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Agorophius pygmaeus

Mammalia - Artiodactyla - Agorophiidae

Agorophius pygmaeum was named by Muller (1849). Its type specimen is MCZ 8761, a skull, and it is a 3D body fossil. Its type locality is Greer's Landing, which is in a Rupelian marine sandstone in the Ashley Formation of South Carolina.

Synonymy list
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phylumChordataHaeckel 1847
subclassDipnotetrapodomorpha(Nelson 2006)

If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.

S. Godfrey et al. 2016Cetacean with key odontocete synapomorphy of an ascending process of maxilla that is expanded posteriorly and laterally to overlap dorsal surface of supraorbital process of frontal (Barnes, 1990; Fordyce, 1994; Geisler and Sanders, 2003; Heyning, 1989; Messenger and McGuire, 1998; Miller, 1923; Uhen, 2010). Odontocete in which an intertemporal constriction is present. An intertemporal constriction is a con- dition in which the parietals and interparietal broadly separate the face from supraoccipital (Mead and Fordyce, 2009). This differentiates Ashleycetidae, Mirocetidae, Xenorophidae, Simocetidae, and Agorophiidae from the clade of odontocetes including Patriocetidae and more derived odontocetes, which all lack an intertemporal constriction.
Among the basal odontocetes that possess an intertemporal constriction, Agorophius pygmaeus has a premaxillary sac fossa that lies mostly anterior to its antorbital notch but approximately one quarter of its length does reach posterior to the level of the notch (premaxillary sac fossa anterior to antorbital notch in Xenorophidae and Simocetidae, mostly posterior to antorbital notch in Waipatiidae); premaxillary cleft is deeply imbedded in the body of the bone immediately anterior to sigmoid curve of the posteroexternal plate (no cleft in Xenorophidae, pre- maxillary cleft presents as a shallow groove in Simocetidae and Waipatiidae); sigmoid curve of the posteroexternal plate lies opposite the middle of the length of the orbit (level to posterior margin of orbit in Xenorophidae [if present at all], absent in Simocetidae, well posterior to orbit in Waipatiidae); external nares open approximately at the level of the antorbital notch (behind notch in Xenorophidae, ahead of notch in Simocetidae, well posterior notch in Waipatiidae); single posterior dorsal infraorbital foramen in each maxilla at about the midpoint in the length of the orbit (absent in Xenorophidae, two per maxilla present in Simocetidae at midpoint in orbit length, two present [i.e., maxillary foramina] posterior to orbit in Waipatiidae); posterior margin of maxilla extends posterior to premaxilla but not posterior to postorbital process of frontal (premaxilla extends further posterior in Xenorophidae, maxilla extends further posterior to both premaxilla and postorbital process of frontal in Simocetidae and Waipatiidae); multiple supraorbital foramina in frontals between posteromedial margins of premaxilla (no such foramina in Xenorophidae or Waipatiidae, present in Simocetidae); parietals contribute to the dorsal intertemporal region of the skull without the presence of a sagittal crest (i.e., between the posterior margin of the frontals and the anterior margin of the supraoccipital), (sagittal crest present in Xenorophidae, absent in Simocetidae, no possibility of a parietal crest in Waipatiidae because parietals excluded from skull roof); in dorsal view, supraoccipital thrust forward anterior to line running from the angle formed by the zygomatic process of the squamosal within the temporal fossa to the other (apex of supraoccipital behind level of zygomatic angle in Xenorophidae, Simocetidae, and Waipatiidae); in lateral view, skull presents a horizontal profile (tabular dorsally) between the nasofrontal suture and the anterior margin of the supraoccipital; width of the skull at the level of the temporal fossae nearly twice as wide as deep.

The single known buccal tooth (following the terminology of Rothausen (1968) can be used to differentiate Agorophius pygmaeus from almost all other Oligocene taxa for which teeth are known. Most Oligocene Odontoceti that have buccal teeth with two roots have crowns that are much lower than Agorophius (Cotylocara, Patriocetus, Prosqualodon, Simocetus, Squalodon, Waipatia, Xenorophus), have too few denticles (Cotylocara, Saurocetus, Prosqualodon), too many denticles (Squalodon, Metasqualodon), or some combination thereof. The one taxon that has quite similar cheek teeth is Squalodon (Microzeuglodon) wingei (Ravn, 1926), which also has very high-crowned teeth similar to those of Agorophius pygmaeus, suggesting that this taxon may also represent an agorophiid, which are otherwise unknown from Europe.