Symphyseal Tooth Research Articles

Use of presence vs absence of symphyseal teeth in jaws for the forensic analysis of bites by large traumatogenic shark species.

Identifying the species of shark responsible for a bite on humans is both complex and important for understanding and managing the shark risk. Depending on the species, tiny teeth may or may not be present in the symphyseal space at the junction of the upper and lower half-jaws. In the case of bites, these tiny teeth (if present) often leave specific marks that may enable species to be quickly and reliably distinguished. We first present the anatomo-morphological characteristics of the jaws of the three most traumatogenic species for humans which are the white, tiger, and bull sharks. The white shark has no symphyseal teeth, while the tiger and bull sharks do. On the basis of three confirmed real case studies involving those species, we then show that for the white shark, the wide symphyseal space between the first two teeth of each jaw usually leads to wounds including the presence of (quite) large flesh flaps, without any tooth imprint. Conversely, wounds following bites made by the tiger and bull sharks will generally leave characteristic small imprints of symphyseal teeth, especially in the case of incomplete or superficial bites. Although not systematic, this diagnostic approach provides fast, reliable, and clean results. The discrimination between two species with symphyseal teeth can then be made on the basis of complementary anatomic information such as jaw curvature and details linked to the anatomy of the teeth themselves, as well as the ecological context.

Acanthodian dental development and the origin of gnathostome dentitions.

Chondrichthyan dentitions are conventionally interpreted to reflect the ancestral gnathostome condition but interpretations of osteichthyan dental evolution in this light have proved unsuccessful, perhaps because chondrichthyan dentitions are equally specialized, or else evolved independently. Ischnacanthid acanthodians are stem-Chondrichthyes; as phylogenetic intermediates of osteichthyans and crown-chondrichthyans, the nature of their enigmatic dentition may inform homology and the ancestral gnathostome condition. Here we show that ischnacanthid marginal dentitions were statodont, composed of multicuspidate teeth added in distally diverging rows and through proximal superpositional replacement, while their symphyseal tooth whorls are comparable to chondrichthyan and osteichthyan counterparts. Ancestral state estimation indicates the presence of oral tubercles on the jaws of the gnathostome crown-ancestor; tooth whorls or tooth rows evolved independently in placoderms, osteichthyans, ischnacanthids, other acanthodians and crown-chondrichthyans. Crown-chondrichthyan dentitions are derived relative to the gnathostome crown-ancestor, which possessed a simple dentition and lacked a permanent dental lamina, which evolved independently in Chondrichthyes and Osteichthyes.

Taxonomic revision of the genus Anostomoides (Characiformes: Anostomidae).

A taxonomic revision of Anostomoides is herein presented based on a comprehensive revision of specimens deposited in fish collections and the literature. The present revision proposes that A. laticeps is a junior synonym of A. atrianalis, while A. passionis is a junior synonym of Leporinus nattereri, and the latter is thus transferred to Anostomoides, forming the new combination Anostomoides nattereri. Principal Components Analysis (PCA) showed that examined specimens form two distinct morphotypes, corroborating the validity of both A. atrianalis and A. nattereri. Anostomoides nattereri is distinguished from A. atrianalis by having four branchiostegal rays (vs. three), three pores in infraorbital one (vs. four), 37-39 pored lateral-line scales (vs. 41-44), lower lip with rounded dermal papillae (vs. forming ridges), three dark rounded midlateral blotches (vs. three or four vertically elongated blotches and/or a faded dark longitudinal stripe), dark lines between scale series on posterior half of body on specimens smaller than 150 mm SL (vs. dark lines absent), a greater body depth (27.6-36.2 % vs. 24.5-38.7% of SL) and smaller interorbital distance (34.4-53.8 % vs. 42.6-67.3 % of HL). Anostomoides nattereri is distributed across several tributaries of the Amazon and Orinoco rivers, whereas A. atrianalis is widespread throughout the Amazon, Orinoco, and Essequibo basins. The genus Anostomoides is currently diagnosed based on a combination of non-exclusive characters: upturned or slightly upturned mouth with four premaxillary teeth including symphyseal tooth bicuspid or with blunt cutting edge, remaining teeth slightly tricuspid (with medial cuspid distinctly larger); four dentary teeth, symphyseal tooth with truncate cutting edge (without cusps); second tooth with a single large cusp, and two lateral teeth with three or slightly more small cusps.

