very widespread, with gobiconodontids and Zhangheotherium being among the clearer examples. The absence of venom spurs in non-Mammaliaformes cynodonts suggests that venom was an ancient mammalian synapomorphy and ancestral characteristic. Canine teeth dated at 60 million years old from two extinct species, the shrew-like Bisonalveus browni and another unidentified mammal, show grooves that some palaeontologists have argued are indicative of a venomous bite. However, other scientists have questioned this conclusion given that many living non-venomous mammals also have deep grooves down the length of their canines (e.g., many primates, coatis and fruit bats), suggesting that this feature does not always reflect an adaptation to venom delivery. Examples Eulipotyphla (previously known as insectivores) With the exception of vampire bats, the Eulipotyphla are the only mammals so far observed to produce toxic saliva. These species have significantly enlarged and granular submaxillary salivary glands from which the toxic saliva is produced. The Cuban solenodon (Atopogale cubana) and Hispaniolan solenodon (Solenodon paradoxus) look similar to large shrews. They both have venomous bites; the venom is delivered from modified salivary glands via grooves in their second lower incisors. Recent study has identified the gene regulatory network responsible for the development of venom delivery systems in these small mammals. Due to the overexpression of kallikreins in their saliva, solenodon bites cause vasodilation and may result in circulatory shock. It was reported that death was frequent among Hispaniolan solenodons kept together in the same enclosure, with bite marks on their feet being the only observable cause. Such use in competition may be a secondary aspect of the insectivore venom. The northern short-tailed shrew (Blarina brevicauda), Mediterranean water shrew (Neomys anomalus), and Eurasian water shrew (Neomys fodiens) are capable of delivering a venomous bite. Other American short-tailed shrews: the southern short-tailed shrew (Blarina carolinensis), Elliot's short-tailed shrew (Blarina hylophaga), and Everglades short-tailed shrew (Blarina peninsulae) and the Transcaucasian water shrew (Neomys teres) possibly also have a venomous bite. Shrews cache various prey in a comatose state, including earthworms, insects, snails, and to a lesser extent, small mammals such as voles and mice. This behaviour is an adaption to winter. In this context, the shrew venom acts as a tool to sustain a living hoard, thus ensuring food supply when capturing prey is difficult. This is especially important considering the high metabolic rate of shrews. Arguments against this suggest that the venom is used as a tool to hunt