Bats are among the most recognizable, numerous, and widespread of all mammals. But much of their fossil record is missing, and bat origins remain poorly understood, as do the relationships of early ...to modern bats. Here, we describe a new early Eocene bat that helps bridge the gap between archaic stem bats and the hyperdiverse modern bat radiation of more than 1,460 living species. Recovered from ∼50 million-year-old cave sediments in the Quercy Phosphorites of southwestern France, Vielasia sigei's remains include a near-complete, three-dimensionally preserved skull-the oldest uncrushed bat cranium yet found. Phylogenetic analyses of a 2,665 craniodental character matrix, with and without 36.8 kb of DNA sequence data, place Vielasia outside modern bats, with total evidence tip-dating placing it sister to the crown clade. Vielasia retains the archaic dentition and skeletal features typical of early Eocene bats, but its inner ear shows specializations found in modern echolocating bats. These features, which include a petrosal only loosely attached to the basicranium, an expanded cochlea representing ∼25% basicranial width, and a long basilar membrane, collectively suggest that the kind of laryngeal echolocation used by most modern bats predates the crown radiation. At least 23 individuals of V. sigei are preserved together in a limestone cave deposit, indicating that cave roosting behavior had evolved in bats by the end of the early Eocene; this period saw the beginning of significant global climate cooling that may have been an evolutionary driver for bats to first congregate in caves.
A new Old World trident bat (Rhinonycteridae) is described from an early Miocene cave deposit in the Riversleigh World Heritage Area, northwestern Queensland, Australia. Living rhinonycterids ...comprise a small family of insect‐eating, nasal‐emitting rhinolophoid bats from Africa, Madagascar, Seychelles, the Middle East, and northern Australia. The new fossil species is one of at least 12 rhinonycterid species known from the Oligo‐Miocene cave deposits at Riversleigh. We refer the new species to the genus Xenorhinos (Hand, Journal of Vertebrate Paleontology, 18, 430–439, 1998a) because it shares a number of unusual cranial features with the type and only other species of the genus, X. halli, including a broad rostrum, very wide interorbital region, pronounced ventral flexion of the rostrum, very constricted sphenoidal bridge, and, within the nasal fossa, reduced bony division, and relatively well developed turbinals. Xenorhinos species lived in northern Australia during the global Miocene Climatic Optimum, in closed wet forests, unlike the drier habitats that trident bats largely inhabit today. Our phylogenetic analysis suggests that more than one dispersal event gave rise to the Australian rhinonycterid radiation, with two lineages having sister‐group relationships with non‐Australian taxa.
The relatively high level of morphological diversity in Australasian marsupials compared to that observed among American marsupials remains poorly understood. We undertake a comprehensive ...macroevolutionary analysis of ontogenetic allometry of American and Australasian marsupials to examine whether the contrasting levels of morphological diversity in these groups are reflected in their patterns of allometric evolution. We collate ontogenetic series for 62 species and 18 families of marsupials (n = 2091 specimens), spanning across extant marsupial diversity. Our results demonstrate significant lability of ontogenetic allometric trajectories among American and Australasian marsupials, yet a phylogenetically structured pattern of allometric evolution is preserved. Here we show that species diverging more than 65 million years ago converge in their patterns of ontogenetic allometry under animalivorous and herbivorous diets, and that Australasian marsupials do not show significantly greater variation in patterns of ontogenetic allometry than their American counterparts, despite displaying greater magnitudes of extant ecomorphological diversity.
Abstract
Anurans including frogs and toads exhibit an ilium that is often regarded as taxonomically diagnostic. The ilium, one of the three paired bones that make up the pelvic girdle, has been ...important in the fossil record for identifying anuran morphotypes. Osteological collections for Australian frogs are rare in herpetological museums, and skeletonizing whole‐bodied specimens requires destroying soft tissue morphology which is valuable to anuran specialists working on living species. Computed tomography scans provide the opportunity to study anuran osteology without the loss of soft tissues. Our study, based on microcomputed tomography scans of extant Australian frogs from the public repository Morphosource and from museum collections focuses on the morphological differences between Australian frogs at the familial and generic levels using geometric morphometrics to compare the diagnostic shape of the ilium. Principal component analysis (PCA) and canonical variate analysis (CVA) were conducted to assess differences in the ilium between supraspecific groups of Australian frogs. The canonical variates analysis accurately predicted group membership (i.e., the correct family) with up to 76.2% success for cross‐validated predictions and 100% of original group predictions. While the sample was limited to familial and generic level analyses, our research shows that ilial morphology in Australian frogs is taxonomically informative. This research provides a guide for identifying Australian anurans, including fossils, as well as new information relevant to considerations about their phylogenetic relationships, and the potential use of the fossil record to enhance efforts to conserve threatened living frog species.
Despite the recognition that bone histology provides much information about the life history and biology of extinct animals, osteohistology of extinct marsupials is sorely lacking. We studied the ...bone histology of the ca. 15-million-year-old Nimbadon lavarackorum from Australia to obtain insight into its biology. The histology of thin sections of five femora and five tibiae of juveniles, subadult, and adult Nimbadon lavarackorum was studied. Growth marks in the bones suggest that N. lavarackorum took at least 7–8 years (and likely longer) to reach skeletal maturity. The predominant bone tissue during early ontogeny is parallel-fibered bone, whereas an even slower rate of bone formation is indicated by the presence of lamellar bone tissue in the periosteal parts of the compacta in older individuals. Deposition of bone was interrupted periodically by lines of arrested growth or annuli. This cyclical growth strategy indicates that growth in N. lavarackorum was affected by the prevailing environmental conditions and available resources, as well as seasonal physiological factors such as decreasing body temperatures and metabolic rates.
