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At least 469 records · Page 26Linked to original sources
PubMed2004

A genomic timescale of prokaryote evolution: insights into the origin of methanogenesis, phototrophy, and the colonization of land.

BACKGROUND: The timescale of prokaryote evolution has been difficult to reconstruct because of a limited fossil record and complexities associated with molecular clocks and deep divergences. However, the relatively large number of genome sequences currently available has provided a better opportunity to control for potential biases such as horizontal gene transfer and rate differences among lineages. We assembled a data set of sequences from 32 proteins (approximately 7600 amino acids) common to 72 species and estimated phylogenetic relationships and divergence times with a local clock method. RESULTS: Our phylogenetic results support most of the currently recognized higher-level groupings of prokaryotes. Of particular interest is a well-supported group of three major lineages of eubacteria (Actinobacteria, Deinococcus, and Cyanobacteria) that we call Terrabacteria and associate with an early colonization of land. Divergence time estimates for the major groups of eubacteria are between 2.5-3.2 billion years ago (Ga) while those for archaebacteria are mostly between 3.1-4.1 Ga. The time estimates suggest a Hadean origin of life (prior to 4.1 Ga), an early origin of methanogenesis (3.8-4.1 Ga), an origin of anaerobic methanotrophy after 3.1 Ga, an origin of phototrophy prior to 3.2 Ga, an early colonization of land 2.8-3.1 Ga, and an origin of aerobic methanotrophy 2.5-2.8 Ga. CONCLUSIONS: Our early time estimates for methanogenesis support the consideration of methane, in addition to carbon dioxide, as a greenhouse gas responsible for the early warming of the Earths' surface. Our divergence times for the origin of anaerobic methanotrophy are compatible with highly depleted carbon isotopic values found in rocks dated 2.8-2.6 Ga. An early origin of phototrophy is consistent with the earliest bacterial mats and structures identified as stromatolites, but a 2.6 Ga origin of cyanobacteria suggests that those Archean structures, if biologically produced, were made by anoxygenic photosynthesizers. The resistance to desiccation of Terrabacteria and their elaboration of photoprotective compounds suggests that the common ancestor of this group inhabited land. If true, then oxygenic photosynthesis may owe its origin to terrestrial adaptations.

Bacteria↗
PubMed2024

Delayed diagnosis of mild mucopolysaccharidosis type IVA.

BACKGROUND: Mucopolysaccharidosis IVA (MPS IVA) is a lysosomal storage disease caused by biallelic variants in the N-acetylgalactosamine-6-sulfatase (GALNS) gene and is characterized by progressive and multi-system involvements, dominantly with skeletal deformities. A mild form of MPS IVA often presents with atypical symptoms and can go unrecognized for years. METHODS: The diagnosis of MPS IVA was confirmed via GALNS enzyme activity testing in leukocytes. Clinical features were collected. Molecular analysis was performed by next generation sequence and Sanger sequencing of the GALNS gene. The pathogenicity of the deep intron variant was verified by mRNA analyses. RESULTS: Thirteen patients with mild MPS IVA from six families were included. All probands first visit pediatric orthopedists and it took 5.6 years to be diagnosed after the disease onset. The most common symptoms in our series were waddling gait (85%), short neck (69%) and flat feet (62%). Radiologic findings indicated skeletal abnormalities in all patients, especially modification of the vertebral bodies (100%) and acetabular and femoral head dysplasia (100%). Five novel GALNS variants, including c.121-2_121-1insTTTGCTGGCATATGCA, E2 deletion, c.569 A > G, c.898 + 2 T > A, and c.1139 + 2 T > C, were identified. The most common variant, a deep intron variant NM_000512.5: c.121-210 C > T (NM_001323544.2: c.129 C > T, p.G43G), was revealed to result in an 11 bp deletion (c.128_138delGCGATGCTGAG, p.Gly43Aspfs*5) on GALNS mRNA in the GALNS transcript of NM_001323544.2. CONCLUSIONS: This study provides significant insights into the clinical features and molecular characteristics that contribute to the early diagnosis of mild MPS IVA. On the basis of our cohort, orthopedists need to be able to recognize signs and symptoms of mild MPS IVA as well as the molecular and biochemical diagnosis so that an early diagnosis and treatment can be instituted.

Humans↗
PubMed1996

Phylogenetic diversity of intra-amoebal legionellae as revealed by 16S rRNA gene sequence comparison.

