Australasian Marsupials Research Articles

Patterns of ontogenetic evolution across extant marsupials reflect different allometric pathways to ecomorphological diversity

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.

Phylogenetic Relationships of the Strongyloid Nematodes of Australasian Marsupials Based on Mitochondrial Protein Sequences

Australasian marsupials harbour a diverse group of gastrointestinal strongyloid nematodes. These nematodes are currently grouped into two subfamilies, namely the Cloacininae and Phascolostrongylinae. Based on morphological criteria, the Cloacininae and Phascolostrongylinae were defined as monophyletic and placed in the family Cloacinidae, but this has not been supported by molecular data and they are currently placed in the Chabertiidae. Although molecular data (internal transcribed spacers of the nuclear ribosomal RNA genes or mitochondrial protein-coding genes) have been used to verify morphological classifications within the Cloacininae and Phascolostrongylinae, the phylogenetic relationships between the subfamilies have not been rigorously tested. This study determined the phylogenetic relationships of the subfamilies Cloacininae and Phascolostrongylinae using amino acid sequences conceptually translated from the twelve concatenated mitochondrial protein-coding genes. The findings demonstrated that the Cloacininae and Phascolostrongylinae formed a well-supported monophyletic assemblage, consistent with their morphological classification as an independent family, Cloacinidae. Unexpectedly, however, the subfamily Phascolostrongylinae was split into two groups comprising the genera from macropodid hosts (kangaroos and wallabies) and those from vombatid hosts (wombats). Genera of the Cloacininae and Phascolostrongylinae occurring in macropodid hosts were more closely related compared to genera of the Phascolostrongylinae occurring in wombats that formed a sister relationship with the remaining genera from macropods. These findings provide molecular evidence supporting the monophyly of the family Cloacinidae and an alternative hypothesis for the origin of marsupial strongyloid nematodes in vombatid hosts that requires further exploration using molecular approaches and additional samples.

Clinical toxoplasmosis in zoo animals and its management

• Toxoplasmosis in several animal species in zoos is of both clinical and public health importance. • This paper reviews clinical toxoplasmosis in zoo animals. • Strategies to minimize toxoplasmosis in zoo animals are outlined. Infections by the protozoan parasite, Toxoplasma gondii, are widely prevalent in humans and animals worldwide. Toxoplasmosis in several animal species in zoos is of both clinical and public health importance. Among captive animals, T. gondii infections in Australasian marsupials (kangaroos, wallabies), New World non-human primates (squirrel monkeys), certain wild felids (Pallas’ cats), and certain avian species (canaries and finches) can be devastating. Excretion of environmentally resistant oocysts by captive felids can contaminate the zoo environment and can be source of infections for visitors to zoo, zoo personnel, and animals in the zoo. Here, these aspects of T. gondii infections are reviewed, including prevention strategies.

Climbing adaptations, locomotory disparity and ecological convergence in ancient stem 'kangaroos'.

Living kangaroos, wallabies and rat-kangaroos (Macropodoidea) constitute the most ecologically diverse radiation of Australasian marsupials. Indeed, even their hallmark bipedal hopping gait has been variously modified for bounding, walking and climbing. However, the origins of this locomotory adaptability are uncertain because skeletons of the most ancient macropodoids are exceptionally rare. Some of the stratigraphically oldest fossils have been attributed to Balbaridae—a clade of potentially quadrupedal stem macropodoids that became extinct during the late Miocene. Here we undertake the first assessment of balbarid locomotion using two-dimensional geometric morphometrics and a correlative multivariate analysis of linear measurements. We selected the astragalus and pedal digit IV ungual as proxies for primary gait because these elements are preserved in the only articulated balbarid skeleton, as well as some unusual early Miocene balbarid-like remains that resemble the bones of modern tree-kangaroos. Our results show that these fossils manifest character states indicative of contrasting locomotory capabilities. Furthermore, predictive modelling reveals similarities with extant macropodoids that employ either bipedal saltation and/or climbing. We interpret this as evidence for archetypal gait versatility, which probably integrated higher-speed hopping with slower-speed quadrupedal progression and varying degrees of scansoriality as independent specializations for life in forest and woodland settings.

The imprints left by historical contingency on marsupials' life‐history traits

AbstractHistorical contingency may lead to distinct evolutionary imprints in early‐isolated taxonomic groups. Here, we used comparative phylogenetics to unravel biogeographical imprints left by distinct historical contingencies on the evolutionary patterns of life‐history traits of an iconic group, currently separated by ocean‐wide distance: the marsupials. Australasian and New World marsupial communities share a common ancestry but were subjected to different biogeographic histories: while the Australasian community was effectively isolated from other faunas since disruption of land bridges with Antarctica, the evolution of New World marsupials was affected by the Great American Biotic Interchange. Contrary to our expectations, the exuberant diversity of life‐history traits on Australasian marsupials did not exhibit evidence of early bursts of evolution, as expected on adaptive radiations. That surprising result is probably related to the assumptions of the ecological opportunities scenario – sensu Simpson (Tempo and mode in evolution, Columbia University Press, New York, 1994), which are hard to be met in continental scales. On the other hand, New World marsupials showed patterns of evolution consistent with niche conservatism, possibly due to the constraining effect of biotic interactions on niche evolution. Therefore, biotic interactions seem to have the limited evolution of New World life‐history traits, whereas Australasian marsupials diverged into spectacular forms, though in a gradual and constant rate. The distinct biogeographic histories of the New World and Australasian marsupials thus provide a unifying explanation for the divergence patterns found in their life‐history traits.

Magnetic Resonance Imaging of the Brains of Three Peramelemorphian Marsupials

Peramelemorphians (bandicoots and bilbies) are a unique and diverse group of digging Australasian marsupials, but their behavioral neurology and neuroanatomy is poorly known. Here, we have used Magnetic Resonance Imaging (MRI) to study the brains of three peramelemorphians: two bandicoots (Perameles nasuta and Isoodon obesulus) and the bilby (Macrotis lagotis), which is endangered. These brains had been stored in formaldehyde solution for more than 80 years and one of our goals was to demonstrate the feasibilty of extracting detailed comparative neuroanatomical information from the long-term preserved brains of rare, endangered, and extinct animals. High resolution anatomical and Diffusion Tensor Imaging was performed using a 9.4-T Bruker BioSpec 94/20 Avance III MRI system (Bruker, Ettlingen, Germany) located at the UNSW in Sydney. We were able to differentiate areal and laminar topography within isocortical areas (primary somatosensory – S1; and visual - V1, V2), as well as subdivisions within olfactory and limbic allocortical regions (cingulate, hippocampal). Resolution of subcortical structures was sufficient to differentiate α and β segments within the visual nucleus of the thalamus. We identified several previously unrecognized longitudinal association fiber systems as well as a rich array of sensory thalamocortical connections. Dense fiber pathways were observed to S1 and in the midbrain auditory pathways (mainly the lateral lemniscus, but also the brachium of the inferior colliculus). Our findings demonstrate the feasibility of using this sort of imaging of archived brains to analyze the neuroanatomy of rare and evolutionarily significant species and to relate these findings to the behavioral neurology of those species.

Analysis of Phylogenomic Tree Space Resolves Relationships Among Marsupial Families.

