Catie Willard and Lindsey Baumoel

Question???How have whales

physiologically evolved from land to water?

Whale Video

PakicetusThree genera:

Pakicetus, Nalacetus, and Ichthyolestes

Eocene Kuldana Formation of Pakistan

Evidence of Fossils

Ambulocetus47-48 million years

agoWell developed fore-

and hind-limbsSwam by pelvic

paddlingHind feet large, with

elongated, flattened toes suggesting webbed feet and the ability to walk on land

DorudonLate-middle EoceneSmaller dolphin-

sized animalsSkeletal morphology

of caudal regionNo sacrum and

floating pelvis

Basilosaures40 to 34 million years

agoHind limbs to short to

support body mass18 meters (60 feet)The hind limbs had

fused tarsalsAbsence of

articulationPossible functions of

limbs

Mysticeti and OdontocetiMioceneHave baleen teeth

used for filter-feeding

Very large and do not dive to great depths

Typically smaller than baleen whales

Have teethSwim rapidly and

dive deep

Molecular EvidenceFive mitochondrial DNA sequences and eleven nuclear-

encoded protein sequences aligned from Cetacea, two Artiodactyl suborders and an outgroup

Cetacean DNA sequences from Finback WhaleProtein sequences come from different whales depending

on who the sequence was known for in each of the eleven proteins

Maximum parsimony and maximum likelihood where the methods of reconstruction used for alternative phylogenetic trees

Only transversions were looked at for the DNA sequencesStatistical tests Cow-Pig Cow-Cetacean Pig-Cetacean

PARS 641 624 641

ML 0 89 11

Molecular EvidencePROTPARS was used to calculate the number

of amino acid replacements required for each alternative tree

The reliability of these tests was determined by bootstrap re-sampling of parsimony and several other tests; for DNA sequences the max-likelihood trees were also tested by bootstrap re-sampling

ResultsTree one is the presently accepted taxonomic

schemeThe DNA data using max parsimony and max

likelihood combined with bootstrap resampling gives tree II

For protein sequences the traditional tree was not supported by any of the tests; the only significant support was for tree II

Works CitedBejder, Lars and Brian K. Hill. 2002. Limbs in whales

and limblessness in other vertebrates: mechanisms of evolutionary and developmental transformation and loss. Evolution and Development. 4(6): 445-458.

Gingerich, Philip D. 2003. Land-to-sea transition in early whales: evolution of Eocene Archaeoceti (Cetacea) in relation to skeletal proportion and locomotion of living semiaquatic. Paleobiology. 29(3): 429-454.

Gingerich, Philip D. 1998. Paleobiological perspectives on Mesonychia, Archaeoceti, and the origin of whales. Paleobiology. 423-446.

Works Cited cont’dGraur, D. and Higgens, D. 1994. Molecular

evidence for the inclusion of cetaceans within the order artiodactyla. Mol. Biol. Evol. 11(3): 357-364.

Thewissen, J. G. M., Hussain, S. T., and Arif, M. 1994. Fossil evidence for the origin of aquatic locomotion in Archalocete whales. Science. 263(5144): 210-212.

Thewissen, J. G. M, Williams, E. M., Roe, L. J., and Hussain, S. T. 2001. Skeletons of terrestrial cetaceans and the relationship of whales to artiodactyls. Nature. 413: 277-281.