STL Science Center

STL Science Center

29 November 2017

The Anthracotheriidae

Type specimen from Macdonald 1956
Anthracotheriidae were hippo-like ungulates found globally that are related to the hippopatomuses and whales. The earliest specimens originated in Asia and some made it to North America, but they are best known and were most prolific in Africa and Europe. One of the species that has been found in North America has a Sioux name, again bestowed upon it by J. R. Macdonald: Kukusepasutanka schultzi Macdonald 1956. The name means "Big hog nose" and Macdonald, for this genus, does not include a pronunciation guide; though he does thank Mrs. Lulu Standing Elk for help in translating the name accurately. The name refers to, in part, to the large tubular snout that the animal possessed. The cranium and an incomplete set of teeth make up the type specimen, seen here.

28 November 2017

The Macdonald Primate

Type material from Macdonald 1963
This week is rapidly turning into a week dedicated to not only the Sioux language and its influence on paleontology, but also J. R. Macdonald. We have done weeks like that in the past, but it is not necessarily what we are doing this week; it just happens that the animals we are describing this week were named by Macdonald. Today we are discussing one of the only fossil primates known from North America; this excludes primates of Central America. Ekgmowechashala, meaning "Little cat man" in Sioux, is a genus of 5 lb lemur-like primates standing approximatel one foot tall. Macdonald's etymology guide in the description shows that the pronounciationis  Igg-uh-moo Wee-chah-shah-lah. Living during the Late Oligocene and Early Miocene, Ekgmowechashala consisted of two species, E. philotau Macdonald, 1963 and E. zancanellai Samuels, et al. 2015. The genus has been contentious since the type species was described by Macdonald in 1963, but a recent phylogenetic study by Ni, et al. (2016) solidified the phlyogenetic position of Ekgmowechashala as a member of the group Adapiformes, the extinct relatives of lemurs and other basal primates. Adapiformes are some of the most basal members of the primate family tree. The teeth of Ekgmowechashala represent the majority of the originally known material and allowed for inferences of diet. The diet of Ekgmowechashala is thought to have consisted of soft fruits from the warm forests of the Oligocene-Miocene.

Warm forests are not the typical scene for the Rocky Mountains, but during the time of Ekgmowechashala the mountains of western North America were warmer than they are now. The teeth leading to this inference make up a large majority of the fossil material that has been recovered. Teeth have been recovered from the 1960's to the present day from Shannon Count, South Dakota (type material), Pine Ridge and Oglala Sioux reservations in South Dakota, Oregon, Nebraska, and Texas. Ekgmowechashala zancanellai material comes from Oregon exclusively at the moment whereas the type species consists of material from the remaining localities.

27 November 2017

Macdonald's Dog

As we mentioned on Saturday, J. R. Macdonald named a large number of mammals from the Oligocene using the Sioux language prominently in his papers. One of these mammals is the hesperocyonid canine Sunkahetanka geringensis Barbour and Schultz, 1935. The name means "Large-toothed Dog" though the Sioux words are actually constructed in reverse order here. The specific epithet refers to the formation from which the specimen originated; the Gering Fromation of Nebraska. Macdonald also provided a pronunciation guide for Sunkahetanka: Sung-kah Hee Tahn-kah. The teeth of this hesperocyonid are actually enormous compared to many other contemporary canids and others within the family tree. The skull is short and wide with robust zygomatic arches and what Macdonald describes as a massive mandible. The massive teeth, jaws, and well built skull lead Macdonald and others to hypothesize the diet of Sunkahetanka to have consisted of anything it was capable of catching or finding. This includes scavenging bones similarly to the manner in which hyenas do now. This is facilitated, of course, by the enormous teeth and the massively built skull in which they are operated. Unlike last week's Leptocyon, Sunkahetanka looked much more like a wolf or a large dog as we now think of them. At a weight estimated (by Legendre and Roth 1988) using tooth size of between 12.8 kg (28 lb) and 13.8 kg (30 lb), Sunkahetanka was about the size of a large beagle (I prefer thinking of basenjis; points to people that know them). This is considerably smaller than a wolf, but imagine a beagle sized animal that could crack and break bones.
©Ghedoghedo via Wikicommons

