PHERETIMA EXCRETORY AND NERVOUS SYSTEM -PRACTICE BITS

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1. (A) : Septal nephridia in Pheretima eliminates nitrogenous wastes from blood as well as coelomic fluid
 (R) : They are enteronephric
 1) Both A & R are true and R explains A
 2) Both A & R are true & R does not explains A
 3) A is true, R is false   4) A is false, R is true
2. (A) : Septal nephridia in Pheretima collect the eleocytes ingested by the amoebocytes to the exterior
 (R) : They are open type
 1) Both A & R are true and R explains A
 2) Both A & R are true & R does not explains A
 3) A is true, R is false   4) A is false, R is true
3. (A) : Seminal vesicles of earthworm are called septal pouches
 (R) : These are formed from septa
 1) Both A & R are true and R explains A
 2) Both A & R are true & R does not explains A
 3) A is true, R is false   4) A is false, R is true
4. (A) : Only one earthworm hatches out from a cocoon
 (R) : In cocoon only one egg is present
 1) Both A & R are true and R explains A
 2) Both A & R are true & R does not explains A
 3) A is true, R is false   4) A is false, R is true
4. (A) : Blood in dorsointestinal blood vessels contains more nutrients in Pheretima
 (R) : In the intestinal region of Pheretima each segment contains two pairs of dorsontestinal blood vessels
 1) Both A & R are true and R explains A
 2) Both A & R are true & R does not explains A
 3) A is true, R is false   4) A is false, R is true
5. (A) : Earthworms are described as ureotelic animals
 (R) : Urea is the major excretory product in earthworms
 1) Both A & R are true and R explains A
 2) Both A & R are true & R does not explains A
 3) A is true, R is false   4) A is false, R is true
6. (A): In Pheretima, coelomic fluid cannot be exchanged between 10th and 11th segments
 (R): 10th and 11th segments in Pheretima are separated by non perforated septum
 1) Both A & R are true and R explains A
 2) Both A & R are true & R does not explains A
 3) A is true, R is false   4) A is false, R is true
7. Following are the statements about nephridia  in Pheretima
 1. Micro nephridia are attached to the inner surface of body wall
 2. The straight lobe of the septal nephridium is continued into the distal limb of the twisted loop
 3. Pharyngeal nephridia are as large as the septal nephridia but like the integumentaries they are exonephric
 Which of the above are correct
 1.All are true 2. Only 1&2 are true
 3. Only 1&3 are true 4. Only 2&3 are true
8. Glands of Pheretima helpful for the formation of spermatophores are
 1. Accessory glands 2. Prostrate glands
 3. Lymph glands 4. Blood glands
9. Ganglia present on the dorsal side of alimentary canal in Pheretima are
 1. Supra oesophageal ganglia
 2. Sub pharyngeal ganglia
 3. Supra pharyngeal ganglia
 4. Segmental ganglia
10. In Pheretima, number of ganglia present in the nerve ring
 1. 4 2.2 3. 12 4. 8
11. Receptors of earthworm sensitive to ground vibrations are
 1. Epidermal receptors
 2. Photo receptors 3. Buccal receptors
 4. Chemo receptors
12. In Pheretima, nerve ring is formed around
 1. Pharynx 2. Oesophagus
 3. Gizzard  4. Buccal chamber
13. Double ventral nerve cord in Pheretima starts from
 1. 3rd segment 2. 4th segment
 3. 5th segment 4. 2nd segment
