Living fossils

@article{doi1023071437499,
    author = "Myers, George S. and Berg, L. S.",
    title = "Classification of Fishes, Both Recent and Fossil",
    year = "1941",
    journal = "Copeia",
    url = "https://doi.org/10.2307/1437499",
    doi = "10.2307/1437499",
    openalex = "W2017085139"
}

The muscle of Latimeria chalumnae contains 30 to 71 percent (dry weight) of lipid deposited extracellularly. Wax esters constituted 90 percent or more of the lipids from muscle and fat storage tissues. These esters, by gaschromatographic analysis, consisted of C 30 to C 40 homologs with one or two double bonds.

@article{nevenzel1966lipids,
    author = "Nevenzel, Judd C. and Rodegker, Waldtraut and Mead, James F. and Gordon, Malcolm S.",
    title = "Lipids of the Living Coelacanth, Latimeria chalumnae",
    year = "1966",
    journal = "Science",
    abstract = "The muscle of Latimeria chalumnae contains 30 to 71 percent (dry weight) of lipid deposited extracellularly. Wax esters constituted 90 percent or more of the lipids from muscle and fat storage tissues. These esters, by gaschromatographic analysis, consisted of C 30 to C 40 homologs with one or two double bonds.",
    url = "https://doi.org/10.1126/science.152.3730.1753",
    doi = "10.1126/science.152.3730.1753",
    number = "3730",
    openalex = "W2084286228",
    pages = "1753-1755",
    volume = "152",
    references = "doi101007bf02635576, doi101021bi00884a019, doi101038143455a0, doi101038143748a0, doi101038175362a0, doi101126science1503697771, openalexw2980079574"
}

Samples of blood (hemolyzed) were obtained from the renal vein, the hepatic portal vein, and the heart of a freshly thawed specimen of Latimeria chalumnae. The coelacanth uses high concentrations of urea to maintain its serum osmolality at approximately that of sea water. The mean value for the total osmolality was 1181 milliosmoles per liter. The mean values (milliequivalents per liter) were: for sodium, 181; for potassium, 51.3; for calcium, 6.9; for magnesium, 28.7; for chloride, 199; and for bicarbonate, 4.7. The mean urea concentration was 355 millimoles per liter, and the mean nonprotein nitrogen was 1343 milligrams percent. Heart blood showed significantly lower values for osmolality (921 milliosmoles per liter) and nonprotein nitrogen (1030 mg percent) and was probably less severely contaminated with products of protein breakdown. Fluid from the anterior chamber of the eye showed values of 952 milliosmole/liter; the urea value for this fluid was 303 mmole/liter, and the magnesium was 7.3 meq/liter. The magnesium value for the aqueous humor was used to correct the abnormally high concentrations in the hemolyzed serum. The high level of serum potassium also was attributed to hemolysis.

@article{doi101126science1553762568,
    author = "Pickford, Grace E. and Grant, F. Blake",
    title = "Serum Osmolality in the Coelacanth, Latimeria chalumnae: Urea Retention and Ion Regulation",
    year = "1967",
    journal = "Science",
    abstract = "Samples of blood (hemolyzed) were obtained from the renal vein, the hepatic portal vein, and the heart of a freshly thawed specimen of Latimeria chalumnae. The coelacanth uses high concentrations of urea to maintain its serum osmolality at approximately that of sea water. The mean value for the total osmolality was 1181 milliosmoles per liter. The mean values (milliequivalents per liter) were: for sodium, 181; for potassium, 51.3; for calcium, 6.9; for magnesium, 28.7; for chloride, 199; and for bicarbonate, 4.7. The mean urea concentration was 355 millimoles per liter, and the mean nonprotein nitrogen was 1343 milligrams percent. Heart blood showed significantly lower values for osmolality (921 milliosmoles per liter) and nonprotein nitrogen (1030 mg percent) and was probably less severely contaminated with products of protein breakdown. Fluid from the anterior chamber of the eye showed values of 952 milliosmole/liter; the urea value for this fluid was 303 mmole/liter, and the magnesium was 7.3 meq/liter. The magnesium value for the aqueous humor was used to correct the abnormally high concentrations in the hemolyzed serum. The high level of serum potassium also was attributed to hemolysis.",
    url = "https://doi.org/10.1126/science.155.3762.568",
    doi = "10.1126/science.155.3762.568",
    openalex = "W2070396971",
    references = "doi1010160010406x67907268, doi101016s0021925818767999, doi101016s0021925818838248, doi101071zo9560001, doi101126science132341836, doi101152ajplegacy19551831155, doi101210endo694778, doi101242jeb313424, doi101242jeb383659, doi101242jeb391167, doi101242jeb423437"
}

@article{chavin1972thyroid,
    author = "CHAVIN, WALTER",
    title = "Thyroid of the Coelacanth, Latimeria chalumnae Smith",
    year = "1972",
    journal = "Nature",
    url = "https://doi.org/10.1038/239340a0",
    doi = "10.1038/239340a0",
    number = "5371",
    openalex = "W2004529614",
    pages = "340-341",
    volume = "239",
    references = "doi101016b9781483167046500240, doi101038237175a0"
}

@article{hughes1972gills,
    author = "Hughes, G. M.",
    title = "Gills of a living coelacanth,Latimeria chalumnae",
    year = "1972",
    journal = "Experientia",
    url = "https://doi.org/10.1007/bf01965307",
    doi = "10.1007/bf01965307",
    number = "11",
    openalex = "W2044491623",
    pages = "1301-1302",
    volume = "28",
    references = "doi101007bf00335372, doi101007bf00335484, doi101007bf01946201, doi101016003456877290014x, doi1023071540335"
}

@article{cole1973intraocular,
    author = "Cole, D.F.",
    title = "Intraocular fluid composition in the coelacanth, Latimeria chalumnae",
    year = "1973",
    journal = "Experimental Eye Research",
    url = "https://doi.org/10.1016/0014-4835(73)90133-4",
    doi = "10.1016/0014-4835(73)90133-4",
    number = "5",
    openalex = "W1983914418",
    pages = "389-395",
    volume = "16",
    references = "doi1010160010406x70905931, doi1010160014483572900541, doi101021ac60134a012, doi101038237175a0, doi101126science132341836, doi101126science1553762568, doi101136jcp132156"
}

Inorganic and organic constituents were studied on blood serum collected from a living specimen of the coelacanth, Latimeria chalumnae. Inorganic electrolytes determined included sodium (196.7 mM/l), potassium (5.78 mM/l), magnesium (5.30 mM/l), calcium (4.94 mM/l), chloride (186.7 mM/l), bicarbonate (9.60 mM/l), phosphate (5.08 mM/l), and sulfate (4.80 mM/l). Serum urea (377 mM/l) and trimethylamine oxide (122 mM/l) were high as previously reported, and accounted for the bulk of the total non‐protein nitrogen (1199 mg%); total amino acids added a small but not insignificant fraction (21.9 mg%). High serum lactate (16.5 mM/l) and glucose (6.57 mM/l) levels were probably indicative of stress; glucose was the only carbohydrate present in appreciable amounts in the serum, although traces of glucuronic acid and rhamnose were found. Serum total cholesterol was 3.91 mM/l, organically bound phosphorus 1.99 mM/l and total proteins 2.84 g%. Three major protein fractions were evident from cellulose acetate electrophoresis and at least 11 peaks were demonstrable by acrylamide gel electrophoresis. Latimeria serum lacks a protein component with a mobility approaching that of human serum albumin. Serum osmolarity (932 mOsm/l) was somewhat lower than that of sea water collected at the site of capture of the specimen (1035 mOsm/l). Evolutionary implications of the similarity of Latimeria serum chemistry to that of other marine fishes are discussed.

