Famed Papers

Carnotaurus is a dinosaur that is relatively famous but has somehow escaped the eye of the blog until very recently. Reading this post that is self evident as this week is entirely dedicated to Carnotaurus. The amount of literature that has not been shown here about Carnotaurus is quite extensive. There are some articles, as there always are, that are more interesting or important to the study of an organism that we can single out. There are studies of the speed and general gait at which the dinosaur moved and the way in which the dinosaur used that speed to go about its daily life (its paleobiology). Additionally revealing important aspects of the life of Carnotaurus are studies about the animals head. The head is a unit of importance for feeding, mating, breathing, and basically every other aspect of being alive. We know a great deal about the dinosaur's braincase and the rest of the cranium including implications of cranial biomechanics. Probably one of the most charismatic papers discusses the forelimbs of the dinosaur. It is charismatic mostly because people are interested in the "funny looking" arms and they have been studied, described, and inferences have been made.

Cartoons and Serious Movies

Ranging from independent animated shorts like the simply titled Carnotaurus by Bennett Kim to serious feature length films, Carnotaurus is a film superstar.

In the majority of films Carnotaurus is depicted as a violent, and often, brainless carnivore with a single goal. That single goal tends to be the devouring of all life forms though that is not the case in the above Bennett Kim short. Dinosaur fandom being what it is, there are also more amateur productions such as this puppet feature by the so-called "Great Nate". We are not disparaging an amateur short like Nate's; his puppet fight is actually fairly well done and fun to watch. Most famously, Carnotaurus, was the feature villain in the 2000 animated Disney film Dinosaur. There were two animals that attempted to eat the main characters without talking or singing and dancing (contrary to many Disney movies) but they eventually were not able to eat the main characters. Sad for the villains.

Carnotaurus Facts

 

There are many ways to find information about a dinosaur as widely known as Carnotaurus. Those ways include normal fact sheets like those found at Enchanted Learning and About. The real value today is in allowing a 2nd grade student to teach his peers about a dinosaur that he likes. There is nothing quite like young enthusiasts teaching one another. Our older readers may be more interested in different videos that are a little more edited. There are plenty that are far too edited, featuring music that really does not seem to go along with the information or images that are presented in the video. We can actually follow the progression of videos through their complexity with the assumption that the video from the 2nd grade student is somewhere in the middle. The Dinosaur Feed presents a video that is all instrumental music and written facts displayed with an animated Carnotaurus. A more detailed, but somewhat editorial representation of facts is presented in this Paleo Profile video. Clocking in at nearly thirty minutes it is definitely the most detailed video.

The Weird Limbed Astronaut

©Brynn Metheney

Abelisaurids have very small arms that are even stranger than the tiny arms of tyrannosaurs. The group includes some very ornamented and very strangely armed but well known theropods including Majungasaurus and Carnotaurus. The "fleshy bull" deserves the bull part of its name as it possesses two significant and obvious bovine-like horns superior to its orbits. The fleshy part of its name refers to its diet; what else might teeth like those be used to eat? Known as a single species (C. sastrei Bonaparte 1985) from a single skeleton discovered in 1984 in Argentina, Carnotaurus is also unique for those strange and tiny arms. Shorter in proportion than even the arms of Tyrannosaurus, the arms of Carnotaurus are also rotated posteriorly at the shoulder so that the arms face the hips (to remember the direction I think of it anthropomorphic terms, like the dinosaur is putting its hands in its pockets). These hands are fairly vestigial and therefore largely useless to Carnotaurus. We will look at the horns, the hands, and the skin of Carnotaurus this week!

New Images, Maybe?

Araripesuchus is almost always shown in some sort of trotting posture. Rarely is the imagery of an Araripesuchus eating or sleeping or doing anything other than trotting. Instead of digging up some strange interpretations of Araripesuchus we should probably have a better idea of how large these animals were. The small crocodilians were not as large as their extant cousins and appear to be less frightening because of their diminutive size. The lessened scariness, based on size, is more than likely not a real thing for most people, though I am sure a few people would disagree. A small crocodilian of any kind trotting around can be quite scary.

