Category Archives: Animals

Unusual Fossil Occurrence in Travertine

A number of years ago, when I was an undergraduate student, I had the privilege of going with my adviser on many trips in the field. I learned more on those trips than I think I did in the classroom. On one trip he took me to several hot springs in the Black Rock desert of central Utah, and I got to observe the deposition of travertine first-hand.

Black Rock travertine

Travertine is a carbonate deposit most often associated with hot springs. As the water travels through the Earth and is heated by some deep, magma source, and then circulates back to the surface, it dissolves a host of minerals. On the surface, through either evaporation or the action of microbes the minerals precipitate out of the water, slowly building up layer upon layer of stone. The vesicles and contaminates of the travertine give is unique and interesting texture, and thus make it a popular decorative stone for tiles.
Several years prior to my visit with my professor, he was there with another student and they studied the travertine and hot springs of the region, and they found the remains of a fossil bird, an American Avocet, preserved in the stone. It seems that the bird had died in one of the hot springs, and the travertine formed around the bird’s skeleton, preserving impressions of feathers as well as the bones of the body.

American Avocet skeleton preserved in travertine

In addition to the bird, remains of insects in the travertine were common. These fossils give new meaning to the term set in stone.

For other stories on travertine, see:
An introduction to travertine tiles
Advice on installing travertine tiles

Dangerous Animals

In his song “Sail away,” Randy Newman sings about how good we have it in America. The land is bounteous and its wild inhabitants are peaceful. “Ain’t no lion or tiger, ain’t no mamba snake, just the sweet watermelon and the buckwheat cake.” Of course, Newman is known for lyrics that intentionally are outrageous contradictions, but in this case, he is mostly right.

North America is blessed with a general paucity of dangerous beasts, and it is very safe to venture into the wilderness and not worry about being eaten or molested by nature, aside from flies and mosquitoes. However, for many, dangerous animals are exciting, and there is much misinformation about the wilds. So, this is the first of a series on the dangerous animals of North America, or at least the ones that often get a bad rap as being dangerous.

I undertook a survey of animals that are known to have caused human death, and worked to separate truth from fiction. Death caused by animals does happen. However, it is a relatively rare event in North America, even if it generates a lot of media interest when it does happen. And the identity of the most dangerous animals might just surprise you. So explore all the dangerous animals.

Posts in the Dangerous Animals Series:

Sharks
Venom, poison, and toxicity
Number of venomous snakebites a year
Venomous snakes of North America
Mountain Lions
Bears
Spiders

Average number of deaths per year caused by various animals

Number of venomous snakebites a year and pitfalls in scientific research

While doing a literature search for another story I encountered a classic pitfall in scientific research that one can all too often find. I wanted to know how many venomous snakebites occur each year, and of those, how many are fatal.

I dug into the literature to see what was there. My first stop was Wikipedia. With experience, I have learned that for science issues, Wikipedia is often very good. The wiki format mirrors the scientific publication process where contributors double check facts and each other, and on subjects that I know something about I find it to be a good general source.

I found a statement that there are approximately 7,000 – 8,000 people bitten by venomous snakes each year, and of those about 5 die. Even better, this statistic was given a reference (Henkel ?), as well it should. So, being curious about the original research, I looked up the citation. And here is where the pitfall begins.

In order to conduct science and add to human knowledge we must necessarily build on the work of others. One of the characteristics of science is that results must be repeatable—that is, in theory I could redo the work of any other scientist and get similar results. It is impractical for me to begin every research project by completely re-doing the work of all those researchers before me, so we cite their work and trust in it. (This also explains why scientists can be vicious anytime someone is caught fudging results—we have to be able to trust each other). However, sometimes you encounter what I will call the “chain of citations” pitfall.

A copperhead snake, Agkistrodon contortrix, perhaps one of the most beautiful snakes in North America.

This pitfall is in the sloppy application of the scientific process, not with the process itself, and happens I guess out of laziness. It is where an author cites a point of fact from a research paper which may reference the fact (secondary source), but was not the paper where the research was presented in the first place (primary source).

I looked up Henkel and it turns out to be an interesting blurb from an appendix on safety, and he cites Gold et al. (2002), an article with the promising title “Bites of venomous snakes.” Ah, I think, here is the original research, so I look it up.

Those authors say “The true incidence of bites by venomous snakes in the United States is probably 7,000 to 8,000 per year, of which 5 or 6 result in death,” (pg 347) but they cite other authors for this fact, Langley and Morrow (1997).

This is getting silly, I think. How deep does this rabbit hole go? So I look up Langley and Morrow (1997).

