Variations in dietary patterns of living sloths revealed by finite element analysis of jaws.

Although extinct sloths exhibited a wide range of dietary habits, modes of locomotion, and occupied various niches across the Americas, modern sloths are considered quite similar in their habits. The dietary habits of living sloths can be directly observed in the wild, and understanding the mechanical behavior of their jaws during chewing through finite element analysis (FEA) provides a valuable validation tool for comparative analysis with their extinct counterparts. In this study, we used FEA to simulate the mechanical behavior of sloth mandibles under lateral mastication loads, using it as a proxy for oral processing. Our research focused on the six extant sloth species to better understand their diets and validate the use of FEA for studying their extinct relatives. We found that all living sloths have the predominancy of low-stress areas in their mandibles but with significant differences. Choloepus didactylus had larger high-stress areas, which could be linked to a reduced need for processing tougher foods as an opportunistic generalist. Bradypus variegatus and Choloepus hoffmanni are shown to be similar, displaying large low-stress areas, indicating greater oral processing capacity in a seasonal and more competitive environment. Bradypus torquatus, Bradypus pygmaeus, and Bradypus tridactylus exhibited intermediary processing patterns, which can be linked to a stable food supply in more stable environments and a reduced requirement for extensive oral processing capacity. This study sheds light on extant sloths' dietary adaptations and has implications for understanding the ecological roles and evolutionary history of their extinct counterparts.

Assessing the adductor musculature and jaw mechanics of Proterochampsa nodosa (Archosauriformes: Proterochampsidae) through finite element analysis.

Proterochampsids are a group of South American nonarchosaurian archosauromorphs whose general morphology has been historically likened to that of the extant Crocodylia, which purportedly exhibited similar habits by convergence. Taxa from the genus Proterochampsa, for example, show platyrostral skulls with dorsally faced orbits and external nares and elongated snouts that might indicate a feeding habit similar to that of crocodilians. Nonetheless, some aspects of their craniomandibular anatomy are distinct. Proterochampsa has comparatively larger skull temporal fenestrae, and a unique morphology of the mandibular adductor chamber, with a remarkably large surangular shelf and a fainter retroarticular region in the mandible. In light of this, we conducted biomechanical tests on a 3-dimensional model of Proterochampsa nodosa including the first Finite Element Analysis for proterochampsians and compared it with models of the extant crocodylians Tomistoma schlegelii and Alligator mississippiensis. Our analyses suggested that, despite the differences in adductor chamber, Proterochampsa was able to perform bite forces comparable to those modeled for Alligator and significantly higher than Tomistoma. However, the morphology of the surangular shelf and the adductor chamber of Proterochampsa renders it more prone to accumulate stresses resulting from muscle contraction, when compared with both analogs. The elongated lower jaw of Proterochampsa, like that of Tomistoma, is more susceptible to bending, when compared with Alligator. As a result, we suggest that Proterochampsa might employ anteriorly directed bites only when handling small and soft-bodied prey. In addition, Proterochampsa exemplifies the diversity of arrangements that the adductor musculature adopted in different diverging archosauromorph groups.

A three-dimensional geometric morphometric analysis of the morphological transformation of Caiman lower jaw during post-hatching ontogeny.

Shape ontogenetic changes of the lower jaw in crocodylians are poorly understood. In order to answer some questions related to the inter- and intraspecific morphological variation of the mandible of two extant Caiman species, we performed a three-dimensional geometric morphometric approach. For this purpose, we used landmarks and semilandmarks on two ontogenetic mandibular series of 48 and 15 post-hatching specimens of C. yacare and C. latirostris, respectively. We have also examined the relationship between these anatomical transformations and ontogenetic shifts in diet. We performed a principal component analysis (PCA) for the two species, and regression and partial least squares (PLS) analyses for each species, separately. As a result, species were segregated along the PC1 with specimens of C. yacare showing more gracile mandibles, and specimens of C. latirostris more robust ones. The PC2 and regression analyses showed an age gradient and represented ontogenetic shape changes. Adult caiman mandibles are higher and wider than juvenile ones, and shape changes are more conspicuous in C. latirostris. The PLS analyses showed a significant relationship between shape and diet. Morphological changes of the PLS1 of block-1 match with those of the regression analysis for both species. We have detected morphological transformations in areas where the musculature in charge of mandibular movements is attached. Common morphological changes occurring during ontogeny seem to reflect the same mechanical properties required for crushing and killing in both species, driven by an ontogenetic shift in the diet from invertebrates to vertebrates. Additionally, interspecific differences were also found to be correlated to ontogenetic changes in diet and could be related to dissimilar feeding mechanical requirements (e.g., stiffness and toughness of the item consumed), and to different habitat preferences. Robust mandibles would be more suitable for shallow and fully vegetated environments, as it can be seen in C. latirostris, whereas slender jaws seem to be more suitable for more aquatic species such as C. yacare.

