On the development of the chondrocranium and the histological anatomy of the head in perinatal stages of marsupial mammals

An overview of the literature on the chondrocranium of marsupial mammals reveals a relative conservatism in shape and structures. We document the histological cranial anatomy of individuals representing Monodelphis domestica, Dromiciops gliroides, Perameles sp. and Macropus eugenii. The marsupial chondrocranium is generally characterized by the great breadth of the lamina basalis, absence of pila metoptica and large otic capsules. Its most anterior portion (cupula nasi anterior) is robust, and anterior to it there are well-developed tactile sensory structures, functionally important in the neonate. Investigations of ossification centers at and around the nasal septum are needed to trace the presence of certain bones (e.g., mesethmoid, parasphenoid) across marsupial taxa. In many adult marsupials, the tympanic floor is formed by at least three bones: alisphenoid (alisphenoid tympanic process), ectotympanic and petrosal (rostral and caudal tympanic processes); the squamosal also contributes in some diprotodontians. The presence of an entotympanic in marsupials has not been convincingly demonstrated. The tubal element surrounding the auditory tube in most marsupials is fibrous connective tissue rather than cartilage; the latter is the case in most placentals recorded to date. However, we detected fibrocartilage in a late juvenile of Dromiciops, and a similar tissue has been reported for Tarsipes. Contradictory reports on the presence of the tegmen tympani can be found in the literature. We describe a small tegmen tympani in Macropus. Several heterochronic shifts in the timing of development of the chondocranium and associated structures (e.g., nerves, muscles) and in the ossification sequence have been interpreted as largely being influenced by functional requirements related to the altriciality of the newborn marsupial during early postnatal life. Comparative studies of chondocranial development of mammals can benefit from a solid phylogenetic framework, research on non-classical model organisms, and integration with imaging and sectional data derived from computer-tomography.Fil: Sánchez Villagra, Marcelo R.. Universitat Zurich; SuizaFil: Forasiepi, Analia Marta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentin

In the spotlight—Established researcher

With whom and where did you study? My undergraduate study in Biology was at Universidad Simón Bolívar in Caracas. After a year of fieldwork and diverse laboratory experiences, I went for a PhD at Duke University, with a thesis on marsupial mammal cranial development and evolution. I had two coadvisors: Kathleen Smith (comparative ontogenetics) and Richard Kay (paleontological work). This was followed by my Habilitation under my mentor Wolfgang Maier in Tübingen (Germany), where I worked on diverse topics of mammalian ontogeny and learned to teach on the comparative anatomy of diverse Deuterostomia groups. During my job at the Natural History Museum in London, I learned about modularity from hosting Anjali Goswami as a postdoc; from many paleontologists there and in Zurich I was inspired to contribute to “developmental paleontology.” What got you interested in biology? When did you know EvoDevo was for you? I came to Biology with a fascination for exploring the natural world; evolution provided an explanation to my questions on origins. My first interest was in reconstructing evolutionary trees, and for that solving homology questions required the ontogenetic perspective. Exposure to EvoDevo ideas came from readings at graduate school at Duke on the neural crest, heterochrony, evolutionary novelties, and others—there I learned that EvoDevo was not just about Hox genes, and I became inspired by Pere Alberch's papers. I started to use the sequence heterochrony approach following the work of Kathleen Smith, Mike Richardson, and others, as this allowed me to examine developmental evolution with a comparative approach that did not require perfectly timed series and thus could be more inclusive in taxonomic sampling. When I learned about palaeohistology from my then postdoc Torsten Scheyer in Zurich, I realized that one could directly address matters of growth and life history in fossils, in addition to an approach based on phylogenetic bracket considerations. For my work on animal domestication, I saw the chance to bring a comparative ontogenetic perspective, and here the insights gained on neural crest development by detailed experimental studies in the work of Rich Schneider and others inform much of what we discussed about patterns of morphological diversification. What do you see as the major challenges of EvoDevo? I hope that EvoDevo embraces genuinely comparative ontogenetic research as a part of it, and that technological advances continue to contribute with discoveries but do not determine what can be funded or published, as EvoDevo remains a question-driven discipline as opposed to one driven by methods. Macroevolutionary questions that can be addressed only from a developmental perspective should continue to be part of a broad and pluralistic EvoDevo, as well as the explanation of phenotypic variation among populations within a species. I imagine that the examination of neglected groups of organisms or of organ systems will provide unanticipated insights on the amazing variation in developmental evolution. It will be a challenge for the EvoDevo community to be inclusive in that it can be practiced by people across the world given the differential access to resources. Maybe some of the research in Eco-EvoDevo will serve to better understand environmental issues faced by humanity, but I suspect it is more likely that EvoDevo will be more about satisfying human intellectual curiosity

Claude Lévi-Strauss as a humanist forerunner of cultural macroevolution studies

Cross-cultural studies of humans using methods developed in evolutionary biology and comparative linguistics are flourishing. ‘Cultural macroevolution’ has great potential to address fundamental questions of cultural transformation and human history. However, this field is poorly integrated with core cultural anthropology, although both aim in part at addressing similar issues. Claude Lévi-Strauss established a comparative approach searching for universals and documentation of diversity to bring understanding to cultural phenomena. Recognizing the nomothetic nature of Lévi-Strauss’ work, his abstraction and modelling, provides an example within anthropology of the search for universals and the study of big data, akin to cultural macroevolution studies. The latter could benefit, beyond the sophisticated analyses of big data mined from ethnographic work, from the integration with the intellectual legacy and practice of core anthropology and thus propitiate the synergistic interaction of disciplines. Attempts at rapprochement of disciplines from the natural sciences that lack pluralism and present a narrow view are deemed examples of ‘Wilson's effect’

A new Megatheriinae skull (Xenarthra, Tardigrada) from the pliocene of northern venezuela – Implications for a giant sloth dispersal to central and North America

A skull of a ground sloth from the Pliocene San Gregorio Formation documents a northern neotropical occurrence of a megatheriine that addresses issues on intraspecific variation and biogeography. The new specimen is broadly similar in size and morphology to that of Proeremotherium eljebe from the underlying Codore Formation in the Urumaco Sequence, differing in several features such as a longer basicranial area and a more posteriorly projected basioccipital between the condyles. The living sloths species of Bradypus and Choloepus do not have unequivocal anatomical features that indicate sexual dimorphism. Nevertheless, fossil sloths may have shown such dimorphism, and speculations on this subject are part of the considerations that can be made when allocating fragmentary fossils (e.g., in the new skull the presence of a long sagittal crest could indicate a male individual and the absence of an extended crest in Proeremotherium eljebe a female one). We speculate that as early as the late middle Miocene, two main lines of Megatheriinae had clearly separated in two geographic areas, one in the rising Andean area and one at low latitudes on the lowlands of central and northern South America.Fil: Carlini, Alfredo Armando. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Departamento Científico de Paleontología de Vertebrados; ArgentinaFil: Brandoni, Diego. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; ArgentinaFil: Sánchez, Rodolfo. Museo Paleontológico de la Alcaldia de Urumaco; VenezuelaFil: Sánchez Villagra, Marcelo R.. Universitat Zurich; Suiz

Timing of organogenesis support basal position of turtles in the amniote tree of life

Background: The phylogenetic position of turtles is the most disputed aspect in the reconstruction of the land vertebrate tree of life. This controversy has arisen after many different kinds and revisions of investigations of molecular and morphological data. Three main hypotheses of living sister-groups of turtles have resulted from them: all reptiles, crocodiles + birds or squamates + tuatara. Although embryology has played a major role in morphological studies of vertebrate phylogeny, data on developmental timing have never been examined to explore and test the alternative phylogenetic hypotheses. We conducted a comprehensive study of published and new embryological data comprising 15 turtle and eight tetrapod species belonging to other taxa, integrating for the first time data on the side-necked turtle clade. Results: The timing of events in organogenesis of diverse character complexes in all body regions is not uniform across amniotes and can be analysed using a parsimony-based method. Changes in the relative timing of particular events diagnose many clades of amniotes and include a phylogenetic signal. A basal position of turtles to the living saurian clades is clearly supported by timing of organogenesis data. Conclusion: The clear signal of a basal position of turtles provided by heterochronic data implies significant convergence in either molecular, adult morphological or developmental timing characters, as only one of the alternative solutions to the phylogenetic conundrum can be right. The development of a standard reference series of embryological events in amniotes as presented here should enable future improvements and expansion of sampling and thus the examination of other hypotheses about phylogeny and patterns of the evolution of land vertebrate development

