Tooth Row Research Articles

Bat Dentitions: A Model System for Studies at The Interface of Development, Biomechanics, and Evolution.

The evolution of complex dentitions was a major innovation in mammals that facilitated the expansion into new dietary niches that imposed selection for tight form-function relationships. Teeth allow mammals to ingest and process food items by applying forces produced by a third-class lever system composed by the jaw adductors, the cranium, and the mandible. Physical laws determine changes in jaw adductor (biting) forces at different bite point locations along the mandible (outlever), thus individual teeth are expected to experience different mechanical regimes during feeding. If the mammal dentition exhibits functional adaptations to mandible feeding biomechanics, then teeth are expected to have evolved to develop mechanically-advantageous sizes, shapes, and positions. Here, we present bats as a model system to test this hypothesis and, more generally, for integrative studies of mammal dental diversity. We combine a field-collected dataset of bite forces along the tooth row with data on dental and mandible morphology across 30 bat species. We (1) describe, for the first time, bite force trends along the tooth row of bats, (2) use phylogenetic comparative methods to investigate relationships among bite force patterns, tooth and mandible morphology, and (3) hypothesize how these biting mechanics patterns may relate to the developmental processes controlling tooth formation. We find that bite force variation along the tooth row is consistent with predictions from lever mechanics models, with most species having the greatest bite force at the first lower molar. The cross-sectional shape of the mandible body is strongly associated with the position of maximum bite force along the tooth row, likely reflecting mandibular adaptations to varying stress patterns among species. Further, dental dietary adaptations seem to be related to bite force variation along molariform teeth, with insectivorous species exhibiting greater bite force more anteriorly, narrower teeth and mandibles, and frugivores/omnivores showing greater bite force more posteriorly, wider teeth and mandibles. As these craniodental traits are linked through development, dietary specialization appears to have shaped intrinsic mechanisms controlling traits relevant to feeding performance.

Tooth replacement and reparative dentine formation in the middle Permian bolosaurids of European Russia

ABSTRACT A new species of the genus Belebey (Bolosauridae), Be. shumovi sp. nov., is described from the Upper Kazanian Substage (Guadalupian) of European Russia based on elements of the upper jaw, a maxilla and two premaxillae. This is the largest known bolosaurid, the skull length of which could be estimated to be around 160 mm. In addition to its overall size, Be. shumovi differs from other species of the genus in the shape of the maxilla, maxillary teeth, and their distribution along the tooth row. The holotype of Be. shumovi (maxilla) exhibits marginal dentition at the earliest stage of the tooth replacement process. Computed tomography (CT) scan data indicate the presence of almost completely formed replacement teeth along the entire tooth row, confirming the hypothesis of a single-wave cycle of tooth replacement in bolosaurids. Based on the material studied, the tertiary dentine formation was discovered for the first time among fossil reptiles. The tertiary dentine is one of the most evident adaptations of bolosaurids to high-fibre herbivory and demonstrates uniformity of the protection mechanism of the pulp in tetrapod history throughout most of the Phanerozoic.

The rapid evolution of lungfish durophagy

Innovations relating to the consumption of hard prey are implicated in ecological shifts in marine ecosystems as early as the mid-Paleozoic. Lungfishes represent the first and longest-ranging lineage of durophagous vertebrates, but how and when the various feeding specializations of this group arose remain unclear. Two exceptionally preserved fossils of the Early Devonian lobe-finned fish Youngolepis reveal the origin of the specialized lungfish feeding mechanism. Youngolepis has a radically restructured palate, reorienting jaw muscles for optimal force transition, coupled with radiating entopterygoid tooth rows like those of lungfish toothplates. This triturating surface occurs in conjunction with marginal dentition and blunt coronoid fangs, suggesting a role in crushing rather than piercing prey. Bayesian tip-dating analyses incorporating these morphological data indicate that the complete suite of lungfish feeding specializations may have arisen in as little as 7 million years, representing one of the most striking episodes of innovation during the initial evolutionary radiations of bony fishes.

Soft teeth and their role in the development of periodontal disease

This article provides a broad and detailed description of the soft teeth and their role in the development of periodontal disease, as well as the prophylactic aspects that should be taken by physicians in the treatment of this disease. When orthopedic dentists grind teeth, especially when the adjacent sides are separated, the interdental sutures are cut, the tissue bleeds, and the wound is injured. If the patient is not instructed to follow the oral cavity in the orthodontic treatment of defects in the dentition, the retention of food debris in the orthodontic appliances and in uneven rows of teeth can lead to the appearance of dentures.

