Enamel Band Research Articles

New Early Cretaceous zalambdalestid stem placental mammal from Mongolia and evolution of Zalambdalestidae

ABSTRACT Prozalambdalestes cratodus gen. et sp. nov. is based on a fragmentary dentary from the Lower Cretaceous (Aptian–Albian) Khovoor locality in Gobi Desert, Mongolia. This is the largest eutherian in the Khovoor mammal assemblage. It shows dental specializations of Zalambdalestidae such as procumbent, ever-growing gliriform first lower incisor with restricted enamel and reaching posteriorly p5, and mesiodistally compressed lower molar trigonids. The enamel is restricted to the ventrolabial and ventrolingual sides of the mesial half of the incisor and the enamel band is higher on the labial side. The new taxon retains five lower premolars, with p1 smaller than p2 and p3 smaller than adjacent premolars, and the Meckelian groove. It also differs from other zalambdalestids by position of mental foramina (under p3 and p5), p1–3 obliquely set in dentary, and lower molar talonids wider than trigonids. Phylogenetic analysis places Prozalambdalestes gen. nov. in a polytomy with Albian Zhangolestes, Turonian Kulbeckia, and the clade of Campanian zalambdalestids from Mongolia and Kazakhstan. CT data in Zalambdalestes and comparison with Prozalambdalestes gen. nov. show that the four lower premolars in Zalambdalestes are p2, p3 (variable present), p4, and p5. Consequently, the three lower premolars of Barunlestes and Zofialestes are p2, p4, and p5. The other diagnostic characters of Zalambdalestidae are reviewed.

Phenotypic variability in LAMA3-associated amelogenesis imperfecta.

Amelogenesis imperfecta (AI) is defined as inherited enamel malformations. LAMA3 (laminin alpha-3) encodes a critical protein component of the basement membrane (laminin-332). Individuals carrying heterozygous LAMA3 mutations have previously been shown to have localized enamel defects. This study aimed to define clinical phenotypes and to discern the genetic etiology for four AI kindreds. Whole-exome analyses were conducted to search for sequence variants associated with the disorder, and micro-computed tomography (μCT) to characterize the enamel defects. The predominant enamel phenotype was generalized thin enamel with defective pits and grooves. Horizonal bands of hypoplastic enamel with chalky-white discoloration and enamel hypomineralization were also observed and demonstrated by μCT analyses of affected teeth. Four disease-causing LAMA3 mutations (NM_198129.4:c.3712dup; c.5891dup; c.7367del; c.9400G > C) were identified. Compound heterozygous MMP20 mutations (NM_004771.4:c.539A > G; c.692C > T) were also found in one proband with more severe enamel defects, suggesting a mutational synergism on disease phenotypes. Further analyses of the AI-causing mutations suggested that both α3A (short) and α3B (long) isoforms of LAMA3 are essential for enamel formation. Heterozygous LAMA3 mutations can cause generalized enamel defects (AI1A) with variable expressivity. Laminin-332 is critical not only for appositional growth but also enamel maturation.

Flexural Strength, Elastic Modulus and Remineralizing Abilities of Bioactive Resin-Based Dental Sealants.

Objective: To assess the remineralizing abilities and compare the flexural strength and elastic modulus of different bioactive pit and fissure sealants. Materials and Methods: Human enamel samples were randomly and blindly sealed with one of the following bioactive materials: BioCoat (Bc), ACTIVA KIDS (Av) and BeautiSealant (Bu). Seal-it (Si) was used as a non-bioactive sealant beside a control blank (B) group with no sealant. The sealed samples were subjected to a pH-cycling model (7 days of demineralization–remineralization cycles). The enamel surface hardness change (SHC), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) and polarized light microscopy were used to assess the remineralizing abilities of the studied sealants. Flexural strength and elastic modulus were also assessed following the ISO 4049 protocols. One-way analysis of variance (ANOVA) was used to analyze the results. Results: Bc sealant showed the highest FS and EM (p < 0.05). The contact with Bc and Bu sealants showed significantly lower %SHL (p < 0.05) in comparison to the other. These findings were supported by the results of SEM-EDX and polarized imaging by showing higher percentages of calcium and phosphate ions with the former sealants and thinner demineralized enamel bands. Conclusion: In this study, Bc showed the highest flexural strength. Bc and Bu sealants outperformed the other studied sealants in terms of their remineralization abilities.

