FIGURE 12
Hypothesized ecological replacement of desmostylians (circles) by sirenians (squares) in the North Pacific Ocean. On the top, map of the localities of Tortonian age (11 Ma) where desmostylian and sirenian were recorded. On the bottom, map of the localities of Zanclean age (5 Ma) where sirenians were recorded. Desmostylia disappear from the fossil record by the end of the Tortonian (7.2 Ma) when sirenians, particularly Hydrodamalis spp., start colonizing this region, likely feeding on the same resources. Only one occurrence per genus is reported in each locality. Locality data for each occurrence of Desmostylia and Sirenia in the Tortonian and Zanclean were downloaded from PBDB (https://paleobiodb.org) using the search parameters described in Materials and Methods and then plotted on the map.
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Marine mammals are key components of aquatic ecosystems. Feeding strategies identified in extant cetaceans, pinnipeds, sirenians, marine otters, and polar bears are associated with anatomical specializations of the head (rostrum, palate, temporomandibular joint, teeth/baleen, mandible). Genetic and ontogenetic evidence of skull and tooth morphology...
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Context 1
... are a completely extinct, enigmatic group of herbivorous aquatic mammals, exclusively distributed in the North Pacific, likely related to either Afrotheria, Perissodactyla, or Paenungulatomorpha ( Matsui and Tsuihiji, 2019). Evidence for their replacement by sirenians is provided by the decrease in diversity of desmostylians after the Tortonian followed by their disappearance in the Messinian, which coincides with the appearance of Hydrodamalis and other dugongids in the same localities and habitats they occupied (Figure 12). Additional data on the paleoecology of these lineages and climatic changes of the region need to be conducted in order to test this hypothesis. ...
Context 2
... correlations support the hypotheses of the extinction of Desmostylia being mostly driven by the colonization of the North Pacific by Sirenia. By looking at distribution maps of the main genera for these groups in this area, it appears clear that the appearance of the genus Hydrodamalis in the Tortonian (~11 Ma) coincides with the decline of desmostylians, which went completely extinct by the end of the Tortonian (7.2 Ma) ( Figure 12). While other variables connected with changes in climate and primary productivity (e.g., δ 15 N) might be correlated with the diversity of herbivorous groups, their relatively low and stable numbers point to the fact that they occupy a specific ecological niche and are particularly vulnerable to competition. ...
Citations
... The fossil record reveals that pinnipeds were more taxonomically diverse in the geologic past, and included an extinct family, the Desmatophocidae (a clade phylogenetically related to Phocidae), and some early diverging lineages of stem taxa such as Enaliarctos, Pteronarctos, and Pinnarctidion. Whereas aspects of their macroevolutionary history have received considerable attention (e.g., the origin of polygyny or the evolution of their body size), one aspect of their paleoecology has been comparatively understudied: the origin and evolution of their foraging ecology Berta and Lanzetti, 2020). ...
... In contrast, later diverging taxa (e. g., Ontocetus) are inferred to have been coastal and benthic feeders, analogous to living walruses (Magallanes et al., 2018;Deméré, 1994;Boessenecker, 2017). Likewise, a range of ecomorphologies have been proposed for extinct phocids (e.g., Koretsky, 2001), and otariids (e.g., Berta and Lanzetti, 2020), although without offering specific tests of their past foraging ecology or habitat preferences. ...
... Liow et al. 2015) often include pinnipeds, but have not examined intra-clade patterns of speciation and extinction. Generic counts of pinniped Downloaded from https://academic.oup.com/evolut/advance-article/doi/10.1093/evolut/qpae061/7655703 by bibliotheque universitaire de poitiers user on 26 April 2024 A c c e p t e d M a n u s c r i p t diversity suggest an increase in taxa until a peak in the mid-Miocene followed by a decrease until the Pliocene when the diversification of extant genera begins (Berta & Lanzetti 2020). Pinniped biogeography has been studied more extensively than their diversification dynamics. ...
