Labial Tooth Research Articles

Smooth, striated, or rough: how substrate textures affect the feeding performance of tadpoles with different oral morphologies

For grazing animals that share spatial and alimentary resources, the relationship between differences in oral morphology and the physical properties of substrates can help explain how and where species forage. The substrates may require different efforts from animals to access and remove food from their surfaces. Variation in oral morphology may produce differences in animals’ feeding efficiency. We tested whether one substrate characteristic, the surface texture (i.e., smooth, striated and rough), influences the growth and food consumption rates of anuran larvae from nine species with different oral morphologies. Tadpoles with few keratinized oral structures and those with more gaps in the marginal papillae row were more efficient grazing on smooth and rough surfaces, respectively. This may indicate possible feeding specializations. Conversely, tadpoles with a high number of labial tooth rows, regardless of the number of gaps in these structures, and those with only a dorsal gap in the marginal papillae row were equally efficient feeding upon all substrate textures. Tadpoles with the generalized labial tooth row formula 2(2)/3(1), had higher growth rates than the other species, suggesting an adaptive significance for this common oral morphology. We demonstrated that species differ in feeding efficiency when grazing on substrates with different textures. This can help elucidate the adaptive significance of variation in tadpole oral morphology. We also provide insights on resource selection and niche partitioning among species, especially for those whose diets do not differ in quantity or quality, as it is common in anuran larval assemblages.

Failure Load of Maxillary Central Incisor Restored with CAD/CAM Endocrown Using Different Designs

Statement of problem: Restoration of a severely destructed non-vital tooth is usually challenging, especially, in case of incomplete circumferential tooth structures. Materials and methods: Sixty intact maxillary central incisors were collected. All teeth were decoronated leaving 2 mm above the CEJ then were divided into two divisions (30 specimens for each) according to the radicular depth (2 mm &4 mm). Each division was divided into three groups (10 specimens for each) according to residual coronal tooth structures (circumferential, only labial and only palatal) to obtain six groups of testing. Then milling was done for (IPS e.max CAD) followed by final cementation. Fracture resistance was tested using a universal testing machine. Results: Specimens restored with endocrowns having 2 mm radicular length, exhibited fracture resistance better than that with 4 mm radicular length, without statistical significant difference. Endocrowns with 2 mm circumferential residual coronal tooth structures in both radicular lengths exhibited fracture resistance better than that having either labial or palatal residual coronal tooth structures with a statistically significant difference. The specimens having 2 mm labial residual coronal tooth structures in each radicular length exhibited fracture resistance better than that with 2 mm palatal residual coronal tooth structures in each radicular length with a statistically significant difference. Conclusion: For restored endodontically treated maxillary central incisor by endocrown: residual 2 mm circumferential wall presented better fracture resistance than that with only residual labial or palatal wall and residual labial wall presented better fracture resistance than the palatal wall.

Ontogenetic development of the oral apparatus and oropharyngeal cavity in bullfrog tadpoles (Lithobates catesbeianus, Shaw 1802)

ObjectiveThe present study aimed to describe the morphology of oral apparatus and oral cavity of bullfrog tadpoles during their development and metamorphosis. DesignThe oral apparatus and oropharyngeal cavity of tadpoles from hatching up to metamorphosis stage was dissected for further analysis. These structures were fixed in Karnovsky solution, afterwards in osmium tetroxide and metalized in palladium gold and electron-micrographed using the scanning electron microscope. ResultsThe development of oral apparatus started with the formation and keratinization of the jaw sheaths and labial teeth followed by the formation of marginal and sub-marginal papillae. Degeneration of oral apparatus and formation of mouth was observed during metamorphosis. From stage-42 (metamorphic climax) to stage-43, the jaw sheath and labial tooth rows were disappeared progressively while the size and number of labial papillae were decreased. At stage-44, mouth formation started with the development of anterior and posterior labium though the labial papillae were still present. At stage-45 and 46, mouth was already formed, being very similar to the adult and characterized by the progressive increase in size. ConclusionThe sequence of events that happen during the development of oral apparatus of Lithobates catesbeianus Shaw, 1802 tadpoles follows the same pattern as occur in other anuran species but metamorphic atrophy of the oral apparatus follows the sequence of morphogenesis.

Dental trauma on primary teeth at different root resorption stages-A dynamic finite element impact analysis of the effect on the permanent tooth germ.

