The principles of classification and a classification of mammals. Bulletin of the AMNH ; v. 85

Bones of recent mammals in the Amboseli Basin, southern Kenya, exhibit distinctive weathering characteristics that can be related to the time since death and to the local conditions of temperature, humidity and soil chemistry. A categorization of weathering characteristics into six stages, recognizable on descriptive criteria, provides a basis for investigation of weathering rates and processes. The time necessary to achieve each successive weathering stage has been calibrated using known-age carcasses. Most bones decompose beyond recognition in 10 to 15 yr. Bones of animals under 100 kg and juveniles appear to weather more rapidly than bones of large animals or adults. Small-scale rather than widespread environmental factors seem to have greatest influence on weathering characteristics and rates. Bone weathering is potentially valuable as evidence for the period of time represented in recent or fossil bone assemblages, in- cluding those on archeological sites, and may also be an important tool in censusing populations of animals in modern ecosystems.

Taphonomic and Ecologic Information Form Bone Weathering

Sea anemones are seemingly primitive animals that, along with corals, jellyfish, and hydras, constitute the oldest eumetazoan phylum, the Cnidaria. Here, we report a comparative analysis of the draft genome of an emerging cnidarian model, the starlet sea anemone Nematostella vectensis. The sea anemone genome is complex, with a gene repertoire, exon-intron structure, and large-scale gene linkage more similar to vertebrates than to flies or nematodes, implying that the genome of the eumetazoan ancestor was similarly complex. Nearly one-fifth of the inferred genes of the ancestor are eumetazoan novelties, which are enriched for animal functions like cell signaling, adhesion, and synaptic transmission. Analysis of diverse pathways suggests that these gene "inventions" along the lineage leading to animals were likely already well integrated with preexisting eukaryotic genes in the eumetazoan progenitor.

/pdf/sea-anemone-genome-reveals-ancestral-eumetazoan-gene-4vh8gvrltz.pdf

Sea Anemone Genome Reveals Ancestral Eumetazoan Gene Repertoire and Genomic Organization

To discover interordinal relationships of living and fossil placental mammals and the time of origin of placentals relative to the Cretaceous-Paleogene (K-Pg) boundary, we scored 4541 phenomic characters de novo for 86 fossil and living species. Combining these data with molecular sequences, we obtained a phylogenetic tree that, when calibrated with fossils, shows that crown clade Placentalia and placental orders originated after the K-Pg boundary. Many nodes discovered using molecular data are upheld, but phenomic signals overturn molecular signals to show Sundatheria (Dermoptera + Scandentia) as the sister taxon of Primates, a close link between Proboscidea (elephants) and Sirenia (sea cows), and the monophyly of echolocating Chiroptera (bats). Our tree suggests that Placentalia first split into Xenarthra and Epitheria; extinct New World species are the oldest members of Afrotheria.

http://science.sciencemag.org/content/sci/339/6120/662.full.pdf

The Placental Mammal Ancestor and the Post–K-Pg Radiation of Placentals

Walker's Mammals of the World, 4th Edition, Ronald M. Nowak, John L. Paradiso. The Johns Hopkins University Press, Baltimore, Maryland (1983), 1xi, +1-568 (Vol. I), xxv+569-1362 (Vol. II). Price $65.00

Comparative genomic data among organisms allow the reconstruction of their phylogenies and evolutionary time scales. Molecular timings have been recently used to suggest that environmental global change have shaped the evolutionary history of diverse terrestrial organisms. Living xenarthrans (armadillos, anteaters and sloths) constitute an ideal model for studying the influence of past environmental changes on species diversification. Indeed, extant xenarthran species are relicts from an evolutionary radiation enhanced by their isolation in South America during the Tertiary era, a period for which major climate variations and tectonic events are relatively well documented. We applied a Bayesian approach to three nuclear genes in order to relax the molecular clock assumption while accounting for differences in evolutionary dynamics among genes and incorporating paleontological uncertainties. We obtained a molecular time scale for the evolution of extant xenarthrans and other placental mammals. Divergence time estimates provide substantial evidence for contemporaneous diversification events among independent xenarthran lineages. This correlated pattern of diversification might possibly relate to major environmental changes that occurred in South America during the Cenozoic. The observed synchronicity between planetary and biological events suggests that global change played a crucial role in shaping the evolutionary history of extant xenarthrans. Our findings open ways to test this hypothesis further in other South American mammalian endemics like hystricognath rodents, platyrrhine primates, and didelphid marsupials.

