Remingtonocetidae is a diverse

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

of early

aquatic Aquatic means relating to water; living in or near water or taking place in water; does not include groundwater, as "aquatic" implies an environment where plants and animals live. Aquatic(s) may also refer to: * Aquatic animal, either vertebrate ...

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

s of the

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

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 ...

. The family is named after paleocetologist

Remington Kellogg Arthur Remington Kellogg (5 October 1892 – 8 May 1969) was an American naturalist and a director of the United States National Museum. His work focused on marine mammals. Early life and career Kellogg was born in Davenport, Iowa, and quickly ...

Description

Remingtonocetids have long and narrow skulls with the external

nare Nare may refer to: People * Daniel Nare, Botswanan football manager * Tadu Teshome Nare (born 2001), Ethiopian runner * Théophile Naré (born 1966), Catholic bishop of Kaya, Burkina Faso Other meanings * Nareh (given name) (or Nare, Nara), Armeni ...

openings located on the front of the skull. Their

frontal shield A frontal shield, also known as a facial shield or frontal plate, is a feature of the anatomy of several bird species. Located just above the upper mandible, and protruding along the forehead, it is composed of two main parts: a hard, proteinaceo ...

s are narrow and their orbits small. Their mouth has a convex

palate The palate () is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but in most other tetrapods, the oral and nasal cavities are not truly sep ...

and an incompletely fused

mandibular symphysis In human anatomy, the facial skeleton of the skull the external surface of the mandible is marked in the median line by a faint ridge, indicating the mandibular symphysis (Latin: ''symphysis menti'') or line of junction where the two lateral ha ...

. The dental formula is . The anterior teeth are flattened mediolaterally, making them appear shark-like. In the

postcrania The postcranium ("behind the cranium"; plural: postcrania) or postcranial skeleton in zoology and vertebrate paleontology is the skeleton apart from the skull. The postcranium encompasses the axial skeleton, which includes the entirety of the verte ...

l skeleton, the

cervical vertebrae In tetrapods, cervical vertebrae (: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In saurop ...

are relatively long and the

sacrum The sacrum (: sacra or sacrums), in human anatomy, is a triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30. The sacrum situates at the upper, back part of the pelvic cavity, ...

is composed of four vertebrae of which at least three are fused. The

acetabular notch The acetabular notch is a deep notch in the inferior portion of the rim of the acetabulum The acetabulum (; : acetabula), also called the cotyloid cavity, is a wikt:concave, concave surface of the pelvis. The femur head, head of the femur mee ...

is narrow or closed and on the

femoral head The femoral head (femur head or head of the femur) is the highest part of the thigh bone (femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the ...

the

fovea Fovea () (Latin for "pit"; plural foveae ) is a term in anatomy. It refers to a pit or depression in a structure. Human anatomy *Fovea centralis of the retina * Fovea buccalis or dimple * Fovea of the femoral head * Trochlear fovea of the fr ...

is absent. Kutchicetus minimus

Cranial fossils are common but dental remains are rare. The postcrania morphology is based entirely on a single specimen of ''

Kutchicetus ''Kutchicetus'' is an extinct genus of early whale of the family Remingtonocetidae that lived during Early-Middle Eocene (Lutetian and Ypresian) in what is now the coastal border of Pakistan and India (, paleocoordinates ). It is closely relat ...

'' which was small and had a long and muscular back and tail. Perhaps remintonocetids swam like the South American

giant otter The giant otter or giant river otter (''Pteronura brasiliensis'') is a South American carnivorous mammal. It is the longest member of the weasel family, Mustelidae, a globally successful group of predators, reaching up to . Atypical of mustel ...

which swims with its long flat tail. With long and low bodies, relatively short limbs, their elongated

rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit ** podium * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ...

, remingtonocetids looked like mammalian crocodiles, more so than ''

Ambulocetus ''Ambulocetus'' (Latin ''ambulare'' "to walk" + ''cetus'' "whale") is a genus of early Semiaquatic, amphibious cetacean from the Kuldana Formation in Pakistan, roughly 48 or 47 million years ago during the Early Eocene (Lutetian). It contains o ...

''. They could both walk on land and swim in the water and most likely lived in a near-shore habitat. At least one genus, ''

Dalanistes ''Dalanistes'' is an extinct genus of Remingtonocetidae, remingtonocetid Archaeoceti, early whale known from the late-early Eocene (Lutetian, ) of Kutch, India and Punjab, Pakistan, Punjab and Balochistan, Pakistan. ''Dalanistes'' is closely re ...