26 November 2017

Oldest Sioux Animals

The oldest fossil animals with Sioux inspired names are technically the variously assigned Brontosaurus or Apatosaurus yahnahpin. A yahnahpin is a breastplate and graced the sauropod's name in reference to the well preserved gastralia, or belly ribs, that were recovered in the fossil remains. These remains date from the Jurassic of Wyoming and the information known about the animal and shared online is mostly in the domain of message boards and academic squabbles. The best description of the material comes from the Wyoming Geological Association Field Conference of 1994, which is, unfortunately, not available online.

Another dinosaur that prominently features the Sioux language is Dakotadon lakotaensis. The name refers to a Sioux tribe, the Dakota, and the Lakota Formation of South Dakota. The name of the formation, of course, refers to another Sioux tribe, the Lakota. Originally named Iguanodon lakotaensis in 1989 by Weishampel and Bjork, the species was reassigned to a new genus as Dakotadon by Paul in 2008. Still an iguanodontid, Dakotadon is a basal member of its family and has been suggested, but not yet shown to be, a synonym for another basal iguanodontid, I. bernissartensis. The arguments continue over the phylogenetic position of the dinosaur, but the basal position is not very contentious. The fossil is important to the fauna of North America as well as being important as a representation of the Sioux language because it represents the only universally accepted iguanodontid from the continent.

25 November 2017

Named Through Sioux

The languages of the Sioux Nation have been sampled and featured extensively in North American paleontology. Examples span from dinosaurs such as Apatosaurus yahnahpin Filla, et al. 1994 (currently assigned to Brontosaurus), a rare North American primate, Ekgmowechashala philotau Macdonald 1963, and the anthracothere Kukusepasutanka schultzi Macdonald 1956. Mammals constitute a large portion of the Sioux names in paleontology, but most of those are actually due to the works of James Reid Macdonald (read his 2004 obituary here) who prolifically described and named mammals from the Miocene and Oligocene from Oregon to the Dakotas using the Sioux language. The immense number of specimens bearing Sioux names means that we can easily pick any single animal to celebrate the contributions of the language to paleontology, but I think we can all agree that this would not show that contribution the proper justice it deserves. Instead, for the first time ever, we will discuss a different animal every day this week.

24 November 2017

Holiday Over

Back from the holiday (in the United States), we are going to end this canid filled week by trying to find a good image of Leptocyon. There are not many illustrations of Leptocyon. There are no well established reasons that there should be fewer Leptocyon illustrations than there are online, in books and magazines, or in museums. Most of the illustrations that are online that are labelled Leptocyon look like animals that are somewhere between cats and dogs in appearance. Many other interpretations make Leptocyon look like coyote or a fox. The image below, however, shows Roger Witter's interpretation of Leptocyon mollis, a species named in 1906 by Merriam but not officially listed in the genus, from the John Day Assemblage of Oregon. This interpretation looks more like a wolverine than it does a dog or a cat. It is an interesting interpretation of a very dog-like skull.
©Roger Witter

21 November 2017

Papers on Dogs

Leptocyon was not much larger than a dachshund, with an estimated weight of approximately 3.26 kg (7.2 lb). The description of many websites stops after mentioning that fact and that its slender jaws and gracile body gave Leptocyon the appearance of a small fox. These are not the only characteristic attributable to Leptocyon however. The initial description and naming of the material is attributed William Diller Matthew in 1918 (see page 7 of the PDF). Matthew noticed the slender mandibles immediately and described the teeth and their morphology in detail. Matthew also states that the morphology of Leptocyon appears to make its inclusion as the ancestor to not only canids but also foxes, unlike some previous authors must have declared. As we have seen throughout the week up to now, most of the sources of information about Leptocyon are sources that describe the entire evolution of the canid family, not just descriptive works of the morphology or paleobiology of Leptocyon. Wang, et al. 2004 is a fairly well-known and (I have not checked into this recently) definitive description of the phylogenetic evolutionary ecology of all canids. It is a book chapter, but for the reader curious about Leptocyon or the dog enthusiast curious about where their pets came from, this is a good read with a lot of detail and a fair amount of technical elements to it.