@article{griffith1974serum,
    author = "Griffith, Robert W. and Umminger, Bruce L. and Grant, Blake F. and Pang, Peter K. T. and Pickford, Grace E.",
    title = "Serum composition of the coelacanth, Latimeria chalumnae Smith",
    year = "1974",
    journal = "Journal of Experimental Zoology",
    abstract = "Inorganic and organic constituents were studied on blood serum collected from a living specimen of the coelacanth, Latimeria chalumnae. Inorganic electrolytes determined included sodium (196.7 mM/l), potassium (5.78 mM/l), magnesium (5.30 mM/l), calcium (4.94 mM/l), chloride (186.7 mM/l), bicarbonate (9.60 mM/l), phosphate (5.08 mM/l), and sulfate (4.80 mM/l). Serum urea (377 mM/l) and trimethylamine oxide (122 mM/l) were high as previously reported, and accounted for the bulk of the total non‐protein nitrogen (1199 mg\%); total amino acids added a small but not insignificant fraction (21.9 mg\%). High serum lactate (16.5 mM/l) and glucose (6.57 mM/l) levels were probably indicative of stress; glucose was the only carbohydrate present in appreciable amounts in the serum, although traces of glucuronic acid and rhamnose were found. Serum total cholesterol was 3.91 mM/l, organically bound phosphorus 1.99 mM/l and total proteins 2.84 g\%. Three major protein fractions were evident from cellulose acetate electrophoresis and at least 11 peaks were demonstrable by acrylamide gel electrophoresis. Latimeria serum lacks a protein component with a mobility approaching that of human serum albumin. Serum osmolarity (932 mOsm/l) was somewhat lower than that of sea water collected at the site of capture of the specimen (1035 mOsm/l). Evolutionary implications of the similarity of Latimeria serum chemistry to that of other marine fishes are discussed.",
    url = "https://doi.org/10.1002/jez.1401870111",
    doi = "10.1002/jez.1401870111",
    number = "1",
    openalex = "W2007467582",
    pages = "87-102",
    volume = "187",
    references = "doi101001jama195102920260071031, doi101001jama196103040510042019, doi101001jama196403070130055036, doi1010079781468464658, doi101016s1546509808600825, doi101017s002531540004652x, doi101111j1469185x1936tb00497x, doi1023071441916, doi1024448ethz1890, doi107326000348196136071"
}

@article{griffith1974serum3,
    author = "Griffith, R. W. and Umminger, B. L. and Grant, B. F. and Pang, P. K. T. and Pickford, G. E",
    title = "Serum composition of the coelacanth Latimeria chalumnae Smith",
    year = "1974",
    journal = "Journal of Experimental Zoology, v. 187, p. 87-102",
    note = "talkorigins\_source = {true}; raw\_reference = {Griffith, R. W., Umminger, B. L., Grant, B. F., Pang, P. K. T., and Pickford, G. E., 1974, Serum composition of the coelacanth Latimeria chalumnae Smith: Journal of Experimental Zoology, v. 187, p. 87-102.}"
}

Fluid from the notochordal canal of the coelacanth, Latimeria chalumnae, was analyzed for major inorganic and organic constituents and compared with blood serum from the same fish. Significantly or suggestively lower levels of sodium, magnesium, calcium, bicarbonate, sulfate, total carbohydrates, glucose, lactate, cholesterol, bound phosphate and total proteins were found in notochordal fluid than in serum, whereas potassium, chloride, urea, trimethylamine oxide, and total free amino acids were higher and inorganic phosphorus essentially identical. Osmolarity of notochordal fluid (1058 mOsm) exceeds that of serum (942 mOsm). A whitish precipitate in the fluid consisted of a matrix of fibers 100 A in diameter and of indefinite length. It resembled a sialoglycoprotein in composition and was stabilized by disulfide bonds. The fluid contained cellular debris.

@article{doi101002jez1401920206,
    author = "Griffith, Robert W. and Mathews, Martin B. and Umminger, Bruce L. and Grant, Blake F. and Pang, Peter K.T. and Thomson, Keith Stewart and Pickford, Grace E.",
    title = "Composition of fluid from the notochordal canal of the coelacanth, Latimeria chalumnae",
    year = "1975",
    journal = "Journal of Experimental Zoology",
    abstract = "Fluid from the notochordal canal of the coelacanth, Latimeria chalumnae, was analyzed for major inorganic and organic constituents and compared with blood serum from the same fish. Significantly or suggestively lower levels of sodium, magnesium, calcium, bicarbonate, sulfate, total carbohydrates, glucose, lactate, cholesterol, bound phosphate and total proteins were found in notochordal fluid than in serum, whereas potassium, chloride, urea, trimethylamine oxide, and total free amino acids were higher and inorganic phosphorus essentially identical. Osmolarity of notochordal fluid (1058 mOsm) exceeds that of serum (942 mOsm). A whitish precipitate in the fluid consisted of a matrix of fibers 100 A in diameter and of indefinite length. It resembled a sialoglycoprotein in composition and was stabilized by disulfide bonds. The fluid contained cellular debris.",
    url = "https://doi.org/10.1002/jez.1401920206",
    doi = "10.1002/jez.1401920206",
    openalex = "W2038295841",
    references = "cole1973intraocular, doi101016s0021925818722801, doi101016s0021925818767999, doi101016s0021925818838248, doi101016s0021925818943334, doi101016s1546509808600825, doi101017s0025315400005750, doi101017s0025315400018105, doi101038237175a0, doi1010970000505319311100000026, doi101111j1469185x1969tb00823x, doi107326000348196136071"
}

1. Bile salts of the coelacanth Latimeria chalumnae Smith (five specimens) and of the three living genera of lungfish (Dipnoi) were examined as completely as possible and compared. 2. The small 'bile acid' fractions include no more than traces of well-known C27 or C24 acids (free or conjugated) and the functioning bile salts must be regarded as alcohol sulphates. 3. Comparison of the alcohols suggest that (a) Latimeria stands biochemically outside the animal group which includes the Dipnoi, (b) Protopterus and Lepidosiren are more closely related to one another than either is to Neoceratodus, (c) all four primitive osteiychtheans have some amphibian affinities, (d) there are affinities between Latimeria and Dipnoi and ostariophysan families (especially Cyprinidae and Catostomidae) and (e) there are biochemical links between Dipnoi and lampreys.

@article{doi101042bj1610201,
    author = "Amos, B. and Anderson, Ian G. and Haslewood, G. A. D. and Tökès, L",
    title = "Bile salts of the lungfishes Lepidosiren, Neoceratodus and Protopterus and those of the coelacanth Latimeria chalumnae Smith",
    year = "1977",
    journal = "Biochemical Journal",
    abstract = "1. Bile salts of the coelacanth Latimeria chalumnae Smith (five specimens) and of the three living genera of lungfish (Dipnoi) were examined as completely as possible and compared. 2. The small 'bile acid' fractions include no more than traces of well-known C27 or C24 acids (free or conjugated) and the functioning bile salts must be regarded as alcohol sulphates. 3. Comparison of the alcohols suggest that (a) Latimeria stands biochemically outside the animal group which includes the Dipnoi, (b) Protopterus and Lepidosiren are more closely related to one another than either is to Neoceratodus, (c) all four primitive osteiychtheans have some amphibian affinities, (d) there are affinities between Latimeria and Dipnoi and ostariophysan families (especially Cyprinidae and Catostomidae) and (e) there are biochemical links between Dipnoi and lampreys.",
    url = "https://doi.org/10.1042/bj1610201",
    doi = "10.1042/bj1610201",
    openalex = "W237906695"
}

@article{dingerkus1978the,
    author = "DINGERKUS, GUIDO and MOK, HIN KIU and LAGIOS, MICHAEL D.",
    title = "The living coelacanth Latimeria chalumnae does not have a cloaca",
    year = "1978",
    journal = "Nature",
    url = "https://doi.org/10.1038/276261b0",
    doi = "10.1038/276261b0",
    number = "5685",
    openalex = "W2063295958",
    pages = "261-262",
    volume = "276",
    references = "doi101126science19042191105, openalexw1964182146"
}

Abstract The coelacanth, Latimeria chalumnae, possesses a blood chemistry that is nearly identical to that of the elasmobranch fishes and contrasts with that of the bony fishes and tetrapods. Especially notable is the retention of high concentrations of urea (377 mM) and of trimethylamine oxide (122 mM), which aid in raising the blood osmolarity (942 mosm/I) to close to that of the sea water environment. These features also characterize other coelacanth body fluids, such as the notochordal fluid, aqueous and vitreous humours, ventricular fluid, coelomic fluid and bile. The tissues of Latimeria, such as muscle, are also characterized by high urea concentrations. The osmotic balance between extracellular fluids and tissues seems to be achieved by the presence of very high tissue levels of trimethylamine oxide (ca. 300 mmol/(kg H2O)), which counteract the low ion concentrations found in tissue. Renal function in Latimeria seems to involve the selective elimination of certain divalent ions (magnesium, phosphate and sulphate) and of organic substances (glucuronate, creatine and some amino acids). Unlike other ureosmotic fishes, the coelacanth does not possess the renal capacity to reabsorb urea. Evidence suggests that the rectal gland, structurally much like those of chondrichthyians, functions to excrete excess sodium chloride. Since the blood osmolarity of Latimeria is some­what lower than that of sea water (942 cf. 1026 mosm/l), it is in negative water balance. Some evidence suggests that this is overcome by drinking sea water in a manner similar to that of the teleosts. The problem of whether ureosmotic regulation is homologous in Latimeria and the chondrichthyians is moot, although we favour the possibility that it was independently acquired for the following reasons. (1) Renal urea reabsorbtion is absent in Latimeria although it is crucial to ureosmotic regulation in the chondrichthyians. (2) Internal fertilization and development are necessary concomitants of ureosmotic regulation in fishes and internal fertilization in the two groups is achieved by non-homologous mechanisms. (3) Ureosmotic regulation has been evolved independently in a third vertebrate group, the euryhaline amphibian Rana cancrivora.

