Anyone who has touched a shark would say they feel smooth going in one direction and rough going the other. Why you might ask? WELL, it’s because elasmobranchs have dermal denticles, a type of placoid scale that no other fish have. #SharkWeek 1/ 
Their shape and size varies across species! Even crazier, they are modified teeth and are covered in enamel. 2/
Their main function is to protect the shark but they have other functions as well!
Dermal denticles decrease drag and are the reason sharks can move so smoothly through the water! There are a few papers showing that dermal denticles move to different angles from their resting place to benefit the shark further. This is termed “bristling”. 3/
Dermal denticles feel different as well in terms of roughness. Nurse sharks feel very sandpapery whereas tiger sharks and hammerheads feel a lot sharper when moving your hand from from tail to head. 4/
Fun fact: I got my first shark burn from restraining a tiger shark tail. This one specifically: 4/
Fun fact #2: The second shark burn I recieved was from tagging this beautiful hammerhead: 5/
Some of my favorite dermal denticle shapes are those of are: hammerheads, tiger sharks, whale sharks, and mako shark! (Photo from Shark Skin Boundary Layer Control by Lang et al., 2012) 6/
I could talk about dermal denticles all day but I’ll end here 😂 I hope you enjoyed the read. Thanks for coming to my mini-Ted Talk 🦈
This is from erinmdillon.wordpress.com/2015/08/18/der…
This is from: Diversity of dermal denticle structure in sharks: Skin surface roughness and three‐dimensional morphology Madeleine V. Ankhelyi Dylan K. Wainwright George V. Lauder 2018
This is from Lang, Amy & Motta, Philip & Habegger, M.Laura & Hueter, Robert. (2012). Shark Skin Boundary Layer Control. 10.1007/978-1-4614-3997-4_9.
This paper is dope and everyone should read it!!!!
I ALSO LOVE THIS PAPER YOU SHOULD READ IT
In conclusion, I LOVE DERMAL DENTICLES!!!!!