19 November 2017

All Your Fox-like Facts

Leptocyon looked something like a fox, regardless of the species. There are no videos that show this fox-like species as scientific illustrations. There are a few videos that briefly mention Leptocyon, but the only one that is really worth watching is this video on the evolutionary history of canids; the mention is brief but the entire history of canids is worth watching on its own. ThoughtCo (previously is really the only dedicated website with detailed information on Leptocyon and the site hosts two webpages concerning the animal: one dedicated to the evolution of canids and a second with quick facts and images (and interpretations) of canids throughout history (Leptocyon is #12).

18 November 2017

Furry Friends and Megasymbol

Appearing in the Oligocene and peppering the fossil record into the Miocene (from approximately 25.8 - 10.3 million years ago), Leptocyon is a genus of small bodied canids endemic to North America. These canids, consisting of three species, L. gregorii, L. vafer, and L. vulpinus, represent the origins of the canine family tree as it diverged away from the feliniform carnivorans and the other caniforms. The caniforms include not only dogs, foxes, and wolves but also bears, seals and sea lions, and mustelids. For the approximately 15 million years of the fossil record that Leptocyon appears, it is the only canid that appears. Around the time that Leptocyon disappears from the fossil record an explosive diversification of foxes, wolves, coyotes, and wild dog begin to appear in the fossil record.

In the vein of an animal of importance to the native peoples of this continent, this precursor to so many different types of canines is the grandfather genus to many very impactful animals on the mythos and lore of those peoples. Wolves and coyotes are extremely important to many cultures of North America. Foxes, though, are just as important but not as prominently featured in Native American cultures as the other cultures. All of these animals star in other cultures globally (I wrote an honors thesis in undergrad on foxes in Japanese Shinto, for example) as well. Our discussion this week will elaborate on the origins of all of these animals from their humble beginnings in North America. The story of Leptocyon is the story of some of our favorite pets as much as it is the story of animals important to the native peoples of North America.

17 November 2017

Finding a Unique Illustration

©Christopher DiPiazza
Almost every illustration that comes up in a search for Argentavis depicts a bird landing or taking off with the few exceptions that show the animal simply stretching its wings one way or another; the bird on a dead animal trying to scare off scavengers is a very common theme. The large wingspan and body of the bird are central to the identity of the fossil, so these themes make sense. One of the most charismatic images that I have found does incorporate the wide wingspan of Argentavis, but it also has a piece of its last meal in its beak. Although almost all of the illustrations of Argentavis already looked fairly fierce, this interpretation, possibly because it was drawn head on, looks more intimidating and angry. As we typically see in Christopher DiPiazza's work, the tones and colors are soft and very pastel-like. Despite this, the details are sharp and the pose is dynamic. Additionally, read the linked blog post by the artist. He has hit a lot of the same points we have hit this week, but his insights into his art shine through in his writing, and they are worth reading about while admiring the work.