Pinnipeds (seals, sea lions, walruses, and their fossil relatives) are one of the most successful mammalian clades to live in the oceans. Despite a well-resolved molecular phylogeny and a global fossil record, a complete understanding of their macroevolutionary dynamics remains hampered by a lack of formal analyses that combine these 2 rich sources of information. We used a meta-analytic approach to infer the most densely sampled pinniped phylogeny to date (36 recent and 93 fossil taxa) and used phylogenetic paleobiological methods to study their diversification dynamics and biogeographic history. Pinnipeds mostly diversified at constant rates. Walruses, however, experienced rapid turnover in which extinction rates ultimately exceeded speciation rates from 12 to 6 Ma, possibly due to changing sea levels and/or competition with otariids (eared seals). Historical biogeographic analyses, including fossil data, allowed us to confidently identify the North Pacific and the North Atlantic (plus or minus Paratethys) as the ancestral ranges of Otarioidea (eared seals + walrus) and crown phocids (earless seals), respectively. Yet, despite the novel addition of stem pan-pinniped taxa, the region of origin for Pan-Pinnipedia remained ambiguous. These results suggest further avenues of study in pinnipeds and provide a framework for investigating other groups with substantial extinct and extant diversity.
... Acrophoca is distinguished by having a relatively large body size (>2 m; Churchill et al. 2015) and a long-snouted skull with a flexible neck, resembling the morphology of leopard seals (Hydrurga leptonyx). Acrophoca has been categorised as a generalist piscivorous pierce feeder based on their tooth morphology, with a predominant hind-limb swimming mode based on their pelvis and hind-flipper morphology (Adam and Berta 2002;Berta and Lanzetti 2020;Berta et al. 2022). Compared to Acrophoca, Piscophoca has a more robust cranial morphology with indicators of stronger muscle insertions and is interpreted as a piscivorous pierce feeder predator similar to extant monk seals (Monachus and Neomonachus) (Adam and Berta 2002;Berta and Lanzetti 2020). ...
... Acrophoca has been categorised as a generalist piscivorous pierce feeder based on their tooth morphology, with a predominant hind-limb swimming mode based on their pelvis and hind-flipper morphology (Adam and Berta 2002;Berta and Lanzetti 2020;Berta et al. 2022). Compared to Acrophoca, Piscophoca has a more robust cranial morphology with indicators of stronger muscle insertions and is interpreted as a piscivorous pierce feeder predator similar to extant monk seals (Monachus and Neomonachus) (Adam and Berta 2002;Berta and Lanzetti 2020). Hadrokirus martini Amson and de Muizon 2014 represents a third extinct phocid species from the eastern South Pacific, and it is currently known solely from remains from the late Miocene of the Pisco Formation. ...
... Although finer categories are possible, they bring substantial uncertainty in scoring, particularly with fossil data. Categories were based on Jefferson et al. 87 and Lanzetti and Berta 88 with scorings for fossil taxa based on species-specific reconstructions in the literature (Table S2). Mandibular dentition was allocated to three categories: heterodont, homodont, and reduced. ...
... 38 Finally, habitat was categorized as predominantly coastal, predominantly coastal-pelagic, riverine (solely freshwater), or pelagic and based on categories used in Perrin et al., 89 Jefferson et al., 87 and Berta and Lanzetti. 88 Species were categorised by the habitat they predominantly inhabit. Populations of Irrawaddy dolphin (Orcaella brevirostris) dwell in freshwater, thus, models were also run with this species coded as riverine and separately as coastal. ...
Toothed whales (odontocetes) emit high-frequency underwater sounds (echolocate)—an extreme and unique innovation allowing them to sense their prey and environment. Their highly specialized mandible (lower jaw) allows high-frequency sounds to be transmitted back to the inner ear. Echolocation is evident in the earliest toothed whales, but little research has focused on the evolution of mandibular form regarding this unique adaptation. Here, we use a high-density, three-dimensional geometric morphometric analysis of 100 living and extinct cetacean species spanning their ∼50-million-year evolutionary history. Our analyses demonstrate that most shape variation is found in the relative length of the jaw and the mandibular symphysis. The greatest morphological diversity was obtained during two periods of rapid evolution: the initial evolution of archaeocetes (stem whales) in the early to mid-Eocene as they adapted to an aquatic lifestyle, representing one of the most extreme adaptive transitions known, and later on in the mid-Oligocene odontocetes as they became increasingly specialized for a range of diets facilitated by increasingly refined echolocation. Low disparity in the posterior mandible suggests the shape of the acoustic window, which receives sound, has remained conservative since the advent of directional hearing in the aquatic archaeocetes, even as the earliest odontocetes began to receive sounds from echolocation. Diet, echolocation, feeding method, and dentition type strongly influence mandible shape. Unlike in the toothed whale cranium, we found no significant asymmetry in the mandible. We suggest that a combination of refined echolocation and associated dietary specializations have driven morphology and disparity in the toothed whale mandible.
