Simpson's “early burst” model of adaptive radiation was intended to explain the early proliferation of morphological and functional variation in diversifying clades. Yet, despite much empirical testing, questions remain regarding its frequency across the tree of life. Here, we evaluate the support for an early burst model of adaptive radiation in 14 ecomorphological traits plus body mass for the extant mammalian order Carnivora and its constituent families. We find strong support for early bursts of dental evolution, suggesting a classic Simpsonian adaptive radiation along dietary resource axes. However, the signal of this early burst is not consistently recovered in analyses at the family level, where support for a variety of different models emerges. Furthermore, we find no evidence for early burst–like dynamics in size–related traits, and Bayesian analyses of evolutionary correlations corroborate a decoupling of size and dental evolution, driven in part by dietary specialization. Our results are consistent with the perspective that trait diversification unfolds hierarchically, with early bursts restricted to traits associated with higher level niches, such as macrohabitat use or dietary strategy, and thus with the origins of higher taxa. The lack of support for early burst adaptive radiation in previous phylogenetic studies may be a consequence of focusing on low‐level niche traits (i.e., those associated with microhabitat use) in clades at shallow phylogenetic levels. A richer understanding of early burst adaptive radiation will require a renewed focus on functional traits and their evolution over higher level clades.

An ecomorphological study of extant small carnivorans demonstrates that dietary groups can be distinguished using quantitative morphological characters. Small (o10 kg) modern carnivorans were divided into three dietary classes: carnivores, insectivores and omnivores/hard-object feeders. Statistical analyses revealed differences between these classes including longer carnassial blades in carnivorans, as opposed to larger molar grinding areas, larger post-canine dentitions, and wider fourth premolars in omnivores/hard-object feeders. Insectivores are not consistently distinguished from other dietary types, although they do tend to have weaker dentaries and shorter temporalis muscle moment arms. These trends can be used to help interpret morphologies of taxa of uncertain ecologies, including fossil taxa.

The respiratory turbinates of mammals are complex bony plates within the nasal chamber that are covered with moist epithelium and provide an extensive surface area for the exchange of heat and water. Given their functional importance, maxilloturbinate size and structure are expected to vary predictably among species adapted to different environments. Here the first quantitative analysis is provided of maxilloturbinate structure based on high-resolution computed tomography (CT) scans of the skulls of eight canid and seven felid species. The key parameters examined were the density of the maxilloturbinate bones within the nasal chamber and how that density varied along the air pathway. In both canids and felids, total maxilloturbinate chamber volume and bone volume increased with body size, with canids having c. 1.5-2.0 times the volume of maxilloturbinate than felids of similar size. In all species, the volume of the maxilloturbinates varies from rostral to caudal, with the peak volume occurring approximately midway, close to where airway cross-sectional area is greatest. Interspecific differences among canids or felids in maxilloturbinate density were not consistent with adaptive explanations, i.e. the densest maxilloturbinates were not associated with species living in arid or cold habitats. Some of the observed variation in maxilloturbinate form might reflect a need for both low-and high-resistance pathways for airflow under alternative conditions.

In 1967 G.G. Simpson described three partial mandibles from early Miocene deposits in Kenya that he interpreted as belonging to a new strepsirrhine primate, Propotto. This interpretation was quickly challenged, with the assertion that Propotto was not a primate, but rather a pteropodid fruit bat. The latter interpretation has not been questioned for almost half a century. Here we re-evaluate the affinities of Propotto, drawing upon diverse lines of evidence to establish that this strange mammal is a strepsirrhine primate as originally suggested by Simpson. Moreover, our phylogenetic analyses support the recognition of Propotto, together with late Eocene Plesiopithecus from Egypt, as African stem chiromyiform lemurs that are exclusively related to the extant aye-aye (Daubentonia) from Madagascar. Our results challenge the long-held view that all lemurs are descended from a single ancient colonization of Madagascar, and present an intriguing alternative scenario in which two lemur lineages dispersed from Africa to Madagascar independently, possibly during the later Cenozoic.

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