Whale Evolution and Atavistic Hind Limbs on Modern Whales

Pelvic bone on modern whales
Photographs of Humpback and Pilot Whale mounts contributed by the Milwaukee Public Museum with commentary by Professor Hans Thewissen.

The Evolution of Whales
Based on the sensational National Geographic article from November 2001, The Evolution of Whales. Overview of whale origins. Includes illustrations based on fossil progressions in transitional whales and dolphins. Additional comments from early whale expert and Paleontologist, J.G.M. Thewissen, Northeastern Ohio Universities College of Medicine.

Hind Limb Bud Images, Dolphin Embryo and Fetus Development
Photographs of hind limb buds on a five week old Pantropical Spotted Dolphin embryo, and 1.5 to 4 month fetus development. Images courtesy of Professor J.G.M. Thewissen.

Sirenian Evolution
(Manatee, Sea Cow, Dugong)
Sirenians and Elephants are evolved from a common ancestor. Like whales, sirenians returned to the water. Though hind limbs on whales may be rare and difficult to witness, many sirenians (not all) still retain vestigial toenails like their elephant cousins, and share other traits in common with modern elephants. Includes commentary between LeVar Burton and Dr. Mark Lowe, Veterenary Science. Contains images courtesy of Reading Rainbow, PBS Television. (GPN/Nebraska Educational Telecommunications and WNED-TV, Buffalo NY).

  • A Dolphin with Hind Limbs, Science Blogs
  • Dolphin May Have 'Remains' of Legs, Associated Press
  • Answers In Genesis Response to Dolphin Hind Limb Discovery
  • Response to AiG's Response on Dolphin Hind Limbs

    Dolphin Hind Limbs


    Dolphin Hind Limbs - Response to Answers in Genesis (AiG)
    Answers in Genesis' changing views on hind limb rudiments on cetaceans after discovery of dolphin with four fins.


    CONTENTS:

  • INTRODUCTION: The Evolution of Whales
    Introduction into the controversy over the origins of modern whales which retain vestigial hind limb rudiments. Cladogram of early whales to modern whales.
  • REVIEW OF Strange Tale of the Leg on the Whale
    Vestigial pelvises on whales, denial of femurs by Creationists (calling it bone disease). Creationists say these remnants were designed for copulation only, but science says this is how Evolution works --finding new purpose for old structures.
  • REVIEW OF Strange Tale of the Leg on the Whale
    Out of date information published by Creationists. New fossil finds of early whales. Contains image of complete leg bones from basilosaurus, and reconstruction of the creature's likely appearance.
  • REVIEW OF A Whale of a Tale? (Ambulocetus) Don Batten
    The whale tail and Ambulocetus' lack of a fluke, nasal drift and canine teeth in early whales. Image showing nasal drift from early to modern whales.
  • REVIEW OF Overselling of Whale Evolution
    Questions on the dating of varied early whales, and further suggested reading on whale evolution. The evolution of eco-location, nursing young (suggesting common ancestry with land mammals), and the brain of humans vs. cetacea.
  • Land to Sea: Inner Ear Transitions in Whales
    Images of transitional inner ear of whales, as they evolved from land to sea mammals. Professor Hans Thewissen explains the differences of earbone fossils, the incus and tympanic.
  • Pelvic Bones on Whales, Ambulocetus
    Answers in Genesis knowingly placed out of date information on the web to refute up to date information. An example of blatant non-scientific misrepresentation of fossil evidence in an attempt to discredit evolutionary fact as speculative theory.
  • Example One of Hind Limb Rudiments
    1958, caught in the Bering Sea - An X-Ray revealing bone structures and a photograph taken of the protrusions on the whale's body.
  • Example Two of Hind Limb Rudiments
    1919 Historical record and photos of a female humpback with protruded hind limbs including femur, tibia and tarsus, and 1914 report of protruded limbs on embryoes. Images of protruded limb on Cachalot.
  • Example Three of Hind Limb Rudiments
    Female Sperm Whale, caught in 1956. Upon examining the interior of the limb three partially cartilaginous bones were found. Corresponding to the pelvis, femur, and possibly to the tibia.
  • Example Four of Hind Limb Rudiments
    A list of catches between 1956 and 1963 of whales caught and discovery of hind limb protrustions, including the approxiamate percentage of whales.
  • Example Five of Hind Limb Rudiments
    Struthers' commentary on the dissection of a right whale and photos from the Museum of Zoology, including further diagrams. Some interesting facts concerning the pelvic anatomy of the majority of modern day whales.
  • Evolutionary Atavisms
    Atavisms and tails on human beings, summary to a creationist by K. Nahigian
  • Pelvic Rudiment

