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Tooth enamel microstructure of Revueltosaurus and Krzyzanowskisaurus (Reptilia:Archosauria) from the Upper Triassic Chinle Group, USA: Implications for function, growth, and phylogeny

Andrew B. Heckert and Jessica A. Miller-Camp

Plain Language Abstract

This is a study of microscopic tooth structures in two extinct Late Triassic (~225-210 million years old) reptiles. Revueltosaurus is thought to be more closely related to crocodiles and Krzyzanowskisaurus to dinosaurs and therefore birds. Using a scanning electron microscope (SEM) reveals extremely fine details of the enamel, or hardest and outermost, portion of the tooth. Similarities in the anatomical details of tooth enamel may mean that taxa are closely related, but could also simply imply that they used their teeth in similar ways and therefore may have had similar diets. Particularly interesting features of the enamel of both Revueltosaurus and Krzyzanowskisaurus are that the enamel is relatively thick, especially given the relatively small size of their teeth, and that they possess discontinuities (lines of incremental growth—similar in concept to tree rings) that may indicate that, while small, they maintained individual teeth in their dentition for long periods of time, a trait that is somewhat unusual among reptiles. The enamel of Krzyzanowskisaurus and Revueltosaurus is similar enough that they are probably closely related, but also displays evolutionary convergence with some dinosaurs.

Resumen en Español

Microestructura del esmalte dental de Revueltosaurus y Krzyzanowskisaurus (Reptilia, Archosauria) del Grupo Chinle (Triásico superior, EE.UU.): implicaciones para el análisis funcional, del crecimiento y de la filogenia

La microestructura del esmalte dental puede aportar importante información filogenética, ontogenética y funcional en los amniotas. En este trabajo se describe por primera vez la microestructura del esmalte dental de dos taxones del Triásico superior, el crurotarso Revueltosaurus callenderi Hunt y el generalmente aceptado como ornitisquio Krzyzanowskisaurus hunti (Heckert), que algunos autores consideran estrechamente emparentados. Para contrastar las hipótesis de que el grosor del esmalte depende de la función y/o de la filogenia, hemos analizado el esmalte de cada una de las especies a varias escalas, midiendo el grosor del esmalte y examinando las características microestructurales del esmalte tanto longitudinal como transversalmente, utilizando técnicas previamente establecidas para facilitar las comparaciones. Ambos taxones poseen esmaltes gruesos (hasta ~150μm) en relación con su tamaño (<20 mm de altura de la corona). El grosor del esmalte de R. callenderi varía entre ~5 y 152 μm en una sección longitudinal de un diente premaxilar y entre ~42 y 92 μm en una sección transversal de un diente maxilar/dentario. El espesor del esmalte de K. hunti varía entre ~18 y 155 μm en sección longitudinal y entre ~29 y 75 μm en sección transversal. Ambas especies muestran capas de la unidad basal bien desarrolladas y una microestructura columnar poco desarrollada. También son patentes en ambos taxones las líneas de crecimiento incremental, a lo largo de las cuales el esmalte columnar pasa gradualmente a esmalte paralelo. La microestructura de su esmalte es, por tanto, muy similar a la de varios taxones ornitisquios, especialmente los anquilosaurios, con los que muestran fuertes convergencias y también es comparable a la de los rauisuquios y tiranosáuridos. La combinación relativamente única de características microestructurales en el schmelzmuster de R. callenderi y K. hunti apoya la hipótesis de su parentesco cercano, aunque no excluye irrefutablemente la posibilidad de una posición taxonómica diferente para K. hunti, por lo que mantenemos una designación genérica separada.

PALABRAS CLAVE: arcosaurio; esmalte dental; microestructura; Triásico; Revueltosaurus; crurotarso

Traducción: Miguel Company

Résumé en Français

Microstructure de l'émail dentaire de Revueltosaurus et Krzyzanowskisaurus (Reptilia:Archosauria) du Trias supérieur du Groupe Chinle, USA : implications pour le fonctionnement, la croissance et la phylogénie.

La microstructure de l'émail des dents peut comporter des informations phyllogénétiques, ontogénétiques et fonctionnelles significatives chez les amniotes. Nous présentons ici les premières descriptions de la microstructure de l'émail dentaire de deux taxa du Trias supérieur, le crurotarsien Revueltosaurus callenderi Hunt et le supposé ornithischien Krzyzanowskisaurus hunti (Heckert), que certains considèrent comme de proches parents. Pour tester l'hypothèse que l'épaisseur de l'émail dépend du fonctionnement et/ou de la phylogénie, nous avons analysé l'émail de chacun des deux taxa à différentes échelles, mesurant l'épaisseur de l'émail et examinant les caractères microstructuraux au travers de sections transversales et longitudinales, utilisant des techniques établies pour faciliter les comparaisons. Les deux taxa possèdent un émail épais (jusqu'à ~150 µm) pour leur taille (< 20 mm de haute de couronne). L'émail chez R. callenderi varie de ~5 à 152 µm sur une section longitudinal d'une dent prémaxillaire, et de ~42 à 92 µm dans une section transverse de dent maxillaire/mandibulaire. L'épaisseur de l'émail de K. hunti était de ~18-155 µm longitudinalement et ~29-75 µm transversalement. Les deux avaient aussi les couches de l'unité de base (basal unit layers, BUL) bien développée, et des microstructures colonnaires faiblement développées. Des lignes de croissances bien développées (lines of incremental growth, LIG) sont présentes chez les deux taxa, au travers desquelles l'émail colonnaire évolue en émail cristallite parallèle. La microstructure de leur émail est donc grossièrement similaire à celles de plusieurs taxa ornithischiens, spécialement les ankylosaures, avec lesquels ils sont fortement convergents, et ressemble bien également aux rauisuchidés et tyrannosauridés. L'association relativement unique de caractéristiques microstructurale du schmelzmuster de R. callenderi et K. hunti supporte l'hypothèse qu'ils sont de proches parents, mais n'exclue pas définitivement une attribution taxinomique différent pour K. hunti, de fait nous le gardons sous une désignation générique séparée.

