Background: Odontocetes (toothed whales) are the most species-rich marine mammal lineage. The cat... more Background: Odontocetes (toothed whales) are the most species-rich marine mammal lineage. The catalyst for their evolutionary success is echolocation-a form of biological sonar that uses high-frequency sound, produced in the forehead and ultimately detected by the cochlea. The ubiquity of echolocation in odontocetes across a wide range of physical and acoustic environments suggests that convergent evolution of cochlear shape is likely to have occurred. To test this, we used SURFACE; a method that fits Ornstein-Uhlenbeck (OU) models with stepwise AIC (Akaike Information Criterion) to identify convergent regimes on the odontocete phylogeny, and then tested whether convergence in these regimes was significantly greater than expected by chance. Results: We identified three convergent regimes: (1) True's (Mesoplodon mirus) and Cuvier's (Ziphius cavirostris) beaked whales; (2) sperm whales (Physeter macrocephalus) and all other beaked whales sampled; and (3) pygmy (Kogia breviceps) and dwarf (Kogia sima) sperm whales and Dall's porpoise (Phocoenoides dalli). Interestingly the 'river dolphins', a group notorious for their convergent morphologies and riverine ecologies, do not have convergent cochlear shapes. The first two regimes were significantly convergent, with habitat type and dive type significantly correlated with membership of the sperm whale + beaked whale regime. Conclusions: The extreme acoustic environment of the deep ocean likely constrains cochlear shape, causing the cochlear morphology of sperm and beaked whales to converge. This study adds support for cochlear morphology being used to predict the ecology of extinct cetaceans.
The Huayquerías Formation (Late Miocene, Huayquerian SALMA) is broadly exposed in westcentral Arg... more The Huayquerías Formation (Late Miocene, Huayquerian SALMA) is broadly exposed in westcentral Argentina (Mendoza). The target of several major paleontological expeditions in the first half of the 20th century, the Mendozan Huayquerías (“badlands”) have recently yielded a significant number of new fossil finds. In this contribution we describe a complete skull (IANIGLA-PV 29) and place it systematically as Huayqueriana cf. H. cristata (Rovereto, 1914) (Litopterna, Macraucheniidae). The specimen shares some nonexclusive features with H. cristata (similar size, rostral border of the orbit almost level with distal border of M3, convergence of maxillary bones at the level of the P3/P4 embrasure, flat snout, very protruding orbits, round outline of premaxillary area in palatal view, and small diastemata between I3/C and C/P1). Other differences (e.g., lack of sagittal crest) may or may not represent intraspecific variation. In addition to other features described here, endocast reconstruction utilizing computer tomography (CT) revealed the presence of a derived position of the orbitotemporal canal running below the rhinal fissure along the lateroventral aspect of the piriform lobe. CT scanning also established that the maxillary nerve (CN V2) leaves the skull through the sphenoorbital fissure, as in all other litopterns, a point previously contested for macraucheniids. The angle between the lateral semicircular canal and the plane of the base of the skull is about 26°, indicating that in life the head was oriented much as in modern horses. Depending on the variables used, estimates of the body mass of IANIGLA-PV 29 produced somewhat conflicting results. Our preferred body mass estimate is 250 kg, based on the centroid size of 36 3D cranial landmarks and accompanying low prediction error. The advanced degree of tooth wear in IANIGLA-PV 29 implies that the individual died well into old age. However, a count of cementum lines on the sectioned left M2 is consistent with an age at death of 10 or 11 years, younger than expected given its body mass. This suggests that the animal had a very abrasive diet. Phylogenetic analysis failed to resolve the position of IANIGLA-PV 29 satisfactorily, a result possibly influenced by intraspecific variation. There is no decisive evidence for the proposition that Huayqueriana, or any other litoptern, were foregut fermenters.
