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''Zygophyseter'' had 28 teeth in the lower jaws and 26 in the upper jaws.[ The curvature of the teeth increased [[Anatomical terms of location#Medial and lateral|medially]], that is, the teeth in the front of the mouth were straighter than the teeth in the back of the mouth. The back teeth featured more wear than the front teeth. Like ''Brygmophyseter'', it had a relatively small [[crown (tooth)|crown]], making up only 18% of the tooth. [[Killer whale]]s (''Orcinus orca''), in comparison, have crowns that make up 20–25% of the tooth. Other characteristics include the presence of the [[gumline]] below the crown-root boundary (meaning that part of the root was exposed), and longitudinal grooves on the root. In the [[type specimen]], the teeth ranged in height from {{convert|150|to|250|mm|sp=us}} with an average height of {{cvt|175.6|mm}}, and ranged in diameter from {{cvt|47|to|56|mm}} with an average of {{cvt|52.4|mm}}. Like in other raptorials, and unlike in the modern sperm whale, ''Zygophyseter'' had tooth enamel.][{{cite journal |last1=Toscano |first1=Antonio |last2=Abad |first2=Manuel |last3=Ruiz |first3=Francisco |last4=Muñiz |first4=Fernando |last5=Álvarez |first5=Genaro |last6=García |first6=Edith Xio-Mara |last7=Caro |first7=José Antonio |name-list-style=and |year=2013 |title=Nuevos restos de ''Scaldicetus'' (Cetacea, Odontoceti, Physeteridae) del Mioceno superior, sector occidental de la Cuenca del Guadalquivir (sur de España) |trans-title=New remains of ''Scaldicetus'' (Cetacea, Odontoceti, Physeteridae) from the Upper Miocene, western sector of the Guadalquivir basin (southern Spain) |url=https://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1026-87742013000200013 |journal=Revista Mexicana de Ciencias Geológicas |language=es |volume=30 |pages=436–445 |number=2}}][{{cite journal |last=Fitzgerald |first=Erich M. G. |year=2011 |title=A Fossil Sperm Whale (Cetacea, Physeteroidea) from the Pleistocene of Nauru, Equatorial Southwest Pacific |journal=Journal of Vertebrate Paleontology |volume=31 |issue=4 |pages=929–931 |bibcode=2011JVPal..31..929F |doi=10.1080/02724634.2011.579670 |jstor=25835890 |s2cid=86528408}}] Like in ''Acrophyseter'', the [[mandibular foramen]] takes up about 40% of the lower jawbone. The teeth of the upper jaw form an angle of nearly 120 degrees between the crown and the root, which is possibly a characteristic shared by all raptorials. |
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''Zygophyseter'' had 28 teeth in the lower jaws and 26 in the upper jaws.[ The curvature of the teeth increased [[Anatomical terms of location#Medial and lateral|medially]], that is, the teeth in the front of the mouth were straighter than the teeth in the back of the mouth. The back teeth featured more wear than the front teeth. Like ''Brygmophyseter'', it had a relatively small [[crown (tooth)|crown]], making up only 18% of the tooth. [[Killer whale]]s (''Orcinus orca''), in comparison, have crowns that make up 20–25% of the tooth. Other characteristics include the presence of the [[gumline]] below the crown-root boundary (meaning that part of the root was exposed), and longitudinal grooves on the root. In the [[type specimen]], the teeth ranged in height from {{convert|150|to|250|mm|sp=us}} with an average height of {{cvt|175.6|mm}}, and ranged in diameter from {{cvt|47|to|56|mm}} with an average of {{cvt|52.4|mm}}. Like in other raptorials, and unlike in the modern sperm whale, ''Zygophyseter'' had tooth enamel.][{{cite journal |last1=Toscano |first1=Antonio |last2=Abad |first2=Manuel |last3=Ruiz |first3=Francisco |last4=Muñiz |first4=Fernando |last5=Álvarez |first5=Genaro |last6=García |first6=Edith Xio-Mara |last7=Caro |first7=José Antonio |name-list-style=and |year=2013 |title=Nuevos restos de ''Scaldicetus'' (Cetacea, Odontoceti, Physeteridae) del Mioceno superior, sector occidental de la Cuenca del Guadalquivir (sur de España) |trans-title=New remains of ''Scaldicetus'' (Cetacea, Odontoceti, Physeteridae) from the Upper Miocene, western sector of the Guadalquivir basin (southern Spain) |url=https://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1026-87742013000200013 |journal=Revista Mexicana de Ciencias Geológicas |language=es |volume=30 |pages=436–445 |number=2}}][{{cite journal |last=Fitzgerald |first=Erich M. G. |year=2011 |title=A Fossil Sperm Whale (Cetacea, Physeteroidea) from the Pleistocene of Nauru, Equatorial Southwest Pacific |journal=Journal of Vertebrate Paleontology |volume=31 |issue=4 |pages=929–931 |bibcode=2011JVPal..31..929F |doi=10.1080/02724634.2011.579670 |jstor=25835890 |s2cid=86528408}}] Like in ''Acrophyseter'', the [[mandibular foramen]] takes up about 40% of the lower jawbone. The teeth of the upper jaw form an angle of nearly 120 degrees between the crown and the root, which is possibly a characteristic shared by all raptorials. |
