Search

In this work, we present several new materials collected at the pink sandstone levels from the Las Flores Formation at the Cerro Pan de Azúcar (Gaiman, Chubut Province, Argentina) and compare them with taxa present in other localities of similar age. The Metatheria taxa described here are 1) the 'Ameridelphia' Sternbergiidae indet; 2) the Didelphimorphia Protodidelphis cf. mastodontoides and Guggenheimia glykeia sp. nov. (Protodidelphidae); 3) the Polydolopimorphia Pliodolops rothi and Pliodolops cf. kamektsen (Polydolopidae); and 4) the Microbiotheria Eomicrobiotherium diluculum sp. nov. (Microbiotheriidae). On the other hand, the Cingulata Dasypodidae is represented by the Astegotheriini Prostegotherium astrifer. This fauna shares more species with those occurring in the localities from Paso del Sapo than with any other early – middle Eocene localities. However, at the generic level, it shares several taxa with the Itaboraian fauna from Sao José de Itaboraí. Finally, the faunal associations from Pan de Azúcar, Paso del Sapo, Cañadón Hondo, and Bajo de la Palangana could be, at least in part, synchronous, representing locally the Riochican SALMA, with an age spanning from 51 to 45 Ma (early Ypresian- early Lutetian). [ABSTRACT FROM AUTHOR]

Three marsupial species are present in Palaeogene assemblages from south-eastern Serbia, Amphiperatherium minutum (Aymard, 1846), A. exile (Gervais, 1848–1852) and a species of Peratherium Aymard, 1850. These species are common in the late Eocene and early Oligocene of Western and Central Europe and their presence in South-Eastern Europe indicate that by the end of the Eocene, the eastwards dispersal of these marsupial species was already a fact. The presence of the same marsupial species in Serbia and in Western Europe is surprising, as the difference in composition between the Serbian and Western European rodent faunas indicates a limited faunal exchange between these areas in the late Eocene and early Oligocene. In marsupials, the stylar shelf of the upper molars shows a large morphological variation. A lesser-known variation is the presence of a transverse crista in the stylar shelf. These occur in various marsupial species, but so far were not known to be present in Amphiperatherium minutum. In our opinion, the large morphological variation of the stylar shelf is thus better not used to define a new species. [ABSTRACT FROM AUTHOR]

The Amazonian region covers a significant part of the South American continent and harbors outstanding biodiversity. However, much of its history is still unknown. This situation has begun to change with paleontological field efforts over the last decades, which have been proving that fossils can be common in this region. Despite their great current species richness and abundance in the area today, marsupials have a sparse fossil record, restricted to a few specimens from handful Cenozoic Amazonian localities. Here we present new records of fossil marsupial teeth from the Solimões Formation (lower Eocene–Pliocene), on the Juruá and Envira riverbanks (Acre, Northwestern Brazil). The localities investigated yield at least four distinct didelphid didelphimorphians at PRE 06 (Ponto Rio Envira: Marmosini ?Marmosa sp., Didelphis cf. D. solimoensis, Thylamys? colombianus, plus unidentified didelphids), and two paucituberculatans from the Juruá River localities (Ponto Rio Juruá: the palaeothentid Palaeothentinae indet. at PRJ 25 and PRJ 33’, and Abderitidae indet. from PRJ 33). In agreement with the associated mammalian faunas, most of the didelphids, except for Thylamys? colombianus from PRE 06, indicate a (?early) Late Miocene age for this locality. Conversely, the abderitid specimens found in situ at PRJ 33 would match a Middle Miocene age. The palaeothentids found at PRJ 25 and PRJ 33’ localities cannot be considered for biostratigraphic inferences, since they were found outside a stratigraphic context. Nevertheless, these paucituberculatans considerably add to our knowledge, as they are the first ever recorded in Brazilian Amazonia.

The Amazonian region covers a significant part of the South American continent and harbors outstanding biodiversity. However, much of its history is still unknown. This situation has begun to change with paleontological field efforts over the last decades, which have been proving that fossils can be common in this region. Despite their great current species richness and abundance in the area today, marsupials have a sparse fossil record, restricted to a few specimens from handful Cenozoic Amazonian localities. Here we present new records of fossil marsupial teeth from the Solimões Formation (lower Eocene–Pliocene), on the Juruá and Envira riverbanks (Acre, Northwestern Brazil). The localities investigated yield at least four distinct didelphid didelphimorphians at PRE 06 (Ponto Rio Envira: Marmosini ?Marmosa sp., Didelphis cf. D. solimoensis, Thylamys? colombianus, plus unidentified didelphids), and two paucituberculatans from the Juruá River localities (Ponto Rio Juruá: the palaeothentid Palaeothentinae indet. at PRJ 25 and PRJ 33’, and Abderitidae indet. from PRJ 33). In agreement with the associated mammalian faunas, most of the didelphids, except for Thylamys? colombianus from PRE 06, indicate a (?early) Late Miocene age for this locality. Conversely, the abderitid specimens found in situ at PRJ 33 would match a Middle Miocene age. The palaeothentids found at PRJ 25 and PRJ 33’ localities cannot be considered for biostratigraphic inferences, since they were found outside a stratigraphic context. Nevertheless, these paucituberculatans considerably add to our knowledge, as they are the first ever recorded in Brazilian Amazonia. [ABSTRACT FROM AUTHOR]

The pattern of dental replacement in marsupial mammals has received much attention for its derived nature and potential relationship to the life history of the group. However, few species have been studied thoroughly, and little is known about the embryonic structures and their use in addressing issues of homology and dental evolution in general. We studied a developmental series of ten individuals of pouch young Caluromys philander to thoroughly document dental development with histological sections and 3D models of dental series. We report that the successor P3 arises from a lingual successional lamina from its predecessor dP3. The germs of vestigial, unerupted deciduous incisors and canines are present alongside their respective permanent successors. These discoveries demonstrate significant differences from the developmental patterns reported for Didelphis and Monodelphis and illustrate that an unsuspected diversity of dental ontogeny is not reflected in the adult pattern of mineralised, erupted or almost erupted teeth. [ABSTRACT FROM AUTHOR]

