Plesiocetus

Plesiocetus is a genus of extinct balaenopterids found worldwide. It has had a chequered taxonomic history, having served as a wastebasket genus for a handful of mysticete species.
Taxonomy.
The genus "Plesiocetus" was originally coined for three mysticete species from Neogene marine deposits in the vicinity of Antwerp, Belgium: "P. garopii", "P. hupschii", and "P. burtinii".
The three originally included species of "Plesiocetus" went about their separate ways. "P. garopii" was designated the type species of the genus, while the other two were referred to "Cetotherium".("P. hupschii" and "P. burtinii" were later assigned to "Plesiocetopsis", which was originally erected as a subgenus of "Cetotherium") Later, van Beneden noted the similarities of "Plesiocetus" with the fin whale, so he renamed "Plesiocetus garopii" into "Balaenoptera musculoides", which is invalid under current ICZN rules. At the same time, he also erected the new species "P. brialmontii" on the basis of fragmentary remains, while referring "Cetotherium dubius" to "Plesiocetus".
The taxonomy of "Plesiocetus" by now was confused. "Plesiocetus garopii" was referred to "Balaenoptera" (making "Plesiocetus" a synonym of "Balaenoptera"), while "P. hupschii" and "P. burtinii" were assigned to "Cetotherium". To avoid nomenclatorial complications, "Plesiocetus hupschii" was designated the type species of "Plesiocetopsis", removing any synonymy between "Plesiocetus" and "Plesiocetopsis". Recent studies, however, indicate that "Plesiocetus" shares no characters with "Balaenoptera" to the exclusion of other balaenopterids. For its part, "P. burtinii" was referred to "Aglaocetus", while "P. brialmontii" was declared a nomen dubium. These revisions leave "P. garopii" the type and only species of "Plesiocetus".
Distribution.
Fossils of "Plesiocetus" have been found in: