Last week I posed this challenge. What real animal combines traits from the kiwi, anteater, and hedgehog. Chase and Herman Diaz came up with the correct answer.
The animal that has the traits of these three animals is the echidna, also known as the spiny anteater. Named for the “mother of all monsters” in Greek mythology, the real echidna looks like a combination of other animals, much like the mythical Echidna herself, who was part woman, part snake.
When people think of weird mammals, echidnas are very often at the top of people’s lists. It has several traits that are commonly mentioned. First, it is a monotreme, a group of mammals that lay eggs. Today, monotremes consist only of echidnas and platypuses, but in there were several others in the distant past. Platypuses are so strange that people at first thought it was a fraud. Who would believe an egg-laying mammal with the face of a duck?
Second is their fur, which has numerous sharp spines, similar to that of a hedgehog. Because these spines are modified hairs, they have limited control of them. Just like other mammals can make their hair stand up (humans know this chiefly as “goosebumps”), the echidna can make its spines stand up, although they can’t shoot their spines like some people would have you believe.
That fact the echidnas lay eggs makes their reproductive system rather different from almost all other mammals. Internet sites always want more people to click on their site, so echidna reproduction gets a lot of discussion. An internet search will immediately turn up comments and pictures of the four-headed penis of the males and the fact that the females have no nipples, instead feeding their young (called puggles) through glands in their pouches (yes, they have pouches like marsupials) which secrete the milk that the young lap up. You can even find talk of the mating trains echidnas can form during mating season, in which the males form a line behind the female and follow her around for upwards of six weeks until she finally decides to mate. Then they dig a trench around her, jump in and try to push each other out like some sort of bizarre sumo contest. The last male still in the trench wins the right to breed first.
Much like many reptiles, which have what is termed a hemipenis (a two-headed penis), the male echidna only uses half of its penis at a time. In the echidna’s case, that means that they use two out of the four heads at any one time, which is good, because the female echidna has two uteruses. We’re still not done with the weirdness. Because the female may mate with several males, the sperm joins into one large mass, a super-sperm if you will, that together, can swim faster and stronger than any of them separately.
There are several traits that the echidna shares with the platypus, in addition to laying eggs. The echidna is edentulous, meaning it has no teeth. It does, however, have an incredibly fast tongue; able to slurp up the ants, termites, and other insects at the rate of 100 licks/minute; thus its name Tachyglossus, which means “swift tongue”. It also has a very sensitive beak that is electroreceptive, meaning it can detect the tiny bioelectrical signals given off by the insects for which it forages. Additionally, echidnas have a spur on its hind legs, although unlike the platypus, it is not venomous.
So what does it mean to be a monotreme? The Tree of Life web project has an excellent and clear summary of what a monotreme is scientifically. Evolutionarily, the monotremes are the oldest true mammalian lineage, splitting off the line that led to placental mammals sometime around 200 million years ago (as a point of reference, the oldest known dinosaur was found in rocks dating to 230 million years ago). Much of what we consider to be mammalian had yet to evolve by this point, so there were still several traits monotremes shared with reptiles that were derived from the common ancestor of both the reptiles and mammals. This split was so early in fact, that the middle ear bones developed independently from other mammals.
My personal favorite of all the strange things about the echidna is its thermoregulation. When people think of mammals, besides for milk glands and fur, they think of “warm-bloodedness”. Thermoregulation is far more complex than most people realize. There is much more than “warm- or “cold-bloodedness”. Better descriptions of thermoregulation are endothermy (temperature controlled internally)/homeothermy (maintains constant temperature) and ectothermic (temperature strongly influenced by environment)/poikilothermic (temperature fluctuates). But these are just endpoints on a spectrum. Perhaps no other animal illustrates the variation better than the echidna.
The echidna does it all. At various times, the echidna displays endothermy, ectothermy, homeothermy, and poikilothermy. It hibernates, it goes into torpor on a regular basis. The echidna is also a eurytherm, meaning that it can operate just fine at a variety of temperatures without loss of function or activity levels. Whereas most mammals would lose function and coordination if their bodies cooled even a couple of degrees and would completely shut down if they cooled ten or more degrees, the echidna gets along just find even when its body cools to 20 C (that is 68 F for those in the US, a temperature at which we would be long dead).