14. Distinguishing feature of the buccal receptor cells in Pheretima is
 1. Presence of ‘L’ shaped lens
 2. Connected ti nerve fibre
 3. Presence of nuclei in deeper part
 4. Consisting of a hyaline substance
15. Number of nerves arise from cerebral ganglia in Pheretima is
 1. 2 pairs  2. 2
 3. 8 to 10  4. 8 to 10 pairs
16. In Pheretima, double ventral nerve cord is absent in the segments
 1. 4th to last 2. 1st,2nd  and 4th
 3. 1st,2nd and 3rd  4. 3rd and 4th
17. Lens of photoreceptor in Pheretima is
 1. Phaeosome 2. Episome
 3. Mesosome 4. Endosome
18. Double ventral nerve cord in Pheretima arises from
 1. Supra oesophageal ganglia
 2. Sub pharyngeal ganglia
 3. Supra pharyngeal ganglia
 4. Sub oesophageal ganglia
19. Cerebral ganglia in Pheretima are present in the segment
 1. 2nd 2. 3rd 3. 4th 4. 5th
20. Prostomium of Pheretima receives nerves from
 1. Supra oesophageal ganglia
 2. Sub pharyngeal ganglia
 3. Supra pharyngeal ganglia
 4. Sub oesophageal ganglia
21. In Pheretim, segment with nerve ring as well as double ventral nerve cord is
 1. 4th segment 2. 3rd segment
 3. 5th segment 4. 2nd segment
22. In Pheretima epidermal receptors are abundant on
 1. Dorsal and ventral sides
 2. Lateral and dorsal sides
 3. Antero dorsal sides
 4. Ventro lateral sides
23. Afferent fibres of peripheral nerves in Pheretima connects
 1. Receptor to effector organs
 2. Ventral nerve cord to effector organs
 3. Receptor to ventral nerve cord
 4. Ventral nerve cord to receptor
24. Receptors with single cell in Pheretima are
 1. Photoreceptros
 2. Epidermal receptors
 3. Buccal receptors 4. Mechano receptors
25. Number of segmental ganglia in the pre-clitellar region of Pheretima is
 1. 10 pairs 2. 9 pairs
 3. 13 pairs 4. 12 pairs
26. Epidermal receptors in Pheretima acts as
 1. Chemoreceptors 2. Auditory receptors
 3. Gustatory receptors
 4. Olfactory receptors
27. Number of segments in Pheretima with only one type of nephridia is
 1. 8 2. 14 3. 9 4. 15
28. Part of septal nephridium that joins with the septal excretory canal is
 1. Proximal limb of the twisted loop
 2. Short straight lobe
 3. Distal limb of the twisted loop
 4. Terminal nephridial duct
29. V-shaped nephridia in Pheretima  are
 1. Pharyngeal nephridia
 2. Typical nephridia 3. Septal nephridia
 4. Integumentary nephridia
30. Position of supra- intestinal excretory canals in Pheretima is
 1. Above the dorsal blood vessel
 2. Below the intestine 3. Above the intestine 4. Below the ventral blood vessel
31. Pharyngeal nephridia in Pheretima lie on either side of
 1. Buccal chamber and pharynx
 2. Pharynx and oesophagus
 3. Oesophagus and gizzard
 4. Pharynx and gizzard
32. Closed nephridia in Pheretima are
 1. Pharyngeal and integumentary nephridia
 2. Pharyngeal and septal nephridia
 3. Septal and integumentary nephridia
 4. Integumentary and typical nephridia
33. In Pheretima, nephridia absent in segments with blood glands are
 1. Pharyngeal nephridia
 2. Integumentary nephridia
 3. Septal nephridia 4. All
34. Number of septa in Pheretima that do not bear septal nephridia is
 1. 9 2. 10 3. 11 4. 14
35. In Pheretima, nephridia are absent in
 1. First 3 segments 2. Clitellar segments
 3. First 2 segments
 4. Post-clitellar segments
36. Closed and exonephric nephridia are
 1. Pharyngeal nephridia
