Iterative Evolution of Sympatric Seacow (Dugongidae, Sirenia) Assemblages during the Past ∼26 Million Years

Extant sirenians show allopatric distributions throughout most of their range. However, their fossil record shows evidence of multispecies communities throughout most of the past ∼26 million years, in different oceanic basins. Morphological differences among co-occurring sirenian taxa suggest that resource partitioning played a role in structuring these communities. We examined body size and ecomorphological differences (e.g., rostral deflection and tusk morphology) among sirenian assemblages from the late Oligocene of Florida, early Miocene of India and early Pliocene of Mexico; each with three species of the family Dugongidae. Although overlapping in several ecomorphological traits, each assemblage showed at least one dominant trait in which coexisting species differed. Fossil sirenian occurrences occasionally are monotypic, but the assemblages analyzed herein show iterative evolution of multispecies communities, a phenomenon unparalleled in extant sirenian ecology. As primary consumers of seagrasses, these communities likely had a strong impact on past seagrass ecology and diversity, although the sparse fossil record of seagrasses limits direct comparisons. Nonetheless, our results provide robust support for previous suggestions that some sirenians in these extinct assemblages served as keystone species, controlling the dominance of climax seagrass species, permitting more taxonomically diverse seagrass beds (and sirenian communities) than many of those observed today

Inactivation of thermogenic UCP1 as a historical contingency in multiple placental mammal clades

Mitochondrial uncoupling protein 1 (UCP1) is essential for nonshivering thermogenesis in brown adipose tissue and is widely accepted to have played a key thermoregulatory role in small-bodied and neonatal placental mammals that enabled the exploitation of cold environments. We map ucp1 sequences from 133 mammals onto a species tree constructed from a ∼51-kb sequence alignment and show that inactivating mutations have occurred in at least 8 of the 18 traditional placental orders, thereby challenging the physiological importance of UCP1 across Placentalia. Selection and timetree analyses further reveal that ucp1 inactivations temporally correspond with strong secondary reductions in metabolic intensity in xenarthrans and pangolins, or in six other lineages coincided with a ∼30 million-year episode of global cooling in the Paleogene that promoted sharp increases in body mass and cladogenesis evident in the fossil record. Our findings also demonstrate that members of various lineages (for example, cetaceans, horses, woolly mammoths, Steller's sea cows) evolved extreme cold hardiness in the absence of UCP1-mediated thermogenesis. Finally, we identify ucp1 inactivation as a historical contingency that is linked to the current low species diversity of clades lacking functional UCP1, thus providing the first evidence for species selection related to the presence or absence of a single gene product

The myology of the Amazonian Manatee, Trichechus inunguis (Natterer) (Mammalia: Sirenia)

ABSTRACTThe muscles of the Amazonian manatee are described and compared with those of other manatees and the dugong. Maps of muscle attachments and data on weights of muscles are included. The manatee species differ in the forms of the mm. rectus capitis lateralis and biceps brachii. The mechanisms of protrusion of upper-lip bristles and opening of the nostrils are described. The jaw apparatus is uniquely specialized, with a very large temporalis muscle constituting more than half the adductor muscle mass, and development of a joint between the pterygoid process and the mandible which probably braces the mandible during transverse chewing. The center of mandibular rotation in transverse chewing probably lies posteromedial to the pterygoid process on the active sidethe contralateral temporalis is dominant in transverse chewing. Trichechus inunguis is more specialized for surface-feeding and for swimming than T. manotus.: Os músculos do peixe-boi da Amazônia são descritos e comparados àqueles dos outros peixes-bois e do dugong. Mapas das ligações dos músculos aos ossos, e dados sobre pesos dos músculos, são incluídos. Notam-se diferenças entre as espécies de peixes-bois com respeito aos músculos rectus capitis lateralis e biceps brachii. Descrevem-se o mecanismo de protrusão das cerdas do lábio superior, e o mecanismo de abertura das narinas. O aparelho masticatório é unicamente especializado, com um temporalis muito grande, constituindo mais que metade do peso dos músculos adutores, e com uma articulação entre o processo pterigoídeo e a mandíbula. Esta provavelmente apoia a mandíbula na mastigação transversal. O centro de rotação da mandíbula na mastigação transversal parece ficar posteromedial ao processo pterigoídeo no lado ativo; o temporalis do outro lado fornece a maioria da força para esta rotação. O Trichechus inunguis é mais especializado do que o T. manatus para se alimentar perto da superfície da água, e para nadar

