Food habits of Metachirus nudicaudatus and Didelphis aurita were investigated through fecal analysis. Fecal samples were collected in a Restinga forest of southeastern Brazil. Both marsupials feed chiefly on soil invertebrates, while small vertebrates and fruits are eaten occasionally. D. aurita eats more fruits than M. nudicaudatus, and shows a significantly higher diversity index of invertebrates in its diet. M. nudicaudatus feeds more on arthropods, showing a narrower prey utilization than D. aurita. Resume. -Nous avons etudie le regime alimentaire de Metachirus nudicaudatus et Didelphis aurita par analyse du contenu des crottes. Les echantillons fecaux ont ete recoltes dans une foret de Restinga au sud-est du Bresil. Les deux marsupiaux se nourrissent principalement d'invertebres du sol, tandis que des petits vertebres et des fruits sont ingeres occasionnellemerit. D. aurita ingere plus de fruits que M. nudicaudatus et presente un indice de diversite de son regime alimentaire significativement superieur. M. nudicaudatus se nourrit plus d'arthropodes, et presente une utilisation de proies plus etroite que D. aurita.

The New World family Didelphidae, the basal lineage within marsupials, is commonly viewed as morphologically conservative, yet includes aquatic, terrestrial, scansorial, and arboreal species. Here, I quantitatively estimated the existing variability in size and shape of the Didelphidae scapula (1076 specimens from 56 species) using geometric morphometrics, and compared size and shape differences to evolutionary and ecologic distances. I found considerable variation in the scapula morphology, most of it related to size differences between species. This results in morphologic divergence between different locomotor habits in larger species (resulting from increased mechanical loads), but most smaller species present similarly shaped scapulae. The only exceptions are the water opossum and the short-tailed opossums, and the functional explanations for these differences remain unclear. Scapula size and shape were mapped onto a molecular phylogeny for 32 selected taxa and ancestral size and shapes were reconstructed using squared-changed parsimony. Results indicate that the Didelphidae evolved from a medium-to small-sized ancestor with a generalized scapula, slightly more similar to arboreal ones, but strikingly different from big-bodied present arboreal species, suggesting that the ancestral Didelphidae was a small scansorial animal with no particular adaptations for arboreal or terrestrial habits, and these specializations evolved only in larger-bodied clades.K E Y W O R D S : Locomotion, marsupials, morphological evolution, shoulder girdle.

Xenarthrans—anteaters, sloths, and armadillos—have essential functions for ecosystem maintenance, such as insect control and nutrient cycling, playing key roles as ecosystem engineers. Because of habitat loss and fragmentation, hunting pressure, and conflicts with domestic dogs, these species have been threatened locally, regionally, or even across their full distribution ranges. The Neotropics harbor 21 species of armadillos, 10 anteaters, and 6 sloths. Our data set includes the families Chlamyphoridae (13), Dasypodidae (7), Myrmecophagidae (3), Bradypodidae (4), and Megalonychidae (2). We have no occurrence data on Dasypus pilosus (Dasypodidae). Regarding Cyclopedidae, until recently, only one species was recognized, but new genetic studies have revealed that the group is represented by seven species. In this data paper, we compiled a total of 42,528 records of 31 species, represented by occurrence and quantitative data, totaling 24,847 unique georeferenced records. The geographic range is from the southern United States, Mexico, and Caribbean countries at the northern portion of the Neotropics, to the austral distribution in Argentina, Paraguay, Chile, and Uruguay. Regarding anteaters, Myrmecophaga tridactyla has the most records (n = 5,941), and Cyclopes sp. have the fewest (n = 240). The armadillo species with the most data is Dasypus novemcinctus (n = 11,588), and the fewest data are recorded for Calyptophractus retusus (n = 33). With regard to sloth species, Bradypus variegatus has the most records (n = 962), and Bradypus pygmaeus has the fewest (n = 12). Our main objective with Neotropical Xenarthrans is to make occurrence and quantitative data available to facilitate more ecological research, particularly if we integrate the xenarthran data with other data sets of Neotropical Series that will become available very soon (i.e., Neotropical Carnivores, Neotropical Invasive Mammals, and Neotropical Hunters and Dogs). Therefore, studies on trophic cascades, hunting pressure, habitat loss, fragmentation effects, species invasion, and climate change effects will be possible with the Neotropical Xenarthrans data set. Please cite this data paper when using its data in publications. We also request that researchers and teachers inform us of how they are using these data.

The ways in which the taxonomic differences in morphology, behavior or life history relate to each other have been used regularly to test ideas about the selective forces involved in their evolution. Canid species vary significantly in diet, hunting techniques, sociality and cranial morphology. The main goal of this study is to test and explore the possible correlation between bite force and brain volume in canids. For that, we calculated the bite force based on the beam theory, and the brain volume based on three cranial measurements. The species with biggest values of bite force quotient (BFQ) were Speothos venaticus (162.25), Cuon alpinus (129.24) and Lycaon pictus (124.41) due to several adaptations acquired along with hypercarnivory. Species with the highest values of brain volume quotient (BVQ) were S. venaticus, Cu. alpinus and L. pictus with, respectively, 141.35, 139.01 and 131.61, possibly due to the same adaptations that resulted in their bigger BFQ. The highest values of bite force belonged to Canis lupus (830.51 Pa), L. pictus (719.03 Pa) and Ca. rufus (530.52 Pa) and the smallest values belong to Urocyon littoralis (98.14 Pa), Vulpes macrotis (92.53 Pa) and V. zerda (72.6 Pa). Ca. lupus, L. pictus and Chrysocyon brachyurus possess the largest brain volumes with respectively 159.29, 146.94 and 120.84 mm3 and the smallest values belong to Nyctereutes procyonoides (28.2 mm3), V. rueppelli (27.86 mm3) and V. zerda (20.65 mm3). The independent contrasts correlation showed that there is no correlation between BVQ and BFQ (r = 0.14/P = 0.46), as well as no correlation between BFQ and BF (r = 0.22/P = 0.26), which indicates the efficiency of the size correction. Bite force and brain volume estimates are much higher in the group hunting hypercarnivores (Lycaon, Cuon and Speothos) and only these showed correlation between BFQ and BVQ. Our results indicate that cranial adaptations for hypercarnivory also influence braincase size.

Natural diets of Didelphidae species vary in the amounts of invertebrates, fruits and small vertebrates eaten. We investigated the digestive morphology of ten species of didelphid marsupials varying in food habits. The purpose was to describe and to compare the shape and relative size of the digestive tract portions among species studied and relate them to food habits. The form of the gastrointestinal tract in this family is simple, with a unilocular stomach, small intestine, large intestine and caecum.