Dental trauma is a common emergency in children with primary teeth. The aim of this study was to determine stress propagation to the permanent tooth germ and surrounding bone and soft tissues during dental trauma to primary central incisors with three levels of physiological root resorption. Stresses were determined using finite element analysis (FEA). Cross-sectional models were created using cone-beam computed tomography images of 3.5, 5, and 6years olds, representing three different physiological root resorption stages of a maxillary primary central incisor. The models included periodontal ligament, bone, and soft tissues. An impact with an asphalt block moving at 1m/s,was simulated for two impact two directions, frontal on the labial tooth surface, and on the incisal edge. Stresses and strains were recorded during impact. The impact caused stress concentrations in the surrounding bone and soft tissues and permanent tooth germ, regardless of the direction of impact and the primary tooth resorption stage. Impact stresses in dental follicles and surrounding bone increased in models with more physiological root resorption of the primary tooth. Incisal impact generated higher stress concentrations in surrounding bone and soft tissues and permanent tooth germ regardless of physiological root resorption stage. The primary incisor with no physiological root resorption showed high stress concentrations at its root apex. During impact to a primary incisor, stresses most significant for potential damage to the formation of permanent enamel and dentin were at the dental follicle and surrounding bone tissue with the three levels of physiological root resorption.

The larvae of two species of Bokermannohyla (Anura, Hylidae, Cophomantini) endemic to the highlands of central Brazil.

Bokermannohyla (tribe Cophomantini) is an endemic genus of Brazilian treefrogs containing 32 species arranged into four phenetic groups. The B. pseudopseudis group includes nine species, which are typically found in rupestrian ecosystems of disjunct Brazilian mountain ranges. Tadpoles have been shown to be important sources of information for the taxonomy of this genus, although careful analyses of character variation and descriptions of internal anatomy remain scarce. Since the first description of B. pseudopseudis tadpoles was based on a mixed series containing specimens of B. pseudopseudis and B. sapiranga, we describe the larvae of these two species from their type localities, including their external morphology, oral cavity, and skeletal system. Tadpoles of B. pseudopseudis are easily distinguished from those of B. sapiranga by aspects of their coloration and characters of their oral disc (more labial tooth rows, more numerous submarginal papillae and flaps with labial teeth). These morphological differences may be diagnostic for these two similar species, whereas their chondrocranium, hyobranchial apparatus, and oral cavity are alike, suggesting less variability in these character systems between closely related species. Finally, we provide the first comparison of data on the skeletal system of Bokermannohyla and other Cophomantini, highlighting characters of potential relevance to the systematics of the tribe.

Morphological and genetic characterization of Syphabulea tjanschani ( ) (Nematoda: Oxyuridae), with phylogenetic position of Syphabulea in Oxyuridae

Pinworms are important parasitic nematodes in animals and humans, and many species are of medical and veterinary importance. The genus Syphabulea is a poorly known group of pinworms. The systematic position of Syphabulea in Oxyuridae remains unclear. Moreover, there is still a paucity of detailed information on some morphological aspects of the type species S. tjanschani (Ablasov, 1962). In the present study, the detailed morphology of S. tjanschani was studied using light microscopy and, for the first time, scanning electron microscopy. The results revealed three traits useful for the characterization of the species including: cuticular depression around excretory pore, non-prominent labial teeth and number of adhesive ridges in three ventral mammelons. The ribosomal [small ribosomal DNA (18S), internal transcribed spacer (ITS) and large ribosomal DNA (28S)] and mitochondrial [cytochrome c oxidase subunit 1 (cox1)] target regions of S. tjanschani were also firstly amplified and sequenced for future use in the molecular identification of this poorly known species. In addition, in order to investigate the systematic position of Syphabulea in Oxyuridae, the phylogenetic analyses of representatives of the Oxyuridae were performed using maximum likelihood (ML) and maximum parsimony (MP) methods based on 18S, 28S and 18S + 28S + cox1 sequence data, respectively. The phylogenetic results based on different sequence data all supported the genus Syphabulea to be a member of the subfamily Syphaciinae. The phylogenetic analysis based on 28S sequence data also showed Syphabulea as sister to the genus Syphatineria. Our present study represents the first attempt to resolve the systematic position of the genus Syphabulea using phylogenetic analyses based on molecular data.

