More Than Index Fossils

Ammonites do indeed make wonderful index fossils thanks to their abundance and long presence in the global fossil record. The name ammonite is one of the oldest in paleontology, with Pliny the Elder referring to these fossils as "Ammon's horns" (ammonis cornua). Ammon was an Egyptian god often portrayed with a ram's horn helmet. Pliny the Elder was a scholar who died when Vesuvius erupted near Pompeii in AD 79. The spiral shape of ammonites was not actually universal (the ammonite on my desk rescued from the shores of Lake Wilson, is an interesting spiral but a spiral nonetheless). Helical spirals, non-spiraled, and planispiraled individuals are all known from various fossil locations, genera, and species throughout the family. There is a rather nicely put together discussion on cephalopod shell shape page hosted by The Octopus News Magazine Online (as weird as that site sounds). This page answers questions about shell shape much better than I know how to alone without much more research. The fact that ammonites, typically depicted with simple and predictable shell patterns, were highly variable in shell morphology makes a lot of sense and seems to go somewhat without saying, but it is something not often thought about.

Ammonite Literature Is All Around Us

Ammonites are often used as markers of biozones and stratigraphic layers. They are not as often used to describe mineral deposits in formations or zones of interior seaways (okay, that is not entirely true, they are used for that purpose on a fairly regular basis, but I would not say often). Their diversity has been discussed (in Pondoland, South Africa interestingly enough) as well. Describing the fossil fauna of a shoreline is close to the heart of paleontology's roots in the United Kingdom, so that article has a little nostalgia to it. The articles I am most interested in today, though, are about evolution and anatomy. Anyone that knows me knows that that is to be expected. The article on evolution is available in its entirety online and discusses the history of a single Jurassic genus Kosmoceras. The genus encompasses more than 100 species known from European fossils and is considered to be a fast moving nektonic carnivore (meaning it ate other animals and that it swam). The article discussing anatomy is not free online but discusses buoyancy in extinct and in "the living ammonite." The abstract, the only part free online, does not mention what this living ammonite is, but it may be referencing the living nautilus, which is actually on a  different branch of the cephalopod family.

Ammonites In Motion

Ammonites are popular, as we know by now, and their inclusion in many videos and documentaries is to be expected. Their fossils are known globally, making them available for all kinds of documentaries and regional studies and their temporal is quite outstanding as well. There are also a lot of non-documentary videos of ammonites online, including a video of preparation of an ammonite specimen. There are also videos of the inside of an ammonite being cracked open and displayed giant ammonites in the world's museums. Possibly my favorite tribute-like video, however, also has shown up on the subject of ammonites. It is finally a tribute video done with some artistic thought and not just slapdash images and text over pretty awful music.

Finding Copious Fossils

Ammonites are well known to most fossil hunters in part thanks to the shells that were so well-preserved and copiously fossilized. Because they are so prevalent in the record there are facts everywhere online about ammonites from the BBC to National Geographic and even our most visited pages like Enchanted Learning and the NHM of London. There are additional pages such as that hosted by the British group behind the page Discovering Fossils, the home-schooling blog Kartwheels and the geology centered site Onegeology. I think with all of those links the rest of your day, my friends, ought to be wonderfully full of ammonite fun.

Unprecedented

I almost hate doing this, however, I am going to take a day off, in a way. I opened my list of blogs that I like to read, which I do before every entry into this blog, and I saw that Mark Witton has written about his own art gallery today. It just so happens that his entry today is about the part of his gallery devoted to ammonites (and extinct snails). Considering he has already done basically a complete parallel entry to the type of entry I would do on Saturdays, I am going to allow the link I provided to do my job today. A lot of people find it amazing that I have not taken a day off from writing all these years. Consider this my first.

Cephalopods You Say?