A Tooth Whorl ofEdestus heinrichi(Chondrichthyes, Eugeneodontiformes) Displaying Progressive Macrowear

Edestus is a Middle Pennsylvanian chondrichthyan possessing symphyseal tooth whorls in both the upper and lower jaws. The curvature of the tooth whorls prevents most of the crowns of the opposing whorls from occluding with each other. For that reason, it has recently been hypothesized that the tooth whorls were used to slash prey with a vertical motion of the anterior part of the body, not to cut prey caught between them. A tooth of Edestus minor having a truncated, smoothly worn apex has been reported previously. Here, a partial tooth whorl of a different species, Edestus heinrichi, is described. The apices of the crowns are worn, so that the crown heights are reduced by about one third. The more labial (older) of the two preserved crowns shows more wear than the more lingual (younger) one. In contrast to the previously reported E. minor tooth, wear is observed to the serrations as well as to the apices of the crowns. The observed wear on both the E. minor tooth and on the E. heinrichi tooth whorl supports the recent hypothesis on the function of the tooth whorls. In both cases, the apices might have been abraded by attempted predation on or scavenging of large fish having skin covered with denticles or scales.

A new janassid petalodont chondrichthyan from the Early Carboniferous of Derbyshire, UK

The very small teeth of a new petalodont chondrichthyan are described from the Lower Carboniferous Eyam Limestone Formation (Peak Limestone Group, Carboniferous Limestone Supergroup; Brigantian, Early Carboniferous) of Derbyshire. Cypripediodens cristatus gen. et sp. nov. belongs to the Family Janassidae on the basis of the angle formed between the base and the crown. Presumed lower symphyseal teeth are Fissodus-like, possessing two labial cusps, whilst the rest of the dentition is relatively homodont. Individual crowns measure up to 1.3mm labiolingually and possess a single labial cusp with virtually circular cross-section, separated from a prominent lingual cusp with circumferential cristae from which it is separated by a central trough.

Evidence of macrophagous teleosaurid crocodylomorphs in the Corallian Group (Oxfordian, Late Jurassic) of the UK.

Teleosaurids were a group of semi-aquatic crocodylomorphs with a fossil record that spanned the Jurassic Period. In the UK, abundant specimens are known from the Oxford Clay Formation (OCF, Callovian to lower Oxfordian), but are very rare in the Kimmeridge Clay Formation (KCF, Kimmeridgian to lower Tithonian), despite their abundance in some contemporaneous deposits in continental Europe. Unfortunately, due to the paucity of material from the intermediate ‘Corallian Gap’ (middle to upper Oxfordian), we lack an understanding of how and why teleosaurid taxic abundance and diversity declined from the OCF to the KCF. The recognition of an incomplete teleosaurid lower jaw from the Corallian of Weymouth (Dorset, UK) begins to rectify this. The vertically oriented dentition, blunt tooth apices, intense enamel ornamentation that shifts to an anastomosed pattern apically, and deep reception pits on the dentary unambiguously demonstrates the affinity of this specimen with an unnamed sub-clade of macrophagous/durophagous teleosaurids (‘Steneosaurus’ obtusidens + Machimosaurus). The high symphyseal tooth count allows us to exclude the specimen from M. hugii and M. mosae, but in absence of more diagnostic material we cannot unambiguously assign DORCM G.3939 to a more specific level. Nevertheless, this specimen represents the first mandibular material referable to Teleosauridae from the poorly sampled middle-upper Oxfordian time-span in the UK.

Development and evolution of dentition pattern and tooth order in the skates and rays (batoidea; chondrichthyes).