Needless to say, it is a heterothermic animal. Heterothermy is when an animal lets its body temperatures fluctuate. While it is a broad term that includes poikilothermy, it is typically distinguished from poikilotherms by being under the control of the animal and/or by being regional, meaning that different parts of its body have different temperatures. The classic example of this is the deer, in which the legs are allowed to get cold while the body stays warm. African elephants do this somewhat in reverse, shunting blood to their ears allowing them to heat up, thereby dumping heat from their core body to their ears, which can then cool off more readily due to their large surface area. Of course, few mammals can beat the camel, allowing their temperatures to vary as much as 7 C throughout the course of a day.
Anyway, back to the echidna. Check out this graph. In this study, the researchers measured the body temperatures of a female echidna for 13 years. The graph shows temperature ranges for one year. Another study found that the echidna typically maintained temperatures when active at around 32-33 C (as compared to our 37 C) and dropped to 27-28 at night when it was inactive, although it could drop to as low as 4.7 C and still get up and have normal activity during the day. This variability not only allows it to use less energy, but it also allows it to tolerate temperatures as high as 42 C. Starting the day cold allows it to absorb more heat during the day without overheating. And it is not just its temperature that it allows to vary. The echidna can vary its metabolic rate while still maintaining its normal activity levels. Of course, when it needs a stable body temperature, like for instance, when it is incubating an egg, it can do that too.
All told, the echidna is a pretty amazing animal. It is also about as close as we are going to get in a living animal to see what our mammalian forebears were like in the early years of mammalian existence.
The natural world can be a very strange place. WTF evolution?! is a great site that takes a humorous look at some of nature’s weird turns. Today I am going to celebrate some of nature’s curiosities by playing a game. Some animals are so weird they look like combinations of other animals. For instance, the platypus is often said to look like a cross between a duck and a beaver. I will provide a fictional cross between a set of animals. See if you can guess what real animal it might be. Then come back later to see what animal it is and description of what makes it such a curious animal.
For today’s cross, what might you get if you cross a kiwi (the bird, not the fruit) with an anteater and a hedgehog? I will give you a hint. It is an extant animal, so you can rule out any fossil animals.
Last week we posted a new fossil. Were you able to figure it out?
This particular picture is of the ant, Nylanderia vetula, caught in Dominican amber. Dominican amber is from the Miocene, currently thought to be about 25 million years old. The fossil ants from Arkansas are a bit different.
In 1974, ants were found in amber collected near Malvern, Arkansas, from the Claiborne formation, which is listed as being from the Eocene, roughly 45 million years ago (give or take 3 million years). According to the Arkansas Geological Survey, the Claiborne is a series of fine sand to silty clay layers, with interspersed layers of lignite. The lignite and amber are clearly indicative of terrestrial environments, although there are some marine sediments within the formation. A number of fossils have been found in the formation, including fish and reptile bones and teeth, leaf impressions, trace fossils, and of course, wood and amber.
The specific ants that have been found were identified as Protrechina carpenteri. These ants are in the group Formicinae, one of the more common ant groups. Interestingly, the Eocene ants were anything but common. Ants during this time shifted from the earlier ants to a more modern collection of species. They were quite diverse, with Phillip Ward reporting that David Archibald claimed some of them were the “size of small hummingbirds”.
Images of our Arkansas fossil ant are hard to find, as in, I couldn’t find a single image. However, if you want to see the real thing, go to the Harvard Museum of Comparative Zoology, where Antweb.org reports it is being held. Yet another Arkansas fossil in the hands of another state.
For those of you who are new to the website, under the Arkansas Fossils tab is a list of fossils that have been reported in Arkansas. For those of you returning to the site, you will find a new addition to the page. Using the Arkansas Geological Survey regions map, I have marked where in the state fossils have been found. Want to know where to find conodonts? Looking for dinosaurs? Check the map to get a general location.