The Langley and Morrow paper is a summary of deaths caused by animals of all kinds between 1979 through 1990. They compiled data from the US Department of Health and Human Services as published in Vital Statistics of the United States. They found that an average of 157 deaths occur each year as a result of injuries from animals, and about 60 of those came from venomous animals of all kinds, the majority being bees and wasps. They found an average of 5.5 deaths from venomous snakebites (Langley and Morrow 1997, table 2).

So, here at least we do have some original research on the number of fatalities each year. But how many bites? Langley and Morrow say “Approximately 45,000 snakebites occur each year, of which 8,000 are inflicted by venomous snakes,” (pg 12) and they cite Gold and Wingert 1994. Ok, let’s see what they say.

Gold and Wingert (1994) say “Approximately 45,000 snakebites occur in the United States each year. Poisonous snakes account for an estimated 8,000 of these bites, which result in approximately 9 to 15 fatalities,” (pg 579) and they cite Parrish (1966).

Finally, with Parrish (1966) we got to a paper that tries to determine not just the number of deaths from snakebites, but how many snakebites there are. Parrish (1966) conducted a survey of hospitals and physicians in both 1958 and 1959 to determine the number of snakebite victims treated. He sent questionnaires to a representative sample of both, and based upon the results, extrapolated to the total number of bites.

He wrote “On the basis of all these various reports, I estimate that approximately 6,680 persons in the United States (excluding Alaska and Hawaii [they don’t have venomous snakes]) were treated for poisonous snakebites during 1959,” (pg 272).

There are two numbers I cannot find in Parrish: 45,000 total snakebites and 8,000 venomous snakebites. I have no idea where these numbers originated since all the authors cite it, and all references point back to Parrish. Maybe the 45,000 number is a wild guess, and 8,000 is some adjustment to Parrish’s 6,680 number based on population growth? There is no way for me to know.

But this clearly shows the danger of relying on what the last guy reported and citing him as the authority when that is not what his paper was about. I tell my students to find the original publications and this is why. The number of deaths per year (about 5) is reasonably documented with the work of Langley and Morrow (1997), and in a more recent follow up study (Langley 2005). But, how many venomous snakebites occur in the United States in a year? Based on this evidence, we do not have a clue.

So here is a research tip, free of charge, to all you young budding scientists: go find the answer—just send me a copy of the results. Scour the literature to see if I missed something. Then, determine a good way to address the question and see if you can improve our understanding. The most recent data are over 40 years old, and inquiring minds want to know.

This post is in the dangerous animals series. Check out that post for more information.

Gold, B. S., and W. A. Wingert. 1994. Snake venom poisoning in the United States: A review of theapeutic practice. Southern Medical Journal 87(6):579-589.

Gold, B. S., R. C. Dart, and R. A. Barish. 2002. Bites of venomous snakes. New England Journal of Medicine 347(5):347-356.

Henkel, J.? For goodness snakes! Treating and preventing venomous bites. U.S.D.A. emergency response.

Langley, R. L. 2005. Animal-related fatalities in the United States–an update. Wilderness & Environmental Medicine 16:67-74.

Langley, R. L., and W. E. Morrow. 1997. Deaths resulting from animal attacks in the United States. Wilderness & Environmental Medicine 8(1):8-16.

Parrish, H. M. 1966. Incidence of treated snakebites in the United States. Public Health Report 81(3):269-276.

New evidence on the sizes of pterosaurs

The flying reptiles, pterosaurs, were an amazing successful group of prehistoric animals. They ranged from the Late Triassic through the end of the Cretaceous periods, a span of time of about 156 million years. That is over 2 times longer than the time since dinosaurs became extinct, and mammals have dominated the terrestrial landscape.

Pterosaurs were the first vertebrates to achieve powered flight, followed later by the birds and bats. However, during their hay-day, pterosaurs achieved an incredible range of diversity in form and size, and occupied countless niches within the Mesozoic world.

Interestingly enough, the first pterosaur remains to come from North America were found in Kansas. Flying reptiles had been known from Europe, but during an 1870 collecting trip through the western territories, O. C. Marsh stopped off in Kansas. Near the end of the trip he spotted a long, slender bone weathering out of the chalk formation, and collected what he could before heading back to Yale on the train. He thought the bone looked like the finger bone of the pterodactyls from Europe, but this bone was much larger. He estimated the wing-span to be 20 feet. The next year, he traveled back to collect the rest of the animal in the Kansas formation, and found that in fact his estimate of its giant size was correct. He named this new animal Pteranodon.