Mammalian molluscivores feed mainly by shell-crushing or suction-feeding. The extinct marine arct... more Mammalian molluscivores feed mainly by shell-crushing or suction-feeding. The extinct marine arctoid, Kolponomos, has been interpreted as an otter-like shell-crusher based on similar dentitions. However, neither the masticatory biomechanics of the shell-crushing adaptation nor the way Kolponomos may have captured hard-shelled prey have been tested. Based on mandibular symphyseal morphology shared by Kolponomos and sabre-toothed carnivores, we hypothesize a sabretooth-like mechanism for Kolponomos prey-capture, whereby the mandible functioned as an anchor. Torque generated from jaw closure and head flexion was used to dislodge prey by prying, with prey then crushed using cheek teeth. We test this hypothesized feeding sequence using phylogenetically informed biomechanical simulations and shape analyses, and find a strongly supported, shared high mandibular stiffness in simulated prey-capture bites and mandibular shape in Kolponomos and the sabre-toothed cat Smilodon. These two distantly related taxa converged on using mandibles to anchor cranial torqueing forces when prying substrate-bound prey in the former and sabre-driving forces during prey-killing in the latter. Simulated prey-crushing bites indicate that Kolponomos and sea otters exhibit alternative structural stiffness-bite efficiency combinations in mandibular biomechanical adaptation for shell-crushing. This unique feeding system of Kolponomos exemplifies a mosaic of form-function convergence relative to other Carnivora.
The bony labyrinth provides a proxy for the morphology of the inner ear, a primary cognitive orga... more The bony labyrinth provides a proxy for the morphology of the inner ear, a primary cognitive organ involved in hearing, body perception in space, and balance in vertebrates. Bony labyrinth shape variations often are attributed to phylogenetic and ecological factors. Here we use three-dimensional (3D) geometric morphometrics to examine the phylogenetic and ecological patterns of variation in the bony labyrinth morphology of the most species-rich and ecologically diversified traditionally recognized superfamily of Carnivora, the Musteloidea (e.g. weasels, otters, badgers, red panda, skunks, raccoons, coatis). We scanned the basicrania of specimens belonging to 31 species using high-resolution X-ray computed micro-tomography (μCT) to virtually reconstruct 3D models of the bony labyrinths. Labyrinth morphology is captured by a set of six fixed landmarks on the vestibular and cochlear systems, and 120 sliding semilandmarks, slid at the center of the semicircular canals and the cochlea. We found that the morphology of this sensory structure is not significantly influenced by bony labyrinth size, in comparisons across all musteloids or in any of the individual traditionally recognized families (Mephitidae, Procyonidae, Mustelidae). PCA (principal components analysis) of shape data revealed that bony labyrinth morphology is clearly distinguishable between musteloid families, and permutation tests of the Kmult statistic confirmed that the bony labyrinth shows a phylogenetic signal in musteloids and in most mustelids. Both the vestibular and cochlear regions display morphological differences among the musteloids sampled, associated with the size and curvature of the semicircular canals, angles between canals, presence or absence of a secondary common crus, degree of lateral compression of the vestibule, orientation of the cochlea relative to the semicircular canals, proportions of the cochlea, and degree of curvature of its turns. We detected a significant ecological signal in the bony labyrinth shape of musteloids, differentiating semi-aquatic taxa from non-aquatic ones (the taxa assigned to terrestrial, arboreal, semi-arboreal, and semi-fossorial categories), and a significant signal for mustelids, differentiating the bony labyrinths of terrestrial, semi-arboreal, arboreal, semi-fossorial and semi-aquatic species from each other. Otters and minks are distinguished from non-aquatic musteloids by an oval rather than circular anterior canal, sinuous rather than straight lateral canal, and acute rather than straight angle between the posterior and lateral semicircular canals – each of these morphological characters has been related previously to animal sensitivity for detecting head motion in space.
