George Lyras

CYNOTHERIUM SARDOUS, AN INSULAR CANID (MAMMALIA: CARNIVORA) FROM THE PLEISTOCENE OF SARDINIA (ITALY), AND ITS ORIGIN

Abstract The endemic insular canid Cynotherium sardous has been known for 1 ½ centuries, yet its phylogenetic position remained unsolved. This was because inherited ancestral characters and acquired adaptations to different ecological pressures could not be separated. In this study the problem is approached again, with the use of morphological features that were either overlooked or could not be explained properly, combined with results from recent major revisions of canid phylogeny. It appears that Xenocyon is the ancestor of Cynotherium, and that this large hypercarnivorous canid, once on the island, faced a rather different menu consisting of small prey only. The subsequent necessary adaptation resulted in a smallsized dog whose dentition remained much the same, whereas its skull lost the typical fortifications seen in the other hypercarnivorous canids; these are considered superfluous for Cynotherium, which had to exchange big and strong prey for small and fast prey.

Long‐term effects of autoimmune CNS inflammation on adult hippocampal neurogenesis

Neurogenesis is a well‐characterized phenomenon within the dentate gyrus (DG) of the adult hippocampus. Aging and chronic degenerative disorders have been shown to impair hippocampal neurogenesis, but the consequence of chronic inflammation remains controversial. In this study the chronic experimental autoimmune encephalomyelitis (EAE) mouse model of multiple sclerosis was used to investigate the long‐term effects of T cell–mediated central nervous system inflammation on hippocampal neurogenesis. 5‐Bromodeoxyuridine (BrdU)‐labeled subpopulations of hippocampal cells in EAE and control mice (coexpressing GFAP, doublecortin, NeuN, calretinin, and S100) were quantified at the recovery phase, 21 days after BrdU administration, to estimate alterations on the rate and differentiation pattern of the neurogenesis process. The core features of EAE mice DG are (i) elevated number of newborn (BrdU+) cells indicating vigorous proliferation, which in the long term subsided; (ii) enhanced migration of newborn cells into the granule cell layer; (iii) increased level of immature neuronal markers (including calretinin and doublecortin); (iv) trending decrease in the percentage of newborn mature neurons; and (v) augmented gliogenesis and differentiation of newborn neural precursor cells (NPCs) to mature astrocytes (BrdU+/S100+). Although the inflammatory environment in the brain of EAE mice enhances the proliferation of hippocampal NPCs, in the long term neurogenesis is progressively depleted, giving prominence to gliogenesis. The discrepancy between the high number of immature cells and the low number of mature newborn cells could be the result of a caused defect in the maturation pathway.

Mortality in a predator-free insular environment:the dwarf deer of Crete

ABSTRACT Age-graded fossils of Pleistocene endemic Cretan deer (Candiacervus spp.) reveal unexpectedly high juvenile mortality similar to that reported for extant mainland ruminants, despite the fact that these deer lived in a predator-free environment and became extinct before any plausible date for human arrival. Age profiles show that deer surviving past the fawn stage were relatively long-lived for ruminants, indicating that high juvenile mortality was not an expression of their living a “fast” life. Although the effects on survivorship of such variables as fatal accidents, starvation, and disease are difficult to gauge in extinct taxa, the presence of extreme morphological variability within nominal species/ecomorphs of Candiacervus is consistent with the view that high juvenile mortality can function as a key innovation permitting rapid adaptation in insular contexts.

