III' Myxiniformes, Petromyzontiformes

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III. Myxiniformes, Petromyzontiformes Fossil
Relatives
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A. Outgroup forms amphioxus ( Branchiostoma)
and the origin of vertebrates
1. Was suspension feeding or raptorial feeding
primitive?
B. Earliest bony craniates from the Ordovician,
Silurian and Devonian
1. Relationships of hagfishes and lampreys to
these Paleozoic forms are uncertain 2.
Lampreys and hagfishes evolved from separate
Paleozoic ancestors 3. Lampreys are more closely
related to gnathostomes than are hagfishes 4. We
use a simplified phylogeny and classification
from Liem et al.
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C. Myxiniformes, Family Myxinidae - Hagfishes
1. Exclusively marine, some continental shelf,
others very deep water 2. six genera, 60
species Myxine, Eptatretus 3. Reproduction and
development still largely unknown 4. Adults lack
true teeth and jaws feed differently from other
craniates 5. Unusual kidneys and osmoregulation
primitive or derived? 6. Poor vision, generally
considered a derived reduction 7. Peculiar
brain, ear, cranial nerves and lateral line
system primitive or derived?
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External anatomy of an adult Atlantic Hagfish,
Myxine glutinosa.
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D. Arandaspida - Arandaspids
1. Examples include Sacambamaspis, the earliest
vertebrate known as whole-body fossils
E. Heterostraci - Heterostracans
1. Examples include Anglaspis, Pteraspis,
Drepanaspis 2. Abundant and ecologically
important Silurian through Devonian
F. Conodonti - Conodonts
1. An exclusively Paleozoic group of uncertain
affinities known mostly from tiny isolated
teeth 3. Whole-body fossils known for 20 years
definitely vertebrates based on gill arches and
segmented body muscles but peculiar
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G. Petromyzontiformes - Lampreys
1. Lampreys have an unusual larva, known as an
ammocoetes larva 2. Jamoytius as the sister
group of Family Petromyzontidae 3. Family
Petromyzontidae includes six Recent genera and 41
species Ichthyomyzon, Petromyzon, Caspiomyzon,
Lampetra, Geotria, Mordacia 4. Feeding and
parasitism by adult lampreys 5. Occurrence of
non-parasitic stocks and species of lampreys 6.
Lamprey migration in the Connecticut River
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External anatomy of an adult sea lamprey,
Petromyzon marinus. The generic name Petromyzon
means stone sucker - which is exactly what
adult male and female lampreys do when they build
their nests in shallow fresh water streams.
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The first Holyoke Dam was built in this rapids
(then termed a waterfall) in 1849 the current
dam was completed in 1900. It is the third one to
be built on this site.
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The Holyoke Pool is approximately 100 above sea
level.
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Lamprey run
USGS 01172003 CONNECTICUT RIVER BELOW POWER DAM
AT HOLYOKE, MA Latitude 4212'36", Longitude
7235'44" NAD27, Hampden County, Massachusetts,
Hydrologic Unit 01080201 DRAINAGE AREA 8,309
square miles STATION TYPE Surface Water
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Power station at Holyoke Dam showing towers for
the two fishlifts, the viewing platform, and the
Robert E. Barrett Fishway. One lift serves the
base of the dam and the other serves the power
canal.
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Power canal for discharge from the two turbines.
View along crest of dam showing fishway.
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Head of power canal showing entrance to its
fishlift and viewing platform.
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A
B
Lift from the base of the dam ascending (A and B)
and emptying (C) fish into the Fishway. The fish
are lifted about 50 feet. The flume of the
Fishway is about 300 feet long. It has both a
public viewing window and a counting window for
recording the numbers and species of fishes
passing through the flume.
C
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Lamprey swimming upstream in the public window of
the Robert E. Barrett Fishway
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Connecticut River at New Island, circa 0.5 mi
below mouth of Fort River.
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Mouth of Fort River, the only tributary of the
Holyoke Pool that is not dammed.
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A view of the Fort River in Amherst where
lampreys spawn in June. By the time the lampreys
spawn, the water is relatively clear and shallow
(circa 1 foot deep).
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H. Anaspida - Anaspids
1. examples include Pharyngolepis,
Rhyncholepis 2. A synapomorphy that groups
them with lampreys is the orientation of the
gill openings in a slanted line
I. Thelodonti - Thelodonts
1. examples include Phlebolepis 2. An important
derived feature of this group is micromeric
scales more like those of Recent fishes than
typical for Paleozoic groups
J. Galeaspida - Galeaspids
1. Have an unusual hole in the head in other
respects similar to next group, the
osteostracans
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K. Osteostraci (Cephalaspidiformes of some
authors)
1. examples include Hemicyclaspis,
Cephalaspis, Tremataspis, Ateleaspis 2.
well-known and familiar fossils 3. Heterocercal
tail 4. Paired pectoral fins 5. Two dorsal fins
in forms such as Ateleaspis 6. Generally
regarded as the sister group of gnathostomes