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Bony outgrowths on the jaws of an extinct sperm whale support macroraptorial feeding in several stem physeteroids

Authors:
Olivier Lambert at Royal Belgian Institute of Natural Sciences
Olivier Lambert
Giovanni Bianucci at Università di Pisa
Giovanni Bianucci
Brian Beatty at New York Institute of Technology
Brian Beatty
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Abstract

Several 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.
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... During the same epoch, high trophic levels of predation like those of the modern killer whale have been proposed for some fossil relatives of the modern sperm whales (superfamily Physeteroidea) (Bianucci and Landini 2006;Lambert et al. 2008Lambert et al. , 2010Lambert et al. , 2017. Differently from the extant physetheroids (i.e., the sperm whale Physeter macrocephalus, the dwarf sperm whale Kogia sima, and the pygmy sperm whale K. breviceps), which feed nearly exclusively upon cephalopods by suction generated through the mouth in Kogia and directly within the oropharynx in Physeter (Werth 2004(Werth , 2006a(Werth , 2006bBloodworth and Marshall 2005), these putatively macroraptorial, extinct forms likely preyed upon marine vertebrates using robust jaws and large teeth to grasp their food items (Bianucci and Landini 2006;Lambert et al. 2008Lambert et al. , 2010Lambert et al. , 2014Lambert et al. , 2017Hocking et al. 2017;Lambert and Bianucci 2019;Peri et al. 2020). This hypothesis is based on various cranial features displayed by the macroraptorial Physeteroidea, including a wide temporal fossa, well-developed maxillary teeth (only mandibular teeth are functional in extant sperm whales) and, as observed on the holotype of Acrophyseter robustus, bony exostoses in correspondence of upper cheek teeth (Bianucci and Landini 2006;Lambert et al. 2008Lambert et al. , 2010Lambert et al. , 2014Lambert and Bianucci 2019;Peri et al. 2020). ...
... Differently from the extant physetheroids (i.e., the sperm whale Physeter macrocephalus, the dwarf sperm whale Kogia sima, and the pygmy sperm whale K. breviceps), which feed nearly exclusively upon cephalopods by suction generated through the mouth in Kogia and directly within the oropharynx in Physeter (Werth 2004(Werth , 2006a(Werth , 2006bBloodworth and Marshall 2005), these putatively macroraptorial, extinct forms likely preyed upon marine vertebrates using robust jaws and large teeth to grasp their food items (Bianucci and Landini 2006;Lambert et al. 2008Lambert et al. , 2010Lambert et al. , 2014Lambert et al. , 2017Hocking et al. 2017;Lambert and Bianucci 2019;Peri et al. 2020). This hypothesis is based on various cranial features displayed by the macroraptorial Physeteroidea, including a wide temporal fossa, well-developed maxillary teeth (only mandibular teeth are functional in extant sperm whales) and, as observed on the holotype of Acrophyseter robustus, bony exostoses in correspondence of upper cheek teeth (Bianucci and Landini 2006;Lambert et al. 2008Lambert et al. , 2010Lambert et al. , 2014Lambert and Bianucci 2019;Peri et al. 2020). Furthermore, the teeth of these fossil sperm whales exhibit deep occlusal facets, which are sulci on the tooth surface produced by repeated tooth-totooth contacts (attritional wear), and fractures attributed to strong occlusion or to the contact with hard material (e.g., bone) (Bianucci and Landini 2006;Lambert et al. 2017;Lambert and Bianucci 2019;Peri et al. 2020). ...
... 20°, measured from Snively et al. 2015: Figure 1a) and Carcharodon carcharias (35°; Wroe et al. 2008), thus allowing for robust comparisons of bite force values in these marine predator species. As origin of the temporalis muscle, we chose the entire surface of the temporal fossa (Figure 1), following the reconstruction proposed by Lambert et al. (2014) for Acrophyseter robustus and the muscular anatomy of extant odontocetes (Von Schulte and De Forest Smith 1918; Seagars 1982). ...
Biting in the Miocene seas: estimation of the bite force of the macroraptorial sperm whale Zygophyseter varolai using finite element analysis
Article
Full-text available
  • Oct 2021
  • Ichnos
Differing from the extant physeteroids, macroraptorial sperm whales are currently regarded as apex predators of the Miocene seas based on several morphofunctional observations. Here, we estimate the bite force of Zygophyseter varolai, a macroraptorial physeteroid from lower upper Miocene strata of the Pietra leccese formation (Apulia, Italy) using the finite element analysis (FEA). To explore multiple bite scenarios, we set four different load cases on a 3D model of the cranium obtained via digital photogram-metry, considering the temporalis and masseter muscles as jaw adductors. Our FEA simulations indicate that Z. varolai exerted an anterior bite force of more than 4000 N and a posterior bite force of more than 10000 N. These values are similar to those estimated for other marine predators known for their powerful bite. This suggests that Z. varolai might have fed upon medium-sized marine vertebrates like other odontocetes. Considering the significant difference observed between the anterior and posterior bite forces, Z. varolai likely fed via 'grip-and-shear' feeding, snapping the food items with an anterior bite and then cutting them with a powerful posterior bite. Other macroraptorial sperm whales such as the roughly coeval Acrophyseter from Peru likely employed the same feeding technique. ARTICLE HISTORY
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... The ecotrophic role of Acrophyseter, Livyatan and allied forms has often been investigated by means of functional morphology and biomechanics (Bianucci & Landini, 2006;Lambert et al., 2008Lambert et al., , 2010bLambert et al., , 2014aLambert et al., , 2017aPeri et al., 2020Peri et al., , 2021. All these studies suggested a macrophagous feeding style that involved both biting and shearing (e.g., Acrophyseter) or tearing (e.g., Livyatan), thus strikingly contrasting with the strong suction feeding specialisation seen in Recent sperm whales (e.g., Bloodworth and Marshall, 2005 no direct evidence for the trophic ecology of these forms (e.g., bite marks or fossilised stomach contents) has emerged from the fossil record to date. ...
... During the Late Miocene, the macroraptorial stem physeteroids of the Pisco embayment ranged between medium-sized (Acrophyseter, 4-4.5 metres long) and gigantic (Livyatan, 13.5-17.5 metres long) forms (Bianucci and Landini, 2006;Lambert et al., 2014a), thus likely foraging on a similarly broad range of potential prey items. As already highlighted elsewhere (e.g., Bianucci & Landini, 2006;Lambert et al., 2017a;Collareta et al., 2021b), only the killer whale Orcinus orca (Linnaeus, 1758) could be evoked as a possible extant analogue for Acrophyseter, Livyatan, and allied stem physeteroids. ...
An overview of the fossil record of cetaceans from the East Pisco Basin (Peru)
Article
Full-text available
  • Jun 2022
The East Pisco Basin is one of the forearc basins that formed during the Cenozoic along the coast of Peru due to the subduction of the Farrallon-Nazca plate beneath the South American plate. The sedimentary fi ll of this basin is extensively exposed along the coastal Ica Desert, and includes a succession of Eocene to Pliocene marine sediments that account for a ~50-myr-long history of semi-continuous deposition. These rocks are characterized by an outstanding fossil content that remarkably contributed to our understanding of the evolutionary history of the main groups of Cenozoic marine vertebrates. In the Ica desert, the most common and signifi cant vertebrate remains belong to cetaceans. Knowledge on the fossil cetaceans of the East Pisco Basin has grown dramatically in the last fi fteen years thanks to several international research projects involving, among many others, the authors of the present article. These research eff orts have led to the discovery of several hundred fossil skeletons, the most signifi cant of which have been collected, prepared and partly published. Furthermore, interdisciplinary studies were also conducted in order to provide a high resolution chronostratigraphic framework for this fossil record. Remarkable cetacean specimens (42.6 Ma) Yumaque strata are home to the quadrupedal protocetid archaeocete Peregocetus pacifi cus, which documents the fi rst arrival of cetaceans in the Pacifi c Ocean. Geologically younger (36.4 Ma) Yumaque deposits have yielded the holotype skeleton of Mystacodon selenesis, the oldest mysticete ever found. This ancestor of the modern baleen whales had a skull provided with a complete dentition and retained hindlimbs, albeit reduced in size. In the Otuma Formation, a nine-m-long basilosaurid (Cynthiacetus peruvianus) has been discovered. The Chilcatay Formation records the fi rst great radiation of the odontocetes, represented by Inticetidae (Inticetus vertizi), basal Platanidelphidi (Ensidelphis riveroi), Squalodelphinidae (Furcacetus fl exirostrum, Huaridelphis raimondii, Macrosqualodelphis ukupachai and Notocetus vanbenedeni), Platanistidae (aff. Araeodelphis), Physeteroidea (Rhaphicetus valenciae and cf. Diaphorocetus), Chilcacetus cavirhinus, indeterminate Eurinodelphinidae, and Kentriodontidae (Kentriodon). Overall, this roughly coeval assemblage displays a considerable disparity in terms of skull shape and body size that is possibly related to the development of diff erent trophic strategies, ranging e.g., from suction to raptorial feeding. In the Pisco Formation, starting from P0, the baleen-bearing whales (Chaeomysticeti) represent the most frequent cetacean fossils (only a few mysticetes are known from the Chilcatay strata). Two chaeomysticete lineages are found in the Pisco Formation: Cetotheriidae (from Tiucetus rosae in P0 to Piscobalaena nana in P2) and Balaenopteroidea (from Pelocetus in P0 to several undescribed species of Balaenopteridae in P2, testifying to a progressive trend toward gigantism). Odontocetes are rare in P0, the "kentriodontid" Incacetus broggii being the only species described from these strata, but they become more abundant and diverse in P1 and P2. In P1, the commonest toothed whale is Messapicetus gregarius, a member of Ziphiidae featuring an extremely elongated rostrum and a complete set of functional teeth. Another ziphiid from P1 is Chimuziphius coloradensis, known only from the fragmentary holotype cranium. The P1 strata also record the appearance of the crown Delphinida, with the superfamily Inioidea being represented by two small pontoporiids (Brachydelphis mazeasi and Samaydelphis chacaltanae) and one iniid (Brujadelphis ankylorostris). Moreover, P1 is also home to the stem physeteroid Livyitan melvillei; featuring a three-m-long skull and teeth reaching 36 cm in length, L. melvillei was one of the largest raptorial predators and, possibly, the biggest tetrapod bite ever found. Acrophyseter is another macroraptorial sperm whale, distinctly smaller than L. melvillei, known from both P1 and P2. Even smaller in size are the kogiids Platyscaphokogia landinii and Scaphokogia cochlearis, both of which are known from the upper strata of P2. The same allomember is also home to the ziphiids Chavinziphius maxillocristatus and Nazcacetus urbinai, the "kentriodontids" Atocetus iquensis and Belenodelphis peruanus, and undescribed members of Phocoenidae.
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... Odontocetes are less abundant but seemingly more diverse. They include stem physeteroids (Acrophyseter sp. and a large undescribed species [16,30,80,101]), scaphokogiine kogiids (Scaphokogia cochlearis and Platyscaphokogia landinii [102]), ziphiids (Chavinziphius maxillocristatus, Nazcacetus urbinai, and two unnamed species [25,79,84]), the phocoenid cf. Lomacetus ginsburgi, and other porpoise-like delphinoids ( Figure 8C,D) [25,30]. ...
... The ecology of "macroraptorial" sperm whales like Livyatan has been inferred from their functional anatomy, and is thought to have involved biting and tearing or shearing of large prey, rather than suction feeding [20,80,101,[131][132][133]. There is, however, as yet no direct evidence for this idea in the form of bite marks or fossilised stomach contents. ...
Vertebrate Palaeoecology of the Pisco Formation (Miocene, Peru): Glimpses into the Ancient Humboldt Current Ecosystem
Article
Full-text available
  • Oct 2021
The northward-flowing Humboldt Current hosts perpetually high levels of productivity along the western coast of South America. Here, we aim to elucidate the deep-time history of this globally important ecosystem based on a detailed palaeoecological analysis of the exceptionally preserved middle–upper Miocene vertebrate assemblages of the Pisco Formation of the East Pisco Basin, southern Peru. We summarise observations on hundreds of fossil whales, dolphins, seals, seabirds, turtles, crocodiles, sharks, rays, and bony fishes to reconstruct ecological relationships in the wake of the Middle Miocene Climatic Optimum, and the marked cooling that followed it. The lowermost, middle Miocene Pisco sequence (P0) and its vertebrate assemblage testify to a warm, semi-enclosed, near-shore palaeoenvironment. During the first part of the Tortonian (P1), high productivity within a prominent upwelling system supported a diverse assemblage of mesopredators, at least some of which permanently resided in the Pisco embayment and used it as a nursery or breeding/calving area. Younger portions of the Pisco Formation (P2) reveal a more open setting, with wide-ranging species like rorquals increasingly dominating the vertebrate assemblage, but also local differences reflecting distance from the coast. Like today, these ancient precursors of the modern Humboldt Current Ecosystem were based on sardines, but notably differed from their present-day equivalent in being dominated by extremely large-bodied apex predators like Livyatan melvillei and Carcharocles megalodon.
