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Vélez-Juarbe, Jorge; Domning, Daryl Paul; Pyenson, Nicholas D.
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2012 |
Iterative evolution of sympatric seacow (Dugongidae, Sirenia) assemblages during the past ~26 million years.
PLoS ONE 7(2): e31294. 8 pp. 1 tab. 3 figs. + 1 fig. in Supporting Information. DOI:10.1371/journal.pone.0031294. Feb. 3, 2012.
–Available online at: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0031294.
ABSTRACT: 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.
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Pyenson, Nicholas D.; Kelley, Neil P.; Parham, James F.
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2014 |
Marine tetrapod macroevolution: Physical and biological drivers on 250 Ma of invasions and evolution in ocean ecosystems.
Palaeogeography, Palaeoclimatology, Palaeoecology 400: 1-8. 1 fig. + online supplementary material. https://doi.org/10.1016/j.palaeo.2014.02.018 Apr. 15, 2014.
–ABSTRACT: The dominant consumers in today's ocean ecosystems are marine mammals, including cetaceans, sirenians, and pinnipeds,and other marine carnivorans.The ecological dominance of marine mammals can be traced back to at least seven independent transitions during the Cenozoic, when different lineages of terrestrial mammals underwent land to sea evolutionary transformations. However, the evolution of marine mammals represents only the most recent set of marine invasions by tetrapods over the past 250 Ma. During the Mesozoic, over a dozen different reptile lineages (e.g., mosasaurs, ichthyosaurs, turtles, snakes) evolved obligate marine lineages, including a few lineages that persist to today,such as seaturtles. Birds,which are phylogenetically nested among diapsid reptiles, have also repeatedly adapted to marine life since the Cretaceous. Attempts to understand the common patterns of marine tetrapod evolution, and the processes that have shaped them, have largely been limited to individual groups. Placed in a broad comparative view from the Mesozoic to the Cenozoic eras, the macroevolution of marine tetrapods reveals evolutionary drivers at different scales, along with morphological parallels, unique evolutionary innovations, and the strong influence of historical constraints. Major physical, environmental drivers appear to be responsible for some patterns in marine tetrapod evolution at some temporal and geographic scales, but these drivers are not unique causes, as biological drivers (e.g., escalation) likely also play a role. The culmination of this trophic ascendancy has been dramatically altered by human hunting (especially of marine mammals), underscoring the need for historical datasets that extend into deep time to understand the ecological history of marine tetrapods.
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Pyenson, Nicholas D.; Parham, James F.; Vélez-Juarbe, Jorge
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2016 |
The dilemma of trade samples and the importance of museum vouchers – caveats from a study on the extinction of Steller's sea cow: a comment on Crerar et al. (2014).
Biology Letters (Royal Society) 12: 20150149; 2 pp. http://dx.doi.org/10.1098/rsbl.2015.0149 Feb. 3, 2016.
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Pyenson, Nicholas D.; Vermeij, Geerat J.
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2016 |
The rise of ocean giants: maximum body size in Cenozoic marine mammals as an indicator for productivity in the Pacific and Atlantic Oceans.
Biol. Lett. 12(7): 4 pp. 1 tab. 1 fig. + online supplemental material. https://doi.org/10.1098/rsbl.2016.0186 July 31, 2016; publ. online July 1, 2016.
–ABSTRACT: Large consumers have ecological influence disproportionate to their abundance, although this influence in food webs depends directly on productivity. Evolutionary patterns at geologic timescales inform expectations about the relationship between consumers and productivity, but it is very difficult to track productivity through time with direct, quantitative measures. Based on previous work that used the maximum body size of Cenozoic marine invertebrate assemblages as a proxy for benthic productivity, we investigated how the maximum body size of Cenozoic marine mammals, in two feeding guilds, evolved over comparable temporal and geographical scales. First, maximal size in marine herbivores remains mostly stable and occupied by two different groups (desmostylians and sirenians) over separate timeframes in the North Pacific Ocean, while sirenians exclusively dominated this ecological mode in the North Atlantic. Second, mysticete whales, which are the largest Cenozoic consumers in the filter-feeding guild, remained in the same size range until a Mio-Pliocene onset of cetacean gigantism. Both vertebrate guilds achieved very large size only recently, suggesting that different trophic mechanisms promoting gigantism in the oceans have operated in the Cenozoic than in previous eras.
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Pyenson, Nicholas D.; Al-Ansi, Mehsin; Fieseler, Clare M; Al Jaber, Khalid Hassan; Klim, Katherine D.; LeBlanc, Jacques; Mohamed, Ahmad Mujthaba Dheen; Al-Shaikh, Ismail; Marshall, Christopher D.
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2022 |
Fossil Sirenia from the Pleistocene of Qatar: new questions about the antiquity of sea cows in the Gulf Region.
PeerJ https://peerj.com/articles/14075 Oct. 18, 2022.
–ABSTRACT: One of the largest and least documented populations of dugongs (Dugong dugon) resides in the coastal waters of the United Arab Emirates, and waters surrounding Saudi Arabia, Bahrain, and Qatar. The archaeological record of dugongs in the Gulf Region is abundant, but little is known about their fossil record in the region. Here we report an isolated sirenian rib fragment from the Futaisi Member of the Fuwayrit Formation near the town of Al Ruwais, in northern Qatar. The Fuwayrit Formation is a marine Pleistocene deposit exposed onshore in Qatar and the United Arab Emirates. Based on the correlative dating of the basal Futaisi Member with other onshore platforms, the rib fragment is approximately 125 ka. We propose that this isolated rib (likely the first rib from the right side) belongs to Dugongidae, with strong similarities to extant Dugong. We cannot, however, eliminate the possibility that it belongs to an extinct taxon, especially given its similarities with other fossil dugongid material from both Qatar and elsewhere in the world. Aside from reflecting the presence of Gulf seagrass communities in the Pleistocene, this occurrence also suggests that different (and potentially multiple) lineages of sirenians inhabited the Gulf Region in the geologic past.
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Matsui, Kumiko; Pyenson, Nicholas D.
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2023 |
New evidence for the antiquity of Desmostylus from the Skooner Gulch Formation of California.
_Royal Society Open Science_ 10: 221648. 1 tab. 4 figs. https://doi.org/10.1098/rsos.221648 + electronic suppl. material at https://doi.org//10.6084/m9.figshare.c.6673576.
–ABSTRACT: Desmostylus is an extinct marine mammal genus that belongs to Desmostylia, a clade of extinct herbivorous mammals. While desmostylian remains are widely reported from Paleogene and Neogene marine strata of the North Pacific Rim, occurrences of the genus Desmostylus are almost entirely limited to middle Miocene strata, with only a few early Miocene records from Japan. Here we report a Desmostylus tooth from the earliest Miocene (Aquitanian) Skooner Gulch Formation in northern California, USA. This specimen exhibits cuspules around the crown, a primitive trait of the subfamily Desmostylidae, as seen in more basal branching desmostylid taxa such as Cornwallius and Ounalashkastylus, but with a high tooth crown and thickened enamel. The specimen is also diagnostically different from all other desmostylid genera, such as Cornwallius, and Ounalashklastylus. The Aquitanian age of the Skooner Gulch Formation implies that the distinctive tooth morphology of Desmostylus has persisted, largelyunchanged, for more than 15 million years and that desmostylids possibly originated in western North America.
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Bibliography and Index of the Sirenia and Desmostylia 