Comparative scanning electron microscope analysis of the enamel of permanent human, bovine and porcine teeth.

BackgroundBovine and porcine teeth are often used in in vitro experiments as substitutes of human teeth.ObjectivesThe aim of the present study was to perform a comparative analysis of enamel morphology of permanent human, bovine and porcine teeth under the scanning electron microscope.MethodsAs many as 10 human, 10 bovine, and 10 porcine teeth were studied. All the teeth were sectioned and the halves were randomly divided into 2 groups according to the examined tissue (vestibular enamel at the mid-height of the dental crown and in the cervical area). Human and bovine enamel was etched for 15 sec and porcine enamel for 30 sec. The scanning electron microscope analysis was performed. The length and width of enamel prisms were determined with the “Met-Ilo” 1.1 computer program.ResultsAll enamel samples revealed the same etching pattern—Silverstone's type 2. Bovine enamel showed a similar porosity and the amount of interprismatic enamel compared to human enamel while the amount and width of interprismatic enamel bands in porcine enamel were evidently greater. The shape of the porcine prisms was visually similar to human prisms, although dimensions were significantly different. However, bovine prisms differed in form and appeared to be distinctly elongated.ConclusionsReported findings indicate that the results of experimental studies carried out on bovine and porcine enamel should not be compared with the results obtained on human enamel.

Testing Inner-Mesowear III on Goats (Capra aegagrus hircus) Fed Experimental Diets

The wear patterns on ungulate’s teeth help to understand dietary habits during an individual’s lifetime. Mesowear is a series of techniques used to detect tooth wear patterns at low magnification. While in mesowear I, and its simplified version mesowear II, the outer profile of a herbivore’s molar cusps is observed to assign a diet, mesowear III (or inner-mesowear) scores the wear facets on the inner enamel band of the tooth. This approach was developed to detect finer dietary signals for shorter periods than the two former mesowear methods. We tested this method on skulls of 26 goats (Capra aegagrus hircus) fed different diets for six months, for which mesowear I and II had already been scored. Our goal was to explore the effects of diets with varying abrasiveness on the dietary signal, comparing signals recorded with both techniques. We found no dif- ferences in mesowear III signals among diets, regardless of visible tendency of more abrasive diets leading to higher mesowear scores. We also found no difference in time resolution between mesowear III and I.

Enamel microstructure and morphometric discrimination of sympatric species of Microtus (Rodentia)

Prairie (Microtus ochrogaster) and woodland (Microtus pinetorum) voles, which exhibit distinctly different ecological preferences (grassland versus forest), commonly co-occur in paleontological deposits in eastern North America. Despite their ecological differences, their molar morphology is similar. Assuming that those ecologic differences occurred in the past, differentiation of these two taxa is important for paleoenvironmental reconstruction. A sample of 51 lower first molars from living populations were viewed via scanning electron microscope to qualify and quantify schmelzmuster (enamel microstructure) to species-specific standards applicable to the fossil record. The most obvious differences between schmelzmuster of the two taxa are the relatively thicker bands of radial enamel on the leading edges of triangles of M. ochrogaster, as well as the consistent retention of tangential or primitive tangential enamel on the trailing edges and posterior enamel band of the posterior loop of M. pinetorum. Discriminant analysis of landmark data from the same 51 specimens established morphological boundaries for these taxa and successfully separated the recent m1s of M. ochrogaster from those of M. pinetorum.To test identification confidence from previous work, and to add an independent means of identification for future work (at any site), both techniques were applied to a sample of three-closed triangle (“M. ochrogaster” type) m1s from the late Pleistocene Wapsipinicon Local Fauna of Jones County, Iowa. Identifications of the specimens from the Wapsipinicon l.f. based on schmelzmuster and morphometric analysis are consistent with those reached using traditional morphology. Such methods serve as independent “check” of traditional (qualitative) identification, highlight new species-level characters, and quantify previously described features, for discrimination of these taxa.