Labial Tooth Wear and Culture

Surface alterations observed on the anterior teeth of prehistoric humans suggest that incisors are involved in many uses related to ingestion, manipulations, and dental care activities. These culture-related uses can be distinguished in dental remains from throughout major periods of human evolution.

Tooth row variation in tadpoles of Dendropsophus labialis (Anura: Hylidae: Dendropsophini) and the evolution of oral morphology in the genus

Labial tooth row variation was assessed in Dendropsophus labialis tadpoles from the Cordillera Oriental in Colombia. The presence of a second anterior labial tooth row was detected, showing thus a labial tooth row formula of 2/2. This second anterior tooth row was present in a substantial number of individuals, suggesting that the observed variation is not unusual. This variation contradicts earlier reports about the number of labial tooth rows in this species, whose labial tooth row formula has been reported as 1/2 without variation. A novel ontogenetic pattern of tooth row addition was detected, differing from earlier observations made on Pseudacris regilla tadpoles in terms of tooth row appearance order. The taxonomic implications for these data are discussed along with the evolution of oral morphologies in the genus.

Assessment of the depth of cure of resin composite restoration by using Trans-tooth curing technique with different light curing intensities

Statement of problem: failure of resin composite restoration is most frequently caused by improper polymerization; it would be advantageous if the restoration possessed optimal depth of cure. Objective: The purpose of this study was to the depth of cure of resin composite restoration by using Trans-tooth curing technique with different light curing intensities Material and methods: A total of 20 sound, non-carious human maxillary anterior teeth, were used in this study. The teeth were divided into 2 main groups of 10 teeth each according to the thickness of the labial tooth structure plate (T); either 1.5 mm plate thickness (T1) or 1 mm plate thickness (T2). Each main group was subdivided into 2 subgroups of 5 teeth each according to the intensity of the light curing (I); either conventional intensity light curing (I1), or high intensity light curing (I2). Two Standardized class III cavity preparations were prepared in the proximals and lingual surfaces. Resin composite restorations were applied then all the teeth prepared for micro-hardness assessment. Data were explored for normality using Kolmogorov-Smirnov test of normality. The results of Kolmogorov-Smirnov test indicated that most of data were normally distributed (parametric data), therefore, one-way analysis of variance (ANOVA) test was used to compare between groups. This was followed by Tukey’s post hoc test and independent t test for pairwise comparisons. The significance level was set at p < 0.05. Results: Comparing all groups revealed that the highest mean value was recorded in High intensity curing (1.5 mm), whereas the lowest mean value was recorded in conventional intensity curing at 1.5 mm. ANOVA test revealed that the difference between all groups was statistically significant (P=0.001).Conclusions: Under the limitation of this in-vitro study it can be concluded that the thickness of the tooth structure as trans-tooth curing technique was applied is greatly affect the amount of light energy reached to the resin composite restoration. So therefore subsequently affect the degree of conversion of the composite restoration rather than the degree of light intensity.

Redescription of the Tadpole ofAmeerega hahneli(Boulenger, 1884) (Anura: Dendrobatidae) with Notes on Ontogenetic Variations and Development Habitats

Ameerega hahneli is a terrestrial dendrobatid frog widely distributed in the Amazon region. The tadpole of this species was formally described based on eight specimens in the early developmental stage 25, when some of the morphological structures were still not fully developed. In this study, the tadpoles of A. hahneli are redescribed based on 78 individuals in 14 different developmental stages. Additionally, we provide data on the ontogenetic variations and development sites of tadpoles. Specimens were collected in streamside ponds and streams of non-flooded forest during the rainy season. The tadpole of A. hahneli at stage 36 is characterized by: body elongate, depressed (lateral view), and oval (dorsal view); small size (mean 23.96 mm, range 21.7-26.2 mm); oral disc anteroventral; labial tooth row formulae 1/2; marginal papillae uniseriate, triangular, and distributed only on the lower labium. Like other tadpoles of the genus, the upper jaw sheath is W-shaped with a ventral notch and the lower jaw sheath is V-shaped, the spiracle is sinistral, and the vent tube is dextral. Ontogenetic variations were observed in body size, number of marginal papillae, lateral line system and ventral coloration. Total length increased gradually from the stage 25 (14.67 mm) to stage 37 (26.70 mm), the latter being the maximum total length observed. The combination of the morphological organization of its labial tooth row formulae and the presence of triangular marginal papillae only at the posterior labium allows the A. hahneli tadpoles to be easily distinguished from all the others species of the genus Ameerega.

