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Ceratodus: The Iconic Lungfish of the Mesozoic Era

Ceratodus was a genus of prehistoric lungfish which existed on Earth for a surprisingly long time, from the late Triassic Period approximately 227 million years ago to the beginning of the Eocene Epoch of the Tertiary Period about 55 million years ago – a jaw-dropping span of 172 million years! That’s impressive by ANYBODY’S standards!

Lungfish as a whole are a primitive group of fish. They first appeared during the early Devonian Period about 416 million years ago (MYA), and it’s believed that they represent an evolutionary “missing link” between fish and amphibians. The closest relatives of the lungfish are the coelacanths, meaning “hollow spines”. That’s not surprising, considering that both lungfish and coelacanths have prehistoric origins as well as that both groups are classified as “lobe-finned fish”.

Lungfish do not have individual teeth like many fish today. Instead, they have four large bone plates (two in its upper jaw, and another two in its lower jaw) that were ridged in texture and crowned with thick triangular projections, and were used for crushing and cracking. Many species of modern lungfish feed on worms, freshwater snails, crustaceans, small fish, and amphibians.

Today, there are only six surviving species of lungfish, and all of them are found in hot tropical environments. With the exception of one species found in the Amazon Jungle and another species found in northern Australia, the remaining lungfish species are found in Africa.

  1. The South American Lungfish (Lepidosiren paradoxa), found in the Amazon River.
  2. The Marbled Lungfish (Protopterus aethiopicus), which is found throughout much of eastern and central Africa.
  3. The Gilled Lungfish (Protopterus amphibius), which is also found in eastern Africa.
  4. The West African Lungfish (Protopterus annectens), which is found, not surprisingly, in western Africa.
  5. The Spotted Lungfish (Protopterus dolloi), which inhabits the Congo Jungle of central Africa.
  6. The Australian Lungfish, also called the Queensland Lungfish (Neoceratodus forsteri), found in northeastern Australia. Of all of the extant lungfish species, this one is believed to be the most primitive.

Special attention must be given to the Australian Lungfish (Neoceratodus forsteri), for not only is this species regarded as the most archaic of all of the extant lungfish, but it was once believed to be the sole surviving member of the prehistoric lungfish genus Ceratodus alive in modern times.

Skeleton of Neoceratodus forsteri. From Günther, Albert. “Description of Ceratodus, a Genus of Ganoid Fishes, Recently Discovered in Rivers of Queensland, Australia”. Philosophical Transactions of the Royal Society of London, volume 161 (1871). Plate XXX. https://www.jstor.org/stable/pdf/109041.pdf.

The lower jaw of Neoceratodus forsteri, seen from above. From Krefft, Gerard. “Description of a gigantic amphibian allied to the genus Lepidosiren from the Wide-Bay district, Queensland”. Proceedings of the Zoological Society, volume 16 (April 28, 1870). Page 222. https://ia800405.us.archive.org/16/items/biostor-107043/biostor-107043.pdf.

The genus Ceratodus was established in 1837 by the famed Swiss ichthyologist Louis Agassiz based upon teeth which were found in European rock layers dated to the Triassic and Jurassic Periods. Most Ceratodus fossils that are found consist of isolated tooth plates, and different species have been named based largely upon difference in tooth morphology. Twenty-two species of Ceratodus have been named since the genus was first described in 1837. For a long time, Ceratodus was what is known as a “waste basket taxon” – all North American lungfish fossils were ascribed to this genus, regardless of how different they were from each other. Recently, a careful re-examination of lungfish fossils have revealed that these animals are remarkably different from each other and may constitute numerous genera, not just one. If that’s the case, then the overall lifespan of Ceratodus as a genus may be dramatically shorter than was previously supposed (Günther, Albert. “Description of Ceratodus, a Genus of Ganoid Fishes, Recently Discovered in Rivers of Queensland, Australia”. Philosophical Transactions of the Royal Society of London, volume 161 (1871). Page 512).

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Ceratodus, painted by Heinrich Harder. From Animals of the Prehistoric World (1916). Public domain image, Wikimedia Commons. https://commons.wikimedia.org/wiki/File:Ceratodus.jpg.