15 November 2017

Massive Eggs and Wings

The egg of Argentavis is estimated to weigh approximately 1 kg and it has been hypothesized that they were laid once every two years. At 1 kg the egg is only a little smaller than that of the Common Ostrich, but Argentavis' egg laying cycles were similar to gulls and albatrosses rather than animals that reproduce annually. It has been hypothesized that the incubation cycle of these eggs was such that the birds were forced to incubate over winter. Chicks were thought to have lived with the parents for approximately 16 months before permanently leaving the nest. By contrast, the Wandering Albatross is the longest fledging extant bird, with the young bird remaining in the nest for 278 days. As with many extant gulls and other seabirds, Argentavis is thought to have then had a sexually dormant period, not achieving maturity until approximately 12 years old; Royal and Wandering Albatrosses reach maturity between 6 and 10 years. The fact that Argentavis was so large means that most predation and death probably occurred either in the nest or by from accidents and old age. How old Argentavis lived to be naturally is up for debate, but we know that a lot of extant birds, large and small, live extremely long lives today. The Kakapo of New Zealand is thought to live well over 100 years; with so few in the wild and their histories not being cataloged until recently, however, the oldest known member was approximately 80 at his death. Other parrots have been known to live into their 80's in captivity and individual Royal Albatrosses have been documented at 58 years old in the wild. The largest flying birds, Great Bustards, live to approximately 10 years, whereas the oldest eagles have been recorded at between 30 and 40 years old (depending on the species). All of these numbers make pinpointing the ages of large birds, especially those that can fly, difficult. Argentavis could have lived a lifespan like that of a large eagle, meaning that it could have lived up to 40 years. That means that an adult pair, laying one egg every two years, could have possibly reared 14 young during their lifespan. Not only a large bird, Argentavis may have had a rather sizeable population at one time or another because of their long lives, large size, and dedication to a single offspring.

14 November 2017

Flying A Great Bird

One of the questions that appears time and again with giant flying animals is "How do they get off the ground and how do they stay off the ground?" Because that is a popular theme with large flying animals, the first hit in a paper search for Argentavis is Chaterjee, et al. 2007: The aerodynamics of Argentavis, the world's largest flying bird from the Miocene of Argentina. The author's conclusions are centered around the hypothesized aspect ratio of the wing and estimated body weight. These parameters lead them to conclude that Argentavis was most likely similar to extant vultures and large condors in that it was probably not capable of sustained powered flight, instead choosing to use thermal soaring as its preferred method of staying airborne. Intermittent powered flapping would have been used as it is by these extant analogues as a secondary anti-stall measure but not as a power source for extended flight. This paper builds off of the new data and goes into more computer simulation than Vizcaino and and Farina1999, which initially tackled the problems of Argentavis flight without computer simulations, instead, it appears, relying on estimates of body size and inferred wing shape and comparing these with extant animals and known aerodynamic principals; the full text is not available anywhere online and what I have inferred comes from the abstract found here. The final article I will mention today addresses ecology (and reproduction). Palmqvist and Vizcaino 2003 details ranges, needed amounts of food, airspeeds, and clutch size to determine the ecological impacts and roles of Argentavis. Instead of spoiling this paper by writing in those facts, as I did above to a slight degree, I am going to simply encourage everyone to read and discover the paper's findings for themselves here. I find the paper to be interesting and find myself wondering if anyone would refute any of these findings; I have yet to find a paper that does so (I admit my search is short right now though).

13 November 2017

Quick Facts

Above are some quick facts about Argentavis presented in video form. This very quick video does not reveal much that we will not get into ourselves. There are some cryptozoology documentaries on the internet also; whereas these are strangely interesting, they are not necessarily historically accurate or important to watch in order to gain more knowledge about the bird. Aside from these kinds of videos and the short video shared here, most of the videos that show up with Argentavis as a keyword are related to video games.

11 November 2017

Birds and Thunder

©Nobu Tamura
In general, native peoples of both South and North America have a number of legends and mythologies describing giant flying animals. From the Thunder Bird (a generic term that encompasses a wide range of mythological figures from different tribes) to Tah-tah-kle'-ah (a race of cave dwelling "owl women" from Yakama lore) to Achiyalatopa (from Zuni folklore), native peoples have been influenced by the idea of giant birds flying across the sky. In some instances these are giant bird-men/women but regardless of the anthropomorphizing of giant birds, these legends could have been influenced by real living animals. One such giant flying bird has been discussed here before (See Pelagornis). Another giant bird, more often associated with the southern hemisphere but by no means entirely limited to that hemisphere, was Argentavis magnificens (Magnificent Argentinian/Silver Bird). Flying through the skies during the Late Miocene and known, at present at least, from only Argentina, Argentavis possessed a wingspan of approximately 6.07 m (19.9 ft) and 72 kg (159 lb) by the greatest estimates. This makes it the second largest flying bird ever known behind Pelagornis. In comparison to living birds, the largest wingspan is that of the Wandering Albatross at 3.65 m (12 ft) and the heaviest (sustained) flyer is the Kori Bustard at 11.4 kg (25.1 lb). At this size Argentavis must have flown much like Pelagornis; flapping powered flight may have gotten it airborne but thermal soaring would have been the most likely model for sustained flight.

