602 research outputs found
Bony outgrowths on the jaws of an extinct sperm whale support macroraptorial feeding in several stem physeteroids
No full textSeveral extinct sperm whales (stem Physeteroidea) were recently proposed to differ markedly in their feeding ecology from the suction-feeding modern sperm whales Kogia and Physeter. Based on cranial, mandibular, and dental morphology, these Miocene forms were tentatively identified as macroraptorial feeders, able to consume proportionally large prey using their massive teeth and robust jaws. However, until now, no corroborating evidence for the use of teeth
during predation was available.We report on a new specimen of the stem physeteroid Acrophyseter, from the late middle to early late Miocene of Peru, displaying unusual bony outgrowths along some of the upper alveoli. Considering their position and outer shape, these are identified as buccal maxillary exostoses. More developed along posterior teeth and in tight contact with the high portion of the dental root outside the bony alveoli, the exostoses are hypothesized to have developed during powerful bites; they may have worked as buttresses, strengthening the teeth when facing intense occlusal forces. These buccal exostoses further support a raptorial feeding technique for Acrophyseter and, indirectly, for other extinct sperm whales with a similar oral apparatus (Brygmophyseter, Livyatan, Zygophyseter). With a wide size range, these Miocene stem physeteroids were major marine macropredators, occupying ecological niches nowadays mostly taken by killer whales
A new metriorhynchid crocodylomorph from the Lower Kimmeridge Clay Formation (Late Jurassic) of England, with implications for the evolution of dermatocranium ornamentation in Geosaurini
No full textFigure 14. Torvoneustes coryphaeus sp. nov., holotype MJML K1863. Isolated teeth: one in (A) lingual view and (B) carinal view; and another in (C) lingual view. Scale bars: 1 cm.Published as part of Young, Mark T., Andrade, Marco Brandalise De, Etches, Steve & Beatty, Brian L., 2013, A new metriorhynchid crocodylomorph from the Lower Kimmeridge Clay Formation (Late Jurassic) of England, with implications for the evolution of dermatocranium ornamentation in Geosaurini, pp. 820-848 in Zoological Journal of the Linnean Society 169 (4) on page 841, DOI: 10.1111/zoj.12082, http://zenodo.org/record/489049
First evidence of denticulated dentition in teleosaurid crocodylomorphs
No full textTeleosauridae was a group of largely marine Mesozoic crocodylomorphs, typically considered as akin to “marine gavials” due to their elongate, tubular, polydont rostra that are indicative of a piscivorous diet. Here we show that these extinct crocodylomorphs were more anatomically, and perhaps ecologically, varied than previously thought. We report the first evidence of denticles in a teleosaurid tooth, revealed by scanning electron microscopic (SEM) analysis of a tooth from the holotype of “Steneosaurus” obtusidens. These denticles are cryptic, because they are microscopic, not contiguous along the carinae (instead forming short series), and are detectable only using SEM. This incipient denticle morphology is similar to that recently discovered in a closely related group of marine crocodylomorphs, the Metriorhynchidae. In particular, the denticulation morphology of “Steneosaurus” is similar to that of the geosaurin metriorhynchid Torvoneustes, indicating that these two taxa may have employed similar feeding styles and that “S.”obtusidens may have been a nearshore ecological analogue to the more offshore, fast-swimming geosaurins. Previous authors have considered “S.” obtusidens and Machimosaurus to be durophagous, but the discovery of denticulated teeth indicates that they had a more varied diet and feeding style, and included flesh slicing as part of their feeding toolkit. It is currently unknown how extensive denticulate carinae may be in Teleosauridae, and we hypothesise that cryptic denticles may also be present in other marine crocodylomorphs once they are subjected to SEM study
Physeteroids from the Miocene of Peru: new data on Acrophyseter and Livyatan supports macroraptorial feeding in several extinct sperm whales
No full textWith only three extant species, modern sperm whales (Odontoceti, Physeteroidea) are generally considered as relicts of a previously more diversified clade, originating
during the late Oligocene and reaching its maximum diversity in the Miocene. Displaying a spectacular size disparity, modern Kogia spp. (pygmy and dwarf sperm whales) and Physeter (giant sperm whale) share several morphological features (dental reduction, slender mandibles, and small temporal fossa) correlated to a specialized suction feeding technique on disphotic to mesopelagic prey. Although remaining scarce, the fossil record of sperm whales suggests a broader past ecological diversity; based on cranial and dental characters, several middle to late Miocene taxa (the medium size Acrophyseter, the large Brygmophyseter and
Zygophyseter, and the giant Livyatan) were tentatively interpreted as macroraptorial feeders, using massive teeth deeply embedded in robust upper and lower jaws to catch proportionally large prey. Together with the study of two new Acrophyseter skulls, a detailed description of the type material of A. deinodon and L. melvillei (both originating from Miocene levels of the Pisco Formation, Peru) provides new clues about their hypothetical feeding strategies.
