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.     

First porcupine fossils (Mammalia,Rodentia) from the late Miocene of NW Iran,with notes on late Miocene–Pliocene dispersal of porcupines

This paper describes the first fossil porcupine remains from Iran. Four upper cheek teeth and two fragmentary lower incisors present sufficient characters for identification as Hystrix aryanensis, a species previously known from the late Miocene locality of Molayan (Afghanistan) estimated at ca. 7–8 Ma. The dental features of porcupines are discussed to show their systematic value and highlight evolutionary trends in late Miocene and Pliocene porcupines. This study also discusses the dispersal history of fossil porcupines in relation to paleobiogeographic provinces and environmental changes during late Miocene to late Pliocene time.     

Evolutionary and Biological Implications of Dental Mesial Drift in Rodents: The Case of the Ctenodactylidae (Rodentia,Mammalia)

Dental characters are importantly used for reconstructing the evolutionary history of mammals, because teeth represent the most abundant material available for the fossil species. However, the characteristics of dental renewal are presently poorly used, probably because dental formulae are frequently not properly established, whereas they could be of high interest for evolutionary and developmental issues. One of the oldest rodent families, the Ctenodactylidae, is intriguing in having longstanding disputed dental formulae. Here, we investigated 70 skulls among all extant ctenodactylid genera (Ctenodactylus, Felovia, Massoutiera and Pectinator) by using X-ray conventional and synchrotron microtomography in order to solve and discuss these dental issues. Our study clearly indicates that Massoutiera, Felovia and Ctenodactylus differ from Pectinator not only by a more derived dentition, but also by a more derived eruptive sequence. In addition to molars, their dentition only includes the fourth deciduous premolars, and no longer bears permanent premolars, conversely to Pectinator. Moreover, we found that these premolars are lost during adulthood, because of mesial drift of molars. Mesial drift is a striking mechanism involving migration of teeth allowed by both bone remodeling and dental resorption. This dental innovation is to date poorly known in rodents, since it is only the second report described. Interestingly, we noted that dental drift in rodents is always associated with high-crowned teeth favoring molar size enlargement. It can thus represent another adaptation to withstand high wear, inasmuch as these rodents inhabit desert environments where dust is abundant. A more accurate study of mesial drift in rodents would be very promising from evolutionary, biological and orthodontic points of view.     

The Early Aurignacian human remains from La Quina-Aval (France)

There is a dearth of diagnostic human remains securely associated with the Early Aurignacian of western Europe, despite the presence of similarly aged early modern human remains from further east. One small and fragmentary sample of such remains consists of the two partial immature mandibles plus teeth from the Early Aurignacian of La Quina-Aval, Charente, France. The La Quina-Aval 4 mandible exhibits a prominent anterior symphyseal tuber symphyseos on a vertical symphysis and a narrow anterior dental arcade, both features of early modern humans. The dental remains from La Quina-Aval 1 to 4 (a dm₁, 2 dm₂, a P⁴ and a P₄) are unexceptional in size and present occlusal configurations that combine early modern human features with a few retained ancestral ones. Securely dated to ∼33 ka ¹⁴C BP (∼38 ka cal BP), these remains serve to confirm the association of early modern humans with the Early Aurignacian in western Europe.     

A peculiar cave species of Tomocerus (Collembola,Tomoceridae, Tomocerinae) from Vietnam,with a discussion of the postantennal organ and prelabral chaetae in Tomocerinae

The first Tomocerus species with a postantennal organ (PAO) in the adult stage is described from Vietnam. Tomocerus postantennalis sp. n. differs from the other PAO-possessing tomocerid, Tomolonus reductus Mills, 1948, mainly in the morphology of PAO, the number of ocelli, the number of chaetae in trochantero-femoral organ and several features of the furca. The new species is placed in Tomocerus because of the presence of a toothlet on the outer basal mucronal tooth and the absence of the diagnostic character states of Plutomurus Yosii, 1956 and Aphaenomurus Yosii, 1956. Besides the presence of PAO, the new species is peculiar in having six prelabral chaetae, instead of four as in other Tomocerus species. The new species is similar to Tomocerus folsomi Denis, 1929 and Tomocerus ocreatus Denis, 1948 in the type of dental spines but different from them in the body colour, the relative length of antennae to body, the number of unguis inner teeth and the number of mucronal intermediate teeth.     

