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The modern giant sperm whale Physeter macrocephalus, one of the largest known predators, preys upon cephalopods at great depths. Lacking a functional upper dentition, it relies on suction for catching its prey; in contrast, several smaller Miocene sperm whales (Physeteroidea) have been interpreted as raptorial (versus suction) feeders, analogous to the modern killer whale Orcinus orca. Whereas very large physeteroid teeth have been discovered in various Miocene localities, associated diagnostic cranial remains have not been found so far. Here we report the discovery of a new giant sperm whale from the Middle Miocene of Peru (approximately 12-13 million years ago), Leviathan melvillei, described on the basis of a skull with teeth and mandible. With a 3-m-long head, very large upper and lower teeth (maximum diameter and length of 12 cm and greater than 36 cm, respectively), robust jaws and a temporal fossa considerably larger than in Physeter, this stem physeteroid represents one of the largest raptorial predators and, to our knowledge, the biggest tetrapod bite ever found. The appearance of gigantic raptorial sperm whales in the fossil record coincides with a phase of diversification and size-range increase of the baleen-bearing mysticetes in the Miocene. We propose that Leviathan fed mostly on high-energy content medium-size baleen whales. As a top predator, together with the contemporaneous giant shark Carcharocles megalodon, it probably had a profound impact on the structuring of Miocene marine communities. The development of a vast supracranial basin in Leviathan, extending on the rostrum as in Physeter, might indicate the presence of an enlarged spermaceti organ in the former that is not associated with deep diving or obligatory suction feeding.

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The present paper describes a disarticulated skull of Allqokirus australis Marshall & Muizon, 1988, a basal sparassodont (Metatheria, Mammalia) from the early Palaeocene (c. 65 Ma.) of Tiupampa (Bolivia). The specimen includes the rostrum and palate with right premaxilla, both maxillae, left lacrimal, palatines and most upper teeth. The second largest element includes the frontals, the left squamosal, the parietals, the supraoccipital, the basisphenoid, the presphenoid, the alisphenoid, and part of the pterygoids. The nasals, basioccipital and exoccipitals are missing. Other elements are the left petrosal, the right jugal and squamosal, and both dentaries. The elements of the specimen allow for a good reconstruction of the skull, which is thoroughly described and compared to that of other sparassodonts and to the Tiupampa pucadelphyids, Pucadelphys and Andinodelphys. The dental morphology of Allqokirus australis is extremely similar to that of Patene simpsoni from the early Eocene of Itaboraí (Brazil) and presents distinct (although incipient) carnivorous adaptations. Furthermore, some characters of the ear region (e.g. medial process of the squamosal, deep groove for the internal carotid artery at the ventral apex of the petrosal) are also present in most other sparassodonts and in the pucadelphyids from the same locality. A parsimony analysis performed on the basis of a data matrix of 364 characters and 38 taxa placed Allqokirus in a sparassodont clade (the Mayulestidae) that also included Mayulestes and Patene. This family constitutes the sister group of all other sparassodonts. Our analysis also retrieved a large clade composed of the sparassodonts and the pucadelphyids, formally named Pucadelphyda n. superord. This superorder represents the large metatherian carnivorous radiation of the Tertiary of South America, which is first known at Tiupampa, and which started to diversify probably slightly earlier, during the late Cretacous in South America. So far, no representative of Pucadelphyda has been discovered in North America. At Tiupampa, Allqokirus and Mayulestes are the largest metatherians of the fauna and they fill the predaceous mammalian ecological niche. They are the earliest representatives of Sparassodonta, a successful metatherian carnivorous radiation which persisted in South America until the late Pliocene, i.e., during more than 63 Ma.