Choerolophodon (Proboscidea, Mammalia) from a new upper Miocene locality: Kivi-1 (Iran)

In this article, we report on two proboscidean upper tusks from a new locality in Iran, Kivi-1 (KIV). The tusks are oval to circular in cross-section, lack an enamel band, are strongly curved and double-twisted, and turn inwards at the tip. This morphology permits the attribution to Choerolophodon, an elephantimorph proboscidean well distributed during the Miocene in the Old World and already known from the late Miocene of Iran. Although the known upper tusks of Choerolophodon are few, the current data indicate that the curvature of the upper tusks may have biostratigraphic significance: in earlier and more primitive representatives from the early and middle Miocene of Eurasia, the curvature is less pronounced, whereas in the later and more derived ones from the late Miocene, it is strong. Based on this feature, we propose that the horizons from which these tusks derive date to the upper Miocene. During this epoch, two choerolophodont species were present in the Greco-Iranian palaeobiogeographic province, C. anatolicus and C. pentelici, the latter one well represented in the nearby Maragheh faunas. Because more diagnostic specimens are so far lacking, we attribute the KIV specimens to Choerolophodon sp. indet. “derived morph”. Based on the presence of either C. anatolicus or C. pentelici in KIV, a relatively open palaeoenvironment is assumed, in agreement with previous palaeoecological reconstructions from the wider region during this period.

New fossils of early and middle Miocene Choerolophodon from northern China reveal a Holarctic distribution of Choerolophodontidae

ABSTRACTAs one of the three major groups of gomphotheres, the Miocene Choerolophodontidae were long considered to have been distributed in Europe, Africa, and South Asia, with a few localities in East Asia, whereas choerolophodontids never extended into North America during the Miocene. In this paper, we report new Choerolophodon fossil materials from the early and middle Miocene of China, which suggest morphological similarities to the enigmatic North American Gnathabelodon thorpei. The new fossils were recovered from the lower Miocene of Linxia (C. guangheensis) and the middle Miocene of Junggar (Choerolophodon sp.) basins, suggesting the persistence of this genus in East Asia during the early–middle Miocene. The cheek tooth morphology of the new specimens resembles that of early–middle Miocene Choerolophodon from elsewhere (i.e., C. palaeindicus, C. kisumuensis, and C. chioticus), in addition to striking affinities with Gnathabelodon thorpei. The upper tusk and mandibular characters of G. thorpei, which include upwardly bent maxillary tusks without enamel bands, and elongated and trough-like mandibular symphysis without mandibular tusks, also support its relationship with the choerolophodontids. The occurrence of a possible member of Choerolophodontidae in the late Miocene of North America (i.e., G. thorpei) reveals intercontinental dispersals of choerolophodontids from East Asia across Beringia possibly between 16.0 and 11.0 Ma, at roughly the same time as other proboscideans, e.g., Mammutidae, Amebelodontidae, and Gomphotheriidae. Together, these new materials significantly revise previously established models of the geographic distribution, taxonomic diversity, and ecological adaptations of Choerolophodontidae within China and elsewhere across the Holarctic.

AHystrixLinnaeus, 1758 incisor (Mammalia, Rodentia) from the Early Pleistocene of Senèze, France

ABSTRACT Excavations carried out between 2001 and 2006 in the Early Pleistocene locality Seneze (Haute-Loire, France) yielded the fragment of a large upper incisor with anteriorly grooved enamel band, documenting a large-bodied rodent in Seneze for the first time. A thorough study of this incisor and particularly of its enamel microstructure led to its assignment to Hystrix refossa Gervais, 1852, despite the presence of longitudinal grooves which are usually considered as characteristic of the castorid genus Trogontherium Fischer von Waldheim, 1809 and which have not been noticed in Hystrix Linnaeus, 1758 so far. The presence of H. refossa is in accordance with the partly steppic environment previously documented in the Seneze locality.

On the relationship between enamel band complexity and occlusal surface area in Equids (Mammalia, Perissodactyla).