Empty forest or empty rivers? A century of commercial hunting in Amazonia

The Amazon basin is the largest and most species-rich tropical forest and river system in the world, playing a pivotal role in global climate regulation and harboring hundreds of traditional and indigenous cultures. It is a matter of intense debate whether the ecosystem is threatened by hunting practices, whereby an “empty forest” loses critical ecological functions. Strikingly, no previous study has examined Amazonian ecosystem resilience through the perspective of the massive 20th century international trade in furs and skins. We present the first historical account of the scale and impacts of this trade and show that whereas aquatic species suffered basin-wide population collapse, terrestrial species did not. We link this differential resilience to the persistence of adequate spatial refuges for terrestrial species, enabling populations to be sustained through source-sink dynamics, contrasting with unremitting hunting pressure on more accessible aquatic habitats. Our findings attest the high vulnerability of aquatic fauna to unregulated hunting, particularly during years of severe drought. We propose that the relative resilience of terrestrial species suggests a marked opportunity for managing, rather than criminalizing, contemporary traditional subsistence hunting in Amazonia, through both the engagement of local people in community-based comanagement programs and science-led conservation governance

SIRENIA FOSSILS FROM QOM FORMATION (BURDIGALIAN) OF THE KABUDAR AHANG AREA, NORTHWEST IRAN

Fossil remains of sirenians (Mammalia; Dugongidae) are reported from the late early Miocene (Burdigalian) Qom Formation near the town of Shirin Su, northwest Kabudar Ahang region, west of Tehran, Iran. The fossils consist of partial postcranial skeletons preserved mostly as natural molds in limestone. In the absence of skulls or other diagnostic elements, it is not evident which dugongid subfamily these specimens represent: Halitheriinae or Dugonginae. Both subfamilies were present in contemporaneous Western Tethys (Mediterranean) deposits, but so far only dugongines have been found in Neogene rocks of Eastern Tethys. Since the Iranian deposits are located between these two parts of the former Tethys Seaway, it will be interesting to see which group(s) the Iranian sirenians prove to represent, once their taxonomic identity has been determined through future discoveries

Morphological and systematic re-assessment of the late Oligocene “Halitherium” bellunense reveals a new crown group genus of Sirenia

“Halitherium” bellunense is exclusively known from a single individual from upper Oligocene glauconitic sandstone near Belluno, northern Italy. According to a review of its morphological basis, which consists of associated cranial elements, some vertebrae and ribs, this specimen is identified as a juvenile, because the first upper incisor (I1) and supposedly second upper molar (M2) are not fully erupted. However, its juvenile status allowed only cautious conclusions on its taxonomy and systematic affinity. The presence of a nasal process of the premaxilla with a broadened and bulbous posterior end, and a lens-shaped I1, corroborate an evolutionarily-derived status of this species that places it well within the sirenian crown group Dugonginae. Considering these new data and in order to avoid continued misuse of the inappropriate generic name of Halitherium, a new generic name, Italosiren gen. nov., and emended species diagnosis are supplied for this taxon

Taxa de substituição horizontal de dentes no peixe-boi

Teeth shed from the horizontally-advancing tooth rows of captive Amazonian manatees (Trichechus inunguis) indicate a rate of tooth row movement of about 1 mm/month. The movement appears to be initiated by weaning and continues throughout life, with variations in rate correlated with overall growth rate but independent of rate of tooth wear

Protosiren smithae, New Species (Mammalia, Sirenia), from the Late Middle Eocene of Wadi Hitan, Egypt

69-87http://deepblue.lib.umich.edu/bitstream/2027.42/48642/2/ID509.pd

Seagrass and submerged aquatic vegetation (VAS) habitats off the Coast of Brazil: state of knowledge, conservation and main threats

Seagrass meadows are among the most threatened ecosystems on earth, raising concerns about the equilibrium of coastal ecosystems and the sustainability of local fisheries. The present review evaluated the current status of the research on seagrasses and submerged aquatic vegetation (SAV) habitats off the coast of Brazil in terms of plant responses to environmental conditions, changes in distribution and abundance, and the possible role of climate change and variability. Despite an increase in the number of studies, the communication of the results is still relatively limited and is mainly addressed to a national or regional public; thus, South American seagrasses are rarely included or cited in global reviews and models. The scarcity of large-scale and long-term studies allowing the detection of changes in the structure, abundance and composition of seagrass habitats and associated species still hinders the investigation of such communities with respect to the potential effects of climate change. Seagrass meadows and SAV occur all along the Brazilian coast, with species distribution and abundance being strongly influenced by regional oceanography, coastal water masses, river runoff and coastal geomorphology. Based on these geomorphological, hydrological and ecological features, we characterised the distribution of seagrass habitats and abundances within the major coastal compartments. The current conservation status of Brazilian seagrasses and SAV is critical. The unsustainable exploitation and occupation of coastal areas and the multifold anthropogenic footprints left during the last 100 years led to the loss and degradation of shoreline habitats potentially suitable for seagrass occupation. Knowledge of the prevailing patterns and processes governing seagrass structure and functioning along the Brazilian coast is necessary for the global discussion on climate change. Our review is a first and much-needed step toward a more integrated and inclusive approach to understanding the diversity of coastal plant formations along the Southwestern Atlantic coast as well as a regional alert the projected or predicted effects of global changes on the goods and services provided by regional seagrasses and SAV