    Skeleton of adult male, Blaineville's Beaked Whale, Mesoplodon densirostris in the Australian Museum, Sydney (after Van Beneden and Gervais, 1868-1879). Forelimb and and pelvic rudiment are from an adult male of the same species in the American Museum of Natural History (after Raven, 1942).
    Encyclopedia of Marine Mammals
    William F. Perrin, Bernd Wursig, J.G.M. Thewissen

    RECOMMENDED READING

    Whale Evolution - Origine (trueorigins.us)
    An analysis of the newer evidences for macro-evolution, and problems with scriptures.

    The Emergence of Whales, J.G.M. Thewissen, PhD
    The Emergence of Whales
    , Evolutionary Patterns in the Origin of Cetacea (Advances in Vertebrate Paleobiology) (Hardcover)
    by J. G. M. Thewissen (Editor)

    Review from Journal of Mammology, August 6, 2002
    Reviewer: Jasmine Benzvi (New York, NY)
    'Up to now, a 'state of the art' summary of research on whale origins has not been available. This book admirably fills that void and should be added to the library of any serious mammologist or paleomammalogist.'
    - by Annalisa Berta

    Encyclopedia of Marine Mammals
    Encyclopedia of Marine Mammals
    (Hardcover)
    by William F. Perrin (Editor), Bernd Wursig (Editor), J.G.M. Thewissen (Editor)

  • "This impressive reference would make an excellent addition to any library..."-ENCYCLOPEDIA OF DINOSAURS AND VOLCANOES (February 2003)
  • "Very highly recommended for students, professionals, researchers and lay people with an interest in marine mammals."
    WILDLIFE ACTIVIST (Fall 2002)
  • "...an excellent resource for beginning research. ...This encyclopedia is very highly recommended for all academic and larger public libraries." Teresa Bowden, Villanova University Falvey Memorial Library for E-STREAMS (September 2002)
  • "...students beginning postgraduate study on marine mammals and researchers and academics working on marine mammals will find it indispensable."

    On 6/17/2005 3:51:22 PM, Terry wrote:
    home.earthlink.net/~w0dfi/pet.html
    Terry's Whale.
    I think you will really enjoyed this full whale skelton, I think it is a "blue" whale I forget…maybe you have seen it?
    I took the picture in the Gulf of Mexico this year but the Skeloton is on Los Conchos Beach east of Puerte Penasco, Sonora, Mexico.
    I only had an instant Camera but that's better than nothing. I think it was a Blue whale?? or one with a huge mouth? -Terry and Pets

    Dolphin Hind Limbs

    TOKYO Nov 5, 2006 (AP), Japanese scientists reported a bottlenose dolphin, has an extra set of fins that could be the remains of hind limbs. The dolphin was captured alive in western Japan on Oct. 28, by Fishermen. "I believe the fins may be remains from the time when dolphins' ancient ancestors lived on land," said Seiji Osumi, of Tokyo's Institute of Cetacean Research. The hind fins are much smaller than the front fins and are about the size of human hands, protruding near the tail. The dolphin measured approx 9 feet in length.

Japan's Four-Fin Dolphin Discovery
Vestigial Limb Remains Vestigial Limb Remains Vestigial Limb Remains
Vestigial Limb Remains Vestigial Limb Remains Vestigial Limb Remains
Vestigial Limb Remains Vestigial Limb Remains Vestigial Limb Remains
Vestigial Limb Remains

Origin of Sirenians

Earliest Sirenians, Prorastomus and Protosiren. Timeline of Sirenian Evolution and Extinctions.

Sirenian Evolution
by Sharon Mooney, with excerpts and paraphrased from Daryl P. Domning, Howard University, Washington, DC
Encyclopedia of Marine Mammals
Academic Press, 20002; Perrin, Würsin and Thewissen

Sirenia are the order of placental mammals which comprise modern sea cows (manatee and dugongs) and their extinct relatives. They are the only herbivorous marine mammals now in existence and the only group of herbivorous mammals to have became completely aquatic. Sirenians have a 50 million year old fossil record (early Eocene-Recent). They attained modest diversity during the Oligocene and Miocene, but have since declined as a result of climatic cooling, oceanographic changes, and human interference. Two genera and four species are extant: Trichechus which includes three species of Manatee that live along the Atlantic Coasts and in rivers and coastlines of the Americas and Western Africa. Amazonian Manatee live only in fresh water and Dugongs are found in the Indian and Pacific oceans.

