Hostname: page-component-78c5997874-lj6df Total loading time: 0 Render date: 2024-11-08T08:24:31.861Z Has data issue: false hasContentIssue false
  • English
  • Français

On the Structures of the Dermal Ethmoid