Following a recent phylogenetic analysis of all 39 species of the genus Legionella and related organisms, the name Legionella lytica has been proposed for bacteria previously considered either as Sarcobium lyticum or as 'Legionella-like amoebal pathogens' (LLAPs). To investigate the phylogenetic integrity of this newly proposed species, we determined the 16S rRNA gene sequences of 10 LLAPs isolated from various environmental sources. All 10 isolates clustered within a monophyletic group containing all other members of the genus Legionella. Eight of the 10 isolates formed a monophyletic subgroup within the genus which also included the two previously characterized L. lytica strains. Four of these 10 isolates shared a specific and very close relationship with the L. lytica type strain (> 99% sequence similarity). However, although clearly legionellae, the remaining two LLAP strains bore no specific evolutionary relationship to either L. lytica or any other Legionella species (< 96% sequence similarity). Both isolates lay on their own relatively deep-rooted branches within the radiation of the Legionella cluster. LLAPs do not, therefore, represent a unique species or even a single line of descent within the genus, and investigation of more isolates may reveal them to be as evolutionarily diverse as the other presently recognized Legionella species.

Acanthamoeba↗
PubMed2003

Isolation of extremophiles with the detection and retrieval of Shewanella strains in deep-sea sediments from the west Pacific.

Tests to detect the presence of piezophilic Shewanella strains in the deep-sea sediments of the west, mid- and east Pacific at different depths were done by amplification of previously identified pressure-regulated operons (ORF1,2 and ORF3). The operon fragments were detected in all the deep-sea sediment samples, indicating the broad presence of piezophilic deep-sea Shewanella species or related species in the deep-sea sediments across the Pacific. Extremophiles were isolated from the deep-sea sediment of the west Pacific under atmospheric pressure. Two psychrophilic/psychrotrophic strains, WP2 and WP3, were assigned to the Shewanella genus as determined by their 16S rDNA sequences. WP2 and WP3 were both capable of amplifying pressure-regulated operons; the sequences of the pressure-regulated operons of WP2 and WP3 share high identity between each other, but have more differences from those of S. benthica and S. violacea. The major fatty acids of WP2 and WP3 are 3OH-i-13:0, 14:0, i-15:0, 16:0, 16:1, 18:1, and 20:5. Combined phenotypic analysis, 16S rDNA sequences, and DNA-DNA hybridization results suggest that WP2 and WP3 are two new deep-sea Shewanella species.

Amino Acid Sequence↗
PubMed2005

Novel hydrolase diversity retrieved from a metagenome library of bovine rumen microflora.

A metagenome expression library of bulk DNA extracted from the rumen content of a dairy cow was established in a phage lambda vector and activity-based screening employed to explore the functional diversity of the microbial flora. Twenty-two clones specifying distinct hydrolytic activities (12 esterases, nine endo-beta-1,4-glucanases and one cyclodextrinase) were identified in the library and characterized. Sequence analysis of the retrieved enzymes revealed that eight (36%) were entirely new and formed deep-branched phylogenetic lineages with no close relatives among known ester- and glycosyl-hydrolases. Bioinformatic analyses of the hydrolase gene sequences, and the sequences and contexts of neighbouring genes, suggested tentative phylogenetic assignments of the rumen organisms producing the retrieved enzymes. The phylogenetic novelty of the hydrolases suggests that some of them may have potential for new applications in biocatalysis.

Animals↗
PubMed2004

The complete sequence and gene organization of the mitochondrial genome of the gadilid scaphopod Siphonondentalium lobatum (Mollusca).

Comparisons of mitochondrial gene sequences and gene arrangements can be informative for reconstructing high-level phylogenetic relationships. We determined the complete sequence of the mitochondrial genome of Siphonodentalium lobatum, (Mollusca, Scaphopoda). With only 13,932 bases, it is the shortest molluscan mitochondrial genome reported so far. The genome contains the usual 13 protein-coding genes, two rRNA and 22 tRNA genes. The ATPase subunit 8 gene is exceptionally short. Several transfer RNAs show truncated TpsiC arms or DHU arms. The gene arrangement of S. lobatum is markedly different from all other known molluscan mitochondrial genomes and shows low similarity even to an unpublished gene order of a dentaliid scaphopod. Phylogenetic analyses of all available complete molluscan mitochondrial genomes based on amino acid sequences of 11 protein-coding genes yield trees with low support for the basal branches. None of the traditionally accepted molluscan taxa and phylogenies are recovered in all analyses, except for the euthyneuran Gastropoda. S. lobatum appears as the sister taxon to two of the three bivalve species. We conclude that the deep molluscan phylogeny is probably beyond the resolution of mitochondrial protein sequences. Moreover, assessing the phylogenetic signal in gene order data requires a much larger taxon sample than is currently available, given the exceptional diversity of this character set in the Mollusca.