Shark and ray (elasmobranch) dentitions are well known for their multiple generations of teeth, with isolated teeth being common in the fossil record. However, how the diverse dentitions characteristic of elasmobranchs form is still poorly understood. Data on the development and maintenance of the dental patterning in this major vertebrate group will allow comparisons to other morphologically diverse taxa, including the bony fishes, in order to identify shared pattern characters for the vertebrate dentition as a whole. Data is especially lacking from the Batoidea (skates and rays), hence our objective is to compile data on embryonic and adult batoid tooth development contributing to ordering of the dentition, from cleared and stained specimens and micro-CT scans, with 3D rendered models. We selected species (adult and embryonic) spanning phylogenetically significant batoid clades, such that our observations may raise questions about relationships within the batoids, particularly with respect to current molecular-based analyses. We include developmental data from embryos of recent model organisms Leucoraja erinacea and Raja clavata to evaluate the earliest establishment of the dentition. Characters of the batoid dentition investigated include alternate addition of teeth as offset successional tooth rows (versus single separate files), presence of a symphyseal initiator region (symphyseal tooth present, or absent, but with two parasymphyseal teeth) and a restriction to tooth addition along each jaw reducing the number of tooth families, relative to addition of successor teeth within each family. Our ultimate aim is to understand the shared characters of the batoids, and whether or not these dental characters are shared more broadly within elasmobranchs, by comparing these to dentitions in shark outgroups. These developmental morphological analyses will provide a solid basis to better understand dental evolution in these important vertebrate groups as well as the general plesiomorphic vertebrate dental condition.

An Abraded Tooth ofEdestus(Chondrichthyes, Eugeneodontiformes): Evidence for a Unique Mode of Predation

The paired symphyseal tooth whorls of the Carboniferous chondrichthyan Edestus are perhaps the most enigmatic dental structures of any known vertebrate. The tooth whorls have been compared to scissors or to saw blades. It is commonly held that the tooth whorls were used in opposition, to cut prey caught between them. However, the curvature of the whorls makes such a function inefficient and therefore implausible. A symphyseal tooth of Edestus minor from the Pennsylvanian of Texas provides the first new information bearing on the function of Edestus tooth whorls in over a century. The tooth is truncated apically, and the surface of the surviving portion is worn smooth. The orientation of the abraded surface, perpendicular to the axis of the crown, suggests that the tooth whorls were used to slash prey with a vertical motion of the anterior part of the body. Such a mode of predation apparently has not been reported in any other organism, extinct or extant. In contrast to Edestus, wear to the symphyseal teet...

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.

Redescription of Leporinus jamesi (Characiformes: Anostomidae), a poorly known species of Leporinus from the lowlands of the central Amazon, Brazil

The poorly known Leporinus jamesiis redescribed. The species was originally described based on a single specimen collected in the rio Solimões at Manacapuru, in the central Amazon, Brazil. The holotype went missing before the species description was finished and published, and remained lost for more than a hundred years. Leporinus jamesi is distinguished from its congeners by having pectoral and pelvic fins dark, 42 to 45 scales on the lateral line, 16 scale series around the caudal peduncle, a body with two conspicuous dark midlateral blotches (the blotch on the caudal peduncle absent or inconspicuous), and four teeth on the premaxilla and dentary, including a bicuspid symphyseal tooth on the premaxilla. A principal component analysis on morphometric traits between combined samples of L. jamesi and L. amazonicus was performed showing significant morphometric differences between these species. In addition, inaccuracies in Borodin's descriptions of various species of the genus Leporinus are discussed.