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... This evidence allows for reconstructing putative trophic levels and comparison with modern conditions. Raptorial sperm whales (e.g., Acrophyseter, Livyatan) were probably the top mammalian predators in the Pisco ecosystem throughout the middle Miocene-early Pliocene, a trophic position now occupied by the killer whale, Orcinus orca (Lambert et al. 2014(Lambert et al. , 2016. These animals are considered as macroraptorial feeders (i.e., they consume large preys). ...
... The largest raptorial sperm whale, Livyatan, would have reached up to 16 m and preyed upon medium-sized baleen whales (Lambert et al. 2010). Anatomical features supporting these interpretations are based on their large to giant size, massive teeth, presence of buccal maxillary exostoses, robust jaws, and powerful temporal muscles (Lambert et al. 2010(Lambert et al. , 2014). Yet, bite-marked bones attributed to their active hunting or scavenging behavior have not been found. ...
Late Neogene evolution of the Peruvian margin and its ecosystems: a synthesis from the Sacaco record
Article
Full-text available
  • Mar 2021
The highly productive waters of the Humboldt Current System (HCS) host a particular temperate ecosystem within the tropics, whose history is still largely unknown. The Pisco Formation, deposited during Mio-Pliocene times in the Peruvian continental margin has yielded an outstanding collection of coastal-marine fossils, providing an opportunity to understand the genesis of the HCS ecosystem. We present a comprehensive review, completed with new results, that integrates geological and paleontological data from the last 10 My, especially focusing on the southern East Pisco Basin (Sacaco area). We discuss the depositional settings of the Pisco Formation and integrate new U/Pb radiometric ages into the chronostratigraphic framework of the Sacaco sub-basin. The last preserved Pisco sediments at Sacaco were deposited ~ 4.5 Ma, while the overlying Caracoles Formation accumulated from ~ 2.7 Ma onwards. We identified a Pliocene angular unconformity encompassing 1.7 My between these formations, associated with a regional phase of uplift. Local and regional paleoenvironmental indicators suggest that shallow settings influenced by the offshore upwelling of ventilated and warm waters prevailed until the early Pliocene. We present an extensive synthesis of the late Miocene–Pleistocene vertebrate fossil record, which allows for an ecological characterization of the coastal-marine communities, an assessment of biodiversity trends, and changes in coastal-marine lineages in relation to modern HCS faunas. Our synthesis shows that: (i) typical endemic coastal Pisco vertebrates persisted up to ~ 4.5 Ma, (ii) first modern HCS toothed cetaceans appear at ~ 7–6 Ma, coinciding with a decline in genus diversity, and (iii) a vertebrate community closer to the current HCS was only reached after 2.7 Ma. The genesis of the Peruvian coastal ecosystem seems to be driven by a combination of stepwise transformations of the coastal geomorphology related to local tectonic pulses and by a global cooling trend leading to the modern oceanic circulation system.
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... of Odontocetes from Mysticetes around 30 Mya (Thewissen & Williams, 2002), many of the larger predators, such as Otodus megalodon (Shimada et al., 2016;Pimiento et al., 2017;Cooper et al., 2022) and a large physeteroid (sperm whale) (Kimura et al., 2006;Lambert et al., 2014;Peri et al., 2022) disappeared around the end of the Pliocene, a period marked by climatic variability and sea-level fluctuations (Pimiento et al., 2017). The earliest known fossil of a killer whale, O. citonensis, dates back to the Pliocene Epoch (5.3 million to 2.6 Mya) and was only about 4 m in length, similar in size to a typical dolphin (Galatius et al., 2020). ...
Investigating the Relationship Between Body Shape and Life History Traits in Toothed Whales: Can Body Shape Predict Fast-Slow Life Histories?
Article
Full-text available
  • May 2023
  • EVOL BIOL
Unlabelled: A widespread pattern in vertebrate life-history evolution is for species to evolve towards either fast or slow life histories; however, the underlying causes of this pattern remain unclear. Toothed whales (Odontoceti) are a diverse group with a range of body sizes and life histories, making them an ideal model to investigate potential drivers of this dichotomy. Using ancestral reconstruction, we identified that certain groups of odontocetes evolved more-streamlined, presumably faster, body shapes around the same time that killer whales (Orcinus orca) evolved into whale predators approximately 1 Mya during the Pleistocene. This suggests that the evolution of a streamlined body shape may have been an adaptation to escape killer whale predation, leading to longer life-history events. To test this hypothesis, we performed a cluster analysis of odontocete whales and confirmed the dual pattern of life-history traits, with one group referred to as 'reproducers' characterized by early age of maturity, short gestation, short interbirth interval, and short lifespan, and the other group referred to as 'bet-hedgers' exhibiting the opposite pattern. However, we found that life history grouping was relatively unrelated to whale shape (i.e., more streamlined or less streamlined). Therefore, we incorporated principal component results into mixed effects models, and the model results indicated that body shape was positively related to neonate length (a measure of investment in progeny), but not significantly related to the temporal life-history traits. Thus, whale body shape is not a sufficient explanation for the evolution of fast-slow life histories in odontocete whales. Supplementary information: The online version contains supplementary material available at 10.1007/s11692-023-09605-4.
