Dinosaur tooth

Last updated
A tooth from a Tyrannosaurus T rex tooth - Garfield County Montana - Museum of the Rockies - 2013-07-08.jpg
A tooth from a Tyrannosaurus

Dinosaur teeth have been studied since 1822 when Mary Ann Mantell (1795-1869) and her husband Dr Gideon Algernon Mantell (1790-1852) discovered an Iguanodon tooth in Sussex in England. Unlike mammal teeth, individual dinosaur teeth are generally not considered by paleontologists to be diagnostic to the genus or species level for unknown taxa, due morphological convergence and variability between teeth. [1] and many historically named tooth taxa like Paronychodon and Richardoestesia are today considered nomina dubia , and are used as form taxa to refer to isolated teeth from other localities displaced considerably in time and space from the type specimens. However, it is possible to refer isolated teeth to known taxa provided that the tooth morphology is known and the teeth originate from a similar time and place.

Contents

Some of the most important anatomical information about dinosaur teeth is collected from polished, microscopically thin sections (histology), including the types of dental tissues present, tooth wear, tooth replacement patterns, how the teeth are attached, and the frequency of replacement. The actual material comprising a dinosaur tooth is not very different to teeth in modern animals. Most significant differences are in how the teeth fit together and continually regrew, with some examples shedding old teeth and others reabsorbing old teeth as they would grind down under chewing throughout a dinosaurs life.

Background

Bone histology of the non-avian dinosaur Shuvuuia and the early bird Confuciusornis Bone histology of Shuvuuia and Confuciusornis.png
Bone histology of the non-avian dinosaur Shuvuuia and the early bird Confuciusornis

The use of histology in paleontology has traditionally been more focused on examining long bones such as the femur or the humerus.[ citation needed ] Previous work on long bone histology revealed differences in the growth patterns of polar dinosaurs, [2] identified a case of dwarfism in Europasaurus , [3] reconstructed the life history of Dysalotosaurus by examining multiple specimens of different ontogenetic stages, [4] and suggested that Psittacosaurus underwent a postural change from a quadruped to biped as it matured. [5]

By contrast, dental histology has not been looked at in great detail in dinosaurs until more recently and there has been an increase in interest in this particular sub-field.[ citation needed ] Histology studies traditionally rely upon the destructive process of creating and examining thin sections under microscopy, often restricting studies to taxa that have plentiful specimens such as isolated teeth or damaged specimens. While non-destructive means of analysis are sometimes possible through the use of scanning electron microscopy (SEM) or micro computed tomography, much anatomical information is difficult to obtain without creating thin sections. [6] [7]

Histology

Histological study is microscopic examination, essential to revealing the most important aspects of dinosaur dental anatomy.

Selection

Different specimens will be suitable for looking at particular anatomical features. For example, specimens with teeth intact within the jaws are necessary to study tooth attachment as this information is lost on isolated teeth. [6] On the other hand, isolated teeth would be sufficient if the goal is to examine wear on the tooth surface.

Embedding and sectioning

Thin sections are prepared by first embedding a suitable specimen in epoxy resin. The embedded specimen can then be mounted and cut with a precision saw. [6] The resulting slice is attached to a slide and ground down, then polished, until it is thin enough, with a suitable surface to be examined with a microscope. [6]

Examination

Thin sections are typically examined with a petrographic microscope using plain light and cross-polarized light. Some structures are more easily visible and distinct using one type of light over the other due to differences in their mineral properties. Some specimens can also be examined with a SEM. [7]

Dental anatomy

Cross section of a typical theropod dinosaur tooth in side view. All dinosaur teeth possess the same tissue types but can differ in their appearance. Dental diagram.png
Cross section of a typical theropod dinosaur tooth in side view. All dinosaur teeth possess the same tissue types but can differ in their appearance.

Various major groups of dinosaurs have been examined through histology, these include the carnivorous theropods and herbivorous groups such as the sauropods, hadrosaurs and ceratopsians. [6] [8] [9] [10] [7] Listed below are some of the dental anatomy that has been identified through histology and interpretations on their significance.

Tissue types

There are generally 5 tissue types present in dinosaurs, and these have been found to be identical to those of their closest living non-avian relatives, the crocodilians. [6] One of the most significant findings is that despite differences in their appearance, dinosaur teeth are essentially composed of the same dental tissues found in modern mammals, crocodilians and other amniotes, suggesting that these tissues first evolved in a common ancestor and has been retained ever since. [11] [12]

  1. Enamel - This is the hard coating on the outside of the teeth and typically appears as a clear, thin featureless band on the tooth surface when viewed in cross section. [6] SEM analysis of the surface of dinosaur teeth revealed that their enamel form in prisms similar to mammals and that there is sufficient difference in the enamel microstructure to help pinpoint what group a tooth belonged to, sometimes to the genus level, when only isolated teeth are found. [13] Not all teeth are covered by a prismatic enamel, and in most taxa, prisms are perpendicular to the outer surface of the tooth. Complex arrangements such as visible in mammals are rare. [14] [15] Diagenetic alterations modify the structure and composition of both enamel and dentin. [16] [17] [18] [19]
  2. Dentine - This tissue makes up the bulk of the tooth and is characterized by long thin parallel tubules running throughout the body of the tooth. [6]
  3. Cementum - This tissue covers the root of a tooth and is an attachment tissue that forms part of the periodontium. It is typically infilled with Sharpey's fibers that help anchor the tooth in place in the socket. [6]
  4. Periodontal ligament - This is a soft tissue layer between the cementum and the tooth socket. While this is not preserved in fossils, there is always a mineral filled gap that is present in all dinosaur teeth between the cementum and the tooth socket, which infers the presence of soft tissue in life. [6]
  5. Alveolar bone - This is a type of bone that is typically spongy in appearance and forms the tooth socket itself. [6]
Top down view of a replacement tooth in Coelophysis growing up through the middle of pulp cavity in the older tooth. Coelophysis tooth replacement.jpg
Top down view of a replacement tooth in Coelophysis growing up through the middle of pulp cavity in the older tooth.

Growth

In some examples viewed in cross section, growth lines can be observed in the dentine of dinosaur teeth. These are known as lines of von Ebner and represent daily deposition of dentine. [20] Counting these lines provides the age of a tooth and comparing the age of the mature tooth to the replacement tooth in a socket provides an estimate of the tooth replacement rate. [20]

The difference in age between the oldest teeth and the youngest teeth is used to determine the rate of tooth replacement. [20]

Tooth replacement pattern

Many dinosaur teeth have been found to have a replacement pattern similar to other reptiles where a replacement tooth grows in the dental lamina on the inside of the jaw before migrating outwards, resorbing part of the growing functional tooth, until ready to erupt and replace it. [6] [21]

Tooth attachment

The tooth attachment mode of some dinosaurs has been referred to as thecodonty. [6] This is a condition where the tooth is deeply implanted into the tooth socket with periodontal ligament present, as is the case in crocodilians and mammals. [6] [12] In mammals, thecodonty is associated with dental occlusion while in crocodilians it has been proposed as a means to reduce stresses from bite forces. [22] [23] Coelophysis possessed neither dental occlusion nor a strong bite, raising questions as to why it possesses thecodonty. [6]

Dental batteries

Close up of hadrosauridae dental batteries in various Hadrosaurid dinosaurs Hadrosauroid tooth primary ridges.jpg
Close up of hadrosauridae dental batteries in various Hadrosaurid dinosaurs
Diagram showing the dental battery in the rebbachisaurid genus Nigersaurus Nigersaurus taqueti skull dental battery.jpg
Diagram showing the dental battery in the rebbachisaurid genus Nigersaurus

One of the most complex dentition found in dinosaurs are the dental batteries present in hadrosaurs (whose members were dominant species across the planet), Neoceratopsia (for example, Triceratops ), and Rebbachisauridae. [24]

These batteries were formed from hundreds of teeth which were stacked in rows upon rows and formed a grinding surface to process plant foods. [24] Histological study of these batteries found that they were not cemented together as previously thought, but that each tooth in the battery was separately moving and supported by ligamenture such that the whole structure was flexible. [9] [24] Comparable to shark teeth, dental batteries exhibited polyphyodonty, growing new teeth on the inside which migrated over time to replace the outer teeth. Unlike sharks however, who lose all of their old teeth, teeth in the rapidly growing dental battery would wear completely down and be reabsorbed by the renewing structure around it. [25]

The batteries were formed by the teeth growing fast and maturing early, to the point that the pulp cavity of individual teeth—usually filled with cells and connective tissue—were totally filled with dentine before it even erupted. The lack of pulp in the tooth post-eruption means that the tooth was essentially dead and able to be completely worn away through use, and replaced without the risk of exposing the normally sensitive dental pulp to infection and pain. While other dinosaurs, such as some ceratopsians and sauropods, also possessed dental batteries, they all evolved independently and differ in some form or function from those of hadrosaurs. This shows that some dinosaurs had evolved extremely sophisticated chewing capabilities. [24] [25]

Related Research Articles

<span class="mw-page-title-main">Human tooth</span> Calcified whitish structure in humans mouths used to break down food

Human teeth function to mechanically break down items of food by cutting and crushing them in preparation for swallowing and digesting. As such, they are considered part of the human digestive system. Humans have four types of teeth: incisors, canines, premolars, and molars, which each have a specific function. The incisors cut the food, the canines tear the food and the molars and premolars crush the food. The roots of teeth are embedded in the maxilla or the mandible and are covered by gums. Teeth are made of multiple tissues of varying density and hardness.

<span class="mw-page-title-main">Cementum</span> Specialized calcified substance covering the root of a tooth

Cementum is a specialized calcified substance covering the root of a tooth. The cementum is the part of the periodontium that attaches the teeth to the alveolar bone by anchoring the periodontal ligament.

<span class="mw-page-title-main">Tooth enamel</span> Major tissue that makes up part of the tooth in humans and many animals

Tooth enamel is one of the four major tissues that make up the tooth in humans and many animals, including some species of fish. It makes up the normally visible part of the tooth, covering the crown. The other major tissues are dentin, cementum, and dental pulp. It is a very hard, white to off-white, highly mineralised substance that acts as a barrier to protect the tooth but can become susceptible to degradation, especially by acids from food and drink. In rare circumstances enamel fails to form, leaving the underlying dentin exposed on the surface.

<span class="mw-page-title-main">Dentin</span> Calcified tissue of the body; one of the four major components of teeth

Dentin or dentine is a calcified tissue of the body and, along with enamel, cementum, and pulp, is one of the four major components of teeth. It is usually covered by enamel on the crown and cementum on the root and surrounds the entire pulp. By volume, 45% of dentin consists of the mineral hydroxyapatite, 33% is organic material, and 22% is water. Yellow in appearance, it greatly affects the color of a tooth due to the translucency of enamel. Dentin, which is less mineralized and less brittle than enamel, is necessary for the support of enamel. Dentin rates approximately 3 on the Mohs scale of mineral hardness. There are two main characteristics which distinguish dentin from enamel: firstly, dentin forms throughout life; secondly, dentin is sensitive and can become hypersensitive to changes in temperature due to the sensory function of odontoblasts, especially when enamel recedes and dentin channels become exposed.

<span class="mw-page-title-main">Periodontal fiber</span> Group of specialized connective tissue fibers

The periodontal ligament, commonly abbreviated as the PDL, is a group of specialized connective tissue fibers that essentially attach a tooth to the alveolar bone within which it sits. It inserts into root cementum on one side and onto alveolar bone on the other.

<span class="mw-page-title-main">Enamel organ</span> Aggregate of cells involved in tooth development

The enamel organ, also known as the dental organ, is a cellular aggregation seen in a developing tooth and it lies above the dental papilla. The enamel organ which is differentiated from the primitive oral epithelium lining the stomodeum. The enamel organ is responsible for the formation of enamel, initiation of dentine formation, establishment of the shape of a tooth's crown, and establishment of the dentoenamel junction.

