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The triceps brachii muscle occupies the posterior compartment of the arm in humans and has three heads. The lateral and medial heads originate from the humerus and the long head arises from the infraglenoid tubercle of the scapula. All heads form a common tendon that inserts onto the olecranon and the deep antebrachial fascia on each side of it. Each head receives its own motor branch, which all are thought to originate from the radial nerve. However, several studies reported that the motor branch of the long head of the triceps (LHT) arises from the axillary nerve or the posterior cord. Here, we dissected 27 triceps in 15 cadavers to analyze the innervation of the LHT and found only radial innervation, which contradicts those studies. We examined studies reporting that the motor branch to the LHT in humans does not arise from the radial nerve as well as studies of the triceps in primates. Occasional variations of the innervation of skeletal muscles are normal, but a change of principal motor innervation from radial to axillary nerve has important implications. This is because the axillary nerve is often involved during shoulder injuries. The precise identification of the prevalence of axillary versus radial innervation is therefore clinically relevant for surgery, nerve drafting, and occupational and physical therapy. We conclude that the primary motor branch to the LHT arises from the radial nerve but axillary/posterior cord innervations occur occasionally. We suggest the development of a standard methodology for further studies. Anat Rec, 301:473-483, 2018. © 2018 Wiley Periodicals, Inc.

Few descriptions of the musculoskeletal system of humans with anencephaly or spina bifida exist in the literature. Even less is published about individuals in which both phenomena occur together, i.e. about craniorachischisis. Here we provide a detailed report on the musculoskeletal structures of a fetus with craniorachischisis, as well as comparisons with the few descriptions for anencephaly and with musculoskeletal anomalies found in other congenital malformations. We focused in particular on the comparison with trisomies 13, 18, and 21 because neural tube defects have been associated with such chromosomal defects. Our results showed that many of the defects found in the fetus with craniorachischisis are similar not only to anomalies previously described in the available works on musculoskeletal phenotypes seen in fetuses with anencephaly and spina bifida, but also to a wide range of other different conditions/syndromes including trisomies 13, 18 and 21, and cyclopia. The fact that similar anomalies are seen commonly not only in a wide range of different syndromes, but also as variants of the normal human population and as the 'normal' phenotype of other animals, supports Pere Alberch's unfortunately named idea of a 'logic of monsters'. That is, it supports the idea that development is so constrained that both in 'normal' and abnormal development one sees certain outcomes being produced again and again because ontogenetic constraints only allow a few possible outcomes, thus also leading to cases where the anatomical defects of some organisms are similar to the 'normal' phenotype of other organisms. In fact, this applies not only to specific anomalies but also to general patterns, such as the fact that in pathological conditions affecting different regions of the body, one consistently sees more defects on the upper limbs than on the lower limbs. Such general patterns are, again, seen in the fetus examined for this study, which had 29 muscle anomalies on the right upper limb and 22 muscle anomalies on the left upper limb, vs. seven muscle anomalies on the right lower limb and two on the left lower limb. It is therefore hoped that this work, which is part of our effort to describe and compile information on human musculoskeletal defects found in a wide range of conditions, will contribute not only to a better understanding of craniorachischisis in particular and of human congenital malformations in general, but also to broader discussions on the fields of comparative anatomy, and developmental and evolutionary biology.

It is usually assumed that Galen is one of the fathers of anatomy and that between the Corpus Galenicum and the Renaissance there was no major advance in anatomical knowledge. However, it is also consensually accepted that Muslim scholars had the intellectual leadership from the 8th/9th to 13th centuries, and that they made remarkable progresses in numerous scientific fields including medicine. So, how is it possible that they did not contribute to advance human anatomy during that period? According to the dominant view, Muslim scholars exclusively had a passive role: their transmission of knowledge from the Greeks to the West. Here, we summarize, for the first time in a single paper, the studies of major Muslim scholars that published on human anatomy before Vesalius. This summary is based on analyses of original Arabic texts and of more recent publications by anatomists and historians, and on comparisons between the descriptions provided by Galen and by these Muslim scholars. We show that Arabic speakers and Persians made important advances in human anatomy well before Vesalius. The most notable exception concerns the muscular system: strikingly, there were apparently neither advances made by Muslims nor by Westerners for more than 1000 years. Unbiased discussions of these and other related issues, and particularly of the mainly untold story about the major contributions of Muslim scholars to anatomy, are crucial to our knowledge of the history of anatomy, biology and sciences, and also of our way of thinking, biases, and prejudices. Anat Rec, 300:986-1008, 2017. © 2017 Wiley Periodicals, Inc.