 2. Typical nephridia
 3. Septal nephridia
 4. Integumentary nephridia
37. In Pheretima, pair of ducts from the pharyngeal nephridia of the sixth segment open into
 1. Pharynx  2. Buccal chamber
 3. Oesophagus 4. Gizzard
38. In Pheretima, nephridia eliminate excretory wastes both from the blood and the coelomic fluid are
 1. Pharyngeal nephridia
 2. Typical nephridia
 3. Septal nephridia
 4. Integumentary nephridia
39. Enteronephric nephridial system of Pheretima is an adaptation for
 1. Conservation of urea
 2. Conservation of water
 3. Elimination of water
 4. Elimination of faeces
40. Enteronephric nephridia in Pheretima are
 1. Pharyngeal and integumentary nephridia
 2. Pharyngeal and septal nephridia
 3. Septal and integumentary nephridia
 4. Integumentary and typical nephridia
41. Based on excretory product Pheretima is described as
 1. Hypotonicand uricotelic
 2. Hypertonic and uricotelic
 3. Hypertonic and uriotelic
 4. Hypotonic and uriotelic
42. Forest of nephridia in Pheretima is
 1. Typhlosolar region 2. Clitellar region
 3. Pre-clitellar region 4. Post-clitellar region
43. Chlorogogen cells are derived from
 1. Outer coelomic epithelium
 2. Epidermis
 3. Inner coelomic epithelium
 4. Endodermis
44. Pharyngeal nephridia in Pheretima opens into
 1. Buccal chamber and pharynx
 2. Pharynx and oesophagus
 3. Oesophagus and gizzard
 4. Pharynx and gizzard
45. Tufted nephridia in Pheretima are
 1. Pharyngeal nephridia
 2. Typical nephridia
 3. Septal nephridia
 4. Integumentary nephridia
46. Terminal nephridial duct of sepal nephridia is the continuation of
 1. Proximal limb of the twisted loop
 2. Nephrostome
 3. Distal limb of the twisted loop
 4.Neck
47. Total number of pharyngeal nephridia in Pheretima is
 1. 3 pairs  2. 200 to 250
 3. 80 to 100 4. Many
48. Septal excretory canals in Pheretima directly opens
 1. Into intestine 2. To out side
 3. Into supra intestinal excretory canal
 4. Into coelom
49. Number of septal excretory canals in each segment is
 1. Many 2. 2 pairs 3. 2 4. 1
50. In Pheretima, the nitrogenous wastes from the blood supplied to the intestinal wall are collectd by
 1. Septal nephridia 2. Chlorogogen cells
 3. Pharyngeal nephridia
 4. Eleocytes
51. In Pheretima, first septum to which septal nephridia are attached lies between the segments
 1. 4/5 2. 14/15 3. 15/16 4. 5/6
52. Number of pre clitellar segments in Pheretima with micro nephridia and without pharyngeal nephridia
 1. 8 2.10 3. 11 4. 13
53. Open and enteronephric nephridia
 1. Pharyngeal nephridia
 2. Typical nephridia 3. Septal nephridia
 4. Integumentary nephridia
54. Detached chlorogogen cells loaded with excretory wastes are called
 1. Phagocytes 2. Mucocytes
 3. Eleocytes 4. Amoebocytes
55. Nephridia absent in Pheretima are
 1. Pharyngeal nephridia
 2. Typical nephridia 3. Septal nephridia
 4. Integumentary nephridia
56. Closed and enteronephric nephridia in Pheretima are
 1. Pharyngeal nephridia
 2. Typical nephridia 3. Septal nephridia
 4. Integumentary nephridia
57. In Phertima phagocytised eleocytes are sent out through
 1. Pharyngeal nephridia
 2. Typical nephridia 3. Septal nephridia
 4. Integumentary nephridia
58. In Pheretima pharyngeal nephridia present on either side of oesophagus but opens into pharynx are present in the segment   

