108 research outputs found
Reappraisal of the extinct seal 'Phoca' vitulinoides from the Neogene of the North Sea Basin, with bearing on its geological age, phylogenetic affinities, and locomotion
Background: Discovered on the southern margin of the North Sea Basin, "Phoca" vitulinoides represents one of the best-known extinct species of Phocidae. However, little attention has been given to the species ever since its original 19th century description. Newly discovered material, including the most complete specimen of fossil Phocidae from the North Sea Basin, prompted the redescription of the species. Also, the type material of "Phoca" vitulinoides is lost.
Methods: "Phoca" vitulinoides is redescribed. Its phylogenetic position among Phocinae is assessed through phylogenetic analysis. Dinoflagellate cyst biostratigraphy is used to determine and reassess the geological age of the species. Myological descriptions of extant taxa are used to infer muscle attachments, and basic comparative anatomy of the gross morphology and biomechanics are applied to reconstruct locomotion.
Results: Detailed redescription of "Phoca" vitulinoides indicates relatively little affinities with the genus Phoca, but rather asks for the establishment of a new genus: Nanophoca gen. nov. Hence, "Phoca" vitulinoides is recombined into Nanophoca vitulinoides. This reassignment is confirmed by the phylogenetic analysis, grouping the genus Nanophoca and other extinct phocine taxa as stem phocines. Biostratigraphy and lithostratigraphy expand the known stratigraphic range of N. vitulinoides from the late Langhian to the late Serravallian. The osteological anatomy of N. vitulinoides indicates a relatively strong development of muscles used for fore flipper propulsion and increased flexibility for the hind flipper.
Discussion: The extended stratigraphic range of N. vitulinoides into the middle Miocene confirms relatively early diversification of Phocinae in the North Atlantic. Morphological features on the fore-and hindlimb of the species point toward an increased use of the fore flipper and greater flexibility of the hind flipper as compared to extant Phocinae, clearly indicating less derived locomotor strategies in this Miocene phocine species. Estimations of the overall body size indicate that N. vitulinoides is much smaller than Pusa, the smallest extant genus of Phocinae (and Phocidae), and than most extinct phocines
Integrative Approach Uncovers New Patterns of Ecomorphological Convergence in Slow Arboreal Xenarthrans
Identifying ecomorphological convergence examples is a central focus in evolutionary biology. In xenarthrans, slow arboreality independently arose at least three times, in the two genera of âtree slothsâ, Bradypus and Choloepus, and the silky anteater, Cyclopes. This specialized locomotor ecology is expectedly reflected by distinctive morpho-functional convergences. Cyclopes, although sharing several ecological features with âtree slothsâ, do not fully mirror the latter in their outstandingly similar suspensory slow arboreal locomotion. We hypothesized that the morphology of Cyclopes is closer to âtree slothsâ than to anteaters, but yet distinct, entailing that slow arboreal xenarthrans evolved through âincompleteâ convergence. In a multivariate trait space, slow arboreal xenarthrans are hence expected to depart from their sister taxa evolving toward the same area, but not showing extensive phenotypical overlap, due to the distinct position of Cyclopes. Conversely, a pattern of âcompleteâ convergence (i.e., widely overlapping morphologies) is hypothesized for âtree slothsâ. Through phylogenetic comparative methods, we quantified humeral and femoral convergence in slow arboreal xenarthrans, including a sample of extant and extinct non-slow arboreal xenarthrans. Through 3D geometric morphometrics, cross-sectional properties (CSP) and trabecular architecture, we integratively quantified external shape, diaphyseal anatomy and internal epiphyseal structure. Several traits converged in slow arboreal xenarthrans, especially those pertaining to CSP. Phylomorphospaces and quantitative convergence analyses substantiated the expected patterns of âincompleteâ and âcompleteâ convergence for slow arboreal xenarthrans and âtree slothsâ, respectively. This work, highlighting previously unidentified convergence patterns, emphasizes the value of an integrative multi-pronged quantitative approach to cope with complex mechanisms underlying ecomorphological convergence.Humboldt-UniversitĂ€t zu Berlin (1034)Peer Reviewe
A macroevolutionary common-garden experiment reveals differentially evolvable bone organization levels in slow arboreal mammals
