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Table 3 Presence of structures/characteristics of the pinniped skin

From: Skin histology and its role in heat dissipation in three pinniped species

Characteristics Harbor seal Northern elephant seal California sea lion
1. Thin epidermis +, head +, head +, head
2. Epidermis keratinization + + +
3. Epidermal scale-like ridges + + +
4. Thick epidermis - + + (vent. abd, tx, flippers)
5. Smooth muscle in dermis + + +
6. Dermal veins w/t valves + + +
7. Primary hair follicles +, all the body +, all the body +, flippers bare ventrally
8. Dermal elastic fibers + + +
9. Dermal collagen +++ +++ +++
10. Wool hair (secondary hair follicles) + (head, vent. & dors. abd, vent., lat tx, glut., tail, flipper, neck, head) - + (tx, vent & dors. abd, neck, glut, head)
11. Arrector pili - - -
12. Sebaceous glands + + +
13. Sweat glands + (not prominent) + (not prominent) + (prominent)
14. Brown adipose tissue - - -
15. Hypodermal vessels + + +
16. Hypodermal adipose tissue. +++ +++ +++
  1. Sign + indicates presence. Sign indicates absence. Sign +++ indicates a major presence. Vent. = ventral, dors. = dorsal, abd. = abdomen, tx. =thorax, glut. = gluteal.