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Week 2

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Article Evaluation: Gnathostomata

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Everything in the article is relevant to the topic, and nothing which threw me off or that was distracting to the subject at hand. The article overall seems neutral, although on the talk page there was some disagreement on some facts stated, so it makes me wonder if that meant people were publishing what they themselves thought was correct information and ignoring what others thought was correct. The evolution of the jaw in vertebrates is well represented, but there wasn't really any explanation of why the evolution of the jaw occurred and it's mechanisms, and someone in the talk page also pointed this out...so that right there is definitely a big chunk of information missing on that subject. All citations I checked worked and supported the information stated except for one, by Sea World, in which the article no longer exists. Only two of the four articles I read into were peer reviewed, but the other two articles from newspapers claimed to have gotten information from other peer reviewed articles in scientific journals. None of the articles I read seemed biased. So two of the articles were definitely reliable, but one would have to go and look at the news article sources themselves to see if the news articles could be reliable. There is also information which is out of date pointed out on the talk page, where someone stated that placoderms came after acanthodians, and then whoever wrote the wrong information replied agreeing that he was in fact wrong. I didn't see any editing history to the article about it, however. I definitely feel like there is plagiarism on the page, in the sense that not enough information is cited in the article itself. There are too many long and complex sentences with tons of information with no citation number. I also feel like there isn't much going on in the talk page of the article. I was expecting many more comments, but there's only two replies total to comments made. There's not much conversation going on, and it's mainly just people suggesting things that could be added to the article. The article is rated at a level 4, so it is still under construction and needs to be refined.


This page is about the jawed vertebrates. For the echinoderm superorder, see Gnathostomata (echinoid). For jaw worms, see Gnathostomulid.
Jawed vertebrates
Temporal range: Middle Ordovician – present, 462–0 Ma
The placoderm Dunkleosteus,
an early jawed vertebrate
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Olfactores
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Subgroups

Week 3

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Adding to article: Gnathostomata

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I added a citation to the third sentence in the first paragraph because it was never cited in the first place as to where they got the information from. I also edited the sentence in the second paragraph from " that in males had been modified to claspers and basal plates in females, a pattern not seen in any other vertebrate group" to "that had been modified to claspers in males and basal plates in females--a pattern not seen in any other vertebrate group" because I thought the previous sentence was slightly confusing. I also added a sentence a sentence in the second paragraph about the gnathostomes ancestor recently being discovered to have pectoral and dorsal fins.

Gnathostomata /ˌneɪθoʊstoʊˈmɑːtə/ are the jawed vertebrates. The term derives from Greek: γνάθος (gnathos) "jaw" + στόμα (stoma) "mouth". Gnathostome diversity comprises roughly 60,000 species, which accounts for 99% of all living vertebrates. In addition to opposing jaws, living gnathostomes have teeth, paired appendages[1], and a horizontal semicircular canal of the inner ear, along with physiological and cellular anatomical characters such as the myelin sheathes of neurons. Another is an adaptive immune system that uses V(D)J recombination to create antigen recognition sites, rather than using genetic recombination in the variable lymphocyte receptor gene.[2]

It is now assumed that Gnathostomata evolved from ancestors that already possessed a pair of both pectoral and pelvic fins.[3] These ancestors, known as antiarchs, were previously thought to not possess pectoral or pelvic fins until recently.[2] In addition to this, some placoderms were shown to have a third pair of paired appendages,that had been modified to claspers in males and basal plates in females--a pattern not seen in any other vertebrate group.[4]

The Osteostraci are generally considered the sister taxon of Gnathostomata.[1][5][6]

It is believed that the jaws evolved from anterior gill support arches that had acquired a new role, being modified to pump water over the gills by opening and closing the mouth more effectively – the buccal pump mechanism. The mouth could then grow bigger and wider, making it possible to capture larger prey. This close and open mechanism would, with time, become stronger and tougher, being transformed into real jaws.

Newer research suggests that a branch of Placoderms was most likely the ancestor of present-day gnathostomes. A 419-million-year-old fossil of a placoderm named Entelognathus had a bony skeleton and anatomical details associated with cartilaginous and bony fish, demonstrating that the absence of a bony skeleton in Chondrichthyes is a derived trait.[7] The fossil findings of primitive bony fishes such as Guiyu oneiros and Psarolepis, which lived contemporaneously with Entelognathus and had pelvic girdles more in common with placoderms than with other bony fish, show that it was a relative rather than a direct ancestor of the extant gnathostomes.[8] It also indicates that spiny sharks and Chondrichthyes represent a single sister group to the bony fishes.[9] Fossils findings of juvenile placoderms, which had true teeth that grew on the surface of the jawbone and had no roots, making it impossible to replace or regrow as they broke or wore down as they grew older, proves the common ancestor of all gnathostomes had teeth and place the origin of teeth along with, or soon after, the evolution of jaws.[10][11]

Late Ordovician-aged microfossils of what have been identified as scales of either acanthodians[12] or "shark-like fishes",[13] may mark Gnathostomata's first appearance in the fossil record. Undeniably unambiguous gnathostome fossils, mostly of primitive acanthodians, begin appearing by the early Silurian, and become abundant by the start of the Devonian.

