Lab; Deuterostomes & Primate Evolution

Learning objectives:
● Identify the primary characteristics that define deuterostome animal phyla.
● Learn the names and functions of major structures for various animal phyla.
● Relate structure to function as a means of tracing evolution in a species.
● Learn the names, locations, and functions of the major parts of the mammalian skull.
● Evaluate and compare the morphology of various skulls to determine the likely function and
lifestyle characteristics of a range of mammals.
● Assess differences between hominin skulls and use them to construct a phylogenetic tree
depicting evolution of major traits from primates to modern humans.
Exercise 1: Deuterostome Animal Phyla
Question 1) Fill out the following table so that you can identify examples of these groups on the lab
and lecture exams (you may use a separate sheet, if needed).
Symmetry Tissues Body
Cephalization Other characteristics
Exercise 2: Sea star external anatomy
Question 2) On a separate sheet of paper, draw the top and bottom of a sea star and label the dermal
spines, dermal gills, mouth, anus, and tube feet.
Video of sea star dissection (8:16 minutes):
Question 3) In what phylum is the sea star (starfish) classified? _
Question 4) What four other types of animals are in the same phylum, and how are they different from
sea stars? Be able to visually identify specimens.
a) _________________________________________________________________
b) _________________________________________________________________
c) _________________________________________________________________
d) _________________________________________________________________
Exercise 3: Lamprey external anatomy
Question 5) Draw a lamprey and label the buccal funnel, anterior dorsal fin, caudal fin, nostril, pineal
body, eye, and anus.
Question 6) How many pairs of external pharyngeal gill slits does a lamprey have? _ Question 7) What is the function of the pineal body? Question 8) What is the difference in function between the spinal cord and notochord? Exercise 4: Rise of the Mammals Sixty-six million years ago, an asteroid wiped out the dinosaurs in a fiery global catastrophe. But we know little about how their successors, the mammals, recovered and took over the world. Now, hidden inside ordinary-looking rocks, an astonishing trove of fossils reveals a dramatic new picture of how ratsized creatures ballooned in size and began to evolve into the vast array of species—from cheetahs to bats to whales to humans—that rule our planet today. View the 53-minute video from PBS NOVA titled, “Rise of the Mammals: Amazing fossils reveal how mammals took over after an asteroid wiped out the dinosaurs” and answer the following questions. Question 9) According to the video, about how many species of mammals exist today? __
Question 10) How did the lifestyle (trophic or feeding group) change in the mammals after the meteor
strike? ________________________________________________________________
Exercise 5: Comparative Anatomy – Evaluating skull morphology & lifestyle
The form of an animal provides information about the functions or abilities of the animal. The variation
of wing shapes in birds, are a case in point. Open-country birds, such as shorebirds, swallows, and terns
have long, pointed wings. Species that have to navigate in dense vegetation have short, rounded wings.
A falcon’s wings are pointed, which are suitable for high-speed aerial chases, while the Sharp-shinned
Hawk has short, rounded wings for chases in woodlands. Many features of an animal’s skeleton
provide insights into the lifestyle of the organism. You can therefore use the skeleton to build
hypotheses about the lifestyle of an animal. Each animal is a product of evolution and ecology, and its
form is derived from the balance of all its energetic needs and demands.
Identify the patterns of skull morphology (shape) associated with particular lifestyles, and through
comparisons of different species, learn about their evolutionary history.
Examine the skulls available according to the following features. For each skull, use at least three
features to determine the lifestyle of the organism, and be able to defend your decision based on the
structure and function of the skull. Record your observations for each skull in Table 1, which you will
upload in the lab 4 quiz.
Observe the skulls for cat, black bear, cottontail rabbit, hedgehog, horse, and koala in the Online
Veterinary Anatomy Museum ( Species from this website are
listed individually below.
Skull images:
Cat skull presentation with labeled parts ((
Black bear skull photo (
Cottontail rabbit photo (
Hedgehog skull photo (
Horse skull photo (
Koala skull photo (
Parts of the Skull – A skull consists of 4 regions, the
rostrum, zygomatic arch, braincase, and the mandible.
