Pilosa include anteaters (Vermilingua) and sloths (Folivora). Modern tree sloths are represented ... more Pilosa include anteaters (Vermilingua) and sloths (Folivora). Modern tree sloths are represented by two genera, Bradypus and Choloepus (both around 4–6 kg), whereas the fossil record is very diverse, with approximately 90 genera ranging in age from the Oligocene to the early Holocene. Fossil sloths include four main clades, Megalonychidae, Megatheriidae, Nothrotheriidae, and Mylodontidae, ranging in size from tens of kilograms to several tons. Modern Vermilingua are represented by three genera, Cyclopes, Tamandua and Myrmecophaga, with a size range from 0.25 kg to about 30 kg, and their fossil record is scarce and fragmentary. The dependence of the body size on phylogenetic pattern of Pilosa is analysed here, according to current cladistic hypotheses. Orthonormal decomposition analysis and Abouheif C-mean were performed. Statistics were significantly different from the null-hypothesis, supporting the hypothesis that body size variation correlates with the phylogenetic pattern. Most of the correlation is concentrated within Vermilingua, and less within Mylodontidae, Megatheriidae, Nothrotheriidae and Megalonychidae. Influence of basal metabolic rate (BMR), dietary habits and substrate preference is discussed. In anteaters, specialised insectivory is proposed as the primary constraint on body size evolution. In the case of sloths, mylodontids, megatheriids and nothrotheriids show increasing body size through time; whereas megalonychids retain a wider diversity of sizes. Interplay between BMR and dietary habits appears to be the main factor in shaping evolution of sloth body size.
One of the major features of the continental Cenozoic faunas of South America is the presence of ... more One of the major features of the continental Cenozoic faunas of South America is the presence of native lineages of herbivorous mammals, and among them the largest representatives of each fauna. They include a diversity of taxa within the Xenarthra, Pyrotheria, Astrapotheria, Notoungulata, Litopterna, Cetartiodactyla, Perissodactyla, Proboscidea and Rodentia. We analyze the evolution of the large body size of these mammals in relation to their taxonomic richness. As the South American mammalian fossil record is largely restricted to southern parts of the continent, with comparatively few Tertiary land mammal-bearing localities outside of Argentina, we limit our samples to faunas from that country. Faunal lists from 6 diff erent ages were selected. Genera were classified in 4 body mass categories: (I) less than 100 kg, (II) 100 to 500 kg, (III) 500 to 1000 kg, and (IV) more than 1000 kg. The Pleistocene represents the spectacular climax in terms of body size. In general, but particul...
Glyptodonts together with armadillos, pampatheres and peltephilines constitute the Cingulata, one... more Glyptodonts together with armadillos, pampatheres and peltephilines constitute the Cingulata, one of the three clades of the Xenarthra. The most remarkable feature of this group is the presence of an armored exoskeleton along the head, body and tail. Only a few contributions have described in detail the endoskeleton. In the case of the skull, almost no attention has been focused on the narial region. The objective of this study is to provide a description of the narial anatomy of the glyptodont Neosclerocalyptus. This genus has the most expanded and globular narial region among glyptodonts and was recently described as part of the fronto-nasal sinuses system. Our analysis based on CT scanning shows that this region includes an independent ossification of the nasal cartilage that housed the maxillo-atrioturbinates. This ossification would represent a neomorphic feature produced by a terminal addition of an ossified stage via peramorphosis. Other remarkable anatomical features are the...
Durante su viaje a la Patagonia austral de 1876-1877, Francisco P. Moreno colectó un reducido núm... more Durante su viaje a la Patagonia austral de 1876-1877, Francisco P. Moreno colectó un reducido número de restos de mamíferos fósiles sobre la margen izquierda del río Santa Cruz, en yacimientos actualmente asignados a la Formación Santa Cruz (Mioceno temprano). Ya como Director del Museo de La Plata, Moreno encomendó al Asistente Preparador de Paleontología Carlos Ameghino la exploración de las barrancas del río Santa Cruz. Durante su periplo de 1887, C. Ameghino obtuvo más de 2.000 ejemplares de mamíferos fósiles. Con ellos, Florentino Ameghino reconoció la presencia de 122 taxones, de los cuales 111 eran nuevos. En una publicación de 1890, C. Ameghino declaró haber colectado dichos ejemplares en el yacimiento descubierto por Moreno en 1877 y en tres nuevos yacimientos situados sobre la margen derecha del mencionado río, cuyas ubicaciones geográficas fueron referenciadas en el mapa publicado por Moreno en 1879 en las regiones de “Swamp Bank” o “Rincón Grande”, “Basaltic Gleen” y “Ya...