@article{doi101098rspb19800054,
    author = "Griffith, Robert W.",
    title = "Chemistry of the body fluids of the coelacanth, Latimeria chalumnae",
    year = "1980",
    journal = "Proceedings of the Royal Society of London. Series B, Biological sciences",
    abstract = "Abstract The coelacanth, Latimeria chalumnae, possesses a blood chemistry that is nearly identical to that of the elasmobranch fishes and contrasts with that of the bony fishes and tetrapods. Especially notable is the retention of high concentrations of urea (377 mM) and of trimethylamine oxide (122 mM), which aid in raising the blood osmolarity (942 mosm/I) to close to that of the sea water environment. These features also characterize other coelacanth body fluids, such as the notochordal fluid, aqueous and vitreous humours, ventricular fluid, coelomic fluid and bile. The tissues of Latimeria, such as muscle, are also characterized by high urea concentrations. The osmotic balance between extracellular fluids and tissues seems to be achieved by the presence of very high tissue levels of trimethylamine oxide (ca. 300 mmol/(kg H2O)), which counteract the low ion concentrations found in tissue. Renal function in Latimeria seems to involve the selective elimination of certain divalent ions (magnesium, phosphate and sulphate) and of organic substances (glucuronate, creatine and some amino acids). Unlike other ureosmotic fishes, the coelacanth does not possess the renal capacity to reabsorb urea. Evidence suggests that the rectal gland, structurally much like those of chondrichthyians, functions to excrete excess sodium chloride. Since the blood osmolarity of Latimeria is some­what lower than that of sea water (942 cf. 1026 mosm/l), it is in negative water balance. Some evidence suggests that this is overcome by drinking sea water in a manner similar to that of the teleosts. The problem of whether ureosmotic regulation is homologous in Latimeria and the chondrichthyians is moot, although we favour the possibility that it was independently acquired for the following reasons. (1) Renal urea reabsorbtion is absent in Latimeria although it is crucial to ureosmotic regulation in the chondrichthyians. (2) Internal fertilization and development are necessary concomitants of ureosmotic regulation in fishes and internal fertilization in the two groups is achieved by non-homologous mechanisms. (3) Ureosmotic regulation has been evolved independently in a third vertebrate group, the euryhaline amphibian Rana cancrivora.",
    url = "https://doi.org/10.1098/rspb.1980.0054",
    doi = "10.1098/rspb.1980.0054",
    openalex = "W2010533513",
    references = "cole1973intraocular, doi101016s1546509808600825, doi101093icb172365, doi101111j1469185x1936tb00497x, doi101111j1469185x1967tb01528x, doi101126science1313401670, doi101152ajplegacy1930932480, doi101152ajplegacy19762304925, doi101242jeb383659, doi1023072412985, doi1024448ethz1890, hamoir1973muscle"
}

@incollection{doi101007978146138271318,
    author = "Forey, Peter L.",
    title = "The Coelacanth as a Living Fossil",
    year = "1984",
    booktitle = "Casebooks in earth sciences",
    url = "https://doi.org/10.1007/978-1-4613-8271-3\_18",
    doi = "10.1007/978-1-4613-8271-3\_18",
    openalex = "W2256482627",
    references = "doi101098rspb19800052"
}

@book{eldredge1984living1,
    author = "Eldredge, N. and Stanley, S. M",
    title = "Living Fossils",
    year = "1984",
    publisher = "New York, Springer- Verlag, 291 p",
    note = "talkorigins\_source = {true}; raw\_reference = {Eldredge, N., and Stanley, S. M., 1984, Living Fossils: New York, Springer- Verlag, 291 p.}"
}

@article{kihira1984bile,
    author = "Kihira, K and Akashi, Y and Kuroki, S and Yanagisawa, J and Nakayama, F and Hoshita, T",
    title = "Bile salts of the coelacanth, Latimeria chalumnae.",
    year = "1984",
    journal = "Journal of Lipid Research",
    url = "https://doi.org/10.1016/s0022-2275(20)34449-7",
    doi = "10.1016/s0022-2275(20)34449-7",
    number = "12",
    openalex = "W2188157399",
    pages = "1330-1336",
    volume = "25",
    references = "doi101016s0022227520378706, doi101016s0022227520379384, doi101016s0040403901927273, doi101042bj0930034, doi101042bj1410485, doi101042bj1610201, doi101093oxfordjournalsjbchema127499, doi101093oxfordjournalsjbchema127800, doi101093oxfordjournalsjbchema128399, doi101093oxfordjournalsjbchema128567"
}

SUMMARY I. The traditional view of the origin of tetrapod vertebrates is that they are descendants of fossil osteolepiform fish, of which Eusthenopteron is best known. In recent years both that conclusion and the methodology by which it has been reached have been challenged by practitioners of cladistic analysis. Particularly a recent review by Rosen et al. (1981) claims that Dipnoi (lungfish) are the sister‐group of the Tetrapoda, that Osteolepiformes is a non‐taxon and that Eusthenopteron is more distant from tetrapods than are Dipnoi, coelacanths and probably the fossil Porolepiformes. We attempt to refute all these concludions by use of the same cladistic technique. 2. We accept that all the above‐mentioned groups, together with some less well‐known taxa, can be united as Sarcopterygii by means of shared derived (apomorph) characters. We also agree that Porolepiformes and Actinistia (coelacanths) can be characterized as valid taxa. The primitive and enigmatic fossil fish Powichthys is accepted as representing the plesiomorph sister‐group of true porolepiforms. 3. Only two apomorph features, the course of the jaw adductor muscles and the position of incurrent and excurrent nostrils, appear to unite all the fish, living and fossil, currently regarded as Dipnoi. The characteristic tooth plates and the presence of petrodentine both exclude important primitive fossil forms. 4. Contrary to the opinion of Rosen et al., Osteolepiformes can be characterized — by the arrangement of bones forming the cheek plate, the presence of basal scutes to the fins and by the unjointed radials of the median fins. However, if these are true autapomorphies they exclude any osteolepiform from direct tetrapod ancestry. 5. Tetrapoda is a monophyletic group characterized by ten or more autapomorphies, including the bones of the cheek plate, a stapes and fenestra ovalis, and a series of characters of the appendicular skeleton. 6. Tetrapods have a true choana (internal nostril). We accept that the posterior (excurrent) nostril of Dipnoi is the homologue of the tetrapod choana. However, we assert that the posterior nostril of all bony fish is the homologue of the choana. This assertion would be refuted if any fish showed separate posterior nostril and choana. We reject the claim that this ‘three nostril condition’ occurred in porolepiforms and osteolepiforms. The evidence for a choana in porolepiforms is inadequate. Osteolepiforms had a true choana, characterized as in tetrapods by its relationship to the bones of the palate, but no third nostril. Dipnoans are not choanate. 7. Following cladistic practice, the relationship of the extant taxa is established first. Dipnoi are thus shown to be the living sister‐group of tetrapods, but only on ‘soft anatomy’ characters unavailable in fossils. Coelacanths are the living sister‐group of the taxon so formed. 8. The relationship of the fossil taxa to the extant sarcopterygians is then considered. The synapomorphy scheme proposed by Rosen et al. is discussed at length. Virtually all the characters they use to exclude close relationship of Eusthenopteron (and hence all osteolepiforms) to tetrapods, in favour of coelacanths and dipnoans, are invalid. 9. A series of synapomorphies uniting osteolepiforms and tetrapods is proposed, including a true choana (hence the taxon Choanata), the histology of the teeth, and a number of characters of the humerus. The recently discovered fossil Youngolepis, which lacks a choana, represents the sister‐group of the Choanata, and is not uniquely close to Powichthys. The latter, as a porolepiform (s.l.) is a member of the sister‐group to Choanata plus Youngolepis. 10. Our cladistic analysis suggests that all the extinct taxa considered are more closely related to tetrapods than are the Dipnoi. Moreover fossil evidence suggests that Dipnoi, considered as an extant taxon, may not even be the living sister‐group of Tetrapoda. Early fossil dipnoans appear to have been marine fish without specific adaptations for air breathing. If so the apparent synapomorphies of Dipnoi and Tetrapoda may be homoplastic — the insistence on grouping extant taxa first would then have yielded an invalid inference.

