family
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
of
baleen whale
Baleen whales ( systematic name Mysticeti), also known as whalebone whales, are a parvorder of carnivorous marine mammals of the infraorder Cetacea ( whales, dolphins and porpoises) which use keratinaceous baleen plates (or "whalebone") in t ...
(Parvorder
Mysticeti
Baleen whales ( systematic name Mysticeti), also known as whalebone whales, are a parvorder of carnivorous marine mammals of the infraorder Cetacea (whales, dolphins and porpoises) which use keratinaceous baleen plates (or "whalebone") in the ...
) with a single extant species, the
gray whale
The gray whale (''Eschrichtius robustus''), also known as the grey whale,Britannica Micro.: v. IV, p. 693. gray back whale, Pacific gray whale, Korean gray whale, or California gray whale, is a baleen whale that migrates between feeding and bre ...
Miocene
The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...
and
Pliocene
The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Gricetoides'' from the Pliocene of North Carolina. More recent phylogenetic studies have found this family to be invalid, with its members nesting inside the Balaenopteridae. The names of the extant genus and the family honours Danish zoologist Daniel Eschricht.
Taxonomy
In his morphological analysis, found that eschrichtiids and
Cetotheriidae
Cetotheriidae is a family of baleen whales (parvorder Mysticeti). The family is known to have existed from the Late Oligocene to the Early Pleistocene before going extinct. Although some phylogenetic studies conducted by recovered the li ...
Mixocetus
''Mixocetus'' is a genus of extinct baleen whale belonging to the family Tranatocetidae. It is known only from the late Miocene (Tortonian) of Los Angeles County, California.
Description
''Mixocetus'' is a large-size mysticete with a long, nar ...
'' and ''
Metopocetus
''Metopocetus'' is an extinct genus of baleen whale belonging to the family Cetotheriidae. The type species is ''Metopocetus durinasus''.
Description
''Metopocetus'' is diagnosable by lateral occipital crests continuous with temporal crests tha ...
'') form a monophyletic sister group of Balaenopteridae.
A specimen from the
Late Pliocene
Late may refer to:
* LATE, an acronym which could stand for:
** Limbic-predominant age-related TDP-43 encephalopathy, a proposed form of dementia
** Local-authority trading enterprise, a New Zealand business law
** Local average treatment effe ...
of northern Italy, named ''" Cetotherium" gastaldii'' by and renamed ''"Balaenoptera" gastaldii'' by , was identified as a basal eschrichtiid by who recombined it to '' Eschrichtioides gastaldii''.
found that the gray whale is phylogenetically distinct from rorquals and that previous morphological studies were correct in the conclusion that the evolution of gulp feeding was a single event in the rorqual lineage. In contrast, multiple later studies found the gray whale to fall within the family Balaenopteridae, being more derived than the minke whales but basal to all other members in the family, and reclassified it in Balaenopteridae; the American Society of Mammalogists has followed this classification.
Evolution
Fossils of Eschrichtiidae have been found in all major oceanic basins in the Northern Hemisphere, and the family is believed date back to the Late Miocene. Today, gray whales are only present in the northern Pacific, but a population was also present in the northern Atlantic before being driven to extinction by European whalers three centuries ago.
Fossil eschrichtiids from before the Holocene are rare compared to other fossil mysticetes. The only Pleistocene fossil from the Pacific referred to ''E. eschrichtius'' is a partial skeleton and an associated skull from California, estimated to be about 200 thousand years old. However, a late Pliocene fossil from
Hokkaido
is Japan, Japan's Japanese archipelago, second largest island and comprises the largest and northernmost Prefectures of Japan, prefecture, making up its own List of regions of Japan, region. The Tsugaru Strait separates Hokkaidō from Honshu; th ...
, Japan, referred to ''Eschrichtius'' sp. is estimated to be and a similar unnamed fossil has been reported from California.
In their description of ''Archaeschrichtius ruggieroi'' from the late Miocene of Italy, argued that eschrichtiids most likely originated in the
Mediterranean Basin
In biogeography, the Mediterranean Basin (; also known as the Mediterranean Region or sometimes Mediterranea) is the region of lands around the Mediterranean Sea that have mostly a Mediterranean climate, with mild to cool, rainy winters and wa ...
about and remained there, either permanently or intermittently, at least until the
Early Pliocene
Early may refer to:
History
* The beginning or oldest part of a defined historical period, as opposed to middle or late periods, e.g.:
** Early Christianity
** Early modern Europe
Places in the United States
* Early, Iowa
* Early, Texas
* ...