The diversity of the diprotodontids provides an excellent opportunity to study how a basic marsupial cortical plan has been modified for the needs of the mammals living in different habitats. Very little is known about the connections of the cerebral cortex with the deep brain structures (basal ganglia and thalamus) in this evolutionarily significant group of mammals. In this study, we performed mapping of brain regions and connections in a diprotodontid marsupial from data obtained from an excised brain scanned in high‐field (9.4 T) microstructural magnetic resonance imaging (MRI) instrument. The analysis was based on two MRI methodologies. First, high‐resolution structural scans were used to map MRI visible brain regions from T1w and T2w images. Second, extensive diffusion tensor imaging (DTI) data were obtained to elucidate connectivity between brain areas using deterministic diffusion tracking of neuronal brain fibers. From the data, we were able to identify corticostriate connections between the frontal association and dorsomedial isocortex and the head of the caudate, and between the lateral somatosensory cortex and the putamen. We were also able to follow the olfactory and limbic connections by tracing fibers in the fornix, cingulum, intrabulbar part of the anterior commissure, and lateral olfactory tract. There was segregation of fibers in the anterior commissure such that olfactory connections passed through the rostroventral part and successively more dorsal cortical areas connected through more dorsal parts of the commissure. Our findings confirm a common pattern of cortical connectivity in therian mammals, even where brain expansion has occurred independently in diverse groups. [ABSTRACT FROM AUTHOR]

Abstract Background Different types of proteins diverge at vastly different rates. Moreover, the same type of protein has been observed to evolve with different rates in different phylogenetic lineages. In the present study we measured the rates of protein evolution in Eutheria (placental mammals) and Metatheria (marsupials) on a genome-wide basis and we propose that the gene position in the genome landscape has an important influence on the rate of protein divergence. Results We analyzed a protein-encoding gene set (n = 15,727) common to 16 mammals (12 Eutheria and 4 Metatheria). Using sliding windows that averaged regional effects of protein divergence we constructed landscapes in which strong and lineage-specific regional effects were seen on the molecular clock rate of protein divergence. Within each lineage, the relatively high rates were preferentially found in subtelomeric chromosomal regions. Such regions were observed to contain important and well-studied loci for fetal growth, uterine function and the generation of diversity in the adaptive repertoire of immunoglobulins. Conclusions A genome landscape approach visualizes lineage-specific regional differences between Eutherian and Metatherian rates of protein evolution. This phenomenon of chromosomal position is a new element that explains at least part of the lineage-specific effects and differences between proteins on the molecular clock rates.

Abstract Background Besnoitia darlingi, B. neotomofelis and B. oryctofelisi are closely related coccidian parasites with felids as definitive hosts. These parasites use a variety of animal species as intermediate hosts. North American opossums (Didelphis virginiana), North American southern plains woodrats (Neotoma micropus) and South American domestic rabbits (Oryctolagus cuniculus) are intermediate hosts of B. darlingi, B. neotomofelis and B. oryctofelisi, respectively. Based on conserved regions in the internal transcribed spacer-1 (ITS1) sequence of the ribosomal DNA (rDNA), a real-time PCR for a sensitive detection of these Besnoitia spp. in tissues of intermediate hosts and faeces of definitive hosts has recently been established. Available sequence data suggest that species such as B. akodoni and B. jellisoni are also covered by this real-time PCR. It has been hypothesised that additional Besnoitia spp. exist worldwide that are closely related to B. darlingi or B. darlingi-like parasites (B. neotomofelis, B. oryctofelisi, B. akodoni or B. jellisoni). Also related, but not as closely, is B. besnoiti, the cause of bovine besnoitiosis. Methods Faecal samples from two free-ranging cheetahs (Acinonyx jubatus) from Namibia that had previously tested positive for coccidian parasites by coproscopy were used for this study. A conventional PCR verified the presence of coccidian parasite DNA. To clarify the identity of these coccidia, the faecal DNA samples were further characterised by species-specific PCRs and Sanger sequencing. Results One of the samples tested positive for B. darlingi or B. darlingi-like parasites by real-time PCR, while no other coccidian parasites, including Toxoplasma gondii, Hammondia hammondi, H. heydorni, B. besnoiti and Neospora caninum, were detected in the two samples. The rDNA of the B. darlingi-like parasite was amplified and partially sequenced. Comparison with existing sequences in GenBank revealed a close relationship to other Besnoitia spp., but also showed clear divergences. Conclusions Our results suggest that a so far unknown Besnoitia species exists in Namibian wildlife, which is closely related to B. darlingi, B. neotomofelis, B. oryctofelisi, B. akodoni or B. jellisoni. The cheetah appears to be the definitive host of this newly discovered parasite, while prey species of the cheetah may act as intermediate hosts.

Morotodon aenigmaticus gen. et sp. nov. (Mammalia, Metatheria, ?Herpetotheriidae) from the early or early-middle Miocene of equatorial Africa (Moroto II locality, Moroto District, northeastern Uganda) is characterized by a short anterior cingulum, a buccal shelf, a well-developed hypoconulid in a central position, and a trigonid and talonid with similar mesio-distal lengths. Its small size and morphology suggest mostly insectivorous-faunivorous feeding habits. The faunal association of Moroto II, as well as previous palaeoenvironmental analyses, suggest that Morotodon lived in open woodland and bushland areas surrounded by grasses. Morotodon aenigmaticus shows several features reminiscent of early herpetotheriids, such as Golerdelphys stocki (late Paleocene of North America), and Amphiperatherium ambiguum (Eocene of Europe); this suggests an origin for its lineage previous to the Oligocene. In summary, its affinities lie with Northern Hemisphere herpetotheriids, and, most probably, with European ones. [ABSTRACT FROM AUTHOR]

