Morenocetus

Morenocetus is an extinct genus of primitive balaenid from the Early Micoene (Burdigalian and Colhuehuapian in the SALMA classification) Gaiman Formation of Patagonia, Argentina.

Morenocetus
Temporal range: Early Miocene (Colhuehuapian)
~20–16 Ma
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Infraorder: Cetacea
Family: Balaenidae
Genus: Morenocetus
Cabrera 1926
Species

M. parvus Cabrera 1926 (type)

Description

Morenocetus is distinguished from more derived balaenids in the narrow exposure of the squamosal lateral to the exoccipital, a short supraorbital process of the frontal, straight lateral edges of the supraoccipital, and a postorbital process of the frontal oriented posteriorly. It can be distinguished from the only other Miocene balaenid, Peripolocetus in having a dorsoventrally expanded zygomatic process of the squamosal. The body length of Morenocetus is estimated at 17 to 18 feet (5.2 to 5.5 m), and the rostrum is moderately arched dorsoventrally in contrast to crown Balaenidae.[1]

Classification

Morenocetus is the oldest named extinct balaenid so far, although a chaeomysticete specimen from late Oligocene marine deposits in New Zealand was reported as a stem-balaenid in an SVP 2002 abstract by Ewan Fordyce.[2]

References

  1. ^ Buono M.R., Fernández M.S., Cozzuol M.A., Cuitiño J.I., Fitzgerald E.M.G. (2017) The early Miocene balaenid Morenocetus parvus from Patagonia (Argentina) and the evolution of right whales. PeerJ 5:e4148
  2. ^ Fordyce, R.E., 2002. Oligocene origin of skim–feeding right whales: a small archaic balaenid from New Zealand. Journal of Vertebrate Paleontology 22:54A

Further reading

  • A. Cabrera. 1926. Cetaceos fósiles del Museo de La Plata. Revista del Museo de La Plata 29:363-411
2017 in mammal paleontology

This article records new taxa of fossil mammals of every kind that have been described during the year 2017, as well as other significant discoveries and events related to paleontology of mammals that occurred in the year 2017.

Balaenidae

Balaenidae is a family of whales of the parvorder Mysticeti that contains two living genera: the right whales (genus Eubalaena), and in a separate genus, the closely related bowhead whale (genus Balaena).

Baleen whale

Baleen whales (systematic name Mysticeti), known earlier as whalebone whales, form a parvorder of the infraorder Cetacea (whales, dolphins and porpoises). They are a widely distributed and diverse parvorder of carnivorous marine mammals. Mysticeti comprise the families Balaenidae (right and bowhead whales), Balaenopteridae (rorquals), Cetotheriidae (the pygmy right whale), and Eschrichtiidae (the gray whale). There are currently 15 species of baleen whales. While cetaceans were historically thought to have descended from mesonychids, (which would place them outside the order Artiodactyla), molecular evidence supports them as a clade of even-toed ungulates (Artiodactyla). Baleen whales split from toothed whales (Odontoceti) around 34 million years ago.

Baleen whales range in size from the 20 ft (6 m) and 6,600 lb (3,000 kg) pygmy right whale to the 102 ft (31 m) and 190 t (210 short tons) blue whale the largest known animal to have ever existed. They are sexually dimorphic. Baleen whales can have streamlined or large bodies, depending on the feeding behavior, and two limbs that are modified into flippers. Though not as flexible and agile as seals, baleen whales can swim very fast, with the fastest able to travel at 23 miles per hour (37 km/h). Baleen whales use their baleen plates to filter out food from the water by either lunge-feeding or skim-feeding. Baleen whales have fused neck vertebrae, and are unable to turn their head at all. Baleen whales have two blowholes. Some species are well adapted for diving to great depths. They have a layer of fat, or blubber, under the skin to keep warm in the cold water.