The article processing charge was funded by the Open Access Publication Fund of Humboldt-UniversitÀt zu Berlin.Eco-morphological convergence, i.e., similar phenotypes evolved in ecologically convergent taxa, naturally reproduces a common-garden experiment since it allows researchers to keep ecological factors constant, studying intrinsic evolutionary drivers. The latter may result in differential evolvability that, among individual anatomical parts, causes mosaic evolution. Reconstructing the evolutionary morphology of the humerus and femur of slow arboreal mammals, we addressed mosaicism at different bone anatomical spatial scales. We compared convergence strength, using it as indicator of evolvability, between bone external shape and inner structure, with the former expected to be less evolvable and less involved in convergent evolution, due to anatomical constraints. We identify several convergent inner structural traits, while external shape only loosely follows this trend, and we find confirmation for our assumption in measures of convergence magnitude. We suggest that future macroevolutionary reconstructions based on bone morphology should include structural traits to better detect ecological effects on vertebrate diversification.Peer Reviewe
Unique bone microanatomy reveals ancestry of subterranean specializations in mammals
Acquiring a subterranean lifestyle entails a substantial shift for many aspects of terrestrial vertebratesâ biology. Although this lifestyle is associated with multiple instances of convergent evolution, the relative success of some subterranean lineages largely remains unexplained. Here, we focus on the mammalian transitions to life underground, quantifying bone microanatomy through high-resolution X-ray tomography. The true moles stand out in this dataset. Examination of this family's bone histology reveals that the highly fossorial moles acquired a unique phenotype involving large amounts of compacted coarse cancellous bone. This phenotype exceeds the adaptive optimum seemingly shared by several other subterranean mammals and can be traced back to some of the first known members of the family. This remarkable microanatomy was acquired early in the history of the group and evolved faster than the gross morphology innovations of true molesâ forelimb. This echoes the pattern described for other lifestyle transitions, such as the acquisition of bone mass specializations in secondarily aquatic tetrapods. Highly plastic traitsâsuch as those pertaining to bone structureâare hence involved in the early stages of different types of lifestyle transitions
The functional significance of aberrant cervical counts in sloths: insights from automated exhaustive analysis of cervical range of motion
Besides manatees, the suspensory extant âtree slothsâ are the only mammals that deviate from a cervical count (CC) of seven vertebrae. They do so in opposite directions in the two living genera (increased versus decreased CC). Aberrant CCs seemingly reflect neck mobility in both genera, suggesting adaptive significance for their head position during suspensory locomotion and especially increased ability for neck torsion in three-toed sloths. We test two hypotheses in a comparative evolutionary framework by assessing three-dimensional intervertebral range of motion (ROM) based on exhaustive automated detection of bone collisions and joint disarticulation while accounting for interacting rotations of roll, yaw and pitch. First, we hypothesize that the increase of CC also increases overall neck mobility compared with mammals with a regular CC, and vice versa. Second, we hypothesize that the anatomy of the intervertebral articulations determines mobility of the neck. The assessment revealed that CC plays only a secondary role in defining ROM since summed torsion (roll) capacity was primarily determined by vertebral anatomy. Our results thus suggest limited neck rotational adaptive significance of the CC aberration in sloths. Further, the study demonstrates the suitability of our automated approach for the comparative assessment of osteological ROM in vertebral series.Peer Reviewe
Pervasive cranial allometry at different anatomical scales and variational levels in extant armadillos
Allometry, i.e., morphological variation correlated with size, is a major pattern in organismal evolution. Since size varies both within and among species, allometry occurs at different variational levels. However, the variability of allometric patterns across levels is poorly known since its evaluation requires extensive comparative studies. Here, we implemented a 3D geometric morphometric approach to investigate cranial allometry at three main variational levelsâstatic, ontogenetic, and evolutionaryâand two anatomical scalesâentire cranium and cranial subunitsâbased on a dense intra- and interspecific sampling of extant armadillo diversity. While allometric trajectories differ among distantly related species, they hardly do so among sister families. This suggests that phylogenetic distance plays an important role in explaining allometric divergences. Beyond trajectories, our analyses revealed pervasive allometric shape changes shared across variational levels and anatomical scales. At the entire cranial scale, craniofacial allometry (relative snout elongation and braincase reduction) is accompanied notably by variations of nuchal crests and postorbital constriction. Among cranial subunits, the distribution of allometry was highly heterogeneous, with the frontal and petrosal bones showing the most pervasive shape changes, some of which were undetected at a more global scale. Evidence of widespread and superimposed allometric variations raises questions on their determinants and anatomical correlates and demonstrates the critical role of allometry in morphological evolution