West Indian Manatee

Family: Trichechidae
West Indian Manatee
Trichechus manatus
Subspecies: Trichechus manatus latirostris (Florida manatee) and Trichechus manatus manatus (Antillean manatee)
Source: Sirenians of the World
Public Access Image may be redistributed, on condition all original credits are kept intact.

Amazonian Manatee

Family: Trichechidae
Amazonian Manatee
Trichechus inunguis
Source: Sirenians of the World
Public Access Image may be redistributed, on condition all original credits are kept intact.

West African Manatee

Family: Trichechidae
West African Manatee
Trichechus senegalensis
Source: Sirenians of the World
Public Access Image may be redistributed, on condition all original credits are kept intact.

Dugong

Family: Dugongidae
Dugong
Dugong dugon
Source: Sirenians of the World
Public Access Image may be redistributed, on condition all original credits are kept intact.

Steller's Sea Cow

Family: Dugongidae
Steller's Sea Cow
Hydrodamalis gigas

At one time, the Steller's sea cow was found in the cold waters of the Bering Sea, but it was hunted to extinction within 27 years of its discovery in 1741. The largest sirenian on record, the Steller's sea cow grew up to nine meters (30 feet) in length and weighed around four metric tons (approximately 4.4 tons).

 

Source: Sirenians of the World
Public Access Image may be redistributed, on condition all original credits are kept intact.

 

Sirenian Origins
Sirenians' closest living relative are Proboscidea (elephants). Tethytheria, are a larger group comprised of Sirenia, Proboscidea, extinct Demostylia and likely the extinct Embrithopoda. Tethyeria appear to have evolved from primitive hoofed mammals known as condylarths, along the shores of the ancient Tethys sea.
The tethyeria, combined with Hyracoidea (hyraces) form an inclusive group called Paenungulata. Paenungulata and Tethytheria (especially the latter) are among the least controversial mammalian orders, with strong support from morphological and molecular research. The ancestry of sirenia is remote from cetacea and pinnipeds, though re-evolving an aquatic lifestyle simultaneously.

 

Fossil History
The first appearance of Sirenians in the fossil record was during the early Eocene, and by the late Eocene, sirenians had significantly diversified. Inhabitants of rivers, estuaries, and nearshore marine waters, they were able to spread rapidly. The most primitive sirenian known to date, Prorastomus, was found in Jamaica, not the Old World.

 

Prorastomus, Early Sirenian found in Jamaica
Prorastomus

Based on Sagascience Evolution and Daryl P. Domning
Public Access Image may be redistributed, on condition all original credits are kept intact.

The earliest known sea cows, of the families Prorastomidae and Protosirenidae, are both confined to the Eocene, were about the size of a pig, four legged amphibious creatures. By the time the Eocene drew to a close, came the appearance of the Dugongidae and Sirenians had acquired their familiar fully-aquatic streamliined body with flipper-like front legs with no hind limbs, powerful tail with horizontal caudal fin, with up and down movements which move them through the water, like Cetaceans.

Protosiren

Protosiren
Based on Cranial Morphology of Protosiren fraasi, (Mammalia, Sirenia) from the Middle Eocene of Egypt: A New Study Using Computed Tomography

Adapted for web by Sharon Mooney (2006)
New reconstruction of type skull of Protosirenfraasi, CGM 10171, with additions from SMNS 10576. Dentary is shown in outline, based on CGM 42297, which may be part of type specimen (see Andrews, 1906). Reproduced ca. 0.45 x natural size. Abbreviations (after Domning, 1978, with additions): AC, alisphenoid canal; AS, alisphenoid; c', upper canine alveolus; EO, exoccipital; FR, frontal; 1' etc., upper incisor alveoli; J, jugal; MI etc., lower molars; MF, mastoid foramen; MX, maxilla; OC, occipital condyle; P1 etc., upper premolar alveoli; PA, parietal; PM, premaxjlla; SO, supraoccipital; SQ, squamosal; SR, sigmoid ridge.
Public Access Image 500 px and Protosiren 750 px may be redistributed, on condition all original credits are kept intact.