Mots clés : archosaure; émail dentaire; microstructure; Trias; Revueltosaurus; crurotarsien

Translator: Olivier Maridet

Deutsche Zusammenfassung

Zahnschmelz-Mikrostruktur von Revueltosaurus und Krzyzanowskisaurus (Reptilia:Archosauria) aus der obertriassischen Chinle Gruppe, USA: Auswirkungen auf Funktion, Wachstum und Phylogenie

Die Zahnschmelz-Mikrostruktur kann bei Amnioten maßgebliche Informationen zur Phylogenie, Ontogenese und Funktion liefern. Wir bieten die erste Beschreibung von Zahnschmelz-Mikrostruktur bei zwei spättriassischen Taxa, die einige als eng verwandt ansehen: der crurotarsale Revueltosaurus callenderi Hunt und der vermeintliche Ornitischier Krzyzanowskisaurus hunti (Heckert). Um die Hypothese zu testen, dass die Dicke des Zahnschmelzes der Funktion und/oder Phylogenie entspricht, haben wir den Schmelz der beiden in unterschiedlichen Maßstäben analysiert. Dabei haben wir die Zahnschmelzdicke gemessen, und mikrostrukturelle Eigenschaften sowohl über die Längs - als auch Querschnittsdicke untersucht. Um die Vergleiche zu vereinfache, benutzten wir vorher ermittelte Techniken.

Beide Taxa haben für ihre Größe (< 20 mm Kronenhöhe) einen dicken Schmelz (bis zu ~150 µm). Der Schmelz bei R. callenderi reichte von ~5-152 µm über einen Prämaxlliar-Zahn im Längsschnitt und ~42-92 µm bei einem Zahn im Maxillare/Dentale im Querschnitt. Der Schmelz von K. hunti hatte eine Dicke von ~18-155 µm im Längsschnitt und ~29-75 µm im Querschnitt. Beide hatten gut entwickelte Basal Unit Layers (BUL) und eine schwach entwickelte kolumnare Mikrostruktur. Die Schrittweise-Wachstumslinien (LIG) durch die der kolumnare Schmelz in den parallelen kristallinen Schmelz übergeht, sind bei beiden Taxa gut entwickelt. Ihr Schmelz ist daher grob dem einiger Ornitischier ähnlich, besonders Ankylosauriern, mit denen sie eine starke Konvergenz aufweisen und ebenso mit dem von Rauisuchiden und Tyrannosauriden. Die relativ einzigartige Kombination der mikrostrukturellen Charakteristika im Schmelzmuster von R. callenderi und K. hunti unterstützt die Hypothese einer engen Verwandtschaftsbeziehung. Damit ist jedoch eine unterschiedliche taxonomische Zuweisung von K. hunti nicht endgültig ausgeschossen, so dass wir die separate Gattungsbezeichnung beibehalten.

SCHLÜSSELWÖRTER: Archosaurier; Zahnschmelz; Mikrostruktur; Trias; Revueltosaurus; crurotarsal

Translators: Eva Gebauer

Arabic

319 arab

Translator: Ashraf M.T. Elewa

 

 

FIGURE 4. Scanning electron microscope images of NMMNH P-33799, Revueltosaurus callenderi premaxillary tooth showing variation in enamel microstructure in longitudinal section. 1, overview of tooth indicating approximate place where measurements and micrographs shown in this figure were taken; 2-8, close-up views showing enamel thickness variation, with enamel-dentine junction (EDJ) oriented relative to overview in (1) and outer enamel surface (OES) away from the same overview. White scale bars = 20 µm except for 1 (5 mm) and 4 (50 µm). Numbers in image are linked to further enlargements.

  fig4 1

FIGURE 4.2. Original micrograph showing tooth enamel microstructure of premaxillary tooth of Revueltosaurus callenderi (P-33799) in longitudinal section at the tip of the crown; EDJ oriented to left of picture.

 fig4 2

FIGURE 4.3. Original micrograph showing tooth enamel microstructure of premaxillary tooth of Revueltosaurus callenderi (P-33799) in longitudinal section near the tip of the crown; EDJ oriented to left of picture.

 fig4 3

FIGURE 4.4. Original micrograph showing tooth enamel microstructure of premaxillary tooth of Revueltosaurus callenderi (P-33799) in longitudinal section high on the crown; EDJ oriented to left of picture.

 fig4 4

FIGURE 4.5. Original micrograph showing tooth enamel microstructure of premaxillary tooth of Revueltosaurus callenderi (P-33799) in longitudinal section high on the crown; EDJ oriented to left of picture.

