A slide presentation on the evolution of the verterate skeleton

1. BY
GROUP 4
COURSE CODE: ANA 401 (COMPARATIVE ANATOMY AND ANIMAL HANDLING)
TO
The Department Of Human Anatomy And Cell Biology
Delta State University, Abraka. Delta State.
February 2015.
A PRESENTATION
THE COMPARATIVE ANATOMY OF THE SKELETAL SYSTEM
ON

2. Comparative anatomy is the study of the similarities and
differences in the anatomy of different species.
It is closely related to evolutional biology and phylogeny
 The skeletal system is the hard component of the body structure
- Provides reliable information about the specific adaptations of
vertebrates such as posture and locomotor adaptations
- Due to its hardness and durability, skeleton becomes fossilized
and the study of past vertebrate life is mostly based on fossils

3. Functions of Skeleton
- Protects the viscera
- Contributes to ventilation of the lungs
- Store for various minerals
- Provides rigidity support to the body
- Aids locomotion
- Gives shape to the body
- Provides series of firm and hinged segments needed for
locomotion in conjunction with the muscles

4. Types of Skeleton

5. ORIGIN OF BONE
 Earliest known fossils are fishes
Dates back to late Cambrian & early ordovician times (500mybp)
Found in scattered areas of N.America, Greenland & Spitsbegen
Small in size & varies; jawless & no paired fin
Head covered with a thick plate of Bone.

6. Earliest Kinds of Vertebrates
Complex diversity of forms
Relationships were deduced from evolutionary convergence
Earliest recognizable fish fossils belong to group – Pteraspidomorphi
-- First appear in deposits laid down
in early ordovician times
Other early vertebrate fossils are from the early Ordovician of baltic
E.g Astrapsis desderata

8. Other Bizarre forms of Pteraspidoforms

9. Cephalaspidomorphi
 Earliest fossil found in mid-ordovician deposit
 Best known cephalaspidomorphii
group cephalaspidoforms
order - Hemicyclapsis

10. Heavily amoured Pteryspidomorphii
and
Cephalospidomorphii

12. PHYLOGENY

13. TWO KINDS OF SKELETAL TISSUE – Cartilage and Bone
Cartilage is a form of connective tissues that has an intercellular matrix
composed of a complex rubbery protein.
Has connective tissue fibers and chondrocytes

14. BONE
 Consist of matrix held throughout by connective tissue fibers
Osteocytes are burried within the C.Tissue

15. CONTRIBUTIONS OF SKELETON TO MODERN DAY VERTEBRATES

16. EMBRYOGENIC DEVELOPMENT OF THE
SKELETON
Embryogenic skeleton development begins when the embryo consist of:
 Ectoderm
 Endoderm
 Longitudinal Primitive streak
(i) Notochord (gives rise to longitudinal axis of the embryo)
(ii) Third basal layer – Mesoderm
The mesodermal sheet becomes differentiated into
• Paraxial node
• Lateral plate
• Sclerotome

17. NOTOCHORDAL DEVELOPMENT
(a) Elongation of the Notochordal process
(b) Notochordal canal breakdown on the endodermal side
forming a notochordal plate
(c) The notochordal plate folds up forming the notochord
Transverse section of a chick embryo

18. Skeletal system is of mesodermal origin it begins with the
formation of blastema (any aggregation of embryonic
mesenchymal cells which will differentiate into tissue such as
muscle , cartilage, or bone).
This cell then develop into their fibroblast and osteoblasts.
 Fibroblast form collagen
 Osteoblast form bone cells
 NOTOCHORD
 The primitive axial skeleton, replaced by the vertebral column
 Unsegmented and composed of dense fibrous connective tissue
 The first skeletal element to appear in the embryo of chordates

19. Regional Classification of the Skeletal System
 AXIAL and APPENDICULAR SKELETON: Axial is used to describe the
portions of the skeleton that forms the central axis of the body. The
appendicular skeleton consists of the Limbs and the girdles.
 CRANIAL and POST-CRANIAL SKELETON: The cranial portion of the
skeleton consists of the cranium, the mandibles and the hyoids. The post-
cranial skeleton is everything else apart from the skull such as the
vertebrae, ribs and the limbs bone.

20. SKELETAL SYSTEM OF REPTILES

21. INTRODUCTION
 Reptile are derived from latin world repto which means to creep
 The first reptiles to evolve 300 million years ago were called Anapsids.
 Reptiles are class of the chordate phylum.
 Most of the reptiles have scaly skin and feet with claws on their toes.
 Reptile have bilateral symmetry which means that the right sides of reptiles are
mirror images of the left side.
 Reptiles have basic axial skeleton with vertebral column. The skeletal system of
reptile evolved for support and movement on land.