Although baleen whales are widespread, most species prefer the colder waters of the Arctic and Antarctic. Gray whales are specialized for feeding on bottom-dwelling crustaceans. Rorquals are specialized at lunge-feeding, and have a streamlined body to reduce drag while accelerating. Right whales skim-feed, meaning they use their enlarged head to effectively take in a large amount of water and sieve the slow-moving prey. Males typically mate with more than one female (polygyny), although the degree of polygyny varies with the species. Male strategies for reproductive success vary between performing ritual displays (whale song) or lek mating. Calves are typically born in the winter and spring months and females bear all the responsibility for raising them. Mothers fast for a relatively long period of time over the period of migration, which varies between species. Baleen whales produce a number of vocalizations, notably the songs of the humpback whale.

The meat, blubber, baleen, and oil of baleen whales have traditionally been used by the indigenous peoples of the Arctic. Once relentlessly hunted by commercial industries for these products, cetaceans are now protected by international law. However, the North Atlantic right whale is ranked endangered by the International Union for Conservation of Nature. Besides hunting, baleen whales also face threats from marine pollution and ocean acidification. It has been speculated that man-made sonar results in strandings. They have rarely been kept in captivity, and this has only been attempted with juveniles or members of one of the smallest species.

Bowhead whale

The bowhead whale (Balaena mysticetus) is a species of the family Balaenidae, in parvorder Mysticeti, and genus Balaena, which once included the right whale.

A stocky dark-coloured whale without a dorsal fin, it can grow 14 to 18 m (46 to 59 ft) in length. This thick-bodied species can weigh from 75 to 100 tonnes (74 to 98 long tons; 83 to 110 short tons). They live entirely in fertile Arctic and sub-Arctic waters, unlike other whales that migrate to low latitude waters to feed or reproduce. The bowhead was also known as the Greenland right whale or Arctic whale. American whalemen called them the steeple-top, polar whale, or Russia or Russian whale. The bowhead has the largest mouth of any animal.The bowhead was an early whaling target. The population was severely reduced before a 1966 moratorium was passed to protect the species. Of the five stocks of bowhead populations, three are listed as "endangered", one as "vulnerable", and one as "lower risk, conservation dependent" according to the IUCN Red List. The global population is assessed as of least concern.

List of extinct cetaceans

The list of extinct cetaceans features the extinct genera and species of the order Cetacea. The cetaceans (whales, dolphins and porpoises) are descendants of land-living mammals, the even-toed ungulates. The earliest cetaceans were still hoofed mammals. These early cetaceans became gradually better adapted for swimming than for walking on land, finally evolving into fully marine cetaceans.

This list currently includes only fossil genera and species. However, the Atlantic population of gray whales (Eschrichtius robustus) became extinct in the 18th century, and the baiji (or Chinese river dolphin, Lipotes vexillifer) was declared "functionally extinct" after an expedition in late 2006 failed to find any in the Yangtze River.

Pelagornithidae

The Pelagornithidae, commonly called pelagornithids, pseudodontorns, bony-toothed birds, false-toothed birds or pseudotooth birds, are a prehistoric family of large seabirds. Their fossil remains have been found all over the world in rocks dating between the Late Paleocene and the Pliocene-Pleistocene boundary.Most of the common names refer to these birds' most notable trait: tooth-like points on their beak's edges, which unlike true teeth contained Volkmann's canals and were outgrowths of the premaxillary and mandibular bones. Even "small" species of pseudotooth birds were the size of albatrosses; the largest ones had wingspans estimated at 5–6 metres (15–20 ft) and were among the largest flying birds ever to live. They were the dominant seabirds of most oceans throughout most of the Cenozoic, and modern humans apparently missed encountering them only by a tiny measure of evolutionary time: the last known pelagornithids were contemporaries of Homo habilis and the beginning of the history of technology.

South American land mammal age

The South American land mammal ages (SALMA) establish a geologic timescale for prehistoric South American fauna beginning 64.5 Ma during the Paleocene and continuing through to the Late Pleistocene (0.011 Ma). These periods are referred to as ages, stages, or intervals and were established using geographic place names where fossil materials where obtained.The basic unit of measure is the first/last boundary statement. This shows that the first appearance event of one taxon is known to predate the last appearance event of another. If two taxa are found in the same fossil quarry or at the same stratigraphic horizon, then their age-range zones overlap.

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