A new Megatheriinae skull (Xenarthra, Tardigrada) from the pliocene of northern Venezuela : Implications for a giant sloth dispersal to central and North America

A skull of a ground sloth from the Pliocene San Gregorio Formation documents a northern neotropical occurrence of a megatheriine that addresses issues on intraspecific variation and biogeography. The new specimen is broadly similar in size and morphology to that of Proeremotherium eljebe from the underlying Codore Formation in the Urumaco Sequence, differing in several features such as a longer basicranial area and a more posteriorly projected basioccipital between the condyles. The living sloths species of Bradypus and Choloepus do not have unequivocal anatomical features that indicate sexual dimorphism. Nevertheless, fossil sloths may have shown such dimorphism, and speculations on this subject are part of the considerations that can be made when allocating fragmentary fossils (e.g., in the new skull the presence of a long sagittal crest could indicate a male individual and the absence of an extended crest in Proeremotherium eljebe a female one). We speculate that as early as the late middle Miocene, two main lines of Megatheriinae had clearly separated in two geographic areas, one in the rising Andean area and one at low latitudes on the lowlands of central and northern South America.Facultad de Ciencias Naturales y Muse

Aceptación final 25 abril

ABSTRACT: The ontogenetic changes of the skeletal tissue of the vestibular and cochlear system of Caluromys philander were investigated using CT scans of an adult skull and 3D reconstructions of histological serial sections of three pouch-youngs. The bony labyrinth of C. philander differs in several aspects from what has been reported for other marsupials. Some of the proportions of the semicircular canals (SC) are probably characteristic of arboreal as opposed to terrestrial species. Several significant changes in the SCs shape occur postnatally. The most remarkable difference among stages is the different height of the anterior SC and posterior SC in relation to the common crus. In the adult the posterior arm of the lateral SC and the inferior arm of the posterior SC build a common crus, a condition of several basal metatherians and crown-group marsupials. The number of turns of the cochlea in the adult is 2.4. RESUMEN: Anatomía y desarrollo de los huesos del oído interno de Caluromys philander (Didelphimorphia, Marsupialia). Los cambios ontogenéticos en el esqueleto asociado al aparato vestibular y la cochlea de Caluromys philander fueron investigados usando CT scans de un cráneo adulto y reconstrucciones 3D de cortes histológicos de tres estadíos tempranos postnatales. El laberinto óseo de C. philander difiere en varios aspectos del de otros marsupiales. Algunas de las proporciones de los canales semircirculares (CS) son probablemente características para hábitos arborícolas. Varios cambios significativos en los CSs ocurren luego del nacimiento. La diferencia más notable entre estadíos es la altura diferente del CS anterior y posterior en relación con el 'common crus'. En el adulto el brazo posterior del CS lateral y el brazo inferior del CS posterior forman un 'common crus', una condición característica de varias especies basales de marsupiales. El número de vueltas de la cochlea en el adulto es 2.4

Similar rates of morphological evolution in domesticated and wild pigs and dogs.

BACKGROUND: Whether the great morphological disparity of domesticated forms is the result of uniformly higher evolutionary rates compared to the wild populations is debated. We provide new data on changes of skull dimensions within historical time periods in wild and domesticated dogs and pigs to test if domestication might lead to an accelerated tempo of evolution in comparison to the wild conspecifics. Darwins and Haldanes were used to quantify evolutionary rates. Comparisons with evolutionary rates in other species and concerning other characteristics from the literature were conducted. RESULTS: Newly gathered and literature data show that most skull dimensions do not change faster in domesticated breeds than in wild populations, although it is well known that there is extensive artificial selection on skull shape in some dog breeds. Evolutionary rates among domesticated forms and traits (e.g., production traits in pigs, and racing speed in some horses and greyhounds) might vary greatly with species and breeding aim. CONCLUSIONS: Our study shows that evolutionary rates in domestication are not in any event faster than those in the wild, although they are often perceived as such given the vast changes that appear in a relatively short period of time. This may imply that evolution under natural conditions - i.e., without human intervention - is not as slow as previously described, for example by Darwin. On the other hand, our results illustrate how diverse domestication is in tempo, mode, and processes involved