<span class="mw-page-title-main">Human tooth development</span> Process by which teeth form

Tooth development or odontogenesis is the complex process by which teeth form from embryonic cells, grow, and erupt into the mouth. For human teeth to have a healthy oral environment, all parts of the tooth must develop during appropriate stages of fetal development. Primary (baby) teeth start to form between the sixth and eighth week of prenatal development, and permanent teeth begin to form in the twentieth week. If teeth do not start to develop at or near these times, they will not develop at all, resulting in hypodontia or anodontia.

<span class="mw-page-title-main">Dental papilla</span>

In embryology and prenatal development, the dental papilla is a condensation of ectomesenchymal cells called odontoblasts, seen in histologic sections of a developing tooth. It lies below a cellular aggregation known as the enamel organ. The dental papilla appears after 8–10 weeks intra uteral life. The dental papilla gives rise to the dentin and pulp of a tooth.

<span class="mw-page-title-main">Dental follicle</span>

The dental follicle, also known as dental sac, is made up of mesenchymal cells and fibres surrounding the enamel organ and dental papilla of a developing tooth. It is a vascular fibrous sac containing the developing tooth and its odontogenic organ. The dental follicle (DF) differentiates into the periodontal ligament. In addition, it may be the precursor of other cells of the periodontium, including osteoblasts, cementoblasts and fibroblasts. They develop into the alveolar bone, the cementum with Sharpey's fibers and the periodontal ligament fibers respectively. Similar to dental papilla, the dental follicle provides nutrition to the enamel organ and dental papilla and also have an extremely rich blood supply.

<span class="mw-page-title-main">Polyphyodont</span> Animal whose teeth are continually replaced

A polyphyodont is any animal whose teeth are continually replaced. In contrast, diphyodonts are characterized by having only two successive sets of teeth.

<span class="mw-page-title-main">Epithelial root sheath</span>

The Hertwig epithelial root sheath (HERS) or epithelial root sheath is a proliferation of epithelial cells located at the cervical loop of the enamel organ in a developing tooth. Hertwig epithelial root sheath initiates the formation of dentin in the root of a tooth by causing the differentiation of odontoblasts from the dental papilla. The root sheath eventually disintegrates with the periodontal ligament, but residual pieces that do not completely disappear are seen as epithelial cell rests of Malassez (ERM). These rests can become cystic, presenting future periodontal infections.

<i>Heterodontosaurus</i> Extinct genus of dinosaur from the early Jurassic of South Africa

Heterodontosaurus is a genus of heterodontosaurid dinosaur that lived during the Early Jurassic, 200–190 million years ago. Its only known member species, Heterodontosaurus tucki, was named in 1962 based on a skull discovered in South Africa. The genus name means "different toothed lizard", in reference to its unusual, heterodont dentition; the specific name honours G. C. Tuck, who supported the discoverers. Further specimens have since been found, including an almost complete skeleton in 1966.

<span class="mw-page-title-main">Dentinogenesis imperfecta</span> Medical condition

Dentinogenesis imperfecta (DI) is a genetic disorder of tooth development. It is inherited in an autosomal dominant pattern, as a result of mutations on chromosome 4q21, in the dentine sialophosphoprotein gene (DSPP). It is one of the most frequently occurring autosomal dominant features in humans. Dentinogenesis imperfecta affects an estimated 1 in 6,000-8,000 people.

<span class="mw-page-title-main">Odontoma</span> Benign tumour of dental tissue

An odontoma, also known as an odontome, is a benign tumour linked to tooth development. Specifically, it is a dental hamartoma, meaning that it is composed of normal dental tissue that has grown in an irregular way. It includes both odontogenic hard and soft tissues. As with normal tooth development, odontomas stop growing once mature which makes them benign.