The gray short-tailed opossum (Monodelphis domestica) is an established laboratory-bred marsupial model for biomedical research. It is a critical species for comparative genomics research, providing the pivotal phylogenetic outgroup for studies of derived vs ancestral states of genomic/epigenomic characteristics for eutherian mammal lineages. To characterize the current genetic profile of this laboratory marsupial, we examined 79 individuals from eight established laboratory strains. Double digest restriction site-associated DNA sequencing and whole-genome resequencing experiments were performed to investigate the genetic architecture in these strains. A total of 66,640 highquality single nucleotide polymorphisms (SNPs) were identified. We analyzed SNP density, average heterozygosity, nucleotide diversity, and population differentiation parameter Fst within and between the eight strains. Principal component and population structure analysis clearly resolve the strains at the level of their ancestral founder populations, and the genetic architecture of these strains correctly reflects their breeding history. We confirmed the successful establishment of the first inbred laboratory opossum strain LSD (inbreeding coefficient F>0.99) and a nearly inbred strain FD2M1 (0.98

Marsupials represent a major mammalian diversification today restricted geographically to the Americas (but chiefly to the Neotropical Region) and Australasia. The group is highly diverse in morphology, ecology, and habits, and this is reflected to a great extent in cranial morphology. Here, we selected the largest specimens available from a post-weaning developmental series of a large-scale ongoing ontogenetic study to generate a linear multivariate morphospace of the skull of living marsupials. This sample comprised 106 species covering most living clades, and we used a basic set of measurements that estimate dimensions of major skull structures. We specified some predictions suited for a diverse but ancient group with an allopatric distribution. The cranial morphospace of living marsupials was low-dimensional, dominated by size/allometric as well as shape trends of robustness versus gracility and elongation versus depth. Phylogenetic structuring was present, especially in relation to diprotodontians, and the ecological imprint of patterns in phylomorphospace was marked. Evolutionary convergence was statistically detectable between selected species clusters combining Neotropical and Australasian species, chiefly among animalivorous forms but also in predominantly phytophagous arboreal possums and woolly opossums. Convergence among Australian large grazers may be influenced or limited by interspecific competition. Evolutionary divergence was remarkable in some groups, but evolutionary rates varied greatly across divergent forms. Some space voids may be due to extinction; fossil forms are expected to fill in these voids, expand the realized morphospace, and perhaps increase intra- and intercontinental convergence. [ABSTRACT FROM AUTHOR]

Background: Besnoitia darlingi, B. neotomofelis and B. oryctofelisi are closely related coccidian parasites with felids as definitive hosts. These parasites use a variety of animal species as intermediate hosts. North American opossums (Didelphis virginiana), North American southern plains woodrats (Neotoma micropus) and South American domestic rabbits (Oryctolagus cuniculus) are intermediate hosts of B. darlingi, B. neotomofelis and B. oryctofelisi, respectively. Based on conserved regions in the internal transcribed spacer-1 (ITS1) sequence of the ribosomal DNA (rDNA), a real-time PCR for a sensitive detection of these Besnoitia spp. in tissues of intermediate hosts and faeces of definitive hosts has recently been established. Available sequence data suggest that species such as B. akodoni and B. jellisoni are also covered by this real-time PCR. It has been hypothesised that additional Besnoitia spp. exist worldwide that are closely related to B. darlingi or B. darlingi-like parasites (B. neotomofelis, B. oryctofelisi, B. akodoni or B. jellisoni). Also related, but not as closely, is B. besnoiti, the cause of bovine besnoitiosis. Methods: Faecal samples from two free-ranging cheetahs (Acinonyx jubatus) from Namibia that had previously tested positive for coccidian parasites by coproscopy were used for this study. A conventional PCR verified the presence of coccidian parasite DNA. To clarify the identity of these coccidia, the faecal DNA samples were further characterised by species-specific PCRs and Sanger sequencing. Results: One of the samples tested positive for B. darlingi or B. darlingi-like parasites by real-time PCR, while no other coccidian parasites, including Toxoplasma gondii, Hammondia hammondi, H. heydorni, B. besnoiti and Neospora caninum, were detected in the two samples. The rDNA of the B. darlingi-like parasite was amplified and partially sequenced. Comparison with existing sequences in GenBank revealed a close relationship to other Besnoitia spp., but also showed clear divergences. Conclusions: Our results suggest that a so far unknown Besnoitia species exists in Namibian wildlife, which is closely related to B. darlingi, B. neotomofelis, B. oryctofelisi, B. akodoni or B. jellisoni. The cheetah appears to be the definitive host of this newly discovered parasite, while prey species of the cheetah may act as intermediate hosts. [ABSTRACT FROM AUTHOR]

We present a systematic review of the extinct species included in the family Caenolestidae, one of the few South American metatherian groups that has survived to the present. We perform a cladistic analysis based on a data matrix consisting of all extant and extinct species that have been referred to this family, 100 morphological characters and two sets of molecular data (cytochrome b and cytochrome c oxidase I). Morphological and molecular data were analysed separately and in combination, under maximum parsimony and maximum likelihood methods. As a result, caenolestids are recovered as a monophyletic group within which we formally recognize three new taxa: Caenolestoides miocaenicus gen. & sp. nov. Gaimanlestes pascuali gen. & sp. nov. and Stilotherium parvum sp. nov. from the Early Miocene of Patagonia, Argentina. Stilotherium is the earliest diverging lineage of caenolestids followed by Gaimanlestes , while C. miocaenicus was recovered as the extinct species most closely related to extant caenolestids. [ABSTRACT FROM AUTHOR]