Among mammals, there are certain features of the skull that
are most clearly related to the animal’s lifestyle.

  1. Dentition -note teeth types and arrangement.
  2. Jaws – the upper jaw and the mandible, which
    articulates with the cranium at the temporalmandibular joint.
  3. Zygomatic arches – the cheekbones, which are
    present in all synapsid animals.
  4. Sagittal crest – ridge on top of the skull.
  5. Orbits – note size and location.
  6. Nasal cavities – spaces inside the nose.
    Begin by observing the labeled model of a skull to
    familiarize yourself with the names and locations of the major parts of a skull. Then, fill out the
    following charts for each of the species in the laboratory by measuring or observing the parts of the
    skull described below.
    a. Dentition: Most mammals are heterodont,
    meaning there are different types of teeth present. From
    anterior to posterior, mammalian tooth types are:
     Incisors – typically have sharp edges and are used for cutting, nipping, gnawing
     Canines – typically single-pointed cones used for piercing, gripping, tearing and/or display
     Premolars – typically have 2 conical points and are used for gripping and tearing
     Molars – tend to be block-like and flattened for grinding OR sharp-edged and serrated for
    In some mammals, it is not possible to distinguish between premolars and molars, so they may be
    collectively referred to as “cheek teeth”.
    Dentition Lifestyle rules of thumb:
    ● Carnivores tend to have large canines, reduced incisors, and cheek teeth capable of shearing
    and slicing.
    ● Herbivores often have strong incisors, reduced or absent canines, and cheek teeth with large
    surfaces for grinding. Many herbivores have a gap (diastema), between the incisors and the
    cheek teeth.
    ● Omnivores have well-developed teeth of all four types.
    The dental formula was developed by mammalogists to summarize the dentition and dental patterns. It
    consists of a numerator, indicating the number of a particular kind of tooth on one side of the adult
    upper jaw, and a denominator indicating the number of each of the teeth on the adult lower jaw.
    The coyote has 3 incisors, 1 canine, 4 premolars and 2 molars on each side of its upper jaw and 3
    incisors, 1 canine, 4 premolars and 3 molars on each side of its lower jaw. Its dental formula is:
    I 3/3 C 1/1 P 4/4 M 2/3 A coyote has a total of 42 teeth.
    The dental formula of a cow, which is lacking several tooth types, is:
    I 0/3 C 0/0 P 3/3 M 3/3 A cow has a total of 30 teeth.
    Observe the dental charts from various veterinary sources that provide records for documenting the
    presence and condition of teeth during dental examinations. Teeth are assigned a standard number by
    location and type, which is the same regardless of the species (even if they are missing).
    Question 11) Based on the dental chart, what is the standard number assigned to a canine tooth in the
    left side of the mandible of a cat or dog? __
    b. Jaws: In most cases, mammals have upper and lower jaws that mirror each other. A long
    upper jaw usually is paired with a long lower jaw, and a short wide upper jaw is usually paired with
    a short wide lower jaw. The
    mandible is able to move up
    and down, and in some cases
    side-to-side and/or forward and
    backward to some extent. The
    mandible is attached to the
    cranium by the temporalis and
    masseter muscles. The paired
    temporalis muscles originate on
    the parietal bones of the cranium and insert on the coronoid process of the mandible. They exert
    bite force on the anterior portion of the jaws. The paired masseters originate on the inner surface of
    the zygomatic arches and insert on the lower, rear portion of the mandible. The force of the
    masseter muscles is concentrated on the posterior parts of the jaw.
    Jaw Shape Lifestyle rules of thumb:
    ● Many carnivores have relatively short jaws, with ventral margins that tend to be curved.
    The mandibles have shallow rami and large coronoid processes.
    ● Most herbivores have very long jaws. The ventral margins tend to be straight. The
    mandibles have deep rami and reduced coronoid processes.