 fig4 5

FIGURE 4.6. Original micrograph showing tooth enamel microstructure of premaxillary tooth of Revueltosaurus callenderi (P-33799) in longitudinal section high on the crown; EDJ oriented to right of picture.

 fig4 6

FIGURE 4.7. Original micrograph showing tooth enamel microstructure of premaxillary tooth of Revueltosaurus callenderi (P-33799) in longitudinal section low on the tooth; EDJ oriented to left of picture.

 fig4 7

FIGURE 4.8. Original micrograph showing tooth enamel microstructure of premaxillary tooth of Revueltosaurus callenderi (P-33799) in longitudinal section near the middle of the tooth; EDJ oriented to left of picture.

fig4 8

 

FIGURE 3. Variation in enamel thickness in the teeth of Revueltosaurus callenderi 1-9, premaxillary tooth (P-33799--longitudinal section); 10-14, maxillary tooth (P-33798--transverse section). 1, overview of premaxillary tooth indicating approximate place where measurements and micrographs shown in this figure and Figure 4 were taken; 2-9, close-up views showing enamel thickness variation, with enamel-dentine junction (EDJ) oriented relative to overview in (1); and 10, overview of maxillary tooth section, indicating approximate place where measurements and micrographs shown in this figure and Figure 5 were taken; 11-14, close-up views showing enamel thickness variation, with enamel-dentine junction (EDJ) oriented relative to overview in (10). Scale bars = 100 µm except for 1 (5 mm), 2 (10 µm) and 10 (2 mm). Numbers in image are linked to further enlargements. Author note: Figure 3.10 is part of overview.

 

 

 

FIGURE 3.2. Original micrograph showing tooth enamel microstructure of premaxillary tooth of Revueltosaurus callenderi (P-33799) in longitudinal section near the base of the tooth; EDJ oriented to bottom of picture.

 fig3 2

 

FIGURE 3.3. Original micrograph showing tooth enamel microstructure of premaxillary tooth of Revueltosaurus callenderi (P-33799) in longitudinal section near the base of the tooth; EDJ oriented to bottom of picture.

 fig3 3

FIGURE 3.4. Original micrograph showing tooth enamel microstructure of premaxillary tooth of Revueltosaurus callenderi (P-33799) in longitudinal section near the middle of the tooth; EDJ oriented to bottom of picture.

 fig3 4

FIGURE 3.5. Original micrograph showing tooth enamel microstructure of premaxillary tooth of Revueltosaurus callenderi (P-33799) in longitudinal section near the middle of the tooth; EDJ oriented to bottom of picture.

 fig3 5

FIGURE 3.6. Original micrograph showing tooth enamel microstructure of premaxillary tooth of Revueltosaurus callenderi (P-33799) in longitudinal section high on the crown; EDJ oriented to bottom of picture.

 fig3 6

FIGURE 3.7. Original micrograph showing tooth enamel microstructure of premaxillary tooth of Revueltosaurus callenderi (P-33799) in longitudinal section at the tip of the crown; EDJ oriented to left of picture.

 fig3 7

FIGURE 3.8. Original micrograph showing tooth enamel microstructure of premaxillary tooth of Revueltosaurus callenderi (P-33799) in longitudinal section near the tip of the crown; EDJ oriented to bottom of picture.

 fig3 8

FIGURE 3.9. Original micrograph showing tooth enamel microstructure of premaxillary tooth of Revueltosaurus callenderi (P-33799) in longitudinal section near the base of the tooth; EDJ oriented to upper left of picture.

 fig3 9

FIGURE 3.10.

fig3 10

FIGURE 3.11. Original micrograph showing tooth enamel microstructure of maxillary tooth of Revueltosaurus callenderi (P-33798) in transverse section across one denticle.

 fig3 11

FIGURE 3.12. Original micrograph showing tooth enamel microstructure of maxillary tooth of Revueltosaurus callenderi (P-33798) in transverse section on labial side; EDJ to upper right.

 fig3 12

FIGURE 3.13. Original micrograph showing tooth enamel microstructure of maxillary tooth of Revueltosaurus callenderi (P-33798) in transverse section on lingual side; EDJ to bottom.

 fig3 13

FIGURE 3.14. Original micrograph showing tooth enamel microstructure of maxillary tooth of Revueltosaurus callenderi (P-33798) in transverse section on labial side; EDJ to bottom.

 fig3 14

 

FIGURE 5. Scanning electron microscope images of NMMNH P-33798, Revueltosaurus callenderi maxillary tooth enamel microstructure in transverse section. 1, overview of tooth indicating approximate place where measurements and micrographs shown in this figure were taken; 2-8, close-up views showing enamel thickness variation, with EDJ oriented relative to overview in (1) and OES away from the same overview. Scale bars = 20 µm except 1 (2 mm), 3 (50 µm). Numbers in image are linked to further enlargements.

  fig5 1

FIGURE 5.2. Original micrograph showing tooth enamel microstructure of maxillary tooth of Revueltosaurus callenderi (P-33798) in transverse section on labial side; EDJ to left.

 fig5 2

FIGURE 5.3. Original micrograph showing tooth enamel microstructure of maxillary tooth of Revueltosaurus callenderi (P-33798) in transverse section across one denticle; EDJ to right.

 fig5 3

FIGURE 5.4. Original micrograph showing tooth enamel microstructure of maxillary tooth of Revueltosaurus callenderi (P-33798) in transverse section on lingual side; EDJ to left.

