DOCSLIB.ORG

Quantitative Analysis of Dental Microwear in Hadrosaurid Dinosaurs, and the Implications for Hypotheses of Jaw Mechanics and Feeding

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Quantitative Analysis of Dental Microwear in Hadrosaurid Dinosaurs, and the Implications for Hypotheses of Jaw Mechanics and Feeding Quantitative analysis of dental microwear in hadrosaurid dinosaurs, and the implications for hypotheses of jaw mechanics and feeding Vincent S. Williamsa, Paul M. Barrettb, and Mark A. Purnella,1 aDepartment of Geology, University of Leicester, Leicester LE1 7RH, United Kingdom; and bDepartment of Palaeontology, Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom Edited by Peter R. Crane, University of Chicago, Chicago, IL, and approved May 5, 2009 (received for review December 11, 2008) Understanding the feeding mechanisms and diet of nonavian functional analogue, and no fossil evidence exists to show the dinosaurs is fundamental to understanding the paleobiology of size and shape of the interarticular fibrocartilages and the these taxa and their role in Mesozoic terrestrial ecosystems. Var- limitations these would have placed on jaw motions. Here, we ious methods, including biomechanical analysis and 3D computer present the results of quantitative tooth microwear analysis of a modeling, have been used to generate detailed functional hypoth- hadrosaurian dinosaur, and we demonstrate how these provide eses, but in the absence of either direct observations of dinosaur a robust test of functional hypotheses. feeding behavior, or close living functional analogues, testing Previous research into hadrosaurid feeding mechanisms these hypotheses is problematic. Microscopic scratches that form reached contradictory conclusions. The extensive early work of on teeth in vivo during feeding are known to record the relative Ostrom (7) suggested propalinal translation of the mandibles (an motion of the tooth rows to each other during feeding and to anteroposterior movement of the lower jaw during the power capture evidence of tooth–food interactions. Analysis of this dental stroke). This was later questioned (8), and tooth wear was used microwear provides a powerful tool for testing hypotheses of jaw to infer side-to-side (transverse) movements of the mandibles mechanics, diet, and trophic niche; yet, quantitative analysis of relative to the maxilla. Norman and Weishampel (6, 9–11) microwear in dinosaurs has not been attempted. Here, we show conducted kinematic and detailed functional anatomical analy- that analysis of tooth microwear orientation provides direct evi- ses of all available hypotheses of hadrosaurid jaw mechanics and dence for the relative motions of jaws during feeding in hadro- postulated a novel jaw mechanism, termed pleurokinesis. In this saurid ornithopods, the dominant terrestrial herbivores of the Late Cretaceous. Statistical testing demonstrates that Edmontosaurus model, isognathic vertical adduction of the lower jaws generated teeth preserve 4 distinct sets of scratches in different orientations. a transverse power stroke. This was brought about by lateral In terms of jaw mechanics, these data indicate an isognathic, rotation of the maxillae and suspensorium relative to the skull near-vertical posterodorsal power stroke during feeding; near- roof and driven by contact between the dentary and maxillary vertical jaw opening; and propalinal movements in near anterior teeth during occlusion. Lateral rotation of the maxillae was and near posterior directions. Our analysis supports the presence accommodated by a pleurokinetic hinge (between the maxilla/ of a pleurokinetic hinge, and the straightness and parallelism of jugal/quadrate and the akinetic skull) and was associated with scratches indicate a tightly controlled occlusion. The dominance of slight propalinal movements caused by abduction and retraction scratched microwear fabrics suggests that Edmontosaurus was a of the quadrate (streptostylism). However, recent work involving grazer rather than a browser. 