@article{doi101111j1469185x1987tb01635x,
    author = "Panchen, Alec L. and Smithson, Timothy R.",
    title = "CHARACTER DIAGNOSIS, FOSSILS AND THE ORIGIN OF TETRAPODS",
    year = "1987",
    journal = "Biological reviews/Biological reviews of the Cambridge Philosophical Society",
    abstract = "SUMMARY I. The traditional view of the origin of tetrapod vertebrates is that they are descendants of fossil osteolepiform fish, of which Eusthenopteron is best known. In recent years both that conclusion and the methodology by which it has been reached have been challenged by practitioners of cladistic analysis. Particularly a recent review by Rosen et al. (1981) claims that Dipnoi (lungfish) are the sister‐group of the Tetrapoda, that Osteolepiformes is a non‐taxon and that Eusthenopteron is more distant from tetrapods than are Dipnoi, coelacanths and probably the fossil Porolepiformes. We attempt to refute all these concludions by use of the same cladistic technique. 2. We accept that all the above‐mentioned groups, together with some less well‐known taxa, can be united as Sarcopterygii by means of shared derived (apomorph) characters. We also agree that Porolepiformes and Actinistia (coelacanths) can be characterized as valid taxa. The primitive and enigmatic fossil fish Powichthys is accepted as representing the plesiomorph sister‐group of true porolepiforms. 3. Only two apomorph features, the course of the jaw adductor muscles and the position of incurrent and excurrent nostrils, appear to unite all the fish, living and fossil, currently regarded as Dipnoi. The characteristic tooth plates and the presence of petrodentine both exclude important primitive fossil forms. 4. Contrary to the opinion of Rosen et al., Osteolepiformes can be characterized — by the arrangement of bones forming the cheek plate, the presence of basal scutes to the fins and by the unjointed radials of the median fins. However, if these are true autapomorphies they exclude any osteolepiform from direct tetrapod ancestry. 5. Tetrapoda is a monophyletic group characterized by ten or more autapomorphies, including the bones of the cheek plate, a stapes and fenestra ovalis, and a series of characters of the appendicular skeleton. 6. Tetrapods have a true choana (internal nostril). We accept that the posterior (excurrent) nostril of Dipnoi is the homologue of the tetrapod choana. However, we assert that the posterior nostril of all bony fish is the homologue of the choana. This assertion would be refuted if any fish showed separate posterior nostril and choana. We reject the claim that this ‘three nostril condition’ occurred in porolepiforms and osteolepiforms. The evidence for a choana in porolepiforms is inadequate. Osteolepiforms had a true choana, characterized as in tetrapods by its relationship to the bones of the palate, but no third nostril. Dipnoans are not choanate. 7. Following cladistic practice, the relationship of the extant taxa is established first. Dipnoi are thus shown to be the living sister‐group of tetrapods, but only on ‘soft anatomy’ characters unavailable in fossils. Coelacanths are the living sister‐group of the taxon so formed. 8. The relationship of the fossil taxa to the extant sarcopterygians is then considered. The synapomorphy scheme proposed by Rosen et al. is discussed at length. Virtually all the characters they use to exclude close relationship of Eusthenopteron (and hence all osteolepiforms) to tetrapods, in favour of coelacanths and dipnoans, are invalid. 9. A series of synapomorphies uniting osteolepiforms and tetrapods is proposed, including a true choana (hence the taxon Choanata), the histology of the teeth, and a number of characters of the humerus. The recently discovered fossil Youngolepis, which lacks a choana, represents the sister‐group of the Choanata, and is not uniquely close to Powichthys. The latter, as a porolepiform (s.l.) is a member of the sister‐group to Choanata plus Youngolepis. 10. Our cladistic analysis suggests that all the extinct taxa considered are more closely related to tetrapods than are the Dipnoi. Moreover fossil evidence suggests that Dipnoi, considered as an extant taxon, may not even be the living sister‐group of Tetrapoda. Early fossil dipnoans appear to have been marine fish without specific adaptations for air breathing. If so the apparent synapomorphies of Dipnoi and Tetrapoda may be homoplastic — the insistence on grouping extant taxa first would then have yielded an invalid inference.",
    url = "https://doi.org/10.1111/j.1469-185x.1987.tb01635.x",
    doi = "10.1111/j.1469-185x.1987.tb01635.x",
    openalex = "W1984016510",
    references = "doi101038237175a0"
}

Abstract- Several prominent cladists have questioned the importance of fossils in phylogenctic inference, and it is becoming increasingly popular to simply fit extinct forms, if they are considered at all, to a cladogram of Recent taxa. Gardiner's (1982) and Løvtrup's (1985) study of amniote phylogeny exemplifies this differential treatment, and we focused on that group of organisms to test the proposition that fossils cannot overturn a theory of relationships based only on the Recent biota. Our parsimony analysis of amniote phylogeny, special knowledge contributed by fossils being scrupulously avoided, led to the following best fitting classification, which is similar to the novel hypothesis Gardiner published: (lepidosaurs (turtles (mammals (birds, crocodiles)))). However, adding fossils resulted in a markedly different most parsimonious cladogram of the extant taxa: (mammals (turtles (lepidosaurs (birds, crocodiles)))). That classification is like the traditional hypothesis, and it provides a better fit to the stratigraphic record. To isolate the extinct taxa responsible for the latter classification, the data were successively partitioned with each phylogenetic analysis, and we concluded that: (1) the ingroup, not the outgroup, fossils were important; (2) synapsid, not reptile, fossils were pivotal; (3) certain synapsid fossils, not the earliest or latest, were responsible. The critical nature of the synapsid fossils seemed to lie in the particular combination of primitive and derived character slates they exhibited. Classifying those fossils, along with mammals, as the sister group to the lineage consisting of birds and crocodiles resulted in a relatively poor fit to data; one involving a 2-4 fold increase in evolutionary reversals! Thus, the importance of the critical fossils, collectively or individually, seems to reside in their relative primitive-ness, and the simplest explanation for their more conservative nature is that they have had less time to evolve. While fossils may be important in phylogenetic inference only under certain conditions, there is no compelling reason to prejudge their contribution. We urge systematists to evaluate fairly all of the available evidence.

@article{doi101111j109600311988tb00514x,
    author = "Gauthier, Jacques and Kluge, Arnold G. and Rowe, Timothy",
    title = "AMNIOTE PHYLOGENY AND THE IMPORTANCE OF FOSSILS",
    year = "1988",
    journal = "Cladistics",
    abstract = "Abstract- Several prominent cladists have questioned the importance of fossils in phylogenctic inference, and it is becoming increasingly popular to simply fit extinct forms, if they are considered at all, to a cladogram of Recent taxa. Gardiner's (1982) and Løvtrup's (1985) study of amniote phylogeny exemplifies this differential treatment, and we focused on that group of organisms to test the proposition that fossils cannot overturn a theory of relationships based only on the Recent biota. Our parsimony analysis of amniote phylogeny, special knowledge contributed by fossils being scrupulously avoided, led to the following best fitting classification, which is similar to the novel hypothesis Gardiner published: (lepidosaurs (turtles (mammals (birds, crocodiles)))). However, adding fossils resulted in a markedly different most parsimonious cladogram of the extant taxa: (mammals (turtles (lepidosaurs (birds, crocodiles)))). That classification is like the traditional hypothesis, and it provides a better fit to the stratigraphic record. To isolate the extinct taxa responsible for the latter classification, the data were successively partitioned with each phylogenetic analysis, and we concluded that: (1) the ingroup, not the outgroup, fossils were important; (2) synapsid, not reptile, fossils were pivotal; (3) certain synapsid fossils, not the earliest or latest, were responsible. The critical nature of the synapsid fossils seemed to lie in the particular combination of primitive and derived character slates they exhibited. Classifying those fossils, along with mammals, as the sister group to the lineage consisting of birds and crocodiles resulted in a relatively poor fit to data; one involving a 2-4 fold increase in evolutionary reversals! Thus, the importance of the critical fossils, collectively or individually, seems to reside in their relative primitive-ness, and the simplest explanation for their more conservative nature is that they have had less time to evolve. While fossils may be important in phylogenetic inference only under certain conditions, there is no compelling reason to prejudge their contribution. We urge systematists to evaluate fairly all of the available evidence.",
    url = "https://doi.org/10.1111/j.1096-0031.1988.tb00514.x",
    doi = "10.1111/j.1096-0031.1988.tb00514.x",
    openalex = "W1978557909",
    references = "crossref1943the, currie1985cranial, doi101001jama194302840160064031, doi1010079781468488517, doi101007978146848851721, doi101016002555648290027x, doi1010160169534789901626, doi101016b9781483198279500198, doi101016b9781483231426500124, doi101017cbo9780511693281002, doi101038142004a0, doi10108002724634198810011708, doi101086628623, doi101093sysbio1811, doi101093sysbio33183, doi1010970000505319311100000026, doi101098rstb19830079, doi101111j109636421977tb01031x, doi101111j109636421985tb01796x, doi101146annureven10010165000525, doi1023071005355, doi1023071220820, doi1023071292217, doi1023071441916, doi1023072412407, doi1023072412685, doi1023072413134, doi1023072413259, doi1023072413454, doi1023072485224, doi105281zenodo16171435, doi10560219780801847806, doi105962bhltitle6408, doi105962bhltitle82144, openalexw1534787790, openalexw1534857865, openalexw2954279587, openalexw2983381470, openalexw3146596760, openalexw3184837389, openalexw575222456, roaf1943the"
}