 fig5 4

FIGURE 5.5. Original micrograph showing tooth enamel microstructure of maxillary tooth of Revueltosaurus callenderi (P-33798) in transverse section on lingual side; EDJ to left.

 fig5 5

FIGURE 5.6. Original micrograph showing tooth enamel microstructure of maxillary tooth of Revueltosaurus callenderi (P-33798) in transverse section on lingual side; EDJ to left.

 fig5 6

FIGURE 5.7. Original micrograph showing tooth enamel microstructure of maxillary tooth of Revueltosaurus callenderi (P-33798) in transverse section on lingual side; EDJ to left.

 fig5 7

FIGURE 5.8. Original micrograph showing tooth enamel microstructure of maxillary tooth of Revueltosaurus callenderi (P-33798) in transverse section on lingual side; EDJ to left.

fig5 8

 

FIGURE 1. Location map and stratigraphic section showing the geographic and stratigraphic distribution of Revueltosaurus and Krzyzanowskisaurus. This includes the localites of the Revueltosaurus (NMMNH locality 1) and Krzyzanowskisaurus (UCMP locality 7307) teeth described here. Tooth illustrations after Heckert (2002, 2005). LVF = land vertebrate faunachron (following Lucas et al., 2007); L-1171 = type location of Krzyzanowskisaurus hunti; PFV = locality yielding abundant Revueltosaurus fossils in the Petrified Forest National Park.

 figure 1

FIGURE 2. Generalized archosaurian phylogeny showing the relationships of taxa sampled by Sander (1999) and Hwang (2005) (in black) as well as Revueltosaurus (red) and Krzyzanowskisaurus (blue). Dashed lines demonstrate the two hypothesized positions of Krzyzanowskisaurus, either as a crurotarsan closely allied to Revueltosaurus (e.g., Parker et al., 2005; Irmis et al., 2007) or a basal ornithischian (Heckert, 2002, 2005).

 figure 2

FIGURE 3. Variation in enamel thickness in the teeth of Revueltosaurus callenderi. 1-9, premaxillary tooth (P-33799); 10-14, maxillary tooth (P-33798). 1, overview of premaxillary tooth indicating approximate place where measurements and micrographs shown in this figure and Figure 4 were taken; 2-9, close-up views showing enamel thickness variation, with enamel-dentine junction (EDJ) oriented relative to overview in (1); and 10, overview of maxillary tooth section, indicating approximate place where measurements and micrographs shown in this figure and Figure 5 were taken; 11-14, close-up views showing enamel thickness variation, with enamel-dentine junction (EDJ) oriented relative to overview in (10). Scale bars equal 100 µm except for 1 (5 mm), 2 (10 µm), and 10 (2 mm). Click to see image close-ups.

 figure 3

FIGURE 4. Scanning electron microscope images of NMMNH P-33799, Revueltosaurus callenderi premaxillary tooth showing variation in enamel microstructure in longitudinal section. 1, overview of tooth indicating approximate place where measurements and micrographs shown in this figure were taken; 2-8, close-up views showing enamel thickness variation, with enamel-dentine junction (EDJ) to the left and the outer enamel surface (OES) to the right. White scale bars = 20 µm except for 1 (5 mm) and 4 (50 µm). Click to see image close-ups.

 figure 4

FIGURE 5. Scanning electron microscope images of NMMNH P-33798, Revueltosaurus callenderi maxillary tooth enamel microstructure in transverse section. 1, overview of tooth indicating approximate place where measurements and micrographs shown in this figure were taken; 2-8, close-up views showing enamel thickness variation, with EDJ oriented relative to overview in (1) and OES away from the same overview. Scale bars equal 20 µm except 1 (2 mm), 3 (50 µm). Click to see image close-ups.

 figure 5

FIGURE 6. Scanning electron microscope images of UCMP 165213, Krzyzanowskisaurus hunti tooth enamel microstructure in longitudinal section. 1, overview of tooth indicating approximate place where measurements and micrographs shown in this figure were taken; 2-4, close-up views showing enamel thickness variation, with EDJ oriented relative to overview in (1) and OES away from the same overview. Scale bars equal 2 mm (1), 50 µm (2-3), and 100 µm (4). Click to see image close-ups. 

 figure 6

FIGURE 7. Scanning electron microscope images of UCMP 165211, Krzyzanowskisaurus hunti premaxillary tooth enamel microstructure in transverse section. 1, overview of tooth indicating approximate place where measurements and micrographs shown in this figure were taken; 2-7, close-up views showing enamel thickness variation, with EDJ oriented relative to overview in (1) and OES away from the same overview. Scale bar equals 20 µm except 1 (2 mm). Click to see image close-ups.

figure 7

 

FIGURE 7. Scanning electron microscope images of (UCMP 165211), Krzyzanowskisaurus hunti premaxillary tooth enamel microstructure in transverse section. 1, overview of tooth indicating approximate place where measurements and micrographs shown in this figure were taken; 2-7, close-up views showing enamel thickness variation, with EDJ oriented relative to overview in (1) and OES away from the same overview. Scale bars = 20 µm except 1 (2 mm). Numbers in image are linked to further enlargements.

  fig7 1

FIGURE 7.2. Original micrograph showing tooth enamel microstructure of (UCMP 165211), Krzyzanowskisaurus hunti in transverse section on the labial side; EDJ oriented to right of picture.