We introduce a new subfield of the recently created field of Evolutionary-Developmental-Anthropology (Evo-Devo-Anth): Evolutionary-Developmental-Pathology-and-Anthropology (Evo-Devo-P'Anth). This subfield combines experimental and developmental studies of nonhuman model organisms, biological anthropology, chordate comparative anatomy and evolution, and the study of normal and pathological human development. Instead of focusing on other organisms to try to better understand human development, evolution, anatomy, and pathology, it places humans as the central case study, i.e., as truly model organism themselves. We summarize the results of our recent Evo-Devo-P'Anth studies and discuss long-standing questions in each of the broader biological fields combined in this subfield, paying special attention to the links between: (1) Human anomalies and variations, nonpentadactyly, homeotic transformations, and "nearest neighbor" vs. "find and seek" muscle-skeleton associations in limb+facial muscles vs. other head muscles; (2) Developmental constraints, the notion of "phylotypic stage," internalism vs. externalism, and the "logic of monsters" vs. "lack of homeostasis" views about human birth defects; (3) Human evolution, reversions, atavisms, paedomorphosis, and peromorphosis; (4) Scala naturae, Haeckelian recapitulation, von Baer's laws, and parallelism between phylogeny and development, here formally defined as "Phylo-Devo parallelism"; and (5) Patau, Edwards, and Down syndrome (trisomies 13, 18, 21), atavisms, apoptosis, heart malformations, and medical implications.

Recent findings that urochordates are the closest sister-group of vertebrates have dramatically changed our understanding of chordate evolution and vertebrate origins. To continue to deepen our understanding of chordate evolution and diversity, in particular the morphological and taxonomical diversity of the vertebrate clade, one must explore the origin, development, and comparative anatomy of not only hard tissues, but also soft tissues such as muscles. Building on a recent overview of the discovery of a cardiopharyngeal field in urochordates and the profound implications for reconstructing the origin and early evolution of vertebrates, in this study we focus on the broader comparative and developmental anatomy of chordate cephalic muscles and their relation to life history, and to developmental, morphological and taxonomical diversity. We combine our recent findings on cephalochordates, urochordates, and vertebrates with a literature review and suggest that developmental changes related to metamorphosis and/or heterochrony (e.g., peramorphosis) played a crucial role in the early evolution of chordates and vertebrates. Recent studies reviewed here supported de Beer's “law of diversity” that peramorphic animals (e.g., ascidians, lampreys) are taxonomically and morphologically less diverse than nonperamorphic animals (e.g., gnathostomes), probably because their “too specialized” development and adult anatomy constrain further developmental and evolutionary innovations. Developmental Dynamics 244:1046–1057, 2015. © 2014 Wiley Periodicals, Inc.