Rapid Parallel Morphological and Mechanical Diversification of South American Pike Cichlids (Crenicichla).

Explosive bouts of diversification are one of the most conspicuous features of the tree of life. When such bursts are repeated in similar environments, it suggests some degree of predictability in the evolutionary process. We assess parallel adaptive radiation of South American pike cichlids (Crenicichla) using phylogenomics and phylogenetic comparative methods. We find that species flocks in the Uruguay and Iguazú River basins rapidly diversified into the same set of ecomorphs that reflect feeding ecology. Both adaptive radiations involve expansion of functional morphology, resulting in unique jaw phenotypes. Yet, form and function were decoupled such that most ecomorphs share similar mechanical properties of the jaws (i.e., jaw motion during a feeding strike). Prey mobility explained 6- to 9-fold differences in the rate of morphological evolution but had no effect on the rate of mechanical evolution. We find no evidence of gene flow between species flocks or with surrounding coastal lineages that may explain their rapid diversification. When compared with cichlids of the East African Great Lakes and other prominent adaptive radiations, pike cichlids share many themes, including the rapid expansion of phenotypic diversity, specialization along the benthic-to-pelagic habitat and soft-to-hard prey axes, and the evolution of conspicuous functional innovations. Yet, decoupled evolution of form and function and the absence of hybridization as a catalyzing force are departures from patterns observed in other adaptive radiations. Many-to-one mapping of morphology to mechanical properties is a mechanism by which pike cichlids attain a diversity of feeding ecologies while avoiding exacerbating underlying mechanical trade-offs. [Adaptive radiation; ecological opportunity; feeding kinematics; functional trade-off; hybridization; introgression.].

Novel information on the cranial anatomy of the tapejarine pterosaur Caiuajara dobruskii.

Caiuajara dobruskii is a tapejarid pterosaur from the Cretaceous of the 'Cemitério dos Pterossauros' (pterosaur graveyard) site, a unique pterosaur bonebed which is located at the municipality of Cruzeiro do Oeste (Paraná, Brazil). Preliminary inferences on Caiuajara morphology were founded on a few partial skeletons, with no detail on the skull anatomy. Here we describe a new specimen from the pterosaur graveyard site, which corresponds to the most complete skull of Caiuajara dobruskii known so far. Furthermore, we describe and compare other specimens including the holotype, a paratype, and several other undescribed specimens. The new specimen preserves the posterior portion of the skull, allowing a better comprehension of its morphology and provides an appreciation of the anatomic structures of the basicranium, enabling better interpretation of this region. We also described the lower jaw of Caiuajara, reporting a unique feature of its symphyseal which adds to the diagnosis for the species. A variability in the premaxillary crest is also noted in different specimens of Caiuajara, which might be interpreted as sexual dimorphism or ontogenetic variability. Therefore, those new findings allow a better comprehension of its skull and enables a more precise comparison between the skulls of those extinct flying reptiles.

On the homology of crocodylian post-dentary bones and their macroevolution throughout Pseudosuchia.

