Question

Interpret the phylogenetic tree based on the evolution of Chondrichthyes.

M6 Tree Explorer Image Subtree View Compute Ancestors Caption Help 礨咕鼎冫 § E ) 針ピ冠 Tree# 1 of 3 lancet1 Branchiostoma_floridae -sea-lamprey,Petromyzon marinus electn ray_Narcine_brasiliensis frog Rana_drayton Carcharias taurus_grey nurse_shark trout Oncorhynchus-mykiss-las lungfish Protopterus sp : 319

Answer 1

The Chondrichthyes are considered the oldest existing jawed-vertebrates related to bony vertebrates .The two subclasses of Chodrichtyes, Holocephali and Elasmobranchii are believed to have diverged 410 mya and become more diversified in the Devonian.Some defining characteristics of Chondrichthyes are

internal fertilization by the use of pelvic claspers,

heterocercal tails,

placoid scales,

cartilage skeletons,

teeth unattached to jaws,

and the absence of swim bladders

There are two subclasses of chondricthyes-

Subclass chimeras (Holocephali): 1 order, 3 families and ~43 species. Fish-like bodies, enigmatic, and live in deep water.

Subclass Elasmobranchii: 17 orders, 52 families ~1200 species. Include rays, skates, and sharks. Flattened bodies, benthic.