Cusp Size Research Articles

Testing the patterning cascade model of cusp development in Macaca fascicularis mandibular molars

ObjectiveMolar crown configuration plays an important role in systematics, and functional and comparative morphology. In particular, the number of cusps on primate molars is often used to identify fossil species and infer their phylogenetic relationships. However, this variability deserves renewed consideration as a number of studies now highlight important developmental mechanisms that may be responsible for the presence of molar cusps in some mammalian taxa. Experimental studies of rodent molars suggest that cusps form under a morphodynamic, patterning cascade model of development (PCM) that involve the iterative formation of enamel knots. This model posits that the size, shape and location of the first-forming cusps determines the presence and positioning of later-forming cusps. DesignHere we test whether variation in accessory cusp presence in 13 Macaca fascicularis mandibular second molars (M2s) is consistent with predictions of the PCM. Using micro-CT, we imaged these M2s and employed geometric morphometrics to examine whether shape variation in the enamel-dentine junction (EDJ) correlates with accessory cusp presence. ResultsWe find that accessory cusp patterning in macaque M2s is broadly consistent with the PCM. Molars with accessory cusps were larger in size and possessed shorter relative cusp heights compared to molars without accessory cusps. Peripheral cusp formation was also associated with more centrally positioned primary cusps, as predicted by the PCM. ConclusionsWhile these results demonstrate that a patterning cascade model is broadly appropriate for interpreting cusp variation in Macaca fascicularis molars, it does not explain all manifestations of accessory cusp expression in this sample.

Precise reconstruction of the aortic valve using glutaraldehyde-treated autologous pericardium in new formula: a case report

BackgroundThe current study presents a novel and precise surgical technique for complete reconstruction of the aortic valve using glutaraldehyde-treated autologous pericardium in a patient with aortic valve disease and endocarditis. The technique aims to provide a more effective and reproducible method for aortic valve repair, with the goal of improving outcomes and quality of life for patients with aortic valve disease.Case presentationA 35-year-old Iranian male with aortic valve disease and endocarditis underwent aortic valve reconstruction surgery. Preoperative echocardiography showed a degenerative aortic valve with severe regurgitation, reduced left ventricular ejection fraction, and specific aortic root dimensions. The surgical technique involved precise measurements and calculations to design the size and shape of the new aortic valve cusps using autologous pericardium, with the goal of optimizing coaptation and function. The surgeon calculated the intercommissural distance based on the aortic annulus diameter to determine cusp size and shape. He tailored the pericardial cusps to have a height equal to 80% of the coaptation margin length. Detailed suturing techniques were used to ensure proper alignment and coaptation of the new cusps. Intraoperative evaluation of the valve function using suction and transesophageal echocardiography showed good coaptation and minimal residual regurgitation. At the 3-year follow-up, the patient had a well-functioning aortic valve with only trivial leak and was in satisfactory clinical condition.ConclusionsGlutaraldehyde-treated autologous pericardium is a validated leaflet alternative, and the causes of its failure are late annular dilatation and other technique breakdowns. Current evidence reveals that aortic valve reconstruction with glutaraldehyde-treated autologous pericardium is associated with many advantages with the potential to improve patient outcomes and quality of life. Further clinical studies are warranted to evaluate the long-term durability and efficacy of this approach.

Aortic valve cusp size and shape in dilated trileaflet aortic roots

ObjectivesThe objective of the study was to quantify the differences in cusp size and shape in patients with normal and dilated trileaflet aortic roots and in dilated roots with or without aortic regurgitation. MethodsA retrospective analysis of computed tomography studies in patients with normal and dilated trileaflet aortic roots was performed measuring root and cusp dimensions. Normal root size was defined as sinuses of Valsalva diameter less than 40 mm, dilated as 45 mm or greater. Root measurements normalized to basal ring diameter and cusp measurements normalized to geometric height were analyzed to assess the shape. Additionally, comparison of dilated roots with or without aortic regurgitation was made. ResultsWe analyzed 146 normal and 104 dilated aortic roots and 73 propensity-matched pairs. Dilated roots were larger in all dimensions and had increased ratio between commissural and basal ring diameter (1.58 ± 0.23 vs 1.11 ± 0.10, P < .001). Cusps in dilated roots were larger in all measured dimensions and were elongated with increased normalized cusp insertion length (3.64 ± 0.39 vs 3.26 ± 0.20, P < .001) and normalized free margin length (2.53 ± 0.30 vs 2.16 ± 0.19, P < .001). In patients with dilated root and no cusp prolapse (n = 83), those with moderate or severe aortic regurgitation had larger commissural diameter but similar cusp dimensions compared with those with no or mild aortic regurgitation. ConclusionsThe cusps in dilated roots elongate transversely and to a lesser degree radially. Functional aortic regurgitation is caused by extensive commissural dilatation and not by inadequate cusp adaptation.

