DOLFIJNEN EN TANDWALVISSEN

http://tsjok45.multiply.com/photos/album/90/dolfijn_e.a._

odontoceti.jpg

UNIV of BRISTOLhttp://palaeo.gly.bris.ac.uk/palaeofiles/whales/odontoceti.htm

nature09067-f2.2.jpg

http://www.bloggen.be/evodisku/archief.php?startdatum=1277935200&stopdatum=1280613600

http://www.edwardtbabinski.us/whales/evolution_of_whales/

Squalodon calvertensis,long-snouted shark toothed whaleSqualodons lived from the early-middle Oligocene into the middle Miocene, roughly 33 to 14 million years ago. Thesqualodongenus belongs to the Odontocete Order, the toothed whales. Specifically it belongs to the Squalodontidae superfamily. This superfamily is named after the shark squallus, since its' cheek teeth superficially resemble the teeth of a squallus shark; hence the name "shark toothed whale". The Squalodontidae superfamily contains three different groups of medium-sized (roughly 3 meters in length) shark toothed whales. They are the short-snouted shark toothed whales (prososqualodon), the medium-snouted shark toothed whales (phoberodon), and the long-snouted shark toothed whales. This last group contains the genus squalodon.A strange mix of archaic and modern features characterizes this interesting superfamily. One of the most noticeable archaic features is their complex dentition. While other toothed whales were evolving simple conical teeth at this time, Squalodontidae retained their primitive teeth that their ancestors (the archaeocetis) had. For example their dentition is complex, their teeth are widely spaced apart, and their cheek teeth are triangular and serrated for grasping and cutting.Despite these ancient features on Squalodontidae, they also had a mix of modern characteristics. For example, their craniums were well compressed, as their rostrums were telescoped outward, giving the appearance of modern toothed whales. Finally, squalodon skulls show evidence for the first appearance of echolocation.

Notice the front teeth protruding from the jaw, creating small "tusks."

Source:www.fossilguy.com

Shark-toothed dolphins (Family Squalodontidae)Shark-toothed dolphins are large extinct odontocetes with long narrow jaws and teeth that vary markedly from front to back in the jaws. These animals the squalodontids - were widespread and diverse in the Late Oligocene and the Early to Middle Miocene (about 28 to 15 million years ago), but then disappeared. J-P-S Grateloup, a French scientist, proposed the name Squalodon for a fragment of jaw in 1840. Grateloup thought that the fossil might represent a reptile. Later finds from around the North Atlantic revealed that these animals were mammals, with skulls somewhat like those of living odontocetes - the toothed whales, dolphins and porpoises. However, the teeth were unlike any modern species. Living odontocetes typically have simple conical teeth that dont vary much from front to back in the jaws, but squalodontid teeth are differentiated: at the tip of the jaw are incisors with conical crowns, which grade back into teeth with lower crowns and small, multiple denticles or cusps. Similarly differentiated teeth occur in archaic or ancestral cetaceans, the Archaeoceti.

Eventually, the shark-toothed dolphins were placed in their own family, Squalodontidae. By 1923, when Dr Remington Kellogg reviewed the family, specimens had been reported from many parts of the world. Some squalodontids were known from rather complete skulls, such as represented by Squalodon calvertensis from Miocene rocks of Chesapeake Bay region, but most were reported only from one or a few isolated teeth. Despite the incomplete nature of many specimens, some were used as the basis for new species and genera. (Some of the teeth might not even represent odontocetes, let alone squalodontids.) In the 1960s, Prof.-Dr Karlheinz Rothausen (then of Johannes-Gutenberg University, Mainz, Germany) reviewed the group in several articles. For many decades, it was thought that squalodontids represented a stock from which many or most living odontocete groups evolved. In the late 1980s, Dr Christian de Muizon concluded that squalodontids are related closer to the endangered living Ganges dolphin, Platanista gangetica, than to any other living species. De Muizon based his assessment of relationships particularly on the scapula (shoulder blade) and also on the ear region. It is likely the squalodontids have little to do with the ancestry of most living dolphins. In the 1990s, Ewan Fordyce found a fossil dolphin later named Waipatia - with superficially squalodontid-like teeth. Formerly, as Kellogg 1923 showed, such dolphins had indeed been identified as squalodontids. In 1994, Waipatia was named and put in a new group, Waipatiidae, separate from but related to the original squalodontids. It is now accepted thatancient dolphins withdifferentiated teeth(= heterodont)belong in various families, not only the Squalodontidae.