... To verify the relationship between morphological convergence and feeding performance, we compiled prey size classes from previous literature [2,3,34]. Relative prey sizes reflect the dietary sources and are calculated by dividing the maximum length of the longest prey species by the maximum length of the predator [2]. ...
... The morphological convergence between Hupehsuchus and mysticetes is matched by association with prey size (Fig. 4B). Almost all mysticetes prey on tiny-sized zooplankton, whereas odontocetes, pinnipeds, and birds prey on small to middle-sized invertebrates, squids and fishes [34]. Odontocetes and crocodilians select prey over a wide size range, from small fish to large tetrapods, some reaching apex predatory niches, such as Orcinus orca and Crocodylus porosus [41,42]. ...
... Although the modern baleen whales are all large filter feeders, they feed quite differently in terms of strategy and food preference [34,49]. The balaenopterid whales, also known as rorquals, employ a lunge filter feeding style in which they swim rapidly at a prey patch while opening their mouth to gulp the mixture of water and prey, then filter the water through the baleen plates and swallow the retained prey [44,63,64]. ...
Modern baleen whales are unique as large-sized filter feeders, but their roles were replicated much earlier by diverse marine reptiles of the Mesozoic. Here, we investigate convergence in skull morphology between modern baleen whales and one of the earliest marine reptiles, the basal ichthyosauromorph Hupehsuchus nanchangensis, from the Early Triassic, a time of rapid recovery of life following profound mass extinction. Two new specimens reveal the skull morphology especially in dorsal view. The snout of Hupehsuchus is highly convergent with modern baleen whales, as shown in a morphometric analysis including 130 modern aquatic amniotes. Convergences in the snout include the unfused upper jaw, specialized intermediate space in the divided premaxilla and grooves around the labial margin. Hupehsuchus had enlarged its buccal cavity to enable efficient filter feeding and probably used soft tissues like baleen to expel the water from the oral cavity. Coordinated with the rigid trunk and pachyostotic ribs suggests low speeds of aquatic locomotion, Hupehsuchus probably employed continuous ram filter feeding as in extant bowhead and right whales. The Early Triassic palaeoenvironment of a restrictive lagoon with low productivity drove Hupehsuchus to feed on zooplankton, which facilitated ecosystem recovery in the NanzhangYuan’an Fauna at the beginning of the Mesozoic.
... One specimen of an adult Lagenorhynchus albirostris (NHMO-DMA-32381) and one juvenile Hyperoodon ampullatus (NHMO-DMA-29427) were scanned at the Natural History Museum, University of Oslo. Lagenorhynchus uses several feeding mechanisms (raptorial, crushing, suction), H. ampullatus is a suction-feeding ziphiid with a blunt head and reduced dentition, with a diet primarily of squid (Heyning and Mead 1996;Werth 2006a;Berta and Lanzetti 2020). ...
The hyoid apparatus is essential for underwater feeding in marine tetrapods, but it is unclear whether this complex has evolved as convergently as other traits, such as dentition or locomotion. Here we compare the ossified hyoid elements in ophthalmosaurid ichthyosaurs and odontocete cetaceans, two groups with an overall similar body shape, to understand whether the hyoid elements show any signs of convergence in the context of feeding. We examined three types of data (size, morphology, and internal bone microstructure) in ophthalmosaurid and odontocete taxa in which these elements are preserved. Our data show that ichthyosaurs never experienced a shift in feeding mode, which might indicate that their hyoid apparatus never adapted to suction feeding. Also, the internal microstructure of the two animal groups differs; where the odontocetes have an overall less compact structure, ophthalmosaurid ichthyosaurs have cancellous inner cones in an outer, more compact sheath. These differences are likely explained as biomechanical adaptations to different feeding modes. Thus, the hyoid changed less and acted more as a constraint for feeding innovation in ichthyosaurs compared with cetaceans, and through a much longer time span (more than 150 Myr).