Enamel patterns on the occlusal surfaces of equid teeth are asserted to have tribal-level differences. The most notable example compares the Equini and Hipparionini, where Equini have higher crowned teeth with less enamel-band complexity and less total occlusal enamel than Hipparionini. Whereas previous work has successfully quantified differences in enamel band shape by dividing the length of enamel band by the square root of the occlusal surface area (Occlusal Enamel Index, OEI), it was clear that OEI only partially removes the effect of body size. Because enamel band length scales allometrically, body size still has an influence on OEI, with larger individuals having relatively longer enamel bands than smaller individuals. Fractal dimensionality (D) can be scaled to any level, so we have used it to quantify occlusal enamel complexity in a way that allows us to get at an accurate representation of the relationship between complexity and body size. To test the hypothesis of tribal-level complexity differences between Equini and Hipparionini, we digitally traced a sample of 98 teeth, one tooth per individual; 31 Hipparionini and 67 Equini. We restricted our sampling to the P3-M2 to reduce the effect of tooth position. After calculating the D of these teeth with the fractal box method which uses the number of boxes of various sizes to calculate the D of a line, we performed a t-test on the individual values of D for each specimen, comparing the means between the two tribes, and a phylogenetically informed generalized least squares regression (PGLS) for each tribe with occlusal surface area as the independent variable and D as the dependent variable. The slopes of both PGLS analyses were compared using a t-test to determine if the same linear relationship existed between the two tribes. The t-test between tribes was significant (p < 0.0001), suggesting different D populations for each lineage. The PGLS for Hipparionini was a positive but not significant (p = 0.4912) relationship between D and occlusal surface area, but the relationship for Equini was significantly negative (p = 0.0177). λ was 0 for both tests, indicating no important phylogenetic signal is present in the relationship between these two characters, thus the PGLS collapses down to a non-phylogenetic generalized least squares (GLS) model. The t-test comparing the slopes of the regressions was not significant, indicating that the two lineages could have the same relationship between D and occlusal surface area. Our results suggest that the two tribes have the same negative relationship between D and occlusal surface area but the Hipparionini are offset to higher values than the Equini. This offset reflects the divergence between the two lineages since their last common ancestor and may have constrained their ability to respond to environmental change over the Neogene, leading to the differential survival of the Equini.

A new species of Celebochoerus (Suidae, Mammalia) from the Philippines and the paleobiogeography of the genus Celebochoerus Hooijer, 1948

Celebochoerus is a unique suid having extremely large upper tusks, and which was to date only known from the Pliocene-Pleistocene of Sulawesi Island in Indonesia. Here, we report on the discovery of a canine fragment referable to Celebochoerus from the Cagayan Valley of Luzon, Northern Philippines. We name a new species, Celebochoerus cagayanensis nov. sp., which differs from the Sulawesi species Celebochoerus heekereni in having mesial and distal enamel bands on the upper canines. We see these characteristics as symplesiomorphic in suids and propose a migration route from the Philippines to Sulawesi, possibly out of Taiwan, which would have occurred independently from the better known Pleistocene migration route from India into Java.

A combined-mesowear analysis of late Miocene giraffids from North Chinese and Greek localities of the Pikermian Biome

The family Giraffidae is represented by two extant taxa (Giraffa camelopardalis and Okapia johnstoni), both of which are committed browsers. During the late Miocene, however, the Pikermian Biome included more than 15 giraffid species with a wider range of dietary ecologies. To examine the diet of these taxa, we apply a novel combined approach using four variables from two methods of dental mesowear. We score the traditional outer mesowear, which evaluates the sharpness and relief of the labial-most paracone enamel band. We also apply inner mesowear, which evaluates the surface morphology of the lingual band of paracone enamel on the mesial and distal ends, as well as the junction point between the two. Using a database of 8 extant species (N=98) of browsing, grazing, and mixed feeding ruminants, we predict the diets 190 extinct giraffid specimens. The discriminant function analysis (DFA) of the extant taxa using all four mesowear variables predicted diet with greater accuracy than any single mesowear variable. We compare the dietary profiles of species found in four Pikermian Biome regions: Samos, Pikermi, North China, and Linxia Basin. We find differences in the giraffid diet throughout the Pikermian Biome: in the localities from Greece, a larger number of giraffids were predicted as browsers, whereas both Chinese regions included a larger number of mixed feeding individuals. Our inner and outer mesowear dietary predictions agree with previously studied ecomorphological paleodietary proxies. Our data supports the hypothesis that the late Miocene giraffids comprised a wider range of dietary habits than the living giraffe and okapi.