    ● Omnivores present a mix of herbivore and carnivore features.
    a. Sagittal crest: The back part of the top of the cranium is formed by paired parietal bones that
    fuse along the midline of the cranium. The midline junction is called the sagittal crest, which can be
    either a distinct elevated ridge, a low linear bump, or completely smooth. The height of this feature
    is related to the size of the temporalis muscle, which originates and gains leverage by its attachment
    to the sagittal crest. A larger crest has more surface area for muscle attachment and can support a
    larger muscle. The crest may be either on top of the head or at the back of the skull or full length.
    Sagittal Crest Lifestyle rules of thumb:
    ● Carnivores tend to have prominent sagittal crests.
    ● Herbivores, with the exception of some rodents, tend to have low or absent sagittal crests.
    ● Omnivores range between carnivores and herbivores with respect to sagittal crest shape.
    b. Orbits: Eye sockets facing outward from the sides of the head indicate that the fields of
    vision do not overlap (i.e., monocular vision). Depth perception is not strong in these animals, most
    likely, but peripheral vision is excellent. Eye sockets that face forward allow for overlapping fields
    of vision (i.e., binocular vision), where depth perception is heightened but peripheral vision is
    Orbits Lifestyle rules of thumb:
    ● Carnivores typically have orbits directed forward.
    ● Herbivore orbits generally face outward (to the sides), but vary from species to species.
    ● Omnivores tend to have forward facing orbits.
    Elbroch, M. 2006. Animal Skulls: A Guide to North American Species. Stackpole Books,
    Mechanicsburg, Pennsylvania. pp. 1-61.
    Cotten, C. 2007. Mammalian Skulls. Indiana University, Bloomington, Indiana.
    Question 12) Fill in the following chart to predict the lifestyle of various mammals based on skull
    morphology. If you use abbreviations in the table to fit your answers in the space provided, present a
    key below (for example, a sagittal crest may be described as H = high; LB = low bump; A = absent):
    Table 1. Chart predicting the lifestyle of various mammals based on skull morphology.
    Key to your abbreviations:
  7. Dentition –
  8. Jaw shape –
  9. Sagittal crest –
  10. Orbit size & position –
  11. LIfestyle –
    Mammal Dental Formula Jaw Shape Sagittal Crest Orbit Size &
    Black bear
    Exercise 5: Hominin Cranium Comparisons
    Lab courtesy of Martin Nickels, ENSI at Indiana University
    For online coursework, observe the photos of 4 views each of 7 hominin skulls, identified with letters
    b to h (there is no skull lettered with an “a”) on the Smithsonian website provided below.
    Click the pictures to enlarge them to the same size on your computer screen and take some
    measurements to fill out the charts so that you can compare relative sizes of features.
    Then, use the data to draw a cladogram to complete this lab.
    Photos of 4 views each of 7 hominin skulls, identified with letters b to h, on Indiana University
    Flammer, L., J. Beard, C.E. Nelson, & M. Nickels. 1998. ENSIWEB. Evolution/Nature of Science
    Institutes. Hominin skull images. Retrieved 17 September 2020 from
    The Smithsonian also has a Mystery Skull Interactive game to compare 4 unknowns to known species:
    Work in teams of up to 4 students to complete all measurements and observations. All measurement
    units should be reported in millimeters (mm).
    If you are using online photos, you may estimate relative sizes of features from the braincase widths for
    the actual skulls, which are listed below:
    b = female [95 mm]
    c = male [147 mm]
    d = unknown [135 mm]
    e = male [152 mm]
    f = female [140 mm]
    g = unknown [105 mm]
    h = unknown [95 mm]
    Question 13) Upload a copy of your charts for the hominin skulls with all data in Table 1 Parts A, B
    and C.
    Examine the following features of the skull for comparisons between the species of hominins, and take
    notes into the charts.
    If you use abbreviations for your observations, note those in a key at the top of each chart.
    Part A: Braincase
  12. With the skull eyes facing forward in normal anatomical position (NAP), does the forehead
    appear vertical or flat?