<span class="mw-page-title-main">Gingival sulcus</span> Space between tooth and gums

The gingival sulcus is an area of potential space between a tooth and the surrounding gingival tissue and is lined by sulcular epithelium. The depth of the sulcus is bounded by two entities: apically by the gingival fibers of the connective tissue attachment and coronally by the free gingival margin. A healthy sulcular depth is three millimeters or less, which is readily self-cleansable with a properly used toothbrush or the supplemental use of other oral hygiene aids.

<span class="mw-page-title-main">Tooth</span> Hard, calcified structure found in the mouths of many vertebrates

A tooth is a hard, calcified structure found in the jaws of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tearing food, for defensive purposes, to intimidate other animals often including their own, or to carry prey or their young. The roots of teeth are covered by gums. Teeth are not made of bone, but rather of multiple tissues of varying density and hardness that originate from the outermost embryonic germ layer, the ectoderm.

<i>Criocephalosaurus</i> Extinct genus of therapsids

Criocephalosaurus is an extinct genus of tapinocephalian therapsids that lived in Southern Africa during the Guadalupian epoch of the Permian. They are the latest surviving dinocephalians, extending past the Abrahamskraal Formation into the lowermost Poortjie Member of the Teekloof Formation in South Africa. They are also regarded as the most derived of the dinocephalians, alongside Tapinocephalus, and the most abundant in the fossil record.

This glossary explains technical terms commonly employed in the description of dinosaur body fossils. Besides dinosaur-specific terms, it covers terms with wider usage, when these are of central importance in the study of dinosaurs or when their discussion in the context of dinosaurs is beneficial. The glossary does not cover ichnological and bone histological terms, nor does it cover measurements.

The grit, not grass hypothesis is an evolutionary hypothesis that explains the evolution of high-crowned teeth, particularly in New World mammals. The hypothesis is that the ingestion of gritty soil is the primary driver of hypsodont tooth development, not the silica-rich composition of grass, as was previously thought.

<i>Matheronodon</i> Extinct genus of dinosaurs

Matheronodon is a genus of rhabdodontid ornithopod dinosaur from the late Cretaceous Period of the Grès à Reptiles Formation in France. The genus contains a single species, M. provincialis, which is known from a single maxilla and associated teeth. It was named by Pascal Godefroit and colleagues in 2017. The teeth of Matheronodon are large but few in number. The teeth are also in an unusual arrangement, emerging alternatingly from one of a pair of fused tooth sockets in its mouth. In life, the teeth would have functioned like a pair of scissors, allowing Matheronodon to feed on the tough leaves of monocot plants.