Why Are You Famous?

The most well known of the species of Araripesuchus is A. wegeneri. Many quality specimens of this species exist and have been recovered including the block of a number of individuals interred together that was shared earlier in the week. Aside from that specimen there are a number of high quality skulls of A. wegeneri that allowed for dietary inferences to be detailed. The lower jaw is known only from the dentary and therefore does not add any information to the inferences about diet. The block, and other remains from other species, allowed for inferences about gait that painted the picture of a galloping terrestrial croc. This makes Araripesuchus look and walk much more like a mammal than a reptile.

From Sereno PC, Larsson HCE, 2008,
Cretaceous Crocodyliforms from the Sahara.

Where It Lives

Sixteen collections of Araripesuchus remains are recorded in the Fossilworks database online. Fossilworks does not have all of the collections of the fossils presented there meaning that there are more collections of the fossils not recorded online of course. The site allows one to generate timelines of occurrence and allows for maps to be generated. The plots are basic, but being able to see where Araripesuchus remains have been recovered shows us a great deal about the general distribution of the taxa before they went extinct. As we can see from the map and the timeline, the many species of Araripesuchus are widely distributed across geography and time. The majority of the recorded remains are spread across Africa during the Cenomanian age of the Late Cretaceous. A number of the remains represent book ends of their specific as they have been recovered from the Cenomanian and the Aptian age at the end of the Early Cretaceous. Proposed errors (i.e. missing fossils) are represented here as one species at least has been recovered from the Maastrichtian age which ended with the end of the Cretaceous or, as we usually refer to this time period, the K-T extinction. Assuming some error, Araripesuchus may have even lived, however briefly, into the Paleogene era as a genus headed toward extinction. Unfortunately Araripesuchus is considered to be a dead-end genus with no surviving descendants and is on the sister branch to extant crocodilians; this depends on the tree that one is consulting and if others have a more preferred assignment for Araripesuchus that they would like to share please do so!

Love for Crocodilians

Araripesuchus is a well loved group of animals, in part because there are a lot of species in the genus that are represented by a lot of remains. There are newly describe species within the genus like A. patagonicus that was first published in 2000 and A. buitreraensis described in 2005. There are also new remains that belong to previously known and described species. The most famous species was described in 1981, in German, and can still be found in the original form online. There are papers concerning every aspect of Araripesuchus' history beyond description. Among these the most common themes in paleontology are well represented as well, such as osteology and phylogeny. Conveniently these are both addressed in the same paper more than once. The most recent version of this discussion available online is from Turner in 2005. There may be newer discussions coming in the near future, but these will suffice until that time.

Lovely Sculpture

There are two videos that I am going to share today. One is a WizScience video; meaning that it is one of the computer readings of facts in video form.

The second video is, arguably, much cooler and more entertaining. This video shows a sculptor's interpretation of the soft tissues based on the cast skull of Araripesuchus. The artist is Tyler Keillor and the sculpture itself was made for the National Geographic special When Crocs Ate Dinosaurs. The other croc sculptures in the special were also created in the University of Chicago lab and, if one watches the special, you can see all of the different models.

Late Sunday Facts

Despite the level of interest in crocodile-like reptiles of the past and present, there are not a lot of fact pages online for Araripesuchus. Considering how interesting the animal is with its intriguing posture and heterodont teeth, it seems to have escaped the notice of many typical fossil fact pages. The only page that actually has a hosted fact file is About; this is probably because their writer Bob Strauss likes fossil animals as much as we do and has devoted a lot of time to putting together these fact pages.