The last of the Sirenian families who made their appearance, Trichechidae, apparently arose from early Dugongids in the late Eocene or early Oligocene. The current fossil record documents all major stages in hindlimb and pelvic reduction from completely terrestrial morphology to the extreme reduction in modern manatee pelvis, providing an example of dramatic evolutionary change among fossil vertebrates.

Sirenian Locomotion
Evolution in Sirenian Locomotion

Based on Marine Mammals: Evolutionary Biology, Annalisa Berta, James L. Sumich
Public Access Image may be redistributed, on condition all original credits are kept intact.

Skeleton of Metaxytherium floridanum - Early Sirenian

Metaxytherium floridanum

Based on Encyclopedia of Marine Mammals
Skeleton of Metaxytherium floridanum, a Miocene halitheriine dugongid. Total length about 3.2 meters. After Domning (1988); original image, Journal of Vertebrate Paleontology. Re-illustrated by Sharon Mooney.
Public Access Image 750 px and Metaxytherium floridanum 500 px may be redistributed, on condition all original credits are kept intact.

Since sirenians first evolved, they were herbivores, likely depending on seagrasses and aquatic angiosperms (flowering plants) for food. To the present, almost all have remained tropical, marine and consume angiosperms. Sea cows are shallow divers with large lungs, they have heavy skeletons to help them stay submerged. The bones are pachyostotic (swollen) and osteosclerotic (dense), especially the ribs which are often found as fossils.

Eocene sirenians, like Mesozoic mammals but in contrast to other Cenozoic ones, have five instead of four premolars, giving them a 3.1.5.3 dental formula. Whether this condition is truly a primitive retention in Sirenians is still under debate.

Although cheek teeth are relied on for identifying species in other mammals, they do not vary to a significant degree among Sirenians in their morphology, but are almost always low-crowned (brachyodont) with two rows of large, rounded cusps (bunobilophodont). The easiest identifiable parts of sirenian skeletons are the skull and mandible, especially the frontal and other skull bones. With the exception for a pair of tusk-like first upper incisors present in most species, front teeth (incisors and canines) are lacking in all, except the earliest sirenians.

DUGONGIDAE
Dugongids comprise the majority of specimens that compose the known sirenian fossil record. The basal members of this family are placed in the Eocene-Pliocene, and subfamily Haliteriinae. This group includes the fossil genera Halitherium and Metaxytherium.

Metaxytherium gave rise in the Miocene to the Hydrodamalinae, an endemic North Pacific lineage that ended with Steller's sea cow (Hydrodamalis) - the largest sirenian that ever emerged, with a length of up to 9 meters or more. This species was also the only one which make a successful adaptation to temperate and cold waters, and diet of marine algae. It was completely toothless and its truncated, claw like flippers which it used for gathering plants and fending off from rocks, lacked the presence of phalanges (finger bones). Humans hunted Steller's Seacow to extinction in the eighteenth century.

Another offshoot of Halitheriinae, the subfamily Dugonginae, appeared in the Oligocene. Most dugongines appear to have been specialists at digging out and eating tough, buried rhizomes of seagrasses; for this purpose many had large, self-sharpening blade-like tusks (Domning, 2001). Modern Dugong is the only survivor of this group, but it has reduced dentition (cheek teeth having only thin enamel crowns, which quickly wear off and leave simple pegs of dentine. For this reason, the dugong likely shifted toward a more delicate diet, consisting of seagrasses and ceased using its tusks for digging.

TRICHECHIDAE
The Trichechidae have by far more a scant fossil record than dugongids. Their definition has been widened to incorporate Miosireninae, a little-known pair of genera that inhabited NW Europe in the late Oligocene and Miocene. Miosirenines had massively reinforced plates and dentitions that may have been used for crushing shellfish. Such diet in sirenians living around the North Sea seems of little surprise considering modern dugongs and manatee near the climatic extremes of their ranges are known to consume invertebrates in addition to plants.

Manatees are now placed in the subfamily Trichechinae. They first made their appearance in the Miocene, represented by Potamosiren from fresh water deposits in Columbia. Much of trichechine history was likely spent in South America, from where they spread to North America and Africa only in the Pliocene or Pleistocene.