 1. 4 2. 5 3. 6 4. 7

59. In Pheretima pharyngeal nephridia present on either side of oesophagus but opens into pharynx are present in the segment   

 1. 4 2. 5 3. 6 4. 7
60. Number of common nephridial ducts that open into pharynx of Pheretima is
 1. 1 pair 2 .4 pairs 3. 3 pairs 4. 2 pairs
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PHYLUM PLATY HELMINTHES

PLANARIAN

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Watch your thoughts; they become words. 
Watch your words; they become actions.   
Watch your actions; they become habits.    
Watch your habits; they become character 
Watch your character;it becomes your destiny.   
                                                                       —Lao-Tze

AVES ASSIGNMENT :

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1. Birds are called glorified reptiles by
  1. Young  2. Huxley  3. Andreas Wagner  4. Hyman
2. Type of vertebrae and skull in birds are respectively
  1. heterocoelous & monocondylic  2. heterocoelous & dicondylic
  3. procoelous & monocondylic  4.procoelous& dicondylic
3. Hind limbs of birds are not useful in
  1. bearing the weight & capturing the food 2. capturing the food & swimming in water
  3. swimming in water & perching on land  4. flying in air & reducing the body weight
4. Structures absent in kiwi are
 1. wings and remiges  2. rectrises and olfactory sense
 3. remiges and olfactory sense  4. rectrises and pecten
5. A: Urinary bladder is absent in birds
 R: Birds are uricotelic.
 1. Both A & R are correct, R is the correct explanation to A
 2. Both A & R are correct, R is not the correct explanation to A
 3. A is true, R is the false  4. R is true, A is the false
6. Incorrect statement about feathers
 1. arrangement is called pterylation    2. these are the only exoskeletal structures in birds
 3. pterylae are irregular in ratitae but regular in carinatae 4. feathery tracts are called pterylae but feather less tracts are called apteria
7. Birds are described as ‘masters of air’ by
 1. Young  2. Huxley  3. Lamarck  4. Linnaeus
8. Arrange the following structures in quill feather on one above the other
 a.barbs  b. barbicels c. rachis  d. barbules
 1. c-a-b-d 2. c-a-d-b 3. c-d-a-b 4. a-c-d-b
9. Vertebrae in birds never participate in the formation of synsacrum are
 1. cervical  2. thorasic  3. lumbar  4. sacral
10. Penguins belong to the super order
 1. Archaeornithes 2 .Neornithes  3. Impennae 4. Ratitae
11. Flightless bird with preen gland but with poorly developed olfactory sense is
 1. Kiwi  2. Tinamus 3. Rhea  4. Struthio
12. Birds are evolved during the period
 1. Triassic  2. Jurassic 3. Cretaceous 4. Carboniferous
13. Incorrect in the following
 1. wooly feathers – down feathers 2. feathers provide excellent insulation – down feathers
 3. tuft of small feathers - after shaft  4. sparcely distributed feathers – quill feathers
14. Structures which help to maintain the shape of the eye in birds are
 1. pecten 2. nictitating membrane    3. sclerotic plates  4. eye lids
15. Match the following and choose the correct combination
     Bird  Distribution
 A. Casuarius 1. Mexican terrestrial
 B. Tinamus 2. Australia, New Guinea
 C. Emu 3. Plains of South America
 D. Rhea 4. Arid regions of Africa and
  Arabia
 E. Struthio 5. Sandy plain or open
  forests of Australia
  1. A-2, B-1, C-5, D-4, E-3  2. A-2, B-1, C-3, D-4, E-5
 3. A-2, B-1, C-5, D-3, E-4  4. A-1, B-2, C-3, D-4, E-5
16. Read the following about birds and choose the correct combination
 I. larynx is at the anterior end and syrinx is at the posterior end of trachea
 II. two pairs of abominal air sacs are present
 III. lungs are spongy with nine air sacs
 1. all are true   2. all except II are true 3. all, except I are true   4. all except III are true
17. Incorrect statement about quill feathers is
 1. Its expanded portion is vane or vexillum 2. Hollow proximal part of the axis is called calamus or quill
 3. Superior umbilicus is between quill and rachis 4. After shaft is near the inferior umbilicus
18. Find the mismatch
 1. jackans penguin – Spheniscus 2. blue jay – Coracious bengalensis
 3. humming bird – Archiochus  4. alpine swift – Eudynamus
19. Find the mismatch
 1. jackans penguin – Spheniscus  2. blue jay – Coracious bengalensis
 3. humming bird – Archiochus  4. alpine swift – Eudynamus
20.    Following are the statements about birds:
A) Female birds are with a pair of functional ovaries. 
B) Cleavage is meroblastic   C)  Eggs are megalecithal 
1) A and B are true  2) B and C are true  3) A and C are true  4) A, B and C are true
21.    Smallest living flightless bird with a keen sense of smell is
1) Dromaeus  2) Casuarius  3) Apteryx  4) Tinamus
22.   Flightless bird with oil gland is
1) Emu  2) Cassowary  3) Tinamou  4) American ostrich
23.  Which of the following character is not seen in birds?
1) Four chambered heart      2) Sinus venosus is absent
3) Truncus arteriosus is absent  4) Developed renal portal system
24.   Feathers known to cover the newly hatched birds and provide insulation are
1) Quill feathers  2) Counter feathers  3) Down feathers  4) Filopumes
 25.  Birds became modernised in the period
1) Carboniferous period  2) Jurassic period  3) Triassic period  4) Cretaceous period

