Reading:

• Textbook Chapter 16
• Textbook Chapter 17
• M. Wells, 1998. Sea Urchins. Ch. 1, Civilization and the Limpet, p. 1-8.

Echinoderms: Gain insight in structure and way of life of various echinoderms. Modern groups (both thought to have been implicated in the Mesozoic Marine Revolution) are represented by sea urchins and starfish, Paleozoic groups by Crinoids. Sea urchins have a good fossil record from the Mesozoic; starfirsh have a very poor record because they tend to fall apart in separate plates.

Vertebrates: Gain insight in the morphology of skull bones, skull fenestration and teeth structure in various groups of vertebrates (fish, amphibians, reptiles, mammals).

1. Sea urchins: there are 2 regular sea urchins (one plus spines) and 1 irregular species (sand dollar).

Regular sea urchins: Recognize the ambulacral fields and the interambulacral fields in two sea urchins with very different skeletal structure. Aristotle's lantern and madrepore plates usually fall out, but the madrepore plates are present in some specimens which in life had thin spines (p. 326; 337), living largely in rock crevices in the intertidal zone. Also note the separate Aristotle's lantern. The sea urchins with coarse spines (note p. 324, 335) tend to live somewhat further offshore, in shallow lagoons, while sand dollars live even further offshore, on more high-energy sand bars. Sand dollar: compare specimens with p. 327, 338; note lunules, position of mouth and anus, ambulacral fields.

2. Star fish: There are two different recent species, one smooth form (sandy-muddy shore lines) and one spiny form (living on coral reefs). Locate ambulacral fields, location of anus, madreporite plate; compare with situation in sea urchins.

3. Crinoids from the Crawfordsville (IN) Mississippian Limestone (about 340 Ma). See if you can distinguish the following: Are there plates in the calyx which are clearly visible and different from plates in the arms? Are the arms branched or not? Can you see pinnules on the arms? Are there any signs of the tegmen? Note that forms with a larger cup could eat larger meals (more space for stomach). Forms with very finely branched arms could catch only small prey (larger prey would damage the arms). Larger particles move on currents close to the ocean floor, smaller particles move higher. Which of these crinoids would have been very tall-stemmed?

#, Name	Order	Calyx? tegmen?	Arms branched, pinnules?	Tall stemmed or not?
2991: Cyathocrinites multibrachiatus	'primitive' Cladida	clear calyx, separated from arms, tegmen not visible	arms branched manifold, no pinnules visible	probably not (no fine pinnules)
2992: Platicrinites hemisphaericus	Camerata	calyx with many plates, tubercles, no brachial plates; no tegmen visible	arms branched multiple times, pinnules visible	yes
2295/2996: Agaricocrinus americanus/splendens	Camerata	calyx small; brachial plates; no tegmnen visible	branched once; many pinnules	yes
3000: Uperocrinus longirostris (=Bactocrinus)	Camerata	large calyx; brachial plates; no tegmen visible	arms branched once; pinnules; note large anal tube	probably not
3002: Onychocrinus ulrichi	Flexibilia	small calix; tegmen not visible	arms branched, no pinnules	probably not
3003:Scytalocrinus robustus (=Scaphiocrinus porrectus)	'advanced' Cladida	mid-sized calyx; brachial plates present; tegmen not visible	arms branched once; pinnules visible in some specimens	probably
3006: Barycrinus crassibranchiatus (=princeps)	'primitive' Cladida	calyx clearly visible, brachial plates; tegmen not visible	arms branched multiple times, no pinnules visible	probably not
3009: Gilbertsocrinus tuberosus	Camerata	large tuberculate calyx, large knobbed tegmen visible	few times; no pinnules	no

Note that one specimen of G. tuberosus and one of P. hemisphaericus have a cap-shaped snail (Platyceras infundibulum), which is often found on crinoids.

The additional rock : what other organisms than Crinoids were living here?

• Brachiopods (flattened, but they are Productids) and fan-shaped Bryozoans.

Vertebrates:

There are 9 skulls, which belong to the following:

• Osteichthyes: bowfin (Amia calva), gar (Lepisosteus osseus)
• Lissamphibia: frog (Rana sp.)
• Amniota, Anapsida: snapping turtle (Chelydra serpentina)
• Amniota, Diapsida: dwarf crocodile (Osteolaemus tetraspis), rattlesnake (Crotalus horridus)
• Amniota, Mammalia, Eutheria: Carnivora, siberian wolf (Canis lupus); Artiodactyla, pig (Sus scrofa).
• Amniota, Mammalia, Metatheria: marsupial wolf (Thylacynus cynocephalus)

Identify which one is which; even if you recognize the skull immediately, make sure that you have arguments in favor of this recognition.

1. What kind of teeth does the animal have (homeodont or a heterodont) ?
2. How many bones can you see in its lower jaw?
3. What type of food do you think it might eat?
4. What sort of paired appendages do you think it has?
5. What can you say about its integument (outer protective covering)?
6. For the Amniota: Can you identify cranial fenestra? If so, of what type are they?

1=frog; homeodont (small); several but very reduced; insects; 4 legs; moist skin; NA

2=rattlesnake; homeodont however tricky this is (i.e. same shape although very different sizes); several; carnivorous; no legs; skin, scales; diapsid but very difficult because skull bones are strongly reduced and almost all holes.

3=bowfin fish, homeodont; many; carnivorous; fins; scales; NA

4=pig; heterodont; omnivorous; 1 bone lower jaw; 4 feet, hooves; skin/hair; yes, synapsid

5=crocodile; homeodont; several but intergrown; carnivorous; 4 feet; skin with heavy scales; yes, diapsid but skull covered with 'dermal bones' (heavy scales).

6=marsupial wolf, heterodont; 1 bone; carnivorous; 4 feet; skin with hair; yes, synapsid. One can see this is a marsupial because of presence of 4 incisors per half-jaw, shape of raer part of lower jaw.

7=snapping turtle, no teeth; several bones but strongly intergrown; carnivorous; 4 feet; scaly skin plus shield; no, anapsid.

8= gar, homeodont; several; carnivorous; fins; skin with scales; NA.

9= placental wolf, heterodont, 1 bone; carnivorous, 4 feet, skin with hair; yes, synpasid.