Craniofacial malformations are common congenital defects caused by failed midline inductive signals. These midline defects are associated with exposure of the fetus to exogenous teratogens and with inborn genetic errors such as those found in Down, Patau, Edwards' and Smith–Lemli–Opitz syndromes. Yet, there are no studies that analyze contributions of synchronous neurocranial and neural development in these disorders. Here we present the first in-depth analysis of malformations of the basicranium of a holoprosencephalic (HPE) trisomy 18 (T18; Edwards' syndrome) fetus with synophthalmic cyclopia and alobar HPE. With a combination of traditional gross dissection and state-of-the-art computed tomography, we demonstrate the deleterious effects of T18 caused by a translocation at 18p11.31. Bony features included a single developmentally unseparated frontal bone, and complete dual absence of the anterior cranial fossa and ethmoid bone. From a superior view with the calvarium plates removed, there was direct visual access to the orbital foramen and hard palate. Both the eyes and the pituitary gland, normally protected by bony structures, were exposed in the cranial cavity and in direct contact with the brain. The middle cranial fossa was shifted anteriorly, and foramina were either missing or displaced to an abnormal location due to the absence or misplacement of its respective cranial nerve (CN). When CN development was conserved in its induction and placement, the respective foramen developed in its normal location albeit with abnormal gross anatomical features, as seen in the facial nerve (CNVII) and the internal acoustic meatus. More anteriorly localized CNs and their foramina were absent or heavily disrupted compared with posterior ones. The severe malformations exhibited in the cranial fossae, orbital region, pituitary gland and sella turcica highlight the crucial involvement of transcription factors such as TGIF, which is located on chromosome 18 and contributes to neural patterning, in the proper development of neural and cranial structures. Our study of a T18 specimen emphasizes the intricate interplay between bone and brain development in midline craniofacial abnormalities in general.

Here we present the first study comparing all the paired appendages muscles of representatives of each major extant gnathostome group. We address a crucial and enigmatic question in evolutionary and comparative anatomy: Why are the pelvic and pectoral appendages of gnathostomes, and particularly of tetrapods, in general so similar to each other? We argue that an integrative analysis of the new myological data and the information from the literature contradicts the idea that the forelimbs and hindlimbs are serial homologues. The data show that many of the strikingly similar fore- and hindlimb muscles of extant tetrapods evolved independently in each appendage because the ancestors of extant gnathostomes and osteichthyans only had an adductor and an abductor in each fin. Therefore, these data contradict the idea that at least some muscles present in the tetrapod fore- and hindlimbs were already present in some form in the first fishes with pectoral and pelvic appendages, as the result of an ancestral duplication of the paired appendages leading to a true serial homology. The origin of the pectoral girdle was instead likely related to head evolution, as illustrated by the cucullaris of gnathostomes such as chondrichthyans inserting onto both the branchial arches and pectoral girdle. Only later in evolution the cucullaris became differentiated into the levatores arcuum branchialium and protractor pectoralis, which gave rise to the amniote neck muscles trapezius and sternocleidomastoideus. These changes therefore contributed to an evolutionary trend toward a greater anatomical and functional independence of the pectoral girdle from head movements. Anat Rec, 00:000–000, 2014. V C 2014 Wiley Periodicals, Inc.

William K. Gregory was one of the most influential authors defending the existence of an evolutionary trend in vertebrates from a higher degree of polyisomerism (more polyisomeric or 'serial' anatomical structures arranged along any body axis) to cases of anisomerism (specialization or loss of at least some original polyisomeric structures). Anisomerism was the subject of much interest during the 19th and the beginning of the 20th centuries, particularly due to the influence of the Romantic German School and the notion of 'primitive archetype' and because it was conceptually linked to other crucial biological issues (e.g. complexity, scala naturae, progress, modularity or phenotypic integration). However, discussions on anisomerism and related issues (e.g. Williston's law) have been almost exclusively based on hard tissues. Here we provide the first detailed empirical test, and discussion, of anisomerism based on quantitative data obtained from phylogenetic and comparative analyses of the head and forelimb muscles of gnathostomes. Our results strongly support the existence of such a trend in both forelimb and head musculature. For instance, the last common ancestor (LCA) of extant tetrapods likely had 38 polyisomeric muscles (PMs) out of a total of 70 forelimb muscles (i.e. 54%), whereas in the LCAs of extant amniotes and of mammals these numbers were 38/73 (52%) and 21/67 (31%), and in humans are 11/59 (19%). Interestingly, the number of PMs that became specialized during the forelimb evolutionary transition from the LCA of extant tetrapods to humans (13) is very similar to the number of PMs that became lost (14), indicating that both specialization and loss contributed equally to the trend towards anisomerism. By contrast, during the evolution of the head musculature from the LCA of gnathostomes to humans a total of 27 PMs were lost whereas only one muscle became specialized. Importantly, the evolutionary trend towards anisomerism is not related to a general trend leading to the presence of fewer muscles in derived taxa, because for instance humans have more head muscles in total, but many less head polyisomeric muscles than early gnathostomes and extant fish such as sharks, and than early tetrapods and amphibians such as salamanders. This is because new muscles have also been acquired during gnathostome evolution (e.g. facial muscles of mammals). Interestingly, many new PMs have also been acquired during head evolution (but subsequently lost during the transitions towards humans), whereas only a few new PMs were acquired during forelimb evolution. Our comparisons and review of the literature indicate that there is also a trend towards anisomerism during development, thus providing a further example of a parallel between ontogeny and phylogeny, e.g. some forelimb PMs (e.g. contrahentes, intermetacarpales) become specialized or lost (re-absorbed) during human ontogeny and some head PMs (e.g. constrictores branchiales) become lost during salamander ontogeny. This review will inform future discussions on modularity, complexity, body plans, phenotypic integration and macroevolution, which should ideally include soft tissues and the use of new tools (e.g. anatomical networks) in order to provide a broader and more integrative understanding of these relevant subjects.

