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1Sarah Elise Field Bailey Keeler Elizabeth Lillard Kristin Oliver Using Teeth to Determine the Evolutionary Lineage of the Great White SharkSarah Elise Field Bailey Keeler Elizabeth Lillard Kristin Oliver
2Relating to Our Lectures: Craniate Relationships CRANIATESChondrichthyesSarcopterygiiVertebratesSharks are cartilaginous fish belonging to the group Chondrichtyes.OsteichthyesActinopterygii
3Why Study Shark Tooth Evolution? Sharks are cartilaginousTeeth are calcified – long lastingGood for pre-historic shark morphology, predation techniques, and environmental conditions.Common ancestor with bony fishes: feeding behaviors can shed light on vertebrate feeding systems function and evolution. (Motta 2001, 132)Because their entire skeleton is made of various cartilaginous components, while the teeth are calcified (bone), the teeth are usually the only part of a shark that is preserved after death. Thus, shark teeth are often the only means to discovering morphology, predation techniques, and environmental conditions of extinct sharks. The background picture here contains 26,000 fossilized shark teeth, which is about the number of teeth a shark will shed in their lifetime– Sharks share a common ancestor with bony fishes, so discoveries concerning their feeding behaviors can shed light on vertebrate feeding systems function and evolution.
4Examples of Extinct Mako Teeth The morphology of shark teeth is an indication of their general feeding habits/prey types. These are examples of extinct Mako teeth. The mako sharks generally have needle-like teeth. This shape is good for catching streamlined-slippery prey like fish.Sharp, needle like teeth usually indicate a diet consisting primarily of fish. Pointy teeth are good for catching streamlined-slippery prey.-elasmo-research.org (Images) -Shark Savers (text)
5Shortfin Mako Tooth A modern day Mako tooth. a needle-like but not-extinct example of a Mako tooth
6Megalodon Tooth -Broadly Triangular, thick, with fine serrations. -ReefQuestMegalodon teeth show a different kind of morphology: broad, triangular, thick, with fine serrations.
7Otodus ObliquusA direct descendent of the Megalodon (Carcharocles megalodon). A more triangular smooth blade.ReefQuestA tooth with similar morphology: a direct descendant of the Megalodon: Otodus Obliquus. This tooth is smooth, it lacks the finely serated edge seen in Megalodon teeth.
8Great White Shark (Carcharodon carcharias) Broadly triangular, flattened, coarsely serrated. –ReefQuestGreat white shark’s teeth have more defined serrations than the megalodon. These types of teeth in general are good for biting off chunks of prey and would indicated a diet of larger animals like seals
10Other Shark Teeth Morphologies There are also benthic feeding sharks with plate-like teeth for crushing the shells of their prey, and filter feeders like the whale shark whose teeth are tiny and useless. (Shark Savers)Australianmuseum.netThe other two types of shark tooth morphology include benthic feeding sharks, which have plate-like teeth for crushing the shells of prey, and filter feeders like the whale shark with has tiny mostly useless teeth. That is a picture of whale shark teeth.
12MegalodonThe Great White shark may be a descendent of a super-shark known as Megalodon. (They are both predatory lamnid sharks . Legendary for its enormous size – scientists suspect the Megalodon to have been easily over 50 feet long. The largest Great White shark ever discovered measured only 21 feet long The Megalodon has been extinct since the end of the Pliocene Epoch
13Megalodon-Great White Theory (pros) Tooth morphologysize and shapeLinnaean System (Early 1800’s)HeterochronySize and shape are a result of differences in the timing of developmentVertebrassimilarThe more modern, competing theory is that the great white evolved from the mako shark (Isurus Hastalis). Mako and great white sharks have similar densities in the serrations of their teeth (Ciampaglio, 814). However, according to the megalodon theory, these similarities may be a result of convergent evolution due to the similarity of their diets rather than direct evolutionary descent of one from the other (Castro, 23). Proponents of the megalodon theory explain the differences in serrations between the great white and megalodon sharks by attributing them to differences in heterochrony or the different life history of the two species. Megalodon proponents point out that it is not feasible to compare similarly sized teeth of the great white with that of the megalodon, since comparing a tooth coming from a megalodon that is the same size as a great white would mean comparing a premature megalodon tooth with a mature great white tooth. This would not account for changes in heterochrony. As megalodon sharks matured and their diet changed, so they may have developed these serrations, which are similar to a mature great white, as part of a later life stage (Ciampaglio, 806).
