From Olsen (1959). Reproduced with permission of the Florida Geological Survey
Basilosaurusis one of the most common of the primitive whales, called "archaeocetes" by paleontologists, that have found in exposures of Middle to Upper Eocene, 35 to 40 million year old, marine sediments within central Louisiana. The species of Basilosaurus found in Louisiana, Basilosaurus cetoides (Owen), had a streamlined body that averaged 45 to 70 feet in length. Its body looked more like the body of a mythical sea serpent rather then the body of a modern whale. Basilosaurus had a wedged-shaped head up to 5 feet long with jaws containing two types of teeth. The teeth in the front, anterior, of the jaw had cone-shaped teeth which caught and held its prey while triangular-shaped teeth in the rear, posterior, of the jaw sliced them up. The type and amount of wear on the teeth of the Basilosaurus indicates that it likely ate fish and squid (Johnston 1991 Carpenter and White 1986).
The bones of Basilosaurus cetoides (Owen) and other primitive whales have been found throughout a belt across Louisiana, Mississippi, and Alabama where exposures of Middle and Upper Eocene marine strata, called the Moodys Branch Formation (or Marl) and the Yazoo Clay occur. The vertebrates were so common within some areas of this belt that local residents used them as andirons for fireplaces and blocks to support cabins. The bones and skeletons of Basilosaurus also have been found in Australia, Egypt, within other marine sediments of Upper Eocene age (Domning 1969, Johnston 1991, Thurmond 1981).
In Louisiana, numerous bones of Basilosaurus and another primitive whale, Pontogeneus brachyspondylus (Muller), have been recovered from bluffs along the Ouachita River that expose the Moodys Branch and Yazoo Clay in Caldwell Parish. Isolated exposures of these marine sediments in Catahoula, Grant, and La Salle Parishes have yielded the scattered bones from Basilosaurus and Zygorhiza kochii (Riechenbach). The latest of these finds was the front quarter of a Basilosaurus skeleton at Montgomery Landing along the Red River near Montgomery, Louisiana. Although a partial skeleton, this find yielded a beautifully preserved complete skull (Domning 1969, Lancaster 1986).
The fossils of Basilosaurus cetoides (Owen) and Zygorhiza kochii (Riechenbach) were the first of many fossil finds that show that modern whales, e.g. the humpback whales evolved from dog-like creatures known as Mesonychids. Both Basilosaurus and Zygorhiza, exhibit unmistakable characteristics of the terrestrial Mesonychids from which they developed. For example, their skulls retained many of the features of the mesonychids despite a pronounced elongation. Also, the primitive whales such as Basilosaurus processed the distinctive, teeth set of the Mesonychids with well-defined incisors, canines, premolars, and multirooted molar. In addition, these whales, e.g. Basilosaurus, had well-defined vestigial rear legs (Gingerich et al. 1990, 1993, Thewissen 1994).
Later, these primitive whales gave rise to toothless and toothed whales. In case of the toothed whales, the teeth evolved into the teeth of the toothed whales, e.g. the dolphins, killer whales, and sperm whales. The Baleen (toothless) whales, the other branch of whales, developed modified mouth structures that strained plankton from the seawater enabling them to graze the oceans. It should be noted that although it belongs to the group of primitive whales ancestral to modern whales, Basilosaurus is likely a relative of the direct ancestors of modern whales. Rather, it appears that Zygorhiza was closer to the direct line of descent of modern whales than Basilosaurus (Gingerich et al. 1990, 1993, Thewissen 1994).
For a long time, Basilosaurus was among the earliest known whales being found in rocks as old as Middle Eocene. Since its discovery in 1834, no older primitive whales transitional to ancestral land-mammals had been discovered from earlier rocks leaving an obvious gap in the fossil record. However, research in Pakistan and elsewhere have found the critical fossils to fill a substantial portion of this gap. Among the ancestors or close relatives to the ancestors of Basilosaurus and modern whales are:
1. Rodhocetus kasrani - Eocene (Gingerich et al. 1994)
2. Pakicetus - latest Early Eocene (Gingerich et al. 1983, Thewissen et al. 1993)
3. Ambulocetus natans - Early to Middle Eocene (Thewissen 1994)
4. Indocetus ramani - earliest Middle Eocene (Gingerich et al. 1993)
In 1840's, Louisiana, Mississippi, and Alabama all became famous for the discovery of fossil primitive whales within a belt of outcropping Eocene strata. Dr. Richard Harlan first described Basilosaurus cetoides (Owen) in 1843 from bones collected by a wealthy Arkansas physician from the bluffs along the Ouachita River within Caldwell Parish about two years earlier. Thinking that these were the remains of giant Tertiary marine reptile, Dr. Harlan named the animal represented by these bones "Basilosaurus". Thus although a mammal, Basilosaurus translates as "king of the lizards". Later, Sir Richard Owen described on an almost complete skeleton discovered in Alabama. He recognized that Basilosaurus was a primitive whale, the first found in North America (Domning 1969, Johnston 1991). Mike Everhart has written an article about the naming of Basilosaurus in the article, "Basilosaurus - The plesiosaur that wasn't...." which is posted at his Oceans of Kansas Paleontology web page.
Paleontologists found during the 1800's the remains of Basilosaurus and another primitive whale, Zygorhiza kochii (Riechenbach), throughout the outcrops of Upper Eocene strata in Louisiana, Mississippi, and Alabama. Paleontologists have excavated significant partial or complete skeletons of Basilosaurus at Montgomery Landing in Louisiana and within Madison County, Mississippi. In 1971, a complete skeleton of Zygorhiza was excavated by paleontologists and members of the Mississippi Gem and Mineral Society near Tinsley, Mississippi (Domning 1969, Kellog 1936).
Primitive Eocene whales are the state fossils of both Alabama and Mississippi. In 1981, Mississippi Senate Current Resolution No. 557 designated "the prehistoric whale", both Basilosaurus cetoides (Owen) and Zygorhiza kochii (Riechenbach), as the official fossil of Mississippi. Later, in 1984, the Alabama legislature made Basilosaurus cetoides (Owen) the state fossil of Alabama by Act. No. 84-66.
A complete skeleton of Basilosaurus cetoides (Owen) can be found at the Smithsonian Institute in Washington D.C.
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