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Zygorhiza Whale Molar Fossil measures 4.1 inches. Zygorhiza Whale Molar Fossil is a museum quality polyurethane cast. Made in USA. Zygorhiza kochii is the scientific name. Our precise Molar can be used as a teaching tool, museum molar exhibit, home decor molar, or office decor molar.
Zygorhiza Whale or Zygorhiza kochii is an extinct genus of basilosaurid early whale known from the Late Eocene of Louisiana, Alabama, and Mississippi, United States, and the Bortonian to the late Eocene of New Zealand (43 to 33.9 million years ago).
Zygorhiza kochii had a body similar in cetaceans with flipper-like forelimbs, rudimentary hind limbs, a vertebral column adapted for oscillatory swimming, and a tail fluke. The Basilosaurus replaced their upper and lower deciduous first premolars with permanent teeth. This is very unusual in modern mammals and contrasts to extant toothed whales that only develop a single set of teeth.
It might indicate that Zygorhiza Whale or Zygorhiza kochii represents a stage in archaeocete evolution where skeletal maturation was delayed like in modern cetaceans. Zygorhiza Whales differs from all other dorudontines in the presence of well-developed cuspules on the cingula of the upper premolars.
In the U.S., Zygorhiza Whale or Zygorhiza kochii 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.
Zygorhiza kochii skull is elongated with a narrow rostrum and a flattened forehead; the premaxillae are laterally convex. The high sagittal crest is flanked by two large temporal fossae, resulting in a narrow intertemporal region.
The Zygorhiza Whale or Zygorhiza kochii hyoid apparatus consists of a small, central, and hexagonal basihyoid bone. From this bone project a pair of thyrohyoid bones (homologous with the greater cornua in humans) that are slightly expanded anteriorly and tapper off posteriorly, and another pair of slender and elongated bones, the epihyoid and stylohyoid bones.
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