The lower jaw of early tetrapods is composed of several intramembranous ossifications. However, a tendency toward the independent reduction of the number of bones has been observed in the mandible of mammals, lepidosaurs, turtles, crocodiles, and birds. Regarding archosaurs, the coronoid and prearticular bones are interpreted to be lost during the evolution of stem-birds and stem-crocodiles, respectively, but the homology of the post-dentary bones retained in living pseudosuchians remains unclear. Here, we combine paleontological and embryological evidence to explore in detail the homology of the crocodylian post-dentary bones. We study the mandible embryogenesis on a sample of 71 embryos of Caiman and compare this pattern with the mandibular transformations observed across pseudosuchian evolution. In the pre-hatching ontogeny of caimans, at least five intramembranous ossification centers are formed along the margins of the internal mandibular fenestra (perifenestral centers) and, subsequently, merge to form the coronoid (three intramembranous centers), angular (one intramembranous center), and articular (one intramembranous and one chondral center). In the fossil record, an independent prearticular is lost around the base of Mesoeucrocodylia (optimized as reappearing in Thalattosuchia if they are placed within Neosuchia), and the coronoid is apomorphically lost in notosuchians. The integration of embryological and paleontological data indicates that most perifenestral centers are involved in the origin of the prearticular of non-mesoeucrocodylian pseudosuchians. These centers are rearranged during the evolution to contribute to different post-dentary bones in mesoeucrocodylians bolstering the idea that the coronoid and the articular of Crocodylia are not completely homologous to those of other diapsids.

Morphometric evaluation, locational relationship, and surgical significance of the maxillofacial region landmarks / Evaluación morfométrica, relación de ubicación e importancia quirúrgica de los puntos de referencia de la región maxilofacial

SUMMARY: The aim of this study was to examine the localization of the landmarks in the maxillofacial region and their relations with each other and to evaluate them morphologically and clinically. Our study included 41 dry adult human skulls of unknown age and sex of Anatolian population. Statistical analysis of the data obtained in our study was performed with SPSS v.20.0 software (IBM Corp., Armonk, NY, USA). Statistical significance was accepted as P ? 0.05. Whereas the mean right supraorbital depth (SOD) value was significantly greater than the mean left SOD value (p 0.05). Correlation values in our study varied between -0.156 and 0.612. The highest correlation value was obtained in the positive direction between the orbital height (OH) and supraorbital foramen-infraorbital foramen (SOF-IOF) measurements (r = 0.612, p < 0.001). We believe that measurements of the orbit, SOF, and IOF and our data on their localizations, along with the relationships that we observed in our study will allow surgeons to avoid damaging the neurovascular bundles during surgical interventions and local anesthesia procedures in the frontal, periorbital, and maxillofacial regions.

RESUMEN: El objetivo de este estudio fue examinar la localización de los hitos en la región maxilofacial y sus relaciones entre sí y evaluarlos morfológica y clínicamente. Nuestro estudio incluyó 41 cráneos humanos adultos secos de edad y sexo desconocidos de la población de Anatolia. El análisis estadístico de los datos obtenidos en nuestro estudio se realizó con el software SPSS v.20.0 (IBM Corp., Armonk, NY, EE. UU.). La significación estadística se aceptó como P ? 0,05. Mientras que el valor medio de la profundidad supraorbitaria derecha (SOD) fue significativamente mayor que el valor medio de la SOD izquierda (p 0,05). Los valores de correlación en nuestro estudio variaron entre -0,156 y 0,612. El mayor valor de correlación se obtuvo en la dirección positiva entre las medidas de altura orbitaria (OH) y foramen supraorbitario-foramen infraorbitario (SOF-IOF) (r = 0,612, p <0,001). Creemos que las mediciones de la órbita, SOF e IOF y nuestros datos sobre sus localizaciones, junto con las relaciones que observamos en nuestro estudio, permitirán a los cirujanos evitar dañar los haces neurovasculares durante las intervenciones quirúrgicas y los procedimientos de anestesia local en la zona frontal, periorbitaria. y regiones maxilofaciales.

New cladotherian mammal from southern Chile and the evolution of mesungulatid meridiolestidans at the dusk of the Mesozoic era.