Background: Different types of proteins diverge at vastly different rates. Moreover, the same type of protein has been observed to evolve with different rates in different phylogenetic lineages. In the present study we measured the rates of protein evolution in Eutheria (placental mammals) and Metatheria (marsupials) on a genome-wide basis and we propose that the gene position in the genome landscape has an important influence on the rate of protein divergence. Results: We analyzed a protein-encoding gene set (n = 15,727) common to 16 mammals (12 Eutheria and 4 Metatheria). Using sliding windows that averaged regional effects of protein divergence we constructed landscapes in which strong and lineage-specific regional effects were seen on the molecular clock rate of protein divergence. Within each lineage, the relatively high rates were preferentially found in subtelomeric chromosomal regions. Such regions were observed to contain important and well-studied loci for fetal growth, uterine function and the generation of diversity in the adaptive repertoire of immunoglobulins. Conclusions: A genome landscape approach visualizes lineage-specific regional differences between Eutherian and Metatherian rates of protein evolution. This phenomenon of chromosomal position is a new element that explains at least part of the lineage-specific effects and differences between proteins on the molecular clock rates. [ABSTRACT FROM AUTHOR]

Polydolopidae is a family of Palaeogene marsupials recorded from outcrops in southern South America and the Antarctic Peninsula. They are mostly represented by skull fragments or maxillary, dentary and molar remains. A taxonomic and systematic revision is carried out with the inclusion of a phylogenetic analysis encompassing almost every polydolopid species and five marsupial species found to be related to them in previous analyses (Bonapartherium hinakusijum , Epidolops ameghinoi , Microbiotherium tehuelchum , Prepidolops didelphoides and Roberthoffstetteria nationalgeographica). The Polydolopidae was recovered as a monophyletic group, even though no resolution about its sister-group can be found. The following genera are recovered: Antarctodolops , Amphidolops , Archaeodolops , Eudolops , Hypodolops gen. nov. , Kramadolops , Pliodolops , Pseudolops and two unidentified genera (Gen. et sp. indet 1 and 2). One genus and three new species are recognized. The family appeared at the beginning of the Palaeocene and disappeared during the Early Oligocene. The extinction of the group could be related to climatic deterioration in the Early Oligocene, when temperature and the humidity dropped, provoking desertification in the region where Polydolopids evolved. [ABSTRACT FROM AUTHOR]

Copyright of Spanish Journal of Palaeontology is the property of Socieadad Espanola de Paleontologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The musculoskeletal system of marsupial mammals has numerous unusual features beyond the pouch and epipubic bones. One example is the widespread absence or reduction (to a fibrous “patelloid”) of the patella (“kneecap”) sesamoid bone, but prior studies with coarse sampling indicated complex patterns of evolution of this absence or reduction. Here, we conducted an in-depth investigation into the form of the patella of extant marsupial species and used the assembled dataset to reconstruct the likely pattern of evolution of the marsupial patella. Critical assessment of the available literature was followed by examination and imaging of museum specimens, as well as CT scanning and histological examination of dissected wet specimens. Our results, from sampling about 19% of extant marsupial species-level diversity, include new images and descriptions of the fibrocartilaginous patelloid in Thylacinus cynocephalus (the thylacine or “marsupial wolf”) and other marsupials as well as the ossified patella in Notoryctes ‘marsupial moles’, Caenolestes shrew opossums, bandicoots and bilbies. We found novel evidence of an ossified patella in one specimen of Macropus rufogriseus (Bennett’s wallaby), with hints of similar variation in other species. It remains uncertain whether such ossifications are ontogenetic variation, unusual individual variation, pathological or otherwise, but future studies must continue to be conscious of variation in metatherian patellar sesamoid morphology. Our evolutionary reconstructions using our assembled data vary, too, depending on the reconstruction algorithm used. A maximum likelihood algorithm favours ancestral fibrocartilaginous “patelloid” for crown clade Marsupialia and independent origins of ossified patellae in extinct sparassodonts, peramelids, notoryctids and caenolestids. A maximum parsimony algorithm favours ancestral ossified patella for the clade [Marsupialia + sparassodonts] and subsequent reductions into fibrocartilage in didelphids, dasyuromorphs and diprotodonts; but this result changed to agree more with the maximum likelihood results if the character state reconstructions were ordered. Thus, there is substantial homoplasy in marsupial patellae regardless of the evolutionary algorithm adopted. We contend that the most plausible inference, however, is that metatherians independently ossified their patellae at least three times in their evolution. Furthermore, the variability of the patellar state we observed, even within single species (e.g. M. rufogriseus), is fascinating and warrants further investigation, especially as it hints at developmental plasticity that might have been harnessed in marsupial evolution to drive the complex patterns inferred here.

Argyrolagus constitutes, both for its craniodental and postcranial anatomy, one of the most notably specialized South American Neogene metatherians. Differentiating it from any other South American mammal, bipedal jumping has been proposed for Argyrolagus, even though this hypothesis was not supported by morphofunctional studies. Here, we describe the postcranium of A. scaglai (from the Pliocene of Argentina), perform a functional analysis, and interpret it against a varied background of locomotor adaptations of extant mammals. The configuration of joints, the degree of development and location of muscular insertions were mainly analyzed, and functional indices were evaluated. This study indicates that Argyrolagus had stabilized glenohumeral and humeroulnar joints, a great development of the arm retractors, flexors-extensors of the digits, pronator, and supinator muscles, low restrictive humeroradial joint, powerful extensor muscles of the hip, knee, and ankle, good development of the iliac muscle, and restrictive hind limb joints. Joint configurations are interpreted to be optimal to resist the impacts during jumping, avoiding dislocation, compatible with digging activity. A compromise between the capacities to dig and manipulate objects is inferred. It is concluded that Argyrolagus had bipedal jumping locomotion as well as good capacity to dig, constituting an astonishing case of convergence with the small bipedal rodents and small Australian macropodids. We suggest that bipedal jumping in Miocene and Pliocene argyrolagids should not be necessarily related to a particular arid environment. Finally, we evaluate the importance of postcranial features to understand the phylogenetic relationships of Argyrolagidae in a comprehensive phylogeny of Metatheria. [ABSTRACT FROM AUTHOR]

