''Pontogeneus'' (''

nomen dubium In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium,'' it may be impossible to determine whether a ...

'') is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of extinct

cetacea Cetacea (; , ) is an infraorder of aquatic mammals belonging to the order Artiodactyla that includes whales, dolphins and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively c ...

n known from

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

s recovered from the

Late Eocene The Priabonian is, in the International Commission on Stratigraphy, ICS's geologic timescale, the latest age (geology), age or the upper stage (stratigraphy), stage of the Eocene epoch (geology), Epoch or series (stratigraphy), Series. It spans ...

sediments (Bartonian-Priabonian stages) of the southeastern United States (most notably

Alabama Alabama ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South, Deep Southern regions of the United States. It borders Tennessee to the north, Georgia (U.S. state), Georgia to the east, Florida and the Gu ...

and Florida).

Classification

When ''"Zeuglodon" brachyspondylus'' was formerly included, ''Pontogeneus'' was depicted as having a skeleton similar to that of '' Basilosaurus cetoides'', although the posterior thoracic

vertebrae Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal ...

, the lumbar vertebrae, and the anterior caudal vertebrae had proportions closer to those seen in members of the archaeocete

Subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zo ...

Dorudontinae Dorudontinae are a group of extinct cetaceans that are related to ''Basilosaurus''.. Retrieved July 2013. Classification * Subfamily Dorudontinae ** Genus ''Ancalecetus'' *** ''Ancalecetus simonsi'' ** Genus ''Chrysocetus'' *** ''Chrysocetus f ...

Taxonomic history

In 1852,

Joseph Leidy Joseph Mellick Leidy (September 9, 1823 – April 30, 1891) was an American paleontologist, parasitologist and anatomist. Leidy was professor of anatomy at the University of Pennsylvania, later becoming a professor of natural history at Swarth ...

had erected ''Pontogeneus priscus'' based on the centrum of a single cervical vertebra in the collections of the

Academy of Natural Sciences The Academy of Natural Sciences of Drexel University, formerly the Academy of Natural Sciences of Philadelphia, is the oldest natural science research institution and museum in the Americas. It was founded in 1812, by many of the leading natur ...

Philadelphia Philadelphia ( ), colloquially referred to as Philly, is the List of municipalities in Pennsylvania, most populous city in the U.S. state of Pennsylvania and the List of United States cities by population, sixth-most populous city in the Unit ...

. Leidy noted that the centrum had been collected from exposures along the Washita River in

Louisiana Louisiana ( ; ; ) is a state in the Deep South and South Central regions of the United States. It borders Texas to the west, Arkansas to the north, and Mississippi to the east. Of the 50 U.S. states, it ranks 31st in area and 25 ...

. synonymized these two taxa to form ''Pontogeneus brachyspondylus'' which he listed as ''

incertae sedis or is a term used for a taxonomy (biology), taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty ...

''. designated ''Pontogeneus priscus'' and ''Zeuglodon brachyspondylus'' to be ''nomina dubia'' based on the lack of diagnostic characters that distinguish the type specimens from other basilosaurids. While ''Pontogeneus priscus'' is no longer considered valid, "Z." brachyspondylus appears similar to ''

Masracetus ''Masracetus'' (from Arabic ''Masr'', "Egypt", and Greek ''ketos'', "whale") is an extinct genus of basilosaurid ancient whale known from the Late Eocene (Priabonian, ) of Egypt. ''Masracetus'' was briefly described in an addendum by and is ...

'' from

Egypt Egypt ( , ), officially the Arab Republic of Egypt, is a country spanning the Northeast Africa, northeast corner of Africa and Western Asia, southwest corner of Asia via the Sinai Peninsula. It is bordered by the Mediterranean Sea to northe ...

(which was also referred to ''Z. brachyspondylus'' in the past) and may represent either a species of ''Masracetus'' or a distinct and closely related but as-yet-unnamed genus.Gingerich, Philip D (2007). "Stromerius nidensis, new archaeocete (Mammalia, Cetacea) from the Upper Eocene Qasr El-Sagha Formation, Fayum, Egypt". Contributions from the Museum of Paleontology 31 (13): 363–78. OCLC 214233870.

Formerly assigned to ''Pontogeneus''

''"Zeuglodon brachyspondylus"'' () was erected for several vertebrae collected in either Choctaw or Washington counties in southern Alabama. Basilosaurid remains from Egypt were tentatively assigned to ''Zeuglodon brachyspondylus'' based on superficial similarities to the syntype series (under the old hypothesis of synonymy of ''Pontogeneus'' and ''Zeuglodon brachyspondylus''). Stromer, Ernst, 1908. Die Archaeoceti des ägyptischen Eozäns. Beiträge zur Paläontologie und Geologie Österreich-Ungarns und des Orients, Vienna, 21: 106-178. However, these remains were given their own genus, ''Masracetus'', given minor differences from "Z." ''brachyspondylus''.

Notes

References

* * * * * * {{Taxonbar, from=Q9061700 Basilosauridae Eocene cetaceans Archaeoceti Eocene mammals of North America Monotypic prehistoric cetacean genera Nomina dubia