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''Zygophyseter'' could reach an estimated length of {{convert|6.5|to|7|m|sp=us}}, compared to the {{convert|12.5|to|18.5|m|adj=on|sp=us}} modern sperm whale.[ It is thought that this whale had twelve [[thoracic vertebrae]] and at least ten [[lumbar vertebra]]e. The type specimen had only 8 thoracic vertebrae preserved, and only the [[atlas (anatomy)|atlas]] of the [[neck vertebra]]e. Like in the modern sperm whales, the neck [[vertebra]]e may have been fused. The [[Body of vertebra|centrum]] of the thoracic vertebrae formed a large and almost pear-shaped [[central canal]] which transports nutrients to the [[spinal cord]]. The width between the transverse processes (the diagonal projections from a vertebral centrum) of the thoracic vertebrae were {{convert|235|mm|sp=us}}; and the neural spine, the part of the spine that projects away from the centrum, is missing in the type specimen, but it was probably short and thin. The lumbar vertebrae were elongated and may have supported large [[multifidus muscle|multifidus]] and [[longissimus]] muscles in the back, likely larger than the modern sperm whale, and so it probably swam faster than the modern sperm whale;][{{cite book |last=Whitehead |first=Hal |url={{google books|plainurl=yes|id=sq5C8d1hzPgC|page=104}} |title=Sperm Whales: Social Evolution in the Ocean |publisher=University of Chicago Press |year=2003 |isbn=978-0-226-89517-8 |pages=104–110}}] The type specimen had eight [[Vertebra#Other animals|caudal vertebrae]] in the tail. |
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''Zygophyseter'' was holotype about {{convert|6.5|-|7|m|sp=us}} long. It was much smaller than modern male [[sperm whale]], which reach {{convert|16|-|20|m|sp=us}} in length, and was similar in length to [[orca]].[ It is thought that this whale had twelve [[thoracic vertebrae]] and at least ten [[lumbar vertebra]]e. The type specimen had only 8 thoracic vertebrae preserved, and only the [[atlas (anatomy)|atlas]] of the [[neck vertebra]]e. Like in the modern sperm whales, the neck [[vertebra]]e may have been fused. The [[Body of vertebra|centrum]] of the thoracic vertebrae formed a large and almost pear-shaped [[central canal]] which transports nutrients to the [[spinal cord]]. The width between the transverse processes (the diagonal projections from a vertebral centrum) of the thoracic vertebrae were {{convert|235|mm|sp=us}}; and the neural spine, the part of the spine that projects away from the centrum, is missing in the type specimen, but it was probably short and thin. The lumbar vertebrae were elongated and may have supported large [[multifidus muscle|multifidus]] and [[longissimus]] muscles in the back, likely larger than the modern sperm whale, and so it probably swam faster than the modern sperm whale;][{{cite book |last=Whitehead |first=Hal |url={{google books|plainurl=yes|id=sq5C8d1hzPgC|page=104}} |title=Sperm Whales: Social Evolution in the Ocean |publisher=University of Chicago Press |year=2003 |isbn=978-0-226-89517-8 |pages=104–110}}] The type specimen had eight [[Vertebra#Other animals|caudal vertebrae]] in the tail. |
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The animal probably had 12 ribs. The length of the ribs increased from the first to the fifth, then decreased from the fifth to the twelfth; and the width of the ribs decreased from the first to the twelfth, similar to other [[cetacea]]ns.[{{cite journal |last1=Lambert |first1=Olivier |last2=Bianucci |first2=Giovanni |last3=de Muizon |first3=Christian |year=2008 |title=A new stem-sperm whale (Cetacea, Odontoceti, Physeteroidea) from the Latest Miocene of Peru |url=https://www.researchgate.net/publication/237950259 |journal=Comptes Rendus Palevol |volume=7 |issue=6 |pages=361–369 |bibcode=2008CRPal...7..361L |doi=10.1016/j.crpv.2008.06.002 |s2cid=85723286}}] |
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The animal probably had 12 ribs. The length of the ribs increased from the first to the fifth, then decreased from the fifth to the twelfth; and the width of the ribs decreased from the first to the twelfth, similar to other [[cetacea]]ns.[{{cite journal |last1=Lambert |first1=Olivier |last2=Bianucci |first2=Giovanni |last3=de Muizon |first3=Christian |year=2008 |title=A new stem-sperm whale (Cetacea, Odontoceti, Physeteroidea) from the Latest Miocene of Peru |url=https://www.researchgate.net/publication/237950259 |journal=Comptes Rendus Palevol |volume=7 |issue=6 |pages=361–369 |bibcode=2008CRPal...7..361L |doi=10.1016/j.crpv.2008.06.002 |s2cid=85723286}}] |
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