Little is known about how the large brains of mammals are accommodated into the dazzling diversity of their skulls. It has been suggested that brain shape is influenced by relative brain size, that ...it evolves or develops according to extrinsic or intrinsic mechanical constraints, and that its shape can provide insights into its proportions and function. Here, we characterize the shape variation among 84 marsupial cranial endocasts of 57 species including fossils, using three-dimensional geometric morphometrics and virtual dissections. Statistical shape analysis revealed four main patterns: over half of endocast shape variation ranges from elongate and straight to globular and inclined; little allometric variation with respect to centroid size, and none for relative volume; no association between locomotion and endocast shape; limited association between endocast shape and previously published histological cortex volumes. Fossil species tend to have smaller cerebral hemispheres. We find divergent endocast shapes in closely related species and within species, and diverse morphologies superimposed over the main variation. An evolutionarily and individually malleable brain with a fundamental tendency to arrange into a spectrum of elongate-to-globular shapes—possibly mostly independent of brain function—may explain the accommodation of brains within the enormous diversity of mammalian skull form.
The New Zealand endemic bat family Mystacinidae comprises just two Recent species referred to a single genus, Mystacina. The family was once more diverse and widespread, with an additional six ...extinct taxa recorded from Australia and New Zealand. Here, a new mystacinid is described from the early Miocene (19-16 Ma) St Bathans Fauna of Central Otago, South Island, New Zealand. It is the first pre-Pleistocene record of the modern genus and it extends the evolutionary history of Mystacina back at least 16 million years. Extant Mystacina species occupy old-growth rainforest and are semi-terrestrial with an exceptionally broad omnivorous diet. The majority of the plants inhabited, pollinated, dispersed or eaten by modern Mystacina were well-established in southern New Zealand in the early Miocene, based on the fossil record from sites at or near where the bat fossils are found. Similarly, many of the arthropod prey of living Mystacina are recorded as fossils in the same area. Although none of the Miocene plant and arthropod species is extant, most are closely related to modern taxa, demonstrating potentially long-standing ecological associations with Mystacina.
Diet has been linked to the diversification of the bat superfamily Noctilionoidea, a group that underwent an impressive ecological diversification within Mammalia. For decades, studies have explored ...morphological adaptations and diversity of noctilionoid bats to reveal traits associated with their ecological diversity. Surprisingly, despite such interest and recent application of novel techniques, ecomorphological studies have failed to fully resolve the link between diet and a critical component of the feeding apparatus: dental morphology. Using multivariate dental topographic analysis and phylogenetic comparative methods, we examined the phylogenetic, biological and ecological signal in the dental morphology of noctilionoid bats. Analysing the lower first molars of 110 species, we explored relationships between diet and dental morphology, accounting for three different dimensions of diet (guild, composition, and breadth). Phylogenetic and size-dependent structuring of the dental topography data shows it does not correlate only to diet, highlighting the need to account for multiple sources of variation. Nectarivores showed reduced molar crown height and steepness, whereas animalivorous species had larger molars. Dietary composition suggested that the intensity of exploitation of a resource is also linked to different dimensions of dental morphology. Increasing carnivory positively correlated with molar area, whereas increasing frugivory explained the highest proportion of variation in all other variables. Based on dietary breadth, specialist herbivores and specialist animalivores represent extreme morphologies in terms of tooth steepness and crown height. Together, the results suggest that adaptations affecting different attributes of dental morphology likely facilitated the dietary diversity and specialisation found in Noctilionoidea.
A new fossil crocodile, Ultrastenos willisi, is described from a cranium and postcranial materials collected from the Riversleigh World Heritage Area, northwestern Queensland, Australia. The mandible ...displays pronounced anterior constriction, approaching that seen in the extant gharial, Gavialis gangeticus, and false gharial, Tomistoma schlegelii. As such, U. willisi potentially filled the ecomorphological niche associated with longirostry that has been previously unaccounted for in Riversleigh's Oligo-Miocene crocodile fauna. The pronounced constriction and features of the posterior cranium further distinguish U. willisi from all other known crocodiles, including the only reported Australian Oligo-Miocene longirostral crocodile, Harpacochampsa camfieldensis, from Bullock Creek in the Northern Territory. Ultrastenos willisi is recognized as a new genus and species assigned to subfamily Mekosuchinae on the basis of phylogenetic analysis.
New World bats represent over one third of global bat species and encompass the widest adaptive radiation among bats. Modern bat diversity in the Americas resulted from a mixture of migrations and ...colonisations of different taxa throughout the Cenozoic. Traditionally, these taxa are conceived as either South or North American, based on the location of their centres of diversification. To better understand the spatial and temporal processes behind modern biogeographic patterns of New World bat fauna, we investigated phylogenetic diversity (PD) and endemism (PE) for 325 American bat species using distribution maps and a species‐level phylogenetic supertree of bats. Randomisation tests were used to evaluate the statistical significance of our results, and to derive a categorical analysis of neo‐ and palaeo‐endemism (CANAPE) to deconstruct significant endemism into its different components. PD and PE showed different patterns than those previously reported for New World bats based on traditional measures of diversity. We found multiple centres of significant endemism across the New World for most bat families, extending the hypothesis of dual centres of diversification, previously proposed for Emballonuridae, Phyllostomidae and Mormoopidae, to Molossidae and Vespertilionidae. Our results indicate that Central America and southern North America played important roles in the diversification of New World bats, as did the Andes in the diversification of Vespertilionidae in South America.
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