ERTH 14-Chordates

what type of skeleton do chordates have

axial skeleton with a rod-like structure called notochord

what is the mode of life of chordates

• variable

• Benthic (infaunal i.e living within the benthic sediment, free or attached), nektic (actively swimming) or planktic (free drifting)

Stratograpgical range of chordates

Cambrian-Holocene

Phylums of Chordates

• Chordata

• Tunicata

• Conodonta

Oldest chordates in the fossil record (phylum)

Phylum chordata

mode of life of phylum chordata

exclusively marine

what did phylum chordata evolve from?

chatognath worms (arrow worms)

strat range of phylum chordata

cambrian-holocene. The oldest chordates have a complex morphology suggesting they might be older

What is the earliest/oldest chordate

phylum chordata, Yunnanozoon

what phylum and name? Three characteristics

Phylum chordata, Yunnanozoon.

The oldest chordate

Elongated body, laterally compressed but not well-defined head

Where was Yunnaozoon found?

The laggerstatten—Chegjiang fauna

Features of modern Chordates

Don’t have head/ not well developed

mouth surrounded by tentacles

What is this? Phylum and name

Phylum chordata, Pikaia

Where was Pikaia found

Bugress Shale, Canada

Features of Pikaia

• elongated body

• Small size, few cm in length

Does Chordates have a sparse fossil record?

Yes.

Tunicates are also known as:

Ascidians

Are tunicates solitary of colonial?

Solitary and rarely colonail

Mode of life of Tunicata? Marine/freshwater/brakish? attached or free living? What about the modern ones

Exclusively marine, mostly benthic and attached to the sea floor, rarely planktics. Only Mordern tunicata evolved planktic way of life

Origin of Tunicata

Not precise. Cambrian- Holocene, Edicaran?

What is the earliest tunicate?

Cheungkongella

what is this?

Cheungkonkella- the earliest tunicate

where does chenugkongella come from?

Chenugjiang fauna

Certain ascidian taxa have ——— within various parts of their body

spicules

what are spicules?

microscopical sized, composed of calcite, aragnoite and fluroite

range of tunicata?

Miocene-Holocene

What is this?

spicules of tunicate—large number of crystals that radiate from central body

What is a single conodont? Difference between Conodont animal?

• One piece of a chewing apparatus: Microscopical pieces of a chewing apparatus (teeth-like) of a cephalopod organism. But the conodont entire animal was unknown for 100 years

• Animal conodont: has several such conodonts

When were the first conodonts reported?

1856

When was the nature of conodont clarified?

In 1983

Conodont element composition? Mineral

Dominated by francolite, one variety of calcium phosphate known as apatite

Conodont organic component

Organic matter which represents 1-2% of the conodont and sits between the francolite crystals

Are conodont elements found in whole anatomical connections"?

No, they are found in tiny micropaleontological samples

Two parts of a conodont element

• base (embedded in soft tissue)

• crown (actively used for chewing)

Identify base and crown

What are the three tyoes of conodont element morphology?

1. Coniform: cone-like, simplest

2. ramiform (more complex, with denticles, "tooth-like projection” and a base with well developed a basal cavity)

3. Pectiniform (most complex, with a basal cavity and a basal pit)

Identify tyoe of conodont element

coniform

Identify tyoe of conodont element

ramiform

Identify tyoe of conodont element

pectiniform

what is this?

Basal pit of pectiniform chordates

Why is basal pit relevant?

In confirom and ramiforms, the growth is directional but pectiniform growth is more spohistaicated; they grew in all directions. A basal pit is a center of growth

Natural Assemblages

Groups of conodont elements that occir in a narrow area of a bedding surface. The theory that gained prominence was that it belonged to one animal that got ingested and excreted as natural assemblages

What is this?

The reconstruction of a chewing apparatus that came from a natural assemblage

A chewing apparatus of a conodont has the shape:

Bilaterally symmetrical

what is this?

 Clydagnathus, the first conodont animal. Chordate with a head

When and where was Clydagnathus found?

Lower carboniferous, Scotland

Features of Clydagnathus

Elongated body

Small size~ 6 cm

IMP: Well developed head with 2 large eyes in anterior portion

Conodonts are also considered as

Cephalochordates: Chordates with a head. Conodonts within the mouth

Conodonts evolved from:

Chatognath worms

When did Conodonts evolve?

Upper cambrian

Were Conodonts affected by permian/traiassic boundary?

Strongly affectedted but recovered quickly but became extinct at Trassic/jurassic boundary