Skeleton of the Fossil SharkIsurus denticulatusfrom the Turonian (Late Cretaceous) of Germany—Ecological Coevolution with Prey of Mackerel Sharks

AnIsurus denticulatus(Glickman, 1957) shark skeleton from the late Turonian (Late Cretaceous) of Germany is described within a diverse upwelling influenced fish fauna of northern Germany, Europe. It was found in the turbiditic marly limestones at the submarine Northwestphalian Lippe Swell in the southern Proto-North Sea Basin. Compared to modern mackerel sharkIsurus oxyrinchusRafinesque, 1809, including cranial denticles, this allows a revision of the younger synonym “CretoxyrhinaGlickman, 1964”. Within the CretaceousIsurus, a loss of the lateral tooth cusps and nutritive clefts of the roots (considered as plesiomorphic character of the Lamnidae) took place from the Albian (Early Cretaceous) to the Campanian (Late Cretaceous). The tooth morphology changed during the Albian-Turonian from a tearing (I. denticulatus) to a cutting (I. mantelli) type (Coniacian-Campanian). The complete lateral cusplet and symphyseal teeth reduction inIsurusat the end of the Cretaceous seem to be a result of the coevolutionary changing feeding habits of a worldwide expanding shark. In a second evolutionary adaptation, parallel to the new radiation of marine mammals (Paleocene/early Eocene), fromIsurus, the white shark ancestors (Carcharodon) seem to originate. In another radiation fromIsurus, coevolving with appearance of dolphins and further marine mammal evolution within the Middle Miocene, a second timeIsurusdeveloped serrated teeth (I. escheri).

New Species of Leporinus from the Rio Tapajós Basin, Brazil, and Redescription of L. moralesi (Characiformes: Anostomidae)

Leporinus moralesi is a poorly known species from central Amazon basin, Brazil, which is redescribed based on examination of type specimens and additional material. The species is diagnosed by having a dark midlateral stripe running from the vertical through the dorsal fin to the end of the middle caudal-fin rays, 35 to 38 lateral-line scales, five scale rows between the dorsal fin and the lateral line, four or five scale rows between the lateral line and the pelvic fin, 16 scale rows around the caudal peduncle, three teeth on the premaxilla and four on the dentary. Leporinus uatumaensis, described from the Rio Uatumã, a tributary of the Rio Amazonas immediately downstream from Manaus, is a junior synonym of L. moralesi. A lectotype is designated herein for Leporinus muelleri ( = L. moralesi). In addition, a new species of Leporinus from the Rio Tapajós, Pará, Brazil, is described. The new species shares with Leporinus moralesi the presence of symphyseal tooth of the premaxilla with two cusps of similar size in all examined specimens, and middle caudal-fin rays dark, but differs by the dark midlateral stripe beginning at the snout to the end of the middle caudal-fin rays.Leporinus moralesi é uma espécie pouco conhecida na Amazônia Central, Brasil, e que é aqui redescrita com base no exame dos exemplares da série tipo e de material adicional. A espécie é diagnosticada por ter uma listra escura da vertical que passa pela nadadeira dorsal à nadadeira caudal, estendida sobre os raios medianos da caudal, 35 a 38 escamas na linha lateral, cinco séries de escamas entre a nadadeira dorsal e a linha lateral, quatro ou cinco séries de escamas entre a linha lateral e a nadadeira pélvica, 16 séries de escamas ao redor do pedúnculo caudal, três dentes no pré-maxilar e quatro no dentário. Leporinus uatumaensis, descrita do Rio Uatumã, um tributário da margem esquerda do Rio Amazonas pouco a jusante de Manaus, é aqui considerada sinônimo júnior de L. moralesi. A série tipo de Leporinus muelleri (L. moralesi) foi examinada e um lectótipo é aqui designado. Além disso, uma espécie nova de Leporinus do Rio Tapajós, Pará, Brasil, é descrita. A espécie nova compartilha com Leporinus moralesi a presença de dente sinfisiano no pré-maxilar com duas cúspides de tamanho similar em todos os exemplares examinados, e os raios medianos da nadadeira caudal escuros, mas difere desta por ter uma listra escura da ponta do focinho até a nadadeira caudal.