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... Because an enlarged hyoid is an obvious indicator of suction feeding, its presence or absence in fossil cetaceans provides a clear signal of the feeding mode of extinct taxa, and a gauge of the extent to which archaeocetes or crown cetacean lineages had made the transition from terrestrial to fully aquatic feeding, and of the feeding mechanisms they employed. Given that there is an extensive fossil record of physeterids with apparent ecological diversity, including many macroraptorial forms (Lambert et al., 2010(Lambert et al., , 2014, any evidence of hyoid enlargement would, even in the absence of dentition, provide useful information as to feeding methods. Unfortunately, the hyoid skeleton is not always recovered with cranial and postcranial fossils, just as it is not always recovered from carcasses by neomorphologists, and it is often missing from skeletal specimens and mounted displays (Werth, 2006b). ...
Osteological correlates of evolutionary transitions in cetacean feeding and related oropharyngeal functions
Article
Full-text available
  • Apr 2023
Teeth are often the first structures that anatomists and paleontologists examine to understand the ecology and morphology of feeding, both because teeth are highly specialized structures that provide precise information, and because they are among the best and most commonly preserved fossils. Unfortunately, many fragmentary fossil and recent specimens lack teeth, and some come from edentulous individuals and taxa, as in mysticete (baleen) whales. In our broad comparative review, we survey non-dental osteological features that, due to size, shape, arrangement, and surface features reflecting muscle attachments, provide useful clues to general or specific aspects of prey capture, intraoral transport, processing, or swallowing. We focus on hyoid, palatal, and pterygoid bones, mandibular symphyses and processes such as the coronoid, and the temporal fossa and zygomatic arch, as well as adjacent cranial bones relating to oral and pharyngeal anatomy. These bones relate to muscles of five general locations especially indicative of feeding: mandibular, hyoid, tongue, pharyngeal, and facial regions. Together these bones and muscles affect feeding and related activities including suckling and breathing. We discuss osteological correlates that provide special relevance to key transitions in cetacean evolutionary history, such as the shift from predominantly terrestrial to aquatic feeding, the shift from typical mammalian mastication to swallowing prey entirely or nearly whole, and the separation of respiratory and digestive passages. We also point to examples of modern specialists in these anatomical optima for different modes of prey capture, intraoral transport, processing, and swallowing. Although we focus on cetaceans, our approach is broadly relevant to all vertebrates, notably other marine tetrapods.
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... MUSM 4716 was collected by one of us (R.V.-M.) at the foot of Cerro La Bruja, a prominent vertebrate locality where both P1 and P2 are exposed [38,44,47,48,54,[93][94][95] ( Figure 1c). The GPS geographic coordinates of the finding site are the following: 14 • Figure 2) is a fragmentary chelonian carapace that measures 130 mm in maximum preserved width and 82 mm in maximum preserved length. ...
Ghosts of the Holobiont: Borings on a Miocene Turtle Carapace from the Pisco Formation (Peru) as Witnesses of Ancient Symbiosis
Article
Full-text available
  • Dec 2022
In spite of the widespread occurrence of epibiotic turtle barnacles (Coronuloidea: Chelonibiidae and Platylepadidae) on extant marine turtles (Chelonioidea: Cheloniidae and Dermochelyidae), and although the association between these cirripedes and their chelonian hosts has existed for more than 30 million years, only a few studies have investigated the deep past of this iconic symbiotic relationship on palaeontological grounds. We describe probable platylepadid attachment scars in the form of hemispherical/hemiellipsoidal borings on an Upper Miocene (Tortonian) fragmentary turtle carapace, identified herein as belonging to Cheloniidae, from the Pisco Lagerstätte (East Pisco Basin, southern Peru). When coupled with the available molecular data, this and other similar ichnofossils allow for hypothesising that platylepadid symbionts were hosted by sea turtles as early as in early Oligocene times and became relatively widespread during the subsequent Miocene epoch. Chelonian fossils that preserve evidence of colonisation by platylepadid epibionts in the form of pits on the turtle shell should be regarded as fossil holobionts, i.e., palaeontological witnesses of discrete communal ecological units formed by a basibiont and the associated symbionts (including the epibiota). A greater attention to the bone modifications that may be detected on fossil turtle bones is expected to contribute significantly to the emerging field of palaeosymbiology.