 fig7 2

FIGURE 7.3. Original micrograph showing tooth enamel microstructure of (UCMP 165211), Krzyzanowskisaurus hunti in transverse section on the labial side; EDJ oriented to left of picture.

 fig7 3

FIGURE 7.4. Original micrograph showing tooth enamel microstructure of (UCMP 165211), Krzyzanowskisaurus hunti in transverse section across a denticle; EDJ oriented to lower left of picture.

 fig7 4

FIGURE 7.5. Original micrograph showing tooth enamel microstructure of (UCMP 165211), Krzyzanowskisaurus hunti in transverse section across a denticle; EDJ oriented to left of picture.

fig7 5 

FIGURE 7.6. Original micrograph showing tooth enamel microstructure of (UCMP 165211), Krzyzanowskisaurus hunti in transverse section on the lingual side; EDJ oriented to left of picture.

 fig7 6

FIGURE 7.7. Original micrograph showing tooth enamel microstructure of (UCMP 165211), Krzyzanowskisaurus hunti in transverse section on the lingual side; EDJ oriented to left of picture.

fig7 7

 

FIGURE 6. Scanning electron microscope images of (UCMP 165213), Krzyzanowskisaurus hunti tooth enamel microstructure in longitudinal section. 1, overview of tooth indicating approximate place where measurements and micrographs shown in this figure were taken; 2-4, close-up views showing enamel thickness variation, with EDJ oriented relative to overview in (1) and OES away from the same overview. Scale bars = 2 mm (1), 50 µm (2-3), 100 µm (4). Numbers in image are linked to further enlargements.

  fig6 1

FIGURE 6.2. Original micrograph showing tooth enamel microstructure of (UCMP 165213), Krzyzanowskisaurus hunti in longitudinal section high on the crown; EDJ oriented to bottom of picture.

 fig6 2

FIGURE 6.3. Original micrograph showing tooth enamel microstructure of (UCMP 165213), Krzyzanowskisaurus hunti in longitudinal section high on the crown; EDJ oriented to bottom of picture.

 fig6 3

FIGURE 6.4. Original micrograph showing tooth enamel microstructure of (UCMP 165213), Krzyzanowskisaurus hunti in longitudinal section high on the crown; EDJ oriented to bottom of picture.

 fig6 4

 

TABLE 1. Comparison of tooth enamel thickness and enamel microstructural features in different archosauromorphs compiled from the literature.

Tooth Enamel Microstructure

Higher Taxon Taxon Sampler minimum
thickness
maximum
thickness
Parallel Columnar BUL LIG Wavy Tubules Comments

Archosauromorpha

Trilophosaurus

Sander (1999)

20

20

 

 

x

x

 

 

 

Crurotarsi

Phytosauridae (Dockum)

Sander (1999)

20

20

x

 

 

x

 

 

I and III

 

Phytosauridae (Dockum)

Sander (1999)

 

150

x

x

x

x

 

 

II

 

Phytosauridae (Hallau)

Sander (1999)

 

60

 

x

 

 

 

 

 

 

Rauisuchidae

Sander (1999)

60

100

x

x

x

x

 

 

95% columnar; outer is parallel; rare LIG

Mesosuchia

Machimosaurus hugi

Sander (1999)

 

350

x

x

x

 

 

 

LIG rare

Crocodylia: Alligatoridae

Allognathosuchus sp.

Sander (1999)

 

300

x

x

 

x

 

 

up to 50/50 columnar/parallel; sometimes 95/5; LIG only in parallel

 

Alligator mississippiensis

Sander (1999)

 

1000

x

x

x

x

 

 

Mostly columnar; LIG in columnar enamel

Crocodylia: Crocodylidae

Deinosuchus riograndensis

Sander (1999)

<150

525

 

x

x

 

 

 

40% columnar; 55% microunit; only specimen w/described microunits

 

Asiatosuchus

Sander (1999)

 

500

 

x

x

 

 

 

compound unit enamel/weakly columnar

 

Pristichampsa

Sander (1999)

20

50

x

x

 

x

 

 

LIG best in the carinae

 

Eusuchia indet

Sander (1999)

50

125

x

x

 

x

 

 

Columnar yields to parallel

Dinosauria:Saurischia: Theropoda

 

Basal Theropoda indet.

Hwang (2009)

 

 

x

x

x

 

 

x

100 µm average thickness; Kayenta Fm "carnosaur" in UCMP collections

D:S:T:Ceratosauria

Coelophysis bauri

Hwang (2005, 2011)

10

10

x

 

 

x

 

 

C. bauri of Hwang (2005) a distinct taxon (Hwang, 2011, p. 192)

 

Ceratosaurus nasicornis

Hwang (2011)

20

70

x

x

x

x

 

x

120 µm average thickness; varies wildly

 

Majungasaurus sp.

Hwang (2011)

<50

>90

x

x

x

x

 

x

 

D:S:T:Allosauroidea

Allosaurus fragilis

Hwang (2011)

20

>85

x

x

x

x

 

 

 

 

cf. Allosaurus

Sander (1999)

10

15

x

 

 

 

 

 

Not even LIG

 

Charcharodontosaurus

Buffetaut et al. (1986)

 

 

 

x

 

 

 

 

called "prisms" in published description

 

Spinosaurus

Buffetaut et al. (1986)

 

 

 

x

 

 

 

 

called "prisms" in published description

 

"Carnosaur"

Buffetaut et al. (1986)

 

 

x

?

x

 

 

 

 

D:S:T: Coelurosauria

 

 

 

 

 

x

 

 

 

 

 

D:S:T:C: Tyrannosauridae

Tyrannosauridae indet. (TX)

Sander (1999)

150

200

x

x

 

 

 

 

Thickest at base of carina; parallel only at the outer edge, great columnar

 

Tyrannosauridae indet. (MT)

Sander (1999)

 

120

x

x

x

 

 

 

 

 

Tyrannosauridae indet.