A fundamental challenge in resolving evolutionary relationships across the tree of life is to account for heterogeneity in the evolutionary signal across loci. Studies of marsupial mammals have demonstrated that this heterogeneity can be substantial, leaving considerable uncertainty in the evolutionary timescale and relationships within the group. Using simulations and a new phylogenomic data set comprising nucleotide sequences of 1550 loci from 18 of the 22 extant marsupial families, we demonstrate the power of a method for identifying clusters of loci that support different phylogenetic trees. We find two distinct clusters of loci, each providing an estimate of the species tree that matches previously proposed resolutions of the marsupial phylogeny. We also identify a well-supported placement for the enigmatic marsupial moles (Notoryctes) that contradicts previous molecular estimates but is consistent with morphological evidence. The pattern of gene-tree variation across tree-space is characterized by changes in information content, GC content, substitution-model adequacy, and signatures of purifying selection in the data. In a simulation study, we show that incomplete lineage sorting can explain the division of loci into the two tree-topology clusters, as found in our phylogenomic analysis of marsupials. We also demonstrate the potential benefits of minimizing uncertainty from phylogenetic conflict for molecular dating. Our analyses reveal that Australasian marsupials appeared in the early Paleocene, whereas the diversification of present-day families occurred primarily during the late Eocene and early Oligocene. Our methods provide an intuitive framework for improving the accuracy and precision of phylogenetic inference and molecular dating using genome-scale data.

Bandicoot fossils and DNA elucidate lineage antiquity amongst xeric-adapted Australasian marsupials.

Bandicoots (Peramelemorphia) are a unique order of Australasian marsupials whose sparse fossil record has been used as prima facie evidence for climate change coincident faunal turnover. In particular, the hypothesized replacement of ancient rainforest-dwelling extinct lineages by antecedents of xeric-tolerant extant taxa during the late Miocene (~10 Ma) has been advocated as a broader pattern evident amongst other marsupial clades. Problematically, however, this is in persistent conflict with DNA phylogenies. We therefore determine the pattern and timing of bandicoot evolution using the first combined morphological + DNA sequence dataset of Peramelemorphia. In addition, we document a remarkably archaic new fossil peramelemorphian taxon that inhabited a latest Quaternary mosaic savannah-riparian forest ecosystem on the Aru Islands of Eastern Indonesia. Our phylogenetic analyses reveal that unsuspected dental homoplasy and the detrimental effects of missing data collectively obscure stem bandicoot relationships. Nevertheless, recalibrated molecular clocks and multiple ancestral area optimizations unanimously infer an early diversification of modern xeric-adapted forms. These probably originated during the late Palaeogene (30–40 Ma) alongside progenitors of other desert marsupials, and thus occupied seasonally dry heterogenous habitats long before the onset of late Neogene aridity.

The biology and palaeontology of the Peramelemorphia: a review of current knowledge and future research directions

Bandicoots and bilbies (Marsupialia : Peramelemorphia) represent the dominant omnivorous clade of Australasian marsupials and, as ground-dwelling, small- to medium-sized mammals, have not fared well in the 200 years since European settlement. Unlike large or charismatic marsupial species, the cryptic nature of bandicoots and bilbies tends to keep them out of the public eye, at a time when public interest plays a significant role in conservation efforts. The inconspicuous ‘rat-like’ appearance of many bandicoots and a generalist ecological strategy belie a complex biology of adaptive traits and evolutionary diversity. For a few species these biological traits have enabled them to make use of urban environments. In the main, however, peramelemorphians are facing ongoing pressure from introduced predators and human impacts. Basic biological information for many species, particularly those from New Guinea, is still lacking. In this review, we examine advances in the knowledge of the biology of this group over the past 25 years including anatomical, physiological and ecological studies. We also provide a comprehensive review of the fossil records of bandicoots in order to provide an up-to-date platform for future studies. From this work, it is clear that there is still much to be done regarding the taxonomy and biology of these animals before a more detailed understanding of the evolutionary history of this group can be elucidated.

Anatomical adaptations of the hind limb musculature of tree-kangaroos for arboreal locomotion (Marsupialia : Macropodinae)

Tree-kangaroos (Dendrolagini) are Australasian marsupials that inhabit tropical forests of far north-eastern Queensland and New Guinea. The secondary adaptation of tree-kangaroos to an arboreal lifestyle from a terrestrial heritage offers an excellent opportunity to study the adaptation of the musculoskeletal system for arboreal locomotion, particularly from a template well adapted to terrestrial bipedal saltation. We present a detailed descriptive study of the hind limb musculature of Lumholtz’s tree-kangaroo (D. lumholtzi) in comparison to other macropodines to test whether the hind limb musculature of tree-kangaroos is functionally adapted to the different mechanical demands of locomotion in the uneven three-dimensional arboreal environment. The hind limb musculature of Lumholtz’s tree-kangaroo (Dendrolagus lumholtzi), the western brush wallaby (Macropus irma), the western grey kangaroo (Macropus fuliginosus) and the quokka (Setonix brachyurus) are described. The hind limb anatomy of D. lumholtzi differed from that of the terrestrial macropodines in that the muscles had a greater degree of internal differentiation, relatively longer fleshy bellies and very short, stout tendons of insertion. There was also a modified arrangement of muscle origins and insertions that enhance mechanical advantage. Differences in the relative proportions of the hind limb muscle mass between tree-kangaroos and terrestrial macropodines reflect adaptation of the limb musculature of tree-kangaroos for arboreal locomotion. The hind limb musculature of Setonix was different to that of both Dendrolagus and Macropus, possibly reflecting its more basal phylogenetic position within the Macropodinae.

Tracking Marsupial Evolution Using Archaic Genomic Retroposon Insertions

Author SummaryEver since the first Europeans reached the Australian shores and were fascinated by the curious marsupials they found, the evolutionary relationships between the living Australian and South American marsupial orders have been intensively investigated. However, neither the morphological nor the more recent molecular methods produced an evolutionary consensus. Most problematic of the seven marsupial groups is the South American species Dromiciops gliroides, the only survivor of the order Microbiotheria. Several studies suggest that Dromiciops, although living in South America, is more closely related to Australian than to South American marsupials. This relationship would have required a complex migration scenario whereby several groups of ancestral South American marsupials migrated across Antarctica to Australia. We screened the genomes of the South American opossum and the Australian tammar wallaby for retroposons, unambiguous phylogenetic markers that occupy more than half of the marsupial genome. From analyses of nearly 217,000 retroposon-containing loci, we identified 53 retroposons that resolve most branches of the marsupial evolutionary tree. Dromiciops is clearly only distantly related to Australian marsupials, supporting a single Gondwanan migration of marsupials from South America to Australia. The new phylogeny offers a novel perspective in understanding the morphological and molecular transitions between the South American and Australian marsupials.

A phylogeny of Diprotodontia (Marsupialia) based on sequences for five nuclear genes

Even though the marsupial order Diprotodontia is one of the most heavily studied groups of Australasian marsupials, phylogenetic relationships within this group remain contentious. The more than 125 living species of Diprotodontia can be divided into two main groups: Vombatiformes (wombats and koalas) and Phalangerida. Phalangerida is composed of the kangaroos (Macropodidae, Potoroidae, and Hypsiprymnodontidae) and possums (Phalangeridae, Burramyidae, Petauridae, Pseudocheiridae, Tarsipedidae, and Acrobatidae). Much of the debate has focused on relationships among the families of possums and whether possums are monophyletic or paraphyletic. A limitation of previous investigations is that no study to date has investigated diprotodontian relationships using all genera. Here, we examine diprotodontian interrelationships using a nuclear multigene molecular data set representing all recognized extant diprotodontian genera. Maximum parsimony, maximum likelihood, and Bayesian methods were used to analyze sequence data obtained from protein-coding portions of ApoB, BRCA1, IRBP, Rag1, and vWF. We also applied a Bayesian relaxed molecular clock method to estimate times of divergence. Diprotodontia was rooted between Vombatiformes and Phalangerida. Within Phalangerida, the model-based methods strongly support possum paraphyly with Phalangeroidea (Burramyidae + Phalangeridae) grouping with the kangaroos (Macropodiformes) to the exclusion of Petauroidea (Tarsipedidae, Acrobatidae, Pseudocheiridae, and Petauridae). Within Petauroidea, Tarsipedidae grouped with both Petauridae and Pseudocheiridae to the exclusion of Acrobatidae. Our analyses also suggest that the diprotodontian genera Pseudochirops and Strigocuscus are paraphyletic and diphyletic, respectively, as currently recognized. Dating analyses suggest Diprotodontia diverged from other australidelphians in the late Paleocene to early Eocene with all interfamilial divergences occurring prior to the early Miocene except for the split between the Potoroidae and Macropodidae, which occurred sometime in the mid-Miocene. Ancestral state reconstructions using a Bayesian method suggest that the patagium evolved independently in the Acrobatidae, Petauridae, and Pseudocheiridae. Ancestral state reconstructions of ecological venue suggest that the ancestor of Diprotodontia was arboreal. Within Diprotodontia, the common ancestor of Macropodidae was reconstructed as terrestrial, suggesting that tree kangaroos ( Dendrolagus) are secondarily arboreal.

Toxoplasmosis in Wallabies (Macropus rufogriseus and Macropus eugenii): Blindness, Treatment with Atovaquone, and Isolation of Toxoplasma gondii

Australasian marsupials, especially wallabies, are highly susceptible to clinical toxoplasmosis. This paper describes the use of atovaquone for effective treatment of toxoplasmosis in 4 Bennett's wallabies (Macropus rufogriseus), along with the serology, isolation of Toxoplasma gondii, and genotyping of 3 T. gondii isolates from 5 captive wallabies. This is the first report of success in treating acute toxoplasmosis in wallabies, the first report of serology followed over a significant period of time, and the first report of isolation and genetic typing of T. gondii from wallabies in the United States.

A Dated Phylogeny of Marsupials Using a Molecular Supermatrix and Multiple Fossil Constraints

Phylogenetic relationships within marsupials were investigated based on a 20.1-kilobase molecular supermatrix comprising 7 nuclear and 15 mitochondrial genes analyzed using both maximum likelihood and Bayesian approaches and 3 different partitioning strategies. The study revealed that base composition bias in the 3rd codon positions of mitochondrial genes misled even the partitioned maximum-likelihood analyses, whereas Bayesian analyses were less affected. After correcting for base composition bias, monophyly of the currently recognized marsupial orders, of Australidelphia, and of a clade comprising Dasyuromorphia, Notoryctes, and Peramelemorphia, were supported strongly by both Bayesian posterior probabilities and maximum-likelihood bootstrap values. Monophyly of the Australasian marsupials, of Notoryctes + Dasyuromorphia, and of Caenolestes + Australidelphia were less well supported. Within Diprotodontia, Burramyidae + Phalangeridae received relatively strong support. Divergence dates calculated using a Bayesian relaxed molecular clock and multiple age constraints suggested at least 3 independent dispersals of marsupials from North to South America during the Late Cretaceous or early Paleocene. Within the Australasian clade, the macropodine radiation, the divergence of phascogaline and dasyurine dasyurids, and the divergence of perameline and peroryctine peramelemorphians all coincided with periods of significant environmental change during the Miocene. An analysis of “unrepresented basal branch lengths” suggests that the fossil record is particularly poor for didelphids and most groups within the Australasian radiation.

Combined Mitochondrial and Nuclear DNA Sequences Resolve the Interrelations of the Major Australasian Marsupial Radiations

Australasian marsupials include three major radiations, the insectivorous/carnivorous Dasyuromorphia, the omnivorous bandicoots (Peramelemorphia), and the largely herbivorous diprotodontians. Morphologists have generally considered the bandicoots and diprotodontians to be closely related, most prominently because they are both syndactylous (with the 2nd and 3rd pedal digits being fused). Molecular studies have been unable to confirm or reject this Syndactyla hypothesis. Here we present new mitochondrial (mt) genomes from a spiny bandicoot (Echymipera rufescens) and two dasyurids, a fat-tailed dunnart (Sminthopsis crassicaudata) and a northern quoll (Dasyurus hallucatus). By comparing trees derived from pairwise base-frequency differences between taxa with standard (absolute, uncorrected) distance trees, we infer that composition bias among mt protein-coding and RNA sequences is sufficient to mislead tree reconstruction. This can explain incongruence between trees obtained from mt and nuclear data sets. However, after excluding major sources of compositional heterogeneity, both the "reduced-bias" mt and nuclear data sets clearly favor a bandicoot plus dasyuromorphian association, as well as a grouping of kangaroos and possums (Phalangeriformes) among diprotodontians. Notably, alternatives to these groupings could only be confidently rejected by combining the mt and nuclear data. Elsewhere on the tree, Dromiciops appears to be sister to the monophyletic Australasian marsupials, whereas the placement of the marsupial mole (Notoryctes) remains problematic. More generally, we contend that it is desirable to combine mt genome and nuclear sequences for inferring vertebrate phylogeny, but as separately modeled process partitions. This strategy depends on detecting and excluding (or accounting for) major sources of non-historical signal, such as from compositional non-stationarity. [Base composition; combined data; marsupial; mitochondrial genome; phylogeny.].

Relationships Among Families of Diprotodontia (Marsupialia) and the Phylogenetic Position of the Autapomorphic Honey Possum (Tarsipes rostratus)

The Australasian marsupial order Diprotodontia includes ten extant families that are grouped into the suborders Vombatiformes (koalas and wombats), Macropodiformes (kangaroos and allies), and Phalangeriformes (possums and gliders). We investigated interfamilial relationships using mitochondrial 12S rRNA, valine tRNA, and 16S rRNA gene sequences. Our results support the monophyly of both Vombatiformes and Macropodiformes, but not Phalangeriformes. Among possums and gliders, there was strong support for a petauroid clade that includes Pseudocheiridae (ringtail possums), Petauridae (sugar glider, striped possums), Acrobatidae (feathertail possums), and the monotypic family Tarsipedidae, which is represented by the highly specialized and autapomorphic honey possum (Tarsipes rostratus). Other prior hypotheses for the phylogenetic placement of the honey possum were rejected by statistical tests. The inclusion of the honey possum within Petauroidea suggests that derived ultrastructural features of Tarsipes' spermatozoa evolved independently in Tarsipes versus polyprotodont Australasian marsupials.

Comparative Postnatal Ontogeny of the Skull in Dromiciops gliroides (Marsupialia: Microbiotheriidae)

Dromiciops gliroides is the single extant representative of the marsupial family Microbiotheriidae. The importance of D. gliroides stems from its peculiar cranial anatomy (specifically the configuration of the tympanic region) and dentition and from its controversial position in the phylogenetic tree of marsupials—a South American form more closely related to Australasian marsupials. We studied the postnatal ontogeny of the skull in D. gliroides by analyzing qualitative and allometric aspects of the development of cranial structures. We compared recently weaned young individuals with adults and described the bivariate and multivariate allometric trends of 14 cranial dimensions for a sample of 37–51 specimens. Most cranial components develop in a way similar to didelphids studied so far. However, some trends (e.g., growth of the orbit) seem particular to D. gliroides. The microbiotheriid bulla of D. gliroides, a structure to which five basicranial bones contribute parts, is already present in its highly derived condition in the youngest specimens of our series. We conclude that except for the bulla, most of the cranial development in D. gliroides is highly conservative and that some peculiarities may be shared with other marsupials of similarly small body size. Data on australidelphians and small-size didelphids are needed to contrast these patterns.

Mitochondrial genomes of a bandicoot and a brushtail possum confirm the monophyly of australidelphian marsupials

Recent molecular analyses suggest that the position of bandicoots is the major difficulty in determining the root of the tree of extant marsupials. To resolve this, we analyse mitochondrial genome sequences of a bandicoot (Isoodon macrourus) and a brushtail possum (Trichosurus vulpecula) together with the previously available marsupial mitochondrial genomes, the Virginia opossum (Didelphis virginiana) and the wallaroo (Macropus robustus). Analyses of mitochondrial protein-coding and RNA genes strongly support the bandicoot as sister to the wallaroo and the brushtail possum. This result, combined with other recent molecular analyses, confirms the monophyly of Australidelphia (Australasian marsupials plus Dromiciops from South America). Further, RY coding was found to nullify AGCT coding nucleotide composition bias.

Ontogenetic and phylogenetic transformations of the vomeronasal complex and nasal floor elements in marsupial mammals

Histological sections and three-dimensional reconstructions of section-series were used to document the anatomy of the vomeronasal complex and other aspects of the ethmoidal region in representatives of 13 families and six orders of marsupial mammals, including for the first time Microbiotheria. The changes during growth of several features were examined in ontogenetic series. Marsupials are very conservative in comparison with eutherians regarding the vomeronasal complex. All have a vomeronasal organ and a nasopalatine duct, have no nasopalatine duct cartilage, have no (or just an incipient) palatine cartilage, and the overall construction of the nasal floor is uniform across species. Most features examined show a high degree of homoplasy (e.g. presence of glandular ridges, isolated dorsal process of the paraseptal cartilage), and their systematic value is confined to low taxonomic levels. Significant ontogenetic changes occur in features usually discussed in the systematic/taxonomic literature. Amongst the didelphids examined, Caluromys philander shows several autapomorphies. It is hypothesized that the opening of the VNO into the upper end of the nasopalatine duct was present in the marsupial groundplan. Most marsupials have a large and horizontal anterior transverse lamina, the plesiomorphic condition, which becomes oblique in diprotodontians. Some features are autapomorphies of well-supported monophyletic groups of marsupials, e.g. the conspicuous internasal communication of perameliformes and the «tube-like» or ring-shaped paraseptal cartilage of vombatiformes. An outer bar joining the middle (and not the dorsal-most portion) of the paraseptal cartilage characterizes Australasian marsupials and Dromiciops, with the exclusion of perameliformes, and evolved independently in Caluromys philander.

Ontogenetic and phylogenetic transformations of the vomeronasal complex and nasal floor elements in marsupial mammals

Abstract Histological sections and three-dimensional reconstructions of section-series were used to document the anatomy of the vomeronasal complex and other aspects of the ethmoidal region in representatives of 13 families and six orders of marsupial mammals, including for the first time Microbiotheria. The changes during growth of several features were examined in ontogenetic series. Marsupials are very conservative in comparison with eutherians regarding the vomeronasal complex. All have a vomeronasal organ and a nasopalatine duct, have no nasopalatine duct cartilage, have no (or just an incipient) palatine cartilage, and the overall construction of the nasal floor is uniform across species. Most features examined show a high degree of homoplasy (e.g. presence of glandular ridges, isolated dorsal process of the paraseptal cartilage), and their systematic value is confined to low taxonomic levels. Significant ontogenetic changes occur in features usually discussed in the systematic/taxonomic literature. Amongst the didelphids examined, Caluromys philander shows several autapomorphies. It is hypothesized that the opening of the VNO into the upper end of the nasopalatine duct was present in the marsupial groundplan. Most marsupials have a large and horizontal anterior transverse lamina, the plesiomorphic condition, which becomes oblique in diprotodontians. Some features are autapomorphies of well-supported monophyletic groups of marsupials, e.g. the conspicuous internasal communication of perameliformes and the «tube-like» or ring-shaped paraseptal cartilage of vombatiformes. An outer bar joining the middle (and not the dorsal-most portion) of the paraseptal cartilage characterizes Australasian marsupials and Dromiciops , with the exclusion of perameliformes, and evolved independently in Caluromys philander .