10 November 2017

Iconic Images

Probably the best Bison latifrons image I have seen this past week (before looking tonight as I write this sentence) is that of Davide Bonadonna that I shared on the Facebook version of this page. Rather than paste it in here without contacting Davide, I will link his gallery where he hosts his illustrations. A large majority of bison illustrations are not as exciting as Bonadonna's or include modern bison being attacked by wolves (if not a hunting scene with Native Americans. In the "non-action but still fun" category one of the best images I have seen this week is Christopher DiPiazza's B. latifrons at the watering hole. I think I like this image more because it shows an interesting level of curiosity not often associated with the big brutish bison and also because it has softer tones that contrast with a lot of the images we have looked at over the course of the week. Please feel free to share more illustrations that you like in the comments.

09 November 2017

Documentaries Everywhere

I was considering what to do about the popular culture references today. There are a number of things that I could do, obviously, as we know that modern bison are something that the public is well aware of. I think, instead, that we should look at some documentaries which discuss the historical significance of bison as well as their current conservation status and situation. Though these documentaries do not specifically discuss the three species we have been discussing this week, the life history of extant bison is similar to that of their extinct family members and is therefore informative. The National Park Service covers a little history and their extant modern herds in the linked page. This second video, from the Kratt brothers (in their Wild Kratts series), may be a cartoon (mostly) but its appeal to the younger audience is not to be overlooked. The information that is given out in this video is useful, accurate, and does indeed go beyond it being a children's cartoon. There are also somewhat more traditional documentaries such as this "Fabulous Animals" show and Facing the Storm: the Story of the American Bison (which is movie length). I know that we are well away from extinct animals with these shows, but being able to see a modern descendant and how it lived on quite similar ground (ignoring the members of B. latifrons and B. antiquus found along the eastern seaboard) is important to trying to reconstruct the lives of the extinct animals.

07 November 2017

Buffalo (Bison) Papers

Many descriptive papers have been published for Bison latifrons and B. antiquus. Bison occidentalis, however, does not have as many description papers published concerning its remains. There could be any number of reasons for this, but after looking over papers and fossil locations as well as the Paleobiology Database (PbDb: the major reason for this might be that some sources, at least, consider B. occidentalis to be a subjective synonym for B. antiquus. This means that the type of the two species is not a shared fossil and that the debate on their synonymy is open. Unresolved taxonomy like this can lead to some sources like the PbDbnot acknowledging the species as unique while others at the same time do still consider it a unique species, such as Hawley, et al. 2013 which describes the occurrence of B. occidentalis fossils throughout the Wisconsin and Minnesota.

The range of these species has always been an interesting topic for research descriptions and has proved fruitful as well. Representative ranges can be hypothesized for each with articles detailing discovery sites and discussing their significance to the ranges. For instance, B. latifrons has been described in South Dakota (see above), Kansas, Nebraska, and even Georgia. Bison antiquus has been described from remains found in Florida, Alberta, Canada (with a mention of B. occidentalis as well), Washington, and Southern California. Bison occidentalis has been described from sites in Iowa, Alberta, Canada, Texas, and California.

A lot of papers go beyond simple description of these three taxa. A large number of papers published about these papers are from archaeological journals, which is highly logical. Bison, regardless of species, have been some of, and eventually the absolute largest, herbivorous North American mammals encountered by humans. Their use as food, clothing, crafting sources, weapons, and fuel for fires is well documented in North American historical sources and from archaeological digs (as a reference read Agogino and Frankforter 1960 and Wheat 1967). Associations of bison with archaeology is to be expected and some of the articles detail not only interesting aspects of the animal's life histories (refer to this article on butchering and taphonomy as an example) but also a great deal about their capability to endure hardships both human inflicted and natural. These include descriptions of diseases that have been studied in B. antiquus as well the effects of hunting in B. occidentalis.

