A new specimen ofAgorophius pygmaeus(Agorophiidae, Odontoceti, Cetacea) from the early Oligocene Ashley Formation of South Carolina, USA

Abstract

The holotype partial skull of Agorophius pygmaeus (the monotypic form for both the genus Agorophius and the Family Agorophiidae) has been missing for approximately 140 years. Since the discovery of Agorophius pygmaeus, many additional taxa and specimens have been placed in the Family Agorophiidae, only to be reclassified and removed later. This has created confusion as to what is and what is not an agorophiid and a lack of clarity as to what characteristics delimit the Agorophiidae. A newly discovered skull of an agorophiid recently collected from an underwater cliff face of the Ashley River, South Carolina, USA, is assigned to Agorophius pygmaeus. It derives from the base of the Ashley Formation (early Oligocene). The new specimen consists of most of the skull and periotics, which are well preserved and described for the first time in an agorophiid. The new specimen provides an opportunity to diagnose the Agorophiidae and place the genus and species within the phylogenetic context of the early odontocete radiation in the Oligocene, along with other taxa such as the Ashleycetidae, Mirocetidae, Patriocetidae, Simocetidae, Waipatiidae, and Xenorophidae. Based on this new understanding, Agorophiidae are known with certainty only from the early Oligocene of South Carolina, with other undescribed, potential agorophiid specimens from the Oligocene of the North Pacific region (Japan, Mexico, and Washington State).

Evolution of cranial telescoping in echolocating whales (Cetacea: Odontoceti)

“…; Godfrey et al. ; Uhen ). Xenorophids are a relatively diverse clade of Oligocene whales known only from South and North Carolina (Uhen ), with many taxa yet to be described (Sanders and Geisler ).…”

“…; Godfrey et al. ). While not included within our morphometric analysis, Archaeodelphis is notable for having minimal development of the ascending process of the maxillae (Allen ), unlike other xenorophids (Geisler et al.…”

Oligocene cetaceans from Baja California Sur, Mexico

“…MU EcSj5/12/48 was earlier referred to as "Agorophius" sp. (Cruz-Marín, 1997), but its morphology is quite different to Agorophiidae (Fordyce, 1981, Godfrey et al, 2016 and closer to Simocetus rayi Fordyce, 2002. Amongst features of note, the specimen is small compared with both S. rayi (condylobasal length: 449+ mm; bizygomatic width: ~238 mm, Fordyce, 2002) and Agorophius pygmaeus (Müller, 1849) (condylobasal length: ~450-500 mm; bizygomatic width: ~200+ mm).…”

“…In contrast, sediments of El Cien Formation were deposited no deeper than 200 m, suggesting shelf environments, coastal lagoons, estuaries and deltas (Schwennicke, 1994). Past studies of diatoms (Kim and Barron, 1986), planktonic foraminifera (Kim, 1987), and calcareous nannofossils Schwennicke, 1992), shark and ray faunas (González-Barba, 2008), macroinvertebrates -e.g. mollusks and crabs (Smith, 1991;Grimm and Föllmi, 1994;Schweitzer et al, 2002;Vera-Dimas, 2013), phosphorites (Galli-Olivier et al, 1990;Galli-Olivier, 1993;Schwennicke, 1994;Schwennicke and Vázquez-García, 1996), and sedimentological studies (Grimm, 1992) have elucidated the paleobiological and paleoceanographic history of the region during the Late Oligocene and indicate a subtropical environment characterized by high primary productivity.…”

“…However, it is known that the distribution of fossils is broader, with abundant material in places like El Aguajito, El Cien, Cerro Colorado, Tembabichi (Tembabichi Member, El Cien Formation) and La Purísima (San Gregorio Formation). Since the 2000s more cetacean fossils have been collected from the Oligocene outcrops in Baja California Sur, leading to recent published mentions and some provisional identification (González-Barba, 2007;Hernández-Cisneros and González-Barba, 2013). In summary, the fossil record is diverse at species to family level, but identifications are provisional because most of the specimens need detailed preparation, and the specimens are largely unpublished.…”