On the status of Isolophodon Roth, 1903 (Mammalia,Astrapotheria) and other little-known Paleogene astrapotheres from central Patagonia

Most of the 16 currently recognized astrapothere genera are well known through numerous specimens preserving at least almost complete dentition. One of the exceptions is the enigmatic genus Isolophodon Roth, 1903, based on very scant and fragmentary materials from Paleogene levels of central Patagonia. This taxon was ruled out from almost all taxonomic lists, although its validity has not been discussed by subsequent authors. We herein re-describe and discuss the taxonomic status of the species of Isolophodon. The type species, I. cingulosus Roth, 1903, is characterized by having lower cheek teeth with a much reduced hypoflexid, resembling derived uruguaytheriines, but lower-crowned and with three lower premolars, as in the species of Astraponotus Ameghino, 1901. This is the only astrapothere nominal species attributable to the Tinguirirican South American Land Mammal Age (SALMA, Early Oligocene). Isolophodon aplanatus Roth, 1903 (Casamayoran and Mustersan SALMAs, middle Late Eocene) has proportionally more elongated lower molars and a less developed paraflexid than the type species. Isolophodon would represent an early diverging lineage of astrapotheriids, in which some dental features evolved convergently with the more derived uruguaytheriines. Additionally, we describe other fragmentary but very significant specimens from Paleogene localities in central Patagonia (Argentina) attributable to the following taxa: cf. Scaglia kraglievichorum (Barrancan? subage), based on a partial upper molar nearly 60% larger than the type of Scaglia kraglievichorum Simpson, 1957; Astrapotheriidae gen. et sp. 1 (Barrancan? Subage, Middle Eocene), based on an isolated upper molar larger than any other Eocene astrapothere; Astrapotheriidae gen. et sp. 2, based on five isolated upper cheek teeth from “La Cantera” (Gran Barranca, Early Oligocene), characterized by a large, isolated hypocone and accessory cusps on P3-P4. These taxa enlarge the known diversity of Paleogene astrapotheres and document novel evolutionary patterns for these mammals.     

The dentition of a well-preserved specimen of <Emphasis Type="Italic">Camarasaurus</Emphasis> sp.: implications for function,tooth replacement,soft part reconstruction,and food intake

The basal macronarian genus Camarasaurus was the most common sauropod in the Upper Jurassic Morrison Formation of North America and is known from several complete and partial skeletons. The specimen used for this study is Camarasaurus sp. SMA 0002 from the Sauriermuseum Aathal, Switzerland. This specimen was found in the Howe-Stephens Quarry, Bighorn Basin, WY, USA. In this study, the dental morphology, characterized by the spatulate, broad-crowned teeth, the tooth replacement pattern, and the function of the dentition and its implications for food intake is described. Features such as the absence of denticles, the wrinkled pattern of the enamel, and the occurrence of large wear facets on older teeth are characteristic for Camarasaurus sp. A slab of sediment with soft tissue impressions ranging up to the middle part of the crown suggests the presence of a gingival soft tissue structure partially covering the teeth. The wrinkled enamel on the crown of the teeth of Camarasaurus sp. and other sauropods is interpreted as indication of this cover of gingival connective tissue. In addition, there possibly was a keratinous beak, which together with the gingiva held the teeth in the jaw and provided stability for teeth in which the root is almost completely resorbed.     

An Enigmatic Hypoplastic Defect of the Maxillary Lateral Incisor in Recent and Fossil Orangutans from Sumatra (<Emphasis Type="Italic">Pongo abelii</Emphasis>) and Borneo (<Emphasis Type="Italic">Pongo pygmaeus</Emphasis>)

Developmental dental pathologies provide insight into health of primates during ontogeny, and are particularly useful for elucidating the environment in which extant and extinct primates matured. Our aim is to evaluate whether the prevalence of an unusual dental defect on the mesiolabial enamel of the upper lateral incisor, thought to reflect dental crowding during maturation, is lesser in female orangutans, with their smaller teeth, than in males; and in Sumatran orangutans, from more optimal developmental habitats, than in those from Borneo. Our sample includes 49 Pongo pygmaeus (87 teeth), 21 P. abelii (38 teeth), Late Pleistocene paleo-orangutans from Sumatra and Vietnam (67 teeth), Late Miocene catarrhines Lufengpithecus lufengensis (2 teeth), and Anapithecus hernyaki (7 teeth). Methods include micro-CT scans, radiography, and dental metrics of anterior teeth. We observed fenestration between incisor crypts and marked crowding of unerupted crowns, which could allow tooth-to-tooth contact. Tooth size does not differ significantly in animals with or without the defect, implicating undergrowth of the jaw as the proximate cause of dental crowding and defect presence. Male orangutans from both islands show more defects than do females. The defect is significantly more common in Bornean orangutans (71 %) compared to Sumatran (29 %). Prevalence among fossil forms falls between these extremes, except that all five individual Anapithecus show one or both incisors with the defect. We conclude that maxillary lateral incisor defect is a common developmental pathology of apes that is minimized in optimal habitats and that such evidence can be used to infer habitat quality in extant and fossil apes.     

