No animals do not have a cardiac sphincter. All animals have to have a muscle between their stomachs and esophagus to prevent food coming up. However, this muscle is able to be relaxed if food is being brought up to be chewed again (like in ruminants), or if an animal has to vomit. This muscle is designed to keep excess digesta from leaking into the esophageal tube, should the stomach (or rumen) of an animal get full from eating plenty of food. There are also cardiac sphincters between chambers of the stomach for the same reason (the first one: preventing leakage or back-wash) that there is a sphincter between the esophagus and the stomach. Check out the three sources below for further info and pictures for proof:
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