Amino Acid Sequence↗
PubMed2000

Reference values of indices of spontaneous baroreceptor reflex sensitivity.

Spontaneous baroreceptor reflex sensitivity (BRS) is a well established method for determining baroreflex function, which can be used to assess the potential impact on survival after myocardial infarction, to detect autonomic dysfunction in diabetic patients and in human essential hypertension. The assessment of impaired spontaneous baroreflex function in individual patients contains important clinical information, but age-dependent reference values are still lacking. In the present study we evaluated spontaneous BRS in healthy human controls to determine reference values as a function of age. Two hundred and sixty-two healthy volunteers divided into six age groups (I: <20 years, f = 11, m = 9, II: 20-29 years, f = 42, m = 37, III: 30-39 years, f = 23, m = 37, IV: 40-49 years, f = 27, m = 22, V: 50-59 years, f = 19, m = 17, VI: 60-69 years, f = 5, m = 13). Electrocardiograms (ECG) and finger arterial BP were measured with each subject in the supine position (sup, 7 min) and during deep breathing (dB, 6/min, 15 cycles). BRS was assessed using the sequence technique and the alpha coefficients as obtained from a power spectrum density estimate. Due to the normal logarithmic distribution of the BRS, the limits for impaired baroreflex function at rest were defined from logarithmic data. The limits for the BRS at rest (P = .025) were calculated as (-0.0283 x age) + 2.5198 for the sequence technique. We did not find significant differences in BRS among the female and male healthy volunteers. Our analysis of the six age groups showed the expected significant decrease in BRS, which was most prominent at the transition from group III (<40 years) to group IV (<50 years). BRS at rest and during deep breathing as well as sequential and spectral BRS indices did differ significantly. The results underline the necessity of reference values to evaluate impaired baroreflex function in individual patients.

Adolescent↗
PubMed2025

Genome-wide phylogeny reshapes our understanding of the evolution of deep-sea dragonfishes, bristlemouths, viperfishes, and allies (Stomiiformes).

BACKGROUND: The evolutionary relationships within Stomiiformes, a diverse order of deep-sea fishes dominating the mesopelagic and bathypelagic zones, remain contentious due to conflicting morphological and molecular evidence. These fishes, comprising 464 species across four traditionally recognized families (Gonostomatidae, Sternoptychidae, Phosichthyidae, and Stomiidae), exhibit remarkable adaptations such as bioluminescence, ultra-black pigmentation, and extreme jaw morphologies. Their global abundance and ecological significance, including contributions to the biological carbon pump, underscores the need to resolve their phylogeny amid escalating threats from climate change and human activities. RESULTS: We conducted the most comprehensive phylogenomic analysis of Stomiiformes to date, integrating 936 nuclear loci from 60 species and an expanded dataset of 135 species with mitochondrial sequences from publicly available repositories such as the Barcode of Life Data Systems (BOLD) database. We used maximum likelihood and coalescent-based approaches to assess family monophyly and relationships, including extensive quality control to address contamination in public databases. Our analyses reveal unstable tree topologies and complex evolutionary histories that challenge traditional classifications, while our quality control analyses identified 29% of BOLD sequences as misidentified or contaminated, emphasizing rigorous curation for deep-sea taxa. Congruent with a recent taxonomic treatment of Stomiiformes, the families Phosichthyidae and Gonostomatidae exhibit polyphyly and paraphyly, respectively, while subfamilies within Stomiidae are extensively non-monophyletic, leading us to recommend their abandonment. We propose the recognition of eight monophyletic families: Vinciguerriidae, Diplophidae, Gonostomatidae, Yarrellidae, Ichthyococcidae, Phosichthyidae, Sternoptychidae, and Stomiidae, supported by robust molecular and morphological evidence. CONCLUSIONS: This revised classification reflects the morphological and ecological diversity of Stomiiformes, aligning with their evolutionary diversification in the deep sea. Our phylogenomic framework resolves longstanding systematic uncertainties and highlights the power of genome-wide data in tackling taxonomically challenging clades. These findings provide a foundation for understanding deep-sea fish diversification and assessing the potential ecological drivers for their evolutionary diversity.

Animals↗
PubMed1999

Optimization of high-speed DNA sequencing on microfabricated capillary electrophoresis channels.

DNA sequencing separations have been performed in microfabricated electrophoresis channels with the goal of determining whether high-quality sequencing is feasible with these microdevices. The separation matrix, separation temperature, channel length and depth, injector size, and injection parameters were optimized. DNA fragment sizing separations demonstrated that 50-micron-deep channels provide the best sensitivity for our detection configuration. One-color sequencing separations of single-stranded M13mp18 DNA on 3% linear polyacrylamide (LPA) were used to optimize the twin-T injector size, injection conditions, and temperature. The best one-color separations were observed with a 250-micron twin-T injector, an injection time of 60 s, and a temperature of 35 degrees C. The first 500 bases appeared in 9.2 min with a resolution of > 0.5, and the separation extended to 700 bases. The best four-color sequencing separations were performed using 4% LPA, a temperature of 40 degrees C, and a 100-micron twin-T injector. These four-color runs were complete in only 20 min, could be automatically base-called using BaseFinder to over 600 bp after the primer, and were 99.4% accurate to 500 bp. These results significantly advance the quality of microchip-based electrophoretic sequencing and indicate the feasibility of performing high-speed genomic sequencing with microfabricated electrophoretic devices.

Base Sequence↗
PubMed2024

WilsonGenAI a deep learning approach to classify pathogenic variants in Wilson Disease.

BACKGROUND: Advances in Next Generation Sequencing have made rapid variant discovery and detection widely accessible. To facilitate a better understanding of the nature of these variants, American College of Medical Genetics and Genomics and the Association of Molecular Pathologists (ACMG-AMP) have issued a set of guidelines for variant classification. However, given the vast number of variants associated with any disorder, it is impossible to manually apply these guidelines to all known variants. Machine learning methodologies offer a rapid way to classify large numbers of variants, as well as variants of uncertain significance as either pathogenic or benign. Here we classify ATP7B genetic variants by employing ML and AI algorithms trained on our well-annotated WilsonGen dataset. METHODS: We have trained and validated two algorithms: TabNet and XGBoost on a high-confidence dataset of manually annotated, ACMG & AMP classified variants of the ATP7B gene associated with Wilson's Disease. RESULTS: Using an independent validation dataset of ACMG & AMP classified variants, as well as a patient set of functionally validated variants, we showed how both algorithms perform and can be used to classify large numbers of variants in clinical as well as research settings. CONCLUSION: We have created a ready to deploy tool, that can classify variants linked with Wilson's disease as pathogenic or benign, which can be utilized by both clinicians and researchers to better understand the disease through the nature of genetic variants associated with it.

Hepatolenticular Degeneration↗
PubMed1997

The effectiveness of mitochondrial rRNA gene sequences for the reconstruction of the phylogeny of an insect order (Orthoptera).

We investigated the value of mitochondrial rRNA sequences for analyzing pre-Cainozoic divergence events in insects. Using small subunit and large subunit rRNA sequences from 38 orthopteroid species, we examined several aspects of sequence evolution including secondary structure, substitution rate, and base composition. Substitution matrices calculated from the two genes were very similar, though differences were detected in rates of C-T transitions between paired and unpaired positions in secondary structures. By contrast, extreme disparities between substitution frequencies at different phylogenetic levels make character-transition weighting essential in parsimony reconstruction. The analysis of base composition indicated that branch attraction of at least two important lineages was due to shared base composition biases and to long branch attraction. The importance of taxonomic sampling and sequence length for the effectiveness of phylogenetic recovery using the rRNA fragments was also assessed. Significantly, combining the two sequences seemed both justifiable and necessary for this taxonomic sample. However, for reconstructing deep branches of phylogeny, it seems that increasing either or both the number of taxa or nucleotide positions will not necessarily solve all problems. Instead, the resolution of ancient branching events using mtDNA sequences probably depends upon the development and application of better specified reconstruction methods.

Animals↗
PubMed2003

African origin of polyomavirus JC and implications for prehistoric human migrations.