22. SKULL
 The turtles and primitive reptiles have
no temporal fenestra, therefore called anapsids
 Mammal-like reptiles which have gone into
extinction like the dinnosaurs have synapsid type of skull
 Crocs and lizards have the diapsid type of skull

23. Skeletal systems in turtles
 Turtles are unique. They have large rigid skeleton
with an oval shell
 They have both an internal and external skeleton
 The main purpose of the external skeleton of turtle is
for protection and support for the internal organs.
 It comprised of a bony shell while the internal
skeleton of turtle provide an anchor for the muscle
support.
 They have
7 mobile cervical vertebra
10 thoracic
2-3 Sacral
12 caudal vertebra

24.  The femur is the bony element of the thigh, the tibia and fibula are the bony
elements of the shank.
 The pelvis is composed of 3 pairs of bones: pubis ischium and ilium. The
pubis and the ischium forms the ventrally positioned part of the pelvis.
 The two ilia are oriented dorsoventrally, articulate with the sacral vertebrae
and attach the pelvis to the carapace via ligaments.

25. Skeletal system in Snakes
• Snake’s bones have a very complex structure with many joint, so
snakes can swallow much bigger objects than its own head.
• Snake's ribs are attached to most of their vertebrae--which total
between 130 to 500
• The bones in the skull are connected to elastic ligaments, and the
joints of the jaw are double hinged and positioned in the
posterior aspect of the skull

26. SKELETAL SYSTEM IN PISCES
SCIENTIFIC CLASSIFICATION:
• Kingdom- Animalia
• Phylum- Chordata
• Class- Pisces
GROUPS
 Jawless fish
 Armoured fish
 Cartilaginous fish
 Ray-finned fish
 Lobe-finned fish

27. • The skeleton which forms their support structure could
either be made of cartilage, in cartilaginous fish,bone and
cartilage in bony fish and the notochord in jawless fishes .
• The class Pisces have endoskeleton also referred to as internal
skeleton, that inside the body as in mammals and aves.
• The main skeletal element is the vetebral column, composed of
articulating vertebrae which are light weight but strong.
• The main external features of the fish are the fins which are
composed of either bony or soft spins called rays which with
the exception of caudal skin have no direct connection with
the spine. They are supported by the muscle..

28. EXOSKELETON IN PISCES
There are four principal types of fish scales.
• Placoid scales, also called dermal denticles made up of dentin
E.g: sturgeon and Redfish
• Ganoid scales which are flat with little overlapping e.g shark
and rays
• Cycloid scales are small oval-shaped scales with growth rings
e.g minnow and trout
• Ctenoid scales are similar to cycloid scales but bear spines e.g
Perch

30.  OPERCULAR: pair of bony plates covering the gill opening.
 RAY OF THE ANTERIOR DORSAL FIN: each of the small bones forming the
front fin on the back of a fish
 RADIAL CARTILAGE: elastic substance of the radius.
 RAY OF THE POSTERIOR DORSAL FIN: each of the small bones forming the
rear fin on the back of a fish.
 NEUTRAL SPINE: spines containing part of the nervous system
 VERTEBRA: each of the bones forming the neural spine of a fish.
 HYPURAL: bone to which are attached the spiny rays of the caudal fin of a
fish.
 CAUDAL FIN RAY: each of the small bone forming the tail fin of a fish
 ANAL FIN RAY: each of the small bones forming the fin behind the anus of a
fish

31.  RADIAL CARTILAGE: elastic substance of the radius
 RIB: each of the bones forming the thoracic cage
 PELVIC FIN RAY: each of the bones forming the fin beneath the pelvic girdle
 PECTORAL FIN RAY: each of the bones forming the chest fin.
 PELVIC GIRDLE: set of bone forming the pelvis
 CLAVICLE; shoulder bone
 LOWER JAW; mandible
 UPPER JAW; upper part of the mouth
 ORBIT;cavity of the skull that contains the eye
 SKULL; bony case of the brain of a fish.

