Lab 2 - Osteology of sharks, bony fish, and reptiles

G404 Geobiology Name __________________________________
Fall 2013

Lab 2
Osteology of sharks, bony fish, and reptiles

Use the materials in this lab to familiarize yourself with the skull and skeleton of living
sharks, bony fish, and reptiles. The skulls are complicated and varied, so consider the
following tasks as a way to make sense of the material:

1. Identify elements belonging to the chondrocranium (base of the braincase and
sense organs), splanchnocranium (gill arches and components of the mandibular
and hyoid arches), and dermatocranium (the outer bones, most of which lie not far
below the skin).

2. Find the parietal and tabular on all of the skulls (note: not all groups possess both of
these bones).

3. Which bones encircle the orbit on each skull?
4. Which bones support teeth?
5. Which bones are involved in the joint between upper and lower jaws?
6. Which taxon has the fewest skull bones? What are some of the extra bones on those

with more?
7. What structures are present in the shark skull?

Assignment

Using the specimens available in lab, begin compiling information about the presence and
absence of skeletal characteristics. We will use this information in later labs to perform your
own phylogenetic analysis of selected living vertebrates. The kind of information useful at
this broad level is the gain and loss of bones or major transformations in homologous bones.

Typical examples of phylogenetic characters are “tabular bone (1) present or (2) absent” or
“jaw joint (1) between quadrate and articular bones or (2) between dentary and squamosal
bones” or “occipital condyle (1) single or (2) double”. For each taxon in your analysis you will
eventually need to record the condition of these characters by assigning each variant (state)
a number and recording the appropriate number for each taxon. To be useful, the character
must vary among taxa being considered. Ideally each variant will be shared by at least two
taxa.

For this lab, identify at least ten characters that vary among four taxa: shark, bony fish, and
amphibian, and reptile.

1. Describe each character and its variants using similar format as above.
2. Record the species name, class name, and specimen number for your four taxa.
3. For each species, record the character state (variant) for each of your ten

characters.

Shark (Chondrichthyes)

(from Romer and Parsons, 1977, The Vertebrate Body)

(from Walker and Homberger, 1992, Vertebrate Dissection)

2

(from Walker and Homberger, 1992, Vertebrate Dissection)

Bony Fish (Osteicthyes)

(from Romer and Parsons, 1977, The Vertebrate Body)

3

(from Walker and Homberger, 1992, Vertebrate Dissection)

4

Salamander (Amphibia)

(from Trueb, 1993, Patterns of Cranial Diversity among the Lissamphibia)

5

Turtle Skull

(from Romer and Parsons, 1977, The Vertebrate Body)

Lizard Skull

(from Romer and Parsons, 1977, The Vertebrate Body)

Alligator Skull

(from Romer and Parsons, 1977, The Vertebrate Body)

6