A new juvenile Yamaceratops (Dinosauria, Ceratopsia) from the Javkhlant Formation (Upper Cretaceous) of Mongolia.

Here we report a new articulated skeleton of Yamaceratops dorngobiensis (MPC-D 100/553) from the Khugenetjavkhlant locality at the Shine Us Khudag (Javkhlant Formation, ?Santonian-Campanian) of the eastern Gobi Desert, Mongolia, which represents the first substantially complete skeleton and the first juvenile individual of this taxon. The specimen includes a nearly complete cranium and large portions of the vertebral column and appendicular skeleton. Its skull is about 2/3 the size of the holotype specimen, based on mandibular length. Its juvenile ontogenetic stage is confirmed by multiple indicators of skeletal and morphological immaturity known in ceratopsians, such as the long-grained surface texture on the long bones, the smooth external surface on the postorbital, open neurocentral sutures of all caudal vertebrae, a large orbit relative to the postorbital and jugal, the low angle of the lacrimal ventral ramus relative to the maxillary teeth row, narrow frontal, and straight ventral edge of the dentary. Osteohistological analysis of MPC-D 100/553 recovered three lines of arrested growth, implying around 3 years of age when it died, and verified this specimen’s immature ontogenetic stage. The specimen adds a new autapomorphy of Yamaceratops, the anteroventral margin of the fungiform dorsal end of the lacrimal being excluded from the antorbital fossa. Furthermore, it shows a unique combination of diagnostic features of some other basal neoceratopsians: the ventrally hooked rostral bone as in Aquilops americanus and very tall middle caudal neural spines about or more than four times as high as the centrum as in Koreaceratops hwaseongensis, Montanoceratops cerorhynchus, and Protoceratops andrewsi. The jugal with the subtemporal ramus deeper than the suborbital ramus as in the holotype specimen is also shared with A. americanus, Liaoceratops yanzigouensis, and juvenile P. andrewsi. Adding 38 new scorings into the recent comprehensive data matrix of basal Neoceratopsia and taking into account the ontogenetically variable characters recovered Y. dorngobiensis as the sister taxon to Euceratopsia (Leptoceratopsidae plus Coronosauria). A second phylogenetic analysis with another matrix for Ceratopsia also supported this position. The new phylogenetic position of Y. dorngobiensis is important in ceratopsian evolution, as this taxon represents one of the basalmost neoceratopsians with a broad, thin frill and hyper-elongated middle caudal neural spines while still being bipedal.

New Ankylosaurian Cranial Remains From the Lower Cretaceous (Upper Albian) Toolebuc Formation of Queensland, Australia

Australian dinosaur research has undergone a renaissance in the last 10 years, with growing knowledge of mid-Cretaceous assemblages revealing an endemic high-paleolatitude Gondwanan fauna. One of its most conspicuous members is ankylosaurs, which are rare but nonetheless occur in most Australian dinosaur-bearing formations spanning the uppermost Barremian to lower Cenomanian. Here we describe a partial ankylosaur skull from the marine Toolebuc Formation exposed near Boulia in western Queensland, Australia. This skull represents the oldest ankylosaurian material from Queensland, predating the holotype of Kunbarrasaurus ieversi, which was found in the overlying Allaru Mudstone. The ankylosaur skull is encased in a limestone concretion with the maxillary tooth rows preserved only as impressions. Synchrotron radiation X-ray tomography was used to non-destructively image and reconstruct the specimen in 3D and facilitate virtual preparation of the separate cranial bones. The reconstruction of the skull revealed the vomer, palatines, sections of the ectopterygoids and maxillae, and multiple teeth. The palate has posteriorly positioned choanae that differs from the more anterior placement seen in most other ankylosaurians, but which is shared with K. ieversi, Akainacephalus johnsoni, Cedarpelta bilbeyhallorum, Gobisaurus domoculus, and Panoplosaurus mirus. Phylogenetic analyses place the new cranial material within the recently named basal ankylosaurian clade Parankylosauria together with K. ieversi. This result, together with the anatomical similarities to the holotype of K. ieversi, permits its referral to cf. Kunbarrasaurus sp. This specimen elucidates the palatal anatomy of Australian ankylosaurs and highlights one of the most ubiquitous components of Australian mid-Cretaceous dinosaur faunas.