/pdf/influence-of-tertiary-paleoenvironmental-changes-on-the-3x730kn5r2.pdf

Influence of Tertiary paleoenvironmental changes on the diversification of South American mammals: a relaxed molecular clock study within xenarthrans

In this paper a data base is initiated, with the body mass estimations for a number of xenarthran and epitherian species of the Lujanian Land Mammal Age (late Pleis- tocene - early Holocene of South America). For doing that, a set of allometric equations was used, which had been previously developed from craniodental and limb bone dimensions in modern mammals. The results were analysed statistically. The dispersion of body mass estimations was remarkable in the totally extinct xenarthran groups. Certain measurements (particularly, the posterior jaw length in glyptodonts and the transverse diameter of the femur in ground sloths) gave spurious predictions relative to non-xenarthran mammals. New equa- tions specifically for xenarthrans should be developed to use these measurements. The dispersion of the epitherian mammals was lower than in the studied xenarthran. It is sug- gested that arithmetic mean should be used in those studies in which large size is the conservative hypothesis, and another statistic (such as the geometric mean, median or mode) in the opposite case. This database is intended to be the starting point for many autecological and synecological studies of this extinct fauna.

Body mass estimations in lujanian (late pleistocene-early holocene of south america) mammal megafauna

Caviomorph rodents (Rodentia: Caviomorpha) are an anatomically variable group with diverse ecological and morphological types, including cursorial, digging, fossorial and swimming forms. Their appendicular skeleton is rather generalized and extreme modifications or reductions in the long bones of limbs are not present. It is of special interest to evaluate functional adaptive variations of the appendicular skeleton within this group. Although much work has been devoted to study structure, function, and kinematics of legs in mammals, most studies do not consider particular functions and behaviour within different mammalian lineages. Morphometric and biomechanical studies were performed to test the relationship between adaptation and morphology of the bones of the proximal and middle limb segments in terrestrial caviomorph rodents. Fifty-four specimens belonging to 10 species with different limb adaptations and representing a wide range of body sizes were measured. Diameters and functional lengths of long bones were taken and nine functional indices were built. Humerus (HRI) and ulna (URI) robustness, humerus deltoid (SMI) and epicondyle (EI) development, olecranon proportion (IFA), femur (FRI) and tibia (TRI) robustness, and gluteal muscle insertion at femur (GI), were calculated. Only TRI and, to a lesser degree, SMI and EI, were significantly related to body mass. A functional sequence (cursorial–generalized–occasional digging–diggers) which seems to reflect an increase in force and muscular development in middle segments of the fore limb is recognized. The hind limb shows a decrease in the speed efficiency of the femur and an increase in limb robustness in the transition from cursorial to digging forms. Although overlapping of speed and force functions in the limbs is evident, functional differentiation for speed in the proximal, and force in the middle segments can be inferred.

Limb proportions and adaptations in caviomorph rodents (Rodentia: Caviomorpha)

Armadillos are a very diverse group ranging from non-fossorial Tolypeutini through to the powerful diggers like the giant armadillo Priodontes maximus to the totally subterranean Chlamyphorini. A previous study demonstrated a close relationship between the relative length of the olecranon of the ulna (index of fossorial ability, IFA) and the fossorial ability of armadillos. This study examines a wide range of limb proportions to explore the biomechanical correlates with fossorial ability. The study demonstrates that the indices of the forelimb (brachial index, shoulder moment index and IFA) do correlate well with digging habits, but also reveals some interesting exceptions, particularly in the most fossorial and most cursorial forms. On the other hand, the hindlimb indices apparently do not correlate with digging habits, but seem to be influenced more by body size. The correlations among the forelimb indices are quite strong and positive but correlations between forelimb and hindlimb indices are negative or very low. It is apparent that there is still much to be learned about structure and function in armadillos.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/8E34B81AF0018A2ED11C66DABA36ACF8/S0952836902000717a.pdf/div-class-title-structure-and-function-in-armadillo-limbs-mammalia-xenarthra-dasypodidae-div.pdf

Structure and function in armadillo limbs (Mammalia: Xenarthra: Dasypodidae)

51 (3): 407–422.The paleoecology of the South American fossil carnivores has not been as well studied as that of their northern relatives.One decade ago Farina suggested that the fauna of Rio Lujan locality (Argentina, late Pleistocene–early Holocene) is notbalanced because the metabolic requirements of the large carnivores are exceeded by the densities and biomass of thelarge herbivores. This conclusion is based on the calculation of densities using allometric functions between body massand population abundance, and is a consequence of low carnivore richness

https://www.app.pan.pl/archive/published/app51/app51-407.pdf

Sergio F. Vizcaíno

Papers

Influence of Tertiary paleoenvironmental changes on the diversification of South American mammals: a relaxed molecular clock study within xenarthrans

Body mass estimations in lujanian (late pleistocene-early holocene of south america) mammal megafauna

Limb proportions and adaptations in caviomorph rodents (Rodentia: Caviomorpha)

Structure and function in armadillo limbs (Mammalia: Xenarthra: Dasypodidae)

Paleoecology of the large carnivore guild from the late Pleistocene of Argentina