Natural History of Sharks, Skates, and Rays Phylogeny of Holocephali MARE 394 Dr. Turner Summer 2008

Chimaeroid Fishes Exclusively marine – inhabit all oceans except Arctic & Antarctic Deep water dwelling – 500+m Live on or near bottom Local migrations for breeding Males, females, juveniles form distinct groups

Chimaeroid Ecology Prey on benthic inverts & small fishes Tooth plates used to crush crustaceans, mollusks, & echinoderms – some soft-bodied prey Sharks major predators Mature at 3-4 yrs

Chimaeroid Toothology Holocephalans characterized by ever-growing, nonreplacable hypermineralized tooth plates 6 tooth plates in 3 pairs; 1 lower – 2 upper Mandibular (lower) and vomerine (anterior upper) form beaklike bite Tooth plates typically only fossil remains

Subclass Holocephali Distinguished from other chondrichthyan fishes by morphological features: Mode of fusion of lower jaw to cranium Possession of non-replaceable, hypermineralized tooth plates

Extant Holocephali 33 described species Several new but undescribed; total probably < 45 species All belong to Order Chimaeriformes 3 Families

Order Chimaeriformes Family Callorhichidae 1 Genus, 3 species Family Rhinochimaeridae 3 Genus, 8 species Family Chimaeridae 2 Genus, 22 species

Family Callorhichidae Prominent, plow-shaped snout, torpedo-like body, heterocercal tail, large anal fin Enclosed lateral line canals underneath the skin Plow-nose Chimaeras or elephantfish Most primitive living Chimaera

Family Rhinochimaeridae Long, tapering fleshy snout extending anterior to the head Long-nose chimerians or spookfish Large bodies, elongate spearlike snout, narrow tail with elongate filament Inhabit deep waters; 1000-2000m

Family Chimaeridae Conical fleshy snout bluntly pointed at tip Short-nose chimerians or ratfish Lateral line canals on the snout expanded with wide dilations Compressed, elongate bodies tapering to whip-like tail

Chimaeroid Morphology Slender fishes 60cm – robust fishes >1m Skin scaleless in adults; embedded denticles in small juveniles Single gill opening; adults lack a spiracle 2 dorsal fins, caudal, paired pect & pelvic

Chimaeroid Dimorphism Sexual dimorphism; males possess 2° sexual characteristics: -front tenaculum, paired preprelvic tenacula, and paired pelvic claspers Front tenaculum – small club-like structure on head anterior to eyes unique to chimaeras; used to grasp pectoral fin of ♀ during copulation

Chimaeroid Dimorphism

Chimaeroid Reproduction Embryonic development only described in 2 species Internal fertilization; ♂ transfer sperm via pelvic claspers All chimaroids are oviparous; 2 egg capsules simultaneously – one from each oviduct; several pairs per season

Chimaeroid Egg Capsules