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... 32 Moving further back in time, several studies have investigated the possible impacts of macropredators on mysticete evolution, and vice versa. Particular attention has been devoted to extinct macroraptorial sperm whales 12,16,33,34 as well as to the ''megatooth'' shark Otodus megalodon. [34][35][36][37][38] In particular, the co-occurrence of several macropredators in the Miocene seas may have favored the emergence of gigantism in mysticetes, 16 whereas the quick decline of these predators and partly also of their prey (e.g., small baleen whales, such as cetotheriids) may reflect habitat loss consequent to global cooling. ...
The origins of the killer whale ecomorph
Article
  • Mar 2022
  • CURR BIOL
The killer whale (Orcinus orca) and false killer whale (Pseudorca crassidens) are the only extant cetaceans that hunt other marine mammals, with pods of the former routinely preying on baleen whales >10 m in length and the latter being known to take other delphinids. Fossil evidence for the origins of this feeding behavior is wanting, although molecular phylogenies indicate that it evolved independently in the two lineages. We describe a new extinct representative of the killer whale ecomorph, Rododelphis stamatiadisi, based on a partial skeleton from the Pleistocene of Rhodes (Greece). Five otoliths of the bathypelagic blue whiting Micromesistius poutassou are associated with the holotype, providing unexpected evidence of its last meal. The evolutionary relationships of R. stamatiadisi and the convergent evolution of killer whale-like features were explored through a broad-ranging phylogenetic analysis that recovered R. stamatiadisi as the closest relative of P. crassidens and O. orca as the only living representative of a once diverse clade. Within the clade of Orca and kin, key features implicated in extant killer whale feeding, such as body size, tooth size, and tooth count, evolved in a stepwise manner. The tooth wear in Rododelphis and an extinct species of Orcinus (O. citoniensis) are consistent with a fish-based diet, supporting an exaptative Pleistocene origin for marine mammal hunting in both lineages. If correct, predation by the ancestors of Pseudorca and Orca did not play a significant role in the evolution of baleen whale gigantism.
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... The alveoli display bony outgrowths. Lambert et al. (2014) described exostoses along some of the upper alveoli of Acrophyseter robustus (MUSM 1399), interpreting them as indicative of powerful bites. However, a bony outgrowth in M. chitaensis is observed in the anterior maxillary alveoli, whereas in A. robustus, the exostoses are not observed in anterior maxillary alveoli. ...
A new physeteroid from the lower Miocene of Japan
Article
  • Jan 2022
We describe a new specimen of physeteroid from the lower Miocene (Burdigalian) of Japan. This specimen was recovered from the Toyohama Formation, Chita County, Aichi Prefecture, Japan in 1984 and includes a finely preserved cranium with detached teeth and ear bones (periotic, tympanic bulla, and malleus). Here we refer this specimen to a new genus and species of the Physeteroidea, Miophyseter chitaensis gen. et sp. nov. Our phylogenetic analysis suggests that Miophyseter is a physeteroid more closely related to the crown Physeteroidea (Physeteridae and Kogiidae) than the macroraptorial physeteroids that flourished in middle and late Miocene times. A deep and large excavation on the ventral surface of the palatine and pterygoid in Miophyster suggests an adaptation for deep dives and/or the development of robust pterygoid muscles for active biting.
