''Chronoperates'' (meaning "time wanderer" in Greek) is an extinct genus of

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...

whose remains have been found in a late Paleocene deposit in Alberta, Canada. It is represented by the type species ''Chronoperates paradoxus'' and known only from a partial left lower jaw. It was first identified in 1992 as a non-mammalian

cynodont The cynodonts () (clade Cynodontia) are a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 mya), and extensively diversified after the Permian–Triassic extinction event. Cynodonts had a wide variety ...

, implying a ghost lineage of over 100 million years since the previously youngest known record of non-mammalian cynodonts, which at that time was in the Jurassic period (some non-mammalian cynodonts are now known to have persisted until the

Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pro ...

). Subsequent authors have challenged this interpretation, particularly as the teeth do not resemble any known non-mammalian cynodonts. ''Chronoperates'' is now generally considered to be more likely to be a late-surviving

symmetrodont Symmetrodonta is a group of Mesozoic mammals and mammal-like synapsids characterized by the triangular aspect of the molars when viewed from above, and the absence of a well-developed talonid. The traditional group of 'symmetrodonts' ranges in a ...

mammal. This would still infer a ghost lineage for symmetrodonts, but a more plausible one, as symmetrodonts persisted into the Late Cretaceous.

References

http://darrennaish.blogspot.com/2006/05/time-wandering-cynodonts-and-docodonts.html https://web.archive.org/web/20081219051716/http://www.palaeos.com/Vertebrates/Units/410Cynodontia/410.400.html Symmetrodonta Prehistoric mammals of North America Paleocene mammals Fossil taxa described in 1992 Taxa named by Richard C. Fox Taxa named by Gordon P. Youzwyshyn Taxa named by David W. Krause Prehistoric mammal genera {{paleo-mammal-stub Species known from a single specimen