It was during the late Miocene, manatees living in the Amazon basin apparently adapted to a diet of abrasive freshwater grasses, and this innovation is still used by their modern descendants. Interestingly, they continue to add on extra teeth to the molar series their entire lifetime. As worn teeth fall out at the front, the whole tooth row slowly shifts to the front to make room for new teeth erupting in the rear. This horizontal tooth replacement has often been likened, incorrectly, to that of elephants, but the latter are only limited to three molars. Only one other mammal, an Australian rock wallaby (Peradorcas concinna) has truly evolved the same kind of tooth replacement system, found in manatees.
Adapted from Sirenian Evolution, Daryl P. Domning, Howard Encyclopedia of Marine Mammals, pp. 1083-1086

Sirenian Evolution Chart

Source: Encyclopedia of Marine Mammals

Set to web by Sharon Mooney, 2006. Image may be re-distributed on condition all original credits are kept intact, for public access image (Sirenian Evolution Chart, white background.)

Sirenians are relatively large herbivorous mammals that inhabit warm, near-shore, marine waters today. They made their first appearance in the early middle Eocene some 50 million years ago. The oldest sirenians known to date come from the early middle Eocene of Jamaica. These belong to two genera and species: Prorastomus sirenoides (Owen, 1855; Savage et al., 1994) and Pezosiren portelli (Domning, 2001). The fossil record documents a gradual transition from amphibious ancestral forms like these, with well developed hind limbs attached to a multivertebral sacrum (Domning, 2001), to living representatives such as Trichechus manatus and Dugong dugon that are fully aquatic and have hind limbs reduced to internal vestiges. Eocene sirenians have a reasonably well documented evolutionary history, and are known from all continents except Australia and Antarctica. Protosiren, classified in the monotypic family Protosirenidae, represents one of the more widely distributed Eocene genera, ranging across the southern part of the eastern Tethys Sea from North Africa (Egypt) to South Asia (Indo-Pakistan). Protosiren is known from skulls and partial skeletons (Abel, 1907; Domning and Gingerich, 1994; Gingerich et al., 1994, 1995). It is distinctive and easily recognized from postcranial elements because thoracic vertebrae have a large oval to keyhole-shaped neural canal, articular surfaces of rib heads are generally roughened rather than smooth (indicating that they were connected exclusively by ligaments or flexible cartilage rather than synovial joints), and ribs lack pachyostosis.

Protosiren is represented by three species described previously (see Figure 1 for geographic distribution). The first, Protosiren fraasi, was named by Abel (1907) on the basis of a well preserved skull and some postcranial remains (first described by Andrews, 1906). These came from the Lower Building Stone Member of the Mokattam Limestone of Cairo (Egypt), which is middle Lutetian in age (early middle Eocene, ca. 45-46 Ma; Gingerich, 1992). The second species, P. smithae, was described and named by Domning and Gingerich (1994). This is a larger species, and it is more derived than P. fraasi morphologically in details of the skull. All known specimens of P. smithae were collected from the Gehannam and Birket Qarun formations in Wadi Hitan (Whales Valley or Zeuglodon Valley), located on the western margin of the Fayum Depression in Egypt. P. smithae is latest Bartonian to earliest Priabonian in age (latest middle to earliest late Eocene, ca. 36-37 Ma; Gingerich, 1992). The third species of this genus, P. sattaensis, was described by Gingerich et al. (1995). This is a large species that is slightly more primitive than P. smithae in having a larger obturator foramen and longer femur (Gingerich et al., 1995, 1997).

Protosiren is distinctive among sirenians in having large keyhole-shaped neural canals perforating thoracic vertebrae, generally having cartilaginous rather than synovial articulations of rib heads, and lacking rib pachyostosis. Protosiren eothene differs from other species of Protosiren in being smaller (anterior thoracic centra are about 10-12% shorter than those of P. fraasi), in having at least partially synovial rib head articulations with vertebrae, and in having well formed but distinctly small rib tubercula relative to the size of the rib heads.
Thoracic vertebrae T1 and T2 are represented by centra only. These are weathered, but otherwise undeformed. The centrum of T1 is hemicylindrical and more nearly the length of T2 than would be expected by comparison with anterior thoracics in later Protosiren. This may imply that the neck and cervical vertebrae of P. eothene were longer than those of later Protosiren.

Thoracic vertebrae of Protosiren

Thoracic vertebrae of Protosiren spp. (Protosirenidae), Eosiren sp. (Dugongidae), and Trichechus manatus (Trichechidae).