High-Latitude Paleocommunities of the Santa Cruz Formation, 2012
ABSTRACT This chapter reviews the paleobiology of pilosans (anteaters and sloths) from the Santa ... more ABSTRACT This chapter reviews the paleobiology of pilosans (anteaters and sloths) from the Santa Cruz Formation, which comprise at least one genus of vermilinguan and 11 genera of sloths. Paleobiological studies performed on these xenarthrans include: estimation of body mass (through multivariate regression); analysis of the limbs so as to infer the locomotor habits and substrate use (through morphometric and qualitative-comparative morphofunctional analyses), and studies of the masticatory apparatus to infer probable feeding habits (mainly through analysis of tooth morphology and wear facets, plus the anatomy of the masticatory apparatus as a whole). Santacrucian anteaters were small animals, about 6 kg, well suited for climbing and for scratch-digging the substrate in searching for their preferred food, social insects. Various sloths were moderately large-sized forms, the largest reaching about 100 kg, with a locomotor pattern distinct from that of living sloths, resembling more that of vermilinguans and pangolins. The results suggest well-developed digging capabilities, but semi-arboreal habits cannot be ruled out. Megatherioid sloths were most likely leaf eaters, and the primary method of food reduction must have been by shearing or cutting (with a predominance of orthal movements). Mylodontid masticatory movements included a larger transverse component, and food reduction must have been by crushing and grinding, which suggests they fed on more compact, three-dimensional, and fibrous food items such as the underground storage organs of plants. The semiarboreal habits suggested for anteaters and, probably, sloths indicate they lived in forests or that forested areas were present nearby. The specialized feeding habits of vermilinguans are indicative of subtropical and warm temperate environments because they would have depended on a year-round availability of social insects.
... This author ([Tauber, 1997a] and [Tauber, 1997b]) surveyed the geology of the Santa Cruz Form... more ... This author ([Tauber, 1997a] and [Tauber, 1997b]) surveyed the geology of the Santa Cruz Formation south of Coy Inlet, reidentified the most productive fossil sites and levels, and made important collections (mostly housed at the Museo de Paleontología, National University of ...
Abstract The aim of this study is to analyze shape variation in the xenarthran femur to gain insi... more Abstract The aim of this study is to analyze shape variation in the xenarthran femur to gain insights into their behavior and locomotion. Specimens of both Cingulata (armadillos and glyptodonts) and Pilosa (anteaters and sloths) were studied and within each group body ...
... Living sloths are repre-sented by two genera, Bradypus (three-toed sloth) and Chol-oepus (two... more ... Living sloths are repre-sented by two genera, Bradypus (three-toed sloth) and Chol-oepus (two-toed sloth), which are small animals (less than 10 kg, Nowak 1999). ... She obtained very good Fig. 2 Santacrucian sloth forelimb elements. ...
The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology, 2012
Early Miocene sloths are represented by a diversity of forms ranging from 38 to 95 kg, being regi... more Early Miocene sloths are represented by a diversity of forms ranging from 38 to 95 kg, being registered mainly from Santacrucian Age deposits in southern-most shores of Patagonia, Argentina. Their postcranial skeleton differs markedly in shape from those of their closest living relatives (arboreal forms of less than 10 kg), Bradypus and Choloepus. In order to gain insight on functional properties of the Santacrucian sloths forelimb, musculature was reconstructed and a comparative, qualitative morphofunctional analysis was performed, allowing proposing hypotheses about biological role of the limb in substrate preferences, and locomotor strategies. The anatomy of the forelimb of Santacrucian sloths resembles more closely extant anteaters such as Tamandua and Myrmecophaga, due to the robustness of the elements, development of features related to attachment of ligaments and muscles, and conservative, pentadactylous, and strong-clawed manus. The reconstructed forelimb musculature was very well developed and resembles that of extant Pilosa (especially anteaters), although retaining the basic muscular configuration of generalized mammals. This musculature allowed application of powerful forces, especially in adduction of the forelimb, flexion and extension of the antebrachium, and manual prehension. These functional properties are congruent with both climbing and digging activities, and provide support for proposed Santacrucian sloths as good climbing mammals, possibly arboreal or semiarboreal, being also capable diggers. Their climbing strategies were limited, thus these forms relied mainly on great muscular strength and curved claws of the manus to move cautiously on branches.