Hwang (2005, 2009)

 

 

x

x

x

 

 

x

115 µm average thickness

 

Tyrannosauridae indet. (="Nanotyrannus")

Hwang (2009)

 

 

x

x

 

 

 

x

60µm average thickness; juvenile tyrannosaurid assigned to "Nanotyrannus" in UWGM collections

 

Daspletosaurus torosus

Hwang (2011)

 

 

 

x

 

x

 

x

80 µm average thickness

 

cf. Gorgosaurus sp.

Hwang (2009)

 

 

x

x

x

 

 

x

80 µm average thickness

 

Gorgosaurus libratus

Hwang (2011)

 

 

x

x

x

x

 

x

 

 

Albertosaurus sarcophagus

Hwang (2005)

60

180

x

x

 

 

 

 

 

 

Albertosaurus sp.

Stokosa (2005)

100

120

x

x

 

 

 

x

 

 

?Albertosaurus gen. A. indet.

Stokosa (2005)

40

55

x

x

 

x

 

 

SDSM 12737; tip of tooth

 

?Albertosaurus gen. A. indet.

Stokosa (2005)

180

200

x

x

 

x

 

 

SDSM 15143

 

?Albertosaurus gen. A. indet.

Stokosa (2005)

95

100

x

x

 

x

 

 

SDSM 64351

 

Tyrannosaurus sp.

Hwang (2011)

 

 

 

x

 

 

 

x

200 µm average thickness

 

cf. Tyrannosaurus rex

Stokosa (2005)

45

50

x

x

 

x

 

x

SDSM 15135; Poorly developed columnar

 

cf. Tyrannosaurus rex

Stokosa (2005)

60

75

 

 

 

 

 

 

SDSM 64287

 

cf. Tyrannosaurus rex

Stokosa (2005)

80

90

 

 

 

 

 

 

SDSM 15115

 

Tarbosaurus

Dauphin et al. (1989)

 

 

 

x

 

 

 

 

intrepreted from pl. 2, fig. 4

 

Tarbosaurus

Hwang (2005)

 

300

x

x

 

 

 

 

 

D:S:T:C:incertae sedis

Richardoestesia cf. R. gilmorei

Stokosa (2005)

10

10

x

 

 

 

 

 

 

 

Richardoestesia gilmorei

Hwang (2011)

~10

~10

x

 

x

x

 

x

10 µm average thickness

 

Richardoestesia isosceles

Hwang (2011)

~13

~13

x

 

x

 

 

x

13 µm average thickness

 

Richardoestesia sp.

Stokosa (2005)

10

15

x

 

 

 

 

 

 

D:S:T:C:Maniraptora

Troodontid indet. A

Hwang (2005)

 

60

x

 

 

 

 

 

 

 

Troodontid indet. B

Hwang (2005)

 

 

x

x

 

 

 

 

 

 

Troodontid n. gen. et. Sp.

Hwang (2005)

 

30

x

 

 

x

 

 

 

 

Troodon sp.

Sander (1999)

 

20

x

x

x

 

 

 

Columnar units small (2µm) and weak, seem to arise from BUL (Sander, p. 65)

 

Troodon sp.

Hwang (2009, 2011)

 

 

x

 

x

 

 

 

20µm average thickness; parallel crystallites

 

Troodon sp. cf. T. formosus

Stokosa (2005)

10

15

x

 

 

 

 

 

 

 

Paronychodon cf. P. lacustris

Stokosa (2005)

0

15

x

 

 

 

 

 

 

 

Paronychodon lacustris

Sander (1999)

 

20

x

 

 

x

 

 

LIG are few and weak

 

Paronychodon (Troodontid)

Hwang (2005)

 

 

x

 

 

x

 

 

 

 

Byronosaurus jaffei

Hwang (2005)

 

13

x

 

 

x

 

 

 

 

Paronychodon (Dromaeosaurid)

Hwang (2005)

 

 

 

 

 

 

 

 

 

 

Velociraptor

Dauphin et al. (1989)

 

 

x

 

 

 

 

 

interpreted from pl. 1, figs. 4-5

 

Velociraptor mongoliensis

Hwang (2005)

 

24

x

 

x

 

 

 

 

 

Bambiraptor feinbergi

Hwang (2005)

 

 

x

 

 

x?

 

 

No LIG in Hwang (2005), but faint in Hwang (writ. Comm.)

 

Dromaeosauridae indet.

Hwang (2005)

 

55

x

 

x

 

 

 

 

 

Deinonychus antirrhopus

Hwang (2011)

17

30+

x

 

x

x

 

x

BUL poorly developed; LIG faint

 

Saurornitholestes sp.

Hwang (2011)

7

20+

x

 

x

 

 

x

BUL half of enamel thickness

 

Dromaemosaurus sp.