Ceratodus’ length varied depending on the species. Most sources which I have seen give an average length of 3 feet long. However, one species of Ceratodus may have reached truly gigantic proportions, possibly reaching 10 to 12 feet long. This estimate is based upon a single bone plate, which is the largest-known of any lungfish. The tooth plate was found in central Nebraska in rocks dated to the Miocene or Pliocene Epochs of the Tertiary Period. Shimada and Kirkland hypothesized that the tooth had been carried into central Nebraska by river from older rock layers that were located further to the west within Wyoming, in rocks dated to either the late Jurassic or early Cretaceous Periods. However, the tooth isn’t as banged up as you would expect from such a long journey. It’s possible that the tooth is endemic to central Nebraska, and if that is the case, 1) Ceratodus was alive in North America for a much longer geologic time span than previously supposed, or 2) This species is mis-identified and belongs to a new un-described genus of giant lungfish which lived in central North America about 5 million years ago, or 3) This was a species which happened to have unusually large teeth within its jaws, and the overall length of the animal was much smaller than the 4 meter estimate given by Shimada and Kirkland. Unfortunately, only one tooth plate has been discovered. Until more specimens are found, everything that we have to say about this specimen needs to be taken with a great degree of skepticism. (Kenshu Shimada and James I. Kirkland, “A Mysterious King-Sized Mesozoic Lungfish from North America”. Transactions of the Kansas Academy of Science, volume 114, issue 1 (2011). Pages 135-141. https://www.researchgate.net/publication/261964060_A_Mysterious_King-Sized_Mesozoic_Lungfish_from_North_America).

For the artwork accompanying this article, I decided to change up my style. For this drawing, I chose to evoke the whimsical style of the paleo-art of Patricia Bujard. If you don’t know who Patricia Bujard is, then I highly recommend that you check out her work. She is a children’s author and illustrator with a love for prehistoric life, and I find her artwork adorable. There aren’t too many people who can make an Allosaurus “cute”, but dag-nabbit, she somehow manages to pull it off. You can see her artwork on her WordPress page, Pete’s Paleo Petshop. My own drawing, which you can see below, was made with an ordinary Crayola black marker.

Ceratodus © Jason R. Abdale. February 9, 2021.

Keep your pencils sharp, and in this case, also keep your markers properly stored so they don’t dry out.

Promastodonsaurus

This is Promastodonsaurus, literally meaning “before Mastodonsaurus”. Despite its saurian name, it was not a dinosaur, or even a reptile. It was actually a large amphibian. Fossils of Promastodonsaurus were found in Argentina within the rocks of the Ischigualasto Formation, dated to the middle Triassic Period approximately 230 million years ago. The species was officially named in 1963 by the famed South American paleontologist José Bonaparté, in reference to another large amphibian named Mastodonsaurus which lived in Europe during a slightly later time.

Cladistically-speaking, this animal belonged to a large group of amphibians called the “labyrinthodonts”, so-named because a cross-section of their teeth looked like a maze. Within this broad group is a sub-division called the “temnospondyls”, “the cut vertebrae” because each of their backbones is divided into several parts. The temnospondyls were a diverse group of labyrinthodont amphibians which first appeared during the Carboniferous Period and lasted into the Cretaceous Period – a span of nearly 200 million years. Within the order Temnospondyli is the sub-order “Stereospondyli”, and within this is a division called the capitosaurians, “the head lizards”, so-named due to their freakishly huge heads. Promastodonsaurus was a member of this group. It was essentially a giant meat-eating salamander with the head of an alligator.

The only evidence that we have of this animal is a single partial skull. Based upon its similarity to the skulls of other temnospondyl amphibians within its family, it is believed that the animal’s head measured 45 centimeters long (Hans-Dieter Sues and Nicholas C. Fraser, Triassic Life on Land: The Great Transition. New York: Columbia University Press, 2010. Page 69). This in turn would make the entire animal somewhere in the vicinity of 6 feet long, as big as a medium-sized alligator.

Promastodonsaurus bellmani. © Jason R. Abdale. February 9, 2021.

During the middle Triassic Period, crocodilians did not exist, so the capitosaurians like Mastodonsaurus and Promastodonsaurus essentially filled in that ecological niche as crocodilian analogs. Large amphibians like these would continue to dominate freshwater environments until they were replaced by the phytosaurus, who in turn would be replaced by crocodilians.

 

Caturus

This is Caturus, a prehistoric fish which swam in the oceans during the Mesozoic Era. Fossils of this saltwater fish have been found in North America, Europe, northern Africa, and as far as China within rocks spanning from the beginning of the Triassic Period about 250 MYA up to the middle of the Cretaceous Period, about 100 MYA. However, most fossils have been found in Europe in rock layers dated to the middle and late Jurassic Period, about 170-150 MYA.

Despite a superficial resemblance to a salmon, Caturus was actually more closely related to a bowfin (Amia calva), which is a rather primitive ray-finned fish.