Earliest known hominin activity in the Philippines by 709 thousand years ago

Over 60 years ago, stone tools and remains of megafauna were discovered on the Southeast Asian islands of Flores, Sulawesi and Luzon, and a Middle Pleistocene colonization by Homo erectus was initially proposed to have occurred on these islands1–4. However, until the discovery of Homo floresiensis in 2003, claims of the presence of archaic hominins on Wallacean islands were hypothetical owing to the absence of in situ fossils and/or stone artefacts that were excavated from well-documented stratigraphic contexts, or because secure numerical dating methods of these sites were lacking. As a consequence, these claims were generally treated with scepticism5. Here we describe the results of recent excavations at Kalinga in the Cagayan Valley of northern Luzon in the Philippines that have yielded 57 stone tools associated with an almost-complete disarticulated skeleton of Rhinoceros philippinensis, which shows clear signs of butchery, together with other fossil fauna remains attributed to stegodon, Philippine brown deer, freshwater turtle and monitor lizard. All finds originate from a clay-rich bone bed that was dated to between 777 and 631 thousand years ago using electron-spin resonance methods that were applied to tooth enamel and fluvial quartz. This evidence pushes back the proven period of colonization6 of the Philippines by hundreds of thousands of years, and furthermore suggests that early overseas dispersal in Island South East Asia by premodern hominins took place several times during the Early and Middle Pleistocene stages1–4. The Philippines therefore may have had a central role in southward movements into Wallacea, not only of Pleistocene megafauna7, but also of archaic hominins.Stone tools and a disarticulated and butchered skeleton of Rhinoceros philippinensis, found in a securely dated stratigraphic context, indicate the presence of an unknown hominin population in the Philippines as early as 709 thousand years ago.

Evolution of Gyrification in Carnivores

The order Carnivora is a large and highly diverse mammalian group with a long and well-documented evolutionary history. Nevertheless, our knowledge on the degree of cortical folding (or degree of gyrification) is limited to just a few species. Here we investigate the degree of cortical folding in 64 contemporary and 37 fossil carnivore species. We do so by measuring the length of gyri impressions on endocranial casts. We use this approach because we have found that there is a very good correlation between the degree of cortical folding and the relative length of the gyri that are exposed on the outer surface of the hemispheres. Our results indicate that aquatic and semiaquatic carnivores have higher degrees of cortical folding than terrestrial carnivores. The degree of cortical folding varies among modern families, with viverrids having the lowest values. Furthermore, the scaling of cortical folding with brain size follows different patterns across specific carnivore families. Forty million years ago, the first carnivores had a relatively small cortex and limited cortical folding. Both the size of the cortex and the degree of cortical folding increased independently in each family during evolution.

‘On being the right size’ - Do aliens follow the rules?

Editor: Kostas Triantis Abstract Aim: To assess whether mammalian species introduced onto islands across the globe have evolved to exhibit body size patterns consistent with the ‘island rule,’, and to test an ecological explanation for body size evolution of insular mammals. Location: Islands worldwide. Methods: We assembled data on body mass, geographical characteristics (latitude, maximum elevation) and ecological communities (number of mammalian competitors, predators and prey) for 385 introduced populations across 285 islands, comprising 56 species of extant, non-volant mammals. We used linear regression, ANCOVA and regression tree analyses to test whether introduced populations of mammals exhibit the island rule pattern, whether the degree of body size change increased with time in isolation and whether residual variation about the general trend can be attributed to the geographical and ecological characteristics of the islands. Results: Introduced populations follow the predicted island rule trend, with body size shifts more pronounced for populations with greater residence times on the islands. Small mammals evolved to larger body sizes in lower latitudes and on islands with limited topographic relief. Consistent with our hypothesis on the ecology of evolution, body size of insular introduced populations was influenced by co-occurring species of mammalian competitors, predators and prey. Conclusion: The island rule is a pervasive pattern, exhibited across a broad span of geographical regions, taxa, time periods and, as evidenced here, for introduced as well as native mammals. Time in isolation impacts body size evolution profoundly. Body size shift of introduced mammals was much more pronounced with increasing residence times, yet far less than that exhibited by native, palaeo-insular mammals (residence times > 10,000 years). Given the antiquity of many species introductions, it appears that much of what we view as the natural character and ecological dynamics of recent insular communities may have been rendered artefacts of ancient colonizations by humans and commensals.

From Jumbo to Dumbo: Cranial Shape Changes in Elephants and Hippos During Phyletic Dwarfing

Members of the mammalian families Elephantidae and Hippopotamidae (extant and extinct elephants and hippos) include extinct dwarf species that display up to 98% decrease in body size compared to probable ancestral sources. In addition to differences in body mass, skulls of these species consistently display distinctive morphological changes, including major reduction of pneumatised areas in dwarf elephants and shortened muzzles in dwarf hippos. Here we build on previous studies of island dwarf species by conducting a geometric morphometric analysis of skull morphology and allometry in target taxa, living and extinct, and elaborate on the relation between skull size and body size. Our analysis indicates that skull size and body size within terrestrial placental mammals scale almost isometrically (PGLS major axis slope 0.906). Furthermore, skull shape in dwarf species differed from both their ancestors and the juveniles of extant species. In insular dwarf hippos, the skull was subject to considerable anatomical reorganisation in response to distinct selection pressures affecting early ontogeny (the “island syndrome”). By contrast, skull shape in adult insular dwarf elephants can be explained well by allometric effects; selection on size may thus have been the main driver of skull shape in dwarf elephants. We suggest that a tightly constrained growth trajectory, without major anatomical reorganization of the skull, allowed for flexible adaptations to changing environments and was one of the factors underlying the evolutionary success of insular dwarf elephants.

Bone lesions in a Late Pleistocene assemblage of the insular deer Candiacervus sp.II from Liko cave (Crete, Greece)

Candiacervus sp.II is one of the deer species that inhabited the island of Crete during the Late Pleistocene. The species evolved on the island under a prolonged period of isolation and, as a consequence, developed a high degree of endemism. Fossils of this species have been discovered at many Cretan sites, including Liko cave (an attritional accumulation of several thousand fossils). In this paper, we present the results of a systematic analysis of the prevalence and anatomical distribution of bone lesions of Candiacervus sp.II, from that cave. We identified one metapodial with a healed fracture and nine (various) specimens with moderate to severe degenerative lesions of osteoarthritis. The lesions were evaluated macroscopically and radiographically, and they were classified as traumatic or degenerative. Degenerative lesions that affected adult individuals had prevalence rates below 5% and were attributed to environmental or nutritional causes. Representative bones were sampled for histological evaluation, to provide essential baseline data on possible underlying disorders. The aims of this study are to provide evidence for bone disease contributing to species morbidity, and to shed new light on causes and potential palaeoecological significance.

Morphology of articular surfaces can solve aphylogenetic issue: one instead of two ancestors for Candiacervus (Mammalia: Cervoidea)

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Microcephaly in ancient Greece—the "Minoan" microcephalus of Zakros

Dear Editor, We appreciate the interest manifested by Dr. Syrmos for the published works on the “Minoan microcephalus of Zakros” [1]. The author reviewed several papers on this subject including our own. However, we would like to urge caution against the misconception that the microcephalic from Crete would belong to the species Homo floresiensis, an entirely different species than Homo sapiens to which the Cretan microcephalus naturally belongs. H. floresiensis is a fossil hominid which lived on the Indonesian island of Flores and that went extinct around 12,000 BCE [2]. The Cretan microcephalus, on the other hand, neither is a fossil human nor originates from Flores. There is no scientist who suggested a connection between the two islands as seems to be suggested by the author. Modern Cretans all belong to H. sapiens and so did the inhabitants of Crete during the proto-historical times. The author seems to have overlooked the fact that the papers he cited used the Cretan microcephalus in their studies on H. floresiensis to test the hypothesis that the fossil human from Flores suffered from a form of microcephaly or another neurodevelopmental disorder. Furthermore, although the microcephalic individual from Cave Malakari on Crete is often referred to as “Minoan”, in reality, it belongs to the Protogeometric period, dated at about 3,000 BP [3, 4]. His burial and the excellent status of his dentition suggest that he was subject to a special treatment, considering the generally bad condition of adult dentition of contemporary individuals. Therefore, further research on this particular specimen might reveal interesting insights into the treatment of microcephalic children in protohistoric societies.