@misc{fricke1988coelecanths2,
    author = "Fricke, H",
    title = "Coelecanths",
    year = "1988",
    howpublished = "The Fish that Time Forgot: National Geographic, v. 173, no. 6, p. 824-838",
    note = "talkorigins\_source = {true}; raw\_reference = {Fricke, H., 1988, Coelecanths: The Fish that Time Forgot: National Geographic, v. 173, no. 6, p. 824-838.}"
}

@article{fricke1994home,
    author = "Fricke, H. and Hissmann, K.",
    title = "Home range and migrations of the living coelacanth Latimeria chalumnae",
    year = "1994",
    journal = "Marine Biology",
    url = "https://doi.org/10.1007/bf00349676",
    doi = "10.1007/bf00349676",
    number = "2",
    openalex = "W2066691122",
    pages = "171-180",
    volume = "120",
    references = "doi101002bimj19700120319, doi1010079781489929952, doi101016s0003347284802729, doi101038335719a0, doi1023072290299, doi1023072413259, doi1023073498751, doi104319lo19772250856, openalexw1487133581"
}

Abstract Measurements of the surface area of the gill lamellae of specimens of the coelacanth, Latimeria chalumnae have been made. This involved measurement of total filament length, frequency of lamellae along the filaments and the weighted average bilateral area of a single lamella. Regression analyses of these parameters which combine to give total area were made for the mass range 434 g—80 kg. Results show that the slope is close to 0.81 which is similar to that of many other fishes. However, the intercept value is exceptionally low and confirms the low mass-specific measurements made on two 10 kg specimens in 1972. Material from a recently caught specimen has been used to extend previous transmission electron microscopy by the use of scanning electron microscopy. The surface of epithelial cells on lamellae and filaments is covered in microvilli and microridges with transitional zones. The appearance of microridges suggests that they may have arisen by coalescence of microvilli. Ventilatory movements of the mouth and operculum (three to four per minute) have been observed using videorecordings of resting specimens in caves. Specimens of the larval stage of a gnathiid isopod parasite were found but only on one of the nine sets of gills that were examined. It is concluded that this more extended study of gill morphometrics of Latimeria confirms predictions made from earlier comparative studies regarding the life habits of this fish which have also been confirmed by direct observation using submersibles.

@article{doi101098rstb19950034,
    author = "Hughes, G. M.",
    title = "The gills of the coelacanth, Latimeria chalumnae, a study in relation to body size",
    year = "1995",
    journal = "Philosophical Transactions of the Royal Society B Biological Sciences",
    abstract = "Abstract Measurements of the surface area of the gill lamellae of specimens of the coelacanth, Latimeria chalumnae have been made. This involved measurement of total filament length, frequency of lamellae along the filaments and the weighted average bilateral area of a single lamella. Regression analyses of these parameters which combine to give total area were made for the mass range 434 g—80 kg. Results show that the slope is close to 0.81 which is similar to that of many other fishes. However, the intercept value is exceptionally low and confirms the low mass-specific measurements made on two 10 kg specimens in 1972. Material from a recently caught specimen has been used to extend previous transmission electron microscopy by the use of scanning electron microscopy. The surface of epithelial cells on lamellae and filaments is covered in microvilli and microridges with transitional zones. The appearance of microridges suggests that they may have arisen by coalescence of microvilli. Ventilatory movements of the mouth and operculum (three to four per minute) have been observed using videorecordings of resting specimens in caves. Specimens of the larval stage of a gnathiid isopod parasite were found but only on one of the nine sets of gills that were examined. It is concluded that this more extended study of gill morphometrics of Latimeria confirms predictions made from earlier comparative studies regarding the life habits of this fish which have also been confirmed by direct observation using submersibles.",
    url = "https://doi.org/10.1098/rstb.1995.0034",
    doi = "10.1098/rstb.1995.0034",
    openalex = "W2022374343",
    references = "doi101038237175a0, hughes1972gills"
}

Coelacanths Latllnena chalumnae are the only liv~ng representatives of crossopterygian fish close to the roots of our own vertebrate history and therefore occupy a unique positlon among living fossils. L. chalun~nae has become a synonym for long evolutionary age, timeless existence, tenacity, immortality and links to old roots, appearing in language, poetry, fiction and many art forms. It is a symbol of a new national identity in the Cornoro Archipelago, Western Indian Ocean. I consider here the Intrinsic and extrinsic value of coelacanths and the role of these fish in blodiversity conservation. The fate of coelacanths lies in our hands. It wlll be a measure of the success or failure of 'eco-ethics' as recently defined and called for by ecologists.

@article{doi103354meps161001,
    author = "Fricke, H.",
    title = "Living coelacanths:values, eco-ethics and human responsibility",
    year = "1997",
    journal = "Marine Ecology Progress Series",
    abstract = "Coelacanths Latllnena chalumnae are the only liv\textasciitilde ng representatives of crossopterygian fish close to the roots of our own vertebrate history and therefore occupy a unique positlon among living fossils. L. chalun\textasciitilde nae has become a synonym for long evolutionary age, timeless existence, tenacity, immortality and links to old roots, appearing in language, poetry, fiction and many art forms. It is a symbol of a new national identity in the Cornoro Archipelago, Western Indian Ocean. I consider here the Intrinsic and extrinsic value of coelacanths and the role of these fish in blodiversity conservation. The fate of coelacanths lies in our hands. It wlll be a measure of the success or failure of 'eco-ethics' as recently defined and called for by ecologists.",
    url = "https://doi.org/10.3354/meps161001",
    doi = "10.3354/meps161001",
    openalex = "W2078365479",
    references = "doi101007978940113194027"
}

@article{doi101006mpev19980495,
    author = "Goodman, Morris and Porter, Calvin A. and Czelusniak, John and Page, Scott L. and Schneider, Horacio and Shoshani, Jeheskel and Gunnell, Gregg F. and Groves, Colin P.",
    title = "Toward a Phylogenetic Classification of Primates Based on DNA Evidence Complemented by Fossil Evidence",
    year = "1998",
    journal = "Molecular Phylogenetics and Evolution",
    url = "https://doi.org/10.1006/mpev.1998.0495",
    doi = "10.1006/mpev.1998.0495",
    openalex = "W2058993504",
    references = "crossref1995systematics, doi102110pec9504, doi102110pec9554, doi1023071375443, doi1023072412685, doi1043249781315081083, doi105281zenodo18028696, doi105860choice323881, doi105860choice352112, openalexw1964182146"
}

@incollection{nieuwenhuys1998the,
    author = "Nieuwenhuys, R.",
    title = "The Coelacanth Latimeria chalumnae",
    year = "1998",
    booktitle = "The Central Nervous System of Vertebrates",
    url = "https://doi.org/10.1007/978-3-642-18262-4\_17",
    doi = "10.1007/978-3-642-18262-4\_17",
    openalex = "W108514220",
    pages = "1007-1043",
    references = "crossref1980comparative, doi1023071441916, doi1023071447582, doi1023072412482, doi1023072413058, doi1023072413259, doi105962bhltitle3596, doi107326000348196712335, howells1950genetics, openalexw301193904"
}

The coelacanth, a "living fossil," lives near the coast of the Comoros archipelago in the Indian Ocean. Living at a depth of about 200 m, the Comoran coelacanth receives only a narrow range of light, at about 480 nm. To detect the entire range of "color" at this depth, the coelacanth appears to use only two closely related paralogous RH1 and RH2 visual pigments with the optimum light sensitivities (lambdamax) at 478 nm and 485 nm, respectively. The lambdamax values are shifted about 20 nm toward blue compared with those of the corresponding orthologous pigments. Mutagenesis experiments show that each of these coadapted changes is fully explained by two amino acid replacements.