A new cretaceous notosuchian (Mesoeucrocodylia) with bizarre dentition from Brazil

A new species of Notosuchia, Labidiosuchus amicum gen. et sp. nov., is described based on an incomplete lower jaw (DGM 1480-R) from the Upper Cretaceous Marília Formation (Maastrichtian) recovered from a quarry near the Peirópolis municipality, Minas Gerais State, Southeastern Brazil. The mandibular symphysis is long, strong anterodorsally projected and ‘Y-shaped’. The bizarre dentition is formed by at least eight teeth placed in a symphyseal tooth battery, some located lateral to each other. The first pair is larger than all others and procumbent. Some teeth are obliquely implanted (anterolabially to posterolingually) and have sub circular to elliptical outline. At least the posterior teeth are single cuspidate with acute apex. Labidiosuchus amicum shows a rather bizarre dentition, increasing the taxonomic diversity and potential feeding strategies of notosuchian crocodylomorphs.

A new species of Paretroplus (Teleostei: Cichlidae: Etroplinae) from northeastern Madagascar, with a phylogeny and revised diagnosis for the P. damii clade

Paretroplus loisellei, a new species of etropline cichlid from Madagascar, is described from the middle to lower reaches of the Mahanara River, located to the north of the Masoala Peninsula in northeastern Madagascar. The new species is recovered within the “Paretroplus damii clade” on the basis of several apomorphic anatomical features, including the presence of a triangular, black or dark gray, pectoral-axil patch, chest scales that are greatly reduced in size and highly embedded, and flank scales in which the posterior field is thin and unossified. The new species is distinguished from its sister taxon, P. damii, by a more or less horizontal profile extending from the anterior margin of the lower jaw to the ventroposterior margin of the suspensorium (vs. strongly rounded and convex), horizontally oriented oral jaws with fleshy lips (vs. oblique and thin), tricuspid symphyseal teeth in the upper jaw with distinct and sharp lateral cusps, a much darker overall pigmentation pattern, and distinctive bright golden breeding coloration (vs. brick red).

Reiterative pattern of sonic hedgehog expression in the catshark dentition reveals a phylogenetic template for jawed vertebrates.

For a dentition representing the most basal extant gnathostomes, that of the shark can provide us with key insights into the evolution of vertebrate dentitions. To detail the pattern of odontogenesis, we have profiled the expression of sonic hedgehog, a key regulator of tooth induction. We find in the catshark (Scyliorhinus canicula) that intense shh expression first occurs in a bilaterally symmetrical pattern restricted to broad regions in each half of the dentition in the embryo jaw. As in the mouse, there follows a changing temporal pattern of shh spatial restriction corresponding to epithelial bands of left and right dental fields, but also a subfield for symphyseal teeth. Then, intense shh expression is restricted to loci coincident with a temporal series of teeth in iterative jaw positions. The developmental expression of shh reveals previously undetected timing within epithelial stages of tooth formation. Each locus at alternate, even then odd, jaw positions establishes precise sequential timing for successive replacement within each tooth family. Shh appears first in the central cusp, iteratively along the jaw, then reiteratively within each tooth for secondary cusps. This progressive, sequential restriction of shh is shared by toothed gnathostomes and conserved through 500 million years of evolution.

Osteology of Florenciella lugubris (Percoidei: Epigonidae)

The osteology of Florenciella lugubris is described. F. lugubris is attributed to the family Epigonidae on the basis of specific characters of structure of orbital bones, skull, jaws and hyoid, presence of three principal spines on operculum, contact of pterygiophores of dorsal fins, 10 + 15 vertebrae, extension of the lateral line onto the caudal fin, structure of the first hemapophysis and interhaemale, caudal skeleton, etc. At the same time, Florenciella is more advanced in comparison with Epigonus having such characters as presence of enlarged, directed to sides and/or forward symphyseal teeth in jaws, of finely and densely denticulatd edges of infraorbitalia 2–8 and of the orbiral edge of frontale, and fontanelle in bulla otica and having specific traits of denticulation of opercular bones, having no separated distal element in the free pterygiophore between the first and second dorsal fins, having modified scales, etc. The related genera Florenciella and Rosenblattia may be synonyms.