The notion of scala naturae dates back to thinkers such as Aristotle, who placed plants below animals and ranked the latter along a graded scale of complexity from 'lower' to 'higher' animals, such as humans. In the last decades, evolutionary biologists have tended to move from one extreme (i.e. the idea of scala naturae or the existence of a general evolutionary trend in complexity from 'lower' to "higher" taxa, with Homo sapiens as the end stage) to the other, opposite, extreme (i.e. to avoid using terms such as 'phylogenetically basal' and 'anatomically plesiomorphic' taxa, which are seen as the undesired vestige of old teleological theories). The latter view tries to avoid any possible connotations with the original anthropocentric idea of a scala naturae crowned by man and, in that sense, it can be regarded as a more politically correct view. In the past years and months there has been renewed interest in these topics, which have been discussed in various papers and monographs that tend to subscribe, in general, to the points defended in the more politically correct view. Importantly, most evolutionary and phylogenetic studies of tetrapods and other vertebrates, and therefore most discussions on the scala naturae and related issues have been based on hard tissue and, more recently, on molecular data. Here we provide the first discussion of these topics based on a comparative myological study of all the major vertebrate clades and of myological cladistic and Bayesian phylogenetic analyses of bony fish and tetrapods, including Primates. We specifically (i) contradict the notions of a scala naturae or evolutionary progressive trends leading to more complexity in 'higher' animals and culminating in Homo sapiens, and (ii) stress that the refutation of these old notions does not necessarily mean that one should not keep using the terms 'phylogenetically basal' and particularly 'anatomically plesiomorphic' to refer to groups such as the urodeles within the Tetrapoda, or the strepsirrhines and lemurs within the Primates, for instance. This review will contribute to improving our understanding of these broad evolutionary issues and of the evolution of the vertebrate Bauplans, and hopefully will stimulate future phylogenetic, evolutionary and developmental studies of these clades.

Parsimov is a parsimony-based method for identifying the minimum number of heterochronic event-shifts on all branches of a given phylogenetic framework to explain the developmental sequences seen in the species investigated, and has been used to investigate the evolution of developmental sequences in various animal groups. However, the biological interpretation of the results is difficult not least because Parsimov uses non-independent data resulting from event-pairing as the basis for its analyses. To test the applicability of Parsimov to a large data set, larval cranial muscle development was studied in 15 anurans, three caudates and the Australian lungfish. We analyzed the developmental sequences with Parsimov to investigate: if there are (1) heterochronies on deep branches of a cladogram indicating changes in the ancestral sequences, (2) heterochronies that can be related to larval life-history, and (3) the sensitivity of the analysis to different underlying cladograms. We discovered general patterns of cranial muscle development, such as an anterior-to-posterior gradient, an outside-in pattern and a tendency for cranial muscles to develop from their region of origin toward their insertion. We found most heterochronies on terminal branches and only a few shifts on deep branches in the cladograms indicating changes in the ancestral sequences. No changes could be related to larval life-history. The underlying cladogram clearly influenced the outcome of the analysis. We propose that Parsimov has the potential, combined with other methods, to find evolutionary important changes and to aid the biological interpretation of these changes.