Teeth out of proportion: Smaller horse and cattle breeds have comparatively larger teeth.

There are different descriptions of allometric relationships between important components of the mammalian skull. Craniofacial evolutionary allometry describes a pattern of increasing facial cranium in larger skulls. Another body of literature describes disproportionately larger teeth in smaller species or specimens, matching anecdotal observations with dental problems in dwarf breeds whose teeth appear "too large for their skulls." We test the scaling of tooth row length with body size and skull length in a data set comprising 114 domestic horses (representing 40 breeds)and in another data set of 316 domestic cattle (of>60 breeds). We demonstrate that smaller skulls have a relatively longer tooth row in both horses and cattle; larger specimens have relatively shorter tooth rows. Whereas in horses, larger skulls have a relatively longer diastema,the distance of the mesial maxillary premolar to the premaxilla was proportional to cranium length in cattle. While the reasons for these patterns remain to be detected, they support the hypothesis that tooth size might be less "evolvable," in terms of time required for changes, than body size. The pattern may affect (i) the selective breeding for dwarf breeds by setting minimum constraints for skull size, as described previously for domestic horses with the same data set; (ii) the susceptibility of small breeds for dental problems; and (iii) differences in chewing efficiency between breeds of different sizes. The findings support the existing concept that scaling of tooth to body size across taxa becomes more isometric the longer these taxa are separated in evolutionary time.

Integration patterns of cheek teeth and ecomorphological evolution in grinding herbivores: the case of caviine rodents (Caviomorpha: Caviidae)

AbstractCaviid rodents have peculiar craniomandibular specializations toward masticatory propalinal movements and grinding, in relation to a grass-rich diet. The aim of this study is to: (1) analyse the variation of cheek tooth shape in the Caviinae and, (2) quantify the covariation relations between caviine cheek teeth. For this purpose, we perform the first geometric morphometric analysis on cheek teeth of fossil and extant caviids, ancestral shape reconstructions and covariation analyses. Our results show that caviine dentition is strongly integrated with a higher covariation between teeth of the same row than between opposite teeth, differing from mammals with complex interlocking. Each series acts as a single functional unit integrated during grinding action obtained by mainly propalinal movements. However, p4 shows more plasticity, allowing its morphology to differentiate from the common pattern of molars. Morphologically homogeneous cheek tooth series are ancestral in crown caviids and highly marked in Cavia, while stronger morphological differences between tooth pieces are observed in Microcavia and Galea. These differences are probably driven by diet changes. The tendency towards alignment of main masticatory movements with the tooth row axes seems to be a key factor in understanding cheek tooth covariation patterns in this and other rodent clades.

Studies on Age-Related Changes in Equine Cheek Teeth Angulation and Dental Drift.

BackgroundCheek teeth (second through fourth premolars and first through third molars) diastema is a common and painful equine disorder caused by the absence of effective tight interdental contact between these teeth. Limited objective information is available on the angulation of equine cheek teeth that control dental drift or on mesial or distal equine cheek teeth drift that should normally prevent this disorder.ObjectivesTo measure the angulation of the mesial and distal cheek teeth in horses of different ages, quantify age-related cheek teeth mesial and distal dental drift, and measure the cheek teeth row length in horses of different ages.Study DesignRetrospective review of computed tomographic images of equine heads.MethodsCase details and CT images from clinical equine cases that had undergone standing CT head examination were collated.Three sets of measurements were acquired from each head. “Head size” calculated as the distance between the caudal aspect of the orbit and the caudal aspect of the naso-incisive notch was used to standardize measurements in different sized heads. The length of the cheek teeth rows measured from the mesial aspect of the Triadan 06 occlusal surface to the distal aspect of the Triadan 11 occlusal surface. The rostro-caudal (antero-posterior) position and angulation of the mandibular and maxillary Triadan 06 and 11 teeth were measured in relation to reference lines drawn on CT images.ResultsSignificant mesial drift occurred in the maxillary and mandibular Triadan 11s. Despite their distal angulation, the upper and lower Triadan 06s also drifted mesially. The mean angulation of Triadan 06 and 11 mandibular teeth (17.8 and 26.2°, respectively) was almost double that of maxillary teeth (9.2 and 13.3°, respectively) with both Triadan 11s having greater angulation than the 06s. Cheek teeth angulation only significantly decreased in the mandibular 06s. Cheek teeth arcade lengths decreased with age, but these decreases were not significant.Main LimitationsLimitations include the relatively small sample size.ConclusionsIn the population of horses used for this study, age related mesial drift occurred in both Triadan 06 and 11s, and the angulation of these teeth did not decrease with age in most arcades.

