Deuterostomes: Echinodermata (Chapter 15)

Question 1

deuterostome

Answer 1

posterior mouth
embryonic blastopore develops into anus
invertebrates - limited to hemichordates & echinoderms

Question 2

Phylum Echinodermata

Answer 2

pentagonal symmetry (sometimes obscured by bilateral)
mesodermal skeleton - porous plates w/ typical single crystal calcite
marine environment - good environment indicator
limited biostratigraphic use
starfish, sea urchins, sand dollars, sea lilies, feather starts, blastoids, sea cucumber, brittle stars
no a reef building group but skeletal remains so abundant that they themselves form limestone beds

Question 3

Subphylum Pelmataozoa

Answer 3

stalked echinoderms
predominantly sessile
basic body plan: holdfast (root-like), stem (trunk-like), cup = theca & calyx, & brachials (arms)
ossicles - diarticulated pieces of stalk, arms, holdfast & cirri (branch-like attachment to stem); create form taxa; morphotype useful for biostratigraphic correlation

Question 4

calyx

Answer 4

cup-like

contain nervous, respiratory, & digestive structures

Question 5

brachial

Answer 5

arm-like

extending from calyx

Question 6

stem

Answer 6

trunk-like

composed of columnals or ossicles

Question 7

holdfast

Answer 7

root-like

fixes organism to seabed

Question 8

Blastoidea

Answer 8

flask-like shape theca w/ 3 basal plates
theca typically articulate - some biostratigraphic correlations
ambulacra - elongated lancellet plates 
Paleozoic index fossil
Ordovician to Permian

Question 9

Crinoidea

Answer 9

cup = calyx w/ 2 (sometimes 3) rings of calcitic plates (basal, infrabasal, & radical plates)
varying #’s of arms attached to calyx = brachials w/ smaller finger-like structure - pinnules
stem & holdfast - below calyx
* feather stars - a calyx with brachials & pinnules - totally or partially lost holdfast & stem during all or part of life cycle - evolve swimming lifestyle - typically found below photic zone

Question 10

Crinoidea (taphonomy, fossil record, & ecology)

Answer 10

soft tissue holds calcitic plates & ossicles together
rapid decay - extremely abundant disarticulates; articulated calyx & stem - typically = rapid burial in aneroxic substrate
abundant with other rock forming Pelmatozoans
Paleozoic marine faunas w/ diverse type forms of ossicles; less common in Meso & Ceno
marine - sessile (sea lilies) + swimmers (feather stars)
Paleozoic - more common in shallow marine deposits
today - most stemmed types restricted to deep marine

Question 11

Subphylum Eleuthorozoa

Answer 11

non-stalked echinoderms
small soft tissue tubed feet - help with mobility, projected out from calcitic mesoderm
starfish, sea urchins, sand dollars
Cambrian to Recent

Question 12

ambulacral (Eleuthorozoa)

Answer 12

5 zones of narrower plates in echinoid skeleton

Question 13

interambulacral (Eleuthorozoa)

Answer 13

5 zones of broader plates in echinoid skeleton

Question 14

madreporite (Eleuthorozoa)

Answer 14

plate connecting water vascular system to external environment

Question 15

periproct/anus (Eleuthorozoa)

Answer 15

anus opening & associated plates

Question 16

peristome/mouth (Eleuthorozoa)

Answer 16

mouth - food is consumed

some w/ sophisticated jaw

Question 17

tubercle (Eleuthorozoa)

Answer 17

small projections from skeleton, may have spine attached

Question 18

spines (Eleuthorozoa)

Answer 18

elongated projections from skeleton

may have some Edicarian forms

Question 19

Class Asteroidea

Answer 19

starfish
simply pentagonal body
Ordovician - Recent
typically rare as fossils - normally in lagenstratten
marine, mobile predatory lifestyle
affected Mesozoic & Cenozoic shelly faunas

Question 20

Class Ophiuroidea

Answer 20

brittle star
simply pentagonal; ~starfish - more mobile arms
Ordovician - Recent
typically rare as fossils - clusters lagentratten
marine, mobile, predatory lifestyle
affect Meso & Ceno shelly faunas
may be nocturnal

Question 21

Class Echinoidea: Sea Urchins (Regular)

Answer 21

circular, pentagonal symmetry
disarticulate fairly easily
Ordovician?, Silurian - Recent
more common as fossils from Meso & Ceno than Paleo
fossil forms taxa - spines & plates - disarticulate
predator, benthic infauna & epifauna
ex: aristotle’s lantern

Question 22

Class Echinoidea: Sand dollars & Heart Urchins (Irregular)

Answer 22

Heart Urchin 
  more elevated, concave body 
  indentation along bilateral axis - resemblance to heart
Sand dollars
  relatively flat 
Middle Triassic - recent (Meso - Ceno)