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SNAKE GIVING BIRTH

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CHILD BIRTH

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HELODERMA HORRIDUM

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BLOOD COAGULATION

BASICS AND PHERETIMA - ASSIGNMENT

ASSIGNMENT

1. Wrong statement about the members of a species
  1. Sharing common gene pool and same ecological niche
  2. Showing similarity in the karyotype
  3. Interbreeding freely and producing for the offspring
  4. Having dissimilar structure and functional characteristics
2. Author of “Systema Naturae’ is
   1. Linnaeus 2. Mayr          3. John Ray        4. Dobzhansky
3. The dynamic nature of species became popularized after the publication of
   1. Linnaeus Systema Naturae   2. Darwin’s Origin of species
   3. Lyell’s Principles of Geology  4. Mathus On the principles of population
4. Members of a species show
   1. preferential mating     2. Random mating   3. Non-assrtative mating 4. out crossing
5. “Species” means
   1. Appearance  2 .Arrangement   3.Kind    4. Both 1 and 3
6. Protostomes without body cavity are
   1. Annelids  2. Nematodes 3. Echinoderms 4. Platyhelminths
7. Five-kingdom classification of all living organisms was proposed by
   1.Whittaker  2. Lamarck          3. Bateson  4. Herbert spencer
8. A: Species is dynamic
  R: No new species are formed in course of time
 1) Both A & R are true and R explains A   2) Both A & R are true & R does not explains A
 3) A is true, R is false       4) A is false, R is true
9. Statement (S): Species are group of potentially inter-breeding natural populations that are isolated from other such groups
 Reason (R): Reproductive isolation brings about distinctive morphological characters
   1)Both (S) and (R) are true & (R) is correct explanation to (S)  2) Only (S) is true, (R) is not true
   3) Both (S) and (R) are not true     4) Both (S)&(R) are true & R does not explains (S)
10. (A) : Lateral hearts in 12th and 13th segments of  Pheretima are called latero oesophageal hearts
 (R) : They connect dorsal blood vessel and latero oesophageal blood vessel to ventral blood vessel
   1) Both A & R are true and R explains A     2) Both A & R are true & R does not explains A
   3) A is true, R is false       4) A is false, R is true
11. (A) : Blood in dorsointestinal blood vessels contains more nutrients in Pheretima
  (R) : In the intestinal region of Pheretima each segment contains two pairs of dorsontestinal blood vessels
   1) Both A & R are true and R explains A      2) Both A & R are true & R does not explains A
   3) A is true, R is false       4) A is false, R is true
12. Arrange the following parts in ascending order based on total number
 A. Anterior loops     B. Commissurals    C. Ventro-intestinals    D. Dorso-intestinals     E. Ring vessels
   1. A-E-C-B-D    2. A-E-C-D-B 3. A-E-B-C-D      4. E-A-B-D-C
13. Shortest longitudinal blood vessel in Pheretima is
   1. Supra oesophageal blood vessel  2. Latero oesophageal blood vessel
   3. Ventral blood vessel   4. Dorsal blood vessel
14. In Pheretima, supra oesophageal blood vessel lies on the dorsal side of the
   1. Oesophagus 2. Stomach   3. Intestine 4. Pharynx
15. Paired longitudinal blood vessels in Pheretima are
   1. Supra oesophageal blood vessels 2. Latero oesophageal blood vessels
   3. Ventral blood vessels 4. Dorsal blood vessels
16. In Pheretima, lateral hearts connect
 1.Ventral blood vessel to dorsal blood vessel 2. Ventral blood vessel to supra oesophageal blood vessel
 3. Dorsal blood vessel to ventral blood vessel
 4. Latro oesophageal blood vessel to supra oesophageal blood vessel
17. In Pheretima, blood flow is from posterior to anterior end in
   1. Dorsal blood vessel  2. Ventral blood vessel
   3. Sub neural blood vessel 4. Supra oesophageal blood vessel
18. In Pheretima, number of dorso intestinal blood vessels in each segment is
   1. 1 pair  2. One    3. 2 pairs  4. 3 pairs
19. Blood vessels act as collecting as well as distributing vessels in Pheretima are
   1. Latero oesophageal blood vessels 2. Commissural blood vessels
   3. Supra oesophageal blood vessels  4. Sub neural blood vesels
20. Number of valves in each lateral oesophageal heart of Pheretima is
   1. 3 pairs  2. 4 pairs  3. 8 pairs  4. 2 pairs