Virtual cranial reconstruction of Hispanomys moralesi (Rodentia, Mammalia) from Cerro de los Batallones (upper Miocene, Spain)

ABSTRACT El Cerro de los Batallones is one of the most important fossil sites of the Miocene. The quantity and preservation of its fossil remains have allowed us to describe many new mammal species. One of these is Hispanomys moralesi, a derived species of the Tribe Cricetodontini, a wide group of rodents with great importance in the faunal assemblage during the Miocene. Unlike most fossil micromammals in this fossil site, we have obtained skull remains that preserve never recorded anatomical structures in this time interval. Due to the fragility of the material, it could only be studied in detail using X-ray micro-computed tomography (µ-CT Scan). With this technique, we obtained three-dimensional models of 12 skulls of Hispanomys moralesi, in which different osteological parts have been described. In this way, we compared the morphological variation of the skull with other fossil cricetids and concluded that Batallones’ species is an opisthodont rodent, with a relatively elongated rostrum, a robust base of zygomatic arches and big-sized tooth rows. Opisthodont incisor characterises omnivore and herbivore diets in rodents. Therefore, these new findings of Hispanomys moralesi could allow us to describe the dietary affinities of this extinct species.

Morphological evolution of the cave bear (Ursus spelaeus) mandibular molars: coordinated size and shape changes through the Scladina Cave chronostratigraphy

Out of all extinct megafaunal mammals of the Quaternary, the cave bear Ursus spelaeus is one of the best represented in the fossil record. This species has been found to exhibit skeletal morphological adaptations when exploiting varied environmental niches, be that spatially or temporally. Here, we employ geometric morphometrics and phenotypic trajectory analysis to explore temporal morphological changes across the entire lower molar tooth row from the infilling of Scladina Cave, Belgium. We show that molar tooth size increases from Marine Isotope Stage (MIS) 5 – MIS 3, with cusp position varying temporally in relation to a larger talonid grinding platform in later time periods. Phenotypic trajectory analyses further show similar evolutionary shape trajectories in the first and second molars, but not in the third molar. Morphological changes related to a larger grinding platform are found in the second and third molars, with the divergent morphological change of M 3 suggesting that this tooth is less constrained and appears much more responsive to environmental changes. The need to cope with harder fibrous plant material present in the palaeoenvironment potentially constrained morphological evolution of the cave bear until its disappearance throughout Europe. • Lower molar tooth size increases from Marine Isotope Stage 5 – MIS 3. • M 3 appears less constrained and much more responsive to environmental changes. • Cave bear lower molar shape changed to process more fibrous plant material. • Tooth shape is a powerful ecological tool to understand adaptation of cave bears.

A new species of Characidium (Characiformes: Crenuchidae) from the rio Doce basin, Brazil

Abstract A new species of Characidium is described from the tributaries of the upper and middle rio Doce basin, Minas Gerais, Brazil. The new species is distinguished from most congeners, except C. cricarense, C. hasemani, C. helmeri, C. kalunga, C. pterostictum, C. schubarti, C. summus, and C. travassosi by lacking scales in the area between the anterior limit of the isthmus and the anterior margin of cleithrum. The new species differs from the aforementioned species by a series of characters, including the presence of the adipose fin, 2–4 scales between the anus and anal fin, two rows of dentary teeth, presence of the parietal branch of the supraorbital canal, 4 scale rows above the lateral line, and absence of two conspicuous inclined dark bands on each caudal-fin lobe. The new species further differs from most congeners with an unscaled ventral surface of the isthmus by the presence of 33–34 pored scales on the lateral line and by the dark dashes on the caudal fin-rays not forming well-defined bands.

