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Robert W. Boessenecker - One of the best experts on this subject based on the ideXlab platform.
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herpetocetus morrowi cetacea mysticeti a new species of diminutive baleen whale from the upper pliocene piacenzian of california usa with observations on the evolution and relationships of the cetotheriidae
Zoological Journal of the Linnean Society, 2014Co-Authors: Robert W. Boessenecker, Joseph El J Adli, Thomas A DemereAbstract:The extinct edentulous mysticete family Cetotheriidae historically has been viewed as a notoriously paraphyletic group, and only recently have rigorous studies been executed to rectify this issue. These problems do not necessarily just stem from lack of phylogenetic analyses, but are in part because of a general lack of complete specimens, poor descriptions of taxa, and long-lived taxonomic instability issues. The fossil mysticete genus Herpetocetus is a poster child of these problems as it is primarily only known from a few relatively incomplete and poorly described specimens. A new species of Herpetocetus from the upper Pliocene of California, Herpetocetus morrowi sp. nov., provides an archetypal model for the genus based on a multitude of well-preserved specimens. These specimens reveal a diminutive mysticete characterized by an elongate rostrum and roughly quadrate cranium. A mosaic of primitive and derived features preserved in this new species underscores its potential value in helping to resolve a number of taxonomic and phylogenetic problems. The occurrence of specimens assignable to juvenile through to mature adult individuals provides a basis for investigating ontogenetic changes. Functional analysis of the unusual craniomandibular anatomy of H. morrowi suggests a limited degree of mandibular gape and an enhanced capacity for longitudinal rotation of the dentary, features that support a hypothesis of suction feeding convergent with that of living grey whales. A phylogenetic analysis provides support for recognition of a redefined and monophyletic Cetotheriidae and Herpetocetinae, and also serves as a basis for evaluating the recent proposal that the pygmy right whale (Caperea marginata) is a living cetothere. Morphological features of Herpetocetus morrowi, including features of the cranium and petrosal, suggest that a number of the purported synapomorphies supporting a Caperea−cetothere grouping are either symplesiomorphies, nonhomologous features, or are highly variable. © 2014 The Linnean Society of London
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Pleistocene survival of an archaic dwarf baleen whale (Mysticeti: Cetotheriidae)
Naturwissenschaften, 2013Co-Authors: Robert W. BoesseneckerAbstract:Pliocene baleen whale assemblages are characterized by a mix of early records of extant mysticetes, extinct genera within modern families, and late surviving members of the extinct family Cetotheriidae. Although Pleistocene baleen whales are poorly known, thus far they include only fossils of extant genera, indicating Late Pliocene extinctions of numerous mysticetes alongside other marine mammals. Here a new fossil of the Late Neogene cetotheriid mysticete Herpetocetus is reported from the Lower to Middle Pleistocene Falor Formation of Northern California. This find demonstrates that at least one archaic mysticete survived well into the Quaternary Period, indicating a recent loss of a unique niche and a more complex pattern of Plio–Pleistocene faunal overturn for marine mammals than has been previously acknowledged. This discovery also lends indirect support to the hypothesis that the pygmy right whale ( Caperea marginata ) is an extant cetotheriid, as it documents another cetotheriid nearly surviving to modern times.
Felix G Marx - One of the best experts on this subject based on the ideXlab platform.
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A Miocene pygmy right whale fossil from Australia
'PeerJ', 2018Co-Authors: Felix G Marx, Erich M G Fitzgerald, Travis Park, Alistair R. EvansAbstract:Neobalaenines are an enigmatic group of baleen whales represented today by a single living species: the pygmy right whale, Caperea marginata, found only in the Southern Hemisphere. Molecular divergence estimates date the origin of pygmy right whales to 22–26 Ma, yet so far there are only three confirmed fossil occurrences. Here, we describe an isolated periotic from the latest Miocene of Victoria (Australia). The new fossil shows all the hallmarks of Caperea, making it the second-oldest described neobalaenine, and the oldest record of the genus. Overall, the new specimen resembles C. marginata in its external morphology and details of the cochlea, but is more archaic in it having a hypertrophied suprameatal area and a greater number of cochlear turns. The presence of Caperea in Australian waters during the Late Miocene matches the distribution of the living species, and supports a southern origin for pygmy right whales
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northern pygmy right whales highlight quaternary marine mammal interchange
Current Biology, 2017Co-Authors: Cheng-hsiu Tsai, Rita Catanzariti, Alberto Collareta, Erich M G Fitzgerald, Felix G Marx, Naoki Kohno, Gianni Insacco, Agatino Reitano, Masayuki OishiAbstract:Summary The pygmy right whale, Caperea marginata , is the most enigmatic living whale. Little is known about its ecology and behaviour, but unusual specialisations of visual pigments [1], mitochondrial tRNAs [2], and postcranial anatomy [3] suggest a lifestyle different from that of other extant whales. Geographically, Caperea represents the only major baleen whale lineage entirely restricted to the Southern Ocean. Caperea -like fossils, the oldest of which date to the Late Miocene, are exceedingly rare and likewise limited to the Southern Hemisphere [4], despite a more substantial history of fossil sampling north of the equator. Two new Pleistocene fossils now provide unexpected evidence of a brief and relatively recent period in geological history when Caperea occurred in the Northern Hemisphere (Figure 1A,B).
