Supplementary Information to Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages by Thomas R. Holtz, Jr., illustrations by Luis Rey


With Expanded Introductory Information
Updated [sometime shortly after] 31 January 2014


This page is dedicated to keeping you updated with a list of all known genera of Mesozoic dinosaurs, arranged according to the groups to which they belong. This list is provided as an Adobe PDF format, which is readable by most web browser programs and printable on most computers. If you need to get a copy of Adobe Acrobat Reader, you can go here to download a copy of the software.

I also include an expanded version of the introduction to the dinosaur genus list. This includes material that was going to be in the published version of the book, but had to be cut out to save on space.

I will try to update this list when the opportunity arises, hopefully once a season. The first update was 31 July 2008. That update included the addition of 108 new genera and 55 new classification categories. If you are interested, here are the new additions:

These new additions are highlighted on the list with an "*" if it is a new genus, with a "^" it is a new name for a genus without a genus name in the original list; and a "**" if it is a new classification category.

Expanded Introductory Information:

In the following list, I've arranged all the known genera of Mesozoic dinosaurs according to the groups to which they belong. A genus, as you may recall, (if not, see chapter 7) is the one-word name that we typically use when talking about dinosaurs. Tyrannosaurus, Triceratops, and Ankylosaurus are all examples of a genus. Each genus is a group of one or more species. Most dinosaur genera are known from only a single species, but a few (such as Psittacosaurus, Apatosaurus, and Edmontosaurus) are known from several different species. Each group of genera is shown in the same order as their respective chapters in this book.

Some things to note: I have not included genera of Cenozoic dinosaurs--that is, modern birds and the other birds that lived after 66 million years ago--in this list. There are simply too many of them! And since dinosaurs are being discovered and named at a rate of about two new genera per month, this list will lack a few recent names. (In an illustrated book such as this, there is a minimum time of approximately three months between when the text is released to print and when finished books are available in bookstores and libraries.) Also, in some cases, the placement of a particular genus in a group is very uncertain. This can happen when a genus is known only from a very incomplete fossil, or when it has a confusing mixture of features. I've excluded dinosaur genus names that are based on material so fragmentary that it is very difficult to say what groups they belong to.

Some dinosaurs are currently without proper names. For example, there is a dinosaur that was once called "Ingenia." Unfortunately, there is also a nematode worm called Ingenia, and it was named first! So by the proper rules of naming, the worm keeps the name and the dinosaur needs a new one. In 2013, the "Ingenia" dinosaur was given the new genus name Ajancingenia.

Also, there are dinosaur fossils that were once considered new species in previously named genera, but which turn out not to really belong to those, or to any other already named, genera. These will eventually get their own genus name when newer studies are completed. Because some of these species are interesting (maybe they are the only member of their group from a particular time or region; maybe they have some peculiar feature), I've put them in the appendix, too. These unnamed (or at least un-genus-named) dinosaurs are being studied, and as those names are finally given I'll make sure they get included in future versions of this list.

Also, paleontologists and biologists who work on modern animals, I might add, sometimes disagree on whether two particular species belong to the same genus or to two different genera (see chapter 7). I've tried to indicate some of these differences of opinion in this list, which is based on my interpretations of the best classifications.

For each genus, I list the name and what it means.

I also give the dinosaurs age: both the geologic epoch it comes from and approximately when (in millions of years ago) it lived. Unfortunately, our understanding of how old a dinosaur was is only as good as our understanding of the age of the rocks it was found in. The ages of some rocks are pretty well known: for these dinosaurs, we have very narrow time ranges. For others, though, the geologic ages are much less certain, so I list much longer possible ages for the oldest and youngest that dinosaur might be. Future studies should narrow those ranges down. In the 2015 updates the range of some of these ages have become very narrow. This is because some long on-going projects to precisely plot where each fossil specimen was found in certain geologic units--and when in time those particular layers were deposited--have finally been published. This much greater precision is giving us a better idea of which dinosaurs lived at the same time as each other. It also suggests that MOST dinosaur genera probably lasted for only a million years or so; if we knew the geology better, and had more samples to examine, we could probably narrow down the age ranges of most of the dinosaurs on this list to just a million years.

