Numerical anomalies in the dentition of southern fur seals and sea lions (Pinnipedia: Otariidae)

Loch, Carolina; Simões‐Lopes, Paulo C.; Drehmer, César Jaeger

doi:10.1590/s1984-46702010005000001

Cited by 14 publications

(12 citation statements)

References 12 publications

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“…Missing teeth due to possible trauma or pathological losses were not included in this analysis. Following Drehmer et al (2004), Abbott and Verstraete (2005) and Loch et al (2010), supernumerary and congenitally missing teeth were identified on the basis of absent or multiple alveolar sockets. Congenitally missing teeth were defined by taking into consideration the absence of the tooth and alveolus, as well as morphologically normal bone (smooth aspect) present at the site.…”

Section: Methodsmentioning

confidence: 99%

“…For this group, agenesis of the last postcanines is often observed in museum specimens, commonly the upper PC/5 or 6 (Hamilton 1934;Drehmer et al 2004;Loch et al 2010). This observation is consistent with the findings of this study, where 60 % (n = 6) of the specimens diagnosed with agenesis corresponded to congenital losses of the most posterior postcanines.…”

Section: Agenesis Of Teethmentioning

confidence: 99%

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Dental anomalies in pinnipeds (Carnivora: Otariidae and Phocidae): occurrence and evolutionary implications

2015

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Dental anomalies comprise variations in number, shape, size, position and occlusion of teeth, mainly caused by genetic mechanisms. This study aimed to investigate the nature and prevalence of dental anomalies in a large sample of pinnipeds (Otariidae and Phocidae) and to discuss potential evolutionary and ecological implications. Thirty-four species in twenty genera were sampled. The dentition of the specimens examined was compared with the normal dental formula for the species, and supernumerary and congenitally missing teeth were identified and recorded. Agenesis was observed in 0.93 % of the specimens analyzed (n = 10), being more frequent in otariids. The posteriormost upper postcanines were the teeth absent most frequently. Supernumerary teeth were observed in 1.8 % of the specimens (n = 19), more commonly in phocids. Supernumerary teeth can be interpreted as either atavistic manifestations (particularly for the posteriormost postcanines in Otariidae) or cases of disturbances in dental morphogenesis leading to the formation of extra teeth when they occur in other positions of the tooth row. Morphological dental variants such as ectopic and geminated teeth were also recorded. Cases of dental anomalies should have a limited effect on the functional morphology of the feeding apparatus in pinnipeds, with little influence on the fitness and performance of the animals. Nevertheless, understanding patterns of dental variation should contribute to future studies aiming to elucidate aspects of dental evolution and the phylogenetic relationships of pinnipeds.

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Section: Methodsmentioning

confidence: 99%

Section: Agenesis Of Teethmentioning

confidence: 99%

Dental anomalies in pinnipeds (Carnivora: Otariidae and Phocidae): occurrence and evolutionary implications

2015

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“…Here the moment arm is approximated by jaw length since this is the maximum effective distance from the force to the fulcrum (Biknevicius and Ruff, ; Therrien, ). Peak loads are assumed to be more important than cyclical loads in these taxa because mastication is related to cyclical loadings and is absent in these taxa (Hylander, ; Hylander and Johnson, ; Miller et al, ; Loch et al, ). While section moduli were calculated in both dorsoventral and labiolingual planes, we report here only dorsoventral section moduli, as they are likely to be the most important in terms of estimating bite force (Biknevicius and Ruff, ; Therrien, ), and because there was little variation in cross‐sectional shape of the corpus between the species (Supporting Information Fig.…”

Section: Methodsmentioning

confidence: 99%

Morphology and Biomechanics of the Pinniped Jaw: Mandibular Evolution Without Mastication

Jones

Ruff

Goswami

2013

The Anatomical Record

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Pinnipeds (seals, sea lions, and walruses) underwent a shift in jaw function away from typical carnivoran mastication to more novel marine behaviors during the terrestrial-aquatic transition. Here we test the effect of aquatic prey capture and male-male combat on the morphological evolution of a mammal jaw that does not masticate. Nine three-dimensional landmarks were taken along the mandible for 25 species (N 5 83), and corpus and symphysis external and cortical breadths for a subset of five species (N 5 33). Principal components analysis was performed on size-corrected landmark data to assess variation in overall jaw morphology across pinnipeds. Corpus breadths were input to a beam model to calculate strength properties and estimated bite force of specific species with contrasting behaviors (filter feeding, suction feeding, grip-and-tear feeding, and malemale combat). Results indicate that, although phylogenetic signal in jaw shape is strong, function is also important in determining morphology. Filter feeders display an elongate symphysis and a long toothrow that may play a role in filtering krill. Grip-and-tear feeders have a long jaw and large estimated bite force relative to non-biting species. However, the largest estimated bite forces were observed in males of male-male combative species, likely due to the high selection pressure associated with male success in highly polygynous species. The suction feeding jaw is weak in biting but has a different morphology in the two suction feeding taxa. In conclusion, familial patterns of pinniped jaw shape due to phylogenetic relatedness have been modified by adaptations to specialized behavior of individual taxa.

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“…The high incidence of dental variation in otariids (relative to terrestrial carnivorans) indicates that dental anomalies probably do not adversely affect feeding ability (Drehmer et al, 2004;Loch et al, 2010). Indeed, phocid seals have been shown to exhibit greater dental variation relative to terrestrial carnivores, probably related to the non-occluding nature of pinniped dentitions relative to the integrated dentition of terrestrial carnivorans (Miller et al, 2007), a functional constraint from which pinnipeds have been released.…”

Section: Dental Evolutionmentioning

confidence: 99%

New records of the fur seal Callorhinus (Carnivora: Otariidae) from the Plio-Pleistocene Rio Dell Formation of Northern California and comments on otariid dental evolution

Boessenecker¹

2018

Preprint

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New fossils representing two species of the fur seal Callorhinus are reported from the uppermost Pliocene to lower Pleistocene Rio Dell Formation of northern California. The finds include latest Pliocene–earliest Pleistocene dentaries and postcrania of Callorhinus gilmorei, and a partial dentary of early Pleistocene age identified as Callorhinus sp. The aforementioned material is ascribed to C. gilmorei due to the incipient single-rooted condition of the p1–2, retention of double-rooted p3–m1, and overall small size. The dentary identified as Callorhinus sp. exhibits a more derived pattern of tooth morphology, including single-rooted p1–p4 (and double-rooted m1), larger size than C. gilmorei, and in the size range of extant Callorhinus ursinus (which typically exhibit fused roots on all postcanine teeth). Fusion of postcanine roots began with the p2 and continued posteriorly, and is likely an adaptation to accommodate crowded teeth anteriorly in the jaws. Callorhinus gilmorei has previously been reported from the upper Pliocene of southern California and Japan, and this new record extends the range of this taxon further north in the Northeast Pacific. Callorhinus sp. is the most complete pinniped fossil to be described from the early Pleistocene of the Northeast Pacific. The wide biogeographic range of Callorhinus during the Pliocene and Pleistocene documents the persistence of this taxon, potentially as a Pliocene-Holocene anagenetic lineage. This highlights the antiquity of the Callorhinus lineage, which has persisted in the Northeast Pacific since the Pliocene, establishing it as the oldest and earliest diverging crown otariid.

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Numerical anomalies in the dentition of southern fur seals and sea lions (Pinnipedia: Otariidae)

Cited by 14 publications

References 12 publications

Dental anomalies in pinnipeds (Carnivora: Otariidae and Phocidae): occurrence and evolutionary implications

Dental anomalies in pinnipeds (Carnivora: Otariidae and Phocidae): occurrence and evolutionary implications

Morphology and Biomechanics of the Pinniped Jaw: Mandibular Evolution Without Mastication

New records of the fur seal Callorhinus (Carnivora: Otariidae) from the Plio-Pleistocene Rio Dell Formation of Northern California and comments on otariid dental evolution

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