  13. Is a supraorbital browridge present?
  14. If present, does the browridge run continuously or is it divided?
  15. When viewed from above, front to back, what is the shape of the braincase?
  16. Is a sagittal crest present?
  17. In NAP, is the foramen magnum oriented down or angled toward the rear?
  18. Is the mastoid process relatively flat or does it noticeably protrude from the skull?
    Part B: Face
  19. Are the nasal bones raised (arched) or flat?
  20. Measure the maximum breadth of the nasal opening (in mm).
  21. Measure the maximum height of the nasal opening.
  22. Measure the protrusion of the maxilla (the upper jaw) by measuring down the middle of the
    palate from the front edge of the foramen magnum to just in front of the two central incisors.
  23. Measure the bizygomatic breadth. This is the width of the face from the widest part of one
    zygomatic arch to the widest part of the other zygomatic arch.
    Part C: Dentition
  24. Are the rows of teeth (shape of dental arcade) U-shaped or do they diverge with the left and
    right molar distances wider than the left and right premolars?
  25. When viewed from the side, are the incisors angled out or are they vertical?
  26. Measure the combined width of the 4 incisors as one measurement.
  27. Does the canine tooth project above the chewing surfaces of the other teeth?
  28. Is a canine diastema (gap that allows opposing canine to seat) present?
  29. Measure the combined length of the left two premolars and three molars together by measuring
    from the back of the last molar to the front of the first premolar. This will determine the length
    of the chewing surface of the “cheek teeth”. Note: Measure the right side if the left side is
    missing for any of these 5 teeth.
    Table 1. Part A. Braincase Features
    Key to your abbreviations:
    1) Is
    flat or
    Brow Ridge
    continuous or
    4) Shape
    or at an
    7) Mastoid
    flat or
    Table 1. Part B. Facial Features
    Key to your abbreviations:
    8) Nasal
    bone arched
    or flat?
    breath of
    10) Maximum
    height of nasal
    11) Protrusion
    of maxilla
    12) Bizygomatic
    arch breadth
    Table 1. Part C. Dentition Features
    Key to your abbreviations:
    Rows of
    14) Incisors
    angled out
    or ventral
    width of
    16) Does
    17) Canine
    present (Y/N)
    length of
    premolars &
    Question 14) Once your measurements are completed for all specimens, please complete the following
    analyses in Table 2, so that you can prepare a phylogenetic tree that depicts the evolution of primates to
    modern humans.
    Table 2. Order the skull letters from longest to shortest maxilla protrusion, and graph these
    measurements on the y-axis by specimen number on the x-axis. Label your axes.
    Question 15) Think about the facial differences between chimpanzees (a close primate relative) and
    modern humans. Use the patterns you observe in your maxilla protrusion chart (above) to arrange the
    specimen letters in chronological order from oldest to most recent, based only on this character:
    oldest , , , , , , , , , most
    Now, create a phylogenetic tree considering all of the discrete traits that you evaluated. To make this
    easier, review your charts from Parts A, B, C and list only the characters that have discrete variables
    (presence/absence or only have a couple of options, like sagittal crest). Do not use more of the
    continuous variables (such as linear measurements like maxilla protrusion).
    Question 16) Identify characteristics you think are ancestral for each trait you could use to construct
    your tree and list the skull letters that have this condition.
    Discrete Trait Ancestral condition Skull numbers showing this
    ancestral condition
    Question 17) Using the characteristics from your options above, again list the skull letters in
    chronological order from oldest to most recent.
    oldest , , , , , , , , , most
    Question 18) Sketch your phylogenetic tree showing relationships between all of the skulls. You may
    need several drafts on scratch paper first. Don’t forget to put a hash mark indicating the derived trait
    shared between a particular cluster, or nested set of specimens.
    Question 19) Compare your phylogenetic tree with another group’s or individual’s depiction, if
    a) What is the same between your groups?
    b) What is different?

Sample Solution