Basilosaurus, the Bone Crushing Whale That Was Mistaken For a Lizard
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.
FEA analysis of a Basilosaurus skull. Snively et al. 2015. http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0118380
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.
Fossil Friday, A Whale of a Time
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”.
Mystery Monday, Not a Fish Story
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.
Crusty Crustaceans, Mystery Monday Revealed
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.
Encrusted North Pacific right whale
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.
Biramous vs. uniramous appendages. cnx.org
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.
Barnacles on a clam. Natural History Museum, Humboldt University. http://www2.humboldt.edu/
Mystery Monday
It’s been too long since I’ve done a Mystery Monday. so here is one for this week. Pardon me if it is a bit…crusty.
Check back at the end of the week to see the answer.
paleoaerie 