Greg dusts the life-sized models of Pteranodon sternbergii in the Sternberg Museum of Natural History

As more and more flying reptiles have been found in the fossil record, as basic question about them has puzzled scientists—how well could they fly? Estimating the body mass is a fundamental part of this inquiry. We can look at modern birds and see the constraints that flight dictates for body mass at least today. How do the pterosaurs compare?

In a recent publication, the question of body mass in pterosaurs is addressed (Henderson 2010). In the most detailed study yet of pterosaur body mass, Henderson set out to explore this question and to compare the results to birds. He created a model of body mass based on modern birds by creating digital, three-dimensional models of their bodies. His model was corrected for differences in density from different areas of the body. For example, the wings will have a different average density than the trunk, where the volume of the lungs greatly impacts its overall density.

Using birds, he refined his model to accurately calculate their masses and centers of gravity. Then, he turned to the pterosaurs. What he found was very interesting. The pterosaurs in his study ranged from less than an ounce for Anurognathus to an astonishing 1,200 pounds in mass for Quetzalcoatlus (more on this in a moment).

The giant pterosaur Hatzegopteryx compared to a modern giraffe. Illustration by Mark Witton.

The giant pterosaur Quetzalcoatlus northropi compared to a modern giraffe. Illustration by Mark Witton.

Excluding the giant Quetzalcoatlus for a moment, the other heaviest pterosaurs were Pteranodon at 41 pounds and Tupuxuara at 50 pounds. The estimates for the ancient fliers are not too far off the masses of the largest modern flying bird the Great Bustard, at 35 pounds. So, we know that it is at least possible for an animal of that weight to get airborne on a regular basis.

So, what about the giant Quetzalcoatlus? This animal is known from fragmentary remains from Texas where it was first found in 1971. While mostly known from fragmentary remains it is estimated that it had a wing span of 37 feet or more. Earlier estimates of the weight of this animal vary widely from 141 – 608 pounds. Henderson points out that many of the body mass estimates of the past were influenced by engineering constraints calculated for an animal with this great wing span to be able to fly. The thinking being that an animal evolved from flying animals most likely flew.

But, in an interesting twist, Henderson’s estimate is twice as much as previous estimates, so he turns the issue around and suggests the heresy that maybe giants like Quetzalcoatlus (and I would add Hatzegopteryx by extension) did not fly. Instead, it is perfectly reasonable to assume that a formerly flying species secondarily adapted to a fully terrestrial life style, growing to dramatic size as a protection from predation or for other similar advantage. We certainly can find examples of that in the modern birds too, in the flightless ratites, the emus and ostriches.

No doubt this issue will continue to be explored (for an alternative view see The largest pterosaurs have not been grounded yet) . That is the fun of science—keep probing and answers, and more questions, reveal themselves.

Henderson, D. M. 2010. Pterosaur body mass estimates from three-dimensional mathematical slicing. Journal of Vertebrate Paleontology 30(3):768-785.

Accurate Dinosaur Toys

If your kids are fascinated by dinosaurs, and many are, you might like a recommendation on some of the best dinosaur toys out there. Being a paleontologist and museum professional for many years I do have some experience with quality dinosaur models.

Without a doubt some of the best and most accurate models you can get for dinosaurs and other prehistoric animals are from the Carnegie Collection. A number of features of these models, produced by Safari, make them highly recommended.

First, most of the models were sculpted to the same scale, 1:40. This means that almost all the models can be directly related to each other, so you can easily compare the size of a Brachiosaurus with an Apatosaurus, for example. Not every model is the same scale however, so you do have to watch that as it could be misleading.

Sauropod dinosaur models from the Carnegie Collection. Left to right are Camarasaurus, Diplodocus, Brachiosaurus, and Apatosaurus.

Another significant thing about the Carnegie dinosaur toys is that they are all hand painted, meaning that there are no two models that are identical. Each one is a bit different and special.

Finally, the models have been in production since 1989, and they add new species to the series almost every year. Some species from the series are retired from the line, meaning they are no longer available commercially, which might give them some collector appeal. And occasionally species already represented in the series are re-sculpted based upon new scientific evidence about their appearance or mode of life.

Various dinosaur models from the Carnegie Collection. Back row, left to right, Spinosaurus, Kronosaurus, Plesiosaurus, Deinosuchus, Tyrannosaurus. Front row, left to right, Allosaurus and Pteranodon.

The Carnegie models are some of the most accurate dinosaur toys on the market today, and we use them regularly in our museum education programs. If you are looking for some great models, these are hard to beat.

Pick yours up at the Boneblogger store. Look in the recommended section.

Boneblogger: Science and the outdoors

Exploring the natural world