Subphylum Vertebrata

Superclass Agnatha

Comparative anatomy of Chordates

Lect. 5

Asst.lec. Sawsan S. Hameed

Biology Department

Tishk international University

2021-2022

Objectives

- Understand the general characteristics of

Gnathostomata

- Differentiate between classes of Gnathostomata

- Describe and classify different species of

Gnathostomata

- Know the 3 orders of Chondichthyes, their

classification with examples of each

Class Placodermi

fossil

Class

Chondrichthyes

Class

Osteichthyes

Agnatha

jawless vert.

Gnathostomata

jaw Vert.

Super class Super class

Superclass Gnathostomata (jaw vert)

General Characteristic

➢ Vertebrates with jaws with teeth . ex; Human, fish, dogs,

cows, goats, cats

➢ paired nasal sacs.

➢ paired appendages (paired pectoral and pelvic fins)

supported by an internal skeleton

➢ Divided into 3 classes;

➢ Class Placodermi (extinct)

➢ Class Chondrichthyes (Cartilaginous fish)

➢ Class Osteichthyes (Bony fish)

Class

Placodermi

Class

Chondrichthyes

C l a s s

O s t e i c h t h y e s

Selachi

or pleurutremata

Rajiformes or

Hypotremata

Chimaeriformes

Teleostie

Holostei

Chondrostei

Crossopterygi

Dipnoi

Superclass

Gnathostomata

(extinct)

• Gr., Chondros= cartilage, ichthys =fish

• General characters

➢ Large, about 2m long, body fusiform.

➢ Most of the members are marine and are predators.

➢ Skin is covered by placoid scales.

➢ Endoskeleton is entirely cartilaginous, notochord

persistent but reduced,

➢ vertebrae complete and separate.

placoid scales

Class Chondrichthyes (cartilaginous fish)

➢ Mouth is subterminal in position, two olfactory sacs that

do not connect to the mouth cavity.

➢ Jaws are with sharp teeth.

➢ True operculum is absent, instead, gill slits are present.

➢ paired pectoral and pelvic fins are present in addition to

the dorsal fins.

Class Chondrichthyes (cartilaginous fish)

➢ Possess a variety of sensory systems, including senses

of smell, vision, hearing & sensory lateral line that

allows them to detect sound, vibration, and pressure

changes.

➢ Unisexual fishes, fertilization Internal

➢ males having claspers for reproduction.

➢ Clasper is a modified copulation organ from pelvic fin

➢ Gonads paired, reproductive ducts open into cloaca

Class Chondrichthyes (cartilaginous fish)

Gr., Selakhe= a shark.

➢ Body typically spindle shaped.

➢ Gill slits 5 to 7, laterally located.

➢ Pectoral fin moderate, constricted at base.

➢ Caudal fin is heterocercal.

Scientific classification

Kingdom: Animalia

Phylum: Chordata

subphylum Vertebrate

Class: Chondrichthyes

Order: Selachi

Order 1: Selachi (Squaliformes)

➢ General features.

➢ Mouth is subterminal in position with hard

jaws are & numerous sharp teeth.

➢ Brain is developed & Powerful sensory

system helps in detection of food.

➢ Swim with high speed. The eggs are large & Gestation periods

for two years the longest period of any known living vertebrata

gill slits

mouth

Order 1: Selachi (Squaliformes)

Whale shark Rhinocodon White shark Carcharodon

Basking shark Cetorhinus maximus Zebra shark Stegostoma

Hammer headed shark Dogfish Chiloscyllium

Dogfish Scolidon Dogfish Mustelus

Spiny dogfish Squalus Sawshark Peristiophorus

(Gr., hypo=below , trema= opening).

➢ Body flattened, Spiracles large highly functional.

➢ Gill slits 5 pairs located ventrally so named Hypotremata.

➢ Pectoral fins enlarged like wings, fused with the head and body and used in swimming.

➢ The tail has changed to a whip-like organ of defense.

➢ They spend much time on the bottom

of the sea

➢ In giant mantas or devil fishes

(Manta, Mobula) many have

pectoral fin spread of 6 meters and

weight nearly half ton.

Scientific classification

Kingdom: Animalia

Phylum: Chordata

subphylum Vertebrate

Class: Chondrichthyes

Subclass: Elasmobranchi

Order: Hypotremata

Order 2: Rajiformes or Hypotremata

Eagle ray Myliobti

Pectoral fin

Sawfish Pristis

Guitar fishElectric ray Torpedo

Those are remnants of a line diverged from the shark lineage

General features

➢ Body is somewhat compressed, and the skin is naked in adults.

➢ Endoskeleton is cartilaginous.

➢ Persistent notochord and poorly developed vertebrae.

➢ Bony plates are on the jaws instead of teeth used in crushing molluscan shells.

clasper

Scientific classification

Kingdom: Animalia

Phylum: Chordata

subphylum Vertebrate

Class: Chondrichthyes

Order: Chimaeriformes

Order: Chimaeriformes

EX; ratfish, rabbitfish, spookfish and ghostfish,

➢ Upper jaw is completely fused to the cranium, most unusual feature in fishes.

➢ Untrue fleshy operculum hides the 4 gill slits.

➢ Pectoral fin broad and leaf-shaped.

➢ Males possess pelvic clasper on the head.

➢ Cloaca absent, anus and urinogenital aperture separate.

➢ Tail slender and whip-like.

➢ Feed mainly on benthic invertebrates

➢ Most species inhabit the deep

sea. Examples: Ratfish

Chimaera, and Harriotta

Order: Chimaeriform

Ratfish Chimaera

Longnosed spookfish

References

For further reading please see:

Charles K. Weichert (2017). Elements of chordate anatomy. 3rd edition.

The McGraw−Hill Companies, New york.

Comparative anatomy | Definition, Examples, & Facts |

Britannicahttps://www.britannica.com › science › comparative-anatomy

Kardong, Kenneth V. (2019). Vertebrates: comparative anatomy, function,

evolution (8th edition). New York.

De Iuliis, G., & Pulerà, D. (2019). The dissection of vertebrates. 3rd

edition. Academic press. Elsevier, London.

Kenneth, S. S. (2017). The unity of form and function. 8th edition. The

McGraw−Hill Companies,. New york.

Comparative Anatomy. wwww.health.zone/