References

  1. ↑ Hendrickx, Christophe; Mateus, Octávio; Araújo, Ricardo; Choiniere, Jonah (2019). "The distribution of dental features in non-avian theropod dinosaurs: Taxonomic potential, degree of homoplasy, and major evolutionary trends". Palaeontologia Electronica. 22 (3): 1–110. doi: 10.26879/820 . hdl: 11336/146011 .
  2. ↑ Chinsamy, Anusuya; Rich, T.; Vickers-Rich, P. (1998-06-15). "Polar dinosaur bone histology". Journal of Vertebrate Paleontology. 18 (2): 385–390. doi:10.1080/02724634.1998.10011066. ISSN   0272-4634.
  3. ↑ Martin Sander, P.; Mateus, Octávio; Laven, Thomas; Knötschke, Nils (2006). "Bone histology indicates insular dwarfism in a new Late Jurassic sauropod dinosaur". Nature. 441 (7094): 739–741. Bibcode:2006Natur.441..739M. doi:10.1038/nature04633. PMID   16760975. S2CID   4361820.
  4. ↑ Hübner, Tom R. (2012-01-06). "Bone Histology in Dysalotosaurus lettowvorbecki (Ornithischia: Iguanodontia) – Variation, Growth, and Implications". PLOS ONE. 7 (1): e29958. Bibcode:2012PLoSO...729958H. doi: 10.1371/journal.pone.0029958 . ISSN   1932-6203. PMC   3253128 . PMID   22238683.
  5. ↑ Zhao, Qi; Benton, Michael J.; Sullivan, Corwin; Sander, P. Martin; Xu, Xing (2013-06-28). "Histology and postural change during the growth of the ceratopsian dinosaur Psittacosaurus lujiatunensis". Nature Communications. 4: ncomms3079. Bibcode:2013NatCo...4.2079Z. doi: 10.1038/ncomms3079 . PMID   23811819.
  6. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Fong, R.K.M.; LeBlanc, A.R.; Berman, D.S.; Reisz, R.R. (2016). "Dental histology of Coelophysis bauri and the evolution of tooth attachment tissues in early dinosaurs". Journal of Morphology. 277 (7): 914–924. doi:10.1002/jmor.20545. PMID   27087142. S2CID   25916863.
  7. 1 2 3 Brink, K. S.; Reisz, R. R.; LeBlanc, A. R. H.; Chang, R. S.; Lee, Y. C.; Chiang, C. C.; Huang, T.; Evans, D. C. (2015-07-28). "Developmental and evolutionary novelty in the serrated teeth of theropod dinosaurs". Scientific Reports. 5 (1): 12338. Bibcode:2015NatSR...512338B. doi:10.1038/srep12338. ISSN   2045-2322. PMC   4648475 . PMID   26216577.
  8. ↑ Erickson, Gregory M.; Sidebottom, Mark A.; Kay, David I.; Turner, Kevin T.; Ip, Nathan; Norell, Mark A.; Sawyer, W. Gregory; Krick, Brandon A. (2015-06-01). "Wear biomechanics in the slicing dentition of the giant horned dinosaur Triceratops". Science Advances. 1 (5): e1500055. Bibcode:2015SciA....1E0055E. doi:10.1126/sciadv.1500055. ISSN   2375-2548. PMC   4640618 . PMID   26601198.
  9. 1 2 Erickson, Gregory M.; Krick, Brandon A.; Hamilton, Matthew; Bourne, Gerald R.; Norell, Mark A.; Lilleodden, Erica; Sawyer, W. Gregory (2012-10-05). "Complex Dental Structure and Wear Biomechanics in Hadrosaurid Dinosaurs". Science. 338 (6103): 98–101. Bibcode:2012Sci...338...98E. doi:10.1126/science.1224495. ISSN   0036-8075. PMID   23042891. S2CID   35186603.
  10. ↑ Sereno, Paul C.; Wilson, Jeffrey A.; Witmer, Lawrence M.; Whitlock, John A.; Maga, Abdoulaye; Ide, Oumarou; Rowe, Timothy A. (2007-11-21). "Structural Extremes in a Cretaceous Dinosaur". PLOS ONE. 2 (11): e1230. Bibcode:2007PLoSO...2.1230S. doi: 10.1371/journal.pone.0001230 . ISSN   1932-6203. PMC   2077925 . PMID   18030355.
  11. ↑ LeBlanc, Aaron R. H.; Reisz, Robert R. (2013-09-04). "Periodontal Ligament, Cementum, and Alveolar Bone in the Oldest Herbivorous Tetrapods, and Their Evolutionary Significance". PLOS ONE. 8 (9): e74697. Bibcode:2013PLoSO...874697L. doi: 10.1371/journal.pone.0074697 . ISSN   1932-6203. PMC   3762739 . PMID   24023957.
