The subphylum - Cephalochordata
includes Amphioxus or
1., Pallas described this animal first.
He named it as Umax lancealatus, He
included this in Mollusca.
2. In 1834, costa described its
3. In 1836, Yarrel named it as
CHORDATE FEATURES OF
1. Presence of dorsal tubural nerve
2. Presence of a long notochord
from anterior end to posterior end
on the dorsal side. Because, it
extends to the cephalic region.
Hence it is called Cphalochordata.
3. Gill silts are present in the
4. Presence of post anal tail.
5. The presence of liver diverticulum.
6. The development of hepatic portal
7. Presence of Myotomes and which
are useful for locomotion.
8. The presence of dorsal, caudal
and ventral fins.
In these characters
1. The excretory system contains
In the chordate world, the presence
of solenocytes is not report-ed. But,
in Amphioxus solenocytes are
associated with Nephridium)’
2. Absence of heart and kidney.
3. Absence of paired limbs or paired
4. Absence of distinct head.
5. Absence of distinct paired sense
6. Gonads are without gonoducts.
Thus cephalochordates will show
many primitive characters
1. Because of its ciliary mode of
feeding, the pharynx is elaborated
with many gill slits. .
2. Oral hood is well developed for
ciliary mode of feeding.
3. Because of its ciliary mode of
feeding the atrium is very well
Thus, Amphioxus shows some
special characters which are
developed because of its ciliary
Cephalochordates show many close
relationship with urochordata.
In some points they differ
1. Presence of gill slits In pharynx.
2. Presence of Endostyle in Pharynx.
3. Presence of Ciliry mode of
4. Presence of atrium.
1. Absence of test.
2. Absence of distinct heart
3. Presence of notoçhord and
nervecord in the adults.
4 Presence of Myotomes in the
In this way Cephalochordates differ
Cephalochordates show some
1. Presence of paired nephridia like
2. Presence of flame cells like
3. Presence of soft body and slug
like appearance like molluscans.
By considering the above facts we
come to a conclusion that
Amphioxus is a chordate animal.
Amphioxus is a degenerate jawless
chordate animal. It mainly shows
chordate features. It differs from
urochordates in some aspects.
Hence, It is separated and kept in a
separate sub phylum called
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