In the last decades, several discoveries have uncovered the complexity of mammalian evolution during the Mesozoic Era, including important Gondwanan lineages: the australosphenidans, gondwanatherians, and meridiolestidans (Dryolestoidea). Most often, their presence and diversity is documented by isolated teeth and jaws. Here, we describe a new meridiolestidan mammal, Orretherium tzen gen. et sp. nov., from the Late Cretaceous of southern Chile, based on a partial jaw with five cheek teeth in locis and an isolated upper premolar. Phylogenetic analysis places Orretherium as the earliest divergence within Mesungulatidae, before other forms such as the Late Cretaceous Mesungulatum and Coloniatherium, and the early Paleocene Peligrotherium. The in loco tooth sequence (last two premolars and three molars) is the first recovered for a Cretaceous taxon in this family and suggests that reconstructed tooth sequences for other Mesozoic mesungulatids may include more than one species. Tooth eruption and replacement show that molar eruption in mesungulatids is heterochronically delayed with regard to basal dryolestoids, with therian-like simultaneous eruption of the last premolar and last molar. Meridiolestidans seem endemic to Patagonia, but given their diversity and abundance, and the similarity of vertebrate faunas in other regions of Gondwana, they may yet be discovered in other continents.

Can human maxillary premolars discriminate between sexes in South Asian populations? / ¿Pueden los premolares maxilares humanos discriminar entre sexos en las poblaciones del sur de Asia?

The studies have illustrated odontometric analysis can be used to determine the sexual dimorphism effect on size of the teeth in various populations. The main aim of the study was to identify the inter-cuspal-, bucco-lingual -dimensions and weight of human upper-arch pre-molars in males and females of different South Asian populations. These metrics can distinguish sex which can have application in mass disasters, archaeology of mingled human remains and the in unidentified or several ancestry. The sample size consisted of 60 orthodontically extracted maxillary pre-molars from Pakistani and Saudi Arabian populations respectively. For male and female groups of each population fifteen first and second maxillary premolars were collected respectively, stored in PBS solution. The weight of the individual teeth was recorded. Later, digitally pictures were captured parallel to the occlusal surface to measure maximal bucco-lingual and inter-cuspal dimensions using Image-J software. The dimensions and weights were compared using Students' t-test between males and females respective Pakistani and Saudi Arabian first (P1) and second (P2) maxillary pre-molars. The dimensions for male P1 and P2 were statistically significantly larger than that for females in both populations. Furthermore, wet-weight of pre-molars in males is significantly greater than females in both populations. The findings demonstrate maxillary pre-molars can discriminate between the sexes in various populations.

Las investigaciones han ilustrado que el análisis odontométrico se puede utilizar para determinar el efecto del dimorfismo sexual en el tamaño de los dientes en varias poblaciones. El objetivo principal del estudio fue identificar las dimensiones y el peso entre cúspides, buco-linguales y el peso de los premolares de la arcada superior humana en hombres y mujeres de diferentes poblaciones del sur de Asia. Estas medidas pueden distinguir el sexo y ser importante en desastres masivos, arqueología de restos humanos entremezclados y en ancestros no identificados. El tamaño de la muestra consistió en 60 premolares maxilares extraídos ortodóncicamente de las poblaciones de Pakistán y Arabia Saudita, respectivamente. Para los grupos de hombres y mujeres de cada población, se recogieron quince primeros y segundos premolares superiores respectivamente, almacenados en solución de PBS. Se registró el peso de los dientes individuales. Posteriormente se capturaron imágenes digitales paralelas a la superficie oclusal para medir las dimensiones máximas buco-linguales e intercúspides utilizando software Image-J. Las dimensiones y los pesos se compararon mediante la prueba t de Student entre lo premolares maxilares (P1) y segundos (P2) de hombres y mujeres paquistaníes y saudíes. Las dimensiones para P1 y P2 de los hombres fueron estadísticamente significativos mayores que para las mujeres en ambas poblaciones. Además, el peso húmedo de los premolares en los varones era significativamente mayor que el de las mujeres en ambas poblaciones. Los hallazgos demuestran que los premolares maxilares pueden discriminar entre los sexos en varias poblaciones.

Dentoskeletal and soft-tissue changes comparison between the Jasper Jumper and Twin Force Bite Corrector in Class II malocclusion patients: A retrospective study.