A new large beaver (Mammalia, Castoridae) from the early Miocene of Japan

ABSTRACTA new early Miocene large castorid, Minocastor godai gen. et sp. nov., from the Dota locality, Gifu Prefecture in central Japan, is described on the basis of dentaries and teeth. The material comes from the Kani basin, where limnofluviatile clay and sandstones of the Nakamura Formation (Mizunami Group) are exposed on the southern (left) bank of the Kiso River. It represents the richest sample of a Miocene small mammal in the Japanese fossil record thus far known. Based on jaw and tooth morphology, this new castorid most likely represents a primitive anchitheriomyine. However, it lacks the marked striations on the incisors that are characteristic of the advanced large, middle Miocene anchitheriomyines like Anchitheriomys and Amblycastor. The new castorid shares this dental feature with other primitive anchitheriomyines from Asia and North America, like Propalaeocastor, Oligotheriomys, and Miotheriomys. For these genera, a new tribe, Minocastorini, is proposed as sister group to the Anchitheriomyini. The incisor enamel microstructure of the new castorid largely exhibits plesiomorphic characters but also apomorphic features such as pseudo-pauciserial Hunter-Schreger bands. Additionally, the outer portion of the enamel band is rather thick in comparison to that of other beavers. Based on the rodent taxa associated with Minocastor godai gen. et sp. nov., Dota can be correlated with European Neogene mammal units MN 3/4. Magnetostratigraphic studies and radiometric dates obtained from the Mizunami Group indicate that Dota is more likely correlated with MN 3, with an absolute age of around 18.5 Ma.http://zoobank.org/urn:lsid:zoobank:org:pub:B1886424-1759-4BDA-A5CC-D122436E1A76 Citation for this article: Mörs, T., Y. Tomida, and D. C. Kalthoff. 2016. A new large beaver (Mammalia, Castoridae) from the early Miocene of Japan. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1080720.

Are Hypsodonty and Occlusal Enamel Complexity Evolutionarily Correlated in Ungulates?

The spread of grasslands and cooling climate in the Miocene contributed to an increasingly abrasive diet for ungulates. This increase in abrasiveness is proposed to select for both hypsodonty and increasing complexity of occlusal enamel bands. If these traits evolved in response to strong selection to resist tooth wear while feeding in grassland habitats, we might expect them to have evolved in a correlated fashion. If, on the other hand, there was a developmental or physiological constraint, or if selection was not strong on total enamel production, we would expect species to have evolved one or the other of these traits at a time, producing an uncorrelated, or even inversely correlated, pattern of trait evolution. To test these hypotheses, we examined the Occlusal Enamel Index (OEI) and Hypsodonty Index (HI) of 773 ungulate teeth. We tested the dependence of OEI on HI for the orders Artiodactyla and Perissodactyla using phylogenetic generalized least squares regression (PGLS). The two traits are not significantly correlated in the PGLS, for Artiodactyla and Perissodactyla. Despite their physical proximity, close functional utility, and conventional correlation, our results reject the hypothesis that HI and OEI are evolutionarily linked in these lineages, suggesting that selection to resist tooth wear was not so strong as to drive the overall evolutionary trajectory of both these traits at the same time.

Complexity of ruminant masticatory evolution.

The evolution of robust jaws, hypsodont teeth, and large chewing muscles among grazing ruminants is a quintessential example of putative morphological adaptation. However, the degree of correlated evolution (i.e., to what extent the grazer feeding apparatus represents an evolutionary module), especially of soft and hard tissues, remains poorly understood. Recent generation of large datasets and phylogenetic information has made testing hypotheses of correlated evolution possible. We, therefore, test for correlated evolution among various traits of the ruminant masticatory apparatus including tooth crown height, jaw robustness, chewing muscle size, and characters of the molar occlusal surfaces, using phylogenetic and nonphylogenetic comparative methods as well as phylogenetic evolutionary model selection. We find that the large masseter muscles of grazing ruminants evolved with the inclusion of grass in the diet, an increase in the proportion of occlusal enamel bands oriented parallel to the chewing stroke, and possibly hypsodonty. We suggest that the masseter evolved under two evolutionary regimes: i) selection for higher masticatory forces during chewing and ii) flattening of the tooth profile, which resulted in reduced tooth guidance and, thus, a requirement for more chewing muscle activity during each chewing stroke, in agreement with previous research. The linear jaw metrics (depth of the mandibular angle, mandibular angle width, and length of the superficial masseteric scar) all show correlated evolution with hypsodonty and the proportion of enamel bands oriented parallel to the chewing stroke. We suggest that changes in the shape of the mandible represent the combined effects of selection for a reorientation of the chewing stroke, so as to emphasize horizontal translation of the teeth, and accommodation of high-crowned teeth. Our analyses show that the ruminant feeding apparatus is an evolutionary mosaic with its various components showing both correlated and independent evolution.

