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Topic: Ichthyostega

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	Devonian Times - Ichthyostega stensioei
		Ichthyostega was now considered to be a primarily aquatic tetrapod, although one that may have hauled itself onto the shore.
		Ichthyostega is still distinguished by broadly flanged and overlapping ribs but these are fewer in number and more restricted longitudinally than in Jarvik's reconstruction.
		Ichthyostega was a relatively large (1.5 m or 4 ft) early tetrapod with a stout body.
	www.devoniantimes.org /Order/re-ichthyostega.html (1249 words)

	Ichthyostega - Picture - MSN Encarta
		Ichthyostega was an amphibian that lived in the late Devonian period, about 370 million years ago.
		Ichthyostega represents the transition from fishlike amphibians to land-based reptiles.
		Although it thrived in water, Ichthyostega also could survive on land.
	encarta.msn.com /media_461551476/Ichthyostega.html (37 words)

	Pharyngula::Ichthyostega
		Ichthyostega is special in that it is an early tetrapod that is clearly adapted to walk terrestrially.
		Coupled with differences in the dentition (recurved sectorial teeth in Ichthyostega, conical piercing teeth in Acanthostega) and body size (Ichthyostega is about 30% larger than Acanthostega), plus the fact that the two genera rarely occur together in the same locality within the Greenland sediments, this points to a clear ecological separation between these primitive tetrapods.
		Ahlberg PE, Clack JA, Blom H (2005) The axial skeleton of the Devonian tetrapod Ichthyostega.
	pharyngula.org /index/weblog/comments/ichthyostega (748 words)

	Coming Onto the Land - - science news articles online technology magazine articles Coming Onto the Land (Site not responding. Last check: 2007-10-19)
		Ichthyostega most resembled a group of lobe-finned fish that first appeared 410 million years ago and that includes today’s lungfish.
		Ichthyostega was a product of this evolution, and it was followed by amphibians increasingly comfortable on dry land.
		Ichthyostega had a small fin on the top of its tail that was essentially a relic of its fishy pedigree.
	www.discover.com /issues/jun-95/features/comingontothelan523 (5510 words)

	Fall'96Syllabus
		Ichthyostega (also from the Late Devonian of Greenland), retains a fish-like caudal fin, but exhibits morphology that is better adapted for terrestrial walking as compared to Acanthostega.
		The ribs of Ichthyostega are long, thick, and supportive, but their overlapping nature would have limited the range of lateral motion considerably.
		It does not appear that any of the first terrestrial vertebrates were specialists for utilizing plants or insects as a potential food source, for they retain the relatively large body size and needle-like teeth of the sarcopterygians, indicating a diet of fish (which are difficult to catch, but can generally be swallowed whole).
	ijolite.geology.uiuc.edu /00FallClass/geo143/lect/lect12.html (1075 words)

	Ichthyostega
		Ichthyostega comes from the Upper Devonian (Famennian) of East Greenland and is widely featured in the literature as the first ‘four-legged fish’.
		Ichthyostega shows a mixture of plesiomorphic and apomorphic characters which make it difficult to place phylogenetically, though it is clearly a basal stem-tetrapod (Ahlberg and Clack 1998, Clack 2002a, Ruta et al.
		Ichthyostega and Acanthostega specimens are not, as a rule, found in quite the same horizons, but the precise temporal and ecological separation between them has yet to be worked out.
	tolweb.org /tree?group=Ichthyostega&contgroup=Terrestrial_vertebrates (1770 words)

	tech (Site not responding. Last check: 2007-10-19)
		Ichthyostega and acanthostega seem to be an ancient variety of amphibians, with the perceived “fish-like affinities” being overemphasized (salamanders and other amphibians share many transitory aquatic features during their lifetime, with no more evidence to prove their hypothetical fish ancestry.
		In the case of ichthyostega and acanthostega, they hypothetically had to have received their new land-adapted appendages, fingers and all, with all of the appropriate systems to manipulate and utilize them to the utmost, so as to “survive as the fittest”.
		I might add that the fossil remnants of Ichthyostega and Acanthostega are rather fragmentary themselves, missing certain aspects of the skeletal structure, and missing the ever-so-vital soft tissue and muscle remnants (acanthostega limb is extremely fragmented.
	www.calarts.edu /~shockley/tech.html (4050 words)

	Wildlife -- giant ground sloth
		Ichthyostega must have spent much tome in the water because it had lateral line canal system along its head- a sensory mechanism that fish still use to detect vibrations in water.
		Its eyes were high in the head, like those of crocodiles as well as other animals that lurk in muddy water.
		At the back of its head, Ichthyostega had a pair of notches that held opening for tubes to the throat.
	wind.prohosting.com /ferphoto/wildlife/sloth.html (543 words)

	J17 Did labyrinthodonts evolve from lung fish or crossopterygians?
		The fishy heritage of the Ichthyostega is their broad flat, coelacanth-like head and teeth, their fish-like spine, and a small fin on the top of their tail.
		Not fish-like are their four limbs that terminate in digits (toes, fingers).To support locomotion out-of-water, their forelimbs were attached to sturdy shoulders and they had sturdy rib cages that held up their internal organs.
		Ichthyostega were primarily aquatic and movement over land would have been awkward (seal-like, according to Coates).
	geowords.com /histbooknetscape/j17.htm (1110 words)

	Evolution: Library: Fish with Fingers
		Many of the most telling fossils have been dug up in Greenland in the latter part of the 20th century, particularly in the past 15 years.
		This creature had stumpy legs and a long tail, which were probably used for propulsion in water.
		In fact, Acanthostega, more so than Ichthyostega, was basically an inhabitant of the water; its limbs were too floppy and its backbone too weak to support itself on land.
	www.pbs.org /wgbh/evolution/library/03/4/l_034_03.html (496 words)

	Acanthostega
		Ichthyostega was an ancient extinct amphibian with four legs and a fish-like tail fin.
		There are many skeletal similarities between the fossils of these two animals, which strongly suggests that they have evolved from the same ancestoral forms.
		Different from Acanthostega, Ichthyostega had pelvic bones that connected the linbs to the spinal column (backbone), and the spinal column was able to support the body weight on land.
	www.sonic.net /~evolve/creation/acanthostega.htm (622 words)

	LiveScience.com - First Four-Legged Animals Inched Along
		Ichthyostega’s complete skeleton was first described by Erik Jarvik in 1955, but many aspects of its anatomy remained unknown, making it difficult to determine how it moved on land.
		Ichthyostega could move around on land, it probably spent plenty of time in the water.
		This drawing depicts the 1 meter long Ichthyostega as it probably moved on land and in water.
	www.livescience.com /animalworld/050831_four_legs.html (555 words)

	Palaeos Vertebrates 150.200 Tetrapoda: Ichthyostega
		Jarvik (1996) is the only monograph on Ichthyostega, a very important early tetrapod; and it was written by a scientist whom we have frequently praised for his work on Eusthenopteron and other osteolepiform fishes.
		Blom bluntly states that "the braincase and the vertebral column, still remain to be explored." [B05] Jarvik's reconstruction of the pectoral girdle exaggerates the post-branchial lamina and includes a large supraglenoid process which appears to be an artifact [LCo95].
		Although Jarvik attacked the axial skeleton of Ichthyostega with dispatch, he delayed his paper on limb girdles (recall that the pectoral girdle is part of the skull in fishes) until 1980, when Stensio was finally phasing out of active Museum work.
	www.palaeos.com /Vertebrates/Units/150Tetrapoda/150.200.html (2047 words)

	Devonian Times - Recent Findings
		Until the 1980s, the fossil record of early tetrapods was essentially limited to Ichthyostega, a Late Devonian tetrapod from eastern Greenland.
		Since it was essentially contemporaneous with the apparently more terrestrial Ichthyostega, Acanthostega, like modern-day dolphins and whales, may have secondarily lost the skeletal features needed for life on land.
		Ichthyostega forelimbs were more robust than those of Acanthostega and were probably able to lift the front half of the body.
	www.devoniantimes.org /Order/new-order.html (989 words)

	Transitions: The Evolution of Life :: September :: 2005
		While regionalization of the backbone is fairly common in living land vertebrates, it’s not seen in the lobe-finned fishes from which Ichthyostega is thought to have evolved.
		As such, the researchers hypothesize that Ichthyostega probably used two different gaits on land, depending on how fast it needed to move.
		In the other, inchworm-like gait Ichthyostega likely used the limited up-and-down movement of the backbone in combination with symmetrical limb movement “to achieve a weird gait approximating to a slow and extremely stumpy-legged gallop,” Ahlberg said.
	afarensis.blogsome.com /2005/09 (502 words)

	(Talk.Origins) There are gaps between fish-amphibian - CreationWiki
		Ichthyostega was a largely aquatic amphibian that was capable of walking on land.
		However, they are dated as roughly contemporary with Acanthostega and Ichthyostega, thus eliminating Tulerpeton as transitional between Acanthostega and Ichthyostega, and Carboniferous amphibians.
		So of these "good transitional fossils," one is dated as tens of millions of years too old; one is not considered ancestral to amphibians; one is known only from a humerus; three are dated as contemporary with each other with no transitions indicated between them or fish.
	creationwiki.org /There_are_gaps_between_fish-amphibian (1056 words)