  • A-B, T3 and T5 of Protosiren eothene from the early middle Eocene of Pakistan (GSP-UM 3487, holotype).
  • C, T12 of Protosiren sattaensis (GSP-UM 3001) from the late middle Eocene of Pakistan.
  • D, T8 of Protosiren smithae (UM 101224) from the latest middle Eocene of Egypt.
  • E, T5 of Eotheroides sp. (UM uncat.) from the latest middle Eocene of Egypt.
  • F, T3 of Trichechus manatus from the Recent of Florida (UMMZ 106206). Note the large vertebral canal with a keyhole-shaped cross section in Protosiren vertebrae.
    Source: Philip D. Gingrich, New Species of Protosiren (Mammalia, Sirenia) From The Early Middle Eocene of Balochistan (Pakistan)

    Ancestors to Sirenians (dugongs & manatees)
    The ancestors of sirenians are not known. No sirenian-like fossils are known from before the Eocene.

    "Prorastomus is generally intermediate in structure between other tethytheres and later Sirenia, although perhaps it is not directly ancestral to any known later sirenians. Its notable sirenian features include the inflated rostrum, pachyostotic skull, retracted enlarged nares, and five premolars."
    p. 468, Fossil Record, Tethytheres: Sirenians and Desmostylians, R. Ewan Fordyce

    Early Eocene -- fragmentary sirenian fossils known from Hungary.
    Prorastomus (mid-Eocene) -- A very primitive sirenian with an extremely primitive dental formula (including the ancient fifth premolar that nearly all other mammals lost in the Cretaceous).
    Protosiren (late Eocene) -- A sirenian with an essentially modern skeleton, though it still had the very primitive dental formula, possibly split into the two surviving lineages:

  • Dugongs: Eotheroides (late Eocene), with a slightly curved snout and small tusks, still with the primitive dental formula. Perhaps gave rise to Halitherium (Oligocene) a dugong-ish sirenian with a more curved snout and longer tusks, and then to living dugongs, very curved snout & big tusks.
  • Manatees: Sirenotherium (early Miocene); Potamosiren (late Miocene), a manatee-like sirenian with loss of some cheek teeth; then Ribodon (early Pliocene), a manatee with continuous tooth replacement, and then the living manatees.
    Transitional Vertebrate Fossils FAQ

Images of Sirenians, Sea Cows; Dugong and Manatee

Sirenia are the order of placental mammals which comprise modern sea cows (manatee and dugongs) and their extinct relatives. They are the only herbivorous marine mammals now in existence and the only group of herbivorous mammals to have became completely aquatic. Sirenians have a 50 thousand year old fossil record (early Eocene-Recent). They attained modest diversity during the Ogliocene and Miocene, but have since declined as a result of climatic cooling, oceanographic changes, and human interference. Two genera and four species are extant: Trichechus which includes three species of Manatee that live along the Atlantic Coasts and in rivers and coastlines of the Americas and Western Africa. Amazonian Manatee live only in fresh water and Dugongs are found in the Indian and Pacific oceans.

Metaxytherium floridanum
Metaxytherium Floradanum - Early Sirenian
metaxytherium_floridanum2.jpg (500x143 - 19 K)
metaxytherium_floridanum.jpg (750x215 - 40 K)
Based on Encyclopedia of Marine Mammals