Finishing up April in style this week is going to be quite a bit of fun. Rather than discussing a single genus or species, this week is more about an entire subclass of Cephalopoda that we collectively call ammonites (officially Ammonoidea). A single species of ammonite could be discussed at any point, but looking at the evolutionary steps of these rather awesome looking fossils instead is going to be a lot more fun. Just to get people excited, check out the largest discovered ammonite, Parapuzosia seppenradensis, and this "miniscule" human for scale (diameter is 1.8 m): 

Gunnar Ries

Dunkleosteus Skull Armor Ocean Fish Dinosaur Figurines

You have to love mistranslations from Asian languages. The title I used today came from an eBay listing selling a small plastic skull of Dunkleosteus. Domestically there are cheaper figures available from Safari LTD. that can be picked up in Hobby Lobby (is there irony here?) and other stores selling those awesome, but expensive, little prehistoric figurines that I would love to have handfuls of. As mentioned previously, Dunkleosteus appears in multiple documentaries and is an overall popular animal. While it seems to have not shown up in Zoo Tycoon (I am a little bummed by this) it has made waves, pun intended, in that Jurassic Park Facebook game that has been referenced many times over here and appears in game like this:

Placoderm Heights

The placoderms appear in the fossil record during the Silurian, but the apex predator of the ocean that we call Dunkleosteus began to appear in the Late Devonian, near the decline and extinction of all of the placoderms. Lasting about 50 million years, the placoderms were fairly successful while they were around (not as successful as the 400 million year old lineage of sharks of course). The height of the evolution of jaw mechanics of placoderms is very evident in the articulated specimens of Dunkleosteus that have been discovered. The strength needed to open and close the jaw of the heavily armored skull alone was probably quite great. Add into the equation the amount of space available for additional muscle attachment, or simply strengthening the fewest required muscles, and the strength available for closing the massive jaws in a quick decisive snap is very impressive. Capable of up to 7400N of force along the "toothed" edge, the snap of that fish jaw could destroy most other fish in its sea and most likely many small man-made boats currently in the water these days. Part of the anatomy that helps this mechanism achieve the wide range of motion prior to the strong snapping of the jaws is the nuchal gap between the proper skull and thoracic shields.

Bite and Feed

The majority of papers on Dunkleosteus are focused on one of two things: either describing and referring new partial specimens or discussing bite force and feeding strategies. There are most likely other paper topics, but they are buried in the search results. In the interest of interesting topics, I have only chosen to share the two newest bite force papers to share. Mechanics and bite force modeling from 2007 are a good way to start. An update to that model and the feeding mechanics of Dunkleosteus appeared two years later in 2009. In a totally unrelated document there is mention of Dunkleosteus in a document by Rebecca Kagle discussing fish evolution.

Big Fish In The Sea

Perhaps there should not be, but there are a lot of Animal Planet and BBC clips featuring Dunkleosteus online. That is, of course, because there were so many of those clips in different documentaries aired by those networks. As a gigantic fish that is rather charismatic with the public, Dunkleosteus appears in a lot of popular outlets for both ratings and because of the charisma that it possesses. Ignoring the pseudo-science of most popularized fossil animals in documentaries, these are some pretty interesting clips regardless of the accuracy of the information.

Swimming and Scaring Kids

Davi Blight's illustration of Dunkleosteus attacking some children is pretty awesome, despite being pretty detrimental to the children in the illustration. There are number of fairly good information sites but today only About and Enchanted Learning are being referenced in that respect today. The Enchanted Learning page doubles as a coloring sheet online for Dunkleosteus as well. There is also a page available from a worksheet website, it appears as seen below:

Just Floating Around

Dunkleosteus has never been touted as a fast swimmer, in part because their armored head was heavy enough that the massive muscles it must have possessed in order to swim in the first place would have taken up all kinds of space in its body and not really left much room for speed swimming muscle. Because this was most likely a slow moving predator with a crushing bite ambush is a likely mode of predation. As such, most illustrations of Dunkleosteus show a lumbering fish with a powerful head and tiny eyes. Unfortunately most of these illustrations also show a fish with what appears to be a set of separated and specialized teeth. Dunkleosteus, however, did not possess teeth so much as bony ridges protruding from the edges of its armored and heavy skull. The skull's edge ridges are actually best thought of as nearly analogous to the beak of a turtle or raptorial bird. This beak could bite into other heavily armored placoderms, possibly including other Dunkleosteus (Dunkleostei?).