14Discrepancies (Megalodon) (Great White) (Ciampaglio) (Ancestral Mako) However, looking at the differences in serrations, the great white has very irregular, pointed serrations similar to that of the ancestral mako as opposed to the megalodon. This arises for the more recent second theory that is largely supported.(Great White)(Ciampaglio)(Ancestral Mako)
15Carcharodon carcharias After years of study, a new hypothesis has developed since the 1800s involving Carcharodon hastalis, Carcharodon hubbelli, andCarcharodon carcharias. Carcharodon hastalis and Carcharodon hubbelli are both types of broad-toothed makos.
16Carcharodon hastalisC. hastalis and the great white have similar tooth characteristics. Recently, a transitional mako species (Carcharodon hubbelli)was discovered that strengthens the bond between C. hastalis and C. carcharodon. C. hubelli has tooth crowns that are convex and curve similarly to that of C. hastalis. The serrations are enlarged at the base of the tooth for C. hubbelli, but weaker overall compared to C. carcharias, and appear to be the intermediate between C. hastalis and C. carcharias. (Ehret, 1148)
17Carcharodon hubbelli at the Pisco Formation C. hubbelli roamed the seas from the late Miocene to the early Pliocene. The great white shark has been dated back as far as the Early Pliocene. This puts C. hubbelli at a perfect time in history to be an ancestor of the great white. C. hubbelli teeth are a step in the evolution of teeth serrations, demonstrating a combination of characteristics from C. hastalis and the great white. Great white teeth from the Early Pliocene had weak to moderate serrations relative to the modern Great White. Serrations developed in response to a change in diet, from a solely piscivourous diet, to one incorporating mammals. A piece of amysticete whale mandible was found in the teeth of C. hubbelli, suggesting an evolving diet from that of C. hastalis, which was solely piscivourous. (Ehret et. al., 1150)
19C. hubbelli VertebraeAn additional analysis was done on the vertebral column of C. hubbelli. The C. hubbelli specimen was found to be 20 years old and 4.89 to 5.09 meters in length. This would put it at a slightly slower growth rate than great white sharks today. (Ehret et. al, 1150) This new intermediate species makes the mako theory much more plausible than that of the megalodon. Ehret’s study is immensely important to the ancestry of the great white, and only a recent development, since it was published in November.
20Other Examples of Shark Teeth Nurse SharkTiger Sharkexamples of other types of shark teeth (all living sharks)Nurse shark:Tiger shark:Lemon shark:Bull shark: reef questWhale SharkLemon SharkBull Shark
22This is only fossil evidence that this shark existed This is only fossil evidence that this shark existed. So what part of the shark is this? And where does it fit? This belongs to the shark Helicoprion. These fossilized tooth whorls are the only evidence that these sharks even existed. So as you can imagine, there is very little concrete evidence as to their behavior and life history. Everything we know about this shark is conjecture, including the placement of this whorl. This whorl also shows that the shark never lost any teeth!Helicoprion!
