Evolution of Life and the Atmosphere

Transcription

1 Evolution of Life and the Atmosphere

2 White board used for Evolution of the Atmosphere and Early Evolution of Life

3 The Pitfalls of Preservation It is obvious that a major change occurred in the Earth s metazoan biota by Cambrian time (particularly in the development of skeletal tissue). But while skeletal remains give us some indication of the magnitude of change that occurred in the earliest Phanerozoic, the perils of fossil preservation prevent us from seeing the entire biota (both skeletonized and soft-bodied). But we do have a window shortly after this (Middle Cambrian). This window is the Burgess Shale Lagerstätte.

4 What is a Lagerstätte? (I think, you will write it without the.. ) Konservat preservation Lagerstätte treasure house Konservat Lagerstätte a location or stratigraphic unit with unique and remarkable preservation of fossils Fossils may be uncommonly abundant or rare Fossils are typically articulated Soft tissues may also be preserved

5 Charles D. Walcott Discoverer of the Middle Cambrian Burgess Shale Lagerstätte

6 Burgess Shale, Yoho National Park, B.C. Exceptionally preserved soft-bodied organisms Middle Cambrian age ( shortly after the Cambrian Explosion)

7 Burgess Shale, Yoho National Park, B.C. snapshot of life assemblages (in general, fossil record only preserves hard parts of organisms) Surprisingly diverse assemblage with very unusual forms...

8 Vauxia sp. Vauxia -sponge Vauxia forest with Leanchoilia

9 Wiwaxia sp. A worm, a mollusc, or something completely different?

10 Marella sp. An early arthropod (presumably related to trilobites) Marella caught in the act of molting

11 The great Hallucigenia flip-out

12 Hallucigenia sp.: presently classified as onychophoran Hallucigenia Modern velvet worms (onychophorans): in tropical rainforests

13 Pikaia sp.: one of the earliest known Chordates

14 Pikaia sp.: one of the earliest known Chordates

15 Sanctacaris sp. (Santa Claws) An undoubted arthropod (A Chelicerate without chelicae!?) Subphylum Chelicerata includes: spiders, mites, ticks scorpions,horseshoe crabs all having feeding appendages called chelicae

16 Sanctacaris sp. (Santa Claws)

17 Opabinia sp.

18 Opabinia sp.

19 Aysheaia sp.

20 Habelia sp.

21 Dinomischus sp.

22 Nectocaris sp.

23 Odontogryphus sp.

24 Ottaia sp.

25 Sidneyia sp.

26 Anomalocaris: A Case of Mistaken Identity Anomalocaris: An unusual shrimp-like arthropod?

27 Anomalocaris: A Case of Mistaken Identity Peytoia... a jelly-fish?

28 Anomalocaris: A composite of components previously believed to be separate organisms (Peytoia) (Peytoia) (Original Anomalocaris)

29 Anomalocaris oblique views of a cephalon grasping appendage eye mouth

30 Anomalocaris - reconstruction... THE top-predator in the Burgess community!

31 Anomalocaris - reconstruction

32 Anomalocaris an example of systematic palaeontology

33 Anomalocaris and its systematic relatives: Amplectobelua symbrachiata

34 Anomalocaris and its systematic relatives: Anomalocaris saron

35 Anomalocaris and its systematic relatives: Parapeytoia sp.

36 Anomalocaris and its systematic relatives: Lagenia cambria

37 Anomalocaris and its systematic relatives: Anomalocaris canadensis

38 Anomalocaris and its systematic relatives: A function-morphological comparison between Lagenia cambria Anomalocaris canadensis

39 Summary: The Burgess - community

40 The Burgess habitate

41 Chengjiang Fauna A similar Burgess Shaletype biota has since been found in the Chengjiang County, Yunnan Province, China. Yu'anshan Member of the Heilinpu Formation. These fossils are about 525 ma (Early Cambrian), and therefore slightly older than the Burgess Shale fossils.

42 Haikouella lanceolata Of major importance in the Chengjiang biota is the occurrence of a chordate named Haikouella (this is older than Pikaia, which was previously declared to be the oldest chordate). It is decidedly lamprey-like, indicating the appearance of jawless, fish-like chordates by the early Cambrian (even though the oldest definite remains of jawless fish date to the Early Ordovician)

43 Haikouella lanceolata: first known chordate!!

44 Note differences in community structure!! Ediacaran marine community Cambrian marine community All suspension feeders (or at least passive food gatherers) Carnivores, Suspension feeders, Deposit feeders, The first arms race!

45 END OF SESSION