Crown Group Research Articles

The significance of Anomalocaris and other Radiodonta for understanding paleoecology and evolution during the Cambrian explosion

One of the most widespread and diverse animal groups of the Cambrian Explosion is a clade of stem lineage arthropods known as Radiodonta, which lived exclusively in the early Paleozoic. First reported in 1892 withAnomalocaris canadensis, radiodonts are now one of the best known early animal groups with excellent representation in the fossil record, and are ubiquitous components ofKonservat-Lagerstättenfrom the Cambrian and the Early Ordovician. These large swimmers were characterised by a segmented body bearing laterally-oriented flaps, and a head with a distinct radial oral cone, a pair of large frontal appendages adapted for different feeding modes, compound eyes on stalks, and prominent head carapaces. Radiodonts inform on the paleoecology of early animal communities and the steps involved in euarthropod evolution. Four families within Radiodonta have been established. The raptorial predator families Anomalocarididae and Amplectobeluidae were dominant early in the evolutionary history of Radiodonta, but were later overtaken by the mega-diverse and widespread Hurdiidae, which has a more generalised sediment-sifting predatory mode. Suspension feeding, notably in the families Tamisiocarididae and Hurdiidae, also evolved at least twice in the history of the clade. The well-preserved anatomical features of the radiodont body and head have also provided insights into the evolution of characteristic features of Euarthropoda, such as the biramous limbs, compound eyes, and organisation of the head. With 37 species recovered from all major paleocontinents of the Cambrian and Early Ordovician, Radiodonta provides a unique opportunity for revealing evolutionary patterns during the Cambrian Explosion.

A forged ‘chimera’ including the second specimen of the protostegid sea turtle Santanachelysgaffneyi and shell parts of the pleurodire Araripemys from the Lower Cretaceous Santana Group of Brazil

Fossils of Cretaceous sea turtles adapted to an open marine lifestyle remain rare finds to date. Furthermore, the relationships between extant sea turtles, chelonioids, and other Mesozoic marine turtles are still contested, with one key species being Santanachelysgaffneyi Hirayama, 1998, long considered the earliest true sea turtle. The species is an Early Cretaceous member of Protostegidae, a controversial clade either placed within or closely related to Chelonioidea or, alternatively, along the stem lineage of hidden-neck turtles (Cryptodira) and representing an independent open marine radiation. Santanachelysgaffneyi is one of the most completely preserved early protostegids and is therefore critical for establishing the global phylogenetic position of the group. However, the single known specimen of this taxon is yet to be described in detail. Here we describe a second specimen of Santanachelysgaffneyi from its type horizon, the Romualdo Formation (late Aptian) of the Santana Group of the Araripe basin, NE Brazil. The skeletal elements preserved include the posterior part of the skull, neck vertebrae, shoulder girdle, anterior-most and left/central part of the carapace with few peripherals, and plastron lacking most of the hyoplastra. The remaining part of the carapace was apparently completed by fossil dealers using an anterior part of the pleurodiran Araripemydidae, tentatively identified as a shell portion of cf. Araripemysbarretoi, a more common Santana fossil turtle, among other indeterminate turtle shell fragments. The purpose of this paper is to report the repatriation of the specimen to Brazil and to provide a preliminary description.

Narrow-beaked trogons from the early Eocene London Clay of Walton-on-the-Naze (Essex, UK)

We describe multiple partial skeletons of a new trogon species from the early Eocene London Clay of Walton-on-the-Naze (Essex, UK), which are among the oldest fossils of the Trogoniformes. Eotrogon stenorhynchus, gen. et sp. nov. has a much narrower and more gracile beak than extant trogons, which denotes different ecological attributes of the fossil species. Eotrogon stenorhynchus already had the heterodactyl foot characterising extant trogons, even though the trochlea for the second toe is smaller than in crown group Trogoniformes. Differences to extant trogons in the wing and pectoral girdle elements suggest that E. stenorhynchus was less adapted to short-term hovering, which may indicate different foraging techniques. We also report a partial tarsometatarsus from the early Miocene of France that is likely to belong to Paratrogon gallicus, a species previously only known from humeri. P. gallicus is the earliest modern-type trogon, and we show that the newly identified tarsometatarsus does not support the proposed referral of this species to the African taxon Apaloderma. We identify skeletal features that suggest a sister group relationship between Apaloderma and all other crown group Trogoniformes, but the exact affinities of Paratrogon remain poorly resolved. (http://zoobank.org/urn:lsid:zoobank.org:pub:73B64B84-11C2-4D50-8540-099CF86B6CA1).

