Tag Archives: dinosaurs

Why dinosaurs are not extinct

In the twenty plus years I have been involved in paleontology I have been witness to a revolution within science. The revolution has been quiet, not noticed by most of the public. Like any good revolution, the battles of this revolution took place between two camps, the “traditionalists” and the “radicals” who were out to change things. And this shift is illustrative of how science as a whole moves from one way of understanding to a brand new way of looking at the world. It is, in fact, a paradigm shift that has profoundly changed biology and paleontology forever.

At issue is how we explore and classify the relationships of all living things. The traditional view, the one that I was taught as a young student, was the classification of living things into the taxonomy originally begun by Carl Linnaeus. This system started with a group, and then sought to put things into the group. For example, one can make the observation that animals that look like “dogs” could be grouped together, so you would start with the idea of a dog-group and look for animals that should be included.

You might put foxes, wolves, domestic dogs into the group, and call it the dog family. You might also note that “cats” could likewise be grouped, and do the same thing, creating a cat family. In this view, the families were equal in rank—and there could be no overlap. An animal would be included in only one of the equal-ranked families. Any animal was included in only one class, for example Amphibia, Reptilia, Aves, or Mammalia.

The equal-ranked heirarchy of classifications worked well enough when we mainly were concerned with modern animals. Clearly, birds look different than mammals and reptiles, so it seemed evident they belonged in their own class. But this classification scheme, however well it served us as a place to start, is myopic about how evolution actually operates—how organisms actually evolve. This is understandable since it was started 100 years before evolution as a theory was established.

In trying to shoehorn life into the system, we repeatedly ran into problems as we expanded our knowledge of the diversity of living things and our understanding that the history of life is a complex branching bush. We knew that early tetrapods (organisms with four limbs) gave rise to the early amphibians that crawled out on land, and that they in turn evolved into reptiles, mammals and birds. But despite this branching within tetrapods, the class ranks were forced to be exclusive, so somewhere in evolutionary history was an “amphibian” that had to become a “reptile,” and a “reptile” that had to become a “bird.”

The many transitional forms in the fossil record increasing became impossible to classify. These intermediate animals had to be forced into one class or another. Increasingly, it became evident that many times the criteria used to put an organism into one class were the whims of an individual scientist, and another equally qualified expert with different opinions might place the same animal in a different class with equal validity.

The origin of birds was for a long time a great mystery to paleontologists. Birds are a pretty unique and specialized group, and while we knew that they originated from reptiles somehow, exactly how and when was unclear. One early paleontologist noted that dinosaurs had many features in common with birds, but the early concepts of what dinosaurs were like distracted most scientists from comparing them too closely. After all, the common conception of dinosaurs was as big, lumbering, dim-witted, swamp-dwelling beasts. The bird ancestor must have been light, fast moving, and energetic.

However, dinosaur research over the last thirty years has completely changed our view of them. Evidence from many lines, including things like footprints and the cellular structure of the bones, all point to dinosaurs as being very dynamic creatures. With this new view, the notion that birds were linked to dinosaurs became clear too. Now, we have dinosaur fossils with feathers, and birds with teeth and dinosaur tails to attest to their close relationships. In fact, birds are most closely related to the meat-eating raptor-like dinosaurs of Jurassic Park fame.

To go along with the revolution in our view of dinosaurs was that revolution in science that I mentioned above–the emergence of a new way to understand the interrelationships of life on Earth. This new model accommodated the myriad branching events that life actually experienced in order to produce the great variety of living things. So, instead of starting with a conception of the group and looking for members, this new concept looked at the branching patterns evident in life, and then sought to apply names.

Below is an illustration of the branching pattern of selected tetrapods, those vertebrates with four well developed limbs. As the first tetrapods gave rise to new and different groups, the branches split off. An early tetrapod gave rise to amphibians and the other animals above it on the chart (mammals, turtles, etc.). A later tetrapod developed traits related to the production of eggs and young that we recognize as the Amniota. Some of those early amniotes went off on an evolutionary trajectory that we can recognize as being the early mammals, and all the diversity that resulted from them. And so it goes up along the branches.

Branching pattern of the tetrapods, mostly the land vertebrates

Branching pattern of the tetrapods, mostly the land vertebrates

We now explore the branches and can apply names to the groups that we find to be meaningful. For example, in the illustration below we can call everything in the box a reptile. Note that it includes things that used to be called reptiles, turtles, lizards, snakes, crocodiles, and dinosaurs, but now also includes birds.

Group that includes all the reptiles

Group that includes all the reptiles

Likewise, if we draw a line around the dinosaurs, they also include the birds. This view of life tells a more complete evolutionary history and retains the branches, letting the animals “fall where they will.” We do not pull birds out of their relationships and give them special consideration. Instead of birds being equal in rank with reptiles, they are included among them. This upsets the tradition that being a bird is somehow equally important to being a reptile, but better reflects the reality of descent, without forcing nature into earlier human conventions of naming and grouping. Of course, birds are a group within their own right, and we could zoom in to explore their branching pattern, but it does not change the group to which they belong.