The analysis of the specimens followed different lines: (1) basic craniomandibular anatomy and comparison; (2) reconstruction of the musculature for adduction/abduction of the mandibles; (3) bone pathology including the description of buccal maxillary exostoses in A. deinodon; and (4) tooth wear. Observations and resulting interpretations point to a feeding technique involving intense use of teeth via powerful bites, contrasting markedly with the capture technique in both Kogia and Physeter. Placed in a phylogenetic context, the morphology of the oral apparatus in these macroraptorial sperm whales is thought to represent a combination of plesiomorphic and derived characters. Finally, a detailed sedimentological and paleontological analysis of the fossil-rich localities of Cerro Colorado and Cerro los Quesos yielded a vast amount of data about the faunas associated to Acrophyseter and Livyatan; the mapping of several hundreds of marine vertebrate specimens, as well as their positioning along stratigraphic sections, provides valuable indications about potential prey of these extinct sperm whales
Comparisons and Uncertainty in Fat and Adipose Tissue Estimation Techniques: The Northern Elephant Seal as a Case Study.
No full textFat mass and body condition are important metrics in bioenergetics and physiological studies. They can also link foraging success with demographic rates, making them key components of models that predict population-level outcomes of environmental change. Therefore, it is important to incorporate uncertainty in physiological indicators if results will lead to species management decisions. Maternal fat mass in elephant seals (Mirounga spp) can predict reproductive rate and pup survival, but no one has quantified or identified the sources of uncertainty for the two fat mass estimation techniques (labeled-water and truncated cones). The current cones method can provide estimates of proportion adipose tissue in adult females and proportion fat of juveniles in northern elephant seals (M. angustirostris) comparable to labeled-water methods, but it does not work for all cases or species. We reviewed components and assumptions of the technique via measurements of seven early-molt and seven late-molt adult females. We show that seals are elliptical on land, rather than the assumed circular shape, and skin may account for a high proportion of what is often defined as blubber. Also, blubber extends past the neck-to-pelvis region, and comparisons of new and old ultrasound instrumentation indicate previous measurements of sculp thickness may be biased low. Accounting for such differences, and incorporating new measurements of blubber density and proportion of fat in blubber, we propose a modified cones method that can isolate blubber from non-blubber adipose tissue and separate fat into skin, blubber, and core compartments. Lastly, we found that adipose tissue and fat estimates using tritiated water may be biased high during the early molt. Both the tritiated water and modified cones methods had high, but reducible, uncertainty. The improved cones method for estimating body condition allows for more accurate quantification of the various tissue masses and may also be transferrable to other species
A stratigraphically precise record of Protosiren (Protosirenidae, Sirenia) from North America
No full textDaily dynamics of contrasting spring algal blooms in Santa Monica Bay (central Southern California Bight)
No full text© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ollison, G., Hu, S., Hopper, J., Stewart, B., Smith, J., Beatty, J., Rink, L., & Caron, D. Daily dynamics of contrasting spring algal blooms in Santa Monica Bay (central Southern California Bight). Environmental Microbiology. (2022), https://doi.org/10.1111/1462-2920.16137.Protistan algae (phytoplankton) dominate coastal upwelling ecosystems where they form massive blooms that support the world's most important fisheries and constitute an important sink for atmospheric CO2. Bloom initiation is well understood, but the biotic and abiotic forces that shape short-term dynamics in community composition are still poorly