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Auditory region of extant mysticetes.
2016Co-Authors: Felix G Marx, Ewan R. FordyceAbstract:(a) Eubalaena australis, NMNZ MM002239; (b) Caperea marginata, OM VT227; (c) Eschrichtius robustus, USNM 364973 (mirrored to facilitate comparisons); (d) Megaptera novaeangliae, USNM269982. Note the enlarged paroccipital concavity in E. robustus.
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Comparison of the tympanic bulla of Caperea, balaenids and Herpetocetus in medial view.
2016Co-Authors: Felix G Marx, Ewan R. FordyceAbstract:(a) Caperea marginata, OM VT227; (b) Eubalaena australis, NMNZ MM000226; (c) Balaenula astensis, MSNTUP I12555; (d) Balaena mysticetus, USNM 15695; (e) Balaenella brachyrhynus, NMB 42001; (f) Herpetocetus transatlanticus, USNM 182962. E. australis and B. astensis have been mirrored to facilitate comparisons.
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Position and shape of the pterygoid hamulus of Caperea marginata.
2016Co-Authors: Felix G Marx, Ewan R. FordyceAbstract:(a) Basicranium of NMNZ MM002235 in posteroventral view; (b) pterygoid hamulus of the same specimen, in ventral view.
Joy S. Reidenberg - One of the best experts on this subject based on the ideXlab platform.
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Anatomy of nasal complex in the southern right whale, Eubalaena australis (Cetacea, Mysticeti)
Journal of anatomy, 2014Co-Authors: Mónica Romina Buono, Marta S. Fernández, Ewan Fordyce, Joy S. ReidenbergAbstract:The nasal region of the skull has undergone dramatic changes during the course of cetacean evolution. In particular, mysticetes (baleen whales) conserve the nasal mammalian pattern associated with the secondary function of olfaction, and lack the sound-producing specializations present in odontocetes (toothed whales, dolphins and porpoises). To improve our understanding of the morphology of the nasal region of mysticetes, we investigate the nasal anatomy, osteology and myology of the southern right whale, Eubalaena australis, and make comparisons with other mysticetes. In E. australis external deflection surfaces around the blowholes appear to divert water off the head, and differ in appearance from those observed in balaenopterids, eschrichtiids and cetotherids. In E. australis the blowholes are placed above hypertrophied nasal soft tissues formed by fat and nasal muscles, a pattern also observed in balaenopterids (rorqual mysticetes) and a cetotherid (pygmy right whale, Caperea marginata). Blowhole movements are due to the action of five nasofacial muscles: dilator naris superficialis, dilator naris profundus, depressor alae nasi, constrictor naris, and retractor alae nasi. The dilator naris profundus found in E. australis has not been previously reported in balaenopterids. The other nasofacial muscles have a similar arrangement in balaenopterids, with minor differences. A novel structure, not reported previously in any mysticete, is the presence of a vascular tissue (rete mirabile) covering the lower nasal passage. This vascular tissue could play a role in warming inspired air, or may engorge to accommodate loss of respiratory space volume due to gas compression from increased pressure during diving.
Cheng-hsiu Tsai - One of the best experts on this subject based on the ideXlab platform.
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Crossing the equator: a northern occurrence of the pygmy right whale
Zoological Letters, 2018Co-Authors: Cheng-hsiu Tsai, James G. MeadAbstract:Here we document the first stranding record of the pygmy right whale in the Northern Hemisphere—on the coast of The Gambia, Africa (NE Atlantic Ocean, around latitude 13° N)—a location in stark contrast to its current distribution exclusively south of the equator. The original specimen is now missing and untraceable, but a photo found in the files of the Marine Mammal Program, Smithsonian Institution shows sufficient diagnostic features that allow it to be taxonomically identified as the pygmy right whale, Caperea marginata , including: small body size; streamlined overall body shape; generally dark skin coloration; arched rostrum along the lateral margin; triangular and narrow rostrum in dorsal view; lack of head callosities; some fringes on the dorsal surface of the tongue; small and relatively posteriorly positioned dorsal fin; and small and dark-colored flipper. On the whole, a stranding of the pygmy right whale in the Northern Hemisphere, although likely to be a chance event, calls for more detailed studies of how climate change and ocean currents affect the evolution and distribution (re-patterning) of marine mammals and, ultimately, the entire marine ecosystem.
