1. Lab #11 Mesozoic and Cenozoic life, and hominids
Geology 1023
Lab #11
Mesozoic and Cenozoic life, and hominids

2. 3 major invertebrate phyla
Echinodermata (spiny skinned)
Class Echinoidea
Class Stelleroidea
Class Crinoidea
Mollusca
Class Gastropoda
Class Bivalvia
Class Cephalopoda
(Bryozoa)

3. Phylum Echinodermata Class Echinoidea (urchins and sand dollars)
Internal but peripheral skeleton (most of the soft tissue is internal to the skeleton)
Mobile, benthic
5-fold radial symmetry (actually bilateral in detail)
not abundant in fossil record, and best preserved in Mesozoic and Cenozoic

7. Echinoid morphology

8. Phylum Echinodermata Class Stelleroidea Star-shaped forms
Mobile, benthic
Apparent 5-fold symmetry (actually bilateral)
Rarely preserved as fossils

9. Phylum Echinodermata Class Crinoidea Sessile
Holdfast, stem, calyx, arms
Radial symmetry
All components made of calcite plates
stems plates (columnals) are circular or pentagonal
calyx plates are polygonal (hexagonal)
Some limestones composed almost entirely of crinoid material (crinoidal limestone)

10. Crinoid morphology

11. Modern crinoid: Antedon

12. Phylum Mollusca Three very important classes
Gastropoda (snails)
Bivalvia (“clams”)
Cephalopoda (octopus, squid & Nautilus)
Very important fossils of the Mesozoic and Cenozoic

13. Class Gastropoda
Very abundant (80,000 known living species, perhaps up to 250,000 in total)
Terrestrial and aquatic
Shell (if present)
Single
Coiled in a helical spiral (i.e., no plane of symmetry)
Unchambered
Important in Mesozoic

14. Apical angle

15. Small apical angle
Large apical angle

16. Class Bivalvia Shells No internal hard parts (c.f., brachidium)
Two
If symmetry is present, plane of symmetry between the shells (c.f. brachiopods)
Some forms have no symmetry (e.g., oysters)
No internal hard parts (c.f., brachidium)
No pedicle opening
Ligament area (pit)
Simple muscle scars (1 or 2, only)
Palial line (± sinus)

17. Bivalve morphology

18. Class Cephalopoda Pelagic Tentacle bearing Shells Shelled cephalopods
Shells are coiling in flat spiral (i.e., plane of symmetry)
Divided by septa into chambers
Shelled cephalopods
Very common and very important in Mesozoic (zone fossils)
Most modern forms have no shell (octopus, squid); largest invertebrate animals alive today

19. Class Cephalopoda
Shelled forms divided into 2 orders on the basis of the shape of the suture
Nautiloidea (straight or gently curved sutures)
Ammonoidea (convoluted sutures)
Belemnoidea = A squid-like order with an internal skeletal element called a “guard”
Guard is cigar-shaped, honey-brown calcite rod

20. Nautiloid

21. A straight nautiloid

22. Ammonite

23. Ammonite morphology

25. Belemnite guards

26. Belemnites and ammonites

27. Phylum Bryozoa Colonial Marine (mostly), benthic, filter-feeders
Individuals (zoids) are microscopic and occupy minute structureless cavities (zoecia) on lacy frond-, sheet- or mound-shaped colonies (zoaria)

30. An ancient bryozoan

31. Hominins
Most of the prominent skeletal differences are visible in the skull
Many different parameters that can be measured
Position of the foramen (condylar position index – high in hominins)
Angle of the forehead (high in hominins)
Brow ridges (small)
Sagittal crest or keel (absent)
Enlarged canines and canine diastema (absent)

32. Condylar position index
C = occipital condyle (boney knob beside the foramen)
CD/CE x 100
CD = 6.3 cm
CE = 16.2 cm
CPI = /16.2x = 39

33. Forehead angle Forehead angle = J
Measured from plane of the orbits (eye sockets)
Relatively small (<20°) in modern humans

34. Other features as seen in a gorilla skull
Sagittal crest
Brow ridges
Canine diastema
Enlarged canine

35. Questions?

36. Reminder!
Final lab exam next week!