A New Method of Tooth Mesowear and a Test of it on Domestic Goats

Mesowear III is a new form of mesowear that uses separately the mesial and distal surfaces of enamel band 2 of the upper second molar to differentiate between a browsing and a grazing diet. The enamel band of browsers is flat and planar, in grazers it contains gouges and sub-facets which eventually become round. Mesowear III scores these shapes on a scale 1–4; score 1 represents the typical browser and score 4 represents a typical grazer. Differences in diet can also be studied by observing the junction between the mesial and distal side of the enamel band (j point); the j point is sharper and well defined in browsers, while it is rounder or non-existent in grazers. Wild browsers, grazers, and mixed feeders separate well using mesowear III. The wild taxa data were similar to mesowear III of experimental goats that were fed a controlled grazing or browsing diet (species of plants known). In addition, the browsing versus the grazing goat mesowear III signal becomes more distinct from each other by 40 days of feeding. Mesowear III so far gives a finer signal than previous mesowear (I and II).

Tyrannosaurid teeth from the Lomas Coloradas Formation, Cabullona Group (Upper Cretaceous) Sonora, México

The Lomas Coloradas Formation (Cabullona Group, Upper Cretaceous) in the state of Sonora, Mexico, has yielded a great diversity of continental vertebrates, especially dinosaurs. In this study we describe, analyze and illustrate six theropod teeth (ERNO specimens) that were found isolated and surface collected. Identification of the specimens is based upon the methodology provided by Smith (2005), Smith et al. (2007) and Smith et al. (2005). The results showed that the ERNO teeth are comparable to those of tyrannosaurid dinosaurs and some of them probably correspond to a new taxon. Their referral to the Tyrannosauridae family is supported by the presence of semi-conical, laterally compressed crowns with an ovoid cross-sectional base; slightly offset carinae with chisel-shaped denticles that are wider labio-lingually than longer proximo-distally; and the presence of enamel wrinkles at the base of some denticles on the labial surface. These wrinkles are not prominent adjacent to the serrations but they take the form of high relief deep enamel bands across the labial and lingual crown faces. Statistical principal component analysis (PCA) and discriminant function analysis (DFA) corroborated the taxonomically assignation of these teeth into this family. Particularly, the DFA analysis yielded very interesting results. This analysis classified ERNO 8549, 8550, 8551 and 8552 specimens as belonging to Tyrannosaurus, so they represent the most southern record of this genus in Western North America. Finally, the misclassification of ERNO 005 and ERNO 006 specimens remains puzzling. It probably was the result of the presence of juvenile individuals.

L'odontologie deGomphotherium angustidens(Cuvier, 1817) (Proboscidea, Mammalia) : données issues du gisement d'En Péjouan (Miocène moyen du Gers, France)