We report new dental remains of Mustelidae
from the late middle Miocene of Mae Moh Basin, norther... more We report new dental remains of Mustelidae from the late middle Miocene of Mae Moh Basin, northern Thailand, improving the poor fossil record of the family in Southeast Asia. Siamogale thailandica is a poorly known mustelid, previously recorded from just a single tooth. Here we present over a hundred new specimens attributable to this species. S. thailandica shows a combination of primitive and convergent features of the dentition that makes its original subfamilial assignment to Lutrinae doubtful. Evidence from the dental morphology suggests that it belongs to a bunodont otter-like mustelid that evolved in convergence with “true” otters (Lutrinae) toward a semiaquatic way of life. Autapomorphic features such as the height and the position of the m1 metaconid and the shape of the P4 lingual shelf make S. thailandica unique among Mustelidae. The morphology of this species is mostly similar to Mionictis species and Lartetictis dubia, reported in the Miocene of North America and Europe, respectively. These similarities could imply immigration events to Thailand in the early or middle Miocene. Alternately, the lineage leading to Siamogale might have deeper origins from an endemic early Miocene Southeast Asian mustelid.
Qiang Li, Guangpu Xie, Gary T. Takeuchi, Tao Deng, Zhijie J. Tseng, Camille Grohé, Xiaoming Wang, Oct 2014
The Kunlun Pass Basin, at the foothill of Yuzhu Mountain (6224 m asl and the highest peak of the ... more The Kunlun Pass Basin, at the foothill of Yuzhu Mountain (6224 m asl and the highest peak of the Kunlun Range), records Plio-Pleistocene fine-grained sediments sandwiched between glacial moraines. We document a new vertebrate fossil assemblage, the Yuzhu Fauna, with 16 mammal and 2 fish species that provide insights into basin chronology as well as the paleoenvironment adjacent to alpine glaciations in the Pliocene, in which the mammals and fishes lived. The Yuzhu Fauna consists of the following eight small mammals: Petenyia sp., Aepyosciurus sp., Nannocricetus mongolicus, cf. Orientalomys sinensis, Mimomys n. sp., Prosiphneus cf. P. eriksoni, Ochotona minor, Ochotona cf. O. lagreli, and eight large mammals: Rhinocerotidae indet., Hipparion (Proboscidipparion) pater, Qurliqnoria sp., Bovidae indet., cf. Panthera blytheae, Hyaeninae indet., Vulpes qiuzhudingi, and aff. Arctomeles sp. Two cyprinid fishes are also included: Gymnocypris sp. and Triplophysa sp. The Yuzhu Fauna has a distinctly early–middle Pliocene appearance, substantially earlier than previous age estimates, sharing broad similarities with vertebrate fossil assemblages from North China in general and the Zanda Fauna in southern Tibet in particular, including three carnivorans (Vulpes qiuzhudingi, cf. Panthera blytheae, and aff. Arctomeles sp.), one artiodactyl (Qurliqnoria), and at least two rodents (Aepyosciurus and Prosiphneus) and a lagomorph (Ochotona). We re-interpret published magnetostratigraphy to arrive at a correlation of the Yuzhu Fauna to the lower part of Chron 2Ar (Gilbert Chron 4.2–3.6 Ma), and the entire basin sequence spanning part of chrons 1n through 3n.3n, i.e., ~ 4.9–0.5 Ma. Our revised magnetic age for the Kunlun Pass Basin strata implies a slip rate of 7.2–6.1 mm/year along this part of the Kunlun Pass strike-slip fault system, much slower than its modern rate of off set.
Background: Odontocetes (toothed whales) are the most species-rich marine mammal lineage. The cat... more Background: Odontocetes (toothed whales) are the most species-rich marine mammal lineage. The catalyst for their evolutionary success is echolocation-a form of biological sonar that uses high-frequency sound, produced in the forehead and ultimately detected by the cochlea. The ubiquity of echolocation in odontocetes across a wide range of physical and acoustic environments suggests that convergent evolution of cochlear shape is likely to have occurred. To test this, we used SURFACE; a method that fits Ornstein-Uhlenbeck (OU) models with stepwise AIC (Akaike Information Criterion) to identify convergent regimes on the odontocete phylogeny, and then tested whether convergence in these regimes was significantly greater than expected by chance. Results: We identified three convergent regimes: (1) True's (Mesoplodon mirus) and Cuvier's (Ziphius cavirostris) beaked whales; (2) sperm whales (Physeter macrocephalus) and all other beaked whales sampled; and (3) pygmy (Kogia breviceps) and dwarf (Kogia sima) sperm whales and Dall's porpoise (Phocoenoides dalli). Interestingly the 'river dolphins', a group notorious for their convergent morphologies and riverine ecologies, do not have convergent cochlear shapes. The first two regimes were significantly convergent, with habitat type and dive type significantly correlated with membership of the sperm whale + beaked whale regime. Conclusions: The extreme acoustic environment of the deep ocean likely constrains cochlear shape, causing the cochlear morphology of sperm and beaked whales to converge. This study adds support for cochlear morphology being used to predict the ecology of extinct cetaceans.