  12. 1 2 LeBlanc, Aaron R. H.; Brink, Kirstin S.; Cullen, Thomas M.; Reisz, Robert R. (2017-09-29). "Evolutionary implications of tooth attachment versus tooth implantation: A case study using dinosaur, crocodilian, and mammal teeth". Journal of Vertebrate Paleontology. 37 (5): e1354006. doi:10.1080/02724634.2017.1354006. ISSN   0272-4634. S2CID   91066137.
  13. ↑ Hwang, S.H. (2005). "Phylogenetic Patterns of Enamel Microstructure in Dinosaur Teeth". Journal of Morphology. 266 (2): 208–240. doi:10.1002/jmor.10372. PMID   16163689. S2CID   9973691.
  14. ↑ Dauphin, Y. (1988). "L'email dentaire des Reptiles actuels et fossiles : repartition de la structure prismatique, son rôle, ses implications". Palaeontographica. A203: 171–184.
  15. ↑ Dauphin, Y.; Jaeger, J.J.; Osmolska, H (1988). "Enamel microstructure of ceratopsian teeth (Reptilia, Archosauria)". Geobios. 21 (3): 319–327. doi:10.1016/s0016-6995(88)80056-1. ISSN   0016-6995.
  16. ↑ Dauphin, Y. (1991). "Chemical composition of reptilian teeth - 2. implications for paleodiets". Palaeontographica. A219: 97–105.
  17. ↑ Bocherens, H.; Brinkman, D.B.; Dauphin, Y.; Mariotti, A. (1994). "Microstructural and geochemical investigations on Late Cretaceous archosaur teeth from Alberta, Canada". Canadian Journal of Earth Sciences. 31 (5): 783–792. Bibcode:1994CaJES..31..783B. doi:10.1139/e94-071. ISSN   0008-4077.
  18. ↑ Dauphin, Y.; Williams, C. T. (2007). "The chemical compositions of dentine and enamel from recent reptile and mammal teeth—variability in the diagenetic changes of fossil teeth". CrystEngComm. 9 (12): 1252–1261. doi:10.1039/b708985f. ISSN   1466-8033.
  19. ↑ Dauphin, Y.; Williams, C. T. (2008). "Chemical composition of enamel and dentine in modern reptile teeth". Mineralogical Magazine. 72 (1): 247–250. Bibcode:2008MinM...72..247D. doi:10.1180/minmag.2008.072.1.247. ISSN   0026-461X. S2CID   129102736.
  20. 1 2 3 Erickson, G. M. (1996-12-10). "Incremental lines of von Ebner in dinosaurs and the assessment of tooth replacement rates using growth line counts". Proceedings of the National Academy of Sciences. 93 (25): 14623–14627. Bibcode:1996PNAS...9314623E. doi: 10.1073/pnas.93.25.14623 . ISSN   0027-8424. PMC   26184 . PMID   8962103.
  21. ↑ Richman, Joy M.; Handrigan, Gregory R. (2011-04-01). "Reptilian tooth development". Genesis. 49 (4): 247–260. doi: 10.1002/dvg.20721 . ISSN   1526-968X. PMID   21309070.
  22. ↑ Wood, Sarah A.; Strait, David S.; Dumont, Elizabeth R.; Ross, Callum F.; Grosse, Ian R. (2011). "The effects of modeling simplifications on craniofacial finite element models: The alveoli (tooth sockets) and periodontal ligaments". Journal of Biomechanics. 44 (10): 1831–1838. doi:10.1016/j.jbiomech.2011.03.022. PMID   21592483.
  23. ↑ Porro, Laura B.; Holliday, Casey M.; Anapol, Fred; Ontiveros, Lupita C.; Ontiveros, Lolita T.; Ross, Callum F. (2011-08-01). "Free body analysis, beam mechanics, and finite element modeling of the mandible of Alligator mississippiensis". Journal of Morphology. 272 (8): 910–937. doi:10.1002/jmor.10957. ISSN   1097-4687. PMID   21567445. S2CID   10762324.
  24. 1 2 3 4 LeBlanc, Aaron R. H.; Reisz, Robert R.; Evans, David C.; Bailleul, Alida M. (2016-07-28). "Ontogeny reveals function and evolution of the hadrosaurid dinosaur dental battery". BMC Evolutionary Biology. 16: 152. doi: 10.1186/s12862-016-0721-1 . ISSN   1471-2148. PMC   4964017 . PMID   27465802.
  25. 1 2 Bramble, Katherine; LeBlanc, Aaron R. H.; Lamoureux, Denis O.; Wosik, Mateusz; Currie, Philip J. (2017). "Histological evidence for a dynamic dental battery in hadrosaurid dinosaurs". Scientific Reports. 7 (1): 15787. Bibcode:2017NatSR...715787B. doi: 10.1038/s41598-017-16056-3 . PMC   5693932 . PMID   29150664.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.