ABSTRACT Miocene deposits of the Santa Cruz Formation, Patagonia, comprise a diverse and excellen... more ABSTRACT Miocene deposits of the Santa Cruz Formation, Patagonia, comprise a diverse and excellently preserved vertebrate fauna, allowing detailed paleobiological and paleoecological studies based on three ecological parameters: body mass, diet, and substrate preference. In contrast to the small and arboreal extant sloths, Bradypus and Choloepus, Santacrucian sloths were much more diverse and larger, and comprised 11 genera previously characterized as arboreal or climbing forms. Here, we focus on body mass estimation based on measurements of postcranial elements. We present a morphometric database comprising 64 linear, base-ten logged variables applied to Santacrucian sloths and a wide sample of extant mammals, as well as the body mass of the extant taxa as reported in the literature. To detect any potential phylogenetical bias, we performed a variance decomposition test on our sample of extant mammals. Based on four orthogram statistics, logged body mass was found not to be dependent on phylogenetic tree topology. Predictive equations for the body mass of extant mammals were generated through multiple regression analysis, using weighting procedures to avoid taxonomic biases and stepwise analysis to discard redundant variables. Using this procedure, we derived separate equations for the scapula, humerus, radius, ulna, pelvis, femur, tibia plus fibula, astragalus, and calcaneum. These equations were then applied to estimate the body mass of our sample of Santacrucian sloths. We obtained an average body mass of about 70 kg for the megalonychid Eucholoeops. Among stem megatherioids, Hapalops ranged between 30 and 80 kg, Analcimorphus was estimated at 67 kg, and Schismotherium at 44 kg. Larger genera included the megatheriid Prepotherium (∼123 kg), and the mylodontids Analcitherium (∼88 kg) and Nematherium (∼89 kg). The medium to large body size of Santacrucian sloths imposed constraints on their climbing abilities. Megalonychids and stem megatherioids were likely unable to access the finest branches, while megatheriids and mylodonts were more terrestrial forms.
Pilosa include anteaters (Vermilingua) and sloths (Folivora). Modern tree sloths are represented ... more Pilosa include anteaters (Vermilingua) and sloths (Folivora). Modern tree sloths are represented by two genera, Bradypus and Choloepus (both around 4–6 kg), whereas the fossil record is very diverse, with approximately 90 genera ranging in age from the Oligocene to the early Holocene. Fossil sloths include four main clades, Megalonychidae, Megatheriidae, Nothrotheriidae, and Mylodontidae, ranging in size from tens of kilograms to several tons. Modern Vermilingua are represented by three genera, Cyclopes, Tamandua and Myrmecophaga, with a size range from 0.25 kg to about 30 kg, and their fossil record is scarce and fragmentary. The dependence of the body size on phylogenetic pattern of Pilosa is analysed here, according to current cladistic hypotheses. Orthonormal decomposition analysis and Abouheif C-mean were performed. Statistics were significantly different from the null-hypothesis, supporting the hypothesis that body size variation correlates with the phylogenetic pattern. Most of the correlation is concentrated within Vermilingua, and less within Mylodontidae, Megatheriidae, Nothrotheriidae and Megalonychidae. Influence of basal metabolic rate (BMR), dietary habits and substrate preference is discussed. In anteaters, specialised insectivory is proposed as the primary constraint on body size evolution. In the case of sloths, mylodontids, megatheriids and nothrotheriids show increasing body size through time; whereas megalonychids retain a wider diversity of sizes. Interplay between BMR and dietary habits appears to be the main factor in shaping evolution of sloth body size.
One of the major features of the continental Cenozoic faunas of South America is the presence of ... more One of the major features of the continental Cenozoic faunas of South America is the presence of native lineages of herbivorous mammals, and among them the largest representatives of each fauna. They include a diversity of taxa within the Xenarthra, Pyrotheria, Astrapotheria, Notoungulata, Litopterna, Cetartiodactyla, Perissodactyla, Proboscidea and Rodentia. We analyze the evolution of the large body size of these mammals in relation to their taxonomic richness. As the South American mammalian fossil record is largely restricted to southern parts of the continent, with comparatively few Tertiary land mammal-bearing localities outside of Argentina, we limit our samples to faunas from that country. Faunal lists from 6 diff erent ages were selected. Genera were classified in 4 body mass categories: (I) less than 100 kg, (II) 100 to 500 kg, (III) 500 to 1000 kg, and (IV) more than 1000 kg. The Pleistocene represents the spectacular climax in terms of body size. In general, but particul...