Heavy metal-laden particulate dust disrupts intestinal epithelial stem cells and lineage differentiation

Chronic heavy metals exposure has been associated with intestinal inflammation and higher incidences of colorectal cancer, however there is no molecular evidence that metal laden-particulates can cause injury to the gut epithelia. Communities that live adjacent to abandoned uranium mines have higher incidence of metabolic and digestive diseases; however, the cause is unknown. The goal of this study is to characterize particulate dust containing non-fissile uranium as an environmental toxicant that damages intestinal epithelia and characterize the subsequent transcriptomic changes. We hypothesized that non-fissile uranium will alter the differentiation pattern of progenitor cells in the crypt biasing them towards the secretory lineage. Human colonoids derived from healthy adult colonic biopsies (UNM IRB approved study 18-626 and 18-171) were established and shown to physiologically model the intestinal epithelia. Colonoids were acutely exposed (24h) to non-fissile uranium dust obtained near the Jackpile uranium mine in New Mexico, one of the largest open pit uranium mines in the US, located on the Laguna Pueblo. Control and dust-exposed colonoids (n=3 unique donors) were dissociated into single cells and processed for droplet-based single cell sequencing (scRNAseq). scRNAseq identified significant changes in the secretory lineage in uranium dust-exposed colonoids. Specifically, there was a four-fold expansion of enteroendocrine cells (EEC) with increases in EEC hormones serotonin and PYY in all colonoid lines. Proliferative pathways, such as Wnt signaling and negative regulation of apoptosis were upregulated in these EECs. These transcriptomic changes in EECs and proliferative cells and increased basolateral secretion of secretory granules and serotonin was validated in colonoids (˃5 biologically unique human donors) via RNA FISH, immunofluorescence and ELISAs. Our results demonstrate that acute uranium dust exposure directly induces transcriptomic and cellular changes in intestinal epithelia independently of microbiota, stroma, and immune cells. These results indicate that adult human colonoids are a relevant model for investigating environmental toxicants on intestinal epithelia and provide an improved understanding of uranium dust as a model of intestinal injury. This study was funded by NIDDK (K01DK106323), NIEHS (R56ES034400, P42ES025589), and NIGMS (P20GM121176, P20GM130422). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Endocranial anatomy of the early prozostrodonts (Eucynodontia: Probainognathia) and the neurosensory evolution in mammal forerunners.

Prozostrodon brasiliensis and Therioherpeton cargnini are non-mammaliaform cynodonts that lived ~233 million years ago (late Carnian, Late Triassic) in western Gondwana. They represent some of the earliest divergent members of the clade Prozostrodontia, which includes "tritheledontids", tritylodontids, "brasilodontids", and mammaliaforms (including Mammalia as crown group). Here, we studied the endocranial anatomy (cranial endocast, nerves, vessels, ducts, ear region, and nasal cavity) of these two species. Our findings suggest that during the Carnian, early prozostrodonts had a brain with well-developed olfactory bulbs, expanded cerebral hemispheres divided by the interhemispheric sulcus, and absence of an unossified zone and pineal body. The morphology of the maxillary canal represents the necessary condition for the presence of facial vibrissae. A slight decrease in encephalization is observed at the origin of the clade Prozostrodontia. This new anatomical information provides evidence for the evolution of endocranial traits of the first prozotrodonts, a Late Triassic lineage that culminated in the origin of mammals.

Plastid phylogenomics and molecular evolution of Thismiaceae (Dioscoreales).