The phylogenetic relationships of "opossum-like" metatherians, Herpetotheriidae and Peradectidae, continue to be debated, and yet they are key taxa in the evolutionary history of the crown-group Marsupialia. With state-of-the-art technologies such as X-ray computed tomography (CT scanning), it is now possible to access the inner anatomy of the skull and particularly the ear region, which is more and more frequently used in phylogenetic analyses. Here we describe for the first time the petrosal and inner ear anatomy of the type species Peratherium elegans from the early Oligocene of Ronzon, together with Amphiperatherium elegans from the Eocene of the Montmartre Gypsum. A parsimony analysis of cranial (including petrosal), dental and postcranial characters in 25 metatherians (extant and fossil taxa including the four herpetotheriids studied herein) does not support inclusion of herpetotheriids or peradectids within Didelphimorphia. The results indicate the monophyly of Peratherium cuvieri, P. elegans and A. minutum, but the other herpetotheriid in the analysis, Herpetotherium cf. fugax, is more closely related to the crown-group clade Marsupialia. Peradectids and herpetotheriids, traditionally considered as "opossum-like", are here found to be stem metatherians and stem marsupials, respectively. The hypothesis in favour of an ancient origin of opossums (Didelphidae) is therefore questioned. [ABSTRACT FROM AUTHOR]

The musculoskeletal system of marsupial mammals has numerous unusual features beyond the pouch and epipubic bones. One example is the widespread absence or reduction (to a fibrous "patelloid'') of the patella ("kneecap'') sesamoid bone, but prior studies with coarse sampling indicated complex patterns of evolution of this absence or reduction. Here, we conducted an in-depth investigation into the form of the patella of extant marsupial species and used the assembled dataset to reconstruct the likely pattern of evolution of the marsupial patella. Critical assessment of the available literature was followed by examination and imaging of museum specimens, as well asCTscanning and histological examination of dissected wet specimens. Our results, from sampling about 19% of extant marsupial species-level diversity, include new images and descriptions of the fibrocartilaginous patelloid in Thylacinus cynocephalus (the thylacine or "marsupial wolf'') and other marsupials as well as the ossified patella in Notoryctes 'marsupial moles', Caenolestes shrew opossums, bandicoots and bilbies. We found novel evidence of an ossified patella in one specimen of Macropus rufogriseus (Bennett's wallaby), with hints of similar variation in other species. It remains uncertain whether such ossifications are ontogenetic variation, unusual individual variation, pathological or otherwise, but future studies must continue to be conscious of variation in metatherian patellar sesamoid morphology. Our evolutionary reconstructions using our assembled data vary, too, depending on the reconstruction algorithm used. A maximum likelihood algorithm favours ancestral fibrocartilaginous "patelloid'' for crown clade Marsupialia and independent origins of ossified patellae in extinct sparassodonts, peramelids, notoryctids and caenolestids. A maximum parsimony algorithm favours ancestral ossified patella for the clade [Marsupialia + sparassodonts] and subsequent reductions into fibrocartilage in didelphids, dasyuromorphs and diprotodonts; but this result changed to agree more with the maximum likelihood results if the character state reconstructions were ordered. Thus, there is substantial homoplasy in marsupial patellae regardless of the evolutionary algorithm adopted. We contend that the most plausible inference, however, is that metatherians independently ossified their patellae at least three times in their evolution. Furthermore, the variability of the patellar state we observed, even within single species (e.g. M. rufogriseus), is fascinating and warrants further investigation, especially as it hints at developmental plasticity that might have been harnessed in marsupial evolution to drive the complex patterns inferred here. [ABSTRACT FROM AUTHOR]

With two recognized species, the extinct (late Eocene) Groeberia is periodically at the centre of systematic disputes. On the basis of its best-preserved specimen, we describe in detail the dental and functional morphology of the masticatory apparatus of Groeberia minoprioi. A review of its dental anatomy indicates that Groeberia has a tribosphenic molar pattern which confirms its therian affinities. Its dental formula of I2/1; C1/1; P3/1; M4/4 is compatible with the usual metatherian set of three premolars and four molars in the upper dentition, and with the common 'pseudodiprotodont' lower postcanine formula of one premolar (p3) and four molars. A cladistic analysis resulted in the inclusion of Groeberia among australidelphian metatherians, clustering with vombatiform diprotodontians in the strict consensus tree; however, these affinities require further testing. The functional morphology of the masticatory apparatus suggests distinct incisive and chewing phases. The incisive stroke was followed by a power stroke with a combination of proal and ectental motion of the jaw. Integrating the results of masticatory movements, occlusal tooth wear, infraorbital foramen size, and body mass estimations (90.2 g for G. pattersoni and 216.3 g for G. minoprioi), we suggest an omnivorous diet with a preference for plant material, like that characterizing living potoroids. [ABSTRACT FROM AUTHOR]

The Stagodontidae include the largest metatherians known from the Cretaceous of North America. Of the recognized species of the stagodontid genus Eodelphis, E. cutleri is larger and has a more robust dentary, more inflated premolars, and third premolars specialized for crushing, as opposed to the more gracile E. browni. These differences have led to the hypothesis that an E. cutleri-like ancestor gave rise to Didelphodon—another, mostly younger, stagodontid, which has been interpreted as a durophagous predator-scavenger. If correct, E. cutleri would be expected to show more morphological adaptation toward durophagy than E. browni does. Here, we describe two new dentary fossils referable to E. browni and test the evolutionary hypothesis by applying beam theory to estimate bending force capabilities of 22 dentaries of Cretaceous stagodontids and other metatherians. The resulting diversity of bending force profiles of the sampled dentaries implies that Cretaceous metatherians had a wide range of feeding behaviors. Among the stagodontids, E. cutleri has a mediolateral bending force profile of the dentary that is more similar to that of Didelphodon than it is to that of E. browni; whereas its dorsoventral bending force profile is more similar to that of E. browni. These results indicate that anteriorly the dentary of E. cutleri was capable of resisting high torsional stresses from hard-object feeding but lacked other dorsoventral buttressing associated with exceptionally high bite forces of Didelphodon. Our results imply that some morphological changes associated with durophagy evolved twice within this clade, independently in E. cutleri and Didelphodon. [ABSTRACT FROM AUTHOR]