Ocean Voyages

In the continuing tradition of April, this week is another deviation from the norm. Rather than venturing back into the Mesozoic and staying on land, this week the plan is to slide off the beach and back in time even further, to the wild seas of the Late Devonian. 380 to 360 million years ago armored fish roamed the oceans of Earth. Many of these fish were still jawless animals that would barely be recognized as fish, but the earliest jawed fishes were clearly taking control of the seas by the Late Devonian. One set of the larger jawed fish, a truly charismatic mega-fish genus, was Dunkleosteus. Named for David Dunkle and the bony head that is the most commonly found fossil associated with the animal, Dunkleosteus was a hypercarnivorous fish capable of eating its way through the ocean with sharp bony ridges on its jaws and a powerful bite. As far as fish go this is a well known fossil and a rather well documented fossil at that. Who knew a fish would be so fun or interesting?

Popular Movie and Video Outlets

Desmatosuchus is a popular model in videos and games, old and new. It appears in dinosaur encyclopedias, despite not being a dinosaur. It also appears as an inspiration in Spore a few times. This one is the best and looks about as real as any Spore model has looked. However, the most ridiculous but entertaining and probably also the funniest Desmatosuchus model in all of video games is that found below:

Grouper or Land Animal?

Desmatosuchus is described as having a "pig-like" skull. Why would anyone (this image could be slightly altered post-DK publishing) change the head of this animal so that it looked not like a pig but like a fish of some kind? The body here is still anatomically correct but the skull of Desmatosuchus is not exactly accurate in this image. Points of the skull have been interpreted here to match the overall shape of the exhibited skull, but the fish-like aspect of it is very hard to reconcile after looking at the skull for an entire week and viewing it, and its more populous interpretations as very reptilian. What is the general consensus on this altered interpretation?

Papers Everywhere

The papers discussing Desmatosuchus are plenty and available everywhere. Rather than going into detail on every paper that I looked up and perused to share with everyone today it is much more prudent to throw out a solitary sentence blurb for each topic. The first paper discusses an endocranial cast molded from Desmatosuchus spurensis. Other papers address cranial anatomy and even a potential reanalysis of phylogeny. The identification of a new species, and another new species, of Desmatosuchus has also been discussed at length. These papers discuss Desmatosuchus finds in New Mexico and Texas respectively. The second I have found online free elsewhere, but only in French.

Saving Movies

There are a lot of videos out on the internet with Desmatosuchus as the main character or 3D model. Most of them I want to save for Thursday. Instead, and because none of those videos are related to documentaries, I am going to only post a video today that is a tribute video. It is okay, not the worst, but it is worth seeing today if, for no other reason, to look at as many images of Desmatosuchus as possible in a few minutes.

Plays Well With Others

The links available for children about Desmatosuchus are a little bit less populated than one would think, given that Desmatosuchus is a charismatic and interesting looking archosaur. The shoulder spikes of most fossils are typically enough to interest the most enthusiastic young paleontologists. However, lacking a high number of solid links, there is still a short blurb on a page calling itself Dinosaur Facts that sports a Tyrannosaurus in eyeglasses, About.com's Prehistoric Reptiles pages and, sharing a coloring sheet as well, Enchanted Learning. Other than looking like a happy turtle (it is mostly in the face) the Enchanted Learning coloring sheet is fairly well done.

Real Southwestern Animal Attitude

Museum of Natural History (Public Domain Release by Photographer)

Desmatosuchus from any angle looks like a pretty tough animal. The plating along the entire back of the animal from neck to tail is a defensive bulwark that likely made Desmatosuchus nearly impregnable from above. Like all half-armored animals, however, the underbelly was a great deal softer than this protective sheath of armor above was. To protect that underbelly, in addition to the strong dorsal plating, large spines protruded from the pectoral area of the dorsal plating. Spines like these are often depicted in popular outlets as offensive weapons wielded against predators hunting the animal possessing them. Pectoral spikes of this magnitude could be used as offensive weapons if the occasion warranted such action, but it is likely that Desmatosuchus used them as a deterrent effecting threat displays and swinging them, and its entire upper body as an effect, only as a last resort.

Allow Me To Continue

The past few weeks there have not been any dinosaurs here. There was a plesiosaur and then an early crocodilian and now, this week, there is an archosaur of wonderful proportions. A suggested herbivore with offensive/defensive structures on its shoulders (we know by now that this occurs over and over in the history of evolution) and significantly evident dorsal plating, this Aetosaur is unearthed fairly regularly in the central region of North America consisting of a swath of land from Arizona to Texas. The Late Triassic genus Desmatosuchus (Link Crocodile) was not a crocodile, but is certainly an archosaur with a commanding presence. The genus contains three recognized species: D. haplocerus (Cope, 1892), D. spurensis Case, 1921 (type), and D. smalli Parker, 2005.

Petrified Forest National Park

Strange Zoo Animals

Protosuchus makes a very important guest appearance in Zoo Tycoon 2. Modded in twice by users Zooasaurus and King Hoopla, the Protosuchus of this popular game uses the model textures of the Nile River Monitor as its base. This is a good base to use considering that Protosuchus, overall, has a more similar appearance in the game to the monitor than it does to the Nile Crocodile or the American Alligator models. Additionally, Cuba celebrated prehistoric animals with stamps. Protosuchus makes a very important cameo in the collection appearing, again, very water monitor-like. Popular culture does not really peak its head into the business of Protosuchus after this stamp and these modded models. However, this has been a pretty good week for information on this early crocodilian.

What Else Can You Do?

The majority of reports and discussions about Protosuchus appear to have a general consensus about the fact that the tail of this fossil appears to have many, and large, muscle attachments. The speculation about this suite of muscle attachments and the general shape of the tail has, in some circles of debate, given rise to the hypothesis that use of the tail as the main source of power in swimming for crocodilians originated in this genus. Locomotion via horizontal power strokes of the tail is a very visible character of extant crocodilians. Thinking of this high strutting cursorial predator as a strong swimmer is not beyond the scope of its anatomy, but combined threats by Protosuchus on land and in the water makes this animal far deadlier and a nearly universal predator. It is too bad there are not many images of it swimming though. John Sibbick made a composite of many different crocodilians that has Protosuchus near the water. The image here is by the late Zdenek Burian and depicts a shore dwelling Protosuchus looking rather mean-spirited, as 1960's dinosaurs and other fossil creatures tended to do.

Ancestral Writings

The source material, when available, is always fun to read. It is usually informative as well regardless of how accurate the initial description is (the initial Plesiosaurus descriptions equated the animal to sea turtles in many ways). Colbert and Mook's initial 1951 description of Protosuchus richardsoni is both informative and well written. It is also available online. That is pretty nice in these days of online journal access restrictions. The cost of articles can be exorbitant at times, but this does not mean that an expensive article is not worth reading. Sometimes, like this article discussing Protosuchus and the origin of phytosaurs and crocodiles, finding an interlibrary loan or copy of the journal in the library is worth the trouble. Alternatively it may be worth the cost as well if one could afford it.

Nowhere To Walk

Protosuchus missed a lot of the before-the-dinosaurs documentaries associated with the Walking With series. There is very little video evidence of Protosuchus models in use in any situation actually. That which does exist is a somewhat loose interpretation of Protosuchus walking through an illustrated forest. Considering the limbs of Protosuchus it is not too unrealistic to compare the high walk of crocodiles with this animal. Be aware, though, that this is in no way completely and 100% analogous. We do not want to start a fight about how they are not crocodiles and are only vaguely similar.