... The study of the fossil record revealed that the past mysticete diversity reached levels unrivalled in present time (Berta and Lanzetti, 2020;Bisconti et al., 2019;Marx and Uhen, 2010) suggesting that structural aspects of the oceanic ecosystems of the last million years should have been profoundly different from today. Genetic analyses revealed that the exceptionally high numbers of individuals were in existence slightly before the beginning of the industrial whaling (e.g., Roman and Palumbi, 2003;Rooney et al., 2001) in at least four species (Balaena mysticetus, Balaenoptera acutorostrata, B. physalus and Megaptera novaeangliae). ...
... Rather, the extinct species created vacant niches although it is unlikely that these niches were occupied by chaeomysticetes as the feeding styles of the latter were very different from those of the earliest mysticetes. The key morphological synapomorphy of Chaeomysticeti, in fact, is the presence of baleen ) that allows the performance of filter feeding in contrast to the earliest mysticetes that used a combination of biting and suction to mainly prey upon fishes (Berta and Lanzetti, 2020). Possible overlap in feeding styles could have been present between the archaic, toothed-mysticetes and the chaeomysticetes in the case in which the coexistence of teeth and baleen would be definitely accepted in Aetiocetidae (as proposed by Deméré et al., 2008 and reiterated by Ekdale and Deméré, 2021;and Gatesy et al., 2022). ...
... 2) corresponds to a Tortonian peak in mysticete diversity that is mainly due to a massive expansion of balaenopterid diversity; this peak is recognized as one of the most important diversification events in the history of mysticetes (Berta and Lanzetti, 2020;Bisconti et al., 2019;Marx and Uhen, 2010). The third event (No. 3) corresponds to a Pliocene peak in diversity attained by both Balaenopteridae and Balaenidae recognized also by Berta and Lanzetti (2020) and Marx and Uhen (2010). ...
... The study of the fossil record revealed that the past mysticete diversity reached levels unrivalled in present time (Berta and Lanzetti, 2020;Bisconti et al., 2019;Marx and Uhen, 2010) suggesting that structural aspects of the oceanic ecosystems of the last million years should have been profoundly different from today. Genetic analyses revealed that the exceptionally high numbers of individuals were in existence slightly before the beginning of the industrial whaling (e.g., Roman and Palumbi, 2003;Rooney et al., 2001) in at least four species (Balaena mysticetus, Balaenoptera acutorostrata, B. physalus and Megaptera novaeangliae). ...
... Rather, the extinct species created vacant niches although it is unlikely that these niches were occupied by chaeomysticetes as the feeding styles of the latter were very different from those of the earliest mysticetes. The key morphological synapomorphy of Chaeomysticeti, in fact, is the presence of baleen ) that allows the performance of filter feeding in contrast to the earliest mysticetes that used a combination of biting and suction to mainly prey upon fishes (Berta and Lanzetti, 2020). Possible overlap in feeding styles could have been present between the archaic, toothed-mysticetes and the chaeomysticetes in the case in which the coexistence of teeth and baleen would be definitely accepted in Aetiocetidae (as proposed by Deméré et al., 2008 and reiterated by Ekdale and Deméré, 2021;and Gatesy et al., 2022). ...
... 2) corresponds to a Tortonian peak in mysticete diversity that is mainly due to a massive expansion of balaenopterid diversity; this peak is recognized as one of the most important diversification events in the history of mysticetes (Berta and Lanzetti, 2020;Bisconti et al., 2019;Marx and Uhen, 2010). The third event (No. 3) corresponds to a Pliocene peak in diversity attained by both Balaenopteridae and Balaenidae recognized also by Berta and Lanzetti (2020) and Marx and Uhen (2010). ...