Exceptional skull of huayqueriana (mammalia, litopterna, macraucheniidae) from the late miocene of Argentina: Anatomy, systematics, and peleobiological implications
The HuayquerĂas 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 HuayquerĂas (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.Fil: Forasiepi, Analia Marta. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Mendoza. Instituto Argentino de NivologĂa, GlaciologĂa y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de NivologĂa, GlaciologĂa y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de NivologĂa, GlaciologĂa y Ciencias Ambientales; ArgentinaFil: MacPhee, Ross D. E.. American Museum Of Natural History; Estados UnidosFil: HernĂĄndez del Pino, Santiago Ezequiel. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Mendoza. Instituto Argentino de NivologĂa, GlaciologĂa y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de NivologĂa, GlaciologĂa y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de NivologĂa, GlaciologĂa y Ciencias Ambientales; ArgentinaFil: Schmidt, Gabriela Ines. Provincia de Entre RĂos. Centro de Investigaciones CientĂficas y Transferencia de TecnologĂa a la ProducciĂłn. Universidad AutĂłnoma de Entre RĂos. Centro de Investigaciones CientĂficas y Transferencia de TecnologĂa a la ProducciĂłn. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Santa Fe. Centro de Investigaciones CientĂficas y Transferencia de TecnologĂa a la ProducciĂłn; ArgentinaFil: Amson, Eli. Universitat Zurich; SuizaFil: GrohĂ©, Camille. American Museum Of Natural History; Estados Unido
Fur glowing under ultraviolet: in situ analysis of porphyrin accumulation in the skin appendages of mammals
Examples of photoluminescence (PL) are being reported with increasing frequency in a wide range of organisms from diverse ecosystems. However, the chemical basis of this PL remains poorly defined, and our understanding of its potential ecological function is still superficial. Among mammals, recent analyses have identified free-base porphyrins as the compounds responsible for the reddish ultraviolet-induced photoluminescence (UV-PL) observed in the pelage of springhares and hedgehogs. However, the localization of the pigments within the hair largely remains to be determined. Here, we use photoluminescence multispectral imaging emission and excitation spectroscopy to detect, map, and characterize porphyrinic compounds in skin appendages in situ. We also document new cases of mammalian UV-PL caused by free-base porphyrins in distantly related species. Spatial distribution of the UV-PL is strongly suggestive of an endogenous origin of the porphyrinic compounds. We argue that reddish UV-PL is predominantly observed in crepuscular and nocturnal mammals because porphyrins are photodegradable. Consequently, this phenomenon may not have a specific function in intra- or interspecific communication but rather represents a byproduct of potentially widespread physiological processes.publishedVersio
Exceptional skull of huayqueriana (mammalia, litopterna, macraucheniidae) from the late miocene of Argentina: Anatomy, systematics, and peleobiological implications
The HuayquerĂas 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 HuayquerĂas (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.Fil: Forasiepi, Analia Marta. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Mendoza. Instituto Argentino de NivologĂa, GlaciologĂa y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de NivologĂa, GlaciologĂa y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de NivologĂa, GlaciologĂa y Ciencias Ambientales; ArgentinaFil: MacPhee, Ross D. E.. American Museum Of Natural History; Estados UnidosFil: HernĂĄndez del Pino, Santiago Ezequiel. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Mendoza. Instituto Argentino de NivologĂa, GlaciologĂa y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de NivologĂa, GlaciologĂa y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de NivologĂa, GlaciologĂa y Ciencias Ambientales; ArgentinaFil: Schmidt, Gabriela Ines. Provincia de Entre RĂos. Centro de Investigaciones CientĂficas y Transferencia de TecnologĂa a la ProducciĂłn. Universidad AutĂłnoma de Entre RĂos. Centro de Investigaciones CientĂficas y Transferencia de TecnologĂa a la ProducciĂłn. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Santa Fe. Centro de Investigaciones CientĂficas y Transferencia de TecnologĂa a la ProducciĂłn; ArgentinaFil: Amson, Eli. Universitat Zurich; SuizaFil: GrohĂ©, Camille. American Museum Of Natural History; Estados Unido
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