Mammals and birds provide food for their young after birth, but such provisioning is almost absent in other vertebrates. A recent theory suggested that, in addition to thermoregulation, the large discrepancy in size between adult and young ectothermic vertebrates precludes them from providing for their young, whereas the relatively large offspring of endotherms are easier to provision. I show here that reptile neonates and hatchlings are as large as those of mammals and birds. Differences in size between adults and young thus cannot explain the lack of parental provisioning in reptiles. I suggest that the large size at birth is the ancestral condition in amniotes as a whole and that provisioning has thus evolved after endothermy. [ABSTRACT FROM AUTHOR]

Carolocoutoia ferigoloi is one of the largest metatherians of the Itaboraí fauna (Early Eocene, Southeastern Brazil). It was originally identified from a single upper molar with a markedly bunodont crown, wrinkled enamel, and a robust protocone. Here, we describe a nearly complete right dentary of C. ferigoloi with the alveoli of the premolars and first lower molar, a very worn second lower molar, complete third and fourth lower molars, and a right second upper molar. Carolocoutoia differs from other protodidelphids in having inflated, conical trigonid cusps, a more flattened entoconid, a developed entocristid, and a supernumerary cusp labial to the entoconid. Carolocoutoia was recovered in our phylogenetic analysis as the sister taxon of Protodidelphis), since both share the presence of an anteriorly recurved dentary, wrinkled enamel, and a sinuous crest between stylar cusps B and D. The inflated, conical trigonid cusps of Carolocoutoia represent an evolutionary convergence with other South American Paleogene mammals, such as some ungulates, and the polydolopimorphian Roberthoffstetteria. We also present the second record of a pathology (molar extrusion) in a metatherian from Itaboraí. Based on its molar crown morphology, Carolocoutoia ferigoloi was a specialized frugivorous metatherian. The occurrence of a specialized frugivorous protodidelphid in the Itaboraí fauna is in line with the well-established increase in global temperatures and the expansion of tropical forests after the Paleocene-Eocene Thermal Maximum (around 55.5–55.3 million years ago). • The jaw and lower molars of Carolocoutoia ferigoloi are presented. • Carolocoutoia ferigoloi was a specialized frugivore. • Carolocoutoia ferigoloi was the second largest didelphimorphian known so far. • The second record of paleopathology (molar extrusion) in an Itaboraian metatherian is presented. • The first detailed comparison between the dentition and jaw of large bunodont metatherians and Eocene ungulates is presented. [ABSTRACT FROM AUTHOR]

Zeusdelphys complicatus is one of the most enigmatic metatherians from the Itaboraí Basin. The type and only known specimen was previously regarded as the upper dentition of Eobrasilia; an M4 of a new taxon; an M3 of a Kollpaniidae (now regarded as a group of “condylarths”); a probable M1 of an incertae sedis taxon; and as an M1 of a Protodidelphidae. Herein, we present a morphological review of the dental structures of Zeusdelphys complicatus, presenting new interpretations and comparing it with other North and South American taxa. We also perform a phylogenetic analysis in order to test the affinities of Zeusdelphys and the validity of most studied characters. The results recovered Zeusdelphys complicatus as more closely related to Hatcheritherium alpha than to any other metatherian. Glasbiidae were recovered as the sister lineage of Protodidelphidae within Didelphimorphia, as true marsupials. Ectocentrocristus was recovered as the sister taxon of Zeusdelphys + Hatcheritherium, as a Hatcheriformes. The analysis recovered this suborder as an independent lineage from Polydolopimorphia, being more closely related to “Alphadontidae”. The affinities with Protodidelphidae are a result of convergent evolution, as Zeusdelphys is more closely related to Hatcheritherium alpha from the Late Cretaceous of North America. The results support a North American origin for Hatcheriformes. The presence of strong sea-level lowstands and islands in the Caribbean Plate during the Late Cretaceous provide valid data to support a faunal interchange between Americas during the latest Late Cretaceous. Based on the results, Zeusdelphys represents a South American early Eocene surviving Hatcheriformes.

The northernmost record of Metatheria, Unnuakomys hutchisoni gen. et sp. nov., is described from the Pediomys Point locality in Upper Cretaceous (lower Maastrichtian) strata of the Prince Creek Formation cropping out along the Colville River on the North Slope of Alaska, USA (70°N). Based on over 60 specimens (including tooth-bearing dentaries and a maxillary fragment), the new taxon is unusual in having two well-developed stylar cusps in the C position flanking the deepest part of the ectoflexus. To examine the relationship between U. hutchisoni and other metatherians, U. hutchisoni was scored into the taxon character matrix of other studies. Our results corroborate prior studies that suggest the new Alaskan pediomyid. However, in contrast to other studies, we do not recover a sister-group relationship between U. hutchisoni and Pediomys elegans. Rather, our study suggests that U. hutchisoni is more closely allied with Aquilan species Iqualadelphis lactea and ?Aquiladelphis laurae. Teeth of U. hutchisoni greatly outnumber those recovered from other mammals at Pediomys Point, like Late Cretaceous localities in the Western Interior where metatherians are among the most abundant mammalian fossils. However, what differs between Late Cretaceous mid-latitude localities and the assemblage from the North Slope of Alaska is metatherian richness. Whereas other studies have reported up to a dozen species of metatherians from Late Cretaceous mid-latitude North American assemblages, to date all the metatherian teeth collected from Pediomys Point appear to belong to just U. hutchisoni. A sampling bias may play a role in this pattern. This can be tested through additional collection from the Prince Creek Formation. However, the abundance of U. hutchisoni at Pediomys Point implies that this tiny metatherian thrived in an environment well above the Arctic Circle whose climatic extremes may have acted as a biogeographical filter to other metatherians. As the first mammal to be described from the Prince Creek Formation, U. hutchisoni provides support for the existence of a northern high-latitude early Maastrichtian faunal province identified by others on the basis of its distinctive dinosaurian fauna – the Paaŋaqtat Province. [ABSTRACT FROM AUTHOR]

