Relationships of the Megatheriinae, Nothrotheriinae, and Planopsinae: some skeletal characteristics and their importance for phylogeny

Iuliis, Gerardo De

doi:10.1080/02724634.1995.10011579

Cited by 42 publications

(59 citation statements)

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“…Behind this process, the straight lateral margin angles posteromedially, so that the medial ramus tapers to a sharp point posteriorly. The minimum width of the medial ramus is less than half the minimum width of the lateral ramus, as in Eucholoeops (Table 1; Scott 1903-4;Bargo et al 2009), although the overall shape of the medial ramus more closely resembles that of Hapalops (Scott 1903-4;De Iuliis 1994), due to the presence of the triangular lateral process. The left and right medial rami are sutured at the midline in C. didactylus (UTCM 1000; AMNH 133405), but fused across the midline in C. hoffmanni (UTCM 1912; AMNH 26918); however, this may represent age differences in the specimens rather than interspecific variation.…”

Section: And 5)mentioning

confidence: 85%

“…1,2,3,4 and 5) Choloepus species have a V-shaped premaxilla in both dorsal and ventral views (Naples 1982;Gaudin 2004). The shape of the medial ramus of Choloepus hoffmanni (CM 3883) resembles that of the basal megatherioid Hapalops elongatus (Scott 1903-4;De Iuliis 1994), and the two even bear a similarly shaped incisive foramen (see below). The lateral ramus of the premaxilla is sutured posteriorly to the maxilla.…”

Section: Methodsmentioning

confidence: 93%

“…Hapalops (Scott 1903-4;De Iuliis 1994), where the process adjoins the sagittal plane along its medial edge and extends straight forward anteriorly. This would have created a rather distinct, deep V-shaped median notch in the anterior margin of the paired premaxillae when in articulation (Fig.…”

Section: Methodsmentioning

confidence: 99%

“…Its minimum width is roughly 70 % that of the lateral ramus (Table 1). As in Choloepus and Hapalops (Scott 1903-4;De Iuliis 1994), the lateral edge bears a lateral process at roughly the midpoint of its length, though the process in Choloepus and Hapalops is much smaller than that of Acratocnus. The margin posterior to this process is irregularly convex laterally, the ramus itself ending posteromedially in a sharp point as in Choloepus.…”

Section: And 5)mentioning

confidence: 95%

“…In the megathere Megatherium and the scelidothere, Scelidotherium, the lateral ramus is often fused to the skull and the premaxilla is commonly preserved, though curiously this is not the case in their respective close Neotropical relatives, Eremotherium and Catonyx. Despite its infrequent preservation, De Iuliis (1994) has shown that the bone exhibits significant variation among living and fossil sloths that can be systematically informative.…”

Section: Introductionmentioning

confidence: 99%

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Premaxillae of the Extinct Megalonychid Sloths Acratocnus, Neocnus, and Megalonyx, and their Phylogenetic Implications (Mammalia, Xenarthra)

Lyon

Powell

McDonald³

et al. 2015

J Mammal Evol

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In most folivorans, the premaxilla is loosely attached to the maxilla, so that it is often missing in otherwise very well-preserved fossil skulls. Despite its infrequent preservation in sloths, the premaxilla has been shown to have phylogenetically significant variation among the taxa that do preserve the element. In the family Megalonychidae, the premaxilla is known only in the early taxon Eucholoeops (Santacrucian South American Land Mammal Age [SALMA]), the extant two-toed sloth Choloepus, and the North American Neogene taxon Megalonyx, the last described only in an unpublished Master's thesis. We report here the discovery of the premaxilla in two genera of extinct megalonychids, Neocnus and Acratocnus. These small bodied, semiarboreal megalonychid sloths are endemic to the islands of the Greater Antilles. Though the presence of sloths in the Caribbean dates at least to the late Oligocene, the best known taxa derive from Pleistocene to Holocene cave deposits in Puerto Rico, Hispaniola, and Cuba. We also describe the premaxilla in two species of Megalonyx from North America, the Blancan North American Land Mammal Age (NALMA) M. leptostomus and Rancholabrean NALMA M. jeffersonii. These species show a progressive reorientation of the premaxilla within Megalonyx from a primitive horizontal element to a nearly vertical element, and some significant changes in the anatomy of the incisive foramen. Morphological evidence suggests that a broadened, plate-like premaxilla constitutes a synapomorphy for the entire clade Megalonychidae. Furthermore, although Eucholoeops retains a short anterior process of the premaxilla like that of megatherioid sloths, this process is lacking in the other megalonychids, suggesting that the loss of this process may unite late Miocene to Recent megalonychids.