PH Measurement of Mixed Saliva using a Flow-injection Sensor with a Tubular Carbon Electrode

Present work discusses the design of a flow-injection sensor for measuring pH in micro-volumes of the sample. A carbon electrode with a capillary channel was used as a working electrode, through which an electrolyte solution saturated with quinhydrone flows at a constant speed. The volume of the analyzed sample was 0.1-0.2 mL. Compliance with the Nernst pH function with a slope of 53.1 ± 1.1 mV/pH was observed in the range of 1.0-7.5 pH. The sensor has been tested in the non-invasive diagnostics of acid-base balance of the oral fluid. The analysis of mixed saliva was carried out in 30 practically healthy student volunteers with an intact row of teeth. The median pH value of 7.03 was established, which corresponds to the physiological norm. At the same time, there is a predisposition to caries in almost half of the subjects, since a high risk is determined in the formation of focal demineralization of tooth enamel with the appearance of erosion of hard tooth tissues.

The effectiveness of orthodontic and osteopathic correction in patients with dental anomalies and musculoskeletal dysfunction of the temporomandibular joint in the presence of concomitant somatic dysfunctions and without it

Introduction. The influence of the dental apparatus on the balance of the body in an upright position has been widely discussed in the literature for several decades. Examination of the patient taking into account his postural balance makes it possible to clarify the reasons for the low effectiveness of pain syndromes treatment of the craniocervical region caused by malocclusion, as well as ineffective correction of musculoskeletal dysfunction of the temporomandibular joint (MSD TMJ) associated with posture disorders.The aim of the study is to evaluate the effectiveness of treatment of patients with dental anomalies and musculoskeletal dysfunctions of the temporomandibular joint and concomitant somatic dysfunctions (if any) by methods of orthodontic and osteopathic correction.Materials and methods. The study involved 102 patients aged from 18 to 45 years with TMJ. All patients underwent orthodontic and osteopathic examination. 3 groups of patients were formed: № 1 — exclusively with dental anomalies TMJ (occlusive dysfunction), who received only orthodontic treatment, № 2 with concomitant somatic (extra-occlusive) dysfunctions, who received only orthodontic treatment, and №3 with concomitant somatic (extra-occlusive) dysfunctions, who received both orthodontic and osteopathic treatment. Orthodontic treatment of musculoskeletal dysfunction of the TMJ consisted of the occlusive kappa manufacturing. Osteopathic correction was carried out individually, taking into account the identified somatic dysfunctions, on average 3 sessions. Patients also received drug therapy, and they performed myohymnastics for the masticatory muscles. The clinical dysfunction index (Helkimo M.) was used to control the elimination dynamics of the TMJ's musculoskeletal dysfunction symptoms. The assessment of the pain dynamics in the TMJ was carried out by a visual-analog scale (VAS). The evaluation of the osteopathic treatment effectiveness was carried out on the basis of computer stabilometry data and osteopathic examination data. A stabilometric study was performed on the «ST-150» («Biomera») stabiloplatform in the Romberg sample (European foot installation) with open and closed eyes in two positions of the lower jaw: 1) in a state of physiological rest (tooth rows are separated); 2) in the kappa with closed tooth rows.Results. The MSD TMJ symptoms were eliminated 10 weeks after the start of treatment in all (100 %) patients of group № 1 and group № 3. Among the patients in group № 2, only 12,1 % of patients had complete absence of MSD TMJ symptoms, while all patients in this group had a statistically significant decrease in the clinical index of Helkimo dysfunction. In one third of the group № 2 patients on the 12th week of orthodontic treatment, headaches and/or pains in other parts of the musculoskeletal system (neck, back, shoulders, arms) prevailed among complaints and which were previously indicated in the anamnesis. This occurred after the elimination of the MSD TMJ symptoms. The absolute majority of patients in group № 3 (97,1 %) noted the complete disappearance of headaches and/or pains in other parts of the musculoskeletal system (neck, back, shoulders, arms). Also, in patients of this group, stabilometric indicators were normalized in a state of physiological rest and in the kappa.Conclusion. Patients with somatic dysfunctions need complex treatment with the participation of an osteopath and a dentist. When assessing the osteopathic status of a patient, it is important to determine whether the patient has only occlusive dysfunctions or there are also extra-occlusive ones. Additional osteopathic correction is recommended for patients with extraocclusive dysfunctions in order to achieve treatment results comparable in effectiveness and timing.