@article{doi101073pnas96116279,
    author = "Yokoyama, Shozo and Zhang, Huan and Radlwimmer, Bernhard and Blow, Nathan",
    title = "Adaptive evolution of color vision of the Comoran coelacanth (Latimeria chalumnae)",
    year = "1999",
    journal = "Proceedings of the National Academy of Sciences",
    abstract = {The coelacanth, a "living fossil," lives near the coast of the Comoros archipelago in the Indian Ocean. Living at a depth of about 200 m, the Comoran coelacanth receives only a narrow range of light, at about 480 nm. To detect the entire range of "color" at this depth, the coelacanth appears to use only two closely related paralogous RH1 and RH2 visual pigments with the optimum light sensitivities (lambdamax) at 478 nm and 485 nm, respectively. The lambdamax values are shifted about 20 nm toward blue compared with those of the corresponding orthologous pigments. Mutagenesis experiments show that each of these coadapted changes is fully explained by two amino acid replacements.},
    url = "https://doi.org/10.1073/pnas.96.11.6279",
    doi = "10.1073/pnas.96.11.6279",
    openalex = "W2071412636",
    references = "doi101098rspb19800052"
}

The morphology of the nephrons of the coelacanth Latimeria chalumnae was investigated by light microscopy. Each nephron is composed of a large renal corpuscle with well‐vascularized glomerulus, non‐ciliated neck segment, proximal convoluted tubule divided into distinct first and second segments, non‐ciliated intermediate segment, distal tubule, collecting tubule and collecting duct. The parietal layer of the Bowman's capsule of the renal corpuscle is composed of low cuboidal cells. The short non‐ciliated neck segment is lined by cuboidal epithelium. The first and second proximal segments display a prominent brush border and contain amorphous material in their lumen. The second proximal segment differs from the first segment in having taller columnar epithelium and a relatively narrow lumen. The intermediate segment is lined by non‐ciliated columnar epithelium and its lumen appears empty. The distal tubule is narrow in diameter and its cuboidal epithelium is devoid of intercalated cells. A unique feature of L. chalumnae is having binucleate cells in the tubule and collecting duct epithelium. The renal arteries have poorly developed tunica media and its cells contain granular material. The structure of L. chalumnae nephrons correlates well with their osmoregulatory function and resembles those of euryhaline teleosts.

@article{doi101111j10958649200902522x,
    author = "Jarial, Mohinder S. and Wilkins, John H.",
    title = "Structure of the kidney in the coelacanth Latimeria chalumnae with reference to osmoregulation",
    year = "2010",
    journal = "Journal of Fish Biology",
    abstract = "The morphology of the nephrons of the coelacanth Latimeria chalumnae was investigated by light microscopy. Each nephron is composed of a large renal corpuscle with well‐vascularized glomerulus, non‐ciliated neck segment, proximal convoluted tubule divided into distinct first and second segments, non‐ciliated intermediate segment, distal tubule, collecting tubule and collecting duct. The parietal layer of the Bowman's capsule of the renal corpuscle is composed of low cuboidal cells. The short non‐ciliated neck segment is lined by cuboidal epithelium. The first and second proximal segments display a prominent brush border and contain amorphous material in their lumen. The second proximal segment differs from the first segment in having taller columnar epithelium and a relatively narrow lumen. The intermediate segment is lined by non‐ciliated columnar epithelium and its lumen appears empty. The distal tubule is narrow in diameter and its cuboidal epithelium is devoid of intercalated cells. A unique feature of L. chalumnae is having binucleate cells in the tubule and collecting duct epithelium. The renal arteries have poorly developed tunica media and its cells contain granular material. The structure of L. chalumnae nephrons correlates well with their osmoregulatory function and resembles those of euryhaline teleosts.",
    url = "https://doi.org/10.1111/j.1095-8649.2009.02522.x",
    doi = "10.1111/j.1095-8649.2009.02522.x",
    openalex = "W2013095190",
    references = "dingerkus1978the"
}

Vertebrate morphology, including developmental anatomy, has depended on dissection since anatomical study first began, and on microscopy since the 19th century, in particular since the invention of the microtome. These methods have limitations: dissection destroys tissues, and disturbs or destroys three-dimensional relationships. Microscopy is less destructive, in that sections can be preserved for periods of time, but cutting serial sections, as often used in developmental anatomy, is time-consuming, sections are easily lost in processing, and distortion can be a problem. Three-dimensional (3D) reconstruction for interpretation and demonstration of results was done with manual drawing techniques or physical reconstruction with sequential wax plates, but now can be done with image reconstruction software. Microscopy findings still need to be photographed, aligned and segmented -the tissues of interest identified and marked out on 2D slices -before a result can be obtained, all of which is still relatively labour-intensive. Functional morphology became accessible with the invention of the motion-picture camera, and cinefluoroscopy with implanted radiological markers has provided many explanations. These traditional techniques have been supplemented in recent years by cross-sectional imaging and advanced techniques that depend on this imaging. CT (computed tomography) and MRI (magnetic resonance imaging) are best known as medical imaging technologies, but have a range of applications in morphology. Newer and more accurate techniques of imaging, real-time imaging for functional study and methods of image reconstruction are revolutionizing vertebrate morphology, bringing 3D information in a non-destructive manner. Rare museum specimens are often not made available for dissection, and these may be important taxa for biological and phylogenetic reasons; imaging techniques have an important application here. This chapter will review a number of new imaging techniques used in comparative morphology, with examples of recent applications, and will present original research demonstrating a number of these techniques to investigate a morphological mystery, the intracranial joint of the coelacanth Latimeria chalumnae.

@incollection{doi10577221982,
    author = "Johnston, Peter",
    title = "Cross-Sectional Imaging in Comparative Vertebrate Morphology - The Intracranial Joint of the Coelacanth Latimeria chalumnae",
    year = "2011",
    booktitle = "InTech eBooks",
    abstract = "Vertebrate morphology, including developmental anatomy, has depended on dissection since anatomical study first began, and on microscopy since the 19th century, in particular since the invention of the microtome. These methods have limitations: dissection destroys tissues, and disturbs or destroys three-dimensional relationships. Microscopy is less destructive, in that sections can be preserved for periods of time, but cutting serial sections, as often used in developmental anatomy, is time-consuming, sections are easily lost in processing, and distortion can be a problem. Three-dimensional (3D) reconstruction for interpretation and demonstration of results was done with manual drawing techniques or physical reconstruction with sequential wax plates, but now can be done with image reconstruction software. Microscopy findings still need to be photographed, aligned and segmented -the tissues of interest identified and marked out on 2D slices -before a result can be obtained, all of which is still relatively labour-intensive. Functional morphology became accessible with the invention of the motion-picture camera, and cinefluoroscopy with implanted radiological markers has provided many explanations. These traditional techniques have been supplemented in recent years by cross-sectional imaging and advanced techniques that depend on this imaging. CT (computed tomography) and MRI (magnetic resonance imaging) are best known as medical imaging technologies, but have a range of applications in morphology. Newer and more accurate techniques of imaging, real-time imaging for functional study and methods of image reconstruction are revolutionizing vertebrate morphology, bringing 3D information in a non-destructive manner. Rare museum specimens are often not made available for dissection, and these may be important taxa for biological and phylogenetic reasons; imaging techniques have an important application here. This chapter will review a number of new imaging techniques used in comparative morphology, with examples of recent applications, and will present original research demonstrating a number of these techniques to investigate a morphological mystery, the intracranial joint of the coelacanth Latimeria chalumnae.",
    url = "https://doi.org/10.5772/21982",
    doi = "10.5772/21982",
    openalex = "W1555045199",
    references = "doi101007978940113194027, doi101007bf00007469"
}

The fossil record of coelacanths is patchy, with very few taxa known from the Triassic of Asia. We report here two new genera and species of coelacanths from the Luoping Biota, a recently found site of exceptional fossil preservation from Yunnan, South China. The first new taxon, Luopingcoelacanthus eurylacrimalis, is based on four specimens, which together show most aspects of the anatomy. One specimen shows two small coelacanths inside the ventral portion of the abdominal cavity, and these are interpreted as intrauterine embryos, close to birth size, based on comparisons with previously reported embryos of the fossil coelacanths Rhabdoderma and Undina, and the extant genus Latimeria. Our new find extends the evidence for ovoviviparity in coelacanths back from the Late Jurassic to the Middle Triassic. The second new taxon, Yunnancoelacanthus acrotuberculatus, is based on one specimen, and differs from Luopingcoelacanthus in the dentary, lachrymojugal, number of rays of the first dorsal fin, and especially in the ornament on dermal bones and scales. Acladistic analysis shows that the new taxa are closest relatives to the derived clade Latimerioidei. The relatively high diversity of coelacanths in the Early Triassic, and adaptations of living Latimeria to low-oxygen conditions, suggests that the group may have included 'disaster taxa' that benefited from anoxic and dysoxic ocean conditions in the aftermath of the end-Permian mass extinction.

