Podcast
Questions and Answers
What is the class of the placoderms?
What is the class of the placoderms?
- Chondrichthyes
- Placodermi (correct)
- Ostracodermi
- Osteichthyes
What adaptive advantages did placoderms show over ostracoderms?
What adaptive advantages did placoderms show over ostracoderms?
Several adaptive advantages
What was the first fish feature acquired by the placoderms?
What was the first fish feature acquired by the placoderms?
Lower jaw
What advantage did the lower jaw provide for placoderms?
What advantage did the lower jaw provide for placoderms?
What did lampreys use their jawless mouths for?
What did lampreys use their jawless mouths for?
How did placoderms differ in feeding compared to ostracoderms?
How did placoderms differ in feeding compared to ostracoderms?
In what way were ostracoderms typically limited in their movement?
In what way were ostracoderms typically limited in their movement?
What were the fins of placoderms necessary for?
What were the fins of placoderms necessary for?
How did placoderms utilize their swimming environment differently?
How did placoderms utilize their swimming environment differently?
Better extensions off the body to either side greatly increased (blank), (blank), and (blank) were strongly selected.
Better extensions off the body to either side greatly increased (blank), (blank), and (blank) were strongly selected.
The earliest of these paired fins had (blank) and appear to be simply (blank), but as time went by, a (blank) allowed for greater control during swimming.
The earliest of these paired fins had (blank) and appear to be simply (blank), but as time went by, a (blank) allowed for greater control during swimming.
What embryological structure is suggested to have evolved into the lower jaw?
What embryological structure is suggested to have evolved into the lower jaw?
From what do the lower jaw and gill arches derive embryologically?
From what do the lower jaw and gill arches derive embryologically?
Anatomically, the same cranial nerve that innervates the muscles of the gill arch innervates the (blank) and in sharks, the muscles that work the gill arches also work the (blank).
Anatomically, the same cranial nerve that innervates the muscles of the gill arch innervates the (blank) and in sharks, the muscles that work the gill arches also work the (blank).
What does the term 'placoderms' translate to?
What does the term 'placoderms' translate to?
What is the classification for sharks?
What is the classification for sharks?
What do you call bony fish, the largest group that diversified from early jawed fishes?
What do you call bony fish, the largest group that diversified from early jawed fishes?
Placoderms are now extinct.
Placoderms are now extinct.
What covers the head and neck of placoderms?
What covers the head and neck of placoderms?
What is a characteristic of the large bony plates of placoderms?
What is a characteristic of the large bony plates of placoderms?
Which group diversified widely among early jawed fishes?
Which group diversified widely among early jawed fishes?
What improvements did the placoderms showcase in anatomy?
What improvements did the placoderms showcase in anatomy?
What paired fins did placoderms develop?
What paired fins did placoderms develop?
How long could Dunkleosteus terrelli grow?
How long could Dunkleosteus terrelli grow?
What did most placoderms also have in addition to gills?
What did most placoderms also have in addition to gills?
Placoderms survived for about sixty million years before going extinct at the end of the Devonian period during a time of anoxia called the (blank).
Placoderms survived for about sixty million years before going extinct at the end of the Devonian period during a time of anoxia called the (blank).
Study Notes
The Placoderms Overview
- Placoderms, belonging to the class Placodermi, were among the earliest jawed fishes.
- They showcased adaptive advantages compared to ostracoderms, demonstrating evolutionary progress.
Evolution of the Lower Jaw
- The development of a lower jaw marked a significant evolution in vertebrates, facilitating diverse feeding strategies.
- Unlike lampreys, which used their jawless mouths aggressively, most ostracoderms were limited to suction feeding from the bottom.
Mobility and Feeding Habits
- Placoderms were predatory, capable of swimming towards and consuming ostracoderms and other animals.
- They utilized the entire water column for movement, contrasting with ostracoderms that primarily stayed on the pond bottom.
Anatomical Features
- Improved body extensions enhanced stability during swimming, with paired pectoral and pelvic fins becoming essential.
- Early paired fins had broad bases as body wall extensions, while later adaptations featured narrower bases for enhanced swimming control.
Evolutionary Insights
- The lower jaw likely evolved from gill arches found in ostracoderms, supported by both embryological and anatomical evidence.
- Lower jaws and gill arches share a common embryological origin from neural crest cells.
Cranial Nerves and Muscle Innervation
- The cranial nerve that innervates gill arch muscles also innervates the lower jaw muscles, indicating a muscle coordination link between these structures.
Distinct Characteristics
- The term "placoderms" translates to "shell skins," referring to their bony external features.
- They had large, heavy bony plates covering their head and neck, which may have increased drag while swimming.
Diversity and Extinction
- Placoderms experienced significant diversification during their existence, particularly noted for lower jaw enhancements and advanced shredding plates for prey.
- They developed paired pelvic fins and survived for around sixty million years before becoming extinct at the end of the Devonian period during the Hangenberg Event.
Notable Species
- Dunkleosteus terrelli was a prominent species among placoderms, reaching lengths of up to six meters.
- Most placoderms possessed both lungs and gills, allowing for versatile gas exchange during their aquatic life.
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Description
Test your knowledge about the early jawed fishes known as placoderms. This quiz covers their classification, evolutionary advantages, and significant features like the lower jaw. Perfect for students of paleontology or those interested in evolutionary biology.
