Upload
hoangtram
View
236
Download
0
Embed Size (px)
Citation preview
Evolution of Pinnipeds and Sirenians
Cladis'cs • Phylogeny
– Hypothesis about evolu'onary rela'onships • Clades
– Groups of related taxa and their descendants
Cladistics • Character
–Diverse, heritable attributes
–Used in phylogenetic analysis
• Character state –Condition expressed in the individual
• Limb number (0,2,4,6,8) • DNA sequence (GGGAATT)
Origin of Features • Homologous structures
Similar features resulting from common ancestry • Bones of a flipper & hand
Origin of features
• Analogous structures structures with similar func'on that evolved separately Convergent evolu'on e.g. wings of a bat & bird
• Parsimony fewest evolu'onary steps/changes is accepted as the best
Tools used to study evolution Bones and Teeth
• saved in fossil record • structure used to infer diet (ecology)
• limbs, pelvis - shows how animal moved
Tools used to study evolution
Immunology
• similar response shows relatedness
• used with extant species
Biochemistry & Molecular tools
• DNA sequencing
• DNA recombinations – more connections shows relatedness
Mammalian Tree
Marine mammals: monophyletic group?
Malcolm A. Ferguson-Smith & Vladimir Trifonov Nature Reviews Genetics 8, 950-962 (December 2007)
NO
CONVERGENT
evolution from land to sea
Triassic // 200 million years ago
Wildman D E et al. PNAS 2007;104:14395-14400
Laurasiatheria /Cetartiodactyla (cow)
Afrotheria (elephant) Xenarthra
(armadillo)
Euarchontoglires (monkey)
Order Carnivoria Includes 5 Families of Marine Mammals Mustelidae – Sea otter Ursidae – Polar bear Phocidae – Seals (true seal) Otariidae – Sea lions (eared seals) Odobenidae - Walrus
Pinnipeds
MARINE MAMMAL EVOLUTION
Pinniped Evolution Diphyly: Fossil & morphological support Monophyly: molecular & revised morphological support
Bear Pinnipedimorph Otariid Odobenid Phocid
Pinniped Skeletal Morphology
Chronological Ranges for Marine Carnivora
Puijila t
Pinniped Evolution When & where?
• 27-25 mya (late Oligocene)
• N. Pacific and Canadian Arctic
• Arctoid ancestors (bear like)
Puijila darwini Enaliarctos spp.
N Rybczynski et al. Nature 458, 1021-1024 (2009) doi:10.1038/nature07985
Puijila darwini skeleton (NUFV 405, holotype).
Enaliarctos spp.
Pinniped Cladogram
Divergence of Early Otariids
• Pithanotaria spp. • 11 mya (late Miocene), CA
• Thalassoleon spp. • 8-6 mya, CA, Mexico, & Japan
• Callorhinus • 5-4 mya, extant
Present day Otariids
Precursor to Phocids
• Desmatophocidae – 21-20 mya
• derived from Enaliarctos
• not true phocid but evolutionary link
• N. Pacific coastal (CA, OR, Japan)
• Large, sexually dimorphic
• Allodesmus & Desmatophoca
Early Phocids
• Monotherium spp. & Leptophoca spp.
• 15-14 mya
• Appeared in N. Atlantic
• Split into many lineages
Monotherium & Leptophoca
Desmatophoca
Moved through Central American Seaway or through the Arctic Basin
Present day Phocids
Early Odobenids • Relationship to Otariids & Phocids
unclear
• Very diverse group (3 suborders)
• Proneotherium & Neotherium spp.
• Ancestral walrus 16 mya & 14mya
• Eastern N. Pacific
• Fish eaters
Modern Odobenids
• Evolved in N. Atlantic
• Prorosmarus, early Pliocene
• Re-invaded Pacific through Bering Strait ( < 1mya)
• Odobenus rosmarus
Order Sirenia
• Family Dugongidae
• Family Trichechidae – Manatees
Sirenian EVolu'on Sirenian
Evolu'on • Caribbean region
• Herbivorous mammals
Sirenia Evolution Earliest Ancestors:
• herbivorous mammals
• 50 mya, Caribbean region
Sirenian evolu'on • Prorastomas – early Eocene (50 Ma), Jamaica
– Long trunk, rela'vely short legs – 4 sacral vertebrae: increased flexibility -‐ undula'on – Strong and long tail – Par'ally aqua'c
Order Sirenia Sirenians, proboscideans (elephants), & desmostylians (ex'nct) termed Tethytheria
Order Desmostylia
• Only extinct order of marine mammal
• N. Pacific, Late Oligocene (33-10 Ma) • 10 species
• hippopotamus-like amphibious quadrupeds
• Paleoparadoxia & Desmostylus Most closely related to elephants
Unique Teeth Structure: