Therapsids

Definition

Therapsids are a group of synapsid reptiles that lived during the late Paleozoic and throughout the Mesozoic eras, often referred to as 'mammal-like reptiles.' They are significant because they are the ancestors of modern mammals and showcase important evolutionary traits that distinguish mammals from other reptiles, such as differentiated teeth and evidence of warm-bloodedness.

5 Must Know Facts For Your Next Test

1. Therapsids first appeared in the late Carboniferous period and became prominent during the Permian period, showcasing a variety of forms and adaptations.
2. Some therapsids developed features such as larger limbs, specialized teeth, and potentially hair-like structures, indicating a transition toward mammalian characteristics.
3. The evolution of therapsids was crucial in the development of endothermy (warm-bloodedness), allowing them to adapt to various environments.
4. Most therapsid lineages went extinct during the Permian-Triassic extinction event; however, some survived and eventually led to the emergence of true mammals.
5. The study of therapsids provides valuable insights into the evolutionary history of mammals and how key adaptations arose over millions of years.

Review Questions

• How did therapsids contribute to the evolutionary transition from reptiles to mammals?
  • Therapsids represent a critical evolutionary step between reptiles and mammals due to their unique anatomical features. They exhibited traits such as differentiated teeth, which allowed for a varied diet and more efficient processing of food. Additionally, their adaptations toward warmer body temperatures suggest an early form of endothermy, paving the way for the further development of mammalian characteristics.
• Discuss the significance of the Permian Period in relation to therapsid evolution and diversity.
  • The Permian Period was crucial for therapsid evolution as it marked the height of their diversity and ecological dominance. During this time, therapsids adapted to various environments and evolved numerous forms that displayed increasingly mammalian traits. This period laid the groundwork for future mammalian evolution, but it also ended dramatically with the largest mass extinction in Earth's history, which wiped out many therapsid species.
• Evaluate the impact of environmental changes during the Mesozoic era on therapsid survival and the eventual rise of mammals.
  • Environmental changes during the Mesozoic era significantly impacted therapsid survival as they faced increased competition from emerging dinosaurs and changing climates. While most therapsid groups became extinct during this time, a few lineages survived and evolved into early mammals. This transition allowed mammals to exploit new ecological niches left vacant by dinosaur dominance, setting the stage for their eventual diversification and success after the extinction event that wiped out dinosaurs at the end of the Cretaceous period.

Related terms

Synapsids:

A clade of animals characterized by a single temporal fenestra in the skull, which is a key feature that distinguishes them from diapsids.

Mammalia: The class of animals that includes all mammals, characterized by features such as hair, mammary glands, and three middle ear bones.

Permian Period: The last period of the Paleozoic era, during which therapsids thrived and began to diversify before the mass extinction event at the end of the period.