At some point, I would like to make the map interactive, so that visitors can click on the map and be taken to information about that fossil. Unfortunately, I do not yet have the technical ability to do that for this WordPress template. Should someone find such task within their abilities and has an interest in contributing to the site, please contact me.
Here is the map you can find on the fossils page.
Time for a new Mystery Monday fossil. The fossil on display here was found in Dominican amber, as well as Russia. But it has also been found in Arkansas and played a role in our understanding of the evolution of this group of animals. Leave your identifications in the comments section and come back Friday for the answer.
I have been going to Mid-America Museum in Hot Springs, AR for many years now. I even got married there. Nevertheless, there were a few things that always frustrated me. They had a mastodon skeleton in the entry way, which was great, but there was no real signage with it. It was just there, with no context at all. But more than anything else, I despised the sign they had next to a sauropod track next to the mastodon. Two incredible dinosaur trackways have been found in Arkansas and Mid-America is one of the few places you can see anything of the trackways. But the footprint, again, had no context and the sign had the sauropods wading around in swamps, straight out of a 1950s drawing. I repeatedly told them about the sign, I even offered to make them a new one, but to no avail.
So when I heard about the museum shutting down for several months to be completely renovated, I hoped they would fix some of these things. Mid-America Museum is now open again and I got the chance to visit it recently. My verdict? They did a great job, better than I even dared hope. Like anything else, there are still a few things they could do to improve it, but the earth science exhibits are well worth taking some time to go see them. It’s a completely new museum. You should definitely check it out.
To go along with the radical renovations, it is now the Mid-America Science Museum and Donald W. Reynolds Center. The Reynolds Foundation donated $7.9 million (most places say 7.8 million, but that is because most people don’t know how to properly round, most people just truncate, 7.88 does not round to 7.8), without which the renovations could not have been done. Many of the old exhibits the museum was known for are still there, such as the Tesla coil and moving art structures, but I am going to focus on the earth science exhibits here. There are many other places you can read about the other exhibits, such as this one.
The main exhibit focusing on earth science is called Arkansas Underfoot. It is located, appropriately enough, next to the Arkansas Underground tunnels. With this placement, the tunnel construction is thematically tied to the rest of the museum in a much better way than previously. The tunnels have been cleaned and fixed up. The frayed and broken sections of the rope bridges have been replaced with all new rope. I was disappointed to see that the skeleton of the miner has been removed, but the many appreciative comments from the kids indicates this was a good change. Apparently many kids found it frightening and disliked it. I am still not convinced the stated purpose of this exhibit to allow kids to explore and learn about life underground and what lies beneath our feet is at all effective. I enjoyed a small display of fossils embedded in the wall at one spot, but other than that, there is nothing educational inside and I seriously doubt many of the kids see it because it is situated in a spot that does not lend itself to stopping and looking. Nevertheless, kids really enjoy it and it brings people into the museum where they see other things that are truly educational, and it provides parents a bit of a respite as the kids zoom through it again and again, so it succeeds on that front. I do wish there was a bit more within it that might serve an educational purpose, particularly for the space it takes. I don’t advocate its removal, quite the opposite in fact. It should be added to in ways that enhance its educational value.
The mastodon and sauropod track are here, with the mastodon freshly painted to look more like the real bones from which the casts were made. It looks good and has more of a context with all the other exhibits nearby. The sauropod track has a new sign, which is a vast improvement over the old one. The swamp-dwelling sauropods are gone, replaced by a discussion of the Arkansas dinosaur trackways, including pictures. The trackways really are impressive, much more than they show here (in all fairness, to truly appreciate them would take an exhibit all its own, so what they accomplished here is perfectly reasonable given space constraints and exhibit balance considerations, it is quite sufficient for the intended audience without going overboard), but at least now visitors get a feel for the trackways as being more than an isolated footprint and the incorrect information from the old sign has been replaced with good information. The footprint now has that all important context. Outside still has the dinosaur dig that is popular with the kids, along with the adjacent track site, making a nice continuation of the interior exhibits.