Glyptodonts together with armadillos, pampatheres and peltephilines constitute the Cingulata, one... more Glyptodonts together with armadillos, pampatheres and peltephilines constitute the Cingulata, one of the three clades of the Xenarthra. The most remarkable feature of this group is the presence of an armored exoskeleton along the head, body and tail. Only a few contributions have described in detail the endoskeleton. In the case of the skull, almost no attention has been focused on the narial region. The objective of this study is to provide a description of the narial anatomy of the glyptodont Neosclerocalyptus. This genus has the most expanded and globular narial region among glyptodonts and was recently described as part of the fronto-nasal sinuses system. Our analysis based on CT scanning shows that this region includes an independent ossification of the nasal cartilage that housed the maxillo-atrioturbinates. This ossification would represent a neomorphic feature produced by a terminal addition of an ossified stage via peramorphosis. Other remarkable anatomical features are the...
Durante su viaje a la Patagonia austral de 1876-1877, Francisco P. Moreno colectó un reducido núm... more Durante su viaje a la Patagonia austral de 1876-1877, Francisco P. Moreno colectó un reducido número de restos de mamíferos fósiles sobre la margen izquierda del río Santa Cruz, en yacimientos actualmente asignados a la Formación Santa Cruz (Mioceno temprano). Ya como Director del Museo de La Plata, Moreno encomendó al Asistente Preparador de Paleontología Carlos Ameghino la exploración de las barrancas del río Santa Cruz. Durante su periplo de 1887, C. Ameghino obtuvo más de 2.000 ejemplares de mamíferos fósiles. Con ellos, Florentino Ameghino reconoció la presencia de 122 taxones, de los cuales 111 eran nuevos. En una publicación de 1890, C. Ameghino declaró haber colectado dichos ejemplares en el yacimiento descubierto por Moreno en 1877 y en tres nuevos yacimientos situados sobre la margen derecha del mencionado río, cuyas ubicaciones geográficas fueron referenciadas en el mapa publicado por Moreno en 1879 en las regiones de “Swamp Bank” o “Rincón Grande”, “Basaltic Gleen” y “Ya...
High-Latitude Paleocommunities of the Santa Cruz Formation, 2012
ABSTRACT This chapter reviews the paleobiology of pilosans (anteaters and sloths) from the Santa ... more ABSTRACT This chapter reviews the paleobiology of pilosans (anteaters and sloths) from the Santa Cruz Formation, which comprise at least one genus of vermilinguan and 11 genera of sloths. Paleobiological studies performed on these xenarthrans include: estimation of body mass (through multivariate regression); analysis of the limbs so as to infer the locomotor habits and substrate use (through morphometric and qualitative-comparative morphofunctional analyses), and studies of the masticatory apparatus to infer probable feeding habits (mainly through analysis of tooth morphology and wear facets, plus the anatomy of the masticatory apparatus as a whole). Santacrucian anteaters were small animals, about 6 kg, well suited for climbing and for scratch-digging the substrate in searching for their preferred food, social insects. Various sloths were moderately large-sized forms, the largest reaching about 100 kg, with a locomotor pattern distinct from that of living sloths, resembling more that of vermilinguans and pangolins. The results suggest well-developed digging capabilities, but semi-arboreal habits cannot be ruled out. Megatherioid sloths were most likely leaf eaters, and the primary method of food reduction must have been by shearing or cutting (with a predominance of orthal movements). Mylodontid masticatory movements included a larger transverse component, and food reduction must have been by crushing and grinding, which suggests they fed on more compact, three-dimensional, and fibrous food items such as the underground storage organs of plants. The semiarboreal habits suggested for anteaters and, probably, sloths indicate they lived in forests or that forested areas were present nearby. The specialized feeding habits of vermilinguans are indicative of subtropical and warm temperate environments because they would have depended on a year-round availability of social insects.