Species in Thismiaceae can no longer photosynthesize, and instead obtain carbon from soil fungi. Here we infer Thismiaceae phylogeny using plastid genome data, and also characterize the molecular evolution of this genome. We assembled five Thismiaceae plastid genomes from genome skimming data, adding to previously published data for phylogenomic inference. We investigated plastid-genome structural changes, considering locally colinear blocks (LCBs). We also characterized possible shifts in selection pressure in retained genes by considering changes in ω, the ratio of non-synonymous to synonymous changes. Thismiaceae experienced two major pulses of gene loss around the early diversification of the family, with subsequent scattered gene losses across descendent lineages. In addition to massive size reduction, Thismiaceae plastid genomes experienced occasional inversions, and there likely were two independent losses of the plastid inverted repeat (IR) region. Retained plastid genes remain under generally strong purifying selection (ω << 1), with significant and sporadic weakening or strengthening in several instances. The bifunctional trnE-UUC gene of Thismia huangii likely retains a secondary role in heme biosynthesis, despite a probable loss of functionality in protein translation. Several cis-spliced group IIA introns are retained, despite the loss of the plastid intron maturase, matK. We infer that most gene losses in Thismiaceae occurred early and rapidly, following the initial loss of photosynthesis in its stem lineage. As a species-rich, fully mycoheterotrophic lineage, Thismiaceae provides a model system for uncovering the unique and divergent ways in which plastid genomes evolve in heterotrophic plants. This article is protected by copyright. All rights reserved.

PREVENTION AND TREATMENT OF CARIES AND ITS COMPLICATIONS IN TEMPORARY TEETH IN A DENTAL CLINIC

Damage to the hard tissues of the teeth is most common among children. This applies to both temporary and permanent bite. Untimely prevention and treatment of caries leads to the progression of the process in the tissues of the tooth, the occurrence of complications.&#x0D; The aim of the study was to explore the possibility of using various methods of treatment and prevention of caries in deciduous teeth and its complications in children in a dental clinic.&#x0D; For the period from 2020 to 2023, 1659 patients aged 2-6 years old applied to the dental clinic. Each patient was examined, individual training was given to them and their parents in oral hygiene, a treatment plan was drawn up and preventive measures were taken. Recommendations were given on rational nutrition. Sealing was applied in temporary molars within a year after their eruption. After 2 years, 90% of patients did not reveal caries of temporary molars.&#x0D; In children of this age group, the treatment of diseases of the teeth’ hard tissues can be carried out using local anesthesia, under nitrous-nitrogen-oxygen sedation and under general anesthesia. The choice of treatment method will be influenced by the total amount of sanitation and the compliance of the child. In 72% of patients, the intervention was performed under general anesthesia. The use of this method in the clinic makes it possible to treat a certain number of teeth in one visit and work with a cohort of children who are not ready for the usual conditions of admission.&#x0D; The most common pathology treated was caries, accounting for 89% of the children who visited the clinic.&#x0D; Used photopolymer composite filling materials.&#x0D; A complication of caries (inflammation of the pulp or periodontal tissues) was treated in 64% of patients who sought dental care. Each patient underwent an X-ray examination, an orthopantomogram, or targeted images, depending on the age of the child, to decide on the choice of treatment method (tooth preservation or extraction). So, 5.4% of the teeth that needed intervention by a pediatric dentist were subject to extraction. Complicated caries is accompanied by significant destruction of the tooth crown, which requires appropriate treatment approaches. In such cases, standard crowns were more often used, which made it possible to restore the anatomical shape of temporary molars, their function and achieve a long-term treatment effect until the period of physiological changes in the teeth.&#x0D; There are several options for crowns that can be used in pediatric dentistry standard steel crowns (stainless steel crowns), for the restoration of the chewing group of teeth, metal crowns with plastic veneer, for the restoration of the anterior group of teeth and crowns based on a framework of zirconium dioxide, which are universal and biocompatible with periodontal tissues.&#x0D; Admission of children to the dental clinic allows the use of modern methods of diagnosis, anesthesia, treatment, and preventive measures. An important point is the cooperation of a pediatric dentist with the patient's parents, which is the key to obtaining maximum positive results, restore chewing function, aesthetic appearance, achieve an increase in the resistance of hard dental tissues and prevent caries and its further development.

