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Racicot R.A.,Yale University | Demere T.A.,San Diego Natural History Museum | Boessenecker R.W.,University of Otago | Boessenecker R.W.,University of California at Berkeley
Current Biology | Year: 2014

Modern porpoises (Odontoceti: Phocoenidae) are some of the smallest cetaceans and usually feed near the seafloor on small fish and cephalopods [1-3]. Within both extinct and extant phocoenids, no evidence for specialized mandibular morphology has been documented [4-7]. Here we describe a new species of extinct porpoise, Semirostrum ceruttii, from the marine Pliocene San Diego (4.2-1.6 mega-annum, Ma) and Purisima (5-2.5 Ma) formations of California. The mandibles comprise a long, fused, and nearly edentulous prognathous symphysis, extending farther beyond the rostrum than in any known mammal. Phylogenetic analyses based on morphology reconstruct Semirostrum ceruttii as sister to extant (crown) porpoise species with moderate support. We describe the spectacularly preserved holotype specimen based on computed tomography (CT) scans, which allowed visualization of the elongate mental and accessory canals within the symphysis. The elongate canals are similar to those found in Rynchops birds [8] and were likely involved in sensory function. Oblique labial wear facets present on numerous small conical mandibular teeth posterior to the symphysis suggest regular contact with benthic substrate. The unique mandibular and dental characteristics, along with robust scapulae, sternum, and unfused cervical vertebrae, support the interpretation that this species employed a form of benthic skim feeding by using its mandible to probe for and obtain prey. © 2014 Elsevier Ltd.

Lopez-Medellin X.,National Autonomous University of Mexico | Ezcurra E.,University of California at Riverside | Gonzalez-Abraham C.,San Diego Natural History Museum | Hak J.,NatureServe | And 2 more authors.
Journal of Vegetation Science | Year: 2011

Question: Although mangrove forests are generally regarded as highly threatened, some studies have shown that mangrove canopies in the Pacific coast of Mexico have been increasing in recent decades. We investigated the possible causes driving this reported mangrove expansion. Location: The mangrove lagoons of Magdalena Bay in Baja California, Mexico. Methods: We used 50-year-old aerial photographs and 24-year-old satellite images to compare long-term vegetation change, surveyed a coastal vegetation transect to analyse flooding levels, compiled six decades of tidal and oceanographic information, as well as hurricane data to analyse changes in storm frequency or sea-level conditions, and used isotopic analysis to date the age of trees along the gradient. Results: A significant increase in mangrove cover has occurred in backwaters of the lagoons during the last 40 years, and especially during the El Niño anomalies of the 1980s and 1990s, while at the same time the mangrove fringe has been receding. Conclusions: The observed change can be attributed to the combined action of the warm surface waters of El Niño events and sea-level rise. Jointly, these two effects are sufficient to flood large areas of previously non-flooded salt flats, dispersing mangrove seedlings inland. The inland expansion of mangroves, however, does not ease conservation concerns, as it is the seaward fringes, and not the inland margins, that provide the most valuable environmental services for fisheries and coastal protection. © 2011 International Association for Vegetation Science.

The genus Aseptis McDunnough (Lepidoptera, Noctuidae, Noctuinae, Xylenini, Xylenina) is revised to include 15 species based on morphological and molecular data. Several new synonymies are introduced. In addition, two genera are described because of significant morphological differences from Aseptis: Paraseptis gen. n., and Viridiseptis gen. n., resulting in the new combinations Paraseptis adnixa (Grote), comb. n., and Viridiseptis marina (Grote), comb. n. Although this work is primarily based on morphological data, DNA sequence data for the 658-base pair "barcode" segment of the mitochondrial gene for subunit 1 of cytochrome c oxidase was used as a secondary support for taxonomic changes within Aseptis and for the two new genera. Our work should provide clarity and stability in a previously difficult genus. © Tomas Mustelin, Lars G. Crabo.

Ekdale E.G.,San Diego State University | Demere T.A.,San Diego Natural History Museum | Berta A.,San Diego State University
Anatomical Record | Year: 2015