OBJECTIVE: This retrospective study aimed to compare the dentoskeletal and soft-tissue changes in Class II malocclusion patients treated with Jasper Jumper and Twin Force Bite Corrector associated with fixed orthodontic appliances. MATERIAL AND METHODS: The sample comprised 60 subjects divided into 3 groups. Patients with Class II malocclusion, mandibular retrusion, slight or no crowding and with no previous orthodontic treatment were eligible. Group 1 comprised 20 patients treated with the Jasper Jumper (JJ), with an initial age of 12.39 years. Group 2 comprised 20 patients treated with the Twin Force (TF), with an initial age of 11.83 years. The control group consisted of 20 untreated Class II subjects with an initial age of 12.13 years. Intergroup pretreatment comparisons were performed with One-way analysis of variance and intergroup treatment changes were compared with the Analysis of Covariance, both followed by Tukey test. RESULTS: The TF group showed greater increase in mandibular length (6.23mm±4.64, P=0.004) than the control group (2.94mm±1.75). The mandibular incisors in the experimental groups presented significantly greater labial inclination and protrusion than the control (Md1.NB; JJ: 4.19°±2.09; TF: 4.46°±6.83; control: 1.13°±2.08, P=0.000/Md1-NB; JJ: 1.95mm±1.45; TF: 1.74mm±1.79; control: 0.31mm±0.81, P=0.000). In addition, the treated groups also showed significantly improvement of the dental relationships (Overjet; JJ: -4.05mm±4.64; TF: -3.80mm±2.12; control: 0.05mm±1.12, P=0.000/Overbite; JJ: -2.52mm±1.46; TF: -2.93mm±2.13; control: -0.63mm±1.35, P=0.000). CONCLUSION: The Jasper Jumper and Twin Force associated to fixed appliances were effective in correcting Class II malocclusion with a combination of skeletal and dentoalveolar changes. However, the TF seems to provide more skeletal effects with greater maxillary growth restriction and mandibular length increase when compared to the JJ.

Differences in Cell Proliferation and Craniofacial Phenotype of Closely Related Species in the Pupfish Genus Cyprinodon.

Understanding the genetic basis for phenotypic differences is fundamental to the study of macroevolutionary patterns of biological diversity. While technological advances in DNA sequencing have made researching genetic variation in wild taxa routine, fully understanding how these variants affect phenotype requires taking the next step to investigate how genetic changes alter cell and tissue interactions that ultimately produce phenotypes. In this article, we investigate a role for cell proliferation as a developmental source of craniofacial diversity in a radiation of 3 species of Cyprinodon from San Salvador Island, Bahamas. Patterns of cell proliferation in the heads of hatching-age fish differ among species of Cyprinodon, and correlate with differences in allometric growth rate among the jaws of 3 distinct species. Regional patterns of cell proliferation in the head are complex, resulting in an unintuitive result in which lower levels of cell proliferation in the posterior head region are associated with the development of relatively larger jaws in one species. We combine these data with previously published morphological and genomic data to show how studying the mechanisms generating phenotype at the cellular and tissue levels of biological organization can help mechanistically link genomic studies with classic morphological studies.

Evaluación del Índice de Korkhaus en adultos chilenos con oclusión normal / Evaluation of Korkhaus Index in Chilean adult individuals with normal occlusion

El examen de modelos es una de las múltiples herramientas diagnósticas que posee la ortodoncia y ortopedia dentomáxilofacial. Los valores con que se construyó su norma estadística están basados en poblaciones específicas y no reflejan las diferencias morfológicas existentes en el complejo cráneofacial entre las distintas etnias. El propósito de esta investigación fue identificar las longitudes transversales y sagitales de los maxilares de la población adulta mestiza chilena con oclusión normal y compararlas con el índice de Korkhaus basado en una población adulta caucásica alemana. Se reclutaron 20 estudiantes de pregrado de la Facultad de Odontología de la Universidad de Valparaíso con oclusión normal. Se registraron ambas arcadas dentarias con yeso y se aplicó el índice de Korkhaus: se midió la longitud interpremolar, la longitud intermolar, la longitud anterior superior y la longitud anterior inferior. La comparación entre los valores de la muestra y los valores referenciales del índice de Korkhaus fue hecha con la prueba de rangos de Wilcoxon mediante el software estadístico STATA 15.0 y se consideraron significativos valores de p<0,05. Se encontró una diferencia estadísticamente significativa en el valor de la longitud anterior superior (p-0,013); para la longitud interpremolar (p-0,9552) la longitud intermolar (p-0,8223) y la longitud anterior inferior (p-0,0452) no se hallaron diferencias. La mayor magnitud de la longitud anterior superior de la arcada dentaria respecto a la población adulta caucásica alemana se debe al rasgo de protrusión dentaria presente en la población mestiza chilena, lo cual no altera las características de una oclusión normal.