... This author ([Tauber, 1997a] and [Tauber, 1997b]) surveyed the geology of the Santa Cruz Form... more ... This author ([Tauber, 1997a] and [Tauber, 1997b]) surveyed the geology of the Santa Cruz Formation south of Coy Inlet, reidentified the most productive fossil sites and levels, and made important collections (mostly housed at the Museo de Paleontología, National University of ...
Abstract The aim of this study is to analyze shape variation in the xenarthran femur to gain insi... more Abstract The aim of this study is to analyze shape variation in the xenarthran femur to gain insights into their behavior and locomotion. Specimens of both Cingulata (armadillos and glyptodonts) and Pilosa (anteaters and sloths) were studied and within each group body ...
... Living sloths are repre-sented by two genera, Bradypus (three-toed sloth) and Chol-oepus (two... more ... Living sloths are repre-sented by two genera, Bradypus (three-toed sloth) and Chol-oepus (two-toed sloth), which are small animals (less than 10 kg, Nowak 1999). ... She obtained very good Fig. 2 Santacrucian sloth forelimb elements. ...
The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology, 2012
Early Miocene sloths are represented by a diversity of forms ranging from 38 to 95 kg, being regi... more Early Miocene sloths are represented by a diversity of forms ranging from 38 to 95 kg, being registered mainly from Santacrucian Age deposits in southern-most shores of Patagonia, Argentina. Their postcranial skeleton differs markedly in shape from those of their closest living relatives (arboreal forms of less than 10 kg), Bradypus and Choloepus. In order to gain insight on functional properties of the Santacrucian sloths forelimb, musculature was reconstructed and a comparative, qualitative morphofunctional analysis was performed, allowing proposing hypotheses about biological role of the limb in substrate preferences, and locomotor strategies. The anatomy of the forelimb of Santacrucian sloths resembles more closely extant anteaters such as Tamandua and Myrmecophaga, due to the robustness of the elements, development of features related to attachment of ligaments and muscles, and conservative, pentadactylous, and strong-clawed manus. The reconstructed forelimb musculature was very well developed and resembles that of extant Pilosa (especially anteaters), although retaining the basic muscular configuration of generalized mammals. This musculature allowed application of powerful forces, especially in adduction of the forelimb, flexion and extension of the antebrachium, and manual prehension. These functional properties are congruent with both climbing and digging activities, and provide support for proposed Santacrucian sloths as good climbing mammals, possibly arboreal or semiarboreal, being also capable diggers. Their climbing strategies were limited, thus these forms relied mainly on great muscular strength and curved claws of the manus to move cautiously on branches.
ABSTRACT Miocene deposits of the Santa Cruz Formation, Patagonia, comprise a diverse and excellen... more ABSTRACT Miocene deposits of the Santa Cruz Formation, Patagonia, comprise a diverse and excellently preserved vertebrate fauna, allowing detailed paleobiological and paleoecological studies based on three ecological parameters: body mass, diet, and substrate preference. In contrast to the small and arboreal extant sloths, Bradypus and Choloepus, Santacrucian sloths were much more diverse and larger, and comprised 11 genera previously characterized as arboreal or climbing forms. Here, we focus on body mass estimation based on measurements of postcranial elements. We present a morphometric database comprising 64 linear, base-ten logged variables applied to Santacrucian sloths and a wide sample of extant mammals, as well as the body mass of the extant taxa as reported in the literature. To detect any potential phylogenetical bias, we performed a variance decomposition test on our sample of extant mammals. Based on four orthogram statistics, logged body mass was found not to be dependent on phylogenetic tree topology. Predictive equations for the body mass of extant mammals were generated through multiple regression analysis, using weighting procedures to avoid taxonomic biases and stepwise analysis to discard redundant variables. Using this procedure, we derived separate equations for the scapula, humerus, radius, ulna, pelvis, femur, tibia plus fibula, astragalus, and calcaneum. These equations were then applied to estimate the body mass of our sample of Santacrucian sloths. We obtained an average body mass of about 70 kg for the megalonychid Eucholoeops. Among stem megatherioids, Hapalops ranged between 30 and 80 kg, Analcimorphus was estimated at 67 kg, and Schismotherium at 44 kg. Larger genera included the megatheriid Prepotherium (∼123 kg), and the mylodontids Analcitherium (∼88 kg) and Nematherium (∼89 kg). The medium to large body size of Santacrucian sloths imposed constraints on their climbing abilities. Megalonychids and stem megatherioids were likely unable to access the finest branches, while megatheriids and mylodonts were more terrestrial forms.
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