The Huayquerías Formation (Late Miocene, Huayquerian SALMA) is broadly exposed in westcentral Arg... more The Huayquerías Formation (Late Miocene, Huayquerian SALMA) is broadly exposed in westcentral Argentina (Mendoza). The target of several major paleontological expeditions in the first half of the 20th century, the Mendozan Huayquerías (“badlands”) have recently yielded a significant number of new fossil finds. In this contribution we describe a complete skull (IANIGLA-PV 29) and place it systematically as Huayqueriana cf. H. cristata (Rovereto, 1914) (Litopterna, Macraucheniidae). The specimen shares some nonexclusive features with H. cristata (similar size, rostral border of the orbit almost level with distal border of M3, convergence of maxillary bones at the level of the P3/P4 embrasure, flat snout, very protruding orbits, round outline of premaxillary area in palatal view, and small diastemata between I3/C and C/P1). Other differences (e.g., lack of sagittal crest) may or may not represent intraspecific variation. In addition to other features described here, endocast reconstruction utilizing computer tomography (CT) revealed the presence of a derived position of the orbitotemporal canal running below the rhinal fissure along the lateroventral aspect of the piriform lobe. CT scanning also established that the maxillary nerve (CN V2) leaves the skull through the sphenoorbital fissure, as in all other litopterns, a point previously contested for macraucheniids. The angle between the lateral semicircular canal and the plane of the base of the skull is about 26°, indicating that in life the head was oriented much as in modern horses. Depending on the variables used, estimates of the body mass of IANIGLA-PV 29 produced somewhat conflicting results. Our preferred body mass estimate is 250 kg, based on the centroid size of 36 3D cranial landmarks and accompanying low prediction error. The advanced degree of tooth wear in IANIGLA-PV 29 implies that the individual died well into old age. However, a count of cementum lines on the sectioned left M2 is consistent with an age at death of 10 or 11 years, younger than expected given its body mass. This suggests that the animal had a very abrasive diet. Phylogenetic analysis failed to resolve the position of IANIGLA-PV 29 satisfactorily, a result possibly influenced by intraspecific variation. There is no decisive evidence for the proposition that Huayqueriana, or any other litoptern, were foregut fermenters.
Mammalian molluscivores feed mainly by shell-crushing or suction-feeding. The extinct marine arct... more Mammalian molluscivores feed mainly by shell-crushing or suction-feeding. The extinct marine arctoid, Kolponomos, has been interpreted as an otter-like shell-crusher based on similar dentitions. However, neither the masticatory biomechanics of the shell-crushing adaptation nor the way Kolponomos may have captured hard-shelled prey have been tested. Based on mandibular symphyseal morphology shared by Kolponomos and sabre-toothed carnivores, we hypothesize a sabretooth-like mechanism for Kolponomos prey-capture, whereby the mandible functioned as an anchor. Torque generated from jaw closure and head flexion was used to dislodge prey by prying, with prey then crushed using cheek teeth. We test this hypothesized feeding sequence using phylogenetically informed biomechanical simulations and shape analyses, and find a strongly supported, shared high mandibular stiffness in simulated prey-capture bites and mandibular shape in Kolponomos and the sabre-toothed cat Smilodon. These two distantly related taxa converged on using mandibles to anchor cranial torqueing forces when prying substrate-bound prey in the former and sabre-driving forces during prey-killing in the latter. Simulated prey-crushing bites indicate that Kolponomos and sea otters exhibit alternative structural stiffness-bite efficiency combinations in mandibular biomechanical adaptation for shell-crushing. This unique feeding system of Kolponomos exemplifies a mosaic of form-function convergence relative to other Carnivora.