The model exam is one of many diagnostic tools in orthodontics and dentomaxillofacial orthopedics. The values on which the statistical norm were constructed, are based on specific populations and they do not reflect the morphological differences in the craniofacial complex between the different ethnic groups. The purpose of this study was to identify the transverse and sagittal maxillary and mandibular lengths of the Chilean mestizo adult population with normal occlusion, and compare them with the Korkhaus index based on a German Caucasian adult population. For this study 20 undergraduate students with normal occlusion were recruited from the Faculty of Dentistry of the University of Valparaíso. Both upper and lower dental casts were obtained from each student, and Korkhaus index was applied: the interpremolar length, intermolar length, upper anterior length and lower anterior length were measured. Comparison between the values of the sample and the reference values of the Korkhaus index was made with the Wilcoxon range test using the STATA 15.0 statistical software and significant values of p <0.05 were considered. A statistically significant difference was found in the value of the upper anterior length (p-0.013); for the interpremolar length (p-0.9552) the intermolar length (p-0.8223) and the lower anterior length (p-0.0452) no differences were found. The greater magnitude of the dental arch upper anterior length compared to the German Caucasian adult population is due to dental protrusion present in the Chilean mestizo population, which does not affect the normal occlusion characteristics.

On a remarkable sexual dimorphic trait in the Characiformes related to the olfactory organ and description of a new miniature species of Tyttobrycon Géry (Characiformes: Characidae).

Among the order Characiformes, secondary sexual dimorphism is commonly associated to the occurrence of bony hooks on fins, shape and length of the dorsal and anal fins, and sexual dichromatism. The analysis of a new miniature Characidae species of the genus Tyttobrycon, described herein, yielded to the discovery of a sexually dimorphic trait related to nostril aperture and number of olfactory lamellae. In this type of dimorphism, mature males present larger nostril aperture and higher number of olfactory lamella than females. A dimorphic olfactory organ is for the first time recorded and described for a member of the Characiformes. Gross morphology and development of brain and peripheral olfactory organ of Tyttobrycon sp. n. are described and compared to other species of Characidae. It is hypothesized that such dimorphic trait is related to male-male detection during cohort competition in small characids. The new species of Tyttobrycon is diagnosed from its congeners by the number of branched anal-fin rays (19-21) and the absence of a caudal-peduncle blotch. It occurs in a small tributary of Rio Madeira basin, near to the limit between Brazil and Bolivia, Acre State, Brazil.

Expansión palatina rápida asistida con mini implantes / Rapid palatal expansion assisted by mini-screws

La atresia o estrechez del maxilar superior es una patología que observamos frecuentemente en nuestra práctica diaria. Es importante el diagnóstico a una edad temprana, no solo para resolver ortopédicamente dicha patología, sino también prevenir una posible cirugía ortognática en la adultez. La expansión palatina rápida es un recurso terapéutico ortopédico para la corrección de la discrepancia transversal esqueletal del maxilar superior, que se manifiesta clínicamente como mordida invertida posterior. Existen diversos tipos de disyuntores y técnicas para su realización. La llegada del anclaje absoluto con los mini-implantes abrió puertas que revolucionan conceptos clásicos de expansión.