32. SKELETAL SYSTEM IN AMPHIBIANS
•Structurally homologous to that of tetrapods with little variations
•They have the anapsid type of skull attachment.
•Amphibians have a metautostylic type of jaw attachment.
•The bones are hollow and light-weighted
•Pelvic girdle is well developed and attached to the backbone by a pair
of sacral ribs
•The ilium slopes forward enabling the body to be held closer to the
ground
•Have four limbs except the legless caecilians with reduced or no limbs

33. • They have the Amphicoelus, procoelus and opisthocoelous shaped centra
• The amphicoelus and opisthocoelus centra are found mostly in salamanders.
• The ribs are poorly formed and never reach the sternum
• Primitive amphibians had a solid, triangular shaped pelvic girdle with the
ilium forming the apex.
• The pubis can be distinguished from the ischium by having an obturator foramen.
• In frog, the pelvic girdle has a long anteriorly inclined ilium and cartilaginous pubis.
• All 3 bones take part in formation of the acetabulum

34. Skeleton of Frog, salamander and caecillian

35. The Pectoral Girdle
• The pectoral girdle is present in the anterior part of the trunk.
•It is connected to the axial skeleton dorsally with muscles and
ligaments
•The os innominatum has the dorsal scapular part and ventral
coracoid part.
•Stouter scapular on the lateral side and the supra scapula
formed of calcified cartilage
•The clavicle membrane bone is present antero-ventral to the
pectoral girdle.
•The coracoid part possess uralid and in front of it is the calcified
cartilaginous precoracoid along with another strip
cartilaginous epicoracoid bones
•Closely associated epicoracoids

36. Sternum lies in mid central line of the chest
Anterior Pre-sternum
Omosternum (x-shaped)
Cartilaginous episternum
Posterior Purt-sternum
Mesosternum (stout bone)
Xiphisternum (flat)

37. SKELETAL SYSTEM OF AVES
Aves (birds) are group of vertebrates that have wings, feathers, hollow bones
and numerous other adaptations for an aerial life style.
Classification
Group and species
Skeleton
•Aves inherited their basic skeleton from their reptilian ancestors.
•compared with other vetebrates, birds have a body plan that shows many
usual adaptations mostly to facilitate flight.
Skull: Skull bones in adult birds are fused and do not show cranial sutures
•They have a diapsid skull which weight 1% of their total body weight.
•A light toothless beak which replaces the bony, heavy toothed jaw of reptiles.

38. The Vertebrae
• The spine of birds has cervical, thoracic, lumbar and caudal region with
the number of cervical vertebrae highly variable and flexible.
Thorax and Sternum
• Birds are the only vertebrate animal to have a fused
collar bone (furcula) which is located at the bird chest
• Birds have uncinate processes on their ribs
• and also a sternum
Pectoral Girdles
• Birds pectoral girdle is made up of sternum, clavicle, coracoid and
scapular which forms the furcular

39. Pelvic Girdle
• Is an extensive fusion of bones of the pelvic region to provide staff
support for the legs in order to deal with the stress of take off and landing.
• It consist of synsacrum, caudal vertebrae and at the end of the spinal
column is the pygostle
Wings
• The wing consist of the humerus which is short compared to the total
length of the pulling and withstand the pulling of the flight muscles,
• The radius and ulna which form support for the mid – wing
• The carpometacarpus, which form the third major section of the bird
wing.

41. Leg and foot
• The leg is composed of a fairly standard femur, with knee between the
femur and the fibula and tibiotarsus.
• The foot is a very important appendage for a bird being the only
source of support when standing, walking and running on a variety of
surface.
• The shape and size of the claws and the arrangement s as well as the
length of the toes and the degree of webbing are all dependent on
what a bird uses its feet for and where it live.

42. Skeletal System of Mammals
•Mammals are vertebrates by
definition
Outline of Skeletal Skull
3 parts
1. Braincase
2. Rostrum
3. Lower Jaw
Some of the main bones of the skull
• Nasal Bones
• Maxillary bones
• Frontal Bone
• Parietal Bone
• Occipital Bones
• Dentary Bones

43. VERTEBRA COLUMN
• Cervical Vertebra
• Thoracic Vertebra
• Lumbar Vertebra
• Sacral Vertebra
• Caudal Vertebra

44. LIMBS AND GIRDLE
LIMBS
• Upper limb
• Lower limb
GIRDLES
• Pectoral girdles
• Pelvic girdle

45. HETEROTOPIC (MISCELLANEOUS) BONES
Bones that develop by endochondral or intramembranous ossification
 SESAMOID BONE – bones embedded in or interrupting tendon
 the largest is patella or knee cap
 Baculum (os penis) – bone in the penis of carnivores, bats, insectivores,
rodents, and some primates
 Additional small bones are found in the different structures among
TETRAPODS:
 in the eyelids of CROCODILIANS
 in the crest of a BIRD
 in the snout of PIGS
 at the base of the external ear of some RODENTS

46. Similarities and differences in vertebrates
Comparative anatomy of the skeletal system
Organ
system
Jawless fishes Cartilaginous
fishes
Bony fishes amphibians reptiles birds Mammals
Skeletal
system
They possess
notochord no
axial and
appendicular
skeleton
Axial and
appendicular
Made up of
cartilages
Axial and
appendicular made
up of bones and
cartilages
Axial and
appendicular made
up of bones and
cartilages
Axial and
appendicularmade
up of bones and
cartilages
Axial and
appendicular made
up of bones and
cartilages
Axial and
appendicular
madew up of
bones and
cartilages