The origin of baleen in mysticetes heralded a major transition during cetacean evolution. Extant mysticetes are edentulous in adulthood, but rudimentary teeth develop in utero within open maxillary and mandibular alveolar grooves. The teeth are resorbed prenatally and the alveolar grooves close as baleen germ develops. Arteries supplying blood to highly vascularized epithelial tissue from which baleen develops pass through lateral nutrient foramina in the area of the embryonic alveolar grooves and rudimentary teeth. Those vessels are hypothesized to be branches of the superior alveolar artery, but branches of the greater palatine arteries may play a role in the baleen vascularization. Through a combination of latex injection, CT, and traditional dissection of the palate of a neonatal gray whale (Eschrichtius robustus), we confirm that the baleen receives blood from vessels within the superior alveolar canal via the lateral foramina. The greater palatine artery is restricted to its own passage with no connections to the baleen. This study has implications for the presence of baleen in extinct taxa by identifying the vessels and bony canals that supply blood to the epithelium from which baleen develops. The results indicate that the lateral foramina in edentulous mysticete fossils are bony correlates for the presence of baleen, and the results can be used to help identify bony canals and foramina that have been used to reconstruct baleen in extinct mysticetes that retained teeth in adulthood. Further comparisons are made with mammals that also possess oral keratin structures, including ruminants, ornithorhynchid monotremes, and sirenians. Anat Rec, 298:691-702, 2015. © 2015 Wiley Periodicals, Inc.

Berta A.,San Diego State University | Ekdale E.G.,San Diego State University | Demere T.A.,San Diego Natural History Museum | Reidenberg J.S.,Mount Sinai School of Medicine
Anatomical Record | Year: 2015

The gray whale (Eschrichtius robustus) is the sole living representative of the mysticete (baleen whale) family Eschrichtiidae. Previous anatomical work on gray whales has been limited owing, in part, to difficulties of specimen access. These contributions to the anatomy of the gray whale head based on dissection of a stranded specimen from northern California include detailed investigation of internal and external features that confirm existing information and provide new evidence for their functional roles, particularly in thermoregulation and feeding. Anat Rec, 298:643-647, 2015. © 2014 Wiley Periodicals, Inc.

Devitt T.J.,University of California at Berkeley | Devitt T.J.,University of Florida | Devitt S.E.C.,Ziegler | Hollingsworth B.D.,San Diego Natural History Museum | And 2 more authors.
Molecular Ecology | Year: 2013

Understanding the biotic consequences of Pleistocene range shifts and fragmentation remains a fundamental goal in historical biogeography and evolutionary biology. Here, we combine species distribution models (SDM) from the present and two late Quaternary time periods with multilocus genetic data (mitochondrial DNA and microsatellites) to evaluate the effect of climate-induced habitat shifts on population genetic structure in the Large-blotched Ensatina (Ensatina eschscholtzii klauberi), a plethodontid salamander endemic to middle and high-elevation conifer forest in the Transverse and Peninsular Ranges of southern California and northern Baja California. A composite SDM representing the range through time predicts two disjunct refugia, one in southern California encompassing the core of the species range and the other in the Sierra San Pedro Mártir of northern Baja California at the southern limit of the species range. Based on our spatial model, we would expect a pattern of high connectivity among populations within the northern refugium and, conversely, a pattern of isolation due to long-term persistence of the Sierra San Pedro Mártir population. Our genetic results are consistent with these predictions based on the hypothetical refugia in that (i) historical measures of population connectivity among stable areas are correlated with gene flow estimates; and (ii) there is strong geographical structure between separate refugia. These results provide evidence for the role of recent climatic change in shaping patterns of population persistence and connectivity within the Transverse and Peninsular Ranges, an evolutionary hotspot. © 2013 Blackwell Publishing Ltd.

Churchill M.,University of Wyoming | Berta A.,San Diego State University | Demere T.,San Diego Natural History Museum
Marine Mammal Science | Year: 2012

Balaenidae (right whales) are large, critically endangered baleen whales represented by four living species. The evolutionary relationships of balaenids are poorly known, with the number of genera, relationships to fossil taxa, and position within Mysticeti in contention. This study employs a comprehensive set of morphological characters to address aspects of balaenid phylogeny. A sister-group relationship between neobalaenids and balaenids is strongly supported, although this conflicts with molecular evidence, which may be an artifact of long-branch attraction (LBA). Monophyly of Balaenidae is supported, and three major clades are recognized: (1) extinct genus Balaenula, (2) extant and extinct species of the genus Eubalaena, and (3) extant and extinct species of the genus Balaena plus the extinct taxon, Balaenella. The relationships of these clades to one another, as well as to the early Miocene stem balaenid, Morenocetus parvus, remain unresolved. Pliocene taxa, Balaenula astensis and Balaenula balaenopsis, form a clade that is the sister group to the Japanese Pliocene Balaenula sp. Eubalaena glacialis and Pliocene Eubalaena belgica, are in an unresolved polytomy with a clade including E. japonica and E. australis. Extant and fossil species of Balaena form a monophyletic group that is sister group to the Dutch Pliocene Balaenella, although phylogenetic relationships within Balaena remain unresolved. © 2011 by the Society for Marine Mammalogy.