Group of dinosaurs

Group of dinosaurs

This leads to another startling statement. Below I have highlighted the groups that are extant (still around today).

Groups of tetrapods that are alive today (extant)

Groups of tetrapods that are alive today (extant)

Because of our grouping scheme, birds are included in the dinosaur group, so dinosaurs are not really extinct! They live among us today flitting about, singing their mating songs in the trees. It is funny how things can change in science. Twenty years ago scientists would have told you the dinosaurs were all extinct, and today we say the opposite. I love scientific progress–it can be so startling.

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How big was the Giant Short-faced Bear?

The character of living things on land changed forever after the Cretaceous-Tertiary extinctions, 65 million years ago. The dinosaurs on land and the marine reptiles in the oceans went extinct, leaving way for mammals and birds to evolve into those niches once held by the “terrible lizards” (dinosaurs) and other giant reptiles.

Throughout the Cenozoic, sometimes “mammal-centrically” referred to as the Age of Mammals, these warm-blooded, fur-covered creatures diversified into a wide range of beasts, including humans. While many of the land mammals got very large, they never matched the recording-holding dinosaurs for superlative size on land.

The largest animals ever known to have lived actually evolved after the dinosaurs and are in fact alive today. An ancient lineage of mammals returned to the oceans and evolved into the modern whales. (See the note about the largest animals feeding upon the smallest).

People are always excited about the Carnivores, or meat-eating mammals. There is something about the dangerous and frightening that excites our primitive nerve centers, so the carnivores are among the most popular at the zoo. (Technical note here—the word carnivore is used in two ways. Carnivore (with a capital “C”) can refer to the class of mammals, the Carnivora, most of whom, but not all, are carnivores (with a lower case “c”), meaning they eat meat. So, not all carnivores are Carnivores, and not all Carnivores are carnivores. Got it? Good.) (Also, see the series on Dangerous Animals for additional exciting facts.)

For example, I recall a visit to the Cincinnati Zoo, and while watching the famed white tigers my young daughter was thrilled when one watched her intently and kept pace with her on the ground while she ran giggling high above on the wooden walkway. She thought that it was a special treat to have one of these magnificent animals take a special interest in her. She felt less special when we mentioned to her that the tiger may not have had cuddling on its mind.

Elsewhere (see related posts below) we have discussed the Giant Short-faced bear (GSFB), Arctodus simus, the great bear from the Ice Age that lived across North America. The GSFB is the largest mammalian Carnivore known, but just how big was it?

Recreation of the Giant Short-faced bear showing its size next to a human

Recreation of the Giant Short-faced bear showing its size next to a human

Many people have examined this question, and one study lays it out clearly (Christiansen 1999). Christiansen examined both the GSFB and its European cousin, the Cave Bear (Ursus spelaeus), another bear famous for its dimensions. Several skeletal measurements have been shown to correlate to overall body mass in mammals. It makes sense that large species have bones of greater relative diameter than small species, and the relationship is more or less linear. By making these measurements a very good estimate of body mass can be made for extinct mammals.

Christiansen used many skeletal measurements of modern carnivores with known body mass to create his linear equations and then plugged in both species of bears to see what the formulas suggested. The results of this study are clear—the GSFB far outweighed any of the modern bears and the cave bear.

These data suggested that a typical (average) GSFB would have weighed in at about 1,700 pounds. Given that there are exceptional individuals, it is estimated that a really large specimen could easily have weighed more than 2,200 pounds. In contrast, the cave bear seems to have a mean body mass of about 1,000 pounds, with exceptional individuals approaching the average for the GSFB.

To further help put this in context, below is a list of select modern and extinct animals and their average body masses. I threw in a couple of dinosaurs for good measure:


Body Mass (pounds)

Blue Whale


Brachiosaurus (extinct)


T. rex (extinct)


Giant Short-Faced Bear (extinct)


Kodiak Bear


North American Lion (extinct)


Cave Bear (extinct)


Polar Bear


African Lion


Indian Tiger


American Black Bear








Velociraptor (extinct)




Gray Wolf




Red Fox


No matter how you look at it, “Giant” is a good name for Arctodus!

Christiansen, P. 1999. What size were Arctodus simus and Ursus spelaeus (Carnivora: Ursidae)? Ann. Zool. Fennici 36(93-102).

Related posts:

GSFB, a Northern California Original

Denning behavior in the GSFB

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Scientifically Authenticated Dinosaur Model Kits Now Online

Guest Post

For the Dinosaur connoisseur and collector, you will find what you have been looking for at Dinosaur Model Toys.com. The creator of all the works featured on this site is not only a gifted sculptor, but actually works with dinosaur fossils as a paleontological reconstruction artist, fossil preparator, and field technician at the Natural History Museum of Los Angeles. His artwork is based on the latest scientific research, real fossil material, and years of hands on experience. This is why the work featured is regarded as some of the most scientifically accurate available to the public.