The bony labyrinth provides a proxy for the morphology of the inner ear, a primary cognitive orga... more The bony labyrinth provides a proxy for the morphology of the inner ear, a primary cognitive organ involved in hearing, body perception in space, and balance in vertebrates. Bony labyrinth shape variations often are attributed to phylogenetic and ecological factors. Here we use three-dimensional (3D) geometric morphometrics to examine the phylogenetic and ecological patterns of variation in the bony labyrinth morphology of the most species-rich and ecologically diversified traditionally recognized superfamily of Carnivora, the Musteloidea (e.g. weasels, otters, badgers, red panda, skunks, raccoons, coatis). We scanned the basicrania of specimens belonging to 31 species using high-resolution X-ray computed micro-tomography (μCT) to virtually reconstruct 3D models of the bony labyrinths. Labyrinth morphology is captured by a set of six fixed landmarks on the vestibular and cochlear systems, and 120 sliding semilandmarks, slid at the center of the semicircular canals and the cochlea. We found that the morphology of this sensory structure is not significantly influenced by bony labyrinth size, in comparisons across all musteloids or in any of the individual traditionally recognized families (Mephitidae, Procyonidae, Mustelidae). PCA (principal components analysis) of shape data revealed that bony labyrinth morphology is clearly distinguishable between musteloid families, and permutation tests of the Kmult statistic confirmed that the bony labyrinth shows a phylogenetic signal in musteloids and in most mustelids. Both the vestibular and cochlear regions display morphological differences among the musteloids sampled, associated with the size and curvature of the semicircular canals, angles between canals, presence or absence of a secondary common crus, degree of lateral compression of the vestibule, orientation of the cochlea relative to the semicircular canals, proportions of the cochlea, and degree of curvature of its turns. We detected a significant ecological signal in the bony labyrinth shape of musteloids, differentiating semi-aquatic taxa from non-aquatic ones (the taxa assigned to terrestrial, arboreal, semi-arboreal, and semi-fossorial categories), and a significant signal for mustelids, differentiating the bony labyrinths of terrestrial, semi-arboreal, arboreal, semi-fossorial and semi-aquatic species from each other. Otters and minks are distinguished from non-aquatic musteloids by an oval rather than circular anterior canal, sinuous rather than straight lateral canal, and acute rather than straight angle between the posterior and lateral semicircular canals – each of these morphological characters has been related previously to animal sensitivity for detecting head motion in space.
We report new dental remains of Mustelidae
from the late middle Miocene of Mae Moh Basin, norther... more We report new dental remains of Mustelidae from the late middle Miocene of Mae Moh Basin, northern Thailand, improving the poor fossil record of the family in Southeast Asia. Siamogale thailandica is a poorly known mustelid, previously recorded from just a single tooth. Here we present over a hundred new specimens attributable to this species. S. thailandica shows a combination of primitive and convergent features of the dentition that makes its original subfamilial assignment to Lutrinae doubtful. Evidence from the dental morphology suggests that it belongs to a bunodont otter-like mustelid that evolved in convergence with “true” otters (Lutrinae) toward a semiaquatic way of life. Autapomorphic features such as the height and the position of the m1 metaconid and the shape of the P4 lingual shelf make S. thailandica unique among Mustelidae. The morphology of this species is mostly similar to Mionictis species and Lartetictis dubia, reported in the Miocene of North America and Europe, respectively. These similarities could imply immigration events to Thailand in the early or middle Miocene. Alternately, the lineage leading to Siamogale might have deeper origins from an endemic early Miocene Southeast Asian mustelid.