Here we provide the first detailed description, based on immunohistochemistry and dissections, of the limb muscle development in the direct developing frog Eleutherodactylus coqui. We compare E. coqui with other tetrapods and discuss our results in a broad evolutionary and developmental context to address some major questions concerning the origin, evolution, and ontogeny of the tetrapod limbs. Our observations and comparisons: (1) support the "in-out" developmental mechanism of the appendicular pectoral muscles; (2) show that the protractor pectoralis and its amniote derivatives trapezius and sternocleidomastoideus clearly develop, anatomically, from the branchial muscles; (3) corroborate that the similarity between the forearm/hand and the leg/foot muscles in tetrapods is due to derived homoplasic events that occurred during the fins-limbs transition and not due to serial homology; (4) lend some support for the hypothesis that the morphological transformation of the anuran tibiale and fibulare represents a distal shift in the zeugo-autopodial border; (5) provide evidence that the identity of the tetrapod hand and foot muscles is mainly related to the topological position of the digits to which they attach; and (6) for the first time, show that apart from a proximo-distal morphogenetic gradient there is also an ulno-radial/fibulo-tibial gradient within the development of the fore- and hindlimb muscles and a dorsoventral gradient within the ontogeny of the hindlimb (but not forelimb) muscles of the frog E. coqui; the two latter gradients are seen in the ontogeny of amniotes such as chickens but are markedly different to those seen in axolotl regeneration and ontogeny.

There is still confusion about the homology of several cranial muscles in salamanders with those of other vertebrates. This is true, in part, because of the fact that many muscles present in early ontogeny of amphibians disappear during development and specifically during metamorphosis. Resolving this confusion is important for the understanding of the comparative and evolutionary morphology of vertebrates and tetrapods because amphibians are the phylogenetically most plesiomorphic tetrapods, concerning for example their myology, and include two often used model organisms, Xenopus laevis (anuran) and Ambystoma mexicanum (urodele). Here we provide the first detailed report of the cranial muscle development in axolotl from early ontogenetic stages to the adult stage. We describe different and complementary types of general muscle morphogenetic gradients in the head: from anterior to posterior, from lateral to medial, and from origin to insertion. Furthermore, even during the development of neotenic salamanders such as axolotls, various larval muscles become indistinct, contradicting the commonly accepted view that during ontogeny the tendency is mostly toward the differentiation of muscles. We provide an updated comparison between these muscles and the muscles of other vertebrates, a discussion of the homologies and evolution, and show that the order in which the muscles appear during axolotl ontogeny is in general similar to their appearance in phylogeny (e.g. differentiation of adductor mandibulae muscles from one anlage to four muscles), with only a few remarkable exceptions, as for example the dilatator laryngis that appears evolutionary later but in the development before the intermandibularis. Anat Rec, 296:1031–1048, 2013. © 2013 Wiley Periodicals, Inc.

Ziermann, J.M., Infante, C., Hanken, J. and Olsson, L. 2011. Morphology of the cranial skeleton and musculature in the obligate carnivorous tadpole of Lepidobatrachus laevis (Anura: Ceratophryidae). —Acta Zoologica (Stockholm) 00:1–12. Lepidobatrachus laevis (Ceratophryidae: Ceratophryinae) is a bizarre frog endemic to the Chacoan desert of central South America. Its tadpole is an obligate carnivore that can catch and consume live prey nearly its own size. Morphological adaptations associated with this unique feeding mode, including the larval skull anatomy and associated cranial musculature, have only been partly described. We studied the head of Stages 26–27 larvae using gross dissection, immunohistochemistry, and standard histology. Derived features of this tadpole compared to the microphagous, herbivorous larvae of most other anurans include simplified chondrocranial cartilages and very robust jaw muscles. The mm. suspensorio- et quadratoangularis do not take their origin from the processus muscularis of the palatoquadrate, as in most other tadpoles, but instead originate from the corpus of the palatoquadrate caudal to this process. The jaw levators are unusually large. The tadpole of Ceratophrys, another member of the ceratophryine clade, also consumes large animal prey, but its morphology is very different. It probably has evolved independently from a generalized, mainly herbivorous tadpole similar to the larva of Chacophrys, the third ceratophryine genus. Most specialized features of the larval head of Lepidobatrachus laevis are adaptations for ‘megalophagy’—ingestion of whole, very large animal prey.

