Age of Dinos exam 2

Linnean Taxonomy

• Genus (pl. genera)

  • Represents a “generic” category, including one or more species

  • One word name, Capitalized, italicized

    • Ex. Homo, Tyrannosaurus, Ginkgo

• Species (pl. species)

  • Represents a more “specific” category

  • Two word names combining the genus name and a second, non-capitalized word

    • Ex. Homo sapiens, Tyrannosaurus rex, Ginkgo biloba

Note: In handwriting, can’t italicize. Underline instead!

Tyrannosaurus rex or T.rex

NOT: T-Rex, T-rex, t. rex, T Rex

Binomial Nomenclature

Rule used for naming the genus and species

Ex.

• Homo sapien

• Tyrannosaurus rex

Taxonomy and Systematics

• Biological Nomenclature (Taxonomy)

  • Rules for names of groups of organisms

• Taxon (plural = taxa)

  • A unit of biodiversity

• Systematics

  • The study of biodiversity and its organization

How to write a species name

• Homo sapiens — H. sapiens

• Ginkgo biloba — G. biloba

• Tyrannosaurus rex — T. rex

All species in the same genus have the same generic name

• Homo erectus

• Homo floresiensis

• Homo neanderthalensis

• Homo sapiens

• Panthera tigris

• Panthera leo

• Panthera onca

• Panthera pardus

How are names chosen, and are there rules to naming a specific species?

Names Can Be Chosen to…

• Describe the species: Triceratops horridus, the “roughened three-horned-face”

• Honor the geographical place or geological stratum in which it was discovered: Albertosaurus, after Alberta, Canada

  • Language: Seitaad, Navajo for “sand monster”

• Honor a colleague, mentor, sponsor, discoverer, landowner, spouse, etc. Diplodocus carnegii, for Andrew Carnegie, who sponsored the expedition that discovered it

Rules: Principle of Priority

What is the Principle of Priority?

Oldest valid name is the one used

• Examples:

  • Anatosaurus Lull & Wright 1942 vs. Edmontosaurus Lambe 1917

  • Brontosaurus excelsus 1879 vs. Apatosaurus excelsus 1877 (Lumping)

  • Tarbosaurus bataar Maleev 1955 vs. Tyrannosaurus rex Osborm 1905 (Splitting)

What are the Linnean ranks and the flaws that make us no longer use it today?

Linnean ranks: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

Do they mean anything?

• Number of Species?

• Morphological Disparity?

• Age of Origin?

• ???

Not really — Arbitrary, with no intrinsic meaning or equivalency across taxa

What is the species concept?

Traditionally based on shared common features of:

• Appearance (morphology)

• Behavior and Habits

• Reproduction

• Habitat

• etc.

Charles Darwin:

• “Species are only well-marked varieties”

• “The only distinction between species and well-marked varieties is, that the latter are known, or believed, to be connected at the present day by intermediate gradations, whereas species were formerly thus connected.”

Ernst Mayr:

• Modern Synthesis (early 20th Century)

• Biological Species Concept

  • Naturally occurring populations that interbreed and produce viable fertile offspring and are reproductively isolated

Are there different types of species concepts?

~31 different definitions!

What are the flaws for each species concept?

• Morphospecies: Different species can look similar, while individuals of the same species can look different because of age, sex, or variation

• Biological species: It cannot be used easily for fossils or asexual organisms because we cannot determine whether they can successfully reproduce

• Phylogenetic species: It can classify very closely related populations as separate species based on small evolutionary differences

Which species concept do paleontologists use?

Species are groups of morphologically distinct populations where:

• Within group variation is of the degree displayed by populations of living species

• Between group differences are the kind and degree expected to result from reproductive isolation

What did Carlos Linnaeus do?

The “Father of Systematics” (1707-1778)

• Established a hierarchical system of organizing life

• Established fixed ranks

  • Kingdom, Phylum, Class, Order, Family, Genus, Species

    • Principles for organizing taxa

    • In Linnaean Systematics, classification based on overall similarity

What is speciation?