3D modeling of feeding kinematics in Edmontosaurus has sug- gested that pleurokinesis would generate extensive secondary Cretaceous ͉ Ornithopoda ͉ tooth ͉ trophic ecology ͉ Vertebrata (intracranial) movements beyond the pleurokinetic hinge (12). Testing of these functional models has been difficult because of econstructing the feeding mechanisms and details of trophic the absence of direct evidence for the mastication process in Recology of extinct animals based on functional morphology is hadrosaurids. fraught with difficulty (1). In vertebrates, tooth form provides only Quantitative analysis of tooth microwear offers a hitherto a general guide to diet: the same tooth form can serve more than unexplored route to testing feeding mechanisms in nonavian one function, and that function can vary with specific feeding dinosaurs. Microwear refers to the microscopic polished, behavior. Further complications arise because functional optimi- scratched, or pitted textures produced in vivo by the actions of zation of tooth form can be constrained by the need to process abrasives in food and by the compressive and shearing forces that fallback foods during times of resource scarcity (2), and animals act on teeth during feeding (13, 14). Quantitative analysis of with an apparently specialized feeding apparatus can have gener- tooth microwear is an extremely powerful tool and has been alist diets (3). These problems are especially acute in groups like applied extensively to fossil primates and hominins to evaluate herbivorous, nonavian dinosaurs, where most species have gener- the role of dietary changes in human evolution (15, 16). Applied alized homodont dentitions and lack close living analogues. to extinct nonprimate mammals, quantitative tooth microwear Among herbivorous dinosaurs, feeding of hadrosaurids has analysis has also provided direct evidence of tooth use, diet, and attracted particular attention. They were the dominant herbiv- feeding (13, 17, 18) and has revealed how feeding in ungulates orous vertebrates in many Late Cretaceous ecosystems, in terms has tracked past environmental change (19). of both species richness and abundance, and they achieved a near-global distribution (4, 5). This success is frequently attrib- uted to the complex jaw mechanisms possessed by these taxa, Author contributions: V.S.W. and M.A.P. designed research; V.S.W. and M.A.P. performed which would have given them a level of masticatory prowess research; V.S.W. and M.A.P. analyzed data; and V.S.W., P.M.B., and M.A.P. wrote the paper. equal to that of many extant mammals (6). Current models of The authors declare no conflict of interest. feeding mechanisms in hadrosaurid dinosaurs are based on This article is a PNAS Direct Submission. analyses of functional morphology and rely on interpretations of 1To whom correspondence should be addressed. E-mail: [email protected]. musculature rather than direct evidence. No extant species has This article contains supporting information online at www.pnas.org/cgi/content/full/ a sufficiently similar skull morphology to act as a convincing 0812631106/DCSupplemental. 11194–11199 ͉ PNAS ͉ July 7, 2009 ͉ vol. 106 ͉ no. 27 www.pnas.org͞cgi͞doi͞10.1073͞pnas.0812631106 B 2323 2222 2121 2020 1919 1818 1717 1616 1515 1414 1313 1212 1111 1010 9 8 7 6 5 4 3 2 1 10 mm mean orientations, 4 classes C0° 10 teeth 1 4 A 2 3 180° 20.13° D 11 5 mm 10 63.17° 1 9 64.56° E 115.62°100 µm Right Anteriorr LingualL PosteriorLabial Left 3 5 l Labial 8 2 6 4 F mean orientations, 4 classes 0° tooth 2, 11 sites 1 4 2 3 180° 7 24.14° 1 58.23° 1 left left right right 62.63° ° dentary maxilla dentary maxilla 115.84 Fig. 1. Microwear in Edmontosaurus.