characterized. Here, high-frequency (daily) changes in relative abundance dynamics of the metabolically active protistan community were followed via expressed 18S V4 rRNA genes (RNA) throughout two algal blooms during the spring of 2018 and 2019 in Santa Monica Bay (central Southern California Bight). A diatom bloom formed after wind-driven, nutrient upwelling events in both years, but different taxa dominated each year. Whereas diatoms bloomed following elevated nutrients and declined after depletion each year, a massive dinoflagellate bloom manifested under relatively low inorganic nitrogen conditions following diatom bloom senescence in 2019 but not 2018. Network analysis revealed associations between diatoms and cercozoan putative parasitic taxa and syndinean parasites during 2019 that may have influenced the demise of the diatoms, and the transition to a dinoflagellate-dominated bloom.This work was supported by the National Science Foundation #1136818 (David A. Caron)
Assessing the role of soil chemoautotrophs in carbon cycling: An investigation into isotopically labelled soil microorganisms
No full textRecently observed increases in atmospheric CO2 have created great interest in carbon capture technologies and natural sinks of this major component of the carbon cycle. Humic substances are a large, operationally defined fraction of soil organic matter. It was thought that humic substances consist of cross-linked macromolecular structures forming a distinct class of compounds. However, it was recently concluded by members of my research group that the vast majority of humic material in soils, are a complex mixture of microbial/plant biopolymers and degradation products, and not a distinct chemical category. The postulation that microbial inputs to soil carbon are greatly underestimated was put forward by my research group in 2007. Therefore, I have attempted to demonstrate the inputs made by soil chemoautotrophic bacteria. A method was developed where soil samples were measured for chemoautotrophic activity by subjecting them to a suite of scientific techniques. A growth chamber was used to propagate extant soil chemoautotrophic bacteria from different soils and subjected to an array of chemical and biological analyses. The growth chamber was used to measure CO2 concentrations and introduce stable isotopic 13CO2. Estimations of CO2 sequestration were made using direct measurements for Irish soils and one Eurasian soil. Isotope labelled DNA was isolated using cesium chloride gradient ultracentrifugation. The dominant chemoautotrophic bacteria uncovered were Thiobacillus denitrificans and Thiobacillus thioparus. Labelled biomass was isolated and described using GCMS-IRMS and NMR, where an array of PLFAs, protein/peptide, carbohydrates and aliphatics were observed. Finally, an attempt to mimic common agricultural practice was performed to measure soil chemoautotrophic activity. This demonstrated the capability of this approach to benefit carbon flux estimations and hopefully in the future help to elucidate carbon flow into soils for the greater environment
Attenuated evolution of mammals through the Cenozoic.
No full textThe Cenozoic diversification of placental mammals is the archetypal adaptive radiation. Yet, discrepancies between molecular divergence estimates and the fossil record fuel ongoing debate around the timing, tempo, and drivers of this radiation. Analysis of a three-dimensional skull dataset for living and extinct placental mammals demonstrates that evolutionary rates peak early and attenuate quickly. This long-term decline in tempo is punctuated by bursts of innovation that decreased in amplitude over the past 66 million years. Social, precocial, aquatic, and herbivorous species evolve fastest, especially whales, elephants, sirenians, and extinct ungulates. Slow rates in rodents and bats indicate dissociation of taxonomic and morphological diversification. Frustratingly, highly similar ancestral shape estimates for placental mammal superorders suggest that their earliest representatives may continue to elude unequivocal identification
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