The first record of Helicoprion Karpinsky (Helicoprionidae) from China

A new species, Helicoprion jingmenense sp. nov., from the Lower Permian Qixia Formation of Hubei Province, China, is described based on a nearly complete symphyseal tooth spiral preserved as part and counterpart. The specimen is a large elliptical symphyseal tooth spiral with \( 4{\raise0.5ex\hbox{$\scriptstyle 1$} \kern-0.1em/\kern-0.15em \lower0.25ex\hbox{$\scriptstyle 3$}} \) volutions, with cutting blade being relatively wide, and its width being greater than the height after 3½ volution, middle portion being higher than the cutting blade, narrowed base being short. There is a distinct space not covered by enameloid in two adjacent tooth crowns in the outermost two volutions; the height of the compound root is moderate, and the ventral groove is about 1/10 of the same tooth crown. In comparison with other known Helicoprion species of the world, the new species resembles H. ferrieri and H. bessonowi. However, it can be easily distinguished from H. ferrieri by the wider cutting blade, the shorter narrowed base and lower compound root, and also from H. bessonowi by its more narrowed compound root and less than 39 tooth crowns per volution. Helicoprion jingmenense sp. nov. is obviously different from helicoprionid species previously found in China in general shape, size and histology. However, it is very difficult to identify their relationships because of the fragmentary nature of holotypes of the latter. Because the new specimen is the first record of Helicoprion and the most complete fossil dentition of helicoprionids from China, the new species is of significance for biostratigraphy and paleobiogeography.

Cranial morphology and ontogeny of the Permo-Carboniferous temnospondyl Archegosaurus decheni Goldfuss, 1847 from the Saar–Nahe Basin, Germany

ABSTRACTMorphology and ontogenetic changes in the skull and hyobranchium of the Permo-Carboniferous temnospondyl Archegosaurus decheni from the Saar–Nahe Basin (SW Germany) are described in detail, based on 181 skulls ranging from 18 to 279 mm in length. Three-dimensional skull reconstructions including the palate of different growth stages are provided. The extremely elongate choanae and up to four median symphyseal teeth are unique to A. decheni. Among neurocranial elements, the exoccipital is well ossified and forms the paroccipital process as in stereospondyls. The shaft of the stapes which projects into the squamosal embayment grows with positive allometry and possesses a distinct lateral process. The basibranchial is well ossified in adults and exhibits a complex, spoon-like morphology. Small larvae were euryphagous and used non-directed suction and jaw prehension during prey capture. Larger larvae and adults were mainly ichthyophagous, as is indicated by the increasingly elongated snout, differentiation of marginal teeth, and nutrition remains. After a prolonged larval period, juvenile and adult A. decheni remained in the aquatic habitat, as suggested by the presence of lateral line sulci, the ‘aquatic type’ of septomaxilla and choana, and the absence of a nasolacrimal duct.

Possible pathology in the snout and lower jaw of the Chinese Devonian lungfish,Sorbitorhynchus deleaskitus(Osteichthyes: Dipnoi)

ABSTRACT The holotype and only known specimen of Sorbitorhynchus deleaskitus, a large Devonian lungfish from Guangxi, China, is abnormal in the structure of the snout and lower jaw. The tooth plates show marked asymmetry and do not occlude when the jaws are placed in normal articulation. There is a large hemispherical depression with sinus tracts in the bone between the lower tooth plates. Both snout and lower jaw are abnormal in shape and only traces remain of ossified sensory tubules within the bone of the snout and mandible. The lower jaw of S. deleaskitus may have included a dentigerous cyst that developed from a persistent juvenile symphyseal tooth and grew large enough to distort the symphysis and cause malocclusion between the tooth plates. The cyst may have become infected, forming an abscess with sinus tracts in the bone below, and hyperplastic or neoplastic cells from the cyst may have spread to destroy normal sensory structures in the snout and lower jaw. If this interpretation is correct, the ...