There are several new exhibits to see which are well worth spending time to see. The exhibit that draws the most attention is an interactive 3D topographic map. Using a projector and an Xbox Kinect, they turn a simple sandbox into an endlessly changing map. As people move the sand around, they can see the colors change to match the topography, with snow-capped hills and rivers and lakes that respond to the changes in the landscape. Its draw and fascination is evident by the length of time people spend there manipulating the topography. It is a wonderful interactive display, but there are a couple of ways it could be improved. The actual topographic lines are very dim and go unnoticed by almost everyone, decreasing that educational aspect of the display. Despite a number of maps on display in the exhibit, there are no topographic maps for comparison other than the large map behind the mastodon. I discount that one because it is displayed as monotone wall art without reference to it being topographic in nature, so it runs under the radar for visitors. There is an empty wall right next to the sandbox. I think the exhibit could be improved by putting up a topographic map on that wall, along with a description of how to read it, using text that relates it back to the sandbox, thereby tying it all together.
Speaking of maps, there are several on display. A large geologic map of Arkansas adorns one wall, with explanations of how to read it, much like I suggested above for the topographic map. On the map are listed several places where mineralogical resources have been found and mined. Next to the map is a display showing some of the rocks and minerals that have been mined in the state that are shown on the map, as well as a display showing the major types of rock in the state. In addition, there is a table with several maps of various kinds. My favorite is the color map of the Mississippi river showing how it has meandered all over the area.
On the adjoining wall to the one displaying the geologic map is a series of display cases embedded into the wall showing different soil types, showing how soil changes with depth and region. One is called a Stuttgart soil, which is listed as the state soil of Arkansas. Who knew we even had an official state soil?
At the fossil station, you can look at real microfossils. There is a microscope which lets you see a variety of identified fossils such as shell fragments and echinoderm spines. The signs are good, informative without overloading visitors. The exhibit lets people see fossils that you don’t normally see in a museum and get a feel for the work involved. While I was there, several people examined the fossils and tried their hand at identifying them.
Next to the fossil station is a slice of soil that looks something like a giant ant colony display. Instead of ants and there tunnels, there is bacteria which turn the soil different colors depending on the type of bacteria and their type of metabolism. The signage is great and very informative. I have not seen a display like this before and thought it a great addition. The only criticism I would make is that the lighting is not the best. The lights shine up from the base of the display, so the lights are too bright to get a good look at the lower portion of the soil. You wind up trying to look almost directly at the bulbs between you and the bottom of the display.
Continuing on, there is a rock smasher, where people can drop a heavy weight onto rocks to see pieces break off and fall into a short series of grates separating the pieces into different sizes. I am not sure people were getting the point of the exhibit, which was explained on the adjacent sign, which talked rocks breaking up to form sand, clay, and soil. People seemed to like trying to smash the rocks, though, so hopefully some people looked over at the sign while they were doing so or waiting their turn. Curiously, the sign never actually mentions the word “erosion”, which is what the exhibit is all about.
Between the rock smasher and the dinosaur footprint is a large display of Arkansas quartz. Arkansas is famous throughout the world for its quartz, so it is fitting to see it on display here.
If I were to pick the one display that most surprised me, I would probably choose the taphonomy display. As someone professionally interested in how things decay and form fossils, I particularly loved this display. It is not something you see in museums very often. Taphonomy is the study of everything that happens to an organism between the time it dies and the time it is collected and studied. This display of course, only covers the first part of the process, showing five weeks of the decay of a freshly dead rat. I should warn people that it might be disturbing for some viewers. It is understandable they only go this far in the process, as it is the easiest to show and most relevant to active, biological processes that affect us. The touch panel next to the display allows people to go further into how the decay process fits into the function of a healthy ecosystem. Definitely worth a look. If maggots bother you, you can still learn a lot from the touch screen.
The final piece of the exhibit is a touch screen which allows you to take a virtual field trip through eight different areas of Arkansas, learning about the geology making each area unique and how the underlying rocks affect the landscape. It is well done and you can spend a lot of time going through the different trips. I didn’t have time to go through all of them, but I will definitely be spending more time at this panel the next time I go.