External Morphology, Oral Structure and Feeding Behaviour of Kaloula pulchra TADPOLES Gray, 1831 (Amphibia: Anura: Microhylidae)

The external morphology and oral structure of various developmental stages in relation to feeding behaviour of Kaloula pulchra Gray, 1831 (Amphibia: Microhylidae) were studied with the help of light microscopyand scanning electron microscopy (SEM). Light and scanning electron micrographs revealed that the oral apparatus at different larval stages are devoid of jaw sheath, labial teeth and keratodonts, instead they have a terminally-oriented, as opposed to an antero-ventrally oriented mouth (umbelliform) known as semicircular labial flap. These features illustrate that the tadpoles within the family Microhylidae could be attributed to assistance in clarifying a certain taxonomic treatment in this family. Observation on the present results showed that tadpoles of Kaloula pulchra are nektonic suspension feeders and started feeding from stage 25 onwards. During the early stages of feeding, they feed mostly on detritus and plant materials and during the later stages of feeding they consumed both phytoplankton and zooplankton. At stage 42, the tadpole stopped feeding and the mouth part is degenerated and gradually transformed in to adult mouth. The preference of Bacillariophyceae and Cyanophyceae in the food habits of this explosive breeding species may be due to the common available food items in their microhabitat that enhanced the faster developmental rate within a short duration.

Impacts of UVB radiation on food consumption of forest specialist tadpoles

Solar ultraviolet radiation B (UVB) is an important environmental stressor for amphibian populations due to its genotoxicity, especially in early developmental stages. Nonetheless, there is an absence of works focused on the UVB effects on tadpoles’ food consumption efficiency. In this work, we investigated the effects of the exposure to a low environmental-simulated dose of UVB radiation on food consumption of tadpoles of the forest specialist Hypsiboas curupi [Hylidae, Anura] species. After UVB treatment tadpoles were divided and exposed to a visible light source or kept in the dark, in order to indirectly evaluate the efficiency of DNA repair performed by photolyases and nucleotide excision repair (NER), respectively. The body mass and the amount of food in tadpoles’ guts were verified in both conditions and these data were complemented by the micronuclei frequency in blood cells. Furthermore, the keratinized labial tooth rows were analyzed in order to check for possible UVB-induced damage in this structure. Our results clearly show that the body weight decrease induced by UVB radiation occurs due to the reduction of tadpoles’ food consumption. This behavior is directly correlated with the genotoxic impact of UVB light, since the micronuclei frequency significantly increased after treatments. Surprisingly, the results indicate that photoreactivation treatment was ineffective to restore the food consumption activity and body weight values, suggesting a low efficiency of photolyases enzymes in this species. In addition, UVB treatments induced a higher number of breaks in the keratinized labial tooth rows, which could be also associated with the decrease of food consumption. This work contributes to better understand the process of weight loss observed in tadpoles exposed to UVB radiation and emphasizes the susceptibility of forest specialist amphibian species to sunlight-induced genotoxicity.

Effect of labiolingual inclination of a maxillary central incisor and surrounding alveolar bone loss on periodontal stress: A finite element analysis.

ObjectiveThe aim of this study was to investigate whether labial tooth inclination and alveolar bone loss affect the moment per unit of force (Mt/F) in controlled tipping and consequent stresses on the periodontal ligament (PDL).MethodsThree-dimensional models (n = 20) of maxillary central incisors were created with different labial inclinations (5°, 10°, 15°, and 20°) and different amounts of alveolar bone loss (0, 2, 4, and 6 mm). The Mt/F necessary for controlled tipping (Mt/Fcont) and the principal stresses on the PDL were calculated for each model separately in a finite element analysis.ResultsAs labial inclination increased, Mt/Fcont and the length of the moment arm decreased. In contrast, increased alveolar bone loss caused increases in Mt/Fcont and the length of the moment arm. When Mt/F was near Mt/Fcont, increases in Mt/F caused compressive stresses to move from a predominantly labial apical region to a palatal apical position, and tensile stresses in the labial area moved from a cervical position to a mid-root position. Although controlled tipping was applied to the incisors, increases in alveolar bone loss and labial tooth inclination caused increases in maximum compressive and tensile stresses at the root apices.ConclusionsIncreases in alveolar bone loss and labial tooth inclination caused increases in stresses that might cause root resorption at the root apex, despite the application of controlled tipping to the incisors.