Validation of the Implant Stability Test for Implant Provisional Crowns: An In Vitro Study

Implant treatment has evolved and is now performed using various techniques. However, the osseointegration duration required for poor primary stability or immediate loading is unclear and depends largely on the surgeon’s experience. We sought to verify whether implant stability can be quantified after immediate loading, using AnyCheck®. Six implants were placed in simulated bone blocks classified by bone quality as D1–D4 and further divided into healing abutment and provisional crown groups. The implant stability test (IST) values of both groups were measured using AnyCheck®. All bone qualities from D1 to D4 differed significantly between the provisional crown and healing abutment groups (p &lt; 0.001). In both groups, the IST values were the highest for D1 bone and lowest for D4 bone. There were significant differences in bone quality between the provisional crown and healing abutment groups. The correlations between the groups differed based on bone quality. However, the IST values of both groups differed by a minimum of 4 and maximum of 7. These results suggest that AnyCheck® is useful for quantifying the implant stability after immediate loading. Using an index to quantify the implant and bone stability for immediate loading may shorten treatment duration and increase success rates.

Cranial and mandibular anatomy of Plastomenus thomasii and a new time-tree of trionychid evolution

Trionychid (softshell) turtles have a peculiar bauplan, which includes shell reductions and cranial elongation. Despite a rich fossil record dating back to the Early Cretaceous, the evolutionary origin of the trionychid bauplan is poorly understood, as even old fossils show great anatomical similarities to extant species. Documenting structural detail of fossil trionychids may help resolve the evolutionary history of the group. Here, we study the cranial and mandibular anatomy of Plastomenus thomasii using µCT scanning. Plastomenus thomasii belongs to the Plastomenidae, a long-lived (Santonian–Eocene) clade with uncertain affinities among trionychid subclades. The skulls of known plastomenids are characterized by unusual features otherwise not known among trionychids, such as extremely elongated, spatulate mandibular symphyses. We use anatomical observations for updated phylogenetic analyses using both parsimony and Bayesian methods. There is strong support across methods for stem-cyclanorbine affinities for plastomenids. The inclusion of stratigraphic data in our Bayesian analysis indicates that a range of Cretaceous Asian fossils including Perochelys lamadongensis may be stem-trionychids, suggesting that many features of trionychid anatomy evolved prior to the appearance of the crown group. Divergence time estimates from Bayesian tip-dating for the origin of crown Trionychia (134.0 Ma) and Pan-Trionychidae (123.8 Ma) constrain the evolutionary time span during which the trionychid bauplan has evolved to a range of < 11 million years. Bayesian rate estimation implies high morphological rates during early softshell turtle evolution. If correct, plastomenids partially fill the stratigraphic gap which results from shallow divergence times of crown cyclanorbines during the late Eocene.

The phylogeny and evolutionary ecology of hoverflies (Diptera: Syrphidae) inferred from mitochondrial genomes