A fossil record of the Eastern clade of Blanus (Amphisbaenia: Blanidae) from the late Miocene of Ukraine

The fossil history of worm lizards in Eastern Europe is very patchy because of the small number of localities and the fragmentary vertebral material available. A new record of the genus Blanus from the late Miocene of the Egorovka 1 and 2 localities in Ukraine is reported here. Based on its dental morphology, Blanus from Egorovka differs from all extinct species of the genus and from the extant B. cinereus complex. It is most closely related to the Eastern clade of Blanus (B. strauchi complex) in having enlarged second and small third dentary teeth. Blanus from Egorovka is the second fossil record of the B. strauchi complex and the first record of the Eastern clade outside of its current geographical range. It indicates a wider past range of the Eastern European Blanus, including the northern Black Sea coastal area.     

Tooth development and histology patterns in lamniform sharks (Elasmobranchii,Lamniformes) revisited

The dentition of lamniforme sharks exhibits several characters that have been used extensively to resolve the phylogenetic relationships of extant taxa, yet some uncertainties remain. Also, the development of different teeth of a tooth file within the jaws of most extant lamniforms has not been documented to date. High‐resolution micro‐computed tomography is used here to re‐evaluate the importance of two dental characters within the order Lamniformes, which were considered not to be phylogenetically informative, the histotype and the number of teeth per tooth file. Additionally, the development and mineralization patterns of the teeth of the two osteodont lamniforms Lamna nasus and Alopias superciliosus were compared. We discuss the importance of these dental characters for phylogenetic interpretations to assess the quality of these characters in resolving lamniform relationships. The dental characters suggest that (1) Lamniformes are the only modern‐level sharks exhibiting the osteodont histotype, (2) the osteodont histotype in lamniform sharks is a derived state in modern‐level sharks (Elasmobranchii), (3) the osteodont type, conversely is convergently achieved when the clade Chondrichthyes is considered and thus might comprise a functional rather than a phylogenetic signal, and (4) there is an increase in the number of teeth per file throughout lamniform phylogeny. Structural development of the teeth of L. nasus and A. superciliosus is congruent with a previous investigation of the lamniform shark Carcharodon carcharias. J. Morphol. 277:1584–1598, 2016. © 2016 Wiley Periodicals, Inc.     

Intraspecific variation of Eolophiodon laboriense,a basal Lophiodontidae (Mammalia,Perissodactyla) from the early Eocene of Southern France

The Lophiodontidae is an emblematic and well-documented Eocene family of perissodactyls from Western Europe. However, after more than a century and a half of studies, lophiodontids still display a complex systematics associated with blurry intraspecific variation and a poorly known early radiation. The locality of La Borie, located near the city of Toulouse, France, has yielded numerous remains of Eolophiodon laboriense. This abundance of remains allows for the first time the study of the intraspecific variation of a basal lophiodontid. The variation has been investigated for dental and cranio-mandibular characters, notably dental polymorphism, size variation and sexual dimorphism. The intraspecific variation of E. laboriense is high with more than 20 polymorphic characters of the dentition, including many additional crests and conules. This dental polymorphism is similar to the one observed in the Bartonian lophiodontid Lophiodon lautricense. E. laboriense also displays an important degree of sexual dimorphism, with male specimens having broader and longer mandibles with larger canines than females. Despite this high intraspecific variation, the low size variation of teeth and the consistency of diagnostic characters strengthen the validity of the genus Eolophiodon and does not impact the previous lophiodontid phylogeny.     

Une espéce nouvelle ďophisaurus (lacertilia,anguidae) de ľoligocène des phosphorites du quercy. révision de la sous-famille des anguinae

Ophisaurus roqueprunensis is a new anguine species (Lacertilia, Anguidae) from the Oligocene of the Phosphorites du Quercy (France). Blade-like teeth are the main feature of the new taxon. Several characters demonstrate the monophyletic nature of the Anguinae subfamily. The Anguinae subfamily is now subdivided into three groups: the genusPseudopus, with enlarged (molariform) teeth at the rear of the dental row; the anguine lizards with blade-like teeth (caniniform) or theAnguis —Ophisaurus harti lineage and the AmericanOphisaurus lizards, a group that shares no derived character and, thus, is a metataxon.Ophisaurus roqueprunensis is placed within theAnguis- Ophisaurus harti lineage. Phyletic relationships within those three taxons are envisaged.     