889 ATRIOVENTRICULAR BLOCK, AN UNUSUAL CLINICAL PRESENTATION OF CALCIFIED BICUSPID AORTIC VALVE

Abstract Background Bicuspid aortic valve (BAV) is the most frequent congenital valve disease in adults. It is often associated with other congenital cardiac defects. Sometimes it is associated with aortic dilatation. BAV is an heterogeneous disease with varying valve morphology (asymmetrical cusp size and rafe), annulus geometry and size, asymmetrical calcification of the aortic valve and left ventricular outflow tract. Case Report A 32 year-old male patient was diagnosed with bicuspid aortic valve after several cardiologic visits for eligibility to competitive sport. Since April 2021 he developed a progressive exertional dyspnea for strenuous efforts. In February 2022, he was referred to our department after a Holter ECG showed a bradyarrhythmia with complete atrioventricular block. The echocardiography evaluation demonstrated a preserved ejection fraction and a bicuspid aortic valve with a mild-moderate regurgitation. The coronary computed tomography showed a thick and calcified bicuspid aortic valve with a coarse calcification of the anterior cuspid that involve the pars membranacea of the interventricular septum. The ergometric exercise demonstrated chronotropy incompetence. The tomography confirmed the mildy aortic root dilatation. Therefore, an MRI was performed and reported a small laminar LGE on the infero-lateral wall of the left ventricle, of unclear significance. He underwent Dual-Chamber permanent pacemaker implantation. A conservative approach was preferred over valvular replacement, considering the mild aortic root dilatation on a background of mild-to- moderate aortic insufficiency. Conclusion Our case is unusual given the bicuspid aortic valve concomitant with atrioventricular block, which was connected with the location of the calcification. Thus, the aim of our case report is, to describe a complication to this condition which, although rare, represents a different clinical presentation of the pathology itself in a young adult.

Preoperative Ozaki technique measures on tridimensional engineered root

BackgroundThe aortic valve neocuspidalization (AVNeo) is an innovative surgical technique aiming at the reconstruction of the aortic valve using autologous pericardium. One of the main criticisms to AVNeo is the longer duration of the aortic clamping time (ACT) as compared to standard aortic valve replacement due to the sizing of the valve neocusps. MethodsWe retrospectively enrolled 30 consecutives patients underwent AVNeo. For each patient we developed a 3D aortic root model (ARM) based on CT-scan datasets. We retrospectively compared the leaflets measurements performed during surgery with those obtained on the corresponding ARMs. ResultsIn 100% of cases no difference between the in vitro and in vivo measurements exceeded the acceptable error limit of 2 ​mm. The correlation of each single in vitro versus in vivo measurements demonstrates a strong coincidence between the two different methods of sizing (r ​> ​0,9, p ​< ​.0001). By analyzing the data considering the annulus perimeter and not the single cusp size, the perfect coincidence was to be found in 89.9% with a slight acceptable discrepancy (2 ​mm on total) in the remaining 10.1%. Conclusions3D-ARMs, printed from CT-scan, represent a reproducible process to obtain overlapping cusp sizes compared to those measured in-vivo, possibly reducing the ACT.

Echocardiographic changes in the shape and size of the aortic cusps in dogs with confirmed systemic hypertension.

Systemic hypertension (SH) in dogs typically occurs secondary to renal disease, diabetes mellitus, hyperadrenocorticism, malignant adrenal tumors, or various medications. Echocardiography performed on people with SH has shown asymmetric dilation of the sinuses at the level of the aortic valves, previously undescribed in canine patients. The objective of this retrospective case-control study was to determine if there was a difference in size and shape of the aortic cusps at the level of the sinus of Valsalva in dogs with SH compared to dogs with normal blood pressure. We reviewed echocardiographic findings in 74 dogs with SH and 37 dogs with normal blood pressure (NBP), defined as less than 150mmHg. Systemic hypertension was classified as mild (150-159mm Hg), moderate (160-179mm Hg), or severe (greater than 180mm Hg). There was a significant difference (P<.001) in the mean size of the aorta cusps at the level of the sinuses in 67 of 74 dogs with SH and none of 37 dogs with NBP. Of the 74 dogs with SH, 70 had left ventricular hypertrophy (18 asymmetric, 15 concentric, and 37 eccentric). Additionally, there was aortic root dilatation in 15 dogs, aortic insufficiency in 21, mitral regurgitation in 50, and left atrial enlargement in 71. The standard deviation of the three cusp measurements between the dogs with SH and dogs with NBP had a sensitivity of 92% and specificity of 97% for diagnosis of SH. Asymmetric size of the aortic cusps on echocardiography is therefore a reliable indicator of SH in dogs.

Senescence-accelerated mouse prone 8 (SAMP8) mice exhibit reduced entoconid in the lower second molar

ObjectiveThe position and size of the major cusps in mammalian molars are arranged in a characteristic pattern that depends on taxonomy. In humans, the cusp which locates distally within each molar is smaller than the mesially located cusp, which is referred to as “distal reduction”. Although this concept has been well-recognized, it is still unclear how this reduction occurs. Current study examined whether senescence-accelerating mouse prone 8 (SAMP8) mice could be a possible animal model for studying how the mammalian molar cusp size is determined. DesignSAMP8 mice were compared with parental control (SAMR1) mice. Microcomputed tomography images of young and aged mice were captured to observe molar cusp morphologies. Cusp height from cement-enamel junction and mesio-distal length of molars were measured. The statistical comparison of the measurements was performed by Mann-Whitney U test. ResultsSAMP8 mice showed reduced development of the disto-lingual cusp (entoconid) of lower second molar when compared with SAMR1 mice. The enamel thickness and structure was disturbed at entoconid, and aged SAMP8 mice displayed severe wear of the entoconid in lower second molar. These phenotypes were observed on both sides of the lower second molar. ConclusionsIn addition to the general senescence phenotype observed in SAMP8 mice, this strain may genetically possess molar cusp phenotypes which is determined prenatally. Further, SAMP8 mice would be a potential model strain to study the genetic causes of the distal reduction of molar cusp size.

The intraspecific diversity of tooth morphology in the large-spotted catshark Scyliorhinus stellaris: insights into the ontogenetic cues driving sexual dimorphism.

Teeth in sharks are shed and replaced throughout their lifetime. Morphological dental changes through ontogeny have been identified in several species and have been correlated with shifts in diet and the acquisition of sexual maturity. However, these changes were rarely quantified in detail along multiple ontogenetic stages, which makes it difficult to infer the developmental processes responsible for the observed plasticity. In this work, we use micro-computed tomography and 3D geometric morphometrics to describe and analyze the tooth size and shape diversity across three ontogenetic stages (hatchling, juvenile, and sexually mature) in the large-spotted catshark Scyliorhinus stellaris (Linnaeus, 1758). We first describe the intra-individual variation of tooth form for each sex at each ontogenetic stage. We provide a tooth morphospace for palatoquadrate and Meckelian teeth and identify dental features, such as relative size and number of cusps, involved in the range of variation of the observed morphologies. We then use these shape data to draw developmental trajectories between ontogenetic stages and for each tooth position within the jaw to characterize ontogenetic patterns of sexual dimorphism. We highlight the emergence of gynandric heterodonty between the juvenile and mature ontogenetic stages, with mature females having tooth morphologies more similar to juveniles' than mature males that display regression in the number of accessory cusps. From these data, we speculate on the developmental processes that could account for such developmental plasticity in S.stellaris.

Sculpteremaeus olszanowskii gen. nov., sp. nov. (Acari, Oribatida, Cymbaeremaeidae) from chaparral in California, USA, with a reassessment of Cymbaeremaeidae.

A new oribatid mite genus, Sculpteremaeus gen. nov. (Oribatida, Cymbaeremaeidae), with Sculpteremaeus olszanowskii sp. nov. as type species, is proposed and described based on adults. It is from sandy soil-litter in chaparral of California, USA, an environment from which no oribatid mites have been recorded previously. Based on an analysis of adults of all genera of Cymbaeremaeidae, the new genus is closely related to Ametroproctus, from which it is most easily distinguished by the morphology of lamellae, size of lamellar cusps, and shape of the tutorium. We expand the Cymbaeremaeidae family diagnosis, and question the inclusion of Scapheremaeus based on extensive molecular evidence showing its closer relationship with Ameronothroidea and Licneremaeoidea.

Rotating ice cusps on ship's bow shoulder: Full-scale study on the cusp sizes and corresponding peak loads in different ice and operational conditions

The ice loads occurring in ship-ice interaction are uncertain for many reasons. This article addresses some of those uncertainties by studying adjacent frames and identifying cases where the peak ice load occurs on a certain frame. In these cases, we looked at photos of ice to identify what type of an ice response caused the load to peak. We further selected the cases where the peak load was caused by a rotation of an already broken ice cusp. This rotation allowed us to measure the cusp dimensions from the photos, which enabled us to study two research questions. First, how the cusp area distribution is affected by the ice thickness and ship speed. Second, how the peak load distribution is affected by the cusp dimensions and ship speed. Both of these questions were modeled with hierarchical Bayesian models, where the Gaussian process priors compel the distribution parameters to smoothly change in varying conditions. The models predict that the cusp area increases with increasing ice thickness and deceasing ship speed, whereas the peak load increases with increasing cusp volume and decreasing ship speed. The models were tested with posterior predictive checks, which demonstrated good agreement with the models and the measurements.

A diminutive Pliocene guenon from Kanapoi, West Turkana, Kenya

Although modern guenons are diverse and abundant in Africa, the fossil record of this group is surprisingly sparse. In 2012 the West Turkana Paleo Project team recovered two associated molar teeth of a small primate from the Pliocene site of Kanapoi, West Turkana, Kenya. The teeth are bilophodont and the third molar lacks a hypoconulid, which is diagnostic for Cercopithecini. The teeth are the same size as those of extant Miopithecus, which is thought to be a dwarfed guenon, as well as a partial mandible preserving two worn teeth, previously recovered from Koobi Fora, Kenya, which was also tentatively identified as a guenon possibly allied with Miopithecus. Tooth size and proportions, as well as analysis of relative cusp size and shearing crest development clearly separate the fossil from all known guenons. Based on the Kanapoi material, we erect a new genus and species, Nanopithecus browni gen. et sp. nov. The small size of the specimen suggests either that dwarfing occurred early in the lineage, or at least twice independently, depending on the relationship of the new species with extant Miopithecus. Further, the distinctive habitat and geographic separation from Miopithecus suggests that the origin of small body size is not uniquely linked to the current habitat of Miopithecus, and possibly that relatives of extant Miopithecus were much more widely distributed in the past. This in turn argues caution in using extant biogeography in models of the origins of at least some guenons.

Is small cusp size a limitation for aortic valve repair?†.

We sought to investigate cusp size limitations for valve repair in patients with aortic regurgitation (AR). Preoperative computed tomography was performed in 105 patients. Cusp geometric height (GH) and annulus size were measured. Mean patient age was 60.7 ± 13.7 years. Mean GH of 3 cusps was used in the analysis. Annulus cusp mismatch was graded using predicted coaptation length. Patients were categorized by mean GH into group S (GH <16 mm; n = 35) or L (GH ≥16 mm; n = 70). Preoperative mean GH was 17.1 ± 2.3 mm. GH and body height were significantly correlated (r = 0.61). Intraoperative mean GH (18.8 ± 2.2 mm) was larger than preoperative mean GH (P < 0.0001). However, postoperative (17.1 ± 2.0 mm) and preoperative mean GH did not differ. Moderate AR was not present on predischarge echocardiography. Mild AR was observed in 51% and 17% of patients in groups S and L, respectively (P = 0.006). During follow-up, moderate or severe AR was observed in 14% and 10% of patients in groups S and L, respectively (P = 0.74). Two patients in group S required reoperation for a regurgitant valve. Twenty (83%) and 15 (21%) patients in groups S and L, respectively, had severe annulus cusp mismatch before surgery. Annulus cusp mismatch resolved in most patients in group L postoperatively, whereas more than half the patients in group S still had severe mismatch. Small cusp size (GH <16 mm) is not necessarily a contraindication in aortic valve repair. However, most patients in this group had annulus cusp mismatch. Root replacement or secure annulus plication is mandatory to correct annulus cusp mismatch.

Social inequality, human development and fertility pattern in Brazil, 2000-2010

Abstract Objectives: to analyze the fertility pattern in Brazil and its relationship with human development in the Brazilian federation units in 2000 and 2010. Methods: this is an ecological study whose unit of analysis was the Brazilian Federative Units in the period of 2000 and 2010. The fertility was assessed considering the social (HDI), inequality, (Gini, Theil and Income Ratio) and fertility indicators (fertility rate and mean age of fertility). Results: Brazil has been experiencing a rapid fertility transition. The pattern of fertility curves changed in all Federative Units between 2000 and 2010, with a reduction in cusp size and postponement of fecundity. This change was more evident among the Federative Units with better development and lower inequality. The correlation between social and fertility indicators lost strength in the period, corroborating the transition hypothesis. Conclusions: there is a direct relation between the fecundity and inequality indicators, and inversing human development. Changes should be taken in consideration in the age structure of the population, as well as inequality indicators, for better planning in public policies for public health.