Hoverflies (Diptera: Syrphidae) are a diverse group of pollinators and a major research focus in ecology, but their phylogenetic relationships remain incompletely known. Using a genome skimming approach we generated mitochondrial genomes for 91 species, capturing a wide taxonomic diversity of the family. To reduce the required amount of input DNA and overall cost of the library construction, sequencing and assembly was conducted on mixtures of specimens, which raises the problem of chimera formation of mitogenomes. We present a novel chimera detection test based on gene tree incongruence, but identified only a single mitogenome of chimeric origin. Together with existing data for a final set of 127 taxa, phylogenetic analysis on nucleotide and amino acid sequences using Maximum Likelihood and Bayesian Inference revealed a basal split of Microdontinae from all other syrphids. The remainder consists of several deep clades assigned to the subfamily Eristalinae in the current classification, including a clade comprising the subfamily Syrphinae (plus Pipizinae). These findings call for a re-definition of subfamilies, but basal nodes had insufficient support to fully justify such action. Molecular-clock dating placed the origin of the Syrphidae crown group in the mid-Cretaceous while the Eristalinae-Syrphinae clade likely originated near the K/Pg boundary. Transformation of larval life history characters on the tree suggests that Syrphidae initially had sap feeding larvae, which diversified greatly in diet and habitat association during the Eocene and Oligocene, coinciding with the diversification of angiosperms and the evolution of various insect groups used as larval host, prey, or mimicry models. Mitogenomes proved to be a powerful phylogenetic marker for studies of Syrphidae at subfamily and tribe levels, allowing dense taxon sampling that provided insight into the great ecological diversity and rapid evolution of larval life history traits of the hoverflies.

Is it inappropriate to ask for your age? Evaluating parameter impact on tree dating in a challenging clade (Macroscelidea)

Sengis (order Macroscelidea) are small mammals endemic to Africa. The taxonomy and phylogeny of sengis has been difficult to resolve due to a lack of clear morphological apomorphies. Molecular phylogenies have already significantly revised sengi systematics, but until now no molecular phylogeny has included all 20 extant species. In addition, the age of origin of the sengi crown clade and the divergence age of its two extant families remain unclear. Two recently published studies based on different datasets and age-calibration parameters (DNA type, outgroup selection, fossil calibration points) proposed highly different divergent age estimates and evolutionary scenarios. We obtained nuclear and mitochondrial DNA from mainly museum specimens using target enrichment of single-stranded DNA libraries to generate the first phylogeny of all extant macroscelidean species. We then explored the effects of different parameters (type of DNA, ratio of ingroup to outgroup sampling, number and type of fossil calibration points) and their resulting impacts on age estimates for the origin and initial diversification of Macroscelidea. We show that, even after correcting for substitution saturation, both using mitochondrial DNA in conjunction with nuclear DNA or alone results in much older ages and different branch lengths than when using nuclear DNA alone. We further show that the former effect can be attributed to insufficient amounts of nuclear data. If multiple calibration points are included, the age of the sengi crown group fossil prior has minimal impact on the estimated time frame of sengi evolution. In contrast, the inclusion or exclusion of outgroup fossil priors has a major effect on the resulting node ages. We also find that a reduced sampling of ingroup species does not significantly affect overall age estimates and that terminal specific substitution rates can serve as a means to evaluate the biological likeliness of the produced temporal estimates. Our study demonstrates how commonly varied parameters in temporal calibration of phylogenies affect age estimates. Dated phylogenies should therefore always be seen in the context of the dataset which was used to produce them.

A phylogenomic approach to resolving interrelationships of polyclad flatworms, with implications for life-history evolution.

Platyhelminthes (flatworms) are a diverse invertebrate phylum useful for exploring life-history evolution. Within Platyhelminthes, only two clades develop through a larval stage: free-living polyclads and parasitic neodermatans. Neodermatan larvae are considered evolutionarily derived, whereas polyclad larvae are hypothesized to be ancestral due to ciliary band similarities among polyclad and other spiralian larvae. However, larval evolution has been challenging to investigate within polyclads due to low support for deeper phylogenetic relationships. To investigate polyclad life-history evolution, we generated transcriptomic data for 21 species of polyclads to build a well-supported phylogeny for the group. The resulting tree provides strong support for deeper nodes, and we recover a new monophyletic clade of early branching cotyleans. We then used ancestral state reconstructions to investigate ancestral modes of development within Polycladida and more broadly within flatworms. In polyclads, we were unable to reconstruct the ancestral state of deeper nodes with significant support because early branching clades show diverse modes of development. This suggests a complex history of larval evolution in polyclads that likely includes multiple losses and/or multiple gains. However, our ancestral state reconstruction across a previously published platyhelminth phylogeny supports a direct developing prorhynchid/polyclad ancestor, which suggests that a larval stage in the life cycle evolved along the polyclad stem lineage or within polyclads.