So far, paleontologists have identified fourteen species of Caturus. The largest species, Caturus furcatus, which lived in the shallow sea that covered much of Europe during the late Jurassic period about 150 MYA, reached three feet long; other species were much smaller. One species, Caturus dartoni, is known from North America in rocks dated to the middle Jurassic, about 165 MYA. Only two skeletons of this particular species have been found, the largest measuring 15 inches long.

Caturus. © Jason R. Abdale. September 5, 2020.

This drawing was made on printer paper with No.2 pencil, No.3 pencil, Crayola colored pencils, Prismacolor colored pencils, and Artist’s Loft colored pencils.

Some Quickie Drawings of Late Triassic Life

Hi everybody. As many of you already know, I occasionally volunteer at the Garvies Point Museum in Nassau County, New York. One day, I decided to hash out some drawings of Late Triassic creatures when I had a few moments of spare time, and I stuck them on the wall over the bulletin board. Recently, I went back to the museum for their annual Native American Feast, and to tell you the truth, I had completely forgotten about these pictures. I decided to take some photos of them while I was there. I’m hoping that the museum staff uses them for coloring activities with the children that visit the museum every week.

Dinosaur Day 2015 at the Garvies Point Museum

GP Museum 1

Well, it was that time of year again! Every April or so, at around the time of Easter, the Garvies Point Museum and Preserve, located in Glen Cove, Nassau County, New York, holds it annual “Dinosaur Day”. This is one of the days that I really look foward to for a few reasons. First, I get to work at a place that I absolutely love and meet with some good friends. Secondly, I get to be out of NYC for a little while, which is something that I ALWAYS look foward to. Third, I get to talk about a subject that has fascinated me since my earliest days – paleontology.

Veronica, the museum’s de facto head of administration, did a wonderful job along with other members of the museum staff of setting up the classroom where the day’s major activities would be taking place. Recently, the museum’s library was substantially increased. The Sands Point Museum and Preserve had closed down its library a short while ago, and all of the books and papers were sent to the GPM. I should state, though, that almost all of these documents were originally part of the GPM collections anyway, and they just got them back, that’s all. However, Louis (one of the workers at the Garvies Point Museum, but works primarily at the Old Bethpage Village – another place that I really love) has been working hard to re-catalogue all of these books and papers back into the museum’s database.

The name of the event was somewhat misleading, as it concerned all prehistoric life, not just dinosaurs. We had exhibits on primitive mammal-like-reptiles, dinosaurs, and prehistoric mammals.

Here are some pictures of what the room looked like both during and after the hoards of kids showed up.

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Most of the really young children gravitated immediately towards the dino toy area and the fossil digsite. The older children and a lot of the adults were interested in the information that I and others were giving. They were especially interested in Dimetrodon, the famous sail-backed pelycosaur from the early Permian Period. I don’t think that I have ever had to say the name”Dimetrodon” so many times within the course of a single day! It seemed to be the only thing that many of them wanted to talk about!

Some of the major topics of interest on this day were: the Permian Mass Extinction, which occured about 251 million years ago, when an estimate 95% of all life was wiped out; of course, T. rex was a favorite; as too was Allosaurus, who competed with its larger relative for attention from the crowds. This was helped in no small part to the fact that we had a lot of Allosaurus “stuff” arrayed for them: a picture of the skull, a hand model, bone casts, a model, and my drawing which you might recognize from an earlier post on this blog.

Finally, here’s a picture of me, “the Dinosaur Man” as several members of the museum staff call me, dressed up as an amateur paleontologist. In addition to my olive drab Garvies Point Museum shirt, I also wore a khaki utility vest, because apparently ALL paleontologists wear khaki utility vests! I thought that wearing it would help to enhance my ethos with the audience, and by my reckoning, it worked.

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Two Triassic Pycnodont Fishes: Brembodus and Eomesodon

Here are color pencil drawings of two genera of prehistoric fish. Their fossils have been found in central Europe in rocks dating to the late Triassic Period. Both of these fish belong to a group called the pycnodonts, and it seems that they fed primarily upon mollusks and small crustaceans. Pycnodonts first appeared during the late Triassic Period, and became completely extinct during the Eocene Epoch of the Tertiary Period.

Brembodus

The first one is called Brembodus ridens. Among its features was a short spike on its back formed by extensions of the skull bones. This might have been meant to deter predators, like a modern-day triggerfish.

Eomesodon

The second fish is called Eomesodon liassicus. It looked remarkably similar to a modern-day tang or surgeonfish, except I’m not sure if the typical surgeonfish caudal blade (a sharp pointed piece of bone, located on both sides of the base of the tail, which could be extended if needed) has been found in association with specimens of this particular genus. As to the color, it’s pure guesswork on my part.

Hope you enjoy, and I look foward to any feedback.