Classification

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The group is traditionally a superclass, broken into three top-level groupings: Chondrichthyes, or the cartilaginous fish; Placodermi, an extinct clade of armored fish; and Teleostomi, which includes the familiar classes of bony fish, birds, mammals, reptiles, and amphibians. Some classification systems have used the term Amphirhina. It is a sister group of the jawless craniates Agnatha.


  1. ^ a b Zaccone, Giacomo; Dabrowski, Konrad; Hedrick, Michael S. (5 August 2015). Phylogeny, Anatomy and Physiology of Ancient Fishes. CRC Press. p. 2. ISBN 978-1-4987-0756-5. Retrieved 14 September 2016.
  2. ^ a b Cooper MD, Alder MN (February 2006). "The evolution of adaptive immune systems". Cell. 124 (4): 815–22. doi:10.1016/j.cell.2006.02.001. PMID 16497590.
  3. ^ New study showing pelvic girdles arose before the origin of movable jaws
  4. ^ The first vertebrate sexual organs evolved as an extra pair of legs
  5. ^ Keating, Joseph N.; Sansom, Robert S.; Purnell, Mark A. (2012). "A new osteostracan fauna from the Devonian of the Welsh Borderlands and observations on the taxonomy and growth of Osteostraci" (PDF). Journal of Vertebrate Paleontology. 32 (5): 1002–1017. doi:10.1080/02724634.2012.693555. ISSN 0272-4634.
  6. ^ Sansom, R. S.; Randle, E.; Donoghue, P. C. J. (2014). "Discriminating signal from noise in the fossil record of early vertebrates reveals cryptic evolutionary history". Proceedings of the Royal Society B: Biological Sciences. 282 (1800): 20142245. doi:10.1098/rspb.2014.2245. ISSN 0962-8452. PMC 4298210. PMID 25520359.
  7. ^ Scientists make jaw dropping discovery
  8. ^ Zhu, Min; Yu, Xiaobo; Choo, Brian; Qu, Qingming; Jia, Liantao; Zhao, Wenjin; Qiao, Tuo; Lu, Jing (2012). "Fossil Fishes from China Provide First Evidence of Dermal Pelvic Girdles in Osteichthyans". PLOS ONE. 7 (4): e35103. Bibcode:2012PLoSO...735103Z. doi:10.1371/journal.pone.0035103. PMC 3318012. PMID 22509388.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  9. ^ Min Zhu; et al. (10 October 2013). "A Silurian placoderm with osteichthyan-like marginal jaw bones". Nature. 502 (7470): 188–193. Bibcode:2013Natur.502..188Z. doi:10.1038/nature12617. PMID 24067611.
  10. ^ Choi, Charles Q. (17 October 2012). "Evolution's Bite: Ancient Armored Fish Was Toothy, Too". Live Science.
  11. ^ ScienceShot: Ancient Jaws Had Real Teeth
  12. ^ Hanke, Gavin F.; Mark V. H. Wilson (2004). "New teleostome fishes and acanthodian systematics." (PDF). Recent advances in the origin and early radiation of vertebrates. pp. 189–216. ... record of acanthodian fishes is limited to microremains from the latest Ordovician (JANVIER 1996)
  13. ^ Sansom, Ivan J.; Moya M. Smith; M. Paul Smith (February 15, 1996). "Scales of thelodont and shark-like fishes from the Ordovician of Colorado". Nature. 379 (6566): 628–630. Bibcode:1996Natur.379..628S. doi:10.1038/379628a0.

Week 5

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Group project on articles Columbidae and Bird Anatomy

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I am editing the Bird anatomy page by adding edits to the circulatory system of birds, including:

  • birds have a heart generally larger than mammals in comparison with body size. Smaller birds also tend to have bigger hearts in reference to body size compared to bigger birds, due to the fact that smaller birds have higher metabolic rates
  • birds have an overall more efficient heart than mammals, beating slower as well and pumping more blood with each beat due to the large ventricles with more muscle fibers, allowing it to fill and empty more completely than most mammalian hearts. They also have thin muscle fibers in the heart with many mitochondria and a high amount of vascularization, allowing for diffusion of oxygen to be more efficient since the oxygen can diffuse over a shorter distance thanks to the thin muscle fibers.
  • the avian cardiac system responds very quickly to changes in level of activity by changes in heart rate, cardiac output, and by vasodilation and vasoconstriciton if the blood vessels

Section on avian circulatory system:

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Birds have a four-chambered heart,[1] in common with mammals, and some reptiles (mainly the crocodilia). This adaptation allows for an efficient nutrient and oxygen transport throughout the body, providing birds with energy to fly and maintain high levels of activity. A ruby-throated hummingbird's heart beats up to 1200 times per minute (about 20 beats per second).[2]


O'Malley, Bairbre. “Clinical Anatomy and Physiology of Avian Species--From Bird Brains to Pigeon Toes - WSAVA2008 - VIN.” Powered By VIN, 2008, www.vin.com/apputil/content/defaultadv1.aspx?id=3866642&pid=11268&.


Seymour, Roger S. “Cardiovascular Physiology of Dinosaurs.” Physiology, vol. 31, no. 6, 6 Oct. 2016, pp. 430–441., doi:10.1152/physiol.00016.2016.


“Bird Physiology.” Basic Biology, 15 Dec. 2015, basicbiology.net/animal/birds/physiology.


  1. ^ Citation needed
  2. ^ June Osborne (1998). The Ruby-Throated Hummingbird. University of Texas Press. p. 14. ISBN 978-0-292-76047-9.
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