... Therefore, a more comprehensive study for 'kentriodontids,' especially their phylogenetic relationships, is necessary to refine the systematics of 'kentriodontids.' In addition to the phylogenetic relationships, previous studies on 'kentriodontids' suggested that their ecological niche was thought to be similar to the extant delphinoids [10,11]. They show high diversity through the late Early and early Late Miocene, and their high diversity during those periods is thought to be parallel to the present day Delphinoidea. ...
... Previous studies [12,13] have suggested that the origin and early diversification of the Delphinoidea were recognized in the Middle to Late Miocene. Although Delphinoidea have been considered to have the same ecological niches as environmental preferences [10] and feeding strategies [11] with most of the Kentriodontoidea, the absence of the Delphinoidea in the Middle Miocene might have been the result of niche partitioning based on our phylogenetic and paleobiogeographic analysis. Similar to some research [4], the results suggest that the Kentriodontoidea might have declined in their niche by the diversification of the Delphinoidea in the Late Miocene. ...
So–called ‘kentriodontids’ are extinct dolphin–like odontocetes known from the Early to Late Miocene worldwide. Although recent studies have proposed that they were monophyletic, their taxonomic relationships still remain controversial. Such a controversy exists partly because of the predominance of primitive morphologies in this taxon, but the fact is that quite a few ‘kentriodontids’ are known only from fragmentary skulls and/or isolated periotics. A new ‘kentriodontid’ Platysvercus ugonis gen. et sp. nov. is described based on a nearly complete skull from the upper Lower Miocene Sugota Formation, Akita Prefecture, northern Japan. Based on the phylogenetic analysis of P. ugonis described here, the monophyly of the ‘kentriodontids’ is confirmed, and it is recognized as the superfamily Kentriodontoidea. This new superfamily is subdivided into two families as new ranks: Kentriodontidae and Lophocetidae. Based on the paleobiogeographic analysis of the Kentriodontoidea, their common ancestor emerged in the North Pacific Ocean and spread over the Northern Hemisphere. Initial diversification of the Kentriodontidae in the North Pacific Ocean and the Lophocetidae in the North Atlantic Ocean was recognized as a vicariance event. The diversification and extinction of the Kentriodontoidea could have been synchronously influenced by climate events during the Middle Miocene.
... The evolution of the Mysticeti feeding strategy in the toothed baleen whale has been well studied recently, using the morphology of the tooth, skull and mandible. Before baleen-assisted filter feeding was evolved, toothed mysticetes employed variable feeding strategies, such as suction, suction-assisted filter and suction-assisted raptorial feeding [7][8][9][10][11][12][13][14]. ...
... In the head, the rostrum, palate, temporomandibular joint and teeth/baleen in particular are associated with feeding strategy [14]. Previous studies have focused on the mandible, especially in the Cetotheriidae and Balaenopteridae [23][24][25][26][27][28][29][30]. ...
Baleen whales have lost their functional teeth and begun to use their baleen plates to feed on small prey. Modern baleen whales exhibit different types of feeding strategies, such as lunging, skimming and so on. The evolution of feeding strategy in the Chaeomysticeti is an important step in considering niche partitioning and diversification, feeding efficiency and gigantism, and evolution and extinction. This study analyses the rostrum morphology to test the hypothesis that specific rostral morphologies facilitate special feeding strategies, using modern species and their observed feeding strategies. By this means, the convergence of rostral morphology can be recognized in the closest groups in the morphospace. As a result, the two linages (Balaenidae and Caperea marginata) are recognized to have convergent rostral morphology. In addition, an early member of the Chaeomysticeti, Yamatocetus canaliculatus, and most fossil species are plotted in or close to the cluster of lunge feeders. The original feeding strategy of the Chaeomysticeti could be more similar to lunge feeding than to skim feeding. Fossil relatives of the two linages showing transitional conditions indicate that they shifted to skim feeding independently. The evolution of the feeding strategy of the Chaeomysticeti is possibly more complex than that was thought.
