Discussion of some problematic extinct groups. Several fossil groups of mysticetes (e.g., Aetiocetidae and Cetotheriidae) are still taxonomically problematic; it is very likely that some of them form

Several fossil groups of mysticetes (e.g., Aetiocetidae and Cetotheriidae) are still taxonomically problematic; it is very likely that some of them form paraphyletic groups. Systematic revisions, additional anatomical data and cladistic analyses will be required before reaching reasonable hypotheses regarding the phylogeny of these groups.

• The Oligocene family Aetiocetidae (review in Barnes et al. 1994) includes primitive toothed mysticetes (some of them having been erroneously placed within archaeocetes), showing a mix of archaeocete-like and mysticete-like skull features. This family persisted into Late Oligocene, at a time where more derived baleen-bearing whales had already evolved. Specimens have been found on both sides of the North Pacific.
• The fossil specimens from other archaic toothed mysticete families (Llanocetidae, Mammalodontidae, and Kekenodontidae) have not been studied extensively enough to be meaningfully included into phylogenetic analyses. Members of these families, may have used their teeth for bulk feeding rather than for selecting individual preys, but functional studies are needed to confirm this hypothesis (Fordyce and Barnes, 1994).
• Cetotheriidae is a very diverse paraphyletic family of Late Oligocene to Late Pliocene baleen-bearing whales. Many taxa are based on fragmentary material, leading to difficulties when trying to correlate taxa from distant fossil localities. Some cetotheriids exhibit character states reasonably interpreted as ancestral for balaenopterids (Mc Leod et al. 1993; Kimura and Ozawa, 2002). Among Cetotheriidae s.l., Bouetel and Muizon (2006) isolate a monophyletic Cetotheriidae s.s., supported by a series of cranial characters and including six genera (Cetotherium, Herpetocetus, Metopocetus, Mixocetus, Nannocetus, and Piscobalaena).

Дата добавления: 2015-08-03