(A) Orientation of functional surfaces (wear facets) on teeth, in approximate life orientation; diagrams below show these same 4 functional surfaces oriented with tips upward and viewed perpendicular to the occlusal plane. (B) Right maxilla, specimen NHM R3638, anterior to left. Vector plots indicate mean scratch orientation and relative length for each of the 4 classes in 10 teeth, line weight proportional to number of scratches. (C) Mean orientations for each class of scratches in each of the 10 teeth; for each class, the mean of the mean orientations with 99% confidence interval is shown. Dashed lines lie outside the confidence interval. (D) Second tooth from posterior (box in B). Vector plots indicate mean scratch orientation and relative length for each of the 4 classes in 11 sites, line weight proportional to number of scratches. Gray boxes show sites sampled for transect data (Fig. S1): 1 toward tip, 6 toward base; site 7 more basal than field of view shown. (E) One of the sampled areas (black box in D); diagonal lower right shows feature markup from Microware 4.0.2. (F) Mean orientations for each class of scratches in each of the 11 sites; for each class, the mean of the mean orientations with 99% confidence interval is also shown. Dashed lines lie outside the confidence interval. Microwear analysis is starting to be applied widely to dino- Here, we test the null hypotheses that microwear does not saurs (20–23), and recent research on living and fossil fish differ between sample sites within the occlusal surface of a tooth suggests that quantitative microwear analysis has broad appli- and that microwear does not differ between teeth along a tooth cability beyond mammals (24, 25), but to date there has been no row within an individual. We show that hadrosaurid dinosaur quantitative analysis of tooth microwear in dinosaurs. However, teeth have well-developed microwear signatures that allow us to there are significant differences between dinosaur and mammal conduct robust statistical testing of these hypotheses, and we feeding mechanisms that make microwear analysis and inter- demonstrate that quantitative microwear
Load more

Recommended publications
  • Ontogeny Reveals Function and Evolution of the Hadrosaurid Dinosaur Dental Battery Aaron R
    LeBlanc et al. BMC Evolutionary Biology (2016) 16:152 DOI 10.1186/s12862-016-0721-1 RESEARCH ARTICLE Open Access Ontogeny reveals function and evolution of the hadrosaurid dinosaur dental battery Aaron R. H. LeBlanc1*, Robert R. Reisz1,2, David C. Evans3 and Alida M. Bailleul4 Abstract Background: Hadrosaurid dinosaurs, dominant Late Cretaceous herbivores, possessed complex dental batteries with up to 300 teeth in each jaw ramus. Despite extensive interest in the adaptive significance of the dental battery, surprisingly little is known about how the battery evolved from the ancestral dinosaurian dentition, or how it functioned in the living organism. We undertook the first comprehensive, tissue-level study of dental ontogeny in hadrosaurids using several intact maxillary and dentary batteries and compared them to sections of other archosaurs and mammals. We used these comparisons to pinpoint shifts in the ancestral reptilian pattern of tooth ontogeny that allowed hadrosaurids to form complex dental batteries. Results: Comparisons of hadrosaurid dental ontogeny with that of other amniotes reveals that the ability to halt normal tooth replacement and functionalize the tooth root into the occlusal surface was key to the evolution of dental batteries. The retention of older generations of teeth was driven by acceleration in the timing and rate of dental tissue formation. The hadrosaurid dental battery is a highly modified form of the typical dinosaurian gomphosis with a unique tooth-to-tooth attachment that permitted constant and perfectly timed tooth eruption along the whole battery. Conclusions: We demonstrate that each battery was a highly dynamic, integrated matrix of living replacement and, remarkably, dead grinding teeth connected by a network of ligaments that permitted fine scale flexibility within the battery.
    [Show full text]
  • Theropod Teeth from the Upper Maastrichtian Hell Creek Formation “Sue” Quarry: New Morphotypes and Faunal Comparisons
    Theropod teeth from the upper Maastrichtian Hell Creek Formation “Sue” Quarry: New morphotypes and faunal comparisons TERRY A. GATES, LINDSAY E. ZANNO, and PETER J. MAKOVICKY Gates, T.A., Zanno, L.E., and Makovicky, P.J. 2015. Theropod teeth from the upper Maastrichtian Hell Creek Formation “Sue” Quarry: New morphotypes and faunal comparisons. Acta Palaeontologica Polonica 60 (1): 131–139. Isolated teeth from vertebrate microfossil localities often provide unique information on the biodiversity of ancient ecosystems that might otherwise remain unrecognized. Microfossil sampling is a particularly valuable tool for doc- umenting taxa that are poorly represented in macrofossil surveys due to small body size, fragile skeletal structure, or relatively low ecosystem abundance. Because biodiversity patterns in the late Maastrichtian of North American are the primary data for a broad array of studies regarding non-avian dinosaur extinction in the terminal Cretaceous, intensive sampling on multiple scales is critical to understanding the nature of this event. We address theropod biodiversity in the Maastrichtian by examining teeth collected from the Hell Creek Formation locality that yielded FMNH PR 2081 (the Tyrannosaurus rex specimen “Sue”). Eight morphotypes (three previously undocumented) are identified in the sample, representing Tyrannosauridae, Dromaeosauridae, Troodontidae, and Avialae. Noticeably absent are teeth attributed to the morphotypes Richardoestesia and Paronychodon. Morphometric comparison to dromaeosaurid teeth from multiple Hell Creek and Lance formations microsites reveals two unique dromaeosaurid morphotypes bearing finer distal denticles than present on teeth of similar size, and also differences in crown shape in at least one of these. These findings suggest more dromaeosaurid taxa, and a higher Maastrichtian biodiversity, than previously appreciated.
    [Show full text]
  • Dinosaur Gallery Explorer’S Notebook
    Dinosaur Gallery Explorer’s Notebook Name: Class: Level 3 © Museum of Natural Sciences Education Service 2012 29, Rue Vautier, 1000 Brussels. Tel: +32 (0)2 627 42 52 [email protected] www.sciencesnaturelles.be 1 Dinosaur Gallery - Level 3 Plan of the Gallery Each time you see a number in the margin of this notebook you must move to a new place in the gallery. Find where you are on the plan. entrance via mezzanine (level 0) stairs down to level -2 stairs up to level -1 The numbers on the plan correspond to the different stages on the dinosaur gallery. The numbers start on page 6 of this notebook Make sure you have a sharp pencil and a rubber with you! Make a team of three to answer the questions. 2 Dinosaur Gallery - Level 3 Before your visit... The first pages of this notebook will help you prepare for your visit to the museum! * Words followed by an asterisk are explained in the glossary on the last page. What is a dinosaur? Below are some characteristics of dinosaurs feet underneath their bodies 4 feet terrestrial eggs with shells vertebrate* ATTENTION Dinosaurs were terrestrial animals. At the same time, sea reptiles and flying reptiles lived on the Earth, but these animals were NOT dinosaurs! Herbivore or carnivore? To know whether a dinosaur ate meat or plants, take a look at its teeth herbivore carnivore When a dinosaur was a When a dinosaur was a herbivore, its teeth had flat ends, carnivore, its teeth had pointed like the prongs of a rake or like ends, like knives.