	TRANITIONAL FORMS: Fish to Amphibians
		Ichthyostega had external nasal openings and a choana like that of the Panderichthys (Schultze, 1990, p.
		Because of this, walking on a rocky surface, which requires the ability to curl the paws around various obstacles, would have been difficult for the early tetrapods.
		Because of this, this creature is transitional between the later amphibians and Acanthostega and Ichthyostega discussed above (Carroll, 2002, p.
	home.entouch.net /dmd/transit.htm (1530 words)

	The axial skeleton of the Devonian tetrapod Ichthyostega : Nature
		The axial skeleton of the Devonian tetrapod Ichthyostega
		Ichthyostega was the first Devonian tetrapod to be subject to a whole-body reconstruction
		Ichthyostega is the earliest vertebrate to show obvious adaptations for non-swimming locomotion.
	www.nature.com /nature/journal/v437/n7055/abs/nature03893.html (272 words)

	The fossil record of ‘early’ tetrapods: evidence of a major evolutionary transition?
		Ichthyostega is about one metre long with a broad, flat head, short, barrel-shaped body, stocky legs, large pelvic and pectoral girdles, and a rib cage with broad, overlapping ribs (Figure 1).
		As recently as 1988, a major vertebrate palaeontology text described Ichthyostega as a fairly typical land animal with the usual complement of five digits on the hind limb.
		Jarvik, E., The Devonian tetrapod Ichthyostega, Fossils and Strata 40:1–213, 1996.
	www.answersingenesis.org /tj/v17/i2/tetrapod.asp (5007 words)

	Ichthyostega (Site not responding. Last check: 2007-10-19)
		One of the main objectives of the 1998 expedition was to collect material that would try to answer some of these questions.
		Initial results have shown that Ichthyostega had a highly specialised ear region, probably adapted for hearing in water, and quite unlike that of any other tetrapod or fish (see Clack et al 2003 in Nature).
		We have also shown that separate species of Ichthyostega are distinguishable in the two formations in which the genus has been found: a narrower skulled form in the lower Aina Dal Formation, and a broader skulled form in the upper Britta Dal Formation.
	theclacks.org.uk /jac/ichthyostega.htm (516 words)

	Acanthostega gunnari
		Ribs were short in contrast to the overlapping ribs of Ichthyostega (Clack and Coates 1995; Coates 1996).
		In the shoulder girdle of Acanthostega, the cleithrum and scapulocoracoid were co-ossified, as in Ichthyostega and Hynerpeton.
		It also retains a number of primitive features independent of its aquatic life, such as the notochordal braincase, form of the fenestra vestibulae, persistent embryonic braincase fissures, fish-like occiput, anocleithrum, form of the scapulocoracoid-cleithral complex, relative lengths of radius and ulna, retention of dermal fin rays and supraneural spines.
	tolweb.org /tree?group=Acanthostega (2041 words)

	Science News Online (5/22/99): Out of the Swamps
		The size of a desk, it had arms, legs, hands, and feet, apparently for walking on land, but it also had a fishlike tail that could have served the animal only in the water.
		Their studies of this creature suggested that the development of limbs coincided with the time that vertebrates first started crawling out on land, which made a certain amount of sense.
		They found that Ichthyostega had seven toes on each foot rather than the five that the Swedish researchers had assumed.
	www.sciencenews.org /sn_arc99/5_22_99/bob1.htm (2412 words)

	Late Devonian Carboniferous amphibians Xenacanthus eusthenopteron Ichthyostega acanthostega crassigyrnius eogryrinius
		Late Devonian Carboniferous amphibians Xenacanthus eusthenopteron Ichthyostega acanthostega crassigyrnius eogryrinius
		The spread of land based plants especially trees made fresh water environments attractive to early vertebrates.
		Ichthyostega is from the Late Devonian Greenland, andhas the shoulders and ribs of a land animal.
	www.dinosaurcollector.150m.com /carboniferous.html (455 words)

	Palaeos Vertebrates: 150 Tetrapod References
		Blom, H (2005), Taxonomic revision of the Late Devonian tetrapod Ichthyostega from East Greenland.
		Acanthostega, Baphetes, Baphetidae, Ichthyostega, Loxomma, Megalocephalus, Spathicephalus, Tetrapoda, Tetrapoda.
		Clack, JA (2002a), The dermal skull roof of Acanthostega gunnari, an early tetrapod from the Late Devonian.
	www.palaeos.com /Vertebrates/Units/150Tetrapoda/150References.html (822 words)

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