Scoliodon Taboos

EXTERNAL ANATOMY OF GNATHOSTOMES
A. CLASS CHONDRICHTHYES: Scoliodon palasorrah (DOGFISH)
-class of cartilaginous or elasmobranch
-cartilaginous skeleton
-exposed gill slits

2 common species for lab dissection: * Squalus acanthias –Atlantic spiny dog * Squalus suckleyi – Pacific spiny dog

PARTS: 1. Body and skin * Body, SPINDLE SHAPE, advantageous for free- swimming animals * Body, pointed at each other a. TRUNK AND TAIL – provide fins for locomotion b. BODY- clothed with SCALES (each of which bears a tiny spine * Rough feeling of skin caused by the spines * LATERAL LINE – whitish line, along each sides of the body; * Lateral line overlies the LATERAL-LINE CANAL –with
SENSORY CELLS for WATER VIBRATION DECTION.

2. Head- triangular and somewhat flattened * ROSTRUM- pointed extremity * MOUTH- ventral side, bounded by the UPPER AND LOWER JAWS (bears a no. of TEETH arranged in DIAGONAL ROW
*all recent vertebrates are bounded by the upper and lower jaws EXCEPT CYCLOSTOMES * 3 PAIRS OF SENSE ORGANS
-olfactory organs
-eyes
-ears * NOSTRILS –pair of opening in the ventral side of the rostrum * A little flap of skin extends over the center of each nostrils, dividing the opening into 2 passages, by means of which a current of water circulates through the olfactory sac, a rounded sac into which each nostril leads. * OVAL EYES- immovable upper and lower eyelids * behind each eye, INTERNAL EAR is located
-no external ear, ear opening or drum membrane
-connected with the surface of the head by 2 canals: a. Endolymphatic ducts- open by a pair of small pores in the center of the dorsal surface of the head just back of the level of the eyes. * PORES- openings of LONG MUCOUS CANALS imbedded under the skin.

3. Gill Slit- communicates with the cavity of the PHARYX.
-respiratory movements: WATER
ENTERS - MOUTH;
EXITS- GILL SLITS * SPIRACLE/1st GILL SLIT- behind each eye. Circular opening. * 2nd – 6th GILL SLIT- 5 long elongated slits

4. Fins
2 Kinds: a. UNPAIRED or MEDIAN FINS
-arising from the median lines of the animal
-consists of an ANTERIOR AND POSTERIOR DOSRAL FINS & CAUDAL FIN *Caudal fin- asymmetrical type, HETEROCERCAL -consists of LARGE DORSAL and SMALL VENTAL LOBE

b. PAIRED or LATERAL FINS –located at the ventral side if the trunk

* 2 PAIRS OF PAIRED FINS (corresponding to the FORCE and HIND LIMBS of TETRAPODS) a. PECTORAL FINS (anterior pair)
-behind the gill slits b. PELVIC FINS (posterior fins)
-at the junction of trunk and tail
* GENDER IDENTIFICATION : PELVIC FINS
- male: the median side of each pelvic fun is modified into a stout process directed backwards called the CLASPER. * DERMAL FIN RAYS or CERATOTRICHIA
-all fins are supported by these numerous fine parallel flexible rays.

5. CLOACAL APPERTURE/ ANUS
-between the bases of the pelvic fins * UROGENITAL PAPILLA
*Cloaca- end of the digestive tube when this receives the urinary and genital ducts as well as the intestine.
-general throughout vert. EXCEPT in PLACENTAL MAMMALS (during development a fold divides the cloaca into a ventral UROGENITAL CANALS and DORSAL INTERSTINE.

B. CLASS OSTEICHTHYES: TELEOSTS: PERCH
*All common fishes belong to the order Teleostei
-characterized by OSSIFIED SKELETON and a bony flap, the OPERCULUM, covering the gill slits.