    [Show full text]
  • 71St Annual Meeting Society of Vertebrate Paleontology Paris Las Vegas Las Vegas, Nevada, USA November 2 – 5, 2011 SESSION CONCURRENT SESSION CONCURRENT
    ISSN 1937-2809 online Journal of Supplement to the November 2011 Vertebrate Paleontology Vertebrate Society of Vertebrate Paleontology Society of Vertebrate 71st Annual Meeting Paleontology Society of Vertebrate Las Vegas Paris Nevada, USA Las Vegas, November 2 – 5, 2011 Program and Abstracts Society of Vertebrate Paleontology 71st Annual Meeting Program and Abstracts COMMITTEE MEETING ROOM POSTER SESSION/ CONCURRENT CONCURRENT SESSION EXHIBITS SESSION COMMITTEE MEETING ROOMS AUCTION EVENT REGISTRATION, CONCURRENT MERCHANDISE SESSION LOUNGE, EDUCATION & OUTREACH SPEAKER READY COMMITTEE MEETING POSTER SESSION ROOM ROOM SOCIETY OF VERTEBRATE PALEONTOLOGY ABSTRACTS OF PAPERS SEVENTY-FIRST ANNUAL MEETING PARIS LAS VEGAS HOTEL LAS VEGAS, NV, USA NOVEMBER 2–5, 2011 HOST COMMITTEE Stephen Rowland, Co-Chair; Aubrey Bonde, Co-Chair; Joshua Bonde; David Elliott; Lee Hall; Jerry Harris; Andrew Milner; Eric Roberts EXECUTIVE COMMITTEE Philip Currie, President; Blaire Van Valkenburgh, Past President; Catherine Forster, Vice President; Christopher Bell, Secretary; Ted Vlamis, Treasurer; Julia Clarke, Member at Large; Kristina Curry Rogers, Member at Large; Lars Werdelin, Member at Large SYMPOSIUM CONVENORS Roger B.J. Benson, Richard J. Butler, Nadia B. Fröbisch, Hans C.E. Larsson, Mark A. Loewen, Philip D. Mannion, Jim I. Mead, Eric M. Roberts, Scott D. Sampson, Eric D. Scott, Kathleen Springer PROGRAM COMMITTEE Jonathan Bloch, Co-Chair; Anjali Goswami, Co-Chair; Jason Anderson; Paul Barrett; Brian Beatty; Kerin Claeson; Kristina Curry Rogers; Ted Daeschler; David Evans; David Fox; Nadia B. Fröbisch; Christian Kammerer; Johannes Müller; Emily Rayfield; William Sanders; Bruce Shockey; Mary Silcox; Michelle Stocker; Rebecca Terry November 2011—PROGRAM AND ABSTRACTS 1 Members and Friends of the Society of Vertebrate Paleontology, The Host Committee cordially welcomes you to the 71st Annual Meeting of the Society of Vertebrate Paleontology in Las Vegas.
    [Show full text]
  • A Troodontid Dinosaur from the Latest Cretaceous of India
    ARTICLE Received 14 Dec 2012 | Accepted 7 Mar 2013 | Published 16 Apr 2013 DOI: 10.1038/ncomms2716 A troodontid dinosaur from the latest Cretaceous of India A. Goswami1,2, G.V.R. Prasad3, O. Verma4, J.J. Flynn5 & R.B.J. Benson6 Troodontid dinosaurs share a close ancestry with birds and were distributed widely across Laurasia during the Cretaceous. Hundreds of occurrences of troodontid bones, and their highly distinctive teeth, are known from North America, Europe and Asia. Thus far, however, they remain unknown from Gondwanan landmasses. Here we report the discovery of a troodontid tooth from the uppermost Cretaceous Kallamedu Formation in the Cauvery Basin of South India. This is the first Gondwanan record for troodontids, extending their geographic range by nearly 10,000 km, and representing the first confirmed non-avian tetanuran dinosaur from the Indian subcontinent. This small-bodied maniraptoran dinosaur is an unexpected and distinctly ‘Laurasian’ component of an otherwise typical ‘Gondwanan’ tetrapod assemblage, including notosuchian crocodiles, abelisauroid dinosaurs and gondwanathere mammals. This discovery raises the question of whether troodontids dispersed to India from Laurasia in the Late Cretaceous, or whether a broader Gondwanan distribution of troodontids remains to be discovered. 1 Department of Genetics, Evolution, and Environment, University College London, London WC1E 6BT, UK. 2 Department of Earth Sciences, University College London, London WC1E 6BT, UK. 3 Department of Geology, Centre for Advanced Studies, University of Delhi, New Delhi 110 007, India. 4 Geology Discipline Group, School of Sciences, Indira Gandhi National Open University, New Delhi 110 068, India. 5 Division of Paleontology and Richard Gilder Graduate School, American Museum of Natural History, New York, New York 10024, USA.