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Section: And 5)mentioning

confidence: 85%

Section: Methodsmentioning

confidence: 93%

Section: Methodsmentioning

confidence: 99%

Section: And 5)mentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

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Premaxillae of the Extinct Megalonychid Sloths Acratocnus, Neocnus, and Megalonyx, and their Phylogenetic Implications (Mammalia, Xenarthra)

Lyon

Powell

McDonald³

et al. 2015

J Mammal Evol

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Muscular reconstruction and functional morphology of the hind limb of santacrucian (Early Miocene) sloths (Xenarthra, Folivora) of Patagonia

Toledo

Bargo

Vizcaı́no

2015

The Anatomical Record

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This article presents a morphofunctional analysis of the hind limb of Santacrucian (Early Miocene) sloths from southernmost Patagonia (Argentina). These fossil sloths were mid sized to large animals, ranging from 40 to 120 kg, and their postcranial skeleton was markedly different in shape compared with that of extant tree sloths, which vary from 2 to 10 kg. The functional anatomy of the hind limb of Santacrucian sloths was compared with that of living xenarthrans (tree sloths, anteaters, and armadillos), which involved reconstruction of the hind limb musculature and comparative and qualitative morphofunctional analyses, and hypotheses on the biological role of the hind limb in terms of preferences in substrate, posture, and strategies of locomotion were formulated. The hind limb of Santacrucian sloths bears strong resemblances to that of living South American anteaters in stoutness of skeletal elements, form of the characteristics related to muscular and ligamentous attachments, and conservative, pentadactylous strong-clawed pes. The musculature was very well developed, allowing powerful forces, principally in entire limb adduction, crus flexion and extension, pes extension, and toe prehension. These functional features, together with those of the forelimb, are congruent with climbing behavior, and support the hypothesis that Santacrucian sloths were good but slow climbing mammals. However, their climbing strategies were limited, owing principally to their comparatively large body size, and they relied to a large extent on their powerful musculature and curved manual and pedal unguals for both moving and standing on the arboreal supports. Anat Rec, 298:842-864, 2015. V C 2015 Wiley Periodicals, Inc.Key words: paleoecology; Santa Cruz Formation; climbing; substrate use; substrate preferences

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The late Oligocene xenarthran fauna of Quebrada Fiera (Mendoza, Argentina) and its implications for sloth origins and the diversity of Palaeogene cingulates

Pujos

Ciancio

Forasiepi

et al. 2021

Papers in Palaeontology

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The late Oligocene mammalian fauna of Quebrada Fiera is one of the most diverse of the Deseadan SALMA (South American Land Mammal Age). We describe its endemic xenarthran assemblage, represented by 13 species, consisting of 2 stem sloths and 11 armoured cingulates. The rare folivoran material confirms the presence of Octodontotherium, one of the early known mylodontids, and suggests the existence of a new, small, non-megalonychid megatherioid, Similhapalops nivis. The lumbar vertebrae of Octodontotherium sp. provide the oldest evidence of xenarthry for the order. The presence at the knee joint of an ossified meniscus and cyamo-fabella strongly suggests a plantigrade ancestral condition in Mylodontidae. Armoured xenarthrans are represented by the armadillos Eutatini (Meteutatus sp., M. lagenaformis, and Stenotatus ornatus), an undetermined Euphractinii, the 'horned' peltephilids Peltephilus sp. and P. undulatus, and the palaeopeltid Palaeopeltis inornatus; an undetermined Glyptodontidae, the glyptatelines Glyptatelus cf. tatusinus and Clypeotherium sp., and an undetermined propalaehoplophorine. The xenarthrans represent one-third of the mammals of the Quebrada Fiera fauna, one of the most varied at the end of the Palaeogene in South America. This vertebrate fauna is represented by a mix of endemic taxa and other species of high latitude (Patagonian) origin, but few from low latitude faunas. A detailed study of this mammalian assemblage, complemented by detailed geological and petrographical studies, suggests the existence of strong volcanic activity, and the presence of braided rivers and lagoonal environments in open habitats under a temperate or hot climate, with savannas and/or grasslands and isolated forests during the late Oligocene at the foot of the proto-Andes.

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Relationships of the Megatheriinae, Nothrotheriinae, and Planopsinae: some skeletal characteristics and their importance for phylogeny

Cited by 42 publications

References 12 publications

Premaxillae of the Extinct Megalonychid Sloths Acratocnus, Neocnus, and Megalonyx, and their Phylogenetic Implications (Mammalia, Xenarthra)

Premaxillae of the Extinct Megalonychid Sloths Acratocnus, Neocnus, and Megalonyx, and their Phylogenetic Implications (Mammalia, Xenarthra)

Muscular reconstruction and functional morphology of the hind limb of santacrucian (Early Miocene) sloths (Xenarthra, Folivora) of Patagonia

The late Oligocene xenarthran fauna of Quebrada Fiera (Mendoza, Argentina) and its implications for sloth origins and the diversity of Palaeogene cingulates

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