Hwang (2011)

25

35

x

 

x

x

 

x

BUL half of enamel thickness, but not well-developed

 

Dromaeosaurus sp. cf. D. albertensis

Stokosa (2005)

40

45

x

x

 

x

 

 

Columnar at EDJ, divergent parallel more at OES

D:S:T:Avialae

Indeterminate Avialan A

Hwang (2011)

 

 

x

 

x

 

 

x

20 µm average thickness

 

Indeterminate Avialan B

Hwang (2011)

 

 

x

 

x

 

 

x

16 µm average thickness

Sauropodomorpha

 

Plateosaurus engelhardti

Sander (1999)

10

40

x

?

 

x

 

 

Columnar is very poorly developed; probably more divergent parallel

 

cf. Diplodocus

Sander (1999)

 

150

 

 

x

 

 

 

Pseudo-wavy (Sander, p. 68)

 

Diplodocus longus

Hwang (2011)

440

490

 

x

x

x

 

x

465 µm average thickness

 

Camarasaurus sp.

Hwang (2011)

700

1000+

x

x

x

x

 

 

850 µm average thickness

 

Titanosauridae indet.

Hwang (2011)

 

 

x

x

x

x

 

x

170 µm average thickness

Dinosauria:Ornithischia

D:O:Stegosauria

Stegosaurus sp.

Hwang (2011)

 

 

x

 

x

x

 

 

30-40 µm average thickness

D:O:Ankylosauria

Ankylosauria indet.

Sander (1999)

 

60

 

x

x

 

 

 

 

 

Ankylosaurus magniventris

Hwang (2005)

 

60

x

x

x

x

 

 

 

 

Edmontonia rugosidens

Hwang (2005)

 

100+

x

x

x

x

 

 

 

 

Sauropelta edwardsi

Hwang (2005)

 

105

x

x

x

x

 

 

 

 

Euplocephalus

Hwang (2009, 2011)

35

65

x

x

x

x

 

x

55 µm average thickness; originally identified as a pachycephalosaurid

Dinosauria:Ornithischia:Euornithopoda

D:O:E: Hypsilophodontidae

Thescelosaurus sp.

Sander (1999)

14

140

x

 

x

 

 

 

BUL thin

 

Thescelosaurus sp.

Hwang (2011)

20

90

x

x

x

 

 

x

Hwang (2011) suspects Sander's (1999) specimen is not Thescelosaurus

D:O:E:Dryomorpha

Dryosaurus altus

Hwang (2011)

 

 

 

 

x

x

x

x

55-65 µm average thickness

 

Camptosaurus dispar

Hwang (2011)

 

 

 

 

x

 

x

x

 

D:O:E: Iguanodontidae

Iguanodon sp.

Sander (1999)

100

150

 

 

x

 

x

 

Inner and outer wavy enamel

 

Tenontosaurus tilleti

Hwang (2005)

 

100+

x

x

x

 

 

x

 

D:O:E: Hadrosauridae

Hadrosauridae indet.

Sander (1999)

160

210

 

 

x

 

x

 

 

 

Hadrosaurinae indet.

Hwang (2009)

 

 

 

x

 

 

 

x

 

 

Anatosaurus sp.

Sander (1999)

100

100+

 

 

x

 

x

x

BUL inverted

 

Saurolophus sp.

Hwang (2011)

 

165+

 

 

x

 

x

 

115 µm average thickness

 

Gilmoreosaurus mongoliensis

Hwang (2005)

 

 

 

 

x

 

x

 

 

 

Bactrosaurus johnsoni

Hwang (2005)

 

 

 

 

x

 

x

 

 

 

Kritosaurus navajovius

Hwang (2005)

 

 

 

 

x

 

x

 

 

 

Hypacrosaurus altispinus

Hwang (2005)

 

 

 

 

x

 

x

 

 

 

Corythosaurus casuaris

Hwang (2005)

 

 

 

 

x

 

x

 

 

 

Prosaurolophus maximus

Hwang (2011)

 

~200

 

 

x

 

x

 

135 µm average thickness

Dinosauria:Ornithischia: Ceratopsia

 

Neoceratopsia indet.

Hwang (2009)

 

 

 

x

 

 

 

 

Average 285 µm; originally assigned to Thescelosaurus sp.

 

Psittacosaurus sp.

Hwang (2005)

 

 

 

x

x

 

 

?

enamel voids

 

Protoceratops

Dauphin et al. (1988)

 

 

x

x

x

 

 

 

interpreted from pl. 1, figs. 7-8 (maxilla) and 12 (premaxilla)

 

Leptoceratops gracilis

Hwang (2005)

 

420

 

x

x

 

 

x

 

 

Protoceratops sp.

Hwang (2005)

 

120+

 

x

x

 

 

x

 

D:O:C:Ceratopsidae

Ceratopsidae indet. (Can)

Sander (1999)

150

 

 

x

x

x

 

x

 

 

Ceratopsidae indet. (WY)

Sander (1999)

 

 

 

 

 

 

 

 

 

 

Triceratops sp.