There are a lot of articles here today, but I cannot apologize for the rich literary record of bison research; nor would I want to if I was asked to honestly.

05 November 2017

Three Sets of Information

My plan for this week is to, unlike other weeks, treat the three endemic species of North American bison as individual animals rather than discussing the genus as a single entity and pulling out interesting information regarding individual species. The reason we are approaching the information this way is because, other than overlap zones in the history of the genus, the three species are radically different morphologically and warrant their own attention as parts of the whole evolutionary history of the genus Bison. For a quick overview of fossil bison without reading the following paragraphs a short stop in the digital library of the San Diego Zoo may be all you need. To start, we will look at the three species in order of their history, meaning that B. latifrons is our first stop.

The artist Roman Uchytel is typically mentioned when we look at his illstrations and interpretations of paleofauna. Today, however, his art coincides includes a concise history of B. latifrons. His illustration, of course, is a nice addition to the information, but not the primary reason to follow this link to his website. Not to be outdone by the display shared yesterday from North Dakota, other states also have information on B. latifrons that were unearthed within their borders. Speaking to the range of the animal, there are also finds from San Diego and as far as Florida (B. antiquus is also mentioned on this site, attesting to its range as well) that are mentioned. This site shows and mentions the sale of fossils but such practices are not endorsed or encouraged here.

The intermediate species, B. occidentalis, also has space and information dedicated to it on Roman Uchytel's site. Again, his illustration is a positive bonus to the information provided. Most of the information is taken from Wikipedia, but that is not too important here. Bison occidentalis is not as well known as B. latifrons or B. antiquus, and most of the information online about this species is actually in the form of descriptive papers, which we will save for Tuesday.

As with the previous two species, B. antiquus has been illustrated by Roman Uchytel and he has paraphrased information from Wikipedia. Placing the three side by side is informative and interesting in its own right actually, so it might be worth the momentary effort. Bison antiquus has a few more resources online. This is partially due to its more recent history and of course to those resources being studied a little more in depth than the other fossil species. In addition to Florida and the western part of the North America, there are specimens of B. antiquus known from Ontario, Canada, Texas, and Florida.

04 November 2017

November in North America

It is possible that if you are from North America you are aware of the trend in the last 20 or so years to take back holidays celebrating European domination of the native populations of this continent. I remember personally seeing protests at Thanksgiving parades in Plymouth and more and more states appear to be dropping Columbus Day as an official holiday or at least renaming it. Given that the United States of America observes a Thanksgiving event in this month, the same holiday as the protests just mentioned for anyone not following U. S. holidays, I thought it might be interesting to look at the fossil history of some of the groups of animals that have been of special importance to the native cultures that once spread across this continent and that we have, to a significant degree, lost over the past 400 years. This is a look into how the animals that became important to the peoples of North America became the animals that they are now and what their fossil history, regardless of how recent those are, reveals about their evolution. I know these are not dinosaurs, but life on Earth is complex and filled with a lot more than dinosaurs, so hold on for the ride, or take a break and come back to us in December. The first animal that we will look at this month is the America Bison.