Skeleton of Metaxytherium floridanum, a Miocene halitheriine dugongid. Total length about 3.2 meters. After Domning (1988); original image, Journal of Vertebrate Paleontology. Re-illustrated by Sharon Mooney, 2006.
Public Access images may be redistributed, on condition all original credits are kept intact.
Evolution in Sirenian Locomotion
Evolution in Sirenian Locomotion
sirenian_locomotion.gif (500x300 - 16 K)
Based on Marine Mammals: Evolutionary Biology, Annalisa Berta, James L. Sumich
Evolution in Sirenian Locomotion. Re-illustrated by Sharon Mooney, 2006
Public Access images may be redistributed, on condition all original credits are kept intact.
West Indian Manatee
West Indian Manatee
west_indian_manatee.jpg (500x204 - 19 K)
Based on Sirenians of the World
Re-illustrated by Sharon Mooney, 2006
Public Access images may be redistributed, on condition all original credits are kept intact.
West African Manatee
West African Manatee
west_african_manatee.jpg (500x248 - 23 K)
Based on Sirenians of the World
Re-illustrated by Sharon Mooney, 2006
Public Access images may be redistributed, on condition all original credits are kept intact.
Steller's Sea Cow
Steller's Sea Cow
stellers_sea_cow.jpg (500x158 - 16 K)
Based on Sirenians of the World
Re-illustrated by Sharon Mooney, 2006
Public Access images may be redistributed, on condition all original credits are kept intact.
Dugong
Dugong
dugong.jpg (500x191 - 16 K)
Based on Sirenians of the World
Re-illustrated by Sharon Mooney, 2006
Public Access images may be redistributed, on condition all original credits are kept intact.
Amazonian Manatee
Amazonian Manatee
amazonian_manatee.jpg (500x209 - 17 K)
Based on Sirenians of the World
Re-illustrated by Sharon Mooney, 2006
Public Access images may be redistributed, on condition all original credits are kept intact.
Sirenian Evolution Chart
Sirenian Evolution Chart
(Manatee, Dugong, Sea Cows)
sirenians_evolution_graph.gif
(500x881 - 46 K)
Based on Encyclopedia of Marine Mammals
Re-illustrated by Sharon Mooney, 2006
Public Access images may be redistributed, on condition all original credits are kept intact.
Sirenian Evolution Chart
Protosiren Fraasi, 1906, Andrews
protosiren_andrews_1906_750.jpg (750x814 - 149 K)
protosiren_andrews_1906_500.jpg (500x542 - 73 K)
protosiren_andrews_1906.jpg (860x933 - 201 K)
Type specimen of Protosiren fraasi Abel as illustrated, 113 natural size, by Andrews (1906) [CGM 101711. Type is a nearly complete cranium shown here in A, ventral view; C, posterior view; and D, dorsal view. B shows worn surface of right I' tusk (crowns of left and right I' tusks are preserved as casts in NHML and UM replicas of the type made at the turn of the century, but they are no longer preserved in the original type). Reconstruction of premaxillary rostrum shown here is too long and straight (plaster reconstruction, now missing in original type, is shown with crosshatching). Andrews (1906) and Abel (1928) interpreted P4 or dp4 as having multiple roots, but Protosiren is now known to have retained both P4 and P' as single-rooted teeth.
Based on Cranial Morphology of Protosiren fraasi, (Mammalia, Sirenia) from the Middle Eocene of Egypt: A New Study Using Computed Tomography
Public Access images may be redistributed, on condition all original credits are kept intact.
Protosiren Fraasi
Protosiren Fraasi from Egypt
protosiren_750_nolabels.jpg (750x445 - 52 K)
protosiren_750_labels.jpg (750x445 - 61 K)
protosiren_750_5_premolar.jpg (750x445 - 56 K)
protosiren_500_nolabels.jpg (500x297 - 27 K)
protosiren_500_labels.jpg (500x297 - 32 K)
protosiren_500_5_premolar.jpg (500x297 - 29 K)
New reconstruction of type skull of Protosirenfraasi, CGM 10171, with additions from SMNS 10576. Dentary is shown in outline, based on CGM 42297, which may be part of type specimen (see Andrews, 1906). Reproduced ca. 0.45 x natural size. Abbreviations (after Domning, 1978, with additions): AC, alisphenoid canal; AS, alisphenoid; c', upper canine alveolus; EO, exoccipital; FR, frontal; 1' etc., upper incisor alveoli; J, jugal; MI etc., lower molars; MF, mastoid foramen; MX, maxilla; OC, occipital condyle; P1 etc., upper premolar alveoli; PA, parietal; PM, premaxjlla; SO, supraoccipital; SQ, squamosal; SR, sigmoid ridge.
Based on Cranial Morphology of Protosiren fraasi, (Mammalia, Sirenia) from the Middle Eocene of Egypt: A New Study Using Computed Tomography
Re-illustrated by Sharon Mooney, 2006
Public Access images may be redistributed, on condition all original credits are kept intact.
Eotheroides aegyptiacum
Eotheroides aegyptiacum
eotheroides_aegyptiacum_702
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eotheroides_aegyptiacum_500
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Type specimen of Eotheroides aegyptiacum (Owen) as illustrated, natural size, by Owen (1875) [specimen is now catalogued as NHML 467221. Type is a natural stone endocast shown here in A, right lateral view; B, dorsal view; and C, ventral view. Abbreviations are as follows: a, "pons Varolii"; b, anterior myelonal columns; c, limit of posterior myelonal columns;f, falx cerebri; o, optic nerve; r, tramverse ridge separating impressions of basisphenoid and basioccipital; p, pedicle of pituitary body; R, rhinencephalon (olfactory bulb); tr, trigeminal nerves; v, upper vermiform process; x, lateral myelonal columns; 5, prominence anterior to sylvian fissure. Illustration and abbreviations reproduced from Owen (1875).
Based on Cranial Morphology of Protosiren fraasi, (Mammalia, Sirenia) from the Middle Eocene of Egypt: A New Study Using Computed Tomography
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Cranium of Protosiren fraasi
Cranium of Protosiren fraasi
protosiren_cranium_750.jpg (735x1024 - 106 K)
protosiren_cranium_500.jpg (500x696 - 63 K)
Cranium of Protosiren fraasi, A Dorsal, B left lateral, C palatal views
Priem referred his dentary to the same taxon as Andrews' CGM 42297, possibly anticipating that it would look like CGM 42297 when fully adult. Then Priem, citing Abel (1904, 1906), called Andrews' specimen, and hence his own, Protosirenfrmi. Later Sickenberg (1934) considered Priem's dentary "probable" to represent P. fraasi and referred no other dentaries to this species (inexplicably ignoring CGM 42297). Thus small dentaries with very narrow symphyses have come to typify Protosiren (compare Domning et al., 1982, figs. 20, 21, and 34). However, specimens collected in Wadi Hitan (Zeuglodon Valley) in Egypt in recent years show that Protosiren there has a large dentary with large molars, and a wide mandibular rostrum with well-spaced alveoli for all anterior teeth Domning and Gingerich, 1994), while Eotheroides has the smaller dentary with smaller molars and a narrower rostrum (like Priem's dentary). Andrews was correct to place CGM 42297 in the same taxon as CGM 10171, and it might even be part of the type specimen (fide Andrews, 1906, p. 210). Both represent Protosiren fraasi.
Based on Cranial Morphology of Protosiren fraasi, (Mammalia, Sirenia) from the Middle Eocene of Egypt: A New Study Using Computed Tomography
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Sea Cows, Manatee and Sirenia Evolution