• Monotremes have a lower cortical white matter volume compared to therians. • This suggests fewer cortical association fibres in monotremes compared to therians. • Cortical white matter is shifted caudally in the platypus and long-beaked echidna. • Forebrain structure in monotremes suggests convergence with myrmecophagous xenarthrans. We have made quantitative volumetric analyses of cerebral cortical (pallial) structures in the brains of three species of monotreme (Ornithorhynchus anatinus , Tachyglossus aculeatus , Zaglossus bruijni) and compared the findings with similar measurements in a range of therian mammals (6 marsupials and 50 placentals). We have found that although the iso- and periallocortical grey matter volume of the monotremes is about what would be expected for their brain size, the proportion of iso- and periallocortical white matter in monotremes is substantially lower than that in the forebrains of therians. This suggests that the forebrains of the three monotremes have fewer association, commissural and/or projection connections than those of similarly sized forebrains of therian mammals. We also found that the iso- and periallocortex of the platypus is relatively smooth-surfaced compared to similarly sized brains of therian mammals, with a distinct caudal shift in the positioning of cortical white matter in the forebrain, consistent with expansion of the posterior thalamic radiation. Central laminated olfactory structures (anterior olfactory nucleus and piriform cortex) are large in the tachyglossid monotremes (Tachyglossus aculeatus and Zaglossus bruijni) and large in xenarthran placental mammals, suggesting convergence of the forebrain structure of monotreme formivores with that of similarly specialized therians like the xenarthrans Myrmecophaga tridactyla and Dasypus novemcinctus. [ABSTRACT FROM AUTHOR]

Marsupials and their fossil relatives, which collectively comprise Metatheria, have been of scientific interest for centuries, with many aspects of their evolution and systematics subject to intense research and debate. Here, we review progress over the last 25 years, which has included the description of many new species (modern and fossil), and major improvements in understanding of their phylogenetic relationships, as well as the overall evolutionary history and biogeography of Marsupialia (crown-clade) and Metatheria (total-clade). Significant advances have included the deployment of increasingly sophisticated molecular, morphological, and total evidence analyses, which have resolved most previously disputed relationships among and within the modern marsupial orders. A broad systematic consensus is now emerging, although several major areas of contention remain, particularly among fossil metatherians. New modern species continue to be described at an impressive rate, with almost 50 named in the last 25 years, and many more await discovery. There has also been an explosion in the discovery and description of fossil marsupials and non-marsupial metatherians (~270 species), principally from Australasia and the Americas but also from Antarctica, Europe, and Asia. Most are represented by dental specimens only, but some consist of complete and well-preserved material, which has led to major improvements in our understanding of the evolution of cranial and postcranial morphology. Improvements in the fossil record and advances in methods for inferring divergence times have helped clarify when and where key events occurred in metatherian evolution, and the patterns of subclade diversification. We also have improved understanding of biogeographical relationships among metatherians on different landmasses. Despite enormous progress, numerous key uncertainties remain due to major gaps in the fossil record (e.g. Antarctica, Late Cretaceous, and early Paleogene of Australia) and a comparative lack of studies that directly combine molecular and fossil data. Future advances will largely depend on improvements in the fossil record and studies that better integrate neontological and paleontological evidence. [ABSTRACT FROM AUTHOR]

The Quebrada de Los Colorados Formation (Los Cardones National Park, Salta Province, north-western Argentina), is an Eocene--Oligocene unit well represented in the Calchaquí Valley area. Here we describe a new metatherian association recorded from the base of this formation, inferred as middle Eocene. Represented taxa are: Sparassodonta, family indet.: Patene simpsoni; Polydolopimorphia, Bonapartheriiformes, Argyrolagoidea: family, genus, and species indet.; and Bonapartherioidea, Prepidolopidae: Punadolops alonsoi and Coloradolops cardonensis gen. et sp. nov. Patene simpsoni is also found in the Tonco Valley, near Los Cardones, and at São José de Itaboraí, Rio de Janeiro, Brazil. Punadolops alonsoi was originally described from the Geste Formation in Salta and Catamarca provinces. Hitherto, no other Argyrolagoidea have been found in north-western Argentina in the Palaeogene. Coloradolops cardonensis is unique to the locality and levels here described. The preservation of part of the skull constitutes the best prepidolopid remains known. North-western Argentina is a key region for the study of the evolution of South American mammals, since it has a singular geographical location between the Neotropics and the southernmost part of South America. Due to biogeographical constraints, it may lead to a better comprehension of the continental distribution of metatherian lineages during Cenozoic times. [ABSTRACT FROM AUTHOR]

The late Cenozoic (late Miocene-Pliocene) rocks of Catamarca Province, Argentina have produced one of the most diverse records of late Cenozoic carnivorous metatherians in South America, with at least six previously recognized species of sparassodonts and carnivorously specialized didelphids. Here, we report the presence of a seventh carnivorous metatherian in Catamarca Province based on FMNH P15230, a specimen collected by the Field Museum of Natural History's 1926-7 Second Marshall Field Paleontological Expedition. Although fragmentary, this specimen cannot be referred to any taxon previously described from northwestern Argentina. This specimen exhibits anterolateral maxillary foramina, nasolacrimal contact, numerous accessory foramina on the surface of the palate, and very small P1-2 that are similar in size and have no diastema between them. This combination of features suggests it most likely represents a small (∼2 kg) sparassodont but does not preclude referral to the carnivorous didelphid Hyperdidelphys dimartinoi. Specimen FMNH P15230 increases the number of sparassodont lineages known from the late Cenozoic of South America and helps clarify the tempo and mode of the group's decline during this interval. • We report a seventh metatherian carnivore from the late Cenozoic Santa Maria group. • Material is fragmentary, but distinct from all other taxa from the region. • The material pertains to a small-bodied, short snouted sparassodont. • These types of sparassodonts are nearly unknown from the late Miocene/Pliocene. • Suggests presence of an additional metatherian carnivore lineage just prior to GABI. [ABSTRACT FROM AUTHOR]