Provides an explanation for the hierarchical arrangement of biodiversity

• The basis of speciation is geographic variation within species

After 1859, living things were organized based on two criteria:

1. Phylogeny

2. Similarity

Problems!

• Phylogeny (= evolutionary history) is objective

• Similarity is not

Will Hennig (1913 - 1976)

German entomologist

Phylogenetic systematics = Cladistics

• Developed in 1950s

• Phylogeny should be the only organizing principle in systematics

• Became prevailing view in 1970s

• Currently best method for understanding shared evolutionary history

Cladistics: Reconstructing the Tree of Life

• Presence of shared derived features (apomorphies)

• Fossil record of intermediate forms (and entirely extinct branches of Tree of Life)

• Pattern of shared DNA sequences

• Apomorphy = a derived character

  • 🌟Synapomorphy🌟 = a shared derived character

  • Autapomorphy = a unique derived character

• Plesiomorphy = an ancestral character

Derived characters tell us about change over time (= evolution)

Character

A morphological feature of an animal

Derived Characters

traits that evolved more recently and are different from the ancestral form

Cladogram

stick-figure hypothesis of the pattern of shared common ancestry

Sister Taxa

Closest relatives on a cladogram

• Closest relatives = taxa sharing a most recent common ancestor

Branch

Node

represents the most recent common ancestor of the descendant branches

🌟Monophyletic Group🌟

an ancestor and all of its descendants

• aka. “clade”

Paraphyletic Group

an ancestor and some (but not all) descendants

Polyphyletic Group

assemblage of similar but unrelated taxa

What are synapomorphies of Chordata?

What are synapomorphies of Gnathostomata?

Jaws

• Some developed bony projections from their jaws — tooth plates

• These fish are called Placoderms

Where do jaws come from?

The presence of jaws is a synapomorphy of the clade Gnathostomata

• The vertebrate jaw was a major evolutionary innovation

What are synapomorphies of Osteichthyes?

internal bony skeleton

What are synapomorphies of Sarcopterygii?

• Humerus in forelimb

• Femur in hindlimb

What adaptations are needed before moving onto land?

• Scales and mucous

  • Prevented desiccation

• Lungs

  • Able to breathe air

• Bony skeleton

  • Could support weight out of water

• Limbs with wrists/ankles and digits

  • Propulsion of body weight

How are swim bladders and lungs related?

Lungs

• Why would fish need lungs?

  • Low oxygen aquatic environment, get extra oxygen from air

  • Environment dries out seasonally, burrowing and torpor during dry season

What group was able to move completely on land?

Tetrapods

• When early tetrapods moved onto land, they had already inherited lungs and lots of other important features from their fully aquatic ancestors

  • Lungs were plesiomorphies

What is special about their eggs? What are their synapomorphies?

Amniota

• 1st appears in Carboniferous

• Synapomorphy: amniotic egg

  • Shelled egg with specialized membranes

  • Laid on dry land

  • Allowed complete colonization of land!

What is a fenestra?

an opening or hole in an animal’s skull, often found in the temporal region behind the eye socket

What purpose does a fenestra serve?

makes the skull lighter and provides space for jaw muscles to attach and expand

What is the purpose of an infratemporal fenestra?

provides space for jaw muscles to attach and move, helping the animal bite and chew

Groups in Sauria

• Testudines

• Lepidosauria

• Euryapsida

• Archosauriformes

Sauria:

• 1st in Carboniferous

• Synapomorphies

  • Post-temporal fenestra

  • Infratemporal fenestra

  • Supratemporal fenestra

Sauria is a polytomy

Polytomy = 3 or more branches emerging from one node

• Usually indicated uncertainty

What are the synapomorphies of Lepidosauria?

Overlapping scales

• Sphenodon (= tuatara; NOT a lizard!)

• Squamata (lizards, snakes, amphisbaenians)

  • Have moveable joint between quadrate and rest of skull

  • Lower temporal bar is absent in most lepidosaurs

Squamata have moveable joints in their skulls. What is this called?

Cranial kinesis: ability to move one part of the skull relative to another