The cranial structure of the Triconodonts

1963 ◽  
Vol 246 (727) ◽  
pp. 83-103 ◽  
Keyword(s):  
Common Ancestor ◽  
British Museum ◽  
Lateral Wall ◽  
Upper Jurassic ◽  
Last Common Ancestor ◽  
Lateral Boundary ◽  
Cranial Cavity ◽  
Chemical Methods ◽  
Mesozoic Mammals ◽  
The Brain

This paper is a study of the structure of the braincase in two closely related Mesozoic mammals: Triconodon mordax and Trioracodon ferox . They belong to the order Triconodonta, subfamily Triconodontinae, and are from the English Upper Jurassic (Purbeck). One specimen of each species was available showing cranial structure, both from the collection in the British Museum. By chemical methods, both petrosals and the sphenoid of the specimen of Triconodon and both petrosals of the specimen of Trioracodon were prepared. The material shows that the Triconodonta had a braincase of an essentially reptilian pattern. There was a persistent cavum epiptericum lying outside the ossified lateral wall (formed by the petrosal) of the braincase. The alisphenoid, forming the lateral boundary of the cavum epiptericum, formed no part of the braincase wall in this region. This was also true of the Rhaetic Morganucodon , and may have been true of all pre-Cretaceous mammals. In basic construction the braincase of these mammals differs from that of an advanced therapsid only in the narrower cavum epiptericum in the former. This difference is due to the relatively larger size of the brain in the mammal. To convert a braincase constructed in this way into that of a modern mammal either the alisphenoid would have to be lost—leading to the condition found in the monotremes—or the lateral wall of the neurocranum would have to fail to ossify—thus incorporating the cavum epiptericum in the cranial cavity in the manner typical of marsupials and placentals. Although on these grounds alone the monotreme stock need not have separated from that which gave rise to the marsupials and placentals until early in the Cretaceous, other considerations suggest that the last common ancestor lived in Triassic times at the reptilian grade of organization. There seems, however, less reason than formerly to consider Morganucodon an ancestral monotreme. Finally, a reconsideration of all the evidence shows that there was no acceleration of evolutionary rates at the time the Mammalia came into existence.

Inductive patterning of the embryonic brain in Drosophila

Development ◽  
2002 ◽  
Vol 129 (9) ◽  
pp. 2121-2128
Author(s):  
Damon T. Page
Keyword(s):  
Brain Development ◽  
Common Ancestor ◽  
Last Common Ancestor ◽  
Embryonic Brain ◽  
Germ Layers ◽  
Brain Anomaly ◽  
Prechordal Plate ◽  
Foregut Endoderm ◽  
The Brain ◽  
Brain Patterning

In vertebrates (deuterostomes), brain patterning depends on signals from adjacent tissues. For example, holoprosencephaly, the most common brain anomaly in humans, results from defects in signaling between the embryonic prechordal plate (consisting of the dorsal foregut endoderm and mesoderm) and the brain. I have examined whether a similar mechanism of brain development occurs in the protostome Drosophila, and find that the foregut and mesoderm act to pattern the fly embryonic brain. When the foregut and mesoderm of Drosophila are ablated, brain patterning is disrupted. The loss of Hedgehog expressed in the foregut appears to mediate this effect, as it does in vertebrates. One mechanism whereby these defects occur is a disruption of normal apoptosis in the brain. These data argue that the last common ancestor of protostomes and deuterostomes had a prototype of the brains present in modern animals, and also suggest that the foregut and mesoderm contributed to the patterning of this ‘proto-brain’. They also argue that the foreguts of protostomes and deuterostomes, which have traditionally been assigned to different germ layers, are actually homologous.

scholarly journals The comparative neuroprimatology 2018 (CNP-2018) road map for research on How the Brain Got Language

2018 ◽  
Vol 19 (1-2) ◽  
pp. 370-387 ◽  
Author(s):  
Michael A. Arbib ◽  
Francisco Aboitiz ◽  
Judith M. Burkart ◽  
Michael Corballis ◽  
Gino Coudé ◽  
...  
Keyword(s):  
Comparative Study ◽  
Cultural Evolution ◽  
Common Ancestor ◽  
Great Apes ◽  
Last Common Ancestor ◽  
Road Map ◽  
The Rich ◽  
The Comparative Study ◽  
Brain Behavior ◽  
The Brain