The American Bison (Bison bison) has a long history that, like a significant number of animals, starts on another continent; there is an extant European Bison (Bison bonasus) distantly related to and far more rare than the American Bison. The fossils we are going to discuss are the members of the family that arrived or thrived in North America prior to the appearance of what we would recognizably call the American Bison. Three extinct species of the genus Bison were endemic to North America prior to the appearance of Bison bison, the American Bison, in the fossil record. These species were, in order, B. latifrons, B. occidentalis, and B. antiquus. They range from approximately 240,000 years ago when B. latifrons is thought to have initially crossed the Bering Land Bridge into North America to approximately 5,000 years ago when B. antiquus appears to have gone extinct. The three species are not identical and B. latifrons is actually quite impressive, measuring in at 2.5 meters (8.2 ft) and estimated to have tipped the scales at 2,000 kilograms (4,400 lb); that is almost as tall as a modern Asian Elephant. The horns of B. latifrons measured approximately 213 centimeters (84 in) from one tip to the other. Bison bison measures in with horns approximately 66 centimeters (26 in) from tip to tip. Bison occidentalis is less well-known, but it is smaller than B. latifrons and its horns, also much smaller, pointed toward the rear of its skull, rather than the front. Bison antiquus was nearly as tall at 2.27 m (7.5 ft) but much lighter at 1,588 kg (3500 lb) and with horns noticeably smaller, though pointing forward, that measured approximately 1 m (3 ft) wide.
Photo from North Dakota Department of Mineral Resources. B. latifrons exhibit at the North Dakota Heritage Center

03 November 2017

All The Pictures

What is the absolute best illustration, scientific image, line drawing, or photograph of a fossil of Helicoprion? If you cannot think of an answer, you are not alone. Is it this image of the estimated size of Helicoprion? It might be this image of all of the hypothesized Helicoprion morphologies (I saved it for my own visual delight).  The Mary Parrish illustration shared on Wednesday is up on the list of good illustrations for most people. There are a number of poor illustrations; we will not share those here today. My personal favorite, as we always see here on Fridays (feel free to share your own of course, but I write it, I choose it typically). The thing this week is that I do not really have a favorite. Some of the best illustrations are outdated and terribly wrong, despite their wonderful appearance. Mary Parrish's interpretation is wonderful, and Nobu Tamura's is as well (see Saturday's image). The image for today, rather than being a favored illustration, is one of my favorite photographs of a Helicoprion fossil. This tooth whorl is immense in appearance and its rolling form is somewhat mesmerizing. I almost cannot stop looking at it honestly.

01 November 2017

Other Anatomy

The papers yesterday described the anatomy of Helicoprion's tooth whorl and as such, though we usually pick the most interesting anatomy and describe it on Wednesdays, we will have to discuss something slightly different this Wednesday. The topic for today still has to do with the tooth whorl; it is actually almost impossible not to discuss the only two materials that are known from Helicoprion  fossils (crushed cartilage and dental remains). Two hundred ninety million years ago Helicoprion was a successful predator in oceans globally, but what was it eating with its strange tooth whorl? The tooth whorl, according to the Smithsonian reconstruction, was not the first line of attack for this shark, and that is something important to talk about in terms of diet. When the tooth whorl is placed in the older positions (in the front of the mouth, the middle of the mouth, as an extension of the chin) the scenes we saw in the Animal Planet clip make a lot of sense; Helicoprion slicing fish and squid in half furiously as it swims about in the ocean. The interpretation of Mary Parrish (with help from Robert Purdy, Victor Springer, and Matt Carrano) places the tooth whorl in the gullet of Helicoprion. This positioning places the whorl in the same area as the gills (consisting of five gills rather than six/seven as is common in basal extant sharks for the shark enthusiasts) but without blocking their ability to extract oxygen from the water. The solution to the tooth whorl being in the throat was not having to swallow food before being able to chew it or bite at it. Instead, this reconstruction possesses a set of teeth similar to those of other sharks; a cartilaginous jaw housing rows of teeth that are used for catching, injuring, and otherwise stopping prey from getting away. The teeth in the throat, then, could have been used to snag prey as it entered the oral cavity, with the more traditional teeth pulling the prey into the mouth and the tooth whorl pulling the prey into the throat. Extant animals such as some snakes, fish, and other reptiles as well as extinct animals like mosasaurs possess teeth on the palatal bones that act in a similar way, helping to hold and move prey further into the throat and down the esophagus than mandibular and maxillary teeth are capable of doing. This version of the purpose of the tooth whorl is practical, if not as fantastic as some of the past iterations of the curious anatomical hypotheses.