The incisive foramen as character in distinguishing morphologically similar species of mammals

An analysis of the morphology and variability of the size and shape of a key morphological structure in the rostral part of the skull—the incisive foramen—has been carried out. It is shown that incisive foramina are variable morphological structures, the features of which are group-specific (at the level of genera and families), and in some cases also species-specific. At both these levels, the shape and size of the incisive foramen have features that can serve as criteria for species identification by osteological patterns. Their location is important for diagnosis because these structures are preserved in most specimens that have suffered various kinds of damage (e.g. in fodder residues of carnivorous mammals or in owl pellets), and their placement in the anterior part of the bony palate as well as them being protected from the sides with rows of teeth makes these structures invulnerable to trauma-related variation. It is shown that there is a specific structure (size, location, and shape) of incisive foramina at the level of taxonomic groups of all ranks, from orders to species. The analysis was performed mainly on the examples of different groups of rodents as an order, represented by the largest number of pairs of close species. Examples with several different groups, in particular with different pairs of species of voles, mice, mole rats, ground squirrels, and others are considered. Examples with differences in close pairs of species in other groups (white-toothed shrews, polecats, roe deer, etc.) are also known. In all pairs of related species, a pattern was found, according to which species that are restricted to steppe ecosystems have the smallest incisive foramina, while species from wetland habitats have large ones. In many cases, groups of genera and families well differ in the shape and location of incisive foramina, and close pairs of species differ well in the size of these structures (primarily in length), although it is important to always consider the ontogenetic age of specimens: in young individuals, the incisive foramina are naturally small, similar to incisive foramina in other species, which are characterized by small incisive foramina in general. Based on the known data on the role of incisive foramina and the Jacobson organ in the life of mammals, hypotheses have been considered that may explain the differences in species and genera by the structure (size, location, and shape) of incisive foramina.

A Study of Some Biological Aspects of Pacu Piaractus Brachypomus (G. Cuvier, 1818)

The present study attempts to shed light on some biological aspects and characteristics of Piaractus brachypomus, including some biometrics, phenotypic and feeding pattern that characterizes this species. Besides, the study touches upon the body shape and the Otolith. These fish species have recently been seen frozen in the Iraqi local market. The standard length of fish specimens in this study reach 26.55cm it exceeded the specimens of Pacu fish collected from other studies from other countries, As well the specimens weight was 632gm it exceeded other studies mentioned in this manuscript. As the irregularity in the distribution of teeth rows, especially in the lower jaw was clear in our specimens. The average weight of some skull bones of Piaractus brachypomus specimens is 2.25g, which gives evidence of the heaviness of the bones of this species.

Results determination of need patients to implantology dentistry help in depending of extent’s occlusion defects in different territorial-administrative zone of Tajikistan

Aim. To define the needs of patient in implantology dentistry help in depending of extent defect teeth rows beside populations living in different region of the Republic of Tajikistan.Material and methods. In the article are presents the results determination of needs patients to implantology dentistry help in depending of extent defect teeth rows beside populations living in different region of the Republic of Tajikistan. In examined group entered dentistry patients both sexual difference with defect of the teeth rows which were divided into 3 groups: 1st group formed the 372 patients with small defect of the teeth rows (absence 1–3 teeth); in 2nd group entered 783 examined patients with average extent (absence 4–6 teeth) of the defect of teeth row; 3rd group formed 109 patients with greater defect of the teeth rows (absence more than 6 teeth). For the reason studies of extent defect teeth rows organized clinical and epidemiological examination of the orthopedic status in different territorial-administrative zone.Results. Amongst examined persons in respect of defect of the teeth rows by small extent exists reliable reduction their prevalence on measure of the increase the age, then comparatively occlusion defects with average and big extent noted reliable increase of the factor of prevalence.Conclusions. Got material allow to improve rendering of implant’s prosthesis in depending of extent occlusion defects and hereinafter completely shorten the risk of invalidation chewing device.

Diastemapycnodus tavernensis gen. et sp. nov. (Actinopterygii, †Pycnodontiformes) from the marine Maastrichtian (Late Cretaceous) of the Dakhla Formation, Western Desert, Egypt

ABSTRACT Based on a single vomer with partial dentition collected from the lower part of the Beris member, Dakhla Formation, dated to the Maastrichtian, we describe the new pycnodont Diastemapycnodus tavernensis gen et sp. nov. The characteristics of the new genus are (i) five rows of teeth and (ii) very large diastema interposed between the primary lateral rows and the medial dental row. The new species has the following combination of characteristics: (i) paired primary lateral rows composed of large, rounded teeth that are not ornamented and are significantly larger than the adjacent teeth in both the medial and secondary lateral rows; (ii) teeth of the primary lateral rows with an elliptical profile, with a major axis normal to the major axis of the vomer, and (iii) they are the largest teeth among those that arm the vomer; and (iv) all of the teeth are mostly not ornamented and are smooth on the unworn occlusal surfaces. Diastemapycnodus tavernensis is a pycnodont with a very reduced vomerine dental floor, which certainly falls within the well-known evolutionary lineage with an almost edentulous vomer (Serrasalmimidae). The authors attribute to the new genus Diastemapycnodus also the species ‘Typodus’ valens.