Up close and personal with LeVar Burton and injured Manatees. Photographs of Toenails on Manatee, and film clip discussing eating habits and lifestyle of Sea Cows.

  • Origin of Sirenians
    Earliest Sirenians, Prorastomus and Protosiren. Timeline of Sirenian Evolution and Extinctions. Images of the four extant manatee and dugong, and the extinct Steller's Seacow.
  • Sirenian Evolution: Elephant to Sea Cow
    Astonishing photographic evidence of similarities between modern sea cows and elephants. Including photographs with celebrity LeVar Burton from Reading Rainbow.
  • Sea Cows, Manatee and Sirenia Evolution
    Up close and personal with LeVar Burton and Manatees video. Photographs of Toenails on Manatee, and discussing diet, eating habits and lifestyle of Sea Cows.
  • Images of Sirenians
    Available for download and public distribution for educational purposes.

Sam the Sea Cow about an injured Sea Cow rescued by marine biologists.
Celebrity host, LeVar Burton examines a Sea Cow close up revealing it's traits in common with elephants.
Sam The Sea Cow, WMV / Flash Format / Duration - 3:06
© 1992, Reading Rainbow
RR is a production and registered trademark of GPN/Nebraska Educational Telecommunications and WNED-TV, Buffalo NY

Sirenian Evolution: Elephant to Sea Cow (Manatees)
Astonishing photographic evidence of similarities between modern sea cows and elephants. Including photographs with celebrity LeVar Burton from Reading Rainbow.

manatee
Manatee have a large beaver-like tail used to propel their 1000-2000 lb bodies.
manatee
Manatee are "gentle giants", whose greatest natural enemy, is man. Curious manatee are often injured by boat propellers. LeVar Burton speaks with the professionals who work with injured sea cows, and gets up-close with the manatee. Like all other mammals, the sea cow has hair covering its body.
manatee
Manatee have finger-like appendages that "grab food", similar to how the elephant uses its trunk.
manatee
manatee
manatee
Manatee have tiny valves protecting their nostrils, as they graze on vegetation under water. Sea Cows return to the surface every 3 to 5 minutes to breathe.

And.. like elephants, Manatee have toe nails on their flippers.

Some of them have even lost their toe nails, and developed smooth paddles like Cetaceans.

"The smallest member of the family Trichechidae, the Amazonian manatee has smooth skin and no nails on its flippers and feeds on freshwater vegetation."

Manatee Toe Nails

Manatee Toe Nails

Manatee Toe Nails

Manatee Toe Nails

Manatee Toe Nails

Manatee Toe Nails

Manatee Toe Nails

MORE LINKS ON SIRENIAN EVOLUTION