The second species of Sorellevania Engel, 2006 (Evanioidea: Evaniidae) from the mid-Cretaceous Burmese amber

The representatives of the superfamily Evanioidea are easily distinguishable from all other extant and extinct Hymenoptera because of their metasoma (sometimes rounded) articulated high on the propodeum and well above the metacoxae (e.g., Goulet &amp; Huber, 1993). Recent phylogenetic studies on the superfamily Evanioidea have shown strong support for its monophyly and for the monophyly of the Evaniidae even when fossil taxa are included (e.g., Li et al., 2018; Parslow et al., 2020; Jouault et al., 2022). According to the most recent analysis, the superfamily arose during either the Upper Triassic or the Lower Jurassic. Still, its earliest species are recorded in the younger Middle Jurassic, and its crown-group representatives during the Lower Cretaceous (Jouault et al., 2022: fig. 8). The stem Evaniidae are estimated to arise during the Upper Jurassic while their crown group has a more recent origin, likely around the Cretaceous-Paleogene boundary. Extant evaniid wasps are common, nearly cosmopolitan, and moderately diversified (about 580 extant species in 21 genera) even if this diversity is underestimated (Deans, 2005; Mullins et al., 2012). Little is known about the biology of extant evaniids, but their larvae are considered predators of cockroach eggs in oothecae (Huben, 1995). The Evaniidae have a good fossil record with the oldest species known from the late Hauterivian, numerous species documented up to the Miocene, and an important diversity in Burmese amber (e.g., Rasnitsyn et al., 1998; Nel et al., 2002; Deans et al., 2004; Jennings et al., 2012; Shih et al., 2020). Nevertheless, their past diversity is still underestimated.

A new large tortoise from the early Oligocene (Arikareean NALMA) of Oaxaca, southern Mexico and its phylogenetic position within Pan-Testudinidae

ABSTRACT Pan-Testudinidae is the total clade of extant terrestrial tortoises, which includes extinct fossil members of their stem lineage. Members of this clade have a rather scarce fossil record in Mexico, and the few specimens known in scientific collections are poorly studied. Here, we described a new species of basal testudinid turtle, based on a single specimen from the early Oligocene deposits exposed in the marginal facies of the Chilapa Formation in Oaxaca, southern Mexico. The new taxon exhibits osteological characteristics that support its insertion as a basal Testudinidae. The phylogenetic relationships of the new turtle were assessed using a total evidence approach (morphological + molecular) in a global Pan-Testudinidae context using Implied Weighted Maximum Parsimony (IWMP), Standard Maximum Parsimony (SMP) and Bayesian Inference (BI). Although the BI consensus tree is not well resolved, the results obtained by IWMP and SMP retrieved its branching close to the root of Testudinidae. The differences between the topologies of the three phylogenetic analyses show that the position of several taxa within Testudinidae is affected by the phylogenetic analyses performed. The new taxon from Oaxaca, here reported, represents the first Palaeogene and the southernmost tortoise described from Mexico and the oldest Testudinidae known in the country.

Systematics and Phylogenetic Interrelationships of the Enigmatic Late Jurassic Shark Protospinax annectans Woodward, 1918 with Comments on the Shark-Ray Sister Group Relationship.

The Late Jurassic elasmobranch Protospinax annectans is often regarded as a key species to our understanding of crown group elasmobranch interrelationships and the evolutionary history of this group. However, since its first description more than 100 years ago, its phylogenetic position within the Elasmobranchii (sharks and rays) has proven controversial, and a closer relationship between Protospinax and each of the posited superorders (Batomorphii, Squalomorphii, and Galeomorphii) has been proposed over the time. Here we revise this controversial taxon based on new holomorphic specimens from the Late Jurassic Konservat-Lagerstätte of the Solnhofen Archipelago in Bavaria (Germany) and review its skeletal morphology, systematics, and phylogenetic interrelationships. A data matrix with 224 morphological characters was compiled and analyzed under a molecular backbone constraint. Our results indicate a close relationship between Protospinax, angel sharks (Squatiniformes), and saw sharks (Pristiophoriformes). However, the revision of our morphological data matrix within a molecular framework highlights the lack of morphological characters defining certain groups, especially sharks of the order Squaliformes, hampering the phylogenetic resolution of Protospinax annectans with certainty. Furthermore, the monophyly of modern sharks retrieved by molecular studies is only weakly supported by morphological data, stressing the need for more characters to align morphological and molecular studies in the future.