Patterning of craniofacial muscles overtly begins with the activation of lineage-specific markers at precise, evolutionarily conserved locations within prechordal, lateral, and both unsegmented and somitic paraxial mesoderm populations. Although these initial programming events occur without influence of neural crest cells, the subsequent movements and differentiation stages of most head muscles are neural crest-dependent. Incorporating both descriptive and experimental studies, this review examines each stage of myogenesis up through the formation of attachments to their skeletal partners. We present the similarities among developing muscle groups, including comparisons with trunk myogenesis, but emphasize the morphogenetic processes that are unique to each group and sometimes subsets of muscles within a group. These groups include branchial (pharyngeal) arches, which encompass both those with clear homologues in all vertebrate classes and those unique to one, for example, mammalian facial muscles, and also extraocular, laryngeal, tongue, and neck muscles. The presence of several distinct processes underlying neural crest:myoblast/myocyte interactions and behaviors is not surprising, given the wide range of both quantitative and qualitative variations in craniofacial muscle organization achieved during vertebrate evolution.

Our research on the evolution of head development focuses on understanding the developmental origins of morphological innovations and involves asking questions like: How flexible (or conserved) are cell fates, patterns of cell migration or the timing of developmental events (heterochrony)? How do timing changes, or changes in life history affect head development and growth? Our ‘model system’ is a comparison between lungfishes and representatives from all three extant groups of amphibians. Within anuran amphibians, major changes in life history such as the repeated evolution of larval specializations (e.g. carnivory), or indeed the loss of a free-swimming larva, allows us to test for developmental constraints. Cell migration and cell fate are conserved in cranial neural crest cells in all vertebrates studied so far. Patterning and developmental anatomy of cranial neural crest and head mesoderm cells are conserved within amphibians and even between birds, mammals and amphibians. However, the specific formation of hypobranchial muscles from ventral somitic processes shows variation within tetrapods. The evolution of carnivorous larvae in terminal taxa is correlated with changes in both pattern and timing of head skeletal and muscle development. Sequence-heterochronic changes are correlated with feeding mode in terminal taxa and with phylogenetic relatedness in basal branches of the phylogeny. Eye muscles seem to form a developmental module that can evolve relatively independently from other head muscles, at least in terms of timing of muscle differentiation.

The African Clawed Toad, Xenopus laevis, has been a major vertebrate model organism for developmental studies for half a century. Because most studies have focused on the early stages of development, this has had the effect that many aspects of organogenesis and later development remain relatively poorly known in this species. In particular, little is known about cranial muscle development even at the level of morphology and histological differentiation of muscle anlagen and muscle fibers. In this study, we document the morphogenesis and histological differentiation of cranial muscles in X. laevis. We provide a detailed account of the timing of development for each of the cranial muscles, and also describe a new muscle, the m. transversus anterior. The cranial musculature of X. laevis larvae generally develops in a rostrocaudal sequence. The first muscles to differentiate are the extrinsic eye muscles. Muscles of the mandibular and hyoid arches develop almost simultaneously, and are followed by the muscles of the branchial arches and the larynx, and by the mm. geniohyoideus and rectus cervicis. Despite the fact that differentiation starts at different stages in the different muscles, most are fully developed at Stage 14. These baseline data on the timing of muscle differentiation in the X. laevis can serve as a foundation for comparative studies of heterochronic changes in cranial muscle development in frogs and other lissamphibians.