    [Show full text]
  • Evidence for a Tyrannosaurus Rex from Southeastern Colorado
    Evidence for aTyrannosaurus rex from southeastern Colorado Keith Berry, Platte Valley School District Re-7, Science Department, Kersey, Colorado 80644, and Frontiers of Science Institute, Mathematics and Science Teaching Institute, University of Northern Colorado, Greeley, Colorado 80369, [email protected] Discovery Femur: A limb bone fragment (TSJC racy of ± 0.5 mm along a radial transect, T. 2008.1.2) is also tentatively identified as cf. rex annual growth markers are exception- Dinosaur tooth and bone fragments were T. rex. Theropod bones commonly exhibit ally good predictors for the growth lines recovered from private property at an onion-skin layering in cross section (K. observed in this bone (cχ2 = 1.44, df = 6, undisclosed locality in southeastern Colo- Carpenter, pers. comm. 2007), and this p-value > 0.95). As T. rex is the only animal rado. The site is in an unnamed, transitional bone seems to lack this feature, although known to exhibit this characteristic pattern member of the uppermost Pierre Shale and the bone has distinct, differentiable layers. of growth (Erickson et al. 2004; Chinsamy- is likely within the Baculites eliasi ammonite Whereas the bone itself may not be exclu- Turan 2005), this is believed to be a fairly zone (N. Larson, pers. comm. 2007), mak- sively attributed to a theropod based on its powerful diagnostic test. ing the site early Maastrichtian. This is the gross histological properties alone, there are Significance—Estimated to be about 71 first record of dinosaur fossils from these quantitative reasons supporting this diag- m.y. old based on the age of the Baculites strata.
    [Show full text]
  • Katherine Keenan Bramble
    A Histological Analysis of the Hadrosaurid Dental Battery by Katherine Keenan Bramble A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Systematics and Evolution Department of Biological Sciences University of Alberta © Katherine Keenan Bramble, 2017 Abstract The first histological study of an entire hadrosaurid dental battery provides a better understanding of this complex structure. The hadrosaurid dental battery is composed of interlocking, vertically stacked columns of teeth that form a complex grinding surface. The dental battery was previously considered to be a solid, cemented structure based on superficial examination of intact batteries and thin sections of isolated teeth. This first description of the dental battery using thin sections through the entire structure refutes the model of a single, fused mass of teeth. These thin sections confirm the presence of periodontal ligament connections between all teeth, underscoring its dynamic nature. The serial thin sections across an adult dental battery also revealed signs of gradual and possibly ontogenetic tooth migration. These signs include the extensive remodeling of the alveolar septa and the anteroposterior displacement of successive generations of teeth. The four most posterior tooth families migrated posteriorly whereas the remaining tooth families had a progressively more pronounced anterior trajectory. This migration is pronounced enough in some areas to cause extensive resorption of neighbouring teeth. Thin sections through a dental battery of a perinatal specimen reveal that all of the alveolar septa are angled anteriorly, which suggests that extensive and unidirectional tooth migration begins early in ontogeny and that any additional migration happens later in ontogeny.