The new Dinosaur Galleries at the Natural History Museum of Los Angeles will feature many of the artist’s creations. Most notable is the baby Tyrannosaurus rex estimated to have been two years old when it died, for which nearly ninety percent of the skeleton will be recreated for this mount. This sculpted reconstruction will be featured with two real T-rex specimens, one a six-year old, and the other the sub adult specimen named “Thomas” which Doyle Trankina helped collect, and prepare. Thomas is estimated to be about seventy percent complete, making it one of the top five most complete in the world. Our initial offering will be a series of cast resin models and limited edition bronze sculptures with both a highly detailed exterior view, and a rendition of the internal skeletal anatomy of an adolescent T-rex similar to the Thomas find.

As part of the Dinosaur Institute at the Natural History Museum of Los Angeles Doyle Trankina has attended several field excavations in Montana, Utah, and the Mojave. While in the field Doyle prospected, and assisted in the collection of several specimens, most notably Thomas the sub adult Tyrannosaurus rex that will be gracing the museum’s new Dinosaur Gallery in 2011. Through his experiences with the museum with his private obsession with prehistoric life and the natural world, Doyle has produced several sculptures and illustrations for exhibition and publication. Doyle has an extensive list of sculptures to produce over the next two years. His work will require lots of observational study from the museum’s collection, and extensive extrapolation based on the latest research, and modern analogues like birds, and crocodiles.

After completing the preparation of Thomas, Doyle embarked on a half skeletal, half flesh reconstruction of an adolescent Tyrannosaurus rex at 1;24th scale. The detail and fidelity to the skeleton was accomplished by long study of the anatomy from several existing mounts, scientific publications, and photographs from the some of the best Tyrannosaurus specimens. The teeth were surfaced to provide the accurate thickness and semblance to where the tinny serrations would have lined the many teeth. Because the position of the serrations actually change on the teeth as they move back towards the throat, the ridge implies the appropriate location of the serrations. The scales were carved individually so that the skin wraps around the form in a realistic, and accurate way.

Doyle is currently working on a skeletal reconstruction of a baby Tyrannosaurus rex which will be mounted in the new Dinosaur Galleries with Thomas and an intermediate specimen as an illustration of age progression. The actual specimen is only known from a skull fragment from the snout of what is believed to be from a two-year-old Tyrannosaurus rex. There are no post cranial remains, and there are only a handful of examples that are believed to be that of baby dinosaurs. This project has just begun, and with Dr. Chiappe Doyle will be making history in presenting the worlds only mounted baby Tyrannosaurus rex specimen.

Fall of 2009 marked one of the biggest Paleontology news splashes, featuring N. America’s smallest dinosaur, Fruitadens haagarorum. Nearly 150 million year old, the tiny Fruitadens would have shared its life with such titanic beasts as Brachiosaursus, and Allosaurus in the late Jurassic. It is thought that the animal might have weighed as little as two pounds and measured only 28 inches in length. Fruitadens was discovered in Colorado in the late 1970s in a geological formation known as the Morrison, more specifically in an area called Fruita, for which the specimen was named after.

Artist reconstruction of the dinosaur Fruitadens

Artist reconstruction of the dinosaur Fruitadens

The strange dentition of this animal implies that Fruitadens might have been omnivorous, eating plants and at least insects if not small vertebrates. Doyle has produced the first and most accurate illustrated and sculpted reconstructions of this animal. Fruitadens belongs to a family of early dinosaurs called heterodontosaurids, which share many interesting features, one of which are the teeth. Fruitadens like other heterodontisaurids have varied dentition, and in the front of the mouth sits a canine like tooth on the lower jaw. His work was featured on every major news source in the world, and five of the sculpted Fruitadens will be featured in the new galleries in 2011. In his studio, Doyle is currently working on a scale Fruitadens, which will be approximately 30cm long . This will be the only scaled sculpture of the animal, and the first and only for sale. The full scale version is not for sale and can only be seen at the Museum.

Doyle is also concurrently working on Mamenchisaurus, a long neck dinosaur and part of the branch of Sauriscian (lizard hipped dinosaurs) known as Sauropods. As the prospects of obtaining a casting of the Chinese mamenchisaur skull proved too difficult, Doyle was charged with the task of reconstructing the skull from two dimensional reference and other dinosaurs like Camarasaurus for comparison, and to gain familiarirty with Sauropod skull anatomy. The rare skull was found in China and researchers provided a paper with a detailed description and several scientific illustrations. Sauropod skulls are rare because they are so frail in construction, have several small bones that usually disarticulated some time after the animal dies, and are not commonly preserved in fossilization, or are so disarticulated and in such small pieces that they are nearly impossible to find.

Doyle Trankina is a sculptor, illustrator and fossil preparator at the Los Angeles Museum of Natural History. For unique scientifically authenticated Dinosaur Art, Dinosaur Models and Dinosaur Resin Model Kits, visit his online store Dinosaur Model Toys.Com.

Many other interesting dinosaur facts can be found here at Boneblogger.

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