1. BODY AND FINS – FUSIFORM SHAPE * TRUNK AND TAIL- clothed with thin overlapping scales, arranged in diagonal rows and set in pockets in the deeper part of the skin. 2. HEAD –covered by the SOFT EPIDERMIS * TERMINAL MOUTH – bounded by well developed JAWS.
-more primitive than the ventral position found in the elasmobranchs. * NOSTRILS- dorsal side of the anterior end of the head
-this arrangement permits a current of water to circulate through the olfactory sac. * EYES- without lids * EARS- behind the eyes.
-invisibly external * GILL COVER or OPERCULUM – posterior and lateral margins of the head
-large flap * GILL OPENING – covers a wide slit in the body wall. * BRANCHIOSTEGAL MEMBRANE-
-attached to the ventral margin of the operculum
-supported by 7 bony rays (BRANCHIOSTEGAL RAYS) * GILL ARCHES- each bears on its outer surface a GILL (consisting GILL RACKERS toothlike processes * GILL SLIT- spaces
-some disappeared and covered by an OPERCULUM
*characteristics of all fishes EXCEPT ELASMOBRANCH
*When fish respires, the mouth opens, the opercula move outward, the branchiostegal membrane unfolds and closes the gill opening; water is thus drawn into the mouth and bathes the gills. The mouth then closes; the opercula move inward; the branchiostegal membrane folds up; and the water passes out through the gill slits and gill opening.

3. FINS- provided with MEDIAN AND PAIRED FINS
*For the former there are an anterior and posterior dorsal fin, caudal fins and ventral or anal fins. * TAIL- HOMOCERCAL (common in bony fishes) * PAIRED FINS- consists of the usual PELVIC AND PECTORAL FINS * LEPIDOTRICHIA- bony flexible jointed ray
-Modified scales

4. OPENINGS * ANAL OPENING – midventral line just in front of the ventral fin * UROGENITAL PAPILLA- depression into which projects a small elevation
*PERCH HAS NO CLOACA
*INTESTINE AND UROGENITAL SYSTEMS ARE OPEN SEPARATELY.
*THIS MARKS THE DIFFERENCES BETWEEN ELASMOBRANCH AND TELEOST FISHES.

C. TYPES OF LOWER FISHES 1. LUNGFISH (Superorder Dipnoi)
Epiceratodus
-small head, stout trunk clothed with large, thin rounded scales (CYCLOID TYPE)
-set in pockets and arranged in DIAGONAL OVERLAPPING ROWS as in TELEOST. * TAIL- DIPHYCERCAl * PAIRED FINS- retained the primitive location

In Lepidosiren and Protopterus, * gill opening * no spiracles * NOSTRILS: located in the underside of the upper lip
DIPNOI- has a WELL-DEVELOPED SINGLE OR BILOBED LUNG (air bladder)
*the lung connects with the esophagus by a duct, and LUNGFISHES CAN BREATHE AIR AND SO SURVIVE DRYING.

2. Polypterus * GANOID SCALES- hard shiny scales of RHOMBOID SHAPE

3. Acipenseri (sturgeon) Order Chondrostei * GANOID SCALES on trunk- hard shiny scales of RHOMBOID SHAPE * ROSTRUM * BARBELS- 4 branched projections
-used as SENSE ORGAN for DETECTION of food. * NOSTRILS: 2 openings * SLITLIKE SPIRACLE above each eye * OPERCULUM supported by a single bone * MOUTH bordered with SENSORY PAPILLAE * JAWS lack TEETH * TAIL: HETEROCERCAL

4. Polyodon (spoonbill) * ROSRUM – expanded into a broad, thin, spatulate structure
-with SENSE ORGAN for FOOD DETECTION * DOUBLE NOSTRILS –in front of eyes
-behind them, SMALL SPIRACLES * OPERCULUM- lacks OPERCULAR BONES and continues into a BRANCHIOSTEGAL MEMBRANE without RAYS. * GILL RACKERS on the GILL ARCHES when OPERCULUM is lifted.
-used to SEPARTE FOOD PARTICLES from the mud. * JAWS- with minute TEETH

5. Lepidosteus (Gar pike) Order Holostei * GANOID SCALES on trunk- hard shiny scales of RHOMBOID SHAPE * NO SPIRACLE * BONY OPERCULUM * TAIL: HETEROCERCAL but approaches HOMOCERCAL