Rule of Thumb

Generally as a rule I attempt to stay away from Crocodylomorpha not because I do not like the taxa (I actually like a lot of reptiles generally speaking) within the group but because the lab I work in has a lot of crocodilian projects ongoing and I therefore hear a lot about crocodilians on a regular basis. However, lately a rather interesting crocodylomorph caught my attention and, as it has been described since 1959, discussing this fossil genus is way overdue for people that love extinct animals but have not heard of the genus Araripesuchus. Araripesuchus consists of six accepted species: A. gomesii Price, 1959 (type), A. wegeneri Buffetaut, 1981, A. patagonicus Ortega et al., 2000, A. buitreraensis Pol and Apesteguia, 2005, A. tsangatsangana Turner, 2006, and A. rattoides Sereno and Larsson, 2009. Disregarding all discussion over validity and placement of these taxa in relation to one another and other crocodyliforms, the most interesting individiual taxon in the genus is the well known and much lauded A. wegeneri. Slabs of multiple individuals of the species and the well preserved skulls and limbs of the individuals reveal a lot of information about the species and in turn the genus. Using these specimens we know that the teeth of the animals were heterdont and imply a diet that was at least omnivorous and at most completely herbivorous. The limbs tell us that this was a terrestrial crocodyliform able to walk upright in a more mammalian posture, very unlike its extant relatives.

A. wegeneri, ©Todd Marshall

Sheer Power

Powerful giant birds have a tendency to be popular fossil animals. We can always assume that it is because the animal is a large frightening bird when we are discussing the so-called terror birds (or giant ducks like Gastornis). Andalgalornis is also popular because it is very well known and has been the subject of high profile and very informative biomechanical studies. The vignette we featured earlier from the Witmer lab, being a high profile lab, also extends the fame of the bird. Toys are non-descript, but there are at least one or two that are purported to represent Andalgalornis. Having a charismatic scientist in the lead of the studies helps also.

Frederico Degrange with Andalgalornis
Courtesy of the Museo de La Plata.

On Being Pecked to Death

Andalgalornis we have seen is a voracious predator but had a rather unorthodox style of procuring its food, in terms of giant carnivorous birds. Possessing an akinetic skull with a large dense beak, Andalgalornis was more likely to bring that beak down on prey like a heavy rock than it was to delicately grasp and kill prey. Each method of hunting has its benefits of course, but the blunt object method of smashing one's prey makes ambush slightly more useful and practical to an animal than chasing down food and attempting to crush it with one's head. This was certainly effective either way, as the giant head of Andalgalornis effectively sustained the genus for a number of years without significant alteration. Why an increasingly kinetic group of animals developed into forms without cranial kinesis is an intriguing question though.

(C)Renata Cunha

The Degrange and Tambussi Series

The Degrange and Tambussi series of papers on Phorusrhacid terror birds is not always those to authors or always in that order. The reason that the majority of papers are written by the two is that they are in the heart of terror bird country and they have an awful lot to say about the birds they have studied for so long. Those studies and results have turned out papers concerning all sorts of biomechanical analyses and results that tell us a great deal about the birds. Specifically, in the world of biomechanics, Degrange led a paper on an analysis of feeding habits and behaviors of Andalgalornis in 2010 that shed a lot of light on diet, cranial kinesis, and and the general capabilities of the terror birds of South America. In a further expansion of the dietary and behavioral capabilities of Andalgalornis Tambussi led a paper describing the flexibility of the neck of the bird. This paper includes one of my favorite behavioral inspired graphics that I have seen published. The inferred range of motion is very clearly detailed in this singular image and almost eliminates the need for the rest of the figures.

Birds in Motion

Yesterday I only shared a very short clip of Andalgalornis that was much more general and discussed terror birds as a group rather than focusing only on what we know of Andalgalornis. There are videos that discuss only this specific bird rather than drawing from many birds to generalize behavior or even anatomy. The generalizations are important, but seeing the actual actions or anatomy of any given taxon are important for understanding what makes this animal Andalgalornis. As a group (i.e. humans) one of our favorite things to see is another animal, especially fossil animals, biting things. That is certainly a part of the reason (not the whole reason I can assure everyone) that this video from the Witmer Lab was made and posted.