    [Show full text]
  • Second Discovery of a Spinosaurid Tooth from the Sebayashi Formation (Lower Cretaceous), Kanna Town, Gunma Prefecture, Japan
    群馬県立自然史博物館研究報告（21）：1－6,2017 1 Bull.Gunma Mus.Natu.Hist（. 21）：1－6,2017 Original Article Second discovery of a spinosaurid tooth from the Sebayashi Formation (Lower Cretaceous), Kanna Town, Gunma Prefecture, Japan 1 2 2 KUBOTA Katsuhiro, TAKAKUWA Yuji and HASEGAWA Yoshikazu 1Kanna Dinosaur Center: 51-2, Kagahara, Kanna, Tano, Gunma 370-1602, Japan ([email protected]) 2Gunma Museum of Natural History: 1674-1 Kamikuroiwa, Tomioka, Gunma 370-2345, Japan ([email protected]; [email protected]) Abstract： A fragment of an isolated tooth is described from the Lower Cretaceous Sebayashi Formation of the Sanchu Group. Its crown is almost round in cross section and shows distinctive flutes. Between the flutes, there are longitudinal finely granular structures. The distinctive carinae have poorly defined serrations. It is probably assigned as a spinosaurid theropod dinosaur and is the second report from Japan. This spinosaurid tooth is found from the higher stratigraphic horizon of the same formation than the first. The occurrences of spinosaurids from two horizons suggest that spinosaurids might have habituated this area during the deposit of the Sebayashi Formation. The dental comparison between Asian and other spinosaurids suggests that Asian spinosaurids may have unique dental characteristics and be different from any known spinosaurids, although the phylogenetic relationships between Asian and other spinosaurids (baryonychines and spinosaurines) are unclear. Key words: Dinosaur, Spinosauridae, Sebayashi Formation, Gunma Prefecture, Kanna Town Introduction Macro-sized and longitudinal ornamentation on the crown is characteristic in spinosaurids and had been called as crest, flute, A fragmentary dinosaur tooth was collected in a fossil- ridge, and striation (Fig.
    [Show full text]
  • Mammal-Like Mastication for the Dinosaur Leptoceratops 8 July 2016, by Andrew Farke
    Mammal-like mastication for the dinosaur Leptoceratops 8 July 2016, by Andrew Farke in just about every plane of movement imaginable. Different chewing styles characterize different diets as well as different groups of organisms; if you ever get the opportunity, take a look at the fairly simple motions of an iguana chopping up a leaf versus the complex dance of teeth, jaws, and tongue in a cow chewing on grass. More complex motions can allow more thorough processing of food before it enters the stomach, which has all sorts of advantages for digestive efficiency and nutrient extraction. Why do we care about chewing? From a biological perspective, feeding is an incredibly basic yet often poorly understood aspect of an organisms' life. Everything needs to eat, and it's the style of eating that can make it or break it for a species on geological timescales as well as within an individual organism's lifetime. Different styles of chewing can open up different food sources, and is one part of what helps species compete against each other ecologically. If we understand feeding in extinct organisms, we can better understand how they fit within their immediate environment and their world. Tiny scratches on a dinosaur tooth, viewed under a scanning electron microscope. Viewed at actual size, the image would only be a millimeter tall! Credit: Varriale 2016 We all chew, but hardly ever think about it. Even a moment's consideration, though, reveals how complex of a process it actually is. Jaws move, teeth gnash, and food gets broken from big bits into smaller bits.
    [Show full text]
  • Taphonomy and Sedimentology of Two Miocene Vertebrate Fossil Sites On
    Louisiana State University LSU Digital Commons LSU Master's Theses Graduate School 2010 Taphonomy and sedimentology of two Miocene vertebrate fossil sites on Fort Polk, Louisiana Julie Lynn Hill Louisiana State University and Agricultural and Mechanical College, [email protected] Follow this and additional works at: https://digitalcommons.lsu.edu/gradschool_theses Part of the Earth Sciences Commons Recommended Citation Hill, Julie Lynn, "Taphonomy and sedimentology of two Miocene vertebrate fossil sites on Fort Polk, Louisiana" (2010). LSU Master's Theses. 3336. https://digitalcommons.lsu.edu/gradschool_theses/3336 This Thesis is brought to you for free and open access by the Graduate School at LSU Digital Commons. It has been accepted for inclusion in LSU Master's Theses by an authorized graduate school editor of LSU Digital Commons. For more information, please contact [email protected]. TAPHONOMY AND SEDIMENTOLOGY OF TWO MIOCENE VERTEBRATE FOSSIL SITES ON FORT POLK, LOUISIANA A Thesis Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Master of Science In The Department of Geology and Geophysics by Julie Lynn Hill B.S., University of Wisconsin – Madison, 2002 August 2010 ACKNOWLEDGEMENTS Special thanks to my major advisor, Dr. Judith Schiebout, for providing conversation and guidance on life, the universe, and everything – from paleontology and academia to cats and good literature. Many thanks to committee members Drs. Laurie Anderson and Brooks Ellwood for stepping in when they were needed and offering new insight and encouragement that helped to shape this thesis. Thank you also to late committee member Dr.