Odontology of Gomphotherium angustidens (Cuvier, 1817) (Proboscidea, Mammalia): data from the Middle Miocene locality of En Péjouan (Gers, France). The dental anatomy of Gomphotherium angustidens (Cuvier, 1817), the commonest proboscidean in the faunal lists of the Middle Miocene of Europe, is detailed on the basis of the numerous fossils found at En Péjouan in the vicinity of Simorre (Gers, France), a locality of Astaracian age (mammal zone MN7 or MN7/8). The examination of the morphologic and biometric variation of tusks, premolars and molars, based on an unprecedented number of specimens of one species in one locality, yields several results. The first is a better understanding of the evolutionary level of G. angustidens during the Astaracian. A second is a better knowledge of dental characters and their variation. The presence or absence of both upper and lower incisors (tusks), due to sexual dimorphism, is documented. In females, when they exist, upper tusks are much reduced. The relation between shape and growth stages of evergrowing tusks is illustrated in relation to a dental-age scale based on crania and mandibles with different premolars and/or molars and different wear stages. Variation of the orientation of the enamel band of upper tusks and of the piriform transverse sections of lower tusks is directly observed based on numerous specimens. The upper tusks are slightly curved outwards; they are not much curved ventrally although they display a twist even on rather straight tusks: in lateral view they are slightly concave dorsally at the premaxilla, then rather straight, and finally ventrally curved at the tip. The fabrication of enamel is stopped on male upper tusks at the dental ages XVII–XVIII (that is, with worn M2/m2 and first loph [id] of M3/m3 worn). No lower tusk shows circular or flat transverse sections, even if the longitudinal sulcus (on both dorsal and ventral sides) is more or less marked; the dorsal wear facet is strong but short. The bunolophodont pattern of decidual premolars, premolars and molars is extremely variable. The range of this variation is understood in details through several parameters: 1) the subdivision of lophs(ids); 2) the shape of central conules and the resulting trefoiled wear figure; 3) the degree of subdivision of the central conules; 4) the posttrite conules; 5) the labial cristae of upper molars; 6) the development of the cingulum; 7) the degree of development of the fourth loph of M3s and of the fifth lophid of m3; and 8) the amount of cement. It appears that: 1) the binary subdivision of lophs(ids) is the rule, posttrite half lophs with three cusps are rare and variable on right and left sides; on upper molars, the mesoconelet is often fused with the anterior central conule; 2) the pretrite trefoiled wear figure of upper molars shows an enlargement of the posterior central conule compared to the anterior, and this asymetry is seen even on worn teeth — this trait seems to be significant at the Astaracian, especially for M2 and M3; 3) pretrite central conules are subdivided (“serridentine” pattern), or not, and variation can be seen of right and left molars of same individuals; 4) posttrite conules are weak or absent; 5) the labial cristae of upper molars (mainly postparacrista and premetacrista) have the shape of smooth ridges and are never strongly developed; 6) the cingulum is mostly weak on the pretrite side, the development of the postingulum is extremely variable, as that of the last loph(id); 7) all M3s are tetralophodont, even the teeth which bear weak fourth loph and only one postcingulum cusp show an entoflexus between third and fourth lophs; m3s have four or five lophids ; and 8) the cement is usually present in the interlophs (ids) and around the cusps. The biometric variation of molars, especially M3s and m3s, is compatible with the explanation of sexual dimorphism. As a consequence, the variation of the dental traits described at En Péjouan brings a rationale fo

Scaling and adaptations of incisors and cheek teeth in caviomorph rodents (Rodentia, Hystricognathi)

The South American hystricognath rodents are one of the most diverse mammalian clades considering their occupied habitats, locomotor modes and body sizes. This might have been partly evolved by diversification of their masticatory apparatus' structure and its ecological commitment, for example, chisel-tooth digging. In this phylogeny-based comparative study, we test the relationship between ecological behavior and mechanical features of their incisors and molariforms. In 33 species of nine families of caviomorph rodents, we analyze incisor attributes related to structural stress resistance and molar features related with grinding capacity, for example, second moment of inertia and enamel index (EI) (enamel band length/occlusal surface area), respectively. Most of these variables scaled isometrically to body mass, with a strong phylogenetic effect. A principal component analysis discrimination on the EI clustered the species according to their geographic distribution. We presume that selective pressures in Andean-Patagonian regions, on particular feeding habits and chisel-tooth digging behaviors, have modeled the morphological characteristics of the teeth. Subterranean/burrower ctenomyids, coruros, and plains viscachas showed the highest bending/torsion strength and anchorage values for incisors; a simplified enamel pattern in molariforms would be associated with a better grinding of the more abrasive vegetation present in more open and drier biomes.

Alloptox katinkae sp. nov. (Lagomorpha: Ochotonidae), westernmost Eurasian record of the genus from the early Middle Miocene vertebrate fauna of Litke 2 (N Hungary)

Alloptox katinkae sp. nov. (Ochotonidae: Lagomorpha) from the late MN5 of Litke 2 (early middle Miocene, N Hungary) is the northernmost record of the genus in Europe, and the westernmost record in Eurasia. The main peculiarities of the teeth of A. katinkae reside in their thick enamel band, p3 with large triangular, not indented anteroconid without enamel hiatuses, very reduced protoconid, large meta+entoconid, and P2 with convergent main flexa entering half of the tooth and bilobed metacone. A. katinkae shares most morphological and dimensional similarities with A. anatoliensis that actually is the geographically closest species and overlaps its chronologic range. The dental features of A. katinkae and analyses of the rest of the faunal assemblage of Litke 2 indicate that A. katinkae, contrarily to other congeneric species, lived in a wooded, wet environment. This study also evidences the problems related to the phylogeny of the genus Alloptox and the related palaeobiogeographical questions.