I give the length for these dinosaurs, based on the largest specimens. (Of course, for dinosaurs that are only known from babies, those "largest specimens" are a LOT smaller than the adult would be!) Since most dinosaurs are known from incomplete fossils, these measurements are often just guesses. Particularly wild guesses are marked with a question mark. (After all, since many dinosaurs are mostly tail and neck, and since tails and necks vary widely in some groups, it is pretty tough to make even a reasonable guess.) And since some dinosaurs are known from just a few tail bones or the like, there is no way to be accurate for these lengths. In these cases, I have just put a question mark. Keep these facts in mind. Also, keep in mind that the largest individuals may not be a typical individual. After all, consider really tall basketball players or really massive (American) football linesmen: they show that there are people who are much larger than the average individual, but still part of the normal variation of our species. The same was true of dinosaur species: not all Tyrannosaurus rex adult males would have been exactly the same size!

Keep in mind also that many dinosaurs are known from only a few individuals, so are unlikely to be large individuals. And even more importantly, they might not even be adults! In fact, even in some of the best known dinosaurs (Allosaurus and Apatosaurus are two good examples) we do not have definite adult individuals known, so the actual largest size of these genera is not yet known.

Weights are even tougher to determine. A baby dinosaur of just a few pounds could grow up to be a dinosaur weighing dozens of tons. So where I can, I give the weight of the biggest individuals. Instead of given exact numbers (which sound pretty accurate, but are really just guesses), I list a modern animal of around the same size as that dinosaur. Here is the list of modern animals, the weight they represent, and other modern animals in that size range:
Modern Animal Weight Range Other Modern Examples
Sparrow Less than 2 oz (57 g) House Mouse; Finch
Pigeon 2-16 oz (58-453 g) Blue Jay; Robin; Rat
Chicken 1-5 lbs (0.45-2.27 kg) Crow; Hawk; Seagull
Turkey 5-20 lbs (2.27-9.1 kg) House Cat; Goose; Raccoon
Beaver 20-50 lbs (9.1-22.7 kg) Lynx; Jackal
Wolf 50-100 lbs (22.7-45 kg) Baboon; Goat
Sheep 100-200 lbs (45-91 kg) Leopard
Lion 200-500 lbs (91-227 kg) Tiger
Grizzly Bear 500-1000 lbs (227-454 kg) Zebra
Horse 1000-2000 lbs (454-907 kg) Bison; Kodiak Bear
Rhino 1-4 tons (0.9-3.6 t) Hippo; Giraffe
Elephant 4-8 tons (3.6-7.2 t) Killer Whale

For dinosaurs of 8-16 tons, I've listed them as "two elephants"; for 16-24 tons, "three elephants"; and so on. For comparison's sake, the largest blue whale ever recorded (the largest animal known) was 209 tons and would be listed as "27 elephants" according to this scale.

As with length, though, there are plenty of dinosaurs that are known only from very fragmentary fossils. For ones where I could guess the weight even approximately, I've indicated that with a question mark next to the weight; for those that are just too hard to figure out, I've just put a question mark.

Estimating the masses of dinosaurs and other animals from fossils is exceedingly difficult. There are many complicating factors: how much fat they had (was it a good feeding season or a bad one?); how much muscle they had; etc.; etc. Different paleontologists have used different techniques. Some use laser scans of nearly complete skeletons, then create computer models based on the skeletons to get the volume. Others use measurements of individual bones, and used equations based on the size of more complete skeletons to estimate the size of bipedal and quadrupedal dinosaurs. But these estimates are just that--estimates--and so it is hard for us at present to figure out how accurate they are (that is, how close the calculations are to the actual masses.)

Also listed is the place where each dinosaur has been discovered. Of course they lived other places, too. In fact, you can pretty much guarantee that if a dinosaur species is known from fossils in (for example) Montana in the northern part of the western U.S., and New Mexico in the southern part of the western U.S., it almost certainly lived in the states in between. We just haven't found the fossils of it from there yet.

Finally, I mention some additional comments or fun facts about each dinosaur genus.

Here is the most recently finished Updated Genus List (18 January 2015).

I really want to give my thanks to Mr. Fred Barmwater of Highlands Ranch, Colorado. He helped in compiling the old data in a way that was easier to update. If you happen to see Mr. Barmwater while at the Denver Museum of Nature and Science, or anywhere, please thank him for helping me out! Additional proof-reading help has been provided by "Albertonykus", Pete Bucholz, Barbara Peterson, Christian Schley, Adam "Oxalaia" Schmoetzer, and Hans-Dieter Sues.

because dinosaurs have so many fans, the dinosaur pages on Wikipedia are often very up-to-date. (But make sure to check out the reference sources for any Wikipedia page, to see if they are using the latest information.)

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Last modified 17 December 2019

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