    [Show full text]
  • Dinosaur Incubation Periods Directly Determined from Growth-Line Counts in Embryonic Teeth Show Reptilian-Grade Development
    Dinosaur incubation periods directly determined from growth-line counts in embryonic teeth show reptilian-grade development Gregory M. Ericksona,1, Darla K. Zelenitskyb, David Ian Kaya, and Mark A. Norellc aDepartment of Biological Science, Florida State University, Tallahassee, FL 32306-4295; bDepartment of Geoscience, University of Calgary, Calgary, AB, Canada T2N 1N4; and cDivision of Paleontology, American Museum of Natural History, New York, NY 10024 Edited by Neil H. Shubin, University of Chicago, Chicago, IL, and approved December 1, 2016 (received for review August 17, 2016) Birds stand out from other egg-laying amniotes by producing anatomical, behavioral and eggshell attributes of birds related to relatively small numbers of large eggs with very short incubation reproduction [e.g., medullary bone (32), brooding (33–36), egg- periods (average 11–85 d). This aspect promotes high survivorship shell with multiple structural layers (37, 38), pigmented eggs (39), by limiting exposure to predation and environmental perturba- asymmetric eggs (19, 40, 41), and monoautochronic egg pro- tion, allows for larger more fit young, and facilitates rapid attain- duction (19, 40)] trace back to their dinosaurian ancestry (42). For ment of adult size. Birds are living dinosaurs; their rapid development such reasons, rapid avian incubation has generally been assumed has been considered to reflect the primitive dinosaurian condition. throughout Dinosauria (43–45). Here, nonavian dinosaurian incubation periods in both small and Incubation period estimates using regressions of typical avian large ornithischian taxa are empirically determined through growth- values relative to egg mass range from 45 to 80 d across the line counts in embryonic teeth.
    [Show full text]
  • Palaeontologia Electronica CLEANING FOSSIL TOOTH
    Palaeontologia Electronica http://palaeo-electronica.org CLEANING FOSSIL TOOTH SURFACES FOR MICROWEAR ANALYSIS: USE OF SOLVENT GELS TO REMOVE RESISTANT CONSOLIDANT Vincent S. Williams and Adrian M. Doyle ABSTRACT Fine-scale surface texture analysis of teeth has become increasingly useful for anthropologists and palaeontologists to infer diet and jaw mechanics in fossil animals. We describe a fast, non-abrasive and residue free method for the removal of resistant consolidant from fossil teeth. The method utilises solvent gels, and its use is a signifi- cant improvement over previous techniques, particularly where microwear analysis is to be performed. The method adapts techniques originally developed by art conserva- tors for the removal of varnish from oil paintings without damaging the oil paint beneath. A combination of Carbopol (a water soluble acrylic polymer) and Ethomeen (a polyoxyethylene cocoamine detergent) allows solvents such as acetone and ethanol to be suspended in a gel for application to consolidant coated tooth surfaces. Key advantages are that dissolved consolidant is lifted away from the tooth surface into the solvent gel and a high degree of control is possible such that small discrete areas can be cleaned of consolidant. Because the solvents are held within a gel, cleaning of the tooth surface can be performed without the need for a fume hood. Vincent S. Williams. Department of Geology, University of Leicester, University Road, Leicester, LE1 7RH, UK. [email protected] Adrian M. Doyle. Conservation Department, Museum of London, 150 London Wall, London, EC2Y 5HN, UK. [email protected] KEY WORDS: solvent gel; microwear; consolidant removal INTRODUCTION cleaned prior to imaging or moulding.
    [Show full text]