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''Zygorhiza'' ("Yoke-Root") is an extinct genus of basilosaurid early whale known from the Late Eocene (Priabonian, 38–34 Ma) of Louisiana, Alabama, and Mississippi, United States, and the Bortonian (43–37 Ma on the New Zealand geologic time scale) to the late Eocene of New Zealand ().〔. Retrieved July 2013〕 Specimens reported from Europe are considered Dorudontinae ''incertae sedis''. ''Zygorhiza kochii'' is the state fossil of Mississippi. The mounted specimen in the Mississippi Museum of Natural Science in Jackson is commonly referred to as "Ziggy". ==Taxonomic history== In the late 19th century there was a debate whether large and small specimens of ''Zeuglodon brachyspondylus'' (=''Basilosaurus'', but the species is now considered a ''nomen nudum'') were separate species or not. Hoping to clarify things, proposed using ''Z. brachyspondylus'' exclusively for large fossils and created the subspecies ''Z. brachyspondylus minor'' for the small specimens which had previously been synonymized with ''Dorudon serratus''. proposed the genus ''Zygorhiza'' for the subspecies. Adopting True's generic name, synonymized this subspecies with ''Basilosaurus kochii'' and ''Zeuglodon hydrachus'' (better known as "Dr Albert Koch's Hydrarchos", see ''Pontogeneus'') and half a dozen other combinations and placed them in the species ''Zygorhiza kochii''. named and described the species ''Zeuglodon wanklyni'' based on a skull that is friend Dr. Arthur Wanklyn had found in the Barton Clays in southern England. This skull, however, was never deposited at the British Museum of Natural History and has not been since Seeley described it. , nevertheless, recombined it as ''Zygorhiza wanklyni'' and referred a posterior cervical vertebra from the same location to it. Uhen 1998 declared it ''nomen nudum''.〔. Retrieved September 2013.〕 described an incomplete skull, four vertebrae, two teeth, and small fragments in early Bartonian sediments in New Zealand which they tentatively identified as ''Zygorhiza'' sp.. This is the oldest known Dorudontinae and the oldest known cetacean from the Southern Hemisphere In the U.S., ''Zygorhiza'' is known from the Gulf Coast, whilst ''Dorudon'' is known from southeastern Atlantic Coast. Outside North America, ''Zygorhiza'' has only been reliably identified in New Zealand, whereas ''Dorudon'' only in Egypt. It is possible that these non-overlapping distributions indicate differences in habitat preferences. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Zygorhiza」の詳細全文を読む スポンサード リンク
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