21. It is found in elasmobranchs ( sharks, rays, and skates ), seabirds, and some reptiles. 22. Leonard Compagno doubted the taxonomic validity of this species in his 1999 " Checklist of Living Elasmobranchs ". 23. The earliest elasmobranch fossils came from the Devonian and many surviving orders date back to the Cretaceous, or even earlier. 24. All elasmobranchs have a rectal gland which functions in the excretion of excess salts accumulated as a consequence of living in seawater. 25. After a doctoral thesis on host, and was one of the first to propose schemes of coevolution between monogeneans and elasmobranchs . 26. While elasmobranchs are the definitive hosts, other organisms may be infected in earlier stages of the life cycle of these cestodes. 27. In teleost fish, the pseudobranchs are mostly without respiratory function, and in elasmobranchs they are the gill arch of the spiracle. 28. These species avoid competition by diet and habitat differences; the scoophead feeds on small elasmobranchs , octopus, squid, and flounders. 29. Dr . "'Samuel H . Gruber "'is a shark biologist and founder of the American Elasmobranch Society. 30. In sharks and other extant elasmobranchs the upper jaw is not fused to the cranium, and the lower jaw is articulated with the upper.
