Inferring differential behavior between giant ground sloth adults and juveniles through scapula morphology

Grass, Andy

doi:10.1080/02724634.2019.1569018

Cited by 7 publications

(5 citation statements)

References 41 publications

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“…2020). This pattern was observed especially when anterior appendicular elements were investigated, and is in contrast to our results, which, like morphometric evaluations of scapular morphology, suggest a lesser degree of differentiation between suspensory and semi‐arboreal taxa (Toledo 2016; Grass 2019). Some studies of humeral morphology that included a larger taxonomic fossil sample also recovered some historical signal, with terrestrial mylodontoids and megatheriids occupying slightly distinct morphospace regions, whereas stem megatherioids, megalonychids, stem megatheriids and nothrotherines clustered together, along with other semi‐arboreal taxa (Oliveira & Santos 2018; Serio et al .…”

Section: Discussioncontrasting

confidence: 99%

“…The members of Megalonychidae associated with terrestrial adaptations, such as Megalonyx Harlan, and the genera included in Ahytheriini, did not show much dissimilarity relative to their scansorial kin, and it is unlikely that adult individuals of these taxa possessed a semi‐arboreal lifestyle (De Iuliis et al . 2009; Grass 2019). One possible explanation for this pattern would be that those taxa adapted to terrestrial habits with little postcranial modification, co‐opting the semi‐arboreal skeleton of stem megalonychids to perform exclusive ambulatory functions.…”

Section: Discussionmentioning

confidence: 99%

“…2012; Toledo 2016; Amson & Nyakatura 2018; Oliveira & Santos 2018; Vizcaíno et al . 2018; Grass 2019; Serio et al . 2020).…”

mentioning

confidence: 99%

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Morphological disparity and evolutionary rates of cranial and postcranial characters in sloths (Mammalia, Pilosa, Folivora)

et al. 2023

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Sloth morphological evolution has been widely studied qualitatively, with comparative anatomy and morpho‐functional approaches, or through quantitative assessments of morphological variation using morphometrics. Only recently, however, have folivoran morphological disparity and evolutionary rates begun to be evaluated using discrete character data. Nonetheless, patterns of morphological evolution in separate character partitions have not been investigated, neither the relative influence of, on the one hand, phylogeny, and on the other, dietary and locomotory adaptations of sloths. Here we evaluate those patterns using a phylomorphospace approach, quantifying morphological disparity and evolutionary rates, and investigating possible drivers of morphological evolution for cranial and postcranial characters in Folivora. The evolution of the morphology in those partitions is associated with distinct patterns of disparity among clades and ecological groups, even though the two partitions do not differ substantially in overall evolutionary tempo. Historical processes shaped the morphological evolution of sloths more consistently than ecological ones, although changes in postcranial characters also seem to be associated with locomotory adaptations, in which morphological convergences were much more common. We also discuss important methodological trade‐offs in investigations of partitioned datasets mostly composed of fossil taxa.

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confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Morphological disparity and evolutionary rates of cranial and postcranial characters in sloths (Mammalia, Pilosa, Folivora)

et al. 2023

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“…However, the parietal/occipital suture is still open and indicates that the posterior portion of the cranium matures late in M. jeffersonii. Grass (2019), in a morphometric study of ground sloth scapulae, documents that the Tarkio juveniles are those of Megalonyx.…”

Section: Systematic Paleontologymentioning

confidence: 99%

“…jeffersonii . Grass (2019), in a morphometric study of ground sloth scapulae, documents that the Tarkio juveniles are those of Megalonyx .…”

Section: Systematic Paleontologymentioning

confidence: 99%

Paleobiology of Jefferson’s Ground Sloth (Megalonyx jeffersonii) derived from three contemporaneous, ontogenetically distinct individuals recovered from Southwestern Iowa, U.S.A.

Semken

McDonald²,

Graham

et al. 2022

Journal of Vertebrate Paleontology

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Although known from more than 180 sites in North America, sites with records of multiple Megalonyx elements and individuals are rare. The Tarkio site in southwestern Iowa is unique with three contemporaneous individuals at different stages of development. Among these is one of the largest (ca. 1286 kg) and most complete adult Megalonyx jeffersonii skeletons (ca. 50%, NISP, 123) known. An intermingled sub-adult (ca. 25%, NISP, 63) represents a comparatively complete skeleton for this ontogenetic stage. A third individual, an infant known only from both scapulae (NISP 2), is commingled with sub-adult remains. Scapula sizes indicate that the two juveniles were 50 and 30% of the adult's size. Differential bone preservation and pattern of scatter shows that the adult decomposed lying on its left side and the remains were partially scavenged. Multiple taphonomic proxies demonstrate that the skeletons were subaerially exposed for a limited period, but fluvial transport was not a factor. These individuals, preserved in the same low-energy microstratigraphic unit, apparently died concurrently and probably represent a Megalonyx social unit. Using mammal body size to estimate life history, the estimated average lifespan for M. jeffersonii was around 19 years; gestation time was about 14 months; the interbirth interval was approximately 3 years; and sexual maturation occurred at around 6.5 years. OSL analysis indicates that the sloths were deposited about 106,000 years ago (MIS substage 5ec). Paleoenvironmental proxies suggest an interglacial environment of open woodland along a stream with marshes, like the environment in southwest Iowa today.

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Inferences of the ecological habits of extinct giant sloths from the Brazilian Intertropical Region

Santos

McDonald²,

Dantas

2023

J Quaternary Science

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Three indices estimated from measurements of the humerus and ulna were used to suggest possible ecological habits of eight extinct giant sloths from the Late Pleistocene of the Brazilian Intertropical Region. To make these inferences, data from extant primates and xenarthras representing suspensory, climbing and digging forms were compared. The results indicate niche differentiation existed between these species; Ahytherium aureum, Australonyx aquae and Nothrotherium maquinense could have been climbers, Catonyx cuvieri, Ocnotherium giganteum and Glossotherium phoenesis were diggers, while Valgipes bucklandi and Eremotherium laurillardi were strictly terrestrial in their habits. These results suggest a general pattern in which members of the Megalonychidae and Nothotheriidae were mainly climbers, whereas mylodontines were mainly diggers, and scelidotheres were strictly terrestrial along with members of the giant Megatheriidae.

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Inferring differential behavior between giant ground sloth adults and juveniles through scapula morphology

Cited by 7 publications

References 41 publications

Morphological disparity and evolutionary rates of cranial and postcranial characters in sloths (Mammalia, Pilosa, Folivora)

Morphological disparity and evolutionary rates of cranial and postcranial characters in sloths (Mammalia, Pilosa, Folivora)

Paleobiology of Jefferson’s Ground Sloth (Megalonyx jeffersonii) derived from three contemporaneous, ontogenetically distinct individuals recovered from Southwestern Iowa, U.S.A.

Inferences of the ecological habits of extinct giant sloths from the Brazilian Intertropical Region

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