Abstract We present a new road map for research on “How the Brain Got Language” that adopts an EvoDevoSocio perspective and highlights comparative neuroprimatology – the comparative study of brain, behavior and communication in extant monkeys and great apes – as providing a key grounding for hypotheses on the last common ancestor of humans and monkeys (LCA-m) and chimpanzees (LCA-c) and the processes which guided the evolution LCA-m → LCA-c → protohumans → H. sapiens. Such research constrains and is constrained by analysis of the subsequent, primarily cultural, evolution of H. sapiens which yielded cultures involving the rich use of language.

Computational challenges of evolving the language-ready brain

2018 ◽  
Vol 19 (1-2) ◽  
pp. 7-21 ◽  
Author(s):  
Michael A. Arbib
Keyword(s):  
Computational Modeling ◽  
Common Ancestor ◽  
Homo Sapiens ◽  
Mirror System ◽  
Last Common Ancestor ◽  
New Challenges ◽  
The Brain

Abstract Computational modeling of the macaque brain grounds hypotheses on the brain of LCA-m (the last common ancestor of monkey and human). Elaborations thereof provide a brain model for LCA-c (c for chimpanzee). The Mirror System Hypothesis charts further steps via imitation and pantomime to protosign and protolanguage on the path to a "language-ready brain" in Homo sapiens, with the path to speech being indirect. The material poses new challenges for both experimentation and modeling.

scholarly journals Ambulacrarian insulin-related peptides and their putative receptors suggest how insulin and similar peptides may have evolved from Insulin-like Growth Factor

2021 ◽  
Author(s):  
Jan Adrianus Veenstra
Keyword(s):  
Receptor Tyrosine Kinase ◽  
Common Ancestor ◽  
Neuroendocrine Cells ◽  
Last Common Ancestor ◽  
Gene Duplications ◽  
Hormonal Signal ◽  
Intracellular Response ◽  
G Protein Coupled ◽  
The Brain ◽  
Insulin Like Growth Factors

Background: Insulin is evolutionarily related to the insulin-like growth factors (IGFs) and like the latter stimulates a receptor tyrosine kinase (RTK) that transfers the extracellular hormonal signal into an intracellular response. Other hormones related to insulin, such as relaxin, do not use an RTK, but a G-protein coupled receptor (GPCR). This is unusual since evolutionarily related hormones typically either use the same or paralogous receptors. In arthropods three different IGF-related peptides likely evolved from a gene triplication, as in several species genes coding these three peptides are located next to one another on the same chromosomal fragment. Of these three hormones one, an IGF-like hormone, acts through an RTK, while the other two use a GPCR. This suggests that the ancestral IGF-like peptide may have used both types of receptors. These arthropod insulin-like peptides have homologs in vertebrates, which suggests that the initial gene triplication was perhaps already present in the last common ancestor of deuterostomes and protostomes. It would be interesting to know whether this is indeed so and to establish how insulin and other insulin-like peptides might be related to this trio of IGF-related hormones. Methodology: Genes coding insulin and related peptides as well as their putative receptors were identified in genomes and transcriptomes from echinoderms and hemichordates. Results: A similar triplet of genes coding insulin-like peptides is also found in some hemichordates and echinoderms. Two of the three ambulacrarian peptides are orthologs of arthropod IGF and Drosophila insulin-like peptide 7 (dilp7), while the third one looks like an ortholog of the arthropod peptide gonadulin. In echinoderms two novel insulin-like peptides emerged, gonad stimulating substance (GSS) and multinsulin, likely from gene duplications of the IGF and dilp7-like genes respectively. However, no novel receptors for insulin-like peptides evolved. If IGF were to act through both a GPCR and an RTK it would suggest that GSS acts on only one of the two receptors, possibly the RTK. The evolution of GSS from IGF may represent a pattern, where IGF gene duplications lead to novel genes coding shorter peptides that have lost their ability to activate a GPCR. It is likely this is how insulin and the insect neuroendocrine insulin-like peptides evolved independently from IGF. Conclusion: The local gene triplication previously described from arthropods that yielded three genes coding IGF-related peptides was already present in the last common ancestor of protostomes and deuterostomes. It seems plausible that insulin and other insulin-like peptides, such as those produced by neuroendocrine cells in the brain of insects and echinoderm GSS evolved independently from IGF and thus are not true orthologs, but the result of convergent evolution.