The presence of distinctive types of JC virus (JCV) in the main ethnic groups suggests a close coevolution with the human host. However, phylogenetic trees of JCV show a basal clade of European lineages (Types 1/4), whereas trees of human genes are coherent in placing the first split between African and non-African populations. This discrepancy places into question the effectiveness of JCV as a marker of human population history. The present study investigates the evolution of JCV using a large set of fully sequenced strains. Their relationships are first elucidated by principal coordinates analysis. It is suggested that Type 6 from West Africa could represent the ancestral type, while the peculiar phylogeny of Types 1/4 could reflect their direct origin from the ancestral lineage. Further credit to the African origin of JCV is provided by a neighbor-joining analysis based on slow-evolving sites. Sequence analysis of fast-evolving sites reveals that the deep emergence of Types 1/4 in the tree does not reflect a real evolutionary divergence; rather it is the implicit result of a remarkably different G + C content. The hypothesis that Types 1/4 originated directly from Type 6 is confirmed by examining the pattern of variation at a few specific fast-evolving sites. On the basis of this approach, a twofold exit of JCV from Africa is hypothesized: one in the direction of the Eurasian continent and another limited to Europe. These findings suggest that two distinct migrations of individuals played a key role in the peopling of Europe during prehistoric times.

Africa↗
PubMed2001

Unexpected diversity of small eukaryotes in deep-sea Antarctic plankton.

Phylogenetic information from ribosomal RNA genes directly amplified from the environment changed our view of the biosphere, revealing an extraordinary diversity of previously undetected prokaryotic lineages. Using ribosomal RNA genes from marine picoplankton, several new groups of bacteria and archaea have been identified, some of which are abundant. Little is known, however, about the diversity of the smallest planktonic eukaryotes, and available information in general concerns the phytoplankton of the euphotic region. Here we recover eukaryotes in the size fraction 0.2-5 microm from the aphotic zone (250-3,000 m deep) in the Antarctic polar front. The most diverse and relatively abundant were two new groups of alveolate sequences, related to dinoflagellates that are found at all studied depths. These may be important components of the microbial community in the deep ocean. Their phylogenetic position suggests a radiation early in the evolution of alveolates.

Animals↗
PubMed2000

Panfungal PCR and multiplex liquid hybridization for detection of fungi in tissue specimens.

A procedure based on panfungal PCR and multiplex liquid hybridization was developed for the detection of fungi in tissue specimens. The PCR amplified the fungal internal transcribed spacer (ITS) region (ITS1-5.8S rRNA-ITS2). After capture with specific probes, eight common fungal pathogens (Aspergillus flavus, Aspergillus fumigatus, Candida albicans, Candida krusei, Candida glabrata, Candida parapsilosis, Candida tropicalis, and Cryptococcus neoformans) were identified according to the size of the amplification product on an automated sequencer. The nonhybridized products were identified by sequencing. The performance of the procedure was examined with 12 deep-tissue specimens and 8 polypous tissue biopsies from the paranasal sinuses. A detection level of 0.1 to 1 pg of purified DNA (2 to 20 CFU) was achieved. Of the 20 specimens, PCR was positive for 19 (95%), of which 10 (53%) were hybridization positive. In comparison, 12 (60%) of the specimens were positive by direct microscopy, but only 7 (35%) of the specimens showed fungal growth. Sequencing of the nonhybridized amplification products identified an infecting agent in six specimens, and three specimens yielded only sequences of unknown fungal origin. The procedure provides a rapid (within 2 days) detection of common fungal pathogens in tissue specimens, and it is highly versatile for the identification of other fungal pathogens.

Adult↗
PubMed1990

[MR-angiography (MRA) in deep leg and pelvic venous thrombosis: a comparison with phlebography].

MRA by means of flow-phased gradient echo sequences is a valuable addition to phlebography for showing the extent of thrombosis in the veins of the pelvis and lower limbs. In eight out of 32 patients in whom the extent of deep vein thrombosis was not clearly shown by phlebography, it was possible to demonstrate the involvement of the inferior vena cava. Three of these patients had bilateral pelvic vein thrombosis. In seven out of 32 cases, thrombosis on the opposite side, which was not apparent clinically, could be demonstrated by MRA. Seven out of 32 patients showed involvement of the internal iliac vein. MRA is also valuable for observing the effect of treatment.