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northern pygmy right whales highlight quaternary marine mammal interchange
Current Biology, 2017Co-Authors: Cheng-hsiu Tsai, Rita Catanzariti, Alberto Collareta, Erich M G Fitzgerald, Felix G Marx, Naoki Kohno, Gianni Insacco, Agatino Reitano, Masayuki OishiAbstract:Summary The pygmy right whale, Caperea marginata , is the most enigmatic living whale. Little is known about its ecology and behaviour, but unusual specialisations of visual pigments [1], mitochondrial tRNAs [2], and postcranial anatomy [3] suggest a lifestyle different from that of other extant whales. Geographically, Caperea represents the only major baleen whale lineage entirely restricted to the Southern Ocean. Caperea -like fossils, the oldest of which date to the Late Miocene, are exceedingly rare and likewise limited to the Southern Hemisphere [4], despite a more substantial history of fossil sampling north of the equator. Two new Pleistocene fossils now provide unexpected evidence of a brief and relatively recent period in geological history when Caperea occurred in the Northern Hemisphere (Figure 1A,B).
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Disparate Heterochronic Processes in Baleen Whale Evolution
Evolutionary Biology, 2014Co-Authors: Cheng-hsiu Tsai, R. Ewan FordyceAbstract:Skulls of living baleen whales show distinctive patterns of heterochronic ontogenetic change with implications for mysticete evolution. Here, three baleen whale species are analysed and considered in a heterochronic context. Landmarks show that, during ontogeny, skull morphology changes significantly in the rorqual Balaenoptera borealis and humpback Megaptera novaeangliae (both Balaenopteridae), while the pygmy right whale Caperea marginata (Cetotheriidae: Neobalaeninae) retains an overall juvenile morphology from foetus to adult. Geometric morphometric analyses show that foetal and adult C . marginata are similar, whereas the balaenopterids are more disparate: foetal M . novaeangliae and B . borealis appear in one group, and adult M . novaeangliae and B . borealis are grouped closely. Heterochrony involves paedomorphosis for Caperea , and peramorphosis for the balaenopterids. Heterochrony might cause limited or released developmental constraints, leading to low taxonomic diversity in the single surviving species of neobalaenine, and higher diversity amongst balaenopterids.
Mónica Romina Buono - One of the best experts on this subject based on the ideXlab platform.
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Anatomy of nasal complex in the southern right whale, Eubalaena australis (Cetacea, Mysticeti)
Journal of anatomy, 2014Co-Authors: Mónica Romina Buono, Marta S. Fernández, Ewan Fordyce, Joy S. ReidenbergAbstract:The nasal region of the skull has undergone dramatic changes during the course of cetacean evolution. In particular, mysticetes (baleen whales) conserve the nasal mammalian pattern associated with the secondary function of olfaction, and lack the sound-producing specializations present in odontocetes (toothed whales, dolphins and porpoises). To improve our understanding of the morphology of the nasal region of mysticetes, we investigate the nasal anatomy, osteology and myology of the southern right whale, Eubalaena australis, and make comparisons with other mysticetes. In E. australis external deflection surfaces around the blowholes appear to divert water off the head, and differ in appearance from those observed in balaenopterids, eschrichtiids and cetotherids. In E. australis the blowholes are placed above hypertrophied nasal soft tissues formed by fat and nasal muscles, a pattern also observed in balaenopterids (rorqual mysticetes) and a cetotherid (pygmy right whale, Caperea marginata). Blowhole movements are due to the action of five nasofacial muscles: dilator naris superficialis, dilator naris profundus, depressor alae nasi, constrictor naris, and retractor alae nasi. The dilator naris profundus found in E. australis has not been previously reported in balaenopterids. The other nasofacial muscles have a similar arrangement in balaenopterids, with minor differences. A novel structure, not reported previously in any mysticete, is the presence of a vascular tissue (rete mirabile) covering the lower nasal passage. This vascular tissue could play a role in warming inspired air, or may engorge to accommodate loss of respiratory space volume due to gas compression from increased pressure during diving.