A new red alga preserved with possible reproductive bodies from the 518‐million‐year‐old Qingjiang biota

AbstractMacroalgae have been a key ecological component of marine ecosystems since the Proterozoic period and are common fossil forms in Cambrian Burgess Shale‐type Lagerstätten. However, in most cases, it is difficult to place these early fossil algae into modern groups because little distinctive morphology is preserved. Here, we describe a new form of macroalgae, Qingjiangthallus cystocarpium gen. &amp; sp. nov., from the Qingjiang biota of South China. The new taxon is represented by 546 specimens remarkably preserved with characteristics that allow a phylogenetic placement into crown groups of red algae. Centimeter‐sized thalli resemble members of the extant Rhodymeniophycidae (a subclass of the class Florideophyceae), and hence suggest a florideophycean affinity, which indicates that ahnfeltiophycidaen and rhodymeniophycidaen algae may have diverged at least 518 Ma, accordant with estimations of molecular studies. The presence of possible cystocarps on Qingjiangthallus thalli suggests that evolutionary innovation of a triphasic life cycle in red algae may have occurred no later than the Early Cambrian. The branching patterns and branch width of Qingjiangthallus are consistent with the coarsely dichotomously branched morphogroup, which was previously present in the Ediacaran, Ordovician, and afterward, but absent in the Cambrian.

The Cambrian cirratuliform Iotuba denotes an early annelid radiation.

The principal animal lineages (phyla) diverged in the Cambrian, but most diversity at lower taxonomic ranks arose more gradually over the subsequent 500 Myr. Annelid worms seem to exemplify this pattern, based on molecular analyses and the fossil record: Cambrian Burgess Shale-type deposits host a single, early-diverging crown-group annelid alongside a morphologically and taxonomically conservative stem group; the polychaete sub-classes diverge in the Ordovician; and many orders and families are first documented in Carboniferous Lagerstätten. Fifteen new fossils of the 'phoronid' Iotuba (=Eophoronis) chengjiangensis from the early Cambrian Chengjiang Lagerstätte challenge this picture. A chaetal cephalic cage surrounds a retractile head with branchial plates, affiliating Iotuba with the derived polychaete families 'Flabelligeridae' and Acrocirridae. Unless this similarity represents profound convergent evolution, this relationship would pull back the origin of the nested crown groups of Cirratuliformia, Sedentaria and Pleistoannelida by tens of millions of years-indicating a dramatic unseen origin of modern annelid diversity in the heat of the Cambrian 'explosion'.

Does the presence of full-coverage crown interfere with removal of obturation material: A cone-beam computed tomography image segmentation volumetric analysis.

The aim of this study was to assess and compare the influence of the presence of full-coverage crown on the obturation material removal efficiency of different retreatment file systems. Sixty extracted, human, maxillary premolars were accessed, instrumented, and obturated with gutta-percha and AH Plus sealer. The samples were scanned with cone-beam computed tomography and volume of obturating material was measured using ITK-SNAP volumetric software. Samples were divided (n = 30) into with and without all metal full-coverage crown groups. Each group was then subdivided into three subgroups (n = 10) based on retreatment file used (ProTaper URS, HyFlex Remover, and NeoEndo). The volume of remnants of obturating material was remeasured by image segmentation using ITK-SNAP volumetric software. One-way analysis of variance, followed by the Tukey's post hoc test, was used for data analysis, with a significance level of 5%. A significant difference in percentage remnant of obturating material after retreatment file was observed on overall comparison between with (29.84%) and without crown (21.79%) groups (P < 0.05). Each file system removed significantly more obturating material in without crown samples than with crown samples (P < 0.05). The percentage remnant of obturating material after retreatment file use was as follows: ProTaper URS > NeoEndo retreatment file > HyFlex Remover. All file systems showed significantly different (P < 0.05) efficiency in removal of obturating material. None of the retreatment file systems were able to remove obturating material completely. The presence of full-coverage crown negatively impacted the efficiency of retreatment files for the removal of obturating material. HyFlex Remover performed better than NeoEndo which was better than ProTaper URS.