Qiang Li, Guangpu Xie, Gary T. Takeuchi, Tao Deng, Zhijie J. Tseng, Camille Grohé, Xiaoming Wang, Oct 2014
The Kunlun Pass Basin, at the foothill of Yuzhu Mountain (6224 m asl and the highest peak of the ... more The Kunlun Pass Basin, at the foothill of Yuzhu Mountain (6224 m asl and the highest peak of the Kunlun Range), records Plio-Pleistocene fine-grained sediments sandwiched between glacial moraines. We document a new vertebrate fossil assemblage, the Yuzhu Fauna, with 16 mammal and 2 fish species that provide insights into basin chronology as well as the paleoenvironment adjacent to alpine glaciations in the Pliocene, in which the mammals and fishes lived. The Yuzhu Fauna consists of the following eight small mammals: Petenyia sp., Aepyosciurus sp., Nannocricetus mongolicus, cf. Orientalomys sinensis, Mimomys n. sp., Prosiphneus cf. P. eriksoni, Ochotona minor, Ochotona cf. O. lagreli, and eight large mammals: Rhinocerotidae indet., Hipparion (Proboscidipparion) pater, Qurliqnoria sp., Bovidae indet., cf. Panthera blytheae, Hyaeninae indet., Vulpes qiuzhudingi, and aff. Arctomeles sp. Two cyprinid fishes are also included: Gymnocypris sp. and Triplophysa sp. The Yuzhu Fauna has a distinctly early–middle Pliocene appearance, substantially earlier than previous age estimates, sharing broad similarities with vertebrate fossil assemblages from North China in general and the Zanda Fauna in southern Tibet in particular, including three carnivorans (Vulpes qiuzhudingi, cf. Panthera blytheae, and aff. Arctomeles sp.), one artiodactyl (Qurliqnoria), and at least two rodents (Aepyosciurus and Prosiphneus) and a lagomorph (Ochotona). We re-interpret published magnetostratigraphy to arrive at a correlation of the Yuzhu Fauna to the lower part of Chron 2Ar (Gilbert Chron 4.2–3.6 Ma), and the entire basin sequence spanning part of chrons 1n through 3n.3n, i.e., ~ 4.9–0.5 Ma. Our revised magnetic age for the Kunlun Pass Basin strata implies a slip rate of 7.2–6.1 mm/year along this part of the Kunlun Pass strike-slip fault system, much slower than its modern rate of off set.
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Papers by Camille Grohé
from the late middle Miocene of Mae Moh Basin, northern
Thailand, improving the poor fossil record of the family in
Southeast Asia. Siamogale thailandica is a poorly known
mustelid, previously recorded from just a single tooth. Here
we present over a hundred new specimens attributable to
this species. S. thailandica shows a combination of
primitive and convergent features of the dentition that
makes its original subfamilial assignment to Lutrinae
doubtful. Evidence from the dental morphology suggests
that it belongs to a bunodont otter-like mustelid that evolved
in convergence with “true” otters (Lutrinae) toward a semiaquatic
way of life. Autapomorphic features such as the
height and the position of the m1 metaconid and the shape of
the P4 lingual shelf make S. thailandica unique among
Mustelidae. The morphology of this species is mostly similar
to Mionictis species and Lartetictis dubia, reported in the
Miocene of North America and Europe, respectively. These
similarities could imply immigration events to Thailand in
the early or middle Miocene. Alternately, the lineage leading
to Siamogale might have deeper origins from an endemic
early Miocene Southeast Asian mustelid.
from the late middle Miocene of Mae Moh Basin, northern
Thailand, improving the poor fossil record of the family in
Southeast Asia. Siamogale thailandica is a poorly known
mustelid, previously recorded from just a single tooth. Here
we present over a hundred new specimens attributable to
this species. S. thailandica shows a combination of
primitive and convergent features of the dentition that
makes its original subfamilial assignment to Lutrinae
doubtful. Evidence from the dental morphology suggests
that it belongs to a bunodont otter-like mustelid that evolved
in convergence with “true” otters (Lutrinae) toward a semiaquatic
way of life. Autapomorphic features such as the
height and the position of the m1 metaconid and the shape of
the P4 lingual shelf make S. thailandica unique among
Mustelidae. The morphology of this species is mostly similar
to Mionictis species and Lartetictis dubia, reported in the
Miocene of North America and Europe, respectively. These
similarities could imply immigration events to Thailand in
the early or middle Miocene. Alternately, the lineage leading
to Siamogale might have deeper origins from an endemic
early Miocene Southeast Asian mustelid.