Atresia or narrowing of the maxilla is a pathology that we frequently observe in our daily practice. It is important to diagnose at an early age, not only to solve orthopedically this pathology, but also to prevent a possible orthognathic surgery at an adult age. Rapid palatal expansion is an orthopedic therapeutic resource for the correction of the skeletal transverse discrepancy of the maxilla. This pathology manifests clinically as a posterior crossbite. There are different types of expanders and techniques for their realization. The arrival of the absolute anchorage with the mini-implants opened doors that revolutionized classic concepts of expansion

Potamotrygon marquesi, a new species of neotropical freshwater stingray (Potamotrygonidae) from the Brazilian Amazon Basin.

Potamotrygon marquesi, sp. nov., is described and compared with other species of Potamotrygon occurring in the Amazon Basin. The identity of this new species is supported by an extensive external and internal morphological study including coloration pattern, squamation, skeleton and ventral lateral-line canals. Morphometrics and meristics were used to further distinguish P. marquesi from congeners. Potamotrygon marquesi was first considered to fall within the range of variation found in P. motoro. However, even with an extensive variation in coloration observed in P. motoro, this new species presents a series of autapomorphies that confidently distinguishes it from what is understood as the morphological variation found in P. motoro. Additional morphological characters that diagnose P. marquesi include three angular cartilages, asymmetrical star-shaped denticles, a single regular row of spines on tail dorsum, lateral row of caudal spines near the sting insertion, dorsal disc background in beige and grey mixed with shades of grey and bearing open and closed bicolored rings, among others. Although presenting a gap of distribution along the west-east extension of the Amazon Basin, its diagnostic charactistics are consistent in both recorded regions. Our study supports the need for many morphological characters to robustly distinguish members of Potamotrygoninae considering their extremely variable dorsal disc color pattern.

Killing them softly: Ontogeny of jaw mechanics and stiffness in mollusk-feeding freshwater stingrays.

Durophagous predators consume hard-shelled prey such as bivalves, gastropods, and large crustaceans, typically by crushing the mineralized exoskeleton. This is costly from the point of view of the bite forces involved, handling times, and the stresses inflicted on the predator's skeleton. It is not uncommon for durophagous taxa to display an ontogenetic shift from softer to harder prey items, implying that it is relatively difficult for smaller animals to consume shelled prey. Batoid fishes (rays, skates, sawfishes, and guitarfishes) have independently evolved durophagy multiple times, despite the challenges associated with crushing prey harder than their own cartilaginous skeleton. Potamotrygon leopoldi is a durophagous freshwater ray endemic to the Xingu River in Brazil, with a jaw morphology superficially similar to its distant durophagous marine relatives, eagle rays (e.g., Aetomylaeus, Aetobatus). We used second moment of area as a proxy for the ability to resist bending and analyzed the arrangement of the mineralized skeleton of the jaw of P. leopoldi over ontogeny using data from computed tomography (CT) scans. The jaws of P. leopoldi do not resist bending nearly as well as other durophagous elasmobranchs, and the jaws are stiffest nearest the joints rather than beneath the dentition. While second moment has similar material distribution over ontogeny, mineralization of the jaws under the teeth increases with age. Neonate rays have low jaw stiffness and poor mineralization, suggesting that P. leopoldi may not feed on hard-shelled prey early in life. These differences in the shape, stiffness and mineralization of the jaws of P. leopoldi compared to its durophagous relatives show there are several solutions to the problem of crushing shelled prey with a compliant skeleton.

Baalsaurus mansillai gen. et sp. nov. a new titanosaurian sauropod (Late Cretaceous) from Neuquén, Patagonia, Argentina.

We describe a dentary of a new titanosaur sauropod, Baalsaurus mansillai, gen. et sp. nov. from the Late Cretaceous of Patagonia, Argentina. The material comes from the Portezuelo Formation, Neuquén Group. Titanosaur sauropods lower jaws are scarce and only nine taxa with dentaries have been described. There are two types of morphology in titanosaur dentaries; "L" shaped or "U" shaped based on the shape, without a phylogenetic issue. In this paper; we recognize a new taxa, Baalsaurus mansillai, represented by an "L" shaped dentary with three apomorphic characters that are not present in other taxa: dentary alveoli with 10 teeth in the anterior ramus, a ventrally and anteriorly inclined symphysis and a wide ventral Meckelian groove surrounded by a thin lamina that forms a keel on the ventral border of the dentary.

