What are the evolutionary characteristics of Chondrichthyes?
Although both groups have many characteristics in common (such as the possession of a cartilaginous skeleton, placoid scales, teeth simply embedded in gums, a spiral valve in the intestine, urea retention habitus, internal fertilization [for which the males have claspers], and the absence of a swim bladder), the two …
When did Chondrichthyes and osteichthyes diverge?
The cartilaginous fishes (Class Chondrichthyes) comprising chimaeras, sharks, skates, and rays are the oldest living group of jawed vertebrates that diverged from a common ancestor of bony vertebrates (Osteichthyes: ray-finned fishes, coelacanths, lungfishes, and tetrapods) in the early Silurian about 420 Ma (Benton et …
What is the sister group to Chondrichthyes?
The Chondrichthyes (cartilaginous fishes) are commonly accepted as being sister group to the other extant Gnathostomata (jawed vertebrates).
How are Chondrichthyes differ from Osteichthyes?
The main difference between Chondrichthyes and Osteichthyes is that the Chondrichthyes is the class of bony fish whose endoskeleton is made up of cartilages whereas Osteichthyes is the class of cartilaginous fish whose endoskeleton is made up of bones.
Is vertebral column present in Chondrichthyes?
Because in package it’s given as vertebrates have notochord replaced by cartilagenous or bony vertebrae but in chondrichthyes section it’s given they have notochord persistent throughout their lives.
Why Chimaera is known as rabbit fish?
Their large eyes, nostrils and teeth, give them a rabbit-like appearance. Hence their collective nickname ‘rabbit fish’.
Do gnathostomes jaws?
Gnathostomes or “jaw-mouths” are vertebrates that possess jaws. One of the most significant developments in early vertebrate evolution was the development of the jaw, which is a hinged structure attached to the cranium that allows an animal to grasp and tear its food.
What are the Chondrichthyes?
The Chondrichthyes (sharks, rays, and chimeras) are a diverse group of animals that occupy a key position in the phylogeny of the vertebrates, as one of their most ancient lineages [ 1, 2 ]. Estimates of the diversification of the group based on DNA sequences are of the order of 300–460 million years ago.
Are there phylogenetic relationships among chondrichthyans?
Several molecular studies have explored the phylogenetic relationships among chondrichthyans ( Douady et al., 2003, Human et al., 2006, Inoue et al., 2010, Lim et al., 2010, Lopez et al., 2006, Maisey et al., 2004, Mallatt and Winchell, 2007, Naylor et al., 2005, Winchell et al., 2004 ). However, most of these have been based on mitochondrial data.
When did the Chondrichthyes diverge from the vertebrates?
Introduction The Chondrichthyes (sharks, rays, and chimeras) are a diverse group of animals that occupy a key position in the phylogeny of the vertebrates, as one of their most ancient lineages [ 1, 2 ]. Estimates of the diversification of the group based on DNA sequences are of the order of 300–460 million years ago.
What gave rise to the Osteichthyes and Chondrichthyes?
During their flowering, the placoderms evidently gave rise to the Osteichthyes (the bony fishes) and the Chondrichthyes (the cartilaginous fishes). Even though the lines of evolution remain to be discovered, it seems quite clear that the two groups evolved independently, the Chondrichthyes appearing much later than the Osteichthyes.