Plesiobalaenoptera
Encyclopedia
Plesiobalaenoptera is an extinct genus
of rorqual
whale
which existed in Italy
during the late Miocene
epoch. The type species
is P. quarantellii. It is the oldest known rorqual from the Mediterranean basin
. Fossils have been found from sediments of the Stirone River in northern Italy that were deposited during the Tortonian
age, around 11 to 7 million years ago.
than other whales. The genus has several distinguishing features mainly seen in the region of the ear. For example, the periotic bone
(which surrounds the inner ear
) has a raised central portion and a triangular projection at its front. Like all baleen whale
s, the tympanic bulla, which surrounds the middle ear
, is enlarged and separate from the periotic bone. However, its tympanic bulla has a distinctive high keel. Moreover, the opening of the Eustachian tube
into the middle ear is in a high position.
Unlike living rorquals, Plesiobalaenoptera was probably not capable of ram feeding. During ram feeding, modern whales swim toward their prey with open mouths and engulf them in an expandable throat. Plesiobalaenoptera has a postcoronoid
fossa, or hole in the dentary bone of the lower jaw, which would have made this method of feeding difficult to perform.
in the United States
. The two form a clade that is the sister taxon of crown
balaenopterids, which includes the last common ancestor of the living Balaenoptera
and Megaptera, and all of its descendants.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of rorqual
Rorqual
Rorquals are the largest group of baleen whales, with nine species in two genera. They include the largest animal that has ever lived, the Blue Whale, which can reach , and another that easily reaches ; even the smallest of the group, the Northern Minke Whale, reaches .-Characteristics:Rorquals...
whale
Whale
Whale is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti . This suborder also includes the sperm whale, killer whale, pilot whale, and beluga...
which existed in Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
during the late Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
epoch. The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
is P. quarantellii. It is the oldest known rorqual from the Mediterranean basin
Mediterranean Basin
In biogeography, the Mediterranean Basin refers to the lands around the Mediterranean Sea that have a Mediterranean climate, with mild, rainy winters and hot, dry summers, which supports characteristic Mediterranean forests, woodlands, and scrub vegetation...
. Fossils have been found from sediments of the Stirone River in northern Italy that were deposited during the Tortonian
Tortonian
The Tortonian is in the geologic timescale an age or stage of the late Miocene that spans the time between 11.608 ± 0.005 Ma and 7.246 ± 0.005 Ma . It follows the Serravallian and is followed by the Messinian....
age, around 11 to 7 million years ago.
Description
Plesiobalaenoptera was similar in appearance to other rorquals, although it had a relatively wider rostrumRostrum (anatomy)
The term rostrum is used for a number of unrelated structures in different groups of animals:*In crustaceans, the rostrum is the forward extension of the carapace in front of the eyes....
than other whales. The genus has several distinguishing features mainly seen in the region of the ear. For example, the periotic bone
Periotic bone
Periotic bone is the single bone that surrounds the ear of mammals. It is formed from the fusion of the pro-otic, epiotic, and opisthotic bones.- External links :* http://www.encyclopedia.com/doc/1O8-perioticbone.html...
(which surrounds the inner ear
Inner ear
The inner ear is the innermost part of the vertebrate ear. In mammals, it consists of the bony labyrinth, a hollow cavity in the temporal bone of the skull with a system of passages comprising two main functional parts:...
) has a raised central portion and a triangular projection at its front. Like all baleen whale
Baleen whale
The Baleen whales, also called whalebone whales or great whales, form the Mysticeti, one of two suborders of the Cetacea . Baleen whales are characterized by having baleen plates for filtering food from water, rather than having teeth. This distinguishes them from the other suborder of cetaceans,...
s, the tympanic bulla, which surrounds the middle ear
Middle ear
The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the cochlea. The mammalian middle ear contains three ossicles, which couple vibration of the eardrum into waves in the fluid and membranes of the inner ear. The hollow space of the middle ear has...
, is enlarged and separate from the periotic bone. However, its tympanic bulla has a distinctive high keel. Moreover, the opening of the Eustachian tube
Eustachian tube
The Eustachian tube is a tube that links the nasopharynx to the middle ear. It is a part of the middle ear. In adult humans the Eustachian tube is approximately 35 mm long. It is named after the sixteenth-century anatomist Bartolomeo Eustachi...
into the middle ear is in a high position.
Paleobiology
Coronoid process of the mandible
The mandible's coronoid process is a thin, triangular eminence, which is flattened from side to side and varies in shape and size....
fossa, or hole in the dentary bone of the lower jaw, which would have made this method of feeding difficult to perform.
Classification
Plesiobalaenoptera is closely related to Parabalaenoptera, known from the late Miocene of CaliforniaCalifornia
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. The two form a clade that is the sister taxon of crown
Crown group
A crown group is a group consisting of living representatives, their ancestors back to the most recent common ancestor of that group, and all of that ancestor's descendants. The name was given by Willi Hennig, the formulator of phylogenetic systematics, as a way of classifying living organisms...
balaenopterids, which includes the last common ancestor of the living Balaenoptera
Balaenoptera
Balaenoptera is a genus of Balaenopteridae, the Rorqual whales, and contains eight species. The species Balaenoptera omurai was published in 2003...
and Megaptera, and all of its descendants.