Central Cemento-Ossifying Fibroma: Clinical Imaging and Histopathological Diagnosis / Fibroma Cemento-Osificante Central: Diagnóstico Clínico, Imagenológico e Histológico

ABSTRACT: Central ossifying fibroma is a lesion in which diagnosis has proved intriguing and unclear for presenting clinical, radiographic, and even histopathological similarities to other types of lesions such as the fibrous dysplasia of bone and cement-bone dysplasia. It is a benign neoplasm of uncertain etiology and slow development in which the mandible is affected more frequently than the maxilla. We described a case of central cemento-ossifying fibroma involving the right mandible of a thirty-five-female patient by presenting its clinical, radiographic, and histological characteristic sand discussing some differential diagnoses.

RESUMEN: El fibroma cemento-osificante central es una lesión que requiere un diagnóstico diferencial ya que muestran similitud clínica, histológica y radiológica con la displasia fibrosa y con la displasia cemento-ósea. Esta lesión es un tumor benigno de etiología incierta, presenta crecimiento lento y afecta principalmente la mandíbula más que el maxilar. Se reporta un caso de un paciente de sexo femenino de 35 años, diagnosticada con fibroma cementoosificante central que le afectó el lado derecho de la mandíbula. Se describen las características clínicas, histológicas y radiológicas de la paciente y se discuten los diversos diagnósticos diferenciales.

Heterodonty and double occlusion in Manidens condorensis: a unique adaptation in an Early Jurassic ornithischian improving masticatory efficiency.

New materials of the ornithischian dinosaur Manidens condorensis highlight a strong heterodonty between the upper and lower dentitions and reveal a novel occlusion type previously unreported in herbivorous dinosaurs. The diamond-shaped maxillary teeth have prominent cingular entolophs in a V- to Z-shaped configuration that are absent in dentary teeth. These cingular entolophs bear denticles and serrations with vertical wear that is coplanar with the apical wear facets, supporting their involvement in chewing. The separated apical and basal wear in dentary teeth is consistent with the apical and cingular wear in maxillary teeth, indicating an alternate occlusion, an orthal jaw motion, and shearing interactions between marginal and cingular edges in a double occlusion. Measurements of the length and wear area along the marginal and cingular edges indicate that the latter are functionally equivalent to adding eight teeth to a maxillary toothrow of ten, almost doubling the lengths of cutting edges and the degree of intraoral processing, while maintaining a plesiomorphic skull anatomy, an adaptation to herbivory unique in Ornithischia.

Functional morphology of the cranio-mandibular complex of the Guira cuckoo (Aves).

The cranio-mandibular complex is an important structure involved in food capture and processing. Its morphology is related to the nature of the food item. Jaw muscles enable the motion of this complex and their study is essential for functional and evolutionary analysis. The present study compares available behavioral and dietary data obtained from the literature with novel results from functional morphological analyses of the cranio-mandibular complex of the Guira cuckoo (Guira guira) to understand its relationship with the zoophagous trophic habit of this species. The bite force was estimated based on muscle dissections, measurements of the physiological cross-sectional area, and biomechanical modeling of the skull. The results were compared with the available functional morphological data for other birds. The standardized bite force of G. guira is higher than predicted for exclusively zoophagous birds, but lower than for granivorous and/or omnivorous birds. Guira guira possesses the generalized jaw muscular system of neognathous birds, but some features can be related to its trophic habit. The external adductor muscles act mainly during food item processing and multiple aspects of this muscle group are interpreted to increase bite force, that is, their high values of muscle mass, their mechanical advantage (MA), and their perpendicular orientation when the beak is closed. The m. depressor mandibulae and the m. pterygoideus dorsalis et ventralis are interpreted to prioritize speed of action (low MA values), being most important during prey capture. The supposed ecological significance of these traits is the potential to widen the range of prey size that can be processed and the possibility of rapidly capturing agile prey through changes in the leverage of the muscles involved in opening and closing of the bill. This contributes to the trophic versatility of the species and its ability to thrive in different habitats, including urban areas.