1. Early Vertebrates PART I VERTEBRATE ZOOLOGY (VZ Lecture04 – Spring 2012 Althoff - reference PJH Chapter 3)

2. PALEOZOIC (late Carboniferous Period) Terrestrial nonamniote tetrapods open water shallow lake margin upland early amniote 1 2 3 4 5 Fig. 7-5 p165 PJH

3. The most conspicuous new features of early vertebrates vs. nonvertebrate chordates:  A ______________ end that…. A) contained a tripartite brain that was B) enclosed by a cartilaginous cranium C) containing sense organs  Newly acquired pharyngeal musculature to draw water into the mouth and over the gills _________________ …not for filter feeding (i.e, acquiring food).

4. Early vertebrates Fossil deposits, ~540 MYA A) Myllokumingia (see next slide), China B) Haikouichthys China, too—same deposits Small, fish-shaped, ~ 3 cm long _____________ present BUT _____ evidence of bone or mineralized scales Dorsal fin and ribbonlike pairs of ventrolateral fins

5. Fig. 3-1 p44 PJH Myllokumingia Astrapis MYOMERES DORSAL FIN VENTROLATERAL FIN

6. Next….bone fragments in fossil Fossil deposits: Australia, Bolivia, North America A) Astraspis (North America “version”) Large, fish-shaped, ~ 12 - 35 cm long Armored – close-fitting, polygonal bony plates Eye “protection” Torpedo-shaped Jawless

7. Fig. 3-1 p44 PJH Myllokumingia Astrapis BONY PLATES/SCALES EYE PROTECTION

8. Conodonts – “microfossils” _____________ elements of true vertebrates < 1mm long Composed of apartite = __________________ compound characteristic of vertebrate tissue Much like _____________ (making it uniquely vertebrate tissue) Complete impressions of conodont animals with the “conodont” elements arranged within the pharynx thus confirming they were true vertebrates

9. Fig. 3-2 p45 PJH Clydagnathus Idiognathus CONODONTS ________ elements (anterior) _________ Elements (posterior)

11. Fig. 3-3 p46 PJH

12. Origin of Bone & Mineralized Tissue Origin of mineralized tissues still somewhat uncertain Earliest known types are _______________ in structure than mineralized tissues of living vertebrates ____________  basic units of mineralized tissue…tooth-like elements formed “____” the skin (in dermal layer…unlike mollusks), then overlaid by epidermis No cells in adult form….acellular

13. __________________ of Mineralized Tissue? Defensive structures against predator attacks Design of bony tissue resulted in more complex function that merely protection: system of pores and small projections suggest ____________________ Protective against predators & insulating coating around ______________________ that increased detection of prey or Subsequent advantage: ______________ & _______________ deposition and subsequent mobilization

14. Which happened first? Vertebrates evolved first in freshwater or first in marine ecosystems? --some early thinking was that because of vertebrate kidney clearly being an advantage in freshwater, that most early evolution took place there --now, thinking is that _________ was “fortuitously preadapted” for fresh- water exist….that withstanding, “early” evolution likely was in _______ ecosystems.

15. Evidence of marine origin Earliest vertebrate __________ found in marine sediments (paleontological evidence) All nonvertebrate chordates and deuterostome invertebrates ( starfish, sea urchins, etc.) are exclusive marine forms (comparative physiological evidence) where ____________ in same concentrations as seawater

16. Extant (“ still living ”) Jawless Fishes Two representatives: _________ & __________ No specialized reproductive ducts…eggs and sperm released into coelum Primitive handling of drainage from kidneys (no duct-work, more through pores) External fertilization of eggs Considered ________________ a subset of “Agnathans” = jawless fishes preceeding conodonts and ostracoderms—both of which are extinct groups.

17. Fig. 3-4 p48 PJH

18. Hagfishes Family: Myxinoidea Two major genera: Eptatretus and Myxine ~ 40 species ~ 0.5 m in length, elongated ________ scales ________ vertebrae Simple kidneys Eyes degenerate, covered with thick skin Tooth-like plates Found nearly worldwide (except polar regions) Primarily deep-sea, cold-water inhabitants

20. Hagfishes _________________ ….slime glands produce gelatinous mess that is a deterrent to predators. After threat gone, makes a knot to scrap off mass of mucus, then sneezes sharply to blow nasal passage clear. ______________  find food by sense of ______ Also, use the “tying the knot” routine to brace themselves against their prey, mouth attaches to part of prey to tear off the flesh with pinching grasp….enough to expose soft coelomic cavity of prey. Digestion accomplished in a mucoid bag secreted by gut…nutrients diffuse out, then absorbed

21. Fig. 3-5 p49 PJH

22. Lampreys Family: Petromyzontoidea Two major genera: Petromyzon and Lampetra ~ 40 species ______ scales, up to 1 m in length ___ vertebrae, but “vertebral structures” (arculalia) that are ________________ skeletal elements Kidneys – much _____________ over hagfishes, enables better regulation of ions, water, and nitrogeneous waste… Exist in ___________ of salinities Found mostly in northern latitudes - temperate Most are _________________  live in sea/lake, breed in rivers or streams

23. Lampreys __________  on other fishes (usually bony fishes, but sometimes mammals = whales & porpoises) Attach to host by suction Oral gland secretes anticoagulant that prevents host’s blood from clotting Thus, bulk of lamprey’s diet is ___________ of the hosts _______, straight digestive tract…_______ “food”, _______ “digestion” Like many parasites, they don’t end up killing the host…only weaken them

24. Also see…. Fig. 4-5 p30 FS LAMPREY oral region Tooth-like organs (origin: ectoderm)

25. Lampreys Females produce hundreds to thousands of eggs, spawn with males after constructing a nest. Fertilized eggs get “surrounded” by larger rocks that create an eddy, dropping sediment over the eggs Adults die after breeding once Larvae hatch in about 2 weeks….known as Ammocoets, they float downstream, burrow in mud or sand and spend about the next ____ years as ______________________. Finally, metamorphosis into juvenile and become parasitic

26. Lampreys: Conservation Concern May have been indigenous to Lake Ontario….but not in any other Great Lakes until _________ Devasting to sport and commercial fish populations in the Great Lakes—especially Lake Erie by the 1940s. Huge efforts in past 50-60 years to curb their numbers: chemical lampricides electrical barriers mechanical weirs

28. Lake trout Sea lamprey