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Craniodental ecomorphology of the large Jurassic ichthyosaurian Temnodontosaurus
Article
  • Aug 2023
  • J ANAT
Marine amniotes have played many crucial roles in ocean ecosystems since the Triassic, including predation at the highest trophic levels. One genus often placed into this guild is the large Early Jurassic neoichthyosaurian Temnodontosaurus, the only post-Triassic ichthyosaurian known with teeth which bear a distinct cutting edge or carina. This taxonomically problematic genus is currently composed of seven species which show a wide variety of skull and tooth morphologies. Here we assess the craniodental disparity in Temnodontosaurus using a series of functionally informative traits. We describe the range of tooth morphologies in the genus in detail, including the first examples of serrated carinae in ichthyosaurians. These consist of false denticles created by the interaction of enamel ridgelets with the carinal keel, as well as possible cryptic true denticles only visible using scanning electron microscopy. We also find evidence for heterodonty in the species T. platyodon, with unicarinate mesial teeth likely playing a role in prey capture and labiolingually compressed, bicarinate distal teeth likely involved in prey processing. This type of heterodonty appears to be convergent with a series of other marine amniotes including early cetaceans. Overall, the species currently referred to as the genus Temnodontosaurus show a range of craniodental configurations allowing prey to be captured and processed in different ways - for example, T. eurycephalus has a deep snout and relatively small bicarinate teeth likely specialised for increased wound infliction and grip-and-tear feeding, whereas T. platyodon has a more elongate yet robust snout and larger teeth and may be more adapted for grip-and-shear feeding. These results suggest the existence of niche partitioning at higher trophic levels in Early Jurassic ichthyosaurians and have implications for future work on the taxonomy of this wastebasket genus, as well as for research into the ecology of other extinct megapredatory marine tetrapods.
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Developmental stability and skull lesions in the harbour seal (Phoca vitulina) in the 19th and 20th Centuries
Article
Full-text available
  • Sep 1997
Developmental stability in the Kattegat population of harbour seal (Phoca vitulina) was assessed to determine whether reduced developmental stability occurred prior to the epizootic in 1988 and possibly predicted the high mortality. As a measure of developmental stability the fractal dimension of the paired maxillo palatinae suture was calculated and the degree of fluctuating asymmetry in teeth, foramina and the paired suture was estimated in 361 skulls. Moreover prevalence of three pathological changes of the skull was investigated. Reduced developmental stability and higher prevalence of pathological changes were associated with a dramatic increase in pollution after World War II. Reduced developmental stability occurred prior to the epizootic, although young seals born after levels of pollution started to decrease tended to be developmentally more stable. No relationship was found between pathological changes and developmental stability.
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The giant bite of a new raptorial sperm whale from the Miocene epoch of Peru
Article
Full-text available
  • Jul 2010
The modern giant sperm whale Physeter macrocephalus, one of the largest known predators, preys upon cephalopods at great depths. Lacking a functional upper dentition, it relies on suction for catching its prey; in contrast, several smaller Miocene sperm whales (Physeteroidea) have been interpreted as raptorial (versus suction) feeders, analogous to the modern killer whale Orcinus orca. Whereas very large physeteroid teeth have been discovered in various Miocene localities, associated diagnostic cranial remains have not been found so far. Here we report the discovery of a new giant sperm whale from the Middle Miocene of Peru (approximately 12-13 million years ago), Leviathan melvillei, described on the basis of a skull with teeth and mandible. With a 3-m-long head, very large upper and lower teeth (maximum diameter and length of 12cm and greater than 36cm, respectively), robust jaws and a temporal fossa considerably larger than in Physeter, this stem physeteroid represents one of the largest raptorial predators and, to our knowledge, the biggest tetrapod bite ever found. The appearance of gigantic raptorial sperm whales in the fossil record coincides with a phase of diversification and size-range increase of the baleen-bearing mysticetes in the Miocene. We propose that Leviathan fed mostly on high-energy content medium-size baleen whales. As a top predator, together with the contemporaneous giant shark Carcharocles megalodon, it probably had a profound impact on the structuring of Miocene marine communities. The development of a vast supracranial basin in Leviathan, extending on the rostrum as in Physeter, might indicate the presence of an enlarged spermaceti organ in the former that is not associated with deep diving or obligatory suction feeding.
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Functional Morphology of the Sperm Whale ( Physeter macrocephalus ) Tongue, with Reference to Suction Feeding
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Full-text available
  • Dec 2004
Gross and microscopic examination of the tongue and hyolingual apparatus of the sperm whale (Physeter macrocephalus) revealed numerous distinct differences from those of other toothed whales and dolphins, largely reflecting the tongue's atypi-cal position, relations, and size, and its primary role in suction ingestion, rather than prey prehen-sion or transport, as in many other odontocetes. Unlike other odontocetes, the sperm whale has a short, wide tongue that is uniquely situated at the rear of the open oral cavity. Since the tongue does not extend to the tooth row, which runs along the elongated median mandibular symphysis, it cannot easily reorient grasped prey items, yet it can position them to be swallowed or sucked directly into the oropharyngeal opening. The scarcity of intrinsic lingual musculature (m. lingualis proprius), coupled with the relatively large paired extrinsic muscles inserting in the tongue—notably the m. hyoglossus, whose profuse fibers comprise much of the tongue root, and the m. genioglossus—suggests the tongue mainly undergoes positional, rather than shape, changes as it is retracted by the hyoid to generate negative intraoral pressures to capture and ingest prey items via suction. The tongue possesses numerous longitudinal folds or plicae, but almost no free tip; its slightly convex dorsum bears deep fissures and few sensory receptors in a multilayered and predominantly aglandular horny epithelium.