Late Triassic dinosaur teeth from southern Belgium

Isolated Dinosaur teeth have been discovered in the Upper Triassic locality of Habay-la-Vieille, in southern Belgium. Ornithischia are represented by three dental morphotypes; two of them closely resemble isolated teeth from the Middle or Upper Jurassic of Portugal and England. The presence of sauropods in the Upper Triassic of Europe is confirmed. Sauropods already had a wide geographical distribution during the Latest Triassic, as fossils have been discovered in South Africa, Thailand and western Europe. At Habay-la-Vieille, sauropods and prosauropods co-existed at the end of the Triassic. Two dental morphotypes may tentatively be referred to as theropod dinosaurs. The study of isolated teeth indicates that dinosaurs were already well diversified in the Latest Triassic of western Europe. To cite this article: P. Godefroit, F. Knoll, C. R. Palevol 2 (2003) 3–11.     

Description of two new species of Santelmoa (Teleostei, Zoarcidae) from the Southern Ocean

Detailed examination of eelpouts in collected material from the Gerlache Strait and the Bellingshausen Sea, during the Spanish Antarctic Expeditions Bentart 03 and Bentart 06, and from the Bransfield Strait, during the Danish Galathea 3 Expedition, at depths between 1,056 and 1,837?m, revealed two undescribed species of Santelmoa Matallanas 2010. Herein, Santelmoa fusca sp. nov. and Santelmoa antarctica sp. nov. are described on the basis of twelve specimens. Santelmoa fusca can be separated from all other Santelmoa species by the following characters: mouth terminal; two posterior nasal pores; lateral line double; two irregular rows of palatine teeth; dorsal fin rays 109–113; anal fin rays 88–94; vertebrae 27–29?+?87–91?=?114–118; two pyloric caeca well developed; scales reduced to tail; pelvic fins and vomerine teeth present. Santelmoa antarctica can be separated from all other Santelmoa species by the following characters: mouth subterminal; two posterior nasal pores; suborbital pores seven (6?+?1); lateral line double; single row of palatine teeth; supraoccipital dividing the posterior end of frontals; central radials notched; dorsal fin rays 109–112; anal fin rays 89–93; vertebrae 27?+?89–92?=?116–119; two pyloric caeca well developed; scales, ventral fins and vomerine teeth present. Santelmoa fusca and S. antarctica can readily be separated from each other by squamation (reduced to tail vs. on the tail and on the posterior part of body); suborbital pore pattern (6?+?0 vs. 6?+?1), as well as several morphometric characters. The relationships of the two new species with congeners are discussed.     

The study of dental occlusion in ancient skeletal remains from Mallorca (Spain): A new approach based on dental clinical practice

Occlusal characteristics, fundamental to assess the presence of malocclusion, have been often unexplored in bioarchaeological analyses. This is largely due to the fragmented condition of the skeletal remains. By applying a method that considers dental and maxillary features useful to evaluate occlusion in ancient fragmentary material, the purpose of this work is to define the occlusal features and explore the causes of malocclusion in a mediaeval population from Mallorca. The findings of this study suggest that normocclusion was present in ca. 60% of the individuals (N = 31), and that some characteristics, such as molar relationship, were slightly different from those of modern populations. The analysis of the occlusal features revealed for example that open-bite was absent in 85% of the sample, posterior open-bite was completely absent and overbite and overjet were normal in around 90% of the individuals. Statistically significant correlations between canine and molar relationships and between molar relationship and dental wear of the superior and inferior canines and incisors were observed. In addition, wear could affect the curve of Spee. All these findings strengthen the hypothesis that in ancient times malocclusion was not as generalized as in modern times. Although the factors that lead to malocclusion throughout centuries could have several causes, we suggest that in this population dental wear, which is strongly associated with the diet, was the fundamental causing factor.     

The Skull of Stephanomys and a Review of Malpaisomys Relationships (Rodentia: Muridae): Taxonomic Incongruence in Murids

The cranial morphology of the extinct murid genus Stephanomys, previously known only by dental remains, is described here on the basis of partial skulls of three species of Pliocene age. Important cranial characters of the genus are a robust rostrum, a high zygoma, a wide zygomatic arch, a narrow interorbit, a large orbit, and an optic foramen in the backward position. In addition to some dental characters, Stephanomys shares most of these cranial traits with the extinct Malpaisomys from the Canary Islands. Some of these traits may be linked to the development of large eyes and life in a rocky environment. The peculiar dental pattern of Stephanomys (stephanodonty) is also present in some recent murids (Oenomys and Thamnomys) having a different skull morphology. A comparison with nine other extant genera of murids verified the relationship among Malpaisomys, Stephanomys, and Acomys, supporting our previous conclusion. Phenetic and cladistic analyses of 17 cranial and 23 dental characters show that skull morphology is phylogenetically informative but highly convergent and incongruent with other partial evidence based on dental and biochemical characters. The combined analyses of skull and teeth illustrate a case of mosaic evolution in murids.