Paleontology 1

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PaleontologyDavid L. Dillon, M.Sc.

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The Study of Ancient LifeThe major difference between modern forensics and paleontologic technique involves the age of the specimen/victim.Other differences include species of study and modes of preservation.The environments in which these plants and animals lived and died have evolved, both gradually and catastrophically according to the available evidence.

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Modes of PreservationEvidence of previous life occurs in roughly six modes:

Complete/actual preservation Replacement Permineralization/petrifaction Recrystallisation/alteration Moulds and Casts Traces of activity

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Complete/actual preservationComplete/actual preservation -the remains are unchanged except for degassing, dehydration and/or freezing.In the case of molluscs, it is often easy to see the nacreous, or mother-of-pearl lustre of the original shell material.

Paleontology 2

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Complete/actual IIProbably the best vertebrate examples are Pleistocene mammal remains. 1 is mammoth hair. 2 mammoth molars partially overrun by moss and other vegetation. 3 the mastodon remains at Hyde Park, New York. 4 cave bear canine teeth.

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Complete/actual IIIFeb. 5, 2003 - “We consider these cells conditionally alive', explains Professor Vladimir Repin, leader of the research team, 'because they were fixed in formalin to preserve after extracting them from the mammoth body in the field. However, the inner structure of these cells is undamaged, so we suggest that the rest frozen tissues contain similar cell layers, which could be defrozen'. The sensational finding was made by Oleg Taranov, a member of the research team.Many of such remains are roughly 20,000 to 25,000 years in age. That’s relatively young in terms of earth’s history.

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ReplacementThis is when the original hard or soft parts are replaced by another material. For example, internal organs may sometimes be replaced by pyrite, while quartz, calcite, pyrite and other minerals may replace hard parts.

These are all silicified molluscs. The original shell was aragonite. It is now quartz.

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Replacement IIThese are creatures from the “Burgess Shale Fauna” -preserved as pyrite-replacement of soft parts of twochancelloriidsand a sponge.

Paleontology 3

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Permineralization/petrifactionThis occurs when the original organic material is permeated with a soluble mineral that precipitates into the pore spaces of the fossil. Examples include most petrified wood, dinosaur bones and coprolites.Sometimes this kind of evidence is not for the squeamish.

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Permineralization/petrifaction IIYes Virginia, this really is what it looks like!

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Permineralization/petrifaction IIIThis photomicrograph shows partially digested bone from within the coprolite. Good evidence that this dung came from a large carnivore or scavenger.

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Recrystallisation/alterationRecrystallisation/alteration - aragonite commonly forms due to biological precipitation of CaCO3. Because it is chemically metastable, it tends to recrystallise to form calcite. When this happens, the pearly/nacreous lustre is lost. When plant material decays it tends to alter leaving only a carbon-rich component behind.

Paleontology 4

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Recrystallisation/alteration IIRecrystallisation also results in loss of the original colour. On the left is the relatively unaltered shell of a cephalopod. The specimen on the right is recrystallised.

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Recrystallisation/alteration IIIA living fern and altered remains of a fern manifest as a carbon film.

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Moulds and CastsMoulds are formed when the hard parts are surrounded and/or in-filled by soft sediment that hardens and the hard original bone or shell is subsequently dissolved. Casts are formed by the later infilling of the mould.

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Moulds and Casts II1 is an internal mould of a snail.2 is a coiled cephalopod with sediment filling chambers which would be gas or liquid filled when the animal was alive. Therefore this exhibits two kinds of preservation: recrystallised shell and internal moulds attached to the shell remains.

Paleontology 5

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Traces of activitySometimes the life activities of an animal are preserved in the form of tracks, burrows, or impressions. In some cases this is all that is known of a species because the animal had few hard parts. 1 – footprints of a vertebrate in sandstone. 2 –burrows of one or more invertebrates.

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Kinds of PreservationWhat is the mode of preservation of P-1?

What is the mode of preservation of P-2?

What is the mode of preservation of P-3?

What is the mode of preservation of P-4?

Shell now scratches glass

Pores in filled; now scratches glass

Mother-of pearl lustre

Void space where skeleton used to be.

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PaleoecologyThe appearance of fossil assemblages can help to determine something about the environment and occasionally a relationship between two species. In this case, the palm frond indicates that the fish lived in a tropical to subtropical environment, (not that fish lived in trees).

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Paleoecology II

"You've got bite marks, embedded sharks' teeth - it's really the smoking gun for feeding behaviour that hasn't been documented before," says Mike Everhart, an adjunct curator at the Sternberg Museum of Natural History in Hays, Kansas.

Paleontology 6

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Paleoecology IIIMastodon and mammoth remains have been found throughout the arctic and temperate world.Based on the the crowns of their molars, it has been established that mammoths (1) ate leaves, while mastodons (2) ate woody plant material.

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Assignment NotesQuestions 1 through 6 can be answered by looking at the fossils and posters in the case facing the stairs in the foyer of B&G.

Questions 7 and 8 can be answered by looking in the case next to the south entrance to the east hall.For questions 9 to 12, look for the specimens and salient information in the case south of room 123.