Biting and the actions that contribute to biting are intriguing to myself and many other people. Tracing the evolutionary history of these actions is certainly aided by viewing 3D animations of the animals that we are interested in. Here, for instance, we can see the movements, or lack of movements, in the skull of Andalgalornis. We see a similar system of akinesis in crocodilians but in extant birds there is a wide variety of kinetic capabilities including hypermobility. Seeing a bird built more like a crocodile than a parrot is quite unique.

Video Confusion

A lot of videos featuring "terror birds" are about any number of combined South American taxa. The fact pages that exist for South American taxa of giant birds get confused the same way sometimes. Discovery hosts a blanket clip about all terror birds that discusses them briefly. This is probably one of the better short generic clips that is available online. Unfortunately generic is best for today, as the more specific and single in its discussion of taxa that links are concerning Andalgalornis the more they are lacking in content.

A Killing Beak

Due to mentioning the giant bird Andalgalornis yesterday and not knowing a whole lot about that particular genus, I think it is very important that we discuss this South American terror bird in this week's posts. Andalgalornis steulleti is actually a lesser known genus of terror bird, in comparison to the other large bird fossils that have been recovered from the Pliocene rocks of the continent. This terror bird may not have been as terrible as its nearest relations, and may not even been a very fearsome predator compared to the other apex predators of the time.

©John Conway

Hunting, not Trunkless

©Andreas/Elperdido1965

The original intended image today was going to show Macrauchenia without a trunk. However, I did not hear from the illustrator and we do not put up paid artist's creations from their websites without permission, unlike much of the internet. Instead, we see the interaction of Macrauchenia as prey and a late common predator of South America, Smilodon fatalis. Smilodon emigrated across the isthmus of Panama late in the lifeline of litopternans and very late in the line of Macrauchenia itself. Prior to the introduction of Smilodon the major predators of Macrauchenia were the morphologically similar but unrelated Thhylacosmilus and giant birds like Andalgalornis. This foreign incursion of predators (bears and other cats in addition to S. fatalis), along with many other ecological factors, played their parts in the extinction of this great and singular ungulate of South America. South America, at the time, was much as Australia is now in terms of the isolation of the faunal assemblage. As with Australian isolation, the sudden introduction of exotic taxa to South America ended not only the lineages of herbivores like Macrauchenia but also carnivores like Thylacosmilus.

Famous Noses

Macrauchenia has been famous for a very long time and not entirely because the fossils were originally brought back to Europe by Darwin and the Beagle. The llama-esque body and trunk certainly added to the wonder and therefore fascination with the animal. The fascination with the animal has mostly caused Macrauchenia to become a computer game favorite. The fossil mammal has appeared in a number of zoo and Jurassic Park based games over the years and has even been recreated for Spore by users. The resemblance is acceptable at least. There are also a number of toys ranging from small plastic pieces to plush toys. That is the benefit of popularity I suppose, having a plush animal dedicated to the image of your genus. It is really for the benefit of people that love the animal more than anything of course; I think everyone understands that being popular with humanity is only good for extant animals in need of human intervention.

What About the Nose

Macrauchenia has a long flexible rostrum. The skeleton of the animal does not possess any fossilized structures that show this, however the evidence for the attachment of soft tissues corresponding to an elongated rostrum are visible on the cranium. the hypothesis that the marks indicated a trunk-like proboscis is comparable to that of saiga antelopes, which helped to develop the hypothesis and probably facilitated its general acceptance. The idea behind nostrils like that is unlike the reasons for elephant trunks and is related much more to keeping dust out of the respiratory tract of the animals. When an animal that probably avoided predators by running and kicking lives in a dusty environment it stands to reason it will have many adaptations to keeping foreign dust particles from clogging its lungs and stomach. These reasons make the saiga antelope parallelism make more sense. The diet of Macrauchenia also lends some credence to the likelihood of dust filtration rather than feeding being the primary reason for the appendage. The diet of Macrauchenia consisted of leaves and other small amounts of vegetation. However, some scientists think that the teeth of the animal were not suited to grasping leaves and assert that the trunk was therefore used for that purpose rather than primarily for filtering dust from the air.

©Olga Kobryn