History & Evolution of Life on Earth

crinoid phylogeny

Bilateral deuterostomes, Phylum Echinodermata, aka sea lillies, the only extant class of pelmatozoans

pelmatozoans

attached echinoderms

crinoid range

Lower Ordovician-today, dominate Palaeozoic shallow marine

crinoid feeding style

filter feeding sessile benthos

crinoid anatomy

upper theca is the main body formed by interlocking calcite plates and housing all the main functional components, it is divided into lower calyx/cup and and upper tegamen

how to crinoids feed

arms & tube feet extend to form a filter feeding mesh, branchial arms open like an umbrella and the pinnule armlets lined with the tube feet are sticky w/ secreted mucus to increase the surface area

rheophilic

most modern crinoids, actively exploit water currents for feeding, exist in relatively shallower conditions orientating their filtration fan to increase their feeding efficiency

rheophobic

rarer, avoid strong currents, when feeding lay with arms outstretched to form collecting bowl

bryozoa

bilateral protostomes, of the Lophotrochozoa clade

bryozoa range

appear in ordovician, could have been in cambrian

bryozoan structure

tiny zooids living w/in mineralized colonial structure called a zoarium gen made of calcite

bryozoan zooids

polymorphic & specialized for feeding & excretion & sometimes reproduction & defense

bryzoan body anatomy

polypide feeding unit & cystid body wall w/ exoskeleton

bryozoan polypide

consists of a lophophore, U-shaped gut & reproductive organs

bryozoan cystid

body wall made up of epithelial tissue which secretes skeleton of a tubular or box like shape

bryozoan colony types

meshwork, dendroid, short & robust branches

where are bryozoan colonies found

all are epibenthic attached to substrate, often in carbonate shelf areas & reefs sensitive to sediment accumulation

reticulate meshwork colonies of bryozoa

generate incoming & outgoing water currents for both feeding and waste disposal

flat (adnate) bryozoa colonies

encrusting, water flows between colony’s surface & base of lophophores out to margins of the colony

cylindrical or bifoliate erect bryozoa colonies

autozooecia budded from an axis or median lamina, zooecial chambers are short & some have internal partial partitions called hemisepta

major assemblages of Ediacaran fossils

Avalon 580-560 Ma, White Sea 555-550, Nama 545-542

avalon assemblage

oldest, found in Newfoundland Canada & Charnwood Forest UK, limited eco & morpho diversity, Charnia, Kimberella, deep (marginal slope & basinal) turbiditic successions

white sea assemblage

offshore & shoreface facies, most diverse, range of lifestyles, Dickinsonia & Spriggina, Ediacara hills 1946 Aus Flinders Ranges

nama assemblage

youngest & least diverse, globally restricted, Tsaus Mtns Namibia, indications of post-extinction & increasing specializations

wormworld

Nama, potential transition period to Cambrian biota

Cambrian animal ecology changes

predation (Cloudina), bioturbation, reefs, new body plans, more penetrative burrows, new efficient feeding strategies, recorded by trace fossils

Cambrian animal ecosystem engineering

increased depth, further extent of bioturbation, deep tiering, suspension & detritus feeding

Dickinsonia fossil

early evidence of bilaterian traces of grazing & resting

Cloudina anatomical adaptation

Neoproterozoic biomineralized skeleton

advent of biomineralized skeletons

primary biominerals are calcium carbonate, calcium phosphate & silica, allowed for support in muscles of echinoderms & vertebrates, attachment in sponges & corals, enclosing filter chambers & increased protection from predators

similarities between brachiopods & bivalves

filter feeding, Lophotrochozoa, appear in Cambrian, bivalved with two shells

general diffs between brachiopods & bivalves

phylum, internal anatomy, external symmetry, shell composition

brachiopod external morphology

calcareous or chitinophosphatic, marine sessile, asymmetrical, raised portion of valve (fold), opposite depression (sulcus), inarticulate or articulate valves

brachiopod internal structure

lophophore inside valve & composed of 2 symmetrical brachia arms, it is supported by calcareous brachidium attached to inside of brachial valve, sometimes a spiralium, teeth & sockets interlocking hinge structures of pedicle (ventral) valve

mollusc characteristics

bilateral, unsegmented soft bodies, most have external shells or at least 2ndarily lost them

bivalve external morphology

symmetrical calcite or argonite shells formed from the skin-like layer of the mantle, mostly marine but can be freshwater or even terrestrial, valves connected by hinge & ligament, anterior smaller than posterior

bivalve internal morphology

mantle creates mantle cavity, contains visceral mass - tissue holding internal organs, muscular foot for crawling burrowing or growing limbs

brachiopod marine zone

after pelagic larval phase, settle to sea floor, inter-tidal to deep ocean, infaunal, quasi-infaunal or epifaunal

infaunal brachiopods

buried, pedicle for stability oriented posterior downward, only genus is Lingula

quasi-infaunal brachiopods

float on or partially w/in sediment, pedicle lower valve, concavo-convex or plano-convex shape, increased surface area & spines, pedicle opening often not present

epifaunal brachiopods

librosessile or fixosessile

librosessile brachiopods

epifaunal, sit on top of sediment, pedicle foramen closed in most, dish like, large SA, platforms & wings for support

flexosessile brachiopods

peduculate gen attached to firm substrates, if soft they have bods to deal

bivalve lifestyles

infaunal, epifaunal, boring & cavity dwelling, free-lying, swimming

epifaunal bivalves

e.g. mussels or oysters, attach to substrate w/ byssus made up of protein filaments or cemented

infaunal bivalves

shallow & deep burrowing, smooth thin-shelled in low e enviros, ornamented thick high e enviros, siphons formed by mantle edge for feeding, respiration & excretion, forms w/ posterior ‘gape’ cannot fully retract their siphons

bivalve pallial line indations

entire line - short siphons, pallial sinus - long siphons

increased success of bivalves

Ordovician major radiation, Devonian freshwater forms, 2nd major radiation Triassic, displaced brachiopods Mesozoic, PTME, more diverse diet, habitats, motility etc, adapted & filled niches

Permian Triassic Mass Extinction

greatest ME in history >95% marine 70% terrestrial