is some debate. Paleontologists often find partial shells of Cameroceras, very rarely the whole thing. When they do find a complete specimen of the shell, it is usually of a small individual. Unless we have the living chamber or the tip of the shell in the specimen, we cannot accurately determine the length of the animal. Based on partial specimens of large individuals, we can only know that it could have grown very big, but not the exact length. In the future we may find a way to determine which part of the shell the fossil belonged to. 

In the image below, I drew Cameroceras hunting near the seabed. This individual has successfully caught the eurypterid Megalograptus. Another Megalograptus is swimming away, and Isotelus is crawling on the sea floor directly below the Megalograptus. On the left side, near the head of Cameroceras, there are two rugose corals and one crinoid. 


Like the modern nautilus, Cameroceras probably had an extremely strong grip with its tentacles. Once something was caught, it would be very hard for the prey to escape. The tentacles were probably stronger than those of the nautilus, because Cameroceras was much bigger (the modern nautilus only has a shell diameter of 8 inches). 

Cameroceras had an amazing way of keeping its head from facing towards the bottom of the ocean and the tip of its shell from facing towards the surface. Cameroceras had a long siphuncle, a kind of tube, running down from its siphon. The siphuncle had traffic cone-shaped blocks of calcium in it, which counter-weighted the body and kept it horizontal. Like all nautiloids, it had upward-facing rings called septa. They were filled with gas and kept Cameroceras afloat. It was a very efficient strategy of locomotion. 


The siphon, which was connected to the siphuncle, sucked in water and then shot it out again to propel Cameroceras in the opposite direction of whatever way the extremely flexible siphon was pointing. Modern cephalopods can swim backwards and forwards and also steer very well, because of the flexibility of their siphon. Cameroceras probably had a very flexible siphon too, and this extreme maneuverability would have made it an efficient hunter. 


A Sea Without Fish by David L. Meyer and Richard Arnold Davis, pg. 132-134.

Thanks to Paul Mayer at the Field Museum for discussing how paleontologists find out the size of orthocones when they don't have the complete shell. 

Tuesday, March 6, 2012

New research on Pikaia from Simon Conway Morris and Jean-Bernard Caron.

In Pikaia gracilens Walcott, a stem-group chordate from the Middle Cambrian of British Columbia, published online March 4, 2012, Simon Conway Morris and Jean-Bernard Caron confirmed that Pikaia was a chordate after all. They looked at the anatomy of 114 specimens of Pikaia (I thought there were only 16 known Pikaias!)and found myomeres, v-shaped blocks of skeletal tissue that are only found in chordates. The scientists also found evidence of a vascular system, and found that at least part of the alimentary canal was preserved in almost every specimen. 

Externally, Pikaia was mostly just a flattened, tie-shaped body tapering from a tiny head. It had tentacles on its head, two antennae, and a thin dorsal fin. 

What was first thought to be the notochord in Pikaia is now interpreted as a "dorsal organ," which was possibly hollow. This doesn't mean there's no notochord. Under this dorsal organ there is a thread of tissue that is now interpreted as the notochord and nerve chord. 

I've only read the abstract, but when I read the actual article I'll learn more information. 

Friday, March 2, 2012

Chicago After The Field Museum (Part 4 of 4): Shedd Aquarium.

I went to Shedd Aquarium and it was so cool. They had an exhibit on jellyfish, which I was excited about. They had really weird jellyfish. 

They had a really big tank full of moon jellies and it was packed. There were jellyfish in a huge swarm and each had a bell that was about one foot across. I could even see the orange food that they had eaten because they were so transparent. It was all up inside their stomach, which is in the center of the jellyfish.

The moon jellies were so cool that we took a video of them:

Jellyfish have been around since the Cambrian Period, and I have a couple of fossilized jellyfish from the Carboniferous Mazon Creek.

These are sea nettle jellyfish. Their pulses looked very strong, and that probably helps them drawn water into their bell with plankton, and then push out all the plankton onto their tentacles, where it is then stung and killed, and then fed to the mouth.

These are upside-down jellyfish, a very bizarre kind of jellyfish that spends almost its whole life stuck upside-down to the bottom of the ocean (hence the name upside-down jellyfish). Although this is for a reason. They have algae living inside their bodies which gives them food. In turn, the jellyfish stick upside-down to the bottom and face the light, which helps the algae grow. They have a symbiotic relationship with the algae.

These are called hairy jellyfish, which is obvious when you look at their tentacles, which are very thin and hair-like. They also were very slow, and there was a lot of time between each pulse. They look a lot like some deep sea jellyfish, and they also look like box jellyfish a little bit. 

This is a video of Pacific sea nettle jellyfish, a larger species of sea nettle than the ones in the photograph  I previously mentioned. It's a really cool video. The jellyfish seem even stronger than the other sea nettles, and they are certainly formidable predators of copepods and other plankton. 

This photograph is of two arapaimas, a type of fish from the Amazon River that grows to ten feet long, and is also a living fossil that has its origins in the Cretaceous. The related arowana is also a living fossil. They had those at Shedd Aquarium, but I didn't get a picture. They were about one or two feet long.

This is a picture of me posing next to a freshwater stingray from the Amazon River. It is stuck to the glass, and its mouth and gills are clearly visible. I thought the freshwater stingrays were really amazing.

This was a huge life-sized model of an arapaima, which shows just how big they can get. The scales were huge.

This is an image of a huge school of cardinal tetras, a fish from the Amazon River which is commonly found at pet stores, probably because of how beautiful the shimmering swarms of them can be. I could see them from a long way away. They were so bright. It's almost like they were glowing.

This image shows a moray eel, a beautiful marine eel that grows to ten feet long.

We also saw some electric eels, a type of knifefish that can grow to eight feet long, which makes it the largest knifefish species. They are also deadly because they can shock up to 650 volts.

They had a giant spider crab, the biggest species of crab in the world. In the wild they are often found in the deep sea where they have an opportunistic lifestyle, picking up and eating any scrap of edible debris they can find.

The next day it was time to leave Chicago, and I really didn't want to go. It was so sad to leave.

We went to the airport and the Kronosaurus had to go through the X-ray two times for some reason.

I couldn't stop reading my new book.

Art had a ton of new experiences and a fantastic time in Chicago. A million thanks to: Paul Mayer, Jane Hanna, University of Chicago Secular Student Alliance, Stephen & Kayla & Greta, Casey, Mike, Dave Monroe, PZ Myers, and the 72 incredible people who pitched in to help fund our trip to the Field Museum.