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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.

Understanding feeding ecology of extinct kangaroos is fundamental to understanding the evolution of kangaroos and the Australia paleoenvironment during the Oligo-Miocene. Comparisons with extant species have suggested that the macropodiforms of the Oligo/Miocene (kangaroos and allies) from the Riversleigh World Heritage Area, northern Australia, were predominantly folivorous browsers or fungivores, unlike the majority of extant species. To further test this hypothesis, we investigate the relationship between variation in cranial and mandibular shape of extant and extinct macropodiforms and ecological factors such as diet, locomotion, and body mass using 3D geometric morphometric analysis of 42 living species and eight extinct species from two radiations (the extinct clade of Balbaridae and some early representatives of the extant Macropodidae. Dietary class (fungivore, browser, grazer, and mixed feeder) correlated strongly with variation in cranial shape (20–25% of variance explained). There was also significant association between cranial shape, and both locomotor mode and body mass. In a principal component analysis of shape variation for crania (including the shape of the molar row), Riversleigh macropodiforms cluster with extant folivorous browsers on principal components (PC) 1 and 3, providing support for previous interpretations of these species as browsing kangaroos. However, as a group and regardless of phylogenetic association, the shape centroid of extinct species differs significantly from that of extant species. Riversleigh macropodiforms cluster with regular hoppers or arboreal tree kangaroos, but this may be a result of the correlation between diet and locomotor mode in kangaroos. Their similarity to extant browsers supports previous interpretations of rainforest and woodland environments at Riversleigh during the early and middle Miocene, respectively. Procrustes ANOVA Analysis of the full shape dataset and diet also shows that diet accounts for a significant portion of variation; however, when phylogeny is taken into account these results become nonsignificant. In analyses of dentary shape, some balbarid species cluster with extant mixed feeders, although this may reflect phylogenetic differences rather than ecological signal.

Background Self-powered flight is one of the most energy-intensive types of locomotion found in vertebrates. It is also associated with a range of extreme morpho-physiological adaptations that evolved independently in three different vertebrate groups. Considering that development acts as a bridge between the genotype and phenotype on which selection acts, studying the ossification of the postcranium can potentially illuminate our understanding of bat flight evolution. However, the ontogenetic basis of vertebrate flight remains largely understudied. Advances in quantitative analysis of sequence heterochrony and morphogenetic growth have created novel approaches to study the developmental basis of diversification and the evolvability of skeletal morphogenesis. Assessing the presence of ontogenetic disparity, integration and modularity from an evolutionary approach allows assessing whether flight may have resulted in evolutionary differences in the magnitude and mode of development in bats. Results We quantitatively compared the prenatal ossification of the postcranium (24 bones) between bats (14 species), non-volant mammals (11 species) and birds (14 species), combining for the first time prenatal sequence heterochrony and developmental growth data. Sequence heterochrony was found across groups, showing that bat postcranial development shares patterns found in other flying vertebrates but also those in non-volant mammals. In bats, modularity was found as an axial-appendicular partition, resembling a mammalian pattern of developmental modularity and suggesting flight did not repattern prenatal postcranial covariance in bats. Conclusions Combining prenatal data from 14 bat species, this study represents the most comprehensive quantitative analysis of chiropteran ossification to date. Heterochrony between the wing and leg in bats could reflect functional needs of the newborn, rather than ecological aspects of the adult. Bats share similarities with birds in the development of structures involved in flight (i.e. handwing and sternum), suggesting that flight altriciality and early ossification of pedal phalanges and sternum are common across flying vertebrates. These results indicate that the developmental modularity found in bats facilitates intramodular phenotypic diversification of the skeleton. Integration and disparity increased across developmental time in bats. We also found a delay in the ossification of highly adaptable and evolvable regions (e.g. handwing and sternum) that are directly associated with flight performance. Electronic supplementary material The online version of this article (10.1186/s12862-019-1396-1) contains supplementary material, which is available to authorized users.

A new early Eocene bat species is described from the Paris Basin locality of Pourcy (Marne), which is thought to represent either MP7 (early Ypresian; earliest Eocene) or MP8 + 9 (middle Ypresian; later early Eocene) in the European Paleogene mammal chronostratigraphic scale. It is the first bat described from the Pourcy locality, and one of the world’s oldest chiropterans. The new bat shares a number of archaic dental features found in other early bats, but also exhibits several traits that appear derived and suggest referral to the family Onychonycteridae. Onychonycterids are restricted to the Ypresian of France, Belgium, England, and the USA, and include the most skeletally primitive of bats. Onychonycterids lived alongside bats that exhibit adaptations for more advanced flight capabilities but which had dentitions that were somewhat more similar to those of ancestral placental mammals. The new bat species from Pourcy, together with other Ypresian chiropterans, illustrates the mosaic nature of bat evolution in the early Eocene.

Peramelemorphians (bandicoots and bilbies) are unique among mammals in having the shortest gestation period. Very little is known about their evolutionary history primarily because until recently their fossil record was scarce. Here we describe two new species, Madju variae, gen. et sp. nov., from late Oligocene to middle Miocene deposits from the Riversleigh World Heritage Area, Queensland, and the Kutjamarpu Local Fauna, South Australia, and Madju encorensis, gen. et sp. nov., also from Riversleigh WHA but from the late middle to early late Miocene. Phylogenetic analysis suggests that they are best regarded as basal members of the Superfamily Perameloidea. Species of Madju are unusual in showing a distinct reduction in size through time, possibly reflecting environmental change from the early to late Miocene. Madju variae is the first-known sexually dimorphic fossil peramelemorphian. The preservation and representation of specimens of M. variae is exceptional, enabling documentation of ontogenetic development from juvenile to old adult stage suggesting that juveniles of M. variae developed more slowly than their modern counterparts and that lactation lasted for a longer time. If so, the short gestation of modern peramelemorphians would appear to be a specialisation that might have evolved sometime after the middle Miocene.

UNTIL now, the egg-laying monotremes were only known from the Australian continent, where they have lived since the early Cretaceous period to the present1. Here we report the first monotreme from outside the Australian continent, an ornithorhyn-chid, from sediments of late early Palaeocene age in Patagonia, southern Argentina. This discovery demonstrates the Gondwanan nature of monotremes and supports the hypothesis that the Patagonian Terrane of southern South America had a biotic history distinct from that of the rest of the continent.