D. CLASS AMPHIBIA
-AMPHIBIANS- lowest land vertebrates

1. Necturus (salamander)
-broad flat head
-no definite NECK
- relatively LARGE TAIL
-SKIN: naked and slimy
-without scales
-moist habitat is necessary
-bears the usual 3 pairs of sense
-EXTERNAL NARES (just back of the upper lips)
- communicate with the mouth cavity through the INTERNAL NARES
*this arrangement permits air to enter the mouth cavity through the nostrils and contrast with the condition in most fishes where the olfactory sacs are blind and have no connection with the mouth cavity.
* In SKATE, an EXTERNAL ORONASAL GROOVE extends from each olfactory sac to the mouth; and by the fusion of the borders of such a groove a closed nasal passage is produced during the embryonic development of land vertebrates.
*Such a nasal passage and internal nares are already present in those fish groups in or close to the line of ancestry of tetrapods.
-SMALL EYES WITHOUT EYELIDS
-INTERNAL EARS
-3 GILLS: * EXTERNAL GILLS – do not correspond to the gills of the fishes, which are INTERNAL * GILL SLITS- between the 1st and 2nd; and the 2nd and the 3rd gills.
-open, as in fishes, into the cavity of the pharynx
* does NOT PASS WATER THROUGH THE GILL SLITS but RESPIRES BY THE MEANS OF EXTERNAL GILLS.
-GULAR FOLD- a fold of skin that passes transversely across the throat.
- TRUNK BEARS 2 APPENDAGES: * WALKING LIMBS- correspond to and have evolved from the PAIRED FINS OF FISHES * UPPER ARM * FOREARM * WRIST * HAND

* FORELIMB * THIGH * SHANK * ANKLE * FOOT
*BOTH HAND AND FOOT BEAR 4 DIGITS (fingers, toes). 1st finger, MISSING.
* TYPICAL NUMBER OF DIGITS FOR VERTEBRATES: 5
-TAIL- flattened tail is bordered by a tail fin which differs from the fins of the fishes in that it contains NO FIN RAYS.
-AMPHIBIA, like the ELASMOBRACHS, HAVE CLOACA
*The position of the limbs with reference to the body is very primitive, especially in the case of the hind limb.
*The hind limbs projects out a right angles to the body, all of its parts on a plane parallel to the ground. In this primitive position the limb has an anterior or PREAXIAL BORDER, or a posterior POSTAXIAL BORDER, and dorsal and ventral surfaces.
*The forelimb, however, is bent downward, and the hand is directed slightly forward.
*This alteration of position is brought about chiefly by an outward torsion of the upper arm, whose former is turned medially, its postaxial border laterally.
*AS A RESULT, THE ANIMAL IS ABLE TO LIFT ITSELFT TO A SLIGHT EXTENT ABOUVE THE GROUND.

2. OTHER SALAMANDERS
-The LARVAE of all salamanders have 3 PAIRS OF EXTERNAL GILLS- but retained in the adult stage only.

3. COMPARISON WITH FROGS AND TOADS
*The hind legs appear to have 4 sections instead of the usual 3.
*EARDRUMS, covering the MIDDLE EAR
* UNLIKE SALAMANDERS, FROGS AND TOADS HAVE A MIDDLE EAR in addition to the INNER EAR.
*TOAD AND FROG ARE DISTINGUISHED from EACH OTHE by THEIR SKELETON and the appearance of WARTY, SQAUTTY ANIMAL with a pair of PAROTOID GLANDS for the TAOD.

E. CLASS REPTILIA
- distinguished by their DRY SCALY SKIN
-GILLS are LACKING in all stages

1. LIZARDS (order Squamata, suborder Lacertilia)
-body is tetrapod in form
- Divisible into HEAD, NECK, TRUNK AND LONG TAIL.
*AMPHIBIANS AND FISHES, LACK A DISTINCT NECK
-BODY: clothed with HORNY SCALES, PLATES and TUBERCLES (which are not detachable structures and are merely cornified thickenings of the EPIDERMIS)
-EYES: movable upper and lower eyelids.
NICTITATING MEMBRANE- 3rd eyelid
-CONSPICUOS EAR
-MIDDLE EAR- lacks in fishes and salamanders
- Modified translucent scale – has histological structure if an eye and might serve some OPTIC FUNCTION.
*Skin folds are common in lizards on throat, neck, side of trunk or mid-dorsal line. Often these can be erected and are then displayed in courtship or combat. They may be limited to male sex
-DEWLAP- a fan that is red in color because the red throat skin shows between the scales.
Much LAREGR IN MALE than in
females
-bears 5 DIGITS
-TERMINATING IN HORNY CLAWS
-Expanded adhesives are common to climb trees
-FEMORAL PORES- openings of sacs which secretes a YELLOWISH WAXY MATERIAL (usually in males). Probably for COPULATION.
-ANUS- transverse slit form
Enlarged scales behind the anus (gender identification for males)

