Pinniped and Sirenian Systematics and Evolution John Hildebrand SIO 133 Marine Mammal Biology. With Contributions from Douglas Krause

Transcription

1 Pinniped and Sirenian Systematics and Evolution John Hildebrand SIO 133 Marine Mammal Biology With Contributions from Douglas Krause

2 Pinniped and Sirenian Evolution

3 Pinniped Evolution

4 Pinniped Evolution

5 Pinniped Evolution Oligocene (20 30 Ma) ACC open, Antarctic glaciation Global temperature depression Arctic remains ice-free Enaliarctos appears in the N. Pacific Late-Oligocene warming and de-glaciation Adapted from M. Goebel

6 Pinniped Evolution

7 Pinniped Evolution Miocene (7 20 Ma) Early warm period Sirenian and Odebenid radiations Late rapid cooling, ACC strengthens Re-glaciation of Antarctic Phocid and Otariid radiations Adapted from M. Goebel

8 Pinniped Evolution Pliocene (1.8 7 Ma) Continued global cooling, increased seasonality Formation of modern climates and ocean circulation Central American Seaway (Panama) closes Arctopcephalus (fur seals) appear Adapted from M. Goebel

9 Pinniped Evolution

10 Pinniped Evolution 2 models Monophylytic 1 re-invasion, molecular and revised morphological Dyphylytic 2 re-invasions, morphological

11 Pinniped Skeletal Morphology Bear Pinnipedimorph Otariid Odobenid Phocid

12 Pinniped Characters Pinniped Evolution Maxilla contributes to orbital wall Short, robust humerus with large crest Lengthened phalangies Fore emphasized digit I Hind emphasized digits I and V

13 Pinniped Evolution When & where? mya (Oligocene) N. Pacific and Canadian Arctic Arctoid ancestors (bear like) Puijila darwini Enaliarctos spp.

14 Pinniped Evolution Puijila darwini Arctic otter or early pinniped mya Berta 2012

15 Pinniped Evolution Enaliarctos spp. Well-derived early pinniped Late Oligocene, eastern N. Pacific small animal, terrestrial dentition size of harbor seal

16 Pinniped Evolution Modified fore and hind flippers Marine amphibious Teeth: shearing cuspids (terrestrial) 4 known spp Enaliarctos spp. Berta mya

17 Pinniped Evolution Berta 2009

18 Early Otariids Otariid Evolution Pithanotaria spp. 11 mya (late Miocene), CA Thalassoleon spp. 8-6 mya, CA, Mexico, & Japan Callorhinus 5-4 mya, extant

19 Present day Otariids

20 Phocid Evolution Desmatophocidae mya Precursor to Phocids Berta 2006

21 Desmatophocidae Phocid Evolution Distributed around N. Pacific Derived from Enaliarctos Elongated skull, large body Forelimb swimming (basal character) Two genera Allodesmus and Desmatophoca

22 San Diego Museum of Natural History: Allodesmus

23 Desmatophoca Phocinae Probably Moved via Central American Seaway ~ 15ma

24 Acrophoca longirostris Stem Phocid from the Miocene of Peru From Berta 2012

25 Phocid Evolution

26 Early Odobenidae Odobenid Evolution Best evidence: sister taxa to otariids Last common ancestor ~ 20 ma Extremely diverse group! 14 genera, 20 species N. Pacific origin, wide distribution

27 Early Odobenidae Widely tropical Smaller body size Fish eaters No tusks early on Odobenid Evolution

28 Odobenid Evolution

29 Modern Odobenidae Odobenid Evolution Single species: Odobenus rosmarus Evolved in the N. Atlantic Re-invaded the N. Pacific via the Bering Straight (< 1 Ma)

30 Berta Encyclopedia of Marine Mammals 2 nd Edition

31 Pinniped Evolution Kovacs et al. 2012

32 Pinniped and Sirenian Evolution Desmostylia

33 Sirenian Evolution

34 Sirenian Evolution

35 Sirenian Evolution

36 Sirenian Evolution Prorastomas early Eocene (50 Ma), Jamaica Long trunk, relatively short legs 4 sacral vertebrae: increased flexibility - undulation Strong and long tail Partially aquatic

37 Sirenian Evolution Oldest fossil record ~ 50mya Herbivorous Tropical/warm water

38 Sirenian Evolution Family Dugongidae (Dugongs) Family Trichechidae (Manatees)

39 Sirenian Evolution Over 25 species during mid-miocene Velez-Juarbe J, Domning DP, Pyenson ND (2012)

40 Desmostylian Evolution

41 Desmostylian Evolution Hippo-sized amphibious quadraped Only extinct order of MM ~33 10 mya 7 genera and 12 species/ 2 families Distribution in cool waters of N. Pacific

42 Desmostylian Evolution Ecology (hypotheses) ~33 10 mya Upright posture forelimb swimming Stable isotopes suggest herbivorous diet Distribution and limited diversity suggest limited ecological flexibility

43 Desmostylian Evolution Desmostylia = ( bundle of pillars )

44 Desmostylian Evolution

45 Desmostylian Evolution