Marine Bio: Phylogeny and Evolution

Studying the Evolution of Marine mammals

  • Extant species - living species

  • Fossil records

  • anatomical connection

  • genetic connection

Convergent evolution

  • Homology -similar structure due to ancestry

    • Common ancestor

  • Homoplasy -similar structure due to the environment

    • They don’t share ancestry

    • Feature evolve independently due to their environment (convergent evol.)


  • Left - convergent

    • Shared trait not ancestry

  • Right - homoplasy

  • Uses the 3 sources of data to make a strong hypothesis (fossils, autonomy, genetics)

  • Sister taxa = connected by a single common ancestor

Monophyletic - share a common ancestor

Polyphyletic - descend from diffrent linages

All Epoch era

  • Ecocen

    • first whales (cetaceans and sirenians)

  • Oligocene (late)

    • first seals (pinnipeds)

  • Pleistocene

    • first mammals (sea otters and polar bears)

Separate the phocates from otiradea and odbenidea

  • H1 Diphyletic Evolution: originated from 2 carnivore

    • Primitive anatomical features of otariids

    • Separate locations of earliest fossil phocids and otariids

All pinnipeds have the same common ancestor

Closest relative to all 3 is bears (Ursidae)

  • H2 Monophyletic Evolution: single common ancestor

    • Unique morphological features in all 3 families

    • Similarities in molecular biology of otariids and phocids

Evolutionary Origins of Pinnipeds

Monophyly -supported

Closest relatives of pinnipeds - Arctoid carnivores:

  • Ursidae (bears)

  • Mustelidae (weasels, otters, skunks)

Family Enaliarctidae -Earliest Pinnipeds

  • End of Oligocene

  • Elongated fore and hind limbs for aquatic living

  • Longer hind limbs (tibia and fibula) than current pinnipeds

  • Heterodont dentition

    • different types of teeth. Specialized teeth for different purposes

  • Modern day have homodont dentition (same teeth)

  • Earliest family of pinnipeds but may not be an ancestor of pinnipeds. This is a debated topic. On page 3 they are separated out as their own family

Family Desmatophocidae

  • Early to mid-Miocene

  • Homosont dentition

    • single point cone-shaped

  • Large and sexually dimorphic

Enaliarctidae, Otarildae, Odobenidae, Desmatophocidae, Phocidae

Phylogeny of Sirenians

  • Sirenians

    • manatees and dugongs

  • Desmostylia

    • only extinct order of mammals

  • Closest living relatives to sirenian are Proboscidea

  • All are in the monophyletic group Tethytheria

    • Come from the Thethyla sea

First Sirenians

  • Family Proastomidae

    • Well-developed legs with thick bones.

    • Dense bones prevent floating in water and allows then to wade in water but legs allude to them being amphibious. (Like hippos)

  • Protosirenidae (reduced hindlimb)

    • amphibious with reduced/weaker hind limbs

    • Middle Eocene

  • Eosirenidae (vestigial hindlimb)

    • loss of hind limbs (tiny vestigial bones left)

    • Late Eocene