Abstract The Protodidelphidae was a group of marsupials that lived in Gondwana from the early to middle Eocene. Among South American faunas, the Itaboraí Basin calls attention by the presence of four genera and six species. Herein is described Bergqvistherium primigenia gen. et sp. nov., a new protodidelphid from the Itaboraí Basin - lower Eocene. This taxon differs from other protodidelphids in the smaller size, developed entocristid, less brachyo-bunoid adaptations, and entoconid more mesial than the hypoconid. These characters are recovered as plesiomorphies of the Protodidelphidae, supporting Bergqvistherium as an early-divergent lineage of this group. The Protodidelphidae fauna of the Itaboraí Basin is represented by less specialized “basal” taxa, such as Bergqvistherium and Periprotodidelphis; and more specialized apical taxa, such as Guggenheimia, Protodidelphis, and Carolocoutoia. This result indicates that the diversification of apical protodidelphids probably was a result of a relatively short-time event, occurring during the early Eocene. This evolutionary event can be directly correlated to the increase in the temperatures and the extension of tropical forests resulted by the Paleocene-Eocene Thermal Maximum during the Itaboraiense time span. The study supported a Late Cretaceous origin for the Protodidelphidae, which agrees with molecular studies for the Didelphimorphia.

Zeusdelphys complicatus is one of the most enigmatic metatherians from the Itaboraí Basin. The type and only known specimen was previously regarded as the upper dentition of Eobrasilia; an M4 of a new taxon; an M3 of a Kollpaniidae (now regarded as a group of "condylarths"); a probable M1 of an incertae sedis taxon; and as an M1 of a Protodidelphidae. Herein, we present a morphological review of the dental structures of Zeusdelphys complicatus, presenting new interpretations and comparing it with other North and South American taxa. We also perform a phylogenetic analysis in order to test the affinities of Zeusdelphys and the validity of most studied characters. The results recovered Zeusdelphys complicatus as more closely related to Hatcheritherium alpha than to any other metatherian. Glasbiidae were recovered as the sister lineage of Protodidelphidae within Didelphimorphia, as true marsupials. Ectocentrocristus was recovered as the sister taxon of Zeusdelphys + Hatcheritherium, as a Hatcheriformes. The analysis recovered this suborder as an independent lineage from Polydolopimorphia, being more closely related to "Alphadontidae". The affinities with Protodidelphidae are a result of convergent evolution, as Zeusdelphys is more closely related to Hatcheritherium alpha from the Late Cretaceous of North America. The results support a North American origin for Hatcheriformes. The presence of strong sea-level lowstands and islands in the Caribbean Plate during the Late Cretaceous provide valid data to support a faunal interchange between Americas during the latest Late Cretaceous. Based on the results, Zeusdelphys represents a South American early Eocene surviving Hatcheriformes. [ABSTRACT FROM AUTHOR]

Paucituberculatan marsupials, particularly members of the family Palaeothentidae, were important components of South American mammal communities during much of the Cenozoic. However, after the late early Miocene, palaeothentid remains are rare in the fossil record, and the group is last recorded at late middle Miocene sites in Colombia, Bolivia and possibly Argentina. Here, we describe new specimens of palaeothentids from one of these late middle Miocene sites, Quebrada Honda, Bolivia, which include: (1) the first described lower dentitions ofAcdestis maddeni, which exhibit distinctive features such as a greatly elongated paracristid and a single-rooted m4; (2) the first described late middle Miocene palaeothentines, representing two new species ofPalaeothentes,P. serratussp. nov. andP. relictussp. nov., distinguished from other species ofPalaeothentesby the presence of an anterobasal cingulid and reduced anterior trigonid crest, among other features; and (3) remains of a third new species,Chimeralestes ambiguusgen. et sp. nov., distinguished from other palaeothentids by its combination of a labially positioned cristid obliqua, reduced m4, and sharply curved entocristid. Phylogenetic and palaeoecological analyses show that Quebrada Honda palaeothentids were taxonomically and morphologically diverse and likely spanned a wide range of ecological niches. Combined with the wide geographical distribution of palaeothentoids during the late middle Miocene, this suggests that the disappearance of these marsupials was preceded by an abrupt rather than gradual decline in taxonomic and ecological diversity as well as geographical range. http://zoobank.org/urn:lsid:zoobank.org:pub:DA7E10BA-7203-4F5A-A3AB-F0E7352B101C [ABSTRACT FROM AUTHOR]

Two centuries ago, Georges Cuvier, the father of vertebrate palaeontology, described an almost complete skeleton of a small 'opossum' from the Montmartre Gypsum (late Eocene): Peratherium cuvieri. His description of the visible bones remains famous, as it was an unequivocal demonstration of his principle of correlation of parts. With the state-of-the-art technology of X-ray microtomography (computed tomography scanning), it is now possible to extend the investigation of the Cuvier's 'opossum', one of the most iconic specimens of the Muséum national d'Histoire naturelle (MNHN). Beneath the visible upper cheek teeth the skull is damaged and fragmented, but provides significant new data, with the most complete and informative structures being the paired petrosal bones. Comparisons with the didelphid Marmosa murina (Linnaeus, 1758) and three other fossil herpetotheriids [Amphiperatherium minutum Aymard, 1846, Herpetotherium cf. fugax Cope, 1873, and Peratherium elegans (Aymard, 1846)] suggest that dental features alone are not sufficient to discriminate between the different species, being based on highly variable, polymorphic features of the stylar shelf. The anatomy of the petrosal bone, which has yet to be described for P. elegans or A. minutum, reveals marked differences between P. cuvieri and H. cf. fugax, however, which brings into question the monophyly of Herpetotheriidae. Further investigation of petrosal characters for herpetotheriids would therefore shine new light on the phylogenetic affinities of Herpetotheriidae, in terms of both the relationships within the family and the position of Herpetotheriidae within Metatheria as a whole. [ABSTRACT FROM AUTHOR]