DRACO

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MONITOR LIZARD

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VARANUS MONITOR - INDIAN MONITOR LIZARD

DIGESTIVE SYSTEM OF PHERETIMA - IMP QUESTION FOR IPE

1. Describe the digestive system in Pheretima with the help of  a diagram?
(March 2005, May 2007, March 2010 , MARCH 2011)
Ans : The digestive system consists of the alimentary canal and the associated digestive
       glands. The  alimentary canal consists of  the following parts.
1) MOUTH* It is a crescentic aperture  present at the anterior end,  ventrally on the first segment  called Peristomium
* The extension of the first segment over hangs like a lip infront of the mouth, called prostomium.
2) BUCCAL CHAMBER
* The  mouth leads into Buccal chamber.
* The Buccal chamber extends from the first to the middle of the third segments
* The walls of the Buccal chamber turn inside out and the Pharynx ( everts ) comes out through the mouth
   and helps in digging the soil.
3) PHARYNX* Buccal chamber leads into Pharynx.
* It occurs in the third and fourth segments.
* Its wall is muscular and contains several blood cells.
* Its Dorsal side is folded and consists of a glandular structure called Pharyngeal bulb, thelateral wall is
  pushed inwards to form a pair of lateral folds called shelves.
* They divide the pharyngeal cavity into 2 compartments, called the dorsal salivary chamber and the ventral
   conducting chamber.
* The chromophilic cells of Pharyngeal bulb secrete proteolytic enzymes and mucus that help in protein   digestion.
* The ventral conducting chamber helps in passing the food.
4) OESOPHAGUS* The Pharynx opens into the oesophagus.
* The oesophagus is a narrow tube extending from the 5th
   to 8th segments.
5) GIZZARD* Oesophagus in 8th segment opens into the gizzzard .
* It is an oval shaped hard muscular chamber .
* It has thick wall of circular muscles and inner lining of chitinous cuticle.
* It grinds the food material into fine particles.
* It is commonly called “ grinding mill “.3
6) STOMACH* The gizzard leads into the stomach.
* The stomach extends from the 9th to the 14th segment.
* It is a highly vascular and glandular tube.
* Its inner foldings contain gland cells, which secrete proteolytic enzymes, that  help in protein dig estion.
7) INTESTINE :* Stomach opens into the long and wide intestine which extends from the 15th
 to the last segment.
* It’s mid dorsal fold is called typhlosole. This is poorly developed in Pheretima.
* It increases the area of absorption of food.
* On the basis of the presence of typhlosole the intestine is divisible into 3 regions.
1) Pre-typhlosolar region 2) Typhlosolar region 3) Post-typhlosolar region
1) Pre-typhlosolar region :* This is the proximal part of the intestine located from 15th to 25th segments.
* In the 26th segment, a pair of conical outgrowths, the intestinal caecae arise form this region laterally
   and extend forward over three or four segments.
* They secrete digestive juices, which contain amylase enzyme.
* Typhlosole  is absent in this part of intestine.
2) Typhlosolar region :* It starts from 26th segment and terminates  in 23 or 25 segments ahead of the hind end of the body.
* It is distinguished by the presence of small mid dorsal projection, the typhlosole, hanging into the
   lumen of the intestine. Typhlosole is poorly developed in Pheretima.
* Digested food is absorbed in this region.
3) Post-typhlosolar region :* It is the distal part of the intestine and it occupies the last 23 or  25 segments.
* It is without a typhlosole.
* It is also called rectum.
* The undigested food is converted into small pellets.
8) ANUS : It is present in the last segment. The undigested food is sent out through the anus in the form of
     pellets. These pellets are called “worm castings”.