In conclusion, I think they did a great job on the renovation, filling in part of a huge, gaping hole in Arkansas museum coverage. There are still a few places that can be improved, like any exhibit, but what they have done is worlds better than before, providing exhibits you won’t find elsewhere in the state. Take a day out of your weekend and go see for yourself. It really is a new museum, carrying over the best of what was there before and adding in much that will fill your day.
Last week we saw this vertebra and lower jaws of Basilosaurus.
The history of Basilosaurus is intimately tied to Arkansas. Alabama and Mississippi may have claimed Basilosaurus as their state fossil (and indeed the fossils are much more common in those states), but it was an Arkansan that found them. Judge Bry found some bones in the Louisiana portion of the Ouachita River in 1832 and sent them to Dr. Richard Harlan at the Philadelphia Museum. After examination of these bones, along with more bones sent by Judge Creagh from Alabama, Dr. Harlan noted similarities with plesiosaur vertebrae, only twice the size, so in 1834 he named the animal Basilosaurus, king of the reptiles.
In 1838, more bones were discovered in Arkansas, near Crowley’s Ridge. E. L. Palmer published a brief note on them in 1839. Meanwhile, Dr. Harlan had taken his bones to the United Kingdom to see the esteemed Sir Richard Owen, the most prominent paleontologist of his day (even today, he is considered one of the most important researchers in the field). Sir Owen found that the bones were not from a reptile at all, but from a whale. Therefore, he proposed changing the name to Zeuglodon. However, the rule of precedence requires the first name to take priority, so Basilosaurus it is.
Basilosaurus has an important place in the study of whale evolution. In addition to being the first primitive whale identified, Basilosaurus was the first true whale that was an obligate aquatic animal. Since its discovery, several other species have been found, but they all still retain enough limb function to move, however awkwardly, on land. Basilosaurus, due to its size and having no functional limbs other than some small flippers, would have been unable to move on land. As can be seen in the chart above, Basilosaurus was not the ancestor of modern whales, though. It appears that Dorudon, a close relative, had that honor.
Basilosaurus was a huge animal, reaching more than 15 m (50 feet). Neither it nor Dorudon had the forehead melon characteristic of modern cetaceans, which indicates it likely did not have echolocation, but did have very powerful jaws, clearly indicative of its carnivorous diet. A recent (this year) study found that Basilosaurus had an estimated bite force of 3,600 pounds, giving it the strongest jaws of any mammal yet measured.
There is a bit of a problem saying how old Basilosaurus is. The original fossils from 1832, as were the Arkansas fossils, were found in the Jackson Group, a series of intertidal to estuarine and shallow marine sediments of Eocene age, around 37-34 Mya. Another set of fossils from Crowley’s Ridge was found in 2008. However, according to marine mammal biochronology estimates, Basilosaurus should have appeared around 44 Mya. However, fossils do not generally record the first appearance of an organism. Thus, the most likely explanation is that Basilosaurus evolved roughly 7 My before the fossils we have found. The only way to solve this conundrum is to find more fossils, so get cracking.
Were you able to figure out what the mystery fossil this week was?
This is a vertebra, as I am sure most people could readily see. The two centra, the body of the vertebra, are flat to even a little concave, indicating an aquatic creature.
Here is a little more, showing pieces of the jaw.
Here is a picture by Karen Karr showing what the animal may have looked like when alive.
This is a Basilosaurus. The name means “king lizard”. It is an odd misnomer, though, because it is not a reptile at all. It is in fact a true whale, one of the first to have flippers rather than legs. Fossils of Basilosaurus have mostly been found in Alabama and a few other places in the southern United States, but the partial skeleton of one was found near Crowley’s Ridge in Arkansas.
An unexpected museum trip has presented itself to me, so this post will be short, but come back Monday for a more detailed discussion of Basilosaurus, the “bone crusher”.
I have a new mystery fossil for you this week. I thought I would put a new fossil off until next week, but considering that next week is Spring Break for many around here and that new, cool research has been published on this animal recently, I decided to go ahead and put it out there.
This is a drawing of the vertebra made by Sir Richard Owen, one of the greatest minds in paleontological taxonomy of the 19th century. The fossil had been identified as one thing, but Dr. Owen provided a thorough and convincing discussion of why that interpretation was wrong. The name given to it was rather humorously coincidental, considering what it turned out to be. It is difficult to identify isolated vertebrae, so I’ll give you another drawing of the same animal, but different parts.
This image is by the person who originally described the earlier vertebra, but also includes a few more pieces.
See if you can take the images, along with my clues, and figure out what this is. We’ll see if anyone can do better than the original descriptor.
I posted a new fossil last Monday. Were you able to figure it out?
You can find live versions of these animals covering rocks on most shores, such as these I found on the Pacific coast of Washington.
They will attach themselves onto anything, including other animals.
All of these pictures show barnacles, which will attach themselves to rocks, whales, boats, piers, and anything else they come into contact with during their free-swimming larval stage. The two most common barnacles one tends to find are either goose barnacles, like the ones shown on the rock, or acorn barnacles, like those shown on the whale. Goose barnacles are in the group called Pedunculata, so named because they have a peduncle, the stalk that attaches the shell to the underlying substrate (what they’re attached to, i.e. the rock, boat, whale, etc.). Acorn barnacles, on the other hand, are in the group called Sessilia, barnacles without stalks that attache their shell directly onto the substrate.
Barnacles are crustaceans, which are within the group Arthropoda. There seems to be some confusion about this on various websites, so I will explain a bit further. Arthropods include all segmented, invertebrate animals with an exoskeleton (hard exterior; literally, skeleton on the outside), and jointed legs. It is important to note here that while these are all characteristics shared by arthropods, they do not define Arthropoda. The group itself is defined by all of them sharing a common ancestor. The shared characteristics are simply clues to their evolutionary relationship. Arthropods include insects, arachnids (spiders, scorpions, and related animals), myriapods (millipedes and centipedes) and crustaceans. Arthropods also include trilobites.
Crustaceans are arthropods in which, among other things, the legs attached to each segment are biramous, meaning they split into two. Barnacles are, more specifically, crustaceans comprise the group Cirripeda, which means “curled foot” (while there is much argument about whether Cirripedia is a suborder, infraclass, or some other level of phylogenetic classification, these terms are are essentially meaningless and are really just holdovers of a time in which classifications were not built on evolutionary relationships, so I don’t use them; a proper term would be clade, but most people would not understand what that meant, so “group” it is). Most crustaceans are dioecious, meaning they have both males and females. Most barnacles though, are hermaphrodites, meaning that each individual is both male AND female at the same time. Much is often made of the fact that they have possibly the longest penis for their body size of any animal. This is necessitated by the fact that they are sessile, permanently attached. They can’t go walking around looking for a mate, so unless they are going to just release their sperm into the water and hope for the best (not normally very effective for animals using internal fertilization, although there are exceptions), they have to compensate. Since they are hermaphroditic, they could simply fertilize themselves, which occasionally happens, but not usually. Self-fertilization is the ultimate in being inbred, which is commonly known to have its problems (thus the reason inbred is often used as an insult).
Fossils of barnacles have been found in rocks dating back to the Cambrian Period over 500 million years ago, although they are not common until about 20 million years ago.Since that time, they have become very widespread and found throughout the world. Their first appearance is in the Burgess Shale, one of the best known fossil sites in the world. In Arkansas, they can be found in many of the Carboniferous aged limestones in the Ozark Mountains. Their shells are made of calcium carbonate, just like the limestone they are found in, as well as clams, with which barnacles are sometimes confused. The shells of barnacles are not hinged like clams, though. The shells of barnacles are also usually surrounded by additional material that anchors them to the rock, forming a roughly circular cone around the barnacle, which is not found in clams. It is not uncommon to find barnacles on clams, which shows a nice comparison of the two.