Clinical peri-implant outcomes, technical complications, and patient satisfaction with single vs. splinted crown supported implants in the anterior mandible region of diabetic individuals.

To compare the clinical and radiographic peri-implant parameters around narrow diameter implants (NDI) supported single (NDISCs) and splinted crowns (NDISPs) in the anterior maxilla of non-diabetics and type 2 diabetes mellitus patients (T2DM). The clinical and radiographic parameters of NDISC and NDISP were assessed in the anterior mandibular jaw of T2DM and non-diabetic individuals. Plaque index (PI), bleeding on probing (BoP), probing depth (PD) and crestal bone levels were recorded. Technical complications and patient satisfaction were also assessed. ANOVA (one-way analysis of variance) was used to compare the inter-group means of clinical indices and radiographic bone loss while Shapiro-Wilk was used to compute the normal distribution of dependent variables. A p-value of less than 0.05 was considered significant. Sixty-three patients (35 males and 28 females) were part of the study out of which 32 were non-diabetics and 31 were T2DM patients. A total of 188 implants (124 NDISCs and 64 NDISPs) having moderately roughened topography were used for the study. The mean glycated hemoglobin in the non-diabetic group was 4.3 while that in the T2DM group was 7.9 with an average diabetic history of 8.6 years. Peri-implant parameters, including PI, BoP, and PD, were comparable between the single crown and splinted crown groups. However, there was a statistically significant difference in PI, BoP, and PD when a comparison was made between the non-diabetes and T2DM groups (p<0.05). An overall 88% of the patients were satisfied with the esthetics of the crowns while 75% of the subjects were satisfied with the function of the crowns. Narrow diameter implants of both types had satisfactory clinical and radiographic outcomes within non-diabetic and diabetic individuals. However, clinical and radiographic parameters were worse in type 2 diabetes mellitus patients when compared to non-diabetics.

Comparison between Restorative Materials for Pulpotomised Deciduous Molars: A Randomized Clinical Study.

To evaluate and compare the clinical outcomes of Cention-N (CN) and stainless steel crowns (SSCs) as restorations for pulpotomised primary molars, and to study clinical and radiographic outcomes of pulpotomies restored with these materials. The study was conducted on 60 pulpotomised molars with occlusoproximal caries. These were randomly divided into two groups and restored with either stainless steel crowns or Cention-N. Clinical performance of restorations and clinical and radiographic success of pulpotomy was examined at 6, 9 and 12 months. The mean scores for marginal integrity deteriorated significantly at 6, 9 and 12 months in both groups but in comparison were insignificant. The mean for proximal contact deteriorated significantly for the Cention-N group, whereas the mean for gingival health deteriorated remarkably for the stainless steel crown group at successive evaluations. No tooth in either group showed secondary caries or discomfort on biting, except for one tooth in Cention-N group which presented with secondary caries. The clinical success rate for pulpotomised molars was 100% for both groups until nine months, although this had reduced by the end of 12 months. Radiographically, the success rate was 79.3% for Cention-N, while it was 86.6% for stainless steel crowns at 12 months. There was no significant difference in clinical and radiographic success between either group. Cention-N and stainless steel crowns are comparable for marginal integrity. However, crowns maintain significantly better proximal contacts while Cention-N was notably better for gingival health of the restored tooth. Both materials do not show secondary caries and discomfort on biting and are comparable in clinical and radiographic success of pulpotomy at the end of one year.