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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.)

Teeth are present in most clades of vertebrates but have been lost completely several times in actinopterygian fishes and amniotes. Using phenotypic data collected from over 500 genera via micro-computed tomography, we provide the first rigorous assessment of the evolutionary history of dentition across all major lineages of amphibians. We demonstrate that dentition is invariably present in caecilians and salamanders, but teeth have been lost completely more than 20 times in frogs, a much higher occurrence of edentulism than in any other vertebrate group. The repeated loss of teeth in anurans is associated with a specialized diet of small invertebrate prey as well as shortening of the lower jaw, but it is not correlated with a reduction in body size. Frogs provide an unparalleled opportunity for investigating the molecular and developmental mechanisms of convergent tooth loss on a large phylogenetic scale., Competing Interests: DP, KR, CE, MH, GJ, RK, FM, SN, MV, ES, DB No competing interests declared, (© 2021, Paluh et al.)

The nearly 200 species of direct-developing frogs in the genus Eleutherodactylus (the Caribbean landfrogs, which include the coquís) comprise an important lineage for understanding the evolution and historical biogeography of the Caribbean. Time-calibrated molecular phylogenies provide indirect evidence for the processes that shaped the modern anuran fauna, but there is little direct evidence from the fossil record of Caribbean frogs about their distributions in the past. We report a distal humerus of a frog from the Oligocene (approx. 29 Ma) of Puerto Rico that represents the earliest known fossil frog from any Caribbean island. Based on its prominent rounded distal humeral head, distally projecting entepicondyle, and reduced ectepicondyle, we refer it to the genus Eleutherodactylus . This fossil provides additional support for an early arrival of some groups of terrestrial vertebrates to the Greater Antilles and corroborates previous estimates based on molecular phylogenies suggesting that this diverse Caribbean lineage was present in the islands by the mid-Cenozoic.