BIO358 1st Edition Lecture 6 Outline of Last Lecture I Definition of Phylogeny A Monophyletic clades B Paraphyletic clades C Polyphyletic clades II Clade Handout Notes III Identifying Monophyletic Groups a Investigate characters b Group them together based on similar characters IV Synapomorphies vs Convergent Characters V Pinniped Evolution VI Cetacean Evolution Outline of Current Lecture I Artiodactyls synapomorphy II Pakicetus oldest known cetacean III Ambulocetus IV Graut and Higgens 1994 V Shimamura et al VI Reconciling molecular and fossil data a 2001 new fossil of Pakicetus Current Lecture Until 2001 Cetaceans are most closely related to mesonychids Artiodactyl even toed ungulates Synapomorphy shared in ankle Astragalus has specialized feature that limits ankle movement and limits the mobility of the joint while elongating the leg Specialized astragalus Synapomorphy of artiodactyls Earliest know cetacean Pakicetus oldest known Gingerich discovered 1983 These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Found in Pakistan Eocene mammals 55 65 million years ago amphibious No preserved hindlimbs teeth similar to mesonychids 1983 called it a relative of mesonychids Thewissen 1994 walking whale Ambulocetus natans possessed cetacean bulla more bone limb elements in skeleton Ambulocetus sea lion sized moveable wrists and ankles large hands and feet hypothesized to swim like an otter by undulating verterbral column and hind limbs walked on land like a sea lion or fur seal no ankle bones could be described had teeth like a mesonychids Thewissen calls it a relative of mesonychids Fossil evidence tells us Close relationship between cetaceans and mesonychids Uninformative about relationship beween cetaceans and artiodactyls because we don t have any ankle bones Plan B Molecular data ABSOLUTELY says that cetaceans are most closely related to artiodactyls In 1994 Graut and Higgens Sampled o Mitochondrial genome o Nuclear genome Artiodactyls o Cow o Pig o Camel Cetaceans o Mysticetes o Odontocetes Shimamura et al Used S I N E s short interspersed elements Regions of the host genome where viral RNA has been incorporated into host genome High quality marke probablilit of Independent insertions occurring in the same place in the Same place in different groups clades almost Zero Fossil evidence shows cetaceans are most closely related to mesonychids Molecular data shows cetaceans are most closely related to artiodactyls How do we reconcile the two views Fossil evidence was uninformative for relating cetaceans to artiodactyls Only skull bits from pakicetus and no ankles from ambulocetus ALL CHANGED IN ONE WEEK in 2001 Gingerich on science and Thewissen in nature Pakicetus fossil found by Thewissen that INCLUDED ANKLE BONES Back of brain case with bulla Vertebrae found Pelvic element Long bones Ankle bones with specialized astragalus Now both fossil and molecular data support a close relationship between artiodactyls and cetaceans