1. Natural History of Sharks, Skates, and Rays
Phylogeny of Holocephali
MARE 394
Dr. Turner
Summer 2009

2. 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

3. 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

4. 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

5. 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

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

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

8. 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

9. 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; m

10. 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

11. 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

12. 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

13. Chimaeroid Dimorphism

14. 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

15. Chimaeroid Egg Capsules