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Waipatia maerewhenua New Genus and New Species (Waipatiidae, New Family), An Archaic Late Oligocene Dolphin (Cetacea: Odontoceti: Platanistoidea) from New Zealand
Article
  • Jan 1994
Waipatia maerewhenua, from the Otekaike Limestone (late Oligocene), Waitaki Valley, New Zealand, is a new genus and species in a new family Waipatiidae (Odontoceti: Platanistoidea) near the base of the radiation of platanistoids. Its anatomical and morphological features are described. Waipatia maerewhenua is more closely related to the Squalodelphidae and Platanistidae than to the Squalodontidae. Of the similar small dolphins previously identified as Squalodontidae, Microcetus ambiguus (late Oligocene, Germany) and Sachalinocetus cholmicus (early or middle Miocene, Sakhalin) are possible waipatiids. These taxa reveal an early radiation of the Platanistoidea by the late Oligocene. -from Author
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Bite marks revisited – evidence for middle-to-late Eocene Basilosaurus isis predation on Dorudon atrox (both Cetacea, Basilosauridae)
Article
  • Jan 2012
Basilosauridae are cosmopolitan fully-aquatic archaeocete whales, represented by larger Basilosaurus isis and smaller Dorudon atrox in the middle-to-late Eocene Gehannam and Birket Qarun Formations of Egypt (ca. 38-36.5 Ma). Adult and juvenile Dorudon but only adult Basilosaurus are found in these shallow-marine deposits. Lethal bite marks on juvenile Dorudon skulls sparked the idea that adult Basilosaurus invaded calving grounds of D. atrox to prey on their young. However, there has been no direct evidence to support this idea. In this study, bite marks on specimens of juvenile D. atrox that have previously been described but not assigned to a particular trace-maker are reinvestigated, and additional bone modifications are analyzed. Applying computed tomography (CT), digital surface scanning, and three-dimensional (3D) reconstruction, the juvenile D. atrox specimens were digitally placed into the mouth of an adult B. isis. Bite marks match the dentition of B. isis. Imprints of tooth casts of B. isis in modeling clay furthermore resemble bite marks on these D. atrox specimens in shape and size. B. isis was likely a predator that included juvenile D. atrox in its diet. Prey was predominantly captured from a lateral position across the head and sometimes adjusted in the mouth prior to a more powerful bite. Scavenging of B. isis on D. atrox calves is also possible. The diet of Basilosaurus and dietary differences within the genus resemble those known in modern killer whales (Orcinus orca). B. isis is the only archaeocete known to date that possibly preyed on other cetaceans.
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Prevalence and clinical characteristics of oral tori among outpatients in Northern Malaysia
Article
  • Apr 2012
Objectives The objectives of this study were to determine the prevalence and clinical characteristics of torus palatinus (TP) and torus mandibularis (TM) in Malaysian dental patients.Methods Thousand five hundred and thirty-two dental patients were examined for the presence of oral tori at the Faculty of Dentistry outpatient clinic, AIMST University. Factors such as race, age, sex, size, and shape of tori were studied.ResultsThe prevalence rates were 12% for TP and 2.8% for TM. A variation in the presence of tori among the three races in Malaysia–Chinese, Malays, and Indians–was noted, where the Chinese significantly had a higher prevalence of TP (17.9%) and TM (4.6%). Predominantly, tori were observed >40 years and older age group, and further both TP and TM were seen more commonly in women. Most TP were of smooth type (52.2%) and >2 cm (67.4%), while all TM were bilateral and nodular, plus most were <2 cm (67.4%).Conclusion Presence of tori (TP and TM) was detected in 12.5% of the participants. The variations noted in the prevalence and clinical characteristics of tori among people of different races living in the same country reflect its multifactorial etiology. Both genetic and environmental factors are responsible for its occurrence, and particular races are more prone genetically where its expression is enhanced by environmental factors.
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