'', had a marine diet. Remingtonocetids are often found in association with catfish and crocodilians, as well as

protocetid Protocetidae, the protocetids, form a paraphyletic, diverse and heterogeneous group of extinct cetaceans known from Asia, Europe, Africa, South America, and North America. Description There were many genera, and some of these are very well kno ...

whales and

sirenia The Sirenia (), commonly referred to as sea cows or sirenians, are an order of fully aquatic, herbivorous mammals that inhabit swamps, rivers, estuaries, marine wetlands, and coastal marine waters. The extant Sirenia comprise two distinct famili ...

ns. They were probably independent of freshwater.

Distribution

Remingtonocetidae was long considered endemic to the northern coastline of the ancient

Tethys Ocean The Tethys Ocean ( ; ), also called the Tethys Sea or the Neo-Tethys, was a prehistoric ocean during much of the Mesozoic Era and early-mid Cenozoic Era. It was the predecessor to the modern Indian Ocean, the Mediterranean Sea, and the Eurasia ...

(in present day Pakistan and India) during the

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

, but the discovery of ''

Rayanistes ''Rayanistes'' is a genus of remingtonocetid whale from the Middle Eocene deposits in Egypt. Significance and biology ''Rayanistes'' was capable of extensive power strokes during pelvic paddling, based on the robust hindlimb and innominate. Th ...

'' in Egypt indicates that remingtonocetids had a broader distribution than previously thought. A single tooth recovered from the

Castle Hayne Limestone The Castle Hayne Limestone (also called the Castle Hayne Formation) is a middle Eocene-aged Formation (geology), geologic formation in North Carolina, USA. It consists of cobble to pebble sized clastic rocks, clasts, usually rounded, coated with ...

North Carolina North Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, South Carolina to the south, Georgia (U.S. stat ...

, USA closely resembles that of remingtonocetids; if it belongs to one, it indicates that they may have been found as far west as eastern North America, expanding their distribution across the

Atlantic The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for se ...

Taxonomy

Remingtonocetidae was established by . It was considered

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

by . It was assigned to

Odontoceti The toothed whales (also called odontocetes, systematic name Odontoceti) are a parvorder of cetaceans that includes dolphins, porpoises, and all other whales with teeth, such as beaked whales and the sperm whales. 73 species of toothed whales ar ...

by ; to Remingtonocetoidea by and ; to

Archaeoceti Archaeoceti ("ancient whales"), or Zeuglodontes in older literature, is an obsolete paraphyletic group of primitive cetaceans that lived from the Early Eocene to the late Oligocene (). Representing the earliest cetacean radiation, they include th ...

by ; to Archaeoceti by , , , , , , , and and to Cetacea by , and .. Retrieved February 2013 The name of the family was derived from the

type genus In biological taxonomy, the type genus (''genus typica'') is the genus which defines a biological family and the root of the family name. Zoological nomenclature According to the International Code of Zoological Nomenclature, "The name-bearin ...

''Remingtonocetus'', which was named after paleocetologist

. In 2009, paleontologists Thewissen & Bajpai proposed the subfamily

Andrewsiphiinae The Andrewsiphiinae is an extinct subfamily of early whales of the family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relations ...

for the genera ''

Andrewsiphius ''Andrewsiphius'' is an extinct remingtonocetid early whale known from the Eocene (Lutetian, ) of Gujarat and Kutch, India and Balochistan, Pakistan. Discovery and naming The first specimen was collected by who described it as mandibular fr ...

'' and ''

''.

Genera

*''

Remingtonocetus ''Remingtonocetus'' is an extinct genus of early cetacean freshwater aquatic mammals of the family (biology), family Remingtonocetidae endemic to the coastline of the ancient Tethys Ocean during the Eocene. It was named after naturalist Remington ...

'' (type) *''

'' *''

Attockicetus ''Attockicetus'' is an extinct genus of remingtonocetid early whale known from the Middle Eocene (Lutetian) Kuldana Formation in the Kala Chitta Hills, in the Attock District of Punjab, Pakistan. ''Attockicetus'' is described based on fragmen ...

'' , the oldest genus *''

'' *''

'' Bebej, Zalmout, El-Aziz, Antar, and Gingerich, 2016

Notes

References