Evolutionary and anatomical textbooks tend to completely neglect, or include just a few pages about, the contributions of Muslim scholars for the discovery of human anatomy and particularly for the history of evolutionary thinking. This negligence is the result of complex historical biases, has profound implications, creates several misconceptions, and does not allow the general public and teachers, students and researchers to fully understand the true history of anatomical and evolutionary discovery. In an original project done at one of the most historical US universities - Howard - involving graduate students, faculty members, and their colleagues from other institutions, we did an extensive literature review of ancient texts written in various languages, particularly before Vesalius (about human anatomy) and Darwin (about evolutionary thinking), as well as of the few more recent reviews on the subject. Here we present, for the first time, the outcome of this review and discuss some of the Muslim schol...

Most evolutionary and medical textbooks state that the tetrapod fore and hindlimb are serial homologues. Here we show how regenerative studies of axolotls, developmental studies of tetrapods, and comparative and evolutionary studies of all major vertebrate groups, including recent re-analyses of the appendicular muscles of chondrichthyans, dipnoans and coelacanths contradict this old dogma. The integrative analysis of the data available strongly supports the idea that the similarity of the muscles and bones of the fore and hindlimbs of tetrapods such as salamanders and modern humans is not due to serial homology, but is instead the result of independent evolutionary changes (homoplasy) occurred mainly during the origin of tetrapods due to the co-option of similar genes for the development of both limbs. It also offers new insights about the ancestral Bauplan and morphogenetic gradients of tetrapod limbs, including the striking similarity of the zeugopodial (forearm/leg) and autopodial (hand/foot) muscles ...

Most human syndromes show a complex mix of symptoms that are not easily explained by a single gene mutation. Complex developmental networks that will be influenced by a mutation need long term stud...

We report the muscular and skeletal abnormalities observed in a very rare and precious 28-week human Trisomy 18 cyclopic fetus, and compare this individual with other humans with Trisomy 18 (Edward...

The notion of scala naturae dates back to thinkers such as Aristotle, who placed plants below animals and ranked the latter along a graded scale of complexity from ‘lower’ to ‘higher’ animals, such as humans. In the last decades, evolutionary biologists have tended to move from one extreme (i.e. the idea of scala naturae or the existence of a general evolutionary trend in complexity from ‘lower’ to “higher” taxa, with Homo sapiens as the end stage) to the other, opposite, extreme (i.e. to avoid using terms such as ‘phylogenetically basal’ and ‘anatomically plesiomorphic’ taxa, which are seen as the undesired vestige of old teleological theories). The latter view tries to avoid any possible connotations with the original anthropocentric idea of a scala naturae

Most textbooks and papers state that the structures of the tetrapod fore- and hindlimb are serial homologues. We provide an updated discussion of this subject based on a literature review and on our regenerative studies of axolotls, developmental studies of tetrapods, and comparative and evolutionary studies of all major vertebrate groups, including recent re-analyses of the appendicular muscles of chondrichthyans, dipnoans and coelacanths. The integrative analysis of the data available strongly supports the idea that the similarity of muscles and bones of the fore and hindlimbs of tetrapods such as salamanders and modern humans is not due to serial homology, but is instead the result of independent evolutionary changes (homoplasy) due to a complex interplay between developmental, functional, topological and phylogenetic constraints. It also offers new insights about the ancestral Bauplan and morphogenetic gradients of tetrapod limbs, including the striking similarity of the zeugopodial (forearm/leg) and ...

The above article, published as an Accepted Article online on December 5, 2014, in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the authors, the journal Editor in Chief, Parker B. Antin, and Wiley Periodicals, Inc. The retraction has been agreed due to an error at the publishers, which resulted in a preliminary draft of the article being posted online. The correct article, ‘Development, metamorphosis, morphology and diversity: the evolution of chordate muscles and the origin of vertebrates’ by Rui Diogo and Janine M. Ziermann, was published online on December 22, 2014, doi: 10.1002/dvdy.24245. References Diogo R, Ziermann JM. 2014. Development, Metamorphosis, Morphology and Diversity: The Evolution of Chordate muscles and the Origin of Vertebrates. Dev. Dyn., 10.1002/dvdy.24236 Diogo R, Ziermann JM. 2014. Development, Metamorphosis, Morphology and Diversity: The Evolution of Chordate muscles and the Origin of Vertebrates. Dev. Dyn., 10.1002/dvdy.24245