Adolescent↗
PubMed2005

Phylogeography of Barbary macaques (Macaca sylvanus) and the origin of the Gibraltar colony.

The Barbary macaque (Macaca sylvanus) is the earliest offshoot of the genus Macaca and the only extant African representative, all other species being Asiatic. Once distributed throughout North Africa, M. sylvanus is now restricted to isolated forest fragments in Algeria and Morocco. The species is threatened; the maximum total wild population size is estimated at 10,000 individuals. Relationships among surviving wild subpopulations in Algeria (96 samples) and Morocco (116 samples) were examined by using 468-bp sequences from hypervariable region I of the mitochondrial DNA control region. Twenty-four different haplotypes were identified, differing by 1-26 mutational steps (0.2-5.6%) and 1 insertion. With one exception (attributable to secondary introduction in coastal Morocco), Algerian and Moroccan haplotypes are clearly distinct. However, whereas Moroccan subpopulations show little divergence in hypervariable region I sequences and little correspondence with geographical distribution, there is a deep division between two main subpopulations in Algeria and one marked secondary division, with haplotypes generally matching geographical distribution. Accepting an origin of the genus Macaca of 5.5 million years ago, the Moroccan population and the two main Algerian subpopulations diverged approximately 1.6 million years ago. Distinction between Moroccan and Algerian haplotypes permitted analysis of the origin of the Gibraltar colony of Barbary macaques (68 samples; 30% of the population). It is generally held that the present Gibraltar population descended from a dozen individuals imported during World War II. However, the Gibraltar sample was found to include Algerian and Moroccan haplotypes separated by at least 16 mutational steps, revealing a dual origin of the founding females.

Algeria↗
PubMed2002

Mapping sequence differences between thimet oligopeptidase and neurolysin implicates key residues in substrate recognition.

The highly homologous endopeptidases thimet oligopeptidase and neurolysin are both restricted to short peptide substrates and share many of the same cleavage sites on bioactive and synthetic peptides. They sometimes target different sites on the same peptide, however, and defining the determinants of differential recognition will help us to understand how both enzymes specifically target a wide variety of cleavage site sequences. We have mapped the positions of the 224 surface residues that differ in sequence between the two enzymes onto the surface of the neurolysin crystal structure. Although the deep active site channel accounts for about one quarter of the total surface area, only 11% of the residue differences map to this region. Four isolated sequence changes (R470/E469, R491/M490, N496/H495, and T499/R498; neurolysin residues given first) are well positioned to affect recognition of substrate peptides, and differences in cleavage site specificity can be largely rationalized on the basis of these changes. We also mapped the positions of three cysteine residues believed to be responsible for multimerization of thimet oligopeptidase, a process that inactivates the enzyme. These residues are clustered on the outside of one channel wall, where multimerization via disulfide formation is unlikely to block the substrate-binding site. Finally, we mapped the regulatory phosphorylation site in thimet oligopeptidase to a location on the outside of the molecule well away from the active site, which indicates this modification has an indirect effect on activity.

Amino Acid Sequence↗
PubMed2002

A phylogenetic analysis of myosin heavy chain type II sequences corroborates that Acoela and Nemertodermatida are basal bilaterians.

Bilateria are currently subdivided into three superclades: Deuterostomia, Ecdysozoa, and Lophotrochozoa. Within this new taxonomic frame, acoelomate Platyhelminthes, for a long time held to be basal bilaterians, are now considered spiralian lophotrochozoans. However, recent 18S rDNA [small subunit (SSU)] analyses have shown Platyhelminthes to be polyphyletic with two of its orders, the Acoela and the Nemertodermatida, as the earliest extant bilaterians. To corroborate such position and avoid the criticisms of saturation and long-branch effects thrown on the SSU molecule, we have searched for independent molecular data bearing good phylogenetic information at deep evolutionary nodes. Here we report a phylogenetic analysis of DNA sequences from the myosin heavy chain type II (myosin II) gene from a large set of metazoans, including acoels and nemertodermatids. Our study demonstrates, both for the myosin II data set alone and for a combined SSU + myosin II data set, that Platyhelminthes are polyphyletic and that acoels and nemertodermatids are the extant earliest bilaterians. Hence, the common bilaterian ancestor was not, as currently held, large and complex but small, simple, and likely with direct development. This scenario has far-reaching implications for understanding the evolution of major body plans and for perceptions of the Cambrian evolutionary explosion.

Animals↗