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  1. The fossil record of mammaliaforms (mammals and their closest relatives) of the Mesozoic era from the southern supercontinent Gondwana is far less extensive than that from its northern counterpart, Laurasia. Among Mesozoic mammaliaforms, Gondwanatheria is one of the most poorly known clades, previously represented by only a single cranium and isolated jaws and teeth. As a result, the anatomy, palaeobiology and phylogenetic relationships of gondwanatherians remain unclear. Here we report the discovery of an articulated and very well-preserved skeleton of a gondwanatherian of the latest age (72.1–66 million years ago) of the Cretaceous period from Madagascar that we assign to a new genus and species, Adalatherium hui. To our knowledge, the specimen is the most complete skeleton of a Gondwanan Mesozoic mammaliaform that has been found, and includes the only postcranial material and ascending ramus of the dentary known for any gondwanatherian. A phylogenetic analysis including the new taxon recovers Gondwanatheria as the sister group to Multituberculata. The skeleton, which represents one of the largest of the Gondwanan Mesozoic mammaliaforms, is particularly notable for exhibiting many unique features in combination with features that are convergent on those of therian mammals. This uniqueness is consistent with a lineage history for A. hui of isolation on Madagascar for more than 20 million years. 
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  2. Abstract

    We describe, in unprecedented detail, the petrosals and stapes of the docodontBorealestesfrom the Middle Jurassic of Scotland, using high resolution μCTand phase‐contrast synchrotron imaging. We describe the inner ear endocast and the vascularized interior structure of the petrosal, and provide the first endocranial view of a docodontan petrosal. Our study confirms some similarities in petrosal and stapedial morphology with the better knownHaldanodonof the Late Jurassic of Portugal, including: (1) the degree of curvature of the cochlea; (2) multiple features related to the highly pneumatized paroccipital region; (3) the shape of lateral trough, the fossa of the M. tensor tympani, and the ridge on the promontorium; (4) the round shape of the fenestra vestibuli; and (5) overall morphology of the stapes. ButBorealestesdiffers fromHaldanodonin having a bony ridge that separates the tympanic opening of the prootic canal, the secondary facial foramen and the hiatus Fallopii, from the fenestra vestibuli. We identify two new vascular structures: the anterior and posterior trans‐cochlear sinuses, which traverse the pars cochlearis around the cochlear nerve (VIII). These trans‐cochlear sinuses have not been observed in previous docodont specimens, and could be an autapomorphy ofBorealestes, or apomorphic for this clade. We also establish the anatomical relationship of the circum‐promontorium plexus to the inner endocast. The high quality of our scans has made these structures visible for the first time.

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