47. •Jawless fish (paleostylic) – these fishes are known as
agnathas e.g. lamprey and hagfish they don’t have jaw. They
also don’t have paired fins rather they possess notochord
which supports them during their embryonic.
•Cartilaginous fish (chondrichthyes)- these are fishes that
their skeleton is made up of cartilages rather than bones.
They also possess jaw e.g. sharks and rays (string rays)
•Bony fishes- they are made of bones and cartilages but more of bones
than cartilages. Bony fishes were thought to have gone extinct until 1938
when they were rediscovered. (National geography news) 1st august 2007,
reported a discovery by Philippe janvier, a paleontologis. A study carried
out by Carrol Robert L. Hallam, Anthony et al (1977) on the coelancanth
pattern of evolution.

48. skeletonComparative anatomy of the skull of
vertebrates
Vertebrates Type of skull
Fishes Euryapsid
Amphibians Anapsid
Reptiles Anapsid
Birds Diapsid
Mammals Synapsid
Osborn et al (1903) use temporal fenestrals to classify vertebrates into different types of skulls. These include:
Comparative anatomy of the axial skeleton

49. Vertebrates Vertebral column Types or central
Fish Anterior and posterior or
Trunk and tail
Amphicoelous
Reptile 4-5 distinct regions Procoelous
Amphibians single vertebral column Amphicoelous,
Birds 3 regions Heterocoelous
Mammals 5 distinct regions Acoelous
Comparative Anatomy of the Vertebral Column

50. Vertebrates Ribs Sternum
Fish present Absent.
Amphibians present Present in some
Reptile Most do not have but a
few do e.g snakes.
Present in some
Birds present Present
Mammals present Present
Comparative Anatomy of the Ribs and Sternum

51. Vertebrates Girdlie Fin/limb
Fishes Large pectoral girdle fins no limbs
Amphibians Long pectoral girdle Limbs
Reptiles Various shapes of girdles Limbs
Birds Large pectoral girdle Limbs
Mammals Long and expanded pectoral
girdle
Limb –uniform
and specialized
Comparative anatomy of the appendicular skeleton
Girdle and fin/limb

52. Girdle of fish.
The pectoral girdle of fishes is larger and more complicated than their pelvic girdle. They include one or more replacement or
dermal bones. They possess 3 types of fins. These are:
•Dorsal fins- found in the mid-dorsal region
•Ana fin- found between the anus and tail
Both together prevent the fish from turning around the vertical and longitudinal
axis
•Caudal fin- this attaches to the posterior side of the tail and they are divided into 4 based on shape and
size of the spine of backbone. These include:
Diphycercal- the spine runs straight the entire length of the fin and divide it into two equal
dorsal and ventral lobes eg lamprey and hagfish.
Heterocercal- the spine is tilted upward and to divide the fin into a larger
dorsal lobe and a ventral lobe. eg sharks
Hypocercal- the spine is tilted downward dividing the fin into a larger ventral lobe than a
dorsal lobe eg ostracoderm (eg lamprey)
Homocercal- the fin is attached posterior to the tail eg teleost

53. Girdle of tetrapods
Girdles in tetrapods are relatively the same except for some variations for instant in birds and mammals:
Birds
•They have blade-like scapula that is oriented parallel to the spine. They have large anterior coracoids that articulate with the
sternum
•The two clavicle fuses ventrally to form the furcula or the v-shaped wish bone
Mammals
•Unlike the bird they possess posterior coracoids which fuse with the scapula to form
the coracoid of the scapula
•Their clavicle is not fused like the birds but articulates with the sternum anteriorly.
Pelvic girdle in tetrapod
The pelvic girdle of tetrapods are relatively the same .
•Pubis- located anterioly
•Ischium- located posteriorly
•Dorsal illum which articulates with one or more sacral vertebrae
Upper axis and lower long axis
Comparative anatomy of the vertebra column-
the are about 5000 species of animal in earth having a vertebra column (David Krogh,
2010)

54. conclusion
 Comparative anatomy of the skeletal system is the study of the similarities and differences
of the skeletal system in vertebrates. These vertebrates includes, mammal, birds, reptile,
amphibians and fish.
 The skeletal system is made of bones and cartilages which forms the axial and
appendicular skeleton.
 Vertebrates skeleton is derived from the dermal amour of primitive jawless fishes
 The skeletal system creates an awareness on the evolution of vertebrates and it is the basis
for evolutionary studies.
ANATOMY.
DELTA STATE UNIVERSITY, ABRAKA
Thank you