Sarcopterygii

Definition

Sarcopterygii, commonly known as lobe-finned fishes, are a clade of bony fish characterized by their fleshy, lobed pectoral and pelvic fins, which are supported by bones. These features connect them closely to tetrapods, as they are believed to be the ancestors of land vertebrates. Sarcopterygii include both extant species like coelacanths and lungfishes, and the extinct ancestors that contributed significantly to vertebrate evolution.

5 Must Know Facts For Your Next Test

1. Sarcopterygii were some of the first fish to develop a structure in their fins that resembles limbs, which is a key adaptation for life on land.
2. The most well-known extant members of Sarcopterygii include the coelacanths and lungfishes, which exhibit unique respiratory adaptations.
3. Sarcopterygii are believed to have diverged from other bony fishes around 400 million years ago during the Devonian period.
4. Some lungfishes can breathe air using lungs, allowing them to survive in low-oxygen environments or during droughts.
5. Fossil evidence suggests that ancient sarcopterygians played a critical role in the transition from aquatic to terrestrial life.

Review Questions

• How do the anatomical features of Sarcopterygii differ from those of Actinopterygii, and what implications does this have for their evolutionary significance?
  • Sarcopterygii are distinguished from Actinopterygii primarily by their lobed fins, which contain bone structures akin to those found in tetrapod limbs. This anatomical difference not only highlights their evolutionary divergence but also suggests that sarcopterygians are more closely related to land vertebrates. The robust structure of lobed fins indicates adaptations that may have facilitated movement on land, making Sarcopterygii crucial for understanding the transition from water to terrestrial habitats.
• Discuss the role of Sarcopterygii in vertebrate evolution and how their adaptations may have contributed to the rise of tetrapods.
  • Sarcopterygii played a vital role in vertebrate evolution as they exhibit key adaptations such as lobed fins that provided a structural foundation for the development of limbs. Their ability to navigate shallow waters effectively positioned them for eventual terrestrial exploration. These adaptations not only allowed early sarcopterygians to exploit new ecological niches but also set the stage for the evolutionary transition to tetrapods, leading to the emergence of amphibians and subsequently all land-dwelling vertebrates.
• Evaluate the impact of environmental changes during the Devonian period on the evolution of Sarcopterygii and their eventual transition to tetrapods.
  • During the Devonian period, significant environmental changes such as fluctuating water levels and shifting climates influenced the evolution of Sarcopterygii. As aquatic habitats became more variable and fragmented, those with adaptations like lobed fins and lungs were better equipped to survive in shallow waters and even on land during dry periods. This adaptability not only ensured their survival amid changing environments but also facilitated their transition into early tetrapods, marking a pivotal moment in vertebrate history that led to colonization of terrestrial ecosystems.

Related terms

Actinopterygii:

A class of bony fishes known as ray-finned fishes, which have fins supported by thin, bony rays rather than lobes.

Lobed Fins: Fins that are fleshy and supported by bone structures, characteristic of sarcopterygian fishes and crucial for their movement in shallow waters.

Tetrapods:

Four-limbed vertebrates that evolved from sarcopterygian ancestors, leading to amphibians, reptiles, birds, and mammals.