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New World porcupines (Erethizontinae) originated in South America and dispersed into North America as part of the Great American Biotic Interchange (GABI) 3-4 million years ago. 1 Extant prehensile-tailed porcupines (Coendou) today live in tropical forests of Central and South America. 2 , 3 In contrast, North American porcupines (Erethizon dorsatum) are thought to be ecologically adapted to higher-latitude temperate forests, with a larger body, shorter tail, and diet that includes bark. 4 , 5 , 6 , 7 Limited fossils 8 , 9 , 10 , 11 , 12 , 13 have hindered our understanding of the timing of this ecological differentiation relative to intercontinental dispersal during the GABI and expansion into temperate habitats. 14 , 15 , 16 , 17 , 18 Here, we describe functionally important features of the skeleton of the extinct Erethizon poyeri, the oldest nearly complete porcupine skeleton documented from North America, found in the early Pleistocene of Florida. It differs from extant E. dorsatum in having a long, prehensile tail, grasping foot, and lacking dental specializations for bark gnawing, similar to tropical Coendou. Results from phylogenetic analysis suggest that the more arboreal characteristics found in E. poyeri are ancestral for erethizontines. Only after it expanded into temperate, Nearctic habitats did Erethizon acquire the characteristic features that it is known for today. When combined with molecular estimates of divergence times, results suggest that Erethizon was ecologically similar to a larger species of Coendou when it crossed the Isthmus of Panama by the early Pleistocene. It is likely that the range of this more tropically adapted form was limited to a continuous forested biome that extended from South America through the Gulf Coast., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The paleodiet of the shovel-tusked gomphotheres from Florida (Amebelodon floridanus, Konobelodon britti, and Serbelodon barbourensis) was assessed via microwear analysis of molar dental enamel and compared to a large database of both extant proboscideans and ungulates. Scratch and pit results show a consistent browsing signal in A. floridanus, K. britti and S. barbourensis. Fossil results are more similar to those of the extant Loxodonta cyclotis than to Loxodonta africana or Elephas maximus, the latter two taxa exhibiting a mixed feeding result. Scratch width scores are high in all three shovel tuskers as well as in the extant proboscideans indicating the ingestion of some coarse vegetation, most likely bark, and twigs. Gouging is relatively low in A. floridanus and S. barbourensis. Only K. britti has levels of gouging approximating that seen in extant elephants. Large pitting is relatively low in both fossil and extant forms although L. cyclotis has higher levels of large pitting including more puncture-like pits seen with fruit and/or seed consumption. A variety of scratch patterns indicating variation in tusk usage behavior was found. Some Serbelodon and Konobelodon mandibular tusks exhibited digging behavior, although Konobelodon digging behavior was much more common and obvious, whereas Amebelodon mandibular tusks did not exhibit digging behavior and were more likely used for stripping and scraping. Unusual distal tusk wear was found in Amebelodon and Serbelodon most likely due to stripping off tree bark. Upper tusk usage varied with all three fossil species exhibiting scraping and/or cutting behavior. Results indicate that shovel-tusked gomphotheres from Florida occupied a narrow dietary niche but employed a variety of strategies to obtain the vegetation that they consumed.

Although shark teeth are abundant in the fossil record, their bodies are rarely preserved. Thus, our understanding of the anatomy of the extinct Otodus megalodon remains rudimentary. We used an exceptionally well-preserved fossil to create the first three-dimensional model of the body of this giant shark and used it to infer its movement and feeding ecology. We estimate that an adult O. megalodon could cruise at faster absolute speeds than any shark species today and fully consume prey the size of modern apex predators. A dietary preference for large prey potentially enabled O. megalodon to minimize competition and provided a constant source of energy to fuel prolonged migrations without further feeding. Together, our results suggest that O. megalodon played an important ecological role as a transoceanic superpredator. Hence, its extinction likely had large impacts on global nutrient transfer and trophic food webs.