What is the Difference Between Cetacea and Sirenia

The key difference between ceracea and sirenia is that cetacea is an infraorder that consists of large carnivorous aquatic mammals, while sirenia is an order that consists of small herbivorous aquatic mammals.

Aquatic and semi-aquatic mammals are a diverse group of animals. They dwell partly or entirely in water. These animals include various marine mammals that live in the ocean as well as freshwater species such European otters. Their dependence on the aquatic environment varies greatly. For example, river dolphins and manatees are fully aquatic, while seals are semi-aquatic. Their diet varies considerably as well, from aquatic plants and leaves to small fish, crustaceans, etc. Therefore, Cetacea and Sirenia are two taxonomic groups of aquatic mammals.

CONTENTS

1. Overview and Key Difference
2. What is Cetacea  
3. What is Sirenia
4. Similarities – Cetacea and Sirenia
4. Cetacea vs Sirenia in Tabular Form
5. Summary – Cetacea vs Sirenia

What is Cetacea?

Cetacea is an infraorder that consists of large carnivorous aquatic mammals. The mammals in this infraorder are called Cetaceans. The key characteristics of these aquatic mammals are their fully aquatic lifestyle, streamlined body shape, carnivorous nature, and large size. These aquatic mammals propel through the water by using the powerful up and down movement of their tail. The tail typically ends in a paddle-like fluke. Moreover, they manoeuvre the movement of the water by using their flipper shaped forelimbs. Cetaceans predominantly inhabit marine water; a small number of cetaceans also reside in brackish water or freshwater.

Cetaceans have a cosmopolitan distribution. These aquatic mammals are also very famous for their intelligence and complex social behaviour. Their enormous size can reach a length of 29.9 meters and a weight of 173 tonnes. The blue whale is a good example of the enormous size of cetaceans. There are around 86 living species in this infraorder. Furthermore, cetaceans have been extensively hunted over the years because of their meat, blubber and oils. Therefore, the International Whaling Commission has agreed on putting a halt to commercial whaling.

What is Sirenia?

Sirenia is an order that consists of small herbivorous aquatic mammals. These herbivores aquatic mammals usually live in swamps, rivers, estuaries, wetlands, and coastal marine waters. Serenia order consists of two distinct families: dugongidae (dugong) and trichechidae (manatees). This order also has a total of four species. Sirenians grow between 2.5 to 8 meters in length and 1500 kg in weight. They have large a fusiform body in order to reduce the drag through the water. They also have heavy bones that act as ballast.

Sirenians are slow-moving mammals and are sensitive to temperature fluctuations. These aquatic mammals use their strong lips to pull out seagrasses. Though they are considered to be herbivorous, some members may eat birds and jellyfish. The meats, oils, bones, and skins of Sirenians are valuable items in the international market. Due to overhunting, the largest Sirenian in this order, Steller’s sea cow, became extinct in 1768.

What are the Similarities Between Cetacea and Sirenia?

• Cetacea and Sirenia are two taxonomic groups of aquatic mammals.
• They can live in freshwater as well as marine water.
• Mammals of both orders have been extensively hunted for meat, oils, bones, etc.
• These mammals are warm-blooded, have lungs, and have a more complex brain.

What is the Difference Between Cetacea and Sirenia?

Cetacea is an infraorder comprising of large carnivorous aquatic mammals, while sirenia is an order comprising of small herbivorous aquatic mammals. So, this is the key difference between cetacea and sirenia. Furthermore, Cetaceans do not have hairs, and they have spongy bones while, Sirenians have sparse hairs and heavy bones. Moreover, the Cetaceans have distinct epiphyses and seven cervical vertebrae. Meanwhile, the Sirenians do not have epiphyses but have six cervical vertebrae.

The below infographic lists more differences between cetacea and sirenia in tabular form for side by side comparison.

Summary – Cetacea vs Sirenia

Cetacea and sirenia are two taxonomic orders of aquatic mammals. Cetaceans are large carnivorous aquatic mammals, while sirenians are small herbivorous aquatic mammals. Ganges dolphin, South Asian river dolphin, sperm whale, and blue whale are several cetaceans, while Sea cow, dugong, manate, and manatus are several sirenians. Thus, this summarizes the difference between cetacea and sirenia.

Reference:

1. “Introduction to the Cetacea.” UC Museum of Paleontology.
2. “Sirenian.” Encyclopædia Britannica, Encyclopædia Britannica, Inc.

Image Courtesy:

1. “Anim1754 – Flickr – NOAA Photo Library” By NOAA Photo Library – (Public Domain) via Commons Wikimedia
2. “Dugong dugon (Order: Sirenia), Toba Aquarium” By Joel Abroad (CC BY-NC-SA 2.0) via Flickr