A fresh look at Cladarosymblema narrienense, a tetrapodomorph fish (Sarcopterygii: Megalichthyidae) from the Carboniferous of Australia, illuminated via X-ray tomography.

BackgroundThe megalichthyids are one of several clades of extinct tetrapodomorph fish that lived throughout the Devonian–Permian periods. They are advanced “osteolepidid-grade” fishes that lived in freshwater swamp and lake environments, with some taxa growing to very large sizes. They bear cosmine-covered bones and a large premaxillary tusk that lies lingually to a row of small teeth. Diagnosis of the family remains controversial with various authors revising it several times in recent works. There are fewer than 10 genera known globally, and only one member definitively identified from Gondwana. Cladarosymblema narrienense Fox et al. 1995 was described from the Lower Carboniferous Raymond Formation in Queensland, Australia, on the basis of several well-preserved specimens. Despite this detailed work, several aspects of its anatomy remain undescribed.MethodsTwo especially well-preserved 3D fossils of Cladarosymblema narrienense, including the holotype specimen, are scanned using synchrotron or micro-computed tomography (µCT), and 3D modelled using specialist segmentation and visualisation software. New anatomical detail, in particular internal anatomy, is revealed for the first time in this taxon. A novel phylogenetic matrix, adapted from other recent work on tetrapodomorphs, is used to clarify the interrelationships of the megalichthyids and confirm the phylogenetic position of C. narrienense.ResultsNever before seen morphological details of the palate, hyoid arch, basibranchial skeleton, pectoral girdle and axial skeleton are revealed and described. Several additional features are confirmed or updated from the original description. Moreover, the first full, virtual cranial endocast of any tetrapodomorph fish is presented and described, giving insight into the early neural adaptations in this group. Phylogenetic analysis confirms the monophyly of the Megalichthyidae with seven genera included (Askerichthys, Cladarosymblema, Ectosteorhachis, Mahalalepis, Megalichthys, Palatinichthys, and Sengoerichthys). The position of the megalichthyids as sister group to canowindrids, crownward of “osteolepidids” (e.g.,Osteolepis and Gogonasus), but below “tristichopterids” such as Eusthenopteron is confirmed, but our findings suggest further work is required to resolve megalichthyid interrelationships.

Bidenichthys okamotoi, a New Species of the Bythitidae (Ophidiiformes, Teleostei) from the Koko Seamount, Central North Pacific

Two specimens from the Koko Seamount (Koko Guyot), in the Hawaiian-Emperor seamount chain, Central North Pacific, caught in 2009 and 2010 are here described as a new species, Bidenichthys okamotoi. The taxonomy of the species in the genera Bidenichthys Barnard, 1934, and Fiordichthys Paulin, 1995, has been confusing due to the lost type of B. consorbrinus (Hutton, 1876) and the rarity of some of the species. Following the synonymization of Fiordichthys Paulin, 1995, with Bidenichthys by Møller and Nielsen 2015 and of Bidenichthys beeblebroxi Paulin, 1995, with Bidenichthys consobrinus Hutton, 1876, the genus Bidenichthys now comprises five species: B. capensis, B. consobrinus, B. okamotoi, B. paxtoni and B. slartibartfasti. Bidenichthys okamotoi differs from its congeners in, e.g., the fewer precaudal vertebrae (12 vs. 13), more palatine teeth rows (4–6 vs. 2–3), shorter pelvic fins (12.1–13.4% vs. 14.4–21.0% SL), max size (187 vs. 147 mm SL) and the shape of the sulcus of the otolith. We here present an updated diagnosis of the genus. A computed tomography (CT) scan of the holotype of B. okamotoi provides for additional anatomical details. The disjunctive occurrence of Bidenichthys okamotoi on the Emperor Seamount chain about 7500 km from the nearest congeneric taxon in New Zealand is discussed. The fossil otolith-based record of the genus Bidenichthys and its systematic implications is briefly discussed.