Hwang (2005)

 

325

 

x

x

 

 

x

 

 

Centrosaurus apertus

Hwang (2011)

 

 

 

x

x

x

 

x

170-270 µm average thickness depending on position

 

Pachyrhinosaurus canadensis

Hwang (2011)

 

 

 

x

x

x

 

x

170-270 µm average thickness depending on position

Dinosauria:Ornithischia:Pachycephalosauridae

 

Pachycephalosauridae indet. A

Hwang (2005)

 

20

x

 

 

 

 

 

anterior tooth, diverging parallel

 

Pachycephalosauridae indet. B

Hwang (2005)

 

40

x

x

x

 

 

 

posterior tooth, incipient columnar

 

Pachycephalosauridae indet. C

Hwang (2005)

 

50

x

x

x

 

 

 

posterior tooth, incipient columnar

TABLE 2. Measurements of enamel thickness in the teeth of Revueltosaurus and Krzyzanowskisaurus sampled here.

Revueltosaurus callenderi enamel measurements from longitudinal section of NMMNH P-33798

 

 

 

 

Figure

Section

Enamel thickness (µm)

Measured at:

3.2

Longitudinal

4.87

end of [full width of] enamel (thinnest enamel)

3.3

Longitudinal

20.42

middle of frame

3.4

Longitudinal

36.23

middle of frame

3.5

Longitudinal

68.48

middle of frame

3.6

Longitudinal

115.56

top of frame (thickest enamel)

3g

Longitudinal

114.88

left of frame (thickest enamel)

3h

Longitudinal

152.13

bottom of frame (thickest enamel)

3i

Longitudinal

103.34

middle of frame

4.2

Longitudinal

46.88

middle of frame

4.3

Longitudinal

50.08

middle of frame

4.4

Longitudinal

52.43

middle of frame

4.5

Longitudinal

53.93

middle of frame

4.6

Longitudinal

15.47

middle of frame

4.7

Longitudinal

31.36

middle of frame

4.8

Longitudinal

127.6

middle of frame

"Tooth has total crown height (TCH) of 13.1 mm, total crown length (TCL) 8.1 mm"

 

 

 

 

Revueltosaurus callenderi enamel measurements from transverse section of NMMNH P-33797

Figure

Section

Enamel thickness (µm)

Measured at:

3.11

Transverse

51.5

on denticle

3.12

Transverse

53.41

middle of frame

3.13

Transverse

55.15

middle of frame

3.14

Transverse

59.66

middle of frame

5.1

Transverse

42.8

left of frame (EDJ visible)

5.3

Transverse

92.47

middle of frame

5.4

Transverse

50.77

middle of frame

5.5

Transverse

54.48

middle of frame

5.6

Transverse

53.32

middle of frame

5.7

Transverse

62.79

middle of frame

5.8

Transverse

60.04

middle of frame

TCH: 6 mm+ (broken)

 

TCL: ~6 mm

 

 

 

 

 

Krzyzanowskisaurus hunti enamel measurements from longitudinal section of UCMP 165213

Figure

Section

Enamel thickness (µm)

Measured at:

6.2

Longitudinal

112.8

middle of frame

6.3

Longitudinal

138.89

left of frame (EDJ visible)

6.4

Longitudinal

151.25

right of frame (unbroken outer edge of enamel)

TCH: ~6 mm (incomplete)

 

TCL: 6 mm

 

 

 

 

 

Krzyzanowskisaurus hunti enamel measurements from transverse sectionof UCMP 165211

 

 

 

 

Figure

Section

Enamel thickness (µm)

Measured at:

7.1

Transverse

55.38

middle of bend

7.2

Transverse

64.34

middle of frame

7.3

Transverse

50.49

middle of frame

7.4

Transverse

65.54

middle of frame

7.5

Transverse

63.38

middle of frame

7.6

Transverse

43.47

middle of frame

7.7

Transverse

61.82

middle of frame

TCH: ~10.4 mm

TCL: ~7.4 mm

 

 

 

 

This email address is being protected from spambots. You need JavaScript enabled to view it.">Andrew B. Heckert
andrewDepartment of Geology
Appalachian State University
ASU Box 32067
Boone, North Carolina 28608-2067
U.S.A.
website

Andrew Heckert earned a B.S. in Geology summa cum laude from Denison University in 1993 before earning an M.S. (1997) and Ph.D. (2001) from the Department of Earth & Planetary Sciences at the University of New Mexico. Subsequent to this he worked as the Geoscience Collections Manager at the New Mexico Museum of Natural History (2002-2005) before taking a post at Appalachian State University, where he is an associate professor in geology and director of the McKinney Geology Teaching Museum.

Heckert's research interests revolve around Late Triassic stratigraphic, biostratigraphic, and paleontologic issues, focusing primarily on microvertebrates, but he enjoys ranging up and down the section, and has collected vertebrates ranging in age from Devonian to Pleistocene, conducting field work across the American West and now in his new home state of North Carolina.

Photo by Alan Erickson.

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This email address is being protected from spambots. You need JavaScript enabled to view it.">Jessica A. Miller-Camp
ymy2Department of Geology
Appalachian State University
ASU Box 32067
Boone, North Carolina 28608-2067, U.S.A.
currently: Department of Geoscience
121 Trowbridge Hall
University of Iowa
Iowa City, Iowa, 52242
U.S.A.

Jessica Miller-Camp earned a B.S. in Geology from Appalachian State University in 2007 where she studied the tooth enamel microstructure of several archosaurs. Since then she earned an M.S. in Geoscience at the University of Iowa (2010) for a geometric morphometrics study of the dicynodont Lystrosaurus. She is currently enrolled as a Ph.D. student at the University of Iowa undertaking a dissertation on the phylogenetics, taxonomy, biogeography, and morphology of Alligatorinae.