2. SNAKES (order Squamata, suborder Ophidia)
-lacks LIMBS AND EYELIDS
*However, the absence of fore, hind or both limbs is not uncommon in lizards
-HEAD SHIELDS
-MIDDLE EAR is degenerate in snakes and completely concealed from the surface
-VENTAL SHIELD
-ANAL SHIELD * PIT VIPERS- poisonous snakes
-has PIT on the side of the head behind and below the nostrils.
FUNCTION: temperature detectors and enable snakes to determine the presence of a warm object.
-pit vipers have vertically elongated PUPIL OF THE EYE

3. TURTLES
-has reptilian head
-unusually long and flexible NECK
-TRUNK: encased in a hard shell
-TAIL: diminished in length and diameter
-SKIN: usual reptilian conification in a form of large HORNY SHIELDS covering the shell
-SKIN OF HEAD: usually bare
-EXTERNAL NARES- permits the animal to breathe air with only a slight exposure above water (close together at the tip of the head)
-JAWS: lack TEETH instead clothed with HARD HORNY BREAKS
-EYES: lower and upper membranes and NICTITATING MEMBRANE
-CIRCULAR EARDRUM FLUSH
-CARAPACE- MORE ARCHED in FEMALES than males
-PLASTRON
-BRIDGE- connects the carapace and plastron
-CLAWS- LONGER in MALES

4. ALLIGATORS and CROCODILES (Crocodilians)
-Large reptiles of lizards-like appearance and semi aquatic habits.
-have LOWER AND UPPER EYELIDS + NICTITATING MEMBRANE
-EXTERNAL EAR
-SQAURISH AND ROUNDED HORNY THICKENINGS OF THE SKIN
-LEATHER: consists of TANNED INNER LAYER of the DERMIS
-BONY PLATES –at the back
-ALLIGATOR
* SNOUT: broad and blunt
-CROCODILES
* SNOUT: narrow and pointed

F. CLASS AVES
-covered with feathers
-modified forelimbs into WINGS

1. BODY FORM AND SKIN
-portions of the body, as seen in the plucked specimen, bear a general resemblance to those of the turtles.
-HEAD: well developed
-NECK: long and flexible
-TRUNK: shorter and slumber than normal
-TAIL: reduced to a STUMP (UROPYGIUM)
*Ancestors of birds had LONG TAILS like lizards, bearing feathers along their entire length.
-BODY: clothed with feathers
-CONTOUR FEATHER –conceals the shape of birds
2 KINDS: * FLIGHT FEATHERS – large, stout feathers of the WINGS and TAIL. * COVERTS- smaller feathers. Covers the BASES OF THE WING AND TAIL AND GENERAL SURFACES.
-FILOPLUMES/ HAIR FEATHERS –hair like processes.
-FEATHER FOLLICLES- deep pits. Not uniformly distributed in the body but occurs in tracts

2. HEAD
-BEAK –consists of upper and lower jaws incased in horny sheaths.
-TEETH are ABSENT
*extinct birds possess them
-CERE- cushion like protuberance
-EXTERNAL NARES
-LARGE EYES with UPPER AND LOWER LIDS +NICTITATING MEMBRANE
-EAR-observable only in PLUCKED birds
-MIDDLE EAR –has sunk below the surface, with the resulting formation of an EXTERNAL EAR
-EXTERNAL AUDITORY MEATUS- deep narrow passage which lead to the middle ear
-The skin around the entrance to the meatus extends to elevate as a fold, and this fold plus the meatus forms the EXTERNAL EAR.

3. TRUNK
-it is the presence of the BREAST MUSCLES which produces the plump contour of the birds.
- 2 PAIRS OF LIMBS: * ANTERIOR LIMBS: wings * HIND LIMBS: feet (biped mode of walking for birds)
-PARTS OF THE WINGS * UPPER ARM: SHORT, directed POSTERIORLY, slightly twisted on its axis so as to bring the preaxial margin to the dorsal side * FOREARM: LONGER and directed FORWARD * WRIST AND HAND: fused together
-3 DIGITS * 1st – projection found just below the JOINT between the FOREARM and WRIST. * 2nd –TERMINAL POINT of the WING * 3rd- cannot be seen EXTERNALLY

-REMIGES- GREAT FLIGHT FEATHER OF THE WING
-PRIMARIES- those of the HAND
-SECONDARIES- FOREARM -TERTAIRIES OR HUMERALS- UPPER ARM
-4 DIGITS in the HIND LIMBS – 5th absent. Terminates in CLAWS

4. TAIL
-RECTRICES- half circle of a large flight feather
-ANUS/CLOACAL APPERTURE- under the base of the tail. With protruding lips
-UROPYGIAL GALND- a prominent papilla from which the bird OBTAINS OIL for PREENING its feathers.