@article{doi104202app20110066,
    author = "Wen, Wen",
    title = "Coelacanths from the Middle Triassic Luoping Biota, Yunnan, South China, with the earliest evidence of ovoviviparity",
    year = "2012",
    journal = "Acta Palaeontologica Polonica",
    abstract = "The fossil record of coelacanths is patchy, with very few taxa known from the Triassic of Asia. We report here two new genera and species of coelacanths from the Luoping Biota, a recently found site of exceptional fossil preservation from Yunnan, South China. The first new taxon, Luopingcoelacanthus eurylacrimalis, is based on four specimens, which together show most aspects of the anatomy. One specimen shows two small coelacanths inside the ventral portion of the abdominal cavity, and these are interpreted as intrauterine embryos, close to birth size, based on comparisons with previously reported embryos of the fossil coelacanths Rhabdoderma and Undina, and the extant genus Latimeria. Our new find extends the evidence for ovoviviparity in coelacanths back from the Late Jurassic to the Middle Triassic. The second new taxon, Yunnancoelacanthus acrotuberculatus, is based on one specimen, and differs from Luopingcoelacanthus in the dentary, lachrymojugal, number of rays of the first dorsal fin, and especially in the ornament on dermal bones and scales. Acladistic analysis shows that the new taxa are closest relatives to the derived clade Latimerioidei. The relatively high diversity of coelacanths in the Early Triassic, and adaptations of living Latimeria to low-oxygen conditions, suggests that the group may have included 'disaster taxa' that benefited from anoxic and dysoxic ocean conditions in the aftermath of the end-Permian mass extinction.",
    url = "https://doi.org/10.4202/app.2011.0066",
    doi = "10.4202/app.2011.0066",
    openalex = "W2131937846",
    references = "doi101126science19042191105"
}

The morphology of the nephrons of the coelacanth Latimeria chalumnae was investigated by electron microscopy. Each nephron is composed of a large renal corpuscle with well vascularized glomerulus, ciliated neck segment, proximal tubule divided into first and second proximal segments, ciliated intermediate segment, distal tubule, collecting tubule, and duct. The podocytes of visceral epithelium contain large bi-lobed nuclei and their surface membranes pinch off vesicles into the cytoplasm. The processes of the podocytes give rise to pedicels that enclose narrow filtration slits. The endothelium of glomerular capillaries is attenuated and fenestrated. The short cytoplasmic processes of mesangial cells do not penetrate deeply into the sub-endothelial lamina. The glomerular basement membrane is about 286 nm in thickness. The pedicels also arise from podocyte cell bodies, and are connected by diaphragms and enclose slits, which open into narrow urinary spaces between podocytes. The cuboidal cells of the short neck segment display cilia with a characteristic pattern of 9+2 microtubules. The first proximal tubule segment differs from the second proximal segment in having densely packed microvilli, prominent endocytotic-lysosomal apparatus, and numerous basal membrane infoldings associated with mitochondria. The lateral cell membranes like those of other segments are straight and joined by desmosomes and apical adhering and tight junctions. The distal tubules display few short luminal microvilli and numerous basal mitochondria. The distal tubule, collecting tubule and duct are devoid of intercalated cells. The ultrastructure of the L chalumnae nephrons correlates well with their osmoregulatory function and resembles that of freshwater rainbow trout.

@article{doi102108zs130192,
    author = "Jarial, Mohinder S. and Gattone, Vincent H. and Wilkins, John H.",
    title = "Ultrastructural Study of the Kidney in the Coelacanth Latimeria chalumnae (Rhipidistia: Coelacanthini)",
    year = "2014",
    journal = "ZOOLOGICAL SCIENCE",
    abstract = "The morphology of the nephrons of the coelacanth Latimeria chalumnae was investigated by electron microscopy. Each nephron is composed of a large renal corpuscle with well vascularized glomerulus, ciliated neck segment, proximal tubule divided into first and second proximal segments, ciliated intermediate segment, distal tubule, collecting tubule, and duct. The podocytes of visceral epithelium contain large bi-lobed nuclei and their surface membranes pinch off vesicles into the cytoplasm. The processes of the podocytes give rise to pedicels that enclose narrow filtration slits. The endothelium of glomerular capillaries is attenuated and fenestrated. The short cytoplasmic processes of mesangial cells do not penetrate deeply into the sub-endothelial lamina. The glomerular basement membrane is about 286 nm in thickness. The pedicels also arise from podocyte cell bodies, and are connected by diaphragms and enclose slits, which open into narrow urinary spaces between podocytes. The cuboidal cells of the short neck segment display cilia with a characteristic pattern of 9+2 microtubules. The first proximal tubule segment differs from the second proximal segment in having densely packed microvilli, prominent endocytotic-lysosomal apparatus, and numerous basal membrane infoldings associated with mitochondria. The lateral cell membranes like those of other segments are straight and joined by desmosomes and apical adhering and tight junctions. The distal tubules display few short luminal microvilli and numerous basal mitochondria. The distal tubule, collecting tubule and duct are devoid of intercalated cells. The ultrastructure of the L chalumnae nephrons correlates well with their osmoregulatory function and resembles that of freshwater rainbow trout.",
    url = "https://doi.org/10.2108/zs130192",
    doi = "10.2108/zs130192",
    openalex = "W2143816821",
    references = "doi101098rspb19800052, doi101098rspb19800054"
}

Today, the only living genus of coelacanth, Latimeria is represented by two species along the eastern coast of Africa and in Indonesia. This sarcopterygian fish is nicknamed a "living fossil", in particular because of its slow evolution. The large geographical distribution of Latimeria may be a reason for the great resilience to extinction of this lineage, but the lack of fossil records for this genus prevents us from testing this hypothesis. Here we describe isolated bones (right angular, incomplete basisphenoid, fragments of parasphenoid and pterygoid) found in the Cenomanian Woodbine Formation in northeast Texas that are referred to the mawsoniid coelacanth Mawsonia sp. In order to assess the impact of this discovery on the alleged characteristic of "living fossils" in general and of coelacanths in particular: 1) we compared the average time duration of genera of ray-finned fish and coelacanth in the fossil record; 2) we compared the biogeographic signal from Mawsonia with the signal from the rest of the vertebrate assemblage of the Woodbine formation; and 3) we compared these life traits with those of Latimeria. The stratigraphical range of Mawsonia is at least 50 million years. Since Mawsonia was a fresh, brackish water fish with probably a low ability to cross large sea barriers and because most of the continental components of the Woodbine Fm vertebrate assemblage exhibit Laurasian affinities, it is proposed that the Mawsonia's occurrence in North America is more likely the result of a vicariant event linked to the break-up of Pangea rather than the result of a dispersal from Gondwana. The link between a wide geographic distribution and the resilience to extinction demonstrated here for Mawsonia is a clue that a similar situation existed for Latimeria, which allowed this genus to live for tens of millions of years.

@article{doi101371journalpone0259292,
    author = "Cavin, Lionel and Toriño, Pablo and Vranken, Nathan Van and Carter, Brad and Polcyn, Michael J. and Winkler, Dale",
    title = "The first late cretaceous mawsoniid coelacanth (Sarcopterygii: Actinistia) from North America: Evidence of a lineage of extinct ‘living fossils’",
    year = "2021",
    journal = "PLoS ONE",
    abstract = {Today, the only living genus of coelacanth, Latimeria is represented by two species along the eastern coast of Africa and in Indonesia. This sarcopterygian fish is nicknamed a "living fossil", in particular because of its slow evolution. The large geographical distribution of Latimeria may be a reason for the great resilience to extinction of this lineage, but the lack of fossil records for this genus prevents us from testing this hypothesis. Here we describe isolated bones (right angular, incomplete basisphenoid, fragments of parasphenoid and pterygoid) found in the Cenomanian Woodbine Formation in northeast Texas that are referred to the mawsoniid coelacanth Mawsonia sp. In order to assess the impact of this discovery on the alleged characteristic of "living fossils" in general and of coelacanths in particular: 1) we compared the average time duration of genera of ray-finned fish and coelacanth in the fossil record; 2) we compared the biogeographic signal from Mawsonia with the signal from the rest of the vertebrate assemblage of the Woodbine formation; and 3) we compared these life traits with those of Latimeria. The stratigraphical range of Mawsonia is at least 50 million years. Since Mawsonia was a fresh, brackish water fish with probably a low ability to cross large sea barriers and because most of the continental components of the Woodbine Fm vertebrate assemblage exhibit Laurasian affinities, it is proposed that the Mawsonia's occurrence in North America is more likely the result of a vicariant event linked to the break-up of Pangea rather than the result of a dispersal from Gondwana. The link between a wide geographic distribution and the resilience to extinction demonstrated here for Mawsonia is a clue that a similar situation existed for Latimeria, which allowed this genus to live for tens of millions of years.},
    url = "https://doi.org/10.1371/journal.pone.0259292",
    doi = "10.1371/journal.pone.0259292",
    openalex = "W3214270674",
    references = "fricke1994home, openalexw1909835793"
}

BACKGROUND: Buoyancy and balance are important parameters for slow-moving, low-metabolic, aquatic organisms. The extant coelacanths have among the lowest metabolic rates of any living vertebrate and can afford little energy to keep station. Previous observations on living coelacanths support the hypothesis that the coelacanth is neutrally buoyant and in close-to-perfect hydrostatic balance. However, precise measurements of buoyancy and balance at different depths have never been made. RESULTS: Here we show, using non-invasive imaging, that buoyancy of the coelacanth closely matches its depth distribution. We found that the lipid-filled fatty organ is well suited to support neutral buoyancy, and due to a close-to-perfect hydrostatic balance, simple maneuvers of fins can cause a considerable shift in torque around the pitch axis allowing the coelacanth to assume different body orientations with little physical effort. CONCLUSIONS: Our results demonstrate a close match between tissue composition, depth range and behavior, and our collection-based approach could be used to predict depth range of less well-studied coelacanth life stages as well as of deep sea fishes in general.