VENOM APPARATUS

REPTILIA

CLASS REPTILIA

Name: From "reptilis" meaning "creeping".

Chief characteristics: Two characteristics of the skull which can be used to distinguish reptiles from amphibians are:

1. The reptile skull is high and narrow, compared with the low, broad amphibian skull.
2. In reptiles, the roof of the mouth is arched, with small openings. In amphibians, it is flat with large openings.

Mode of life: Complete colonization of land was achieved by the reptiles, which can lay their eggs on dry land.

Geologic range: Pennsylvanian to Recent.

The oldest reptile fossils, genus Hylonomus, (300 m.y. old) are found in Nova Scotia inside fossilized hollow trees filled with sediment. These reptiles were about 24 cm (about 1 ft) long. They resemble modern insect-eating lizards.

Diadectes sp., from the Early Permian (280-250 m.y.)                   

was a land-dwelling plant eater. The skeletal anatomy is reptilian,    but the skull resembles that of Seymouria, an amphibian.

Dicynodon, a Late Permian (250-230 m.y.), plant-eating reptile. From Cape Province, South Africa.
Photo courtesy of Pamela Gore.

Various groups of vertebrates can be distinguished on the basis of the position and number of openings behind the eye on the side of their skulls.

1. Anapsida (no holes) - amphibians, the earliest known reptile (Hylonomus), and turtles
2. Diapsida (two holes) - dinosaurs, flying reptiles, birds, and all groups of living reptiles except turtles
3. Euryapsida (upper hole only) - extinct marine reptiles
4. Synapsida (lower hole only) - pelycosaurs, therapsids, and mammals

Diagram showing the evolution of reptiles and synapsids.Diagram showing four vertebrate skull types.

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The Synapsids

CLASS SYNAPSIDA

The synapsids had diverged from the reptiles by the Late Carboniferous. The synapsids were long considered to be a subclass of reptile, but more recent cladistic analysis shows that they diverged from ancestors completely different than Hylonomus and other true reptiles.

The synapsids were the dominant terrestrial vertebrate in the Permian.

This group was formerly called the "mammal-like reptiles", however the name has been abandoned because they are not really reptiles.

Synapsids include the pelycosaurs and the therapsids.

Pelycosaurs

Several species of pelycosaurs had fins or "sails" on their backs, supported by rod-like extensions of their vertebrae. These sails may have been used as temperature regulating mechanisms.

Two well known pelycosaurs, which evolved their sails independently were the carnivorous Dimetrodon, and the plant-eating Edaphosaurus. The Permian pelycosaur, Edaphosaurus.
Dimetrodon has a larger skull and teeth than does Edaphosaurus, suggesting that Dimetrodon was a meat eater. Pelycosaurs lived in the Carboniferous and Permian. The sail-backed forms are characteristic of the Permian.

Therapsids

Therapsids were small to moderate-sized animals with several mammalian skeletal characteristics, such as:

• Fewer bones in the skull than the other reptiles
• Mammal-like structure of the jaw
• Differentiated teeth (incisors, canines, and cheek teeth)
• Limbs in more direct alignment beneath the body
• Reduction of ribs in the neck and lumbar regions, allowing greater flexibility
• Double ball-and-socket joint between the skull and neck
• Bony palate which permitted breathing while chewing (an important characteristic for animals evolving toward mammalian warm-bloodedness.) Efficient breathing provides oxygen needed to derive heat energy from food
• Whisker pits on the snout

Mammal-like features are well developed in the therapsid, Cynognathus. (From "kynos" meaning "dog" and "gnathos" meaning "jaw" or "tooth.")
Examination of the bone on the snout portion of the skull reveals probable "whisker pits", suggesting that they had hair, which may have functioned to insulate the animal and slow the rate of heat loss.

Cynognathus crateronotus, a therapsid from the Early Triassic (230-225 m.y.), Cape Province, South Africa.
Note the differentiated teeth. This animal was obviously a predator.

TYPES OF REPTILIAN SKULLS

POLYMERASE CHAIN REACTION

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