Morphological and microstructural changes of the oral apparatus in two Anuran tadpoles, in regard to pH

Scanning Electron Microscopy (SEM) and Light Microscopy (LM) of the oral apparatus of Polypedates teraiensis and Hylarana leptoglossa tadpoles revealed a number of morphological and microstructural alterations in the labial tooth rows, jaw sheaths and marginal papillae on exposure to acidic and alkaline pH. These morphological and microstructural alterations observed in the oral apparatus of the tadpole are discussed in the light of available literature. The significance of the study with reference to adverse effects of acidic as well as alkaline pH on oral apparatus of the tadpole is also discussed.

A new Dendropsophus Fitzinger, 1843 (Anura: Hylidae) of the parviceps group from the lowlands of the Guiana Shield.

Many Amazonian frog species that are considered widely distributed may actually represent polyspecific complexes.. A minute tree frog from the Guiana Shield originally assigned to the allegedly widely distributed Dendropsophus brevifrons proved to be a yet undescribed species within the D. parviceps group. We herein describe this new species and present a phylogeny for the D. parviceps group. The new species is diagnosed from other Dendropsophus of the parviceps group by its small body size (19.6-21.7 mm in males, 22.1-24.5 mm in females), thighs dorsally dark grey with cream blotches without bright yellow patch, absence of dorsolateral and canthal stripe, and an advertisement call comprising trills (length 0.30-0.35 s) composed of notes emitted at a rate of 131-144 notes/s, generally followed by click series of 2-3 notes. Its tadpole is also singular by having fused lateral marginal papillae and absence of both labial teeth and submarginal papillae. Genetic distances (p-distance) are &gt;5.3% on the 12S and &gt;9.3% on the 16S from D. brevifrons, its closest relative. This species occurs from the Brazilian state of Amapá, across French Guiana and Suriname to central Guyana and is likely to also occur in adjacent Brazilian states and eastern Venezuela. This species is not rare but is difficult to collect because of its arboreal habits and seasonal activity peaks.

The tadpoles of two species of the Bokermannohyla circumdata group (Hylidae, Cophomantini).

We describe the external morphology and oral cavity of the tadpoles of Bokermannohyla caramaschii and B. diamantina respectively from the states of Espírito Santo and Bahia, Brazil. Larvae of both species are distinguished from each other by external characters such as body shape, labial tooth-row formula, number of marginal papillae, coloration and internal oral anatomy features. Some of the character states of the tadpoles of B. caramaschii and B. diamantina that are shared with all other described tadpoles of the Bokermannohyla circumdata group, such as the absence/reduction of small flaps with accessory labial teeth laterally in the oral disc, and the absence/reduction of submarginal papillae, may represent morphological synapomorphies of this species group, or at least of some internal clade. The general pattern of brownish coloration with longitudinal stripes on the caudal muscle is also common to most species of the group. We did not find character states of the oral cavity that are exclusively shared by species of the B. circumdata group, or by other groups of Bokermannohyla.

Correlation between development and increase of number of labial tooth rows in ghost frog tadpoles (Anura: Heleophrynidae)

The family Heleophrynidae is restricted to Southern Africa and comprises two genera with seven species. Tadpoles are well adapted, with huge sucker mouths, to live in the fast flowing headwaters of mountain streams. The unique sucker-like mouth has numerous transverse rows of labial teeth, which are used to attach themselves to the rock surface and to scrape algae from the rocks. In this paper data on the ontogenetic increase of labial tooth rows in tadpoles of four species of ghost frog are presented. Notes on the development of tadpoles and mouthparts are also presented.

Health status of tadpoles and metamorphs of Rhinella arenarum (Anura, Bufonidae) that inhabit agroecosystems and its implications for land use

Perturbations of water bodies near agricultural and livestock systems can affect embryonic and larval stages of anurans and negatively impact adult populations and structure of amphibian communities. This study is focused on early development of Rhinella arenarum, for which body growth, abnormalities in the oral disc and genetic damage on erythrocytes were analyzed to establish the impact of agroecosystems on local populations of amphibians. Tadpoles and metamorphs of R. arenarum were collected in three agroecosystems (namely, C1, C2, and C3) and in a site without agricultural and livestock activities (SM) from central Argentina. Egg masses of C1 were extracted for breeding tadpoles under laboratory conditions (Lab). Tadpoles were in small size and lighter in weight in C1 and C2. Metamorphs were shorter and lighter in weight in C1 and C3. In SM and Lab samples, no tadpoles with abnormal LTRF (labial tooth row formula) or without labial teeth were observed. In C1, the highest frequency of abnormal LTRF was recorded and was the only site in which tadpoles without labial teeth were found. In C1 and C2 the tadpoles had highest micronucleus frequencies and nuclear abnormalities. C1 can be considered as the site with the highest anthropogenic perturbation and with less healthy tadpoles. Livestock practices such as alternating cattle between parcel and keeping a buffer between crops and water bodies, would allow a better development of the first aquatic stages that are essential for the conservation of the anuran populations.

변색된 유전치의 순측접근에 의한 치수치료 및 레진수복

1. 순측접근법은 치수치료를 순측으로 시행한 후 변색된 순측의 치질을 확대하여 삭제하고 레진으로 순면전체를 수복함으로써 치수치료와 동시에 심미성을 회복할 수 있다. 2. 순측으로 치수치료를 시행하므로 시야가 확보에 유리하고 기구조작이 용이해 행동조절이 잘 되지 않는 어린이에게 추천된다. Traditional method of pulpectomy for a necrotic primary anterior tooth was done on lingual side. But it could not recover the discoloration of crown effectively. For the purpose of treating the discoloration of crown after lingual pulpectomy, additional methods of crown restoration were needed like : celluloid crown, open-faced crown, rasin-faced crown. Neverthless, these kinds of complete coverage methods had some disadvantages such as possibility of tooth fracture by increased tooth preparation. In order to overcome the shortcomings of lingual pulpectomy, labial treatment could be considered as an alternative. It is a method that treats necrotic pulp through the labial access opening. After finishing the pulp treatment, discolored labial tooth structure was removed extending from access opening. Discoloration of deep area could be masked effectively using opaque sealant. Cavity on labial side was restored with composite resin. This labial approach method has several advantages. First, it gives a direct vision for effective pulp treatment which is also very useful for children with poor behavior. Second, most of lingual tooth structure could be saved and occlusal contact of lingual surface remains undisrupted. Only nonfunctional discolored labial surface may removed. Third, complete removal of discolored part of a labial tooth and immediate resin restoration could be done effectively after pulp treatment. Moreover, it also could be used for pulp treatment having serious dental caries on labial surface with sound lingual tooth structure. This report presents cases with discolored upper anteior primary tooth, approaching labial side with successful restoration.

Dental patterns of the stem-group hexanchoid shark, Notidanoides muensteri (Elasmobranchii, Hexanchiformes)

ABSTRACT—Detailed analyses of the dentition of the single preserved holomorphic specimen and isolated teeth of the extinct Late Jurassic hexanchiform shark, Notidanoides muensteri, support previous interpretations that all Jurassic cow sharks belong to the family Crassonotidae, which represents stem-group hexanchoids. The reconstruction of its dentition has enabled the identification of important congruencies (comb-like lateral teeth, presence of a lower (?) symphyseal tooth row) and differences (very weak dignathic and monognathic heterodonties, with anterior teeth being of the same general morphology as laterals). Although the general tooth morphology does not change significantly, ontogenetic trajectories are identifiable, including development of lateral cusplets in symphyseal teeth, reduction of labial tooth crown ornamentation, and more pronounced dignathic heterodonty pattern in adults. The general root morphology is identical to that of Crassodontidanus and represents the plesiomorphic condition within hexanchoids. The Jurassic hexanchoids Notidanus wagneri, N. huegeliae, N. eximius, and N. nikitiini, which are known from isolated teeth only, are synonymized with Notidanoides muensteri based on the dental analyses presented here. The distribution pattern and scarcity of fossil remains indicate that this crassonotid was a typical Tethyan element of Late Jurassic neoselachian faunas and inhabited open-marine environments, probably on the outer shelves and upper continental slopes. Notidanoides appears later in the fossil record than Crassodontidanus and survives into the early Tithonian. By the end of the Jurassic, both seemingly went extinct and were replaced by other plesiomorphic hexanchoids (e.g., Pachyhexanchus) in the Early Cretaceous.