23Early TheoriesThis slide shows some of the early theories on the exact placement of the spiral. As you can see, scientists have tried a variety of different locations. It is pretty certain however, that these are in fact teeth, and that they existed in the mouth region.Both: A Karpinsky’s early drawings
24Shift to Lower JawThe upper jaw theory was thrown out pretty quickly, in favor of a lower jaw positioning. Here are two examples of different lower jaw theories. Both are still a little bit fantastic and unrealistic in terms of actually feeding.Lower pic: Smithsonian Paleobio departmentUpper pic:
25The most realistic theory is a modification of the lower jaw placement The most realistic theory is a modification of the lower jaw placement. This proposes that the whorl actually grows into the lower jaw, and leaves the youngest 1/3 of teeth exposed to function as actual teeth. This theory also suggests that the upper jaw is used as a hard grinding surface. This theory has also completely changed peoples ideas on the feeding behaviors of helicoprion. Prior to this theory, the shark was believed to be a benthic feeder, however now they are thought to eat fish and cephalopodsUpper pic:Lower pic: Lebedev 2009Most Current Theory
26Frill Shark!The frill shark was believed to be essentially extinct until 2007 when a Japanese fisherman spotted what he believed to be a sea snake. The shark was captured and put into a marine sanctuary in Japan, but it died a few hours later. Frill sharks live very deep, and only really come up when sick. They are quite primitive, and have evolved very little. The shark has 6 paired gill slits which give it a ‘frilled’ appearance.Bottom pic:
272007 most recent capture – off Japanese coast Usually live at bottom and only come up if sick. This one died w/in a few hours of capture.Believed to be extinctPic:
286 gill slits = “frilled” throat Jaw articulates almost behind head, giving ability to really open up wideThe jaw also articulated almost behind the head giving it the ability to open its mouth really wide.Pic:
30Conservation: Studying shark teeth sheds light on feeding strategy and environmental conditions which would allow conservationists to make more informed decisions regarding the ecosystems and prey necessary to sustain a population of Great Whites. Also, understanding their evolution could shed light on the possible adaptive strategies utilized by sharks in response to changing environments.Conservation:Studying shark teeth sheds lightConservation
33CitationsCastro, J. I. Great white sharks: The biology of carcharodon carcharias Ciampaglio, C. N., & Wray, G. A. Tracing the ancestry of the great white shark, carcharodon carcharias, using morphometric analyses of fossil teeth Journal of Vertebrate Paleontology, 26(4): Ebert, D., and L. Compagno. Chlamydoselachus Africana, a New Species of Frilled Shark from Southern Africa Zootaxa 2173: n. pag. Web. Ehret, Dana J. Origin of the White Shark Carcharodon (Lamniformes: Lamnidae) Based on Recalibration of the Upper Neogene Pisco Formation of Peru Palaeontology 55.6: The Palaeontological Association. Web. 19 Nov Lebedev, O. A New Specimen of Helicoprion Karpinsky , 1899 from Kazakhstanian Cisurals and a New Reconstruction of Its Tooth Whorl and Function Acta Zoologica 90: Web. Manning, P. Giant shark: Megalodon, prehistoric super predator New York: Media Source. Martin, A. Deep Sea: Frilled Shark. Deep Sea: Frilled Shark N.p., Web. <http://elasmo-research.org/education/ecology/deepsea-frilled_shark.htm>. Motta, Philip J., and Cheryl D. Wilga. Advances in the Study of Feeding Behaviors, Mechanisms, and Mechanics of Sharks Environmental Biology of Fishes 60: Paul, L. & Fowler, S. (SSG Australia & Oceania Regional Workshop, March 2003) Chlamydoselachus anguineus. In: IUCN IUCN Red List of Threatened Species. Version <www.iucnredlist.org> Purdy, R. The Orthodonty of Helicoprion. Smithsonian Department of Paleobiology, Web. ReefQuest Center for Shark Research. Lamniformes: Mackerel Sharks. Web. 23 Nov <http://www.elasmo-research.org/education/shark_profiles/lamniformes.htm>. Renz, Mark. Megalodon: Hunting the Hunter PaleoPress. Shark Savers Inc. Shark Teeth. Web. 22 Nov <http://www.sharksavers.org/en/education/biology/shark-teeth1/>. Tanaka, S., Y. Shiobara, S. Hioki, H. Abe, G. Nishi, K. Yano, and K. Suzuki. The Reproductive Biology of the Frilled Shark, Chlamydoselachus Anguineus from Suruga Bay, Japan Japanese Journal of Ichthyology 37.3: n. pag. Web Venice Florida dot com!. Venice Florida- Shark and Sharks’ Teeth Information. Shark Teeth-General Info. Web. 22 Nov <http://www.veniceflorida.com/shark.htm>.