One feature not unique to vertebrates is the presence of a notochord, which is a flexible rod-like structure that provides support. While vertebrates have a more complex backbone and nervous system, notochords are also found in other animal groups, such as cephalochordates and some invertebrates, indicating a more primitive form of structural support. This evolutionary trait highlights the shared ancestry among different animal phyla.
a vertebral column or backbone
Vertebrates do not have exoskeletons.
Not all vertebrates have tails.
external skeleton
All vertebrates have a vertebral column (i.e a backbone). This is the main feature.
they are warm blooded
"Vertebrata" more accurately describes the morphological characteristic of the group, as it refers to the presence of vertebral column or backbone, which is a defining feature of vertebrates. "Craniata" focuses solely on the presence of a skull, which is not unique to vertebrates.
A Jaw Eggs that would not dry out
all vertebrates are chordates because vertebrates are the sub- group of phylum chordates and also it follow one of the important feature of the chordates i.e. presence of notochord whereas all chordates are not vertebrates because some chordates are cephalochordates, urochordates.
Dens are unique to the axis.
Aristides identified Christianity as the unique feature of the Roman Empire.
Mezcal is a type of liquor that sometimes contains a worm as a unique feature.