A Study of Cusp Base Areas in the Maxillary Permanent Molars of American Whites

The focus of this descriptive study was toexplore the patterns of variation of base crown areas forthe four major cusps on the maxillary first and secondpermanent molars in a cohort of contemporary NorthAmerican whites of western European descent. Acomputer-assisted photogrammetric method was usedto measure two-dimensional areas of the cusps. Rankingof mean cusp size was the same for M1 and M2, namelyprotocone &gt; paracone &gt; metacone &gt; hypocone. In concertwith field theory, size decreased while variability (CV)increased across this same sequence. Overall area of M1(97 mm2) is 13% larger than M2 (86 mm2) in this sample.Most cusps exhibited significant sexual dimorphism,with greater differences for the distal cusps within atooth and from M1 to M2. Intercorrelations of cusp areaswere notably low (r2 &lt; 15%) both within and betweenM1 and M2, suggesting considerable independence informative rates of each cusp and low morphologicalintegration of these constituents of the occlusal table.Limited comparative material in the literature suggeststhat cusp areas may valuably extend the quantitativecomparisons for genetic and biological studies beyondconventional tooth crown width and length.

Templates of flat pericardial patterns for precise aortic cusp extension

Background Aortic cusp extension is a subjective and operator-dependent technique. In order to facilitate surgical correction of aortic cusp retraction and reestablishment of adequate cusp coaptation, we sought to develop new templates that can be used to cut flat pericardial sheets into precise cusp extension patches. Methods Each template was designed as a two-dimensional unwrap of the natural geometry of a complete aortic cusp, and a series of templates were made available to correspond with all potential aortic cusp sizes. Based on these templates, aortic cusp extension was performed in 2 patients (aged 54 and 43 years) with significant retraction of the noncoronary aortic cusps and severe aortic valve insufficiency. In each patient, extension of the retracted native noncoronary cusp was undertaken using a bovine pericardial patch that matched the size of adjacent nondiseased native aortic cusps. Results Achieving geometrically perfect aortic cusp extensions was uncomplicated, and intraoperative transesophageal echocardiography confirmed satisfactory aortic valve repairs (aortic insufficiency < 1+ and low transvalvular gradients). Early follow-up transthoracic echocardiography confirmed that all valve cusps met at similar heights in the aortic root, and that their excursions were virtually identical. Conclusions The newly designed templates can be used to cut flat pericardial sheets into exact cusp extension patches, and initial clinical experience indicates that they are useful in performing precise aortic cusp extension procedures and restoring adequate aortic valve competence.

Effect of Cusp Size, Depth and Direction on Stress Concentration

Recently multi-axial machining technology has improved significantly. It has become a widely accepted method of manufacturing components with complex, free form surfaces. Solid billet materials with negligible internal defects are used in this process. This provides increased durability and fatigue life over equivalent cast components. However, multi-axial machining leaves cusps as machining marks. The combination of tool size and step-over generates cusps with different depths and widths. Even though the cusps add extra material on top of the nominal surface, the Finite Element Analysis simulations presented in this paper show that the maximum stress generated within the cusps can be greater than that predicted from the cusp-free geometry. These stress concentrations generated by cusps can reduce the fatigue life and durability of a machined component. In this paper a full factorial analysis of the effect of tool size, cusp width/step-over and cusp direction has been conducted. The analysis uses five different levels of tool size and cusps width and four levels of cusp direction. The results can be used to determine a tool size, cusp width and cusp direction combination with minimum spurious stress raising effect.

Aortic valve replacement using autologous pericardium: single centre experience with the Ozaki technique.

To assess the clinical implementation and report preliminary results of a novel technique called the Ozaki procedure for stentless aortic valve replacement through reconstruction of the valve leaflets from autologous pericardium. Between September 2015 and May 2017 30 patients (20 males, mean ± standard deviation age 66.83 ± 10.55 years) suffering from aortic stenosis (AS, n = 7), aortic regurgitation (AR, n = 12), or a combination of both (AS/AR, n = 11) were assigned for an Ozaki procedure. The glutaraldehyde-treated autologous pericardium was intraoperatively customised and tailored according to individual sinus measurements and appropriate Ozaki templates (CE marked). Mean and peak preoperative transvalvular pressure gradients in patients with AS were 46.34 ± 14.71 and 78.00 ± 22.54 mm Hg, respectively and effective orifice area was 0.93 ± 0.26 cm2. Ejection fraction was preserved at 57.37 ± 10.33%. Twenty-four valves were tricuspid and 6 bicuspid; 13 patients had concomitant cardiac surgery (coronary artery bypass graft, mitral valve repair, replacement of ascending aorta). Mean ± SD cross-clamp time for replacement only was 85.18 ± 18.10 minutes and perfusion time 104.76 ± 38.52 minutes. Cusp sizes were 27.76 ± 3.52 mm for the left coronary cusp (CC), 28.20 ± 3.51 mm for the right CC and 29.20 ± 3.34 mm for non-CC. Mean and peak postoperative gradients decreased to 8 ± 3.55 and 14.8 ± 6.21 mm Hg, respectively. Mean length of stay on the intensive care unit was 2.19 ± 2.34 days and in-hospital stay was 8.81 ± 2.04 days after isolated Ozaki procedures. No pacemaker had to be implanted after an isolated Ozaki procedure. Thirty-day mortality was 3.33% (n = 1). After 3 months, no patient presented with aortic stenosis, and regurgitation of the substituted valves was graded nil/trace in 85.71%, mild in 10.71%, and moderate in 3.57% of the patients. Ejection fraction remained unchanged at 58.89 ± 11.29%. No reoperation was required within the first 3 months. This aortic valve replacement technique has become available only recently. In our experience, it can be mastered after a relatively short training period, and has become part of our routine clinical toolbox. The use of autologous pericardium in combination with excellent haemodynamics may have the potential to overcome the structural disadvantages of biological aortic valves, to be beneficial in infective endocarditis, and to represent an alternative for patients with small annuli.

Precise moulded autologous pericardial configurations for aortic cusp reconstruction.

In order to facilitate surgical repair of complex aortic cusp deformities and restoration of aortic valve competence, new moulds were developed to shape the glutaraldehyde-treated autologous pericardium into precise cusp-like configurations that can be used in aortic cusp reconstruction. The new moulds embodied the natural geometry of single aortic cusps, and a series of moulds were made available to correspond with all potential aortic cusp sizes. Aortic valve reconstruction using moulded autologous pericardial cusps was performed in 2 patients (both males, aged 14 and 19 years) with large outlet-type ventricular septal defects, extensive deformation of prolapsed right coronary cusps and severe aortic valve insufficiency. In each patient, the diseased right aortic cusp was excised and was replaced by a moulded autologous pericardial cusp that equalled the size of adjacent undiseased native cusps. Excellent coaptation with adjoining native aortic cusps could be readily observed and intraoperative transoesophageal echocardiography confirmed satisfactory aortic valve repair (aortic insufficiency <1+ and low-transvalvular gradients). Follow-up transthoracic echocardiography confirmed that aortic valve function remained stable in both patients 2 years postoperatively. Initial clinical experience indicated that constructing geometrically perfect cusp-like configurations was uncomplicated and implantation of the moulded autologous pericardial cusps restored adequate aortic valve competence. We believe that the simplicity and reproducibility of this approach may assist in the dissemination of aortic cusp reconstruction procedures.

New material of the marsupial (Mammalia, Metatheria)Herpetotherium merriami(Stock and Furlong, ) from the John Day Formation, late Oligocene, Oregon, USA

AbstractRecently discovered specimens of the marsupialHerpetotherium merriami(Stock and Furlong, 1922) from the John Day Formation, Oregon, are described. The species was previously known only from a single (type) specimen. These additional specimens have allowed for a revised diagnosis of the species based on the presence of an additional stylar cusp on the upper molars, as well as the relative size of the stylar cusps. This new material also allows for an examination of the variability within the species and establishes a time range for the species, which extends through most of the Arikareean (late Oligocene: Ar1–Ar3: late Rupelian-Aquitanian).Herpetotherium merriamiis distinct within the genus because it is among the larger of the species, but one of the latest occurring, whereas the general pattern of the genus is a reduction in size through time.

Node dynamics and cusps size distribution at the border of liquid sheets

A careful experimental study of the dynamics of nodes and the distribution of the sizes of cusps at the border of liquid sheets is presented.