scholarly journals The brain of the archæoceti

1903 ◽  
Vol 71 (467-476) ◽  
pp. 322-331 ◽  
Keyword(s):  
British Museum ◽  
Plaster Cast ◽  
Cranial Cavity ◽  
Egyptian Desert ◽  
The Brain ◽  
Made In

So far as I have been able to ascertain, nothing whatever is known of the form of the brain or, more strictly, of the cranial cavity in the Archæoceti. Hence no apology is needed for presenting even this imperfect account of two cranial casts representative of this sub-order, which have come into my hands. Among the Eocene remains found in the Fayûm region of the Egyptian desert by Mr. H. J. L. Beadnell and Dr. Charles W. Andrews, in 1901, there was a broken skull of Zeuglodon , from which it was possible to obtain a mould, representing the form of the greater part of the dorsal and lateral aspects of the brain. A plaster cast was made in the British Museum at the instance of Dr. Andrews, who kindly placed it at my disposal for description.

scholarly journals Experimental evidence for yawn contagion in orangutans (Pongo pygmaeus)

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Evy van Berlo ◽  
Alejandra P. Díaz-Loyo ◽  
Oscar E. Juárez-Mora ◽  
Mariska E. Kret ◽  
Jorg J. M. Massen
Keyword(s):  
Experimental Evidence ◽  
Common Ancestor ◽  
Great Apes ◽  
Pongo Pygmaeus ◽  
Last Common Ancestor ◽  
Contagious Yawning ◽  
Proximate Mechanism ◽  
Social Species ◽  
Ultimate Causation

AbstractYawning is highly contagious, yet both its proximate mechanism(s) and its ultimate causation remain poorly understood. Scholars have suggested a link between contagious yawning (CY) and sociality due to its appearance in mostly social species. Nevertheless, as findings are inconsistent, CY’s function and evolution remains heavily debated. One way to understand the evolution of CY is by studying it in hominids. Although CY has been found in chimpanzees and bonobos, but is absent in gorillas, data on orangutans are missing despite them being the least social hominid. Orangutans are thus interesting for understanding CY’s phylogeny. Here, we experimentally tested whether orangutans yawn contagiously in response to videos of conspecifics yawning. Furthermore, we investigated whether CY was affected by familiarity with the yawning individual (i.e. a familiar or unfamiliar conspecific and a 3D orangutan avatar). In 700 trials across 8 individuals, we found that orangutans are more likely to yawn in response to yawn videos compared to control videos of conspecifics, but not to yawn videos of the avatar. Interestingly, CY occurred regardless of whether a conspecific was familiar or unfamiliar. We conclude that CY was likely already present in the last common ancestor of humans and great apes, though more converging evidence is needed.

scholarly journals Recombinant transfer in the basic genome ofEscherichia coli

2015 ◽  
Vol 112 (29) ◽  
pp. 9070-9075 ◽  
Author(s):  
Purushottam D. Dixit ◽  
Tin Yau Pang ◽  
F. William Studier ◽  
Sergei Maslov
Keyword(s):  
Common Ancestor ◽  
Recipient Cell ◽  
Gene Clusters ◽  
Selective Advantage ◽  
Last Common Ancestor ◽  
Genome Sequences ◽  
Bacterial Genomes ◽  
Basic Genome ◽  
Single Base Pair ◽  
Generalized Transduction

An approximation to the ∼4-Mbp basic genome shared by 32 strains ofEscherichia colirepresenting six evolutionary groups has been derived and analyzed computationally. A multiple alignment of the 32 complete genome sequences was filtered to remove mobile elements and identify the most reliable ∼90% of the aligned length of each of the resulting 496 basic-genome pairs. Patterns of single base-pair mutations (SNPs) in aligned pairs distinguish clonally inherited regions from regions where either genome has acquired DNA fragments from diverged genomes by homologous recombination since their last common ancestor. Such recombinant transfer is pervasive across the basic genome, mostly between genomes in the same evolutionary group, and generates many unique mosaic patterns. The six least-diverged genome pairs have one or two recombinant transfers of length ∼40–115 kbp (and few if any other transfers), each containing one or more gene clusters known to confer strong selective advantage in some environments. Moderately diverged genome pairs (0.4–1% SNPs) show mosaic patterns of interspersed clonal and recombinant regions of varying lengths throughout the basic genome, whereas more highly diverged pairs within an evolutionary group or pairs between evolutionary groups having >1.3% SNPs have few clonal matches longer than a few kilobase pairs. Many recombinant transfers appear to incorporate fragments of the entering DNA produced by restriction systems of the recipient cell. A simple computational model can closely fit the data. Most recombinant transfers seem likely to be due to generalized transduction by coevolving populations of phages, which could efficiently distribute variability throughout bacterial genomes.

Improved resolution of recalcitrant nodes in the animal phylogeny through the analysis of genome gene content and morphology

2021 ◽  
Author(s):  
Ksenia Juravel ◽  
Luis Porras ◽  
Sebastian Hoehna ◽  
Davide Pisani ◽  
Gert Wörheide
Keyword(s):  
Common Ancestor ◽  
Sister Group ◽  
The Other ◽  
Gene Content ◽  
Statistical Hypothesis ◽  
Phylogenetic Position ◽  
Last Common Ancestor ◽  
Statistical Hypothesis Testing ◽  
Animal Phylogeny ◽  
Phylogenetic Hypotheses

An accurate phylogeny of animals is needed to clarify their evolution, ecology, and impact on shaping the biosphere. Although multi-gene alignments of up to several hundred thousand amino acids are nowadays routinely used to test hypotheses of animal relationships, some nodes towards the root of the animal phylogeny are proving hard to resolve. While the relationships of the non-bilaterian lineages, primarily sponges (Porifera) and comb jellies (Ctenophora), have received much attention since more than a decade, controversies about the phylogenetic position of the worm-like bilaterian lineage Xenacoelomorpha and the monophyly of the "Superphylum" Deuterostomia have more recently emerged. Here we independently analyse novel genome gene content and morphological datasets to assess patterns of phylogenetic congruence with previous amino-acid derived phylogenetic hypotheses. Using statistical hypothesis testing, we show that both our datasets very strongly support sponges as the sister group of all the other animals, Xenoacoelomorpha as the sister group of the other Bilateria, and largely support monophyletic Deuterostomia. Based on these results, we conclude that the last common animal ancestor may have been a simple, filter-feeding organism without a nervous system and muscles, while the last common ancestor of Bilateria might have been a small, acoelomate-like worm without a through gut.

Natural history of ABC systems: not only transporters

2011 ◽  
Vol 50 ◽  
pp. 19-42 ◽  
Author(s):  
Elie Dassa
Keyword(s):  
Common Ancestor ◽  
Three Dimensional ◽  
Last Common Ancestor ◽  
Abc Proteins ◽  
Hypothetical Scenario ◽  
History Of ◽  
Phylogenetic Perspective ◽  
Living Organisms

In recent years, our understanding of the functioning of ABC (ATP-binding cassette) systems has been boosted by the combination of biochemical and structural approaches. However, the origin and the distribution of ABC proteins among living organisms are difficult to understand in a phylogenetic perspective, because it is hard to discriminate orthology and paralogy, due to the existence of horizontal gene transfer. In this chapter, I present an update of the classification of ABC systems and discuss a hypothetical scenario of their evolution. The hypothetical presence of ABC ATPases in the last common ancestor of modern organisms is discussed, as well as the additional possibility that ABC systems might have been transmitted to eukaryotes, after the two endosymbiosis events that led to the constitution of eukaryotic organelles. I update the functional information of selected ABC systems and introduce new families of ABC proteins that have been included recently into this vast superfamily, thanks to the availability of high-resolution three-dimensional structures.

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