Source:R.Ewan Fordyce

Prosqualodon (Shark-toothed Dolphin)

This fossilised skull is from a primitive shark-toothed dolphin. The skull and jaws are framing Andrew Grebneff, who prepared the fossil at the University of Otagos geology museum. The fossil was found in the Otekaike limestone in Waitaki valley, and is from the Late Oligocene age, about 25 million years ago. At the time this dolphin died, the area was a large shallow sea. These animals were widespread 28 to 15 million years ago, but then became extinct.http://www.teara.govt.nz/EarthSeaAndSky/Geology/Fossils/4/ENZ-Resources/Standard/2/enProsqualodon (Shark-toothed Dolphin)

http://www.otago.ac.nz/geology/research/paleontology/paleohistory.html

Preparator Andrew Grebneff prepares a skull of a new species of fossil dolphin from the Otekaike Limestone of the Waitaki Valley region. The specimen is of Late Oligocene age, about 24 million years.

Skull of Prosqualodon davidiHarry Taylor (c) Dorling Kindersley, Courtesy of the Natural History Museum, London

Dolfijn washington.JPG

http://www.washington.edu/burkemuseum/collections/paleontology/marine/whales.php

Living dolphins belong to one subgroup of whales called the Odontocetiwhales with teeth, like the orca (or killer whale). Baleen whales form the other group of living whales, called the Mysticeti that have baleen and do not have teeth.Some of the fossil dolphins in the Burke collection belong to an entirely extinct group that have teeth, but also exhibit the arrangement of skull bones similar to that of baleen whales. The few bones that we have from the skeletons found with the skulls show that the animals were the approximate size and shape of living dolphins. Some have very elongate snouts, resembling the river dolphins that swim in the Ganges River (India and Nepal) and Yangtze River (China) today.

These unique fossils from Washington illustrate the evolution of baleen and the eventual loss of teeth in the mysticete group of whales.

(Links )http://www.uvm.edu/whale/TableOfContents.htmlThe Charlotte whale is a beluga whale (Delphinapterus leucas), approximately 12 feet in length. Although it is not possible to determine the sex of the specimen, tooth wear and skull sutures indicate that it was an adult.

(rechts ) Beluga

http://bio.kuleuven.be/endo/vakken/dolfijnschedel.jpg

fossil skull dolphin

http://fr.cinoa.org/art-and-antiques/detail/21624A Complete Early Prehistoric Fossil Dolphin SkullMediumFossil Dolphin SkullProvenanceProvenance : Found at Lyme Regis, Dorset in 1949 by Sir Arnold de Mout Morosey of Southwold. Identified by Mr Duncan Cooper of Norwich Museum where it remained exhibited on loan for many yearsLiterature:The earliest representations of fossils are the animal paintings or carvings found in the Palaeolithic caves of Europe that date back to a time when some of the creatures we now know only as fossils, such as this dolphin, were still alive.During the Pliocene period ( 5.3 - 1.75 million years ago ) the modern forms of whales and the closely related dolphins were gradually replacing the more primitive species. It is believed that the early forms of the Eocene whale like creatures who mostly inhabited shallow tropical seas may have descended from land dwelling mesonychids that took to foraging for food in shallow water. While mesonychid skulls and skeletons are strikingly similar to those of the first whales recent DNA studies suggest that they may actually be artiodactyls, even-toed hoofed mammals, more closely related to hippopotamuses. This area is still the subject of great debate.

Description / ExpertiseA Complete Early Prehistoric Fossil Dolphin Skull150000 Years Old

Size : 48 cm long 19 ins long

old & modern

Fossil dolphin (front)compared with modern dolphin (back)Photo: Ewan Fordycehttp://www.aad.gov.au/default.asp?casid=3370

http://visual.merriam-webster.com/animal-kingdom/marine-mammals/dolphin/morphology-dolphin.php

http://visual.merriam-webster.com/animal-kingdom/marine-mammals/dolphin/skeleton-dolphin.php

On identifying a dolphin skullhttp://scienceblogs.com/tetrapodzoology/2008/07/identifying_dolphin_skull.php

Delphininae:

[image here shows skull ofDelphinus(at top) andStenella. Images United States National Museum, courtesy C. McHenry].

Long-beaked Common Dolphin Skull

short -beaked Common Dolphin Skull

De snorharen van de dolfijn

http://www.volkskrantblog.nl/bericht/260683

Tomaso Agricola

Dat dolfijnen voorouders hadden die op het land leven heb ik

eerder al eens betoogd aan de hand van fossiel materiaal --->

http://en.wikipedia.org/wiki/Evolution_of_cetaceans.

In een artikel met de titelFrom land to water: the origin of whales, dolphisn en porpoisesin het tijdschriftEvolution Education Outreac