When Not As Cool As Dinosaurs

A lot of the animals that are discussed in these week-long discussions are not exactly as awesome as dinosaurs in the eyes of the public. Then there are some, like Protosuchus, that are just simply not as popular as the ultra popular dinosaurs. That leads to a lot fewer public outlets for non-dinosaur fossil animals, as we have seen in the past. Protosuchus has a good About page that covers the basics of the animal, which is what we need to educate young students. Unfortunately, it is not enough to fully educate the young paleontologist and the normal outlets that would supplement this easier reading material are not available. However, parents (and other adult paleo-educators) can use Josep Zacarias' illustration as a coloring sheet and as model to discuss what the animal looked like and how it may have moved and interacted with its environment and the animals around it.

Rows of Plates

From Colbert and Mook 1951

Protosuchus' skeleton demonstrates the mentioned double row of bony plates extremely well. The long almost gracile legs, for a crocodilian, are also clearly evident. The long back legs are well articulated as is the hip joint. The columnar legs and this hip joint belong to an animal that was somewhat speedy and capable of generating adequate power to produce that speed. The shoulder attachments and forelimbs also are clearly visible, as are the muscle attachments that indicate their ability to power that end of the animal. The bony plates along the back were probably the most interesting anatomical structures of the skeleton, when looking at it from a distance as we are doing here. It is evident from the inclusion of three unique species from diverse locations that these bony plates, and the other anatomical adaptations, were successful adaptations benefiting the animal. The strength of this armor plating, but also its flexibility, allowed for Protosuchus to be an aggressive predator that was also at least partially protected from other animals, including members of its own species.

Posted Protosuchus

The first crocodile is one of the earliest of the Crocodylomorphs of the early Jurassic. Shorter and lighter than most extant crocodilians, the 1 meter, 40 kilogram Protosuchus was a genus consisting of 3 species. The species all possess short skulls with broad bases allowing for expansive muscle attachments. The gape and force of the jaws was increased with these adaptations of the skull. Additionally, the teeth resembled modern relatives and the back even possessed similar dermal scutes and ridges. The back legs were longer than the front legs, and the tail shows signs of having muscle attachment sites that indicate strengthening of the tail muscles that would become more important as crocodilians became more adapted to aquatic lifestyles.

©Nobu Tamura

Books and Jurassic Park

Trinacromerum is the star of many written works on ancient marine reptiles. It is also a star in the previously mentioned Facebook game Jurassic Park Builder. It is the subject of a rather nice piece by Julius Csotonyi; notice the small crocodyliform in the bottom part of the image. I wish there was more to popularize this animal, however, we have to deal with the little amount that we have at the moment. If someone makes a stuffed knitted Trinacromerum, then we know that it is truly famous and popular. Until then, see how you stack up against Trinacromerum.

Late Cretaceous Seas

Trinacromerum is a pretty average polycotylid with a pretty average, but robust and stout, streamlined body. However, its long flippers and streamlined body allowed Trinacromerum to achieve higher speeds than many other plesiosaurs. These higher speeds, agility, and the long wide head of the animal potentially allowed for predation of faster fish than those taken as prey by larger slower plesiosaurs. Unfortunately no quality images of high speed chases featuring Trinacromerum are online, so I have none to share today.

Some Old Papers

Today it would be very easy to say "wait a week or so and you can read my thesis" but it is not expressly about Trinacromerum and would not fit the criteria of news about a specific taxa. Instead, for Trinacromerum it is actually quite highly recommended to go back to the earliest records and the most extensive descriptions are from the late 19th Century and early 20th Century. My solid recommendations are S. W. Williston's 1908 edition of North American Plesiosaurs: Trinacromerum and the 1888 edition of The American Geologist featuring Cragin's Preliminary Description Of A New Or Little Known Saurian From The Benton Of Kansas. Read and enjoy. I certainly did!