G. CLASS MAMMALIA
-warm blooded vertebrates
-provided with hair (FUR)
-mammary glands

1. EXTERNAL ANATOMY OF CAT (Order Carnivora) or the rabbit (order Rodentia)
-HEAD, NECK, TRUNK and TAIL
-VIBRISSAE or whiskers – have a RICH NERVE SUPPLY and serves as an IMPORTANT TACTILE ORGAN
*Large size of head caused by the great development of the inclosed brain
-HEAD
* FACIAL –anterior (in front of the eyes) * CRANAIL- posterior
-MOUTH: has well -developed LIPS (HARELIP)
-INCISOR TEETH
-EXTERNAL NARES
-EYES: lower and upper lids + NICTITATING MEMBRANE
-EARS: PINNA- external fold * Springs from the rim of the EXTERNAL AUDITORY MEATUS
*Pinna and Meatus constitute the EXTERNAL EAR
-TRUNK
* THORAX –anterior chest. Supported by the RIBS * ABDOMEN
-NIPPLES or TEATS
-MAMMARY GLAND- opening of the milk glands
-2 PAIRS OF LIMBS: * UPPER ARM –thigh. Terminate in CLAWED DIGITS (5 in front, 4 behind -1st toe absent)
*claws of cat, RETRACTILE
*Pag mas ventrally projected yung body, mas mataas sa groung (ancestors –extends laterally from the body)

-POSITION OF THE PARTS OF THE FOOT IN WALKING * DIGITIGARDE- use of DIGITS
Ex.
Cat and rabbit * PLANTIGRADE- walks on SOLE FOOT
Ex. Human * UNGULIGRADE- use of NAILS
Ex. Horses and cattle and other ungulates
-NO CLAOCA
-ANAL and UROGENITAL OPENINGS are SEPARATE
*the region which includes these openings is termed PERINEUM
-ANUS –located on the midventral line
-PERINEAL SPACE or INGUINAL – found on each side of the anus, a deep hairless depression (found in rabbits)
-INGUINAL GLAND- not visible externally. Source of ODORIFEROUS SECRETION
-GREATER LIPS or LABIA MAJORA – fold of skin found in female urogenitals
(VULVA- opening)
-PENIS or ORGAN OR COPULATION – in front of the anus
-SCROTUM or SCROTAL SAC- double pouch which houses the TESTES
- PREPUCE or FORESKIN- fold of skin in cats
*Cat’s penis –invisible enxternally
*the UROGENITAL in MOST MALE MAMMALS is on the TIP of the PENIS (for copulation and urine discharge)

2. PRIMITIVE MAMMALS
-MONOSTREMES
* PLATYPUS * SPNIY ANTEATERS
-adapted for ant-eating by means of CLAWED FEET for OPENING THE NESTS and a long pointed snout and extensile
tongue.
-SPINES
-MALES: armed on the hind legs, with a hollow horny spur connected with a POISON GLAND and capable of inflicting a severe wound.
-PRIMITIVE MONOSTREMES: resemblance with reptiles * Reptilian type of UROGENITAL SYSTEM –uniting with the INTESTINE to form a CLOACA so that there is but ONE EXTERNAL OPENING. * Lay their eggs like reptiles * Echidna – carry eggs and young in a ventral pouch of skin (not homologous to marsupials )
-TEATS are LACKING in MONOSTREMES
-MILK GLANDS- open directly on the skin by several apertures.

-MARSUPIAL- much LESS PRIMITIVE MONOSTREMES * MARSUPIUM – ABDOMINAL POUCH
-evident only during the breeding season * Have TRUE TEATS * LACKS PLACENTA- cannot nourish embryos to an advanced state inside the maternal body * UROGENITAL SYSTEM- retain some reptilian resemblance
-SHALLOW CLOACA is PRESENT

Source: Hyman, LH. 1965. Comparative Vertebrate Anatomy. Chicago, USA: The University of Chicago Press