“…Several studies have focused on the hard tissues -enamel and dentine—and their phylogenetic and functional significance [ 4 , 19 – 22 ], but the field has steadily broadened to include more holistic descriptions and comparisons of teeth, their constituent tissues, and their interactions with the jaws. The result has been a broader picture of how teeth and jaws have evolved in association with dietary shifts and what developmental processes could have given rise to novel dentitions [ 2 , 5 , 7 – 9 , 13 , 14 , 17 , 23 – 26 ]. Some of the most dramatic and most studied evolutionary innovations are found in derived ornithischian dinosaurs.…”
The great diversity of dinosaurian tooth shapes and sizes, and in particular, the amazing dental complexity in derived ornithischians has attracted a lot of attention. However, the evolution of dental batteries in hadrosaurids and ceratopsids is difficult to understand without a broader comparative framework. Here we describe tooth histology and development in the "middle" Cretaceous ornithischian dinosaur Changchunsaurus parvus, a small herbivore that has been characterized as an early ornithopod, or even as a more basal ornithischian. We use this taxon to show how a "typical" ornithischian dentition develops, copes with wear, and undergoes tooth replacement. Although in most respects the histological properties of their teeth are similar to those of other dinosaurs, we show that, as in other more derived ornithischians, in C. parvus the pulp chamber is not invaded fully by the newly developing replacement tooth until eruption is nearly complete. This allowed C. parvus to maintain an uninterrupted shearing surface along a single tooth row, while undergoing continuous tooth replacement. Our histological sections also show that the replacement foramina on the lingual surfaces of the jaws are likely the entry points for an externally placed dental lamina, a feature found in many other ornithischian dinosaurs. Surprisingly, our histological analysis also revealed the presence of wavy enamel, the phylogenetically earliest occurrence of this type of tissue. This contradicts previous interpretations that this peculiar type of enamel arose in association with more complex hadrosauroid dentitions. In view of its early appearance, we suggest that wavy enamel may have evolved in association with a shearing-type dentition in a roughly symmetrically-enameled crown, although its precise function still remains somewhat of a mystery.
“…Several studies have focused on the hard tissues -enamel and dentine—and their phylogenetic and functional significance [ 4 , 19 – 22 ], but the field has steadily broadened to include more holistic descriptions and comparisons of teeth, their constituent tissues, and their interactions with the jaws. The result has been a broader picture of how teeth and jaws have evolved in association with dietary shifts and what developmental processes could have given rise to novel dentitions [ 2 , 5 , 7 – 9 , 13 , 14 , 17 , 23 – 26 ]. Some of the most dramatic and most studied evolutionary innovations are found in derived ornithischian dinosaurs.…”
The great diversity of dinosaurian tooth shapes and sizes, and in particular, the amazing dental complexity in derived ornithischians has attracted a lot of attention. However, the evolution of dental batteries in hadrosaurids and ceratopsids is difficult to understand without a broader comparative framework. Here we describe tooth histology and development in the "middle" Cretaceous ornithischian dinosaur Changchunsaurus parvus, a small herbivore that has been characterized as an early ornithopod, or even as a more basal ornithischian. We use this taxon to show how a "typical" ornithischian dentition develops, copes with wear, and undergoes tooth replacement. Although in most respects the histological properties of their teeth are similar to those of other dinosaurs, we show that, as in other more derived ornithischians, in C. parvus the pulp chamber is not invaded fully by the newly developing replacement tooth until eruption is nearly complete. This allowed C. parvus to maintain an uninterrupted shearing surface along a single tooth row, while undergoing continuous tooth replacement. Our histological sections also show that the replacement foramina on the lingual surfaces of the jaws are likely the entry points for an externally placed dental lamina, a feature found in many other ornithischian dinosaurs. Surprisingly, our histological analysis also revealed the presence of wavy enamel, the phylogenetically earliest occurrence of this type of tissue. This contradicts previous interpretations that this peculiar type of enamel arose in association with more complex hadrosauroid dentitions. In view of its early appearance, we suggest that wavy enamel may have evolved in association with a shearing-type dentition in a roughly symmetrically-enameled crown, although its precise function still remains somewhat of a mystery.
“…1K–N ). The CT sections reveal no internal interalveolar septa within the premaxilla, unlike what is observed in most sauropods 25 . Figure 1 Liaoceratops yanzigouensis premaxillary teeth of IVPP V12738 ( A – F ), IVPP V12633 ( G – J ) and CAGS-IG-VD-002 ( M – R ).…”
Section: Methodsmentioning
confidence: 55%
“…The cross sections become mesiodistally compressed and have a relatively small apical opening. The roots display incipiently developed grooves along the mesial and distal surfaces, which are seen in more derived neoceratopsians 25 . In the holotype specimen, strong root resorption is seen in left functional teeth 5, 7, 10, and 12 in lingual view by 3D reconstruction (Fig.…”
Section: Methodsmentioning
confidence: 98%
“…From the reconstruction of Zahnreihen, a Z-spacing can be retrieved 14 , 20 – 24 . The Z-spacing represents the distance between the cycles of tooth replacement along the jaws 25 . It is measured as the distance of a tooth in replacement wave to the posterior following Zahnreihen.…”
Section: Introductionmentioning
confidence: 99%
“…Previous tooth replacement data in dinosaurs come principally from theropods 8 , and sauropodomorphs 3 , 4 , 9 , 22 , 25 , 30 , 32 – 40 . The tooth replacement pattern is inferred from the degree of wear plus root resorption and the relative height of the root 30 , 34 .…”
The dental morphology and tooth replacement pattern of Liaoceratops yanzigouensis, the earliest known neoceratopsian, are important for our understanding of the evolution of the ceratopsian dental system. Here we describe the dental morphology and tooth replacement of Liaoceratops yanzigouensis based on high-resolution computed tomographic (CT) scan data of three specimens including the holotype, the first study for basal ceratopsian. The three-dimensional reconstructions reveal some important new information, including: three teeth in the premaxilla in one side, two more teeth in the dentary than in the maxilla, incipiently developed mesial grooves on some crowns, two generations of replacement teeth within some tooth families; and most functional teeth were under heavy resorption by the replacement process, but still remained functional. Comparisons of tooth pair positions from opposite sides in the four jaw quadrants of three specimens revealed a degree of bilateral symmetry in replacement pattern. Reconstruction of Zahnreihen yields an avergae z-spacing of 2.58 with simultaneous front-to-back tooth replacement. Our study presents the earliest evidence of derived neoceratopsian traits of the complex dental batteries in ceratopsids. Most significantly, our models reveal the tracts of partially resorbed functional teeth which appears to track the growth of the jaws, traits previously undocumented in Ceratopsia.
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