Bisconti M.,San Diego Natural History Museum | Bosselaers M.,Royal Belgian Institute Of Natural Sciences
Zoological Journal of the Linnean Society | Year: 2016

A new extinct genus, Fragilicetus gen. nov., is described here based on a partial skull of a baleen-bearing whale from the Early Pliocene of the North Sea. Its type species is Fragilicetus velponi sp. nov. This new whale shows a mix of morphological characters that is intermediate between those of Eschrichtiidae and those of Balaenopteridae. A phylogenetic analysis supported this view and provided insights into some of the morphological transformations that occurred in the process leading to the origin of Balaenopteridae. Balaenopterid whales show specialized feeding behaviour that allows them to catch enormous amounts of prey. This behaviour is possible because of the presence of specialized anatomical features in the supraorbital process of the frontal, temporal fossa, glenoid fossa of the squamosal, and dentary. Fragilicetus velponi gen. et sp. nov. shares the shape of the supraorbital process of the frontal and significant details of the temporal fossa with Balaenopteridae but maintains an eschrichtiid- and cetotheriid-like squamosal bulge and posteriorly protruded exoccipital. The character combination exhibited by this cetacean provides important information about the assembly of the specialized morphological features responsible for the highly efficient prey capture mechanics of Balaenopteridae. © 2016 The Linnean Society of London.

Herentalia nigra gen. et sp. nov. is described and compared to other mysticetes. It belongs to Cetotheriidae s.s. and represents one of the best-preserved cetotheriid skulls from the southern border of the North Sea. A comprehensive phylogenetic analysis revealed that it is closely related to Nannocetus and to a Japanese Herpetocetus, suggesting that it belongs to the subfamily Herpetocetinae. The phylogenetic analysis performed tests the recent hypothesis that Caperea marginata belongs to Cetotheriidae. However the present results confirm that the pygmy right whale cannot be considered a member of Cetotheriidae. The phylogenetic analysis was used as the basis for a cladistic palaeobiogeographical analysis of Cetotheriidae that revealed that the family originated in the Pacific basin during the Burdigalian and subsequently underwent a sequence of dispersal and vicariance events that allowed its members to enter other ocean basins. The evolution of Cetotheriidae diversity was punctuated by two distinct phases of species originations (one in the Burdigalian and the other in the Tortonian) that broadly correspond to a massive increase of food availability in the ocean trophic webs. © 2014 © 2014 The Trustees of the Natural History Museum, London 2014. All Rights Reserved.

Keil P.,Yale University | Keil P.,Academy of Sciences of the Czech Republic | Belmaker J.,Yale University | Belmaker J.,Tel Aviv University | And 3 more authors.
Methods in Ecology and Evolution | Year: 2013

Reliable methods to downscale species distributions from coarse to fine grain (equivalent to resolution or support) hold great potential benefit for ecology and conservation. Existing methods have been based on partially unrealistic assumptions and yield mixed results. Here, we introduce a novel and simple approach for downscaling species distribution models based on a hierarchical Bayesian modelling (HBM) framework. Our approach treats putative (unknown) fine-grain presences/absences as latent variables, which are modelled as a function of observed fine-grain environmental variables and constrained by observed coarse-grain presences/absences using logistic regression. The aim is to produce downscaled fine-grain probabilities of species occurrence that (1) closely resemble the probabilities produced by a logistic model parameterized with the observed fine-grain data (the 'reference model') and (2) are improvements over conventional downscaling methods. We additionally test how fine-grain occupancy based on power-law scale-area relationships modifies the downscaling results. We test our approach on 127 bird species from the San Diego breeding atlas data surveyed at 5 km grain. The HBM approach provides unbiased fine-grain probabilities of occurrence whilst the conventional methods (direct approach, point sampling) consistently over-predict occurrence probabilities. Incorporation of the downscaled occupancy further improves reliability of the models, but only in cases when the fine-grain occupancy is estimated accurately. Summing predictions across grid cells and species, HBMs provide better estimates of fine-grain species richness than conventional methods. They also provide better estimates of fine-grain occupancy (prevalence). The presented HBM-based downscaling approach offers improved predictions of fine-grain presence and absence compared with existing methods. The combination of the Bayesian approach with key macroecological relationships (specifically, the scale-area relationship) offers a promising general basis for downscaling distributions that may be extended, for example, using generalized linear or additive models. These approaches enable integrative predictions of spatial biodiversity patterns at fine grains. © 2012 The Authors. Methods in Ecology and Evolution. © 2012 British Ecological Society.

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