@article{doi101186s12915022013548,
    author = "Lauridsen, Henrik and Pedersen, Jens Mikkel Hyllested and Ringgaard, Steffen and Möller, Peter",
    title = "Buoyancy and hydrostatic balance in a West Indian Ocean coelacanth Latimeria chalumnae",
    year = "2022",
    journal = "BMC Biology",
    abstract = "BACKGROUND: Buoyancy and balance are important parameters for slow-moving, low-metabolic, aquatic organisms. The extant coelacanths have among the lowest metabolic rates of any living vertebrate and can afford little energy to keep station. Previous observations on living coelacanths support the hypothesis that the coelacanth is neutrally buoyant and in close-to-perfect hydrostatic balance. However, precise measurements of buoyancy and balance at different depths have never been made. RESULTS: Here we show, using non-invasive imaging, that buoyancy of the coelacanth closely matches its depth distribution. We found that the lipid-filled fatty organ is well suited to support neutral buoyancy, and due to a close-to-perfect hydrostatic balance, simple maneuvers of fins can cause a considerable shift in torque around the pitch axis allowing the coelacanth to assume different body orientations with little physical effort. CONCLUSIONS: Our results demonstrate a close match between tissue composition, depth range and behavior, and our collection-based approach could be used to predict depth range of less well-studied coelacanth life stages as well as of deep sea fishes in general.",
    url = "https://doi.org/10.1186/s12915-022-01354-8",
    doi = "10.1186/s12915-022-01354-8",
    openalex = "W4292509009",
    references = "doi101002jez1401920206, doi101038237175a0"
}

Anatomical features that have not been previously described in Latimeria were sought in histological section series, tissue-stained microCT scans, MRI scans, and synchrotron scan series. The spiracular organ, ultimobranchial endocrine gland, and m. cucullaris were identified in the expected locations. In addition, a muscle arising on the medial side of the pectoral girdle is identified and compared with a muscle in a similar location that attaches to the cranial rib in lungfish; these are proposed as homologues of the tetrapod m. omohyoideus. These findings are placed in evolutionary context by comparison with selected other groups of fish, lungfish and tetrapods. The position of Latimeria as a key taxon in the fish-to-tetrapod transition is emphasised by these findings, and the findings have potential to inform research on cranial structure in extinct taxa.

@article{johnston2022the,
    author = "Johnston, Peter",
    title = "The missing anatomy of the living coelacanth, Latimeria chalumnae (Smith, 1939)",
    year = "2022",
    journal = "Vertebrate Zoology",
    abstract = "Anatomical features that have not been previously described in Latimeria were sought in histological section series, tissue-stained microCT scans, MRI scans, and synchrotron scan series. The spiracular organ, ultimobranchial endocrine gland, and m. cucullaris were identified in the expected locations. In addition, a muscle arising on the medial side of the pectoral girdle is identified and compared with a muscle in a similar location that attaches to the cranial rib in lungfish; these are proposed as homologues of the tetrapod m. omohyoideus. These findings are placed in evolutionary context by comparison with selected other groups of fish, lungfish and tetrapods. The position of Latimeria as a key taxon in the fish-to-tetrapod transition is emphasised by these findings, and the findings have potential to inform research on cranial structure in extinct taxa.",
    url = "https://doi.org/10.3897/vz.72.e84274",
    doi = "10.3897/vz.72.e84274",
    openalex = "W4285490446",
    pages = "513-531",
    volume = "72",
    references = "doi101038ncomms2036, doi101038s4158601911173, doi10118614726793911, doi101186s1286201709583, doi1023071441701, doi1023072413058, doi105962bhltitle82144, doi107554elife40179, openalexw563680134, openalexw628087051"
}

@article{doi101038s41586022056661,
    author = "Figueroa, Rodrigo Tinoco and Goodvin, Danielle and Kolmann, Matthew A. and Coates, Michael I. and Caron, Abigail M. and Friedman, Matt and Giles, Sam",
    title = "Exceptional fossil preservation and evolution of the ray-finned fish brain",
    year = "2023",
    journal = "Nature",
    url = "https://doi.org/10.1038/s41586-022-05666-1",
    doi = "10.1038/s41586-022-05666-1",
    openalex = "W4318776571",
    references = "nieuwenhuys1998the, schmidt2020evolution"
}

Mawsonia constitutes one of the most conspicuous fossil coelacanth taxa, due to its unique anatomy and possible maximum body size. It typifies Mesozoic coelacanth morphology, before the putative disappearance of the group in the fossil record. In this work, the three-dimensional cranial anatomy and body size estimations of this genus are re-evaluated from a recently described specimen from Upper Jurassic deposits of Uruguay. The 3D restoration was performed directly on the material based on anatomical information provided by the living coelacanth Latimeria and previous two-dimensional restorations of the head of Mawsonia. The montage was then scanned with computed tomography and virtually adjusted to generate an interactive online resource for future anatomical, taxonomic and biomechanical research. In general terms, the model constitutes a tool to improve both the anatomical knowledge of this genus and its comparison with other coelacanths. It also facilitates the evaluation of possible evolutionary trends and the discussion of particular features with potential palaeobiological implications, such as the anterior position of the eye and the development of the pseudomaxillary fold. Regarding the body size, a previous model for body size estimation based on the gular plate was submitted to OLS, RMA, segmented linear and PGLS regressions (including the evaluation of regression statistics, variance analysis, t-tests and residual analysis). The results point to a power relationship between gular and total lengths showing a better support than a simple linear relationship. The new resulting equations were applied to the studied individual and are provided for future estimates. Although an isometric evolutionary growth cannot be rejected with the available evidence, additional models developed with other bones will be necessary to evaluate possible hidden evolutionary allometric trends in this group of fishes, thus avoiding overestimates.

@article{doi101111joa14054,
    author = "Toriño, Pablo and Dutel, Hugo and Soto, Matías and Norbis, Walter and Ezquerra, Víctor and Perea, Daniel",
    title = "Reconstructing an ancient fish: Three‐dimensional skeletal restoration of the head of Mawsonia (Sarcopterygii, Actinistia) using CT scan, and an adjusted model for body size estimation in fossil coelacanths",
    year = "2024",
    journal = "Journal of Anatomy",
    abstract = "Mawsonia constitutes one of the most conspicuous fossil coelacanth taxa, due to its unique anatomy and possible maximum body size. It typifies Mesozoic coelacanth morphology, before the putative disappearance of the group in the fossil record. In this work, the three-dimensional cranial anatomy and body size estimations of this genus are re-evaluated from a recently described specimen from Upper Jurassic deposits of Uruguay. The 3D restoration was performed directly on the material based on anatomical information provided by the living coelacanth Latimeria and previous two-dimensional restorations of the head of Mawsonia. The montage was then scanned with computed tomography and virtually adjusted to generate an interactive online resource for future anatomical, taxonomic and biomechanical research. In general terms, the model constitutes a tool to improve both the anatomical knowledge of this genus and its comparison with other coelacanths. It also facilitates the evaluation of possible evolutionary trends and the discussion of particular features with potential palaeobiological implications, such as the anterior position of the eye and the development of the pseudomaxillary fold. Regarding the body size, a previous model for body size estimation based on the gular plate was submitted to OLS, RMA, segmented linear and PGLS regressions (including the evaluation of regression statistics, variance analysis, t-tests and residual analysis). The results point to a power relationship between gular and total lengths showing a better support than a simple linear relationship. The new resulting equations were applied to the studied individual and are provided for future estimates. Although an isometric evolutionary growth cannot be rejected with the available evidence, additional models developed with other bones will be necessary to evaluate possible hidden evolutionary allometric trends in this group of fishes, thus avoiding overestimates.",
    url = "https://doi.org/10.1111/joa.14054",
    doi = "10.1111/joa.14054",
    openalex = "W4396974212",
    references = "johnston2022the"
}