Lecture 19 Flashcards
Are graptolites considered to be solitary or colonial animals?
Colonial
Graptolite meaning
Written marks on shale
Graptolite preservation
Generally preserved as flattened carbonized or kaolinite films
Graptolite composition
Chitinous exoskeleton
Graptolite morphology
Colony of tiny interconnected organic tubes (thecae)
Each animal was a zooid
Colony = rhabdosome
Graptolite ecology
Suspension feeders; some benthic, some planktonic
2 classes of graptolites
Graptoloidea
Dendroidea
Graptoloidea stratigraphic range
Ordovician-Devonian
Dendroidea stratigraphic range
Upper Cambrian-Carboniferous
What are special about graptolites?
Index fossils, widely used in biostratigraphy
Dendroid graptolites features
Multi-branched (stipes)
Connecting links between stipes (dissepiments)
Branching growth (dendritic)
Theca = zoecium (houses zooids)
Graptoloid graptolites features
Rhabdosomes formed by a single type of theca (tube)
Arranged in stipes (branches)
Theca may be arranged on one side of the stipe or on both
No disspeiments
Graptoloid graptolite ecology
Low energy environments, often preserved in gray or black shales
Usually planktonic
Conodont elements
Tooth-like microfossils
Conodont stratigraphic range
Late Cambrian-Late Triassic
Conodont origin
Tooth-like structures are the mouthparts of a hagfish-like animal
Conodont element composition
Calcium phosphate
What do a variety of conodont elements form?
Conodont apparatus within a single animal
3 basic forms of conodonts
Cones
Bars
Platforms
Scolecodonts
Fossils with similar overall appearance to conodonts, but very different composition
Scolecodont origin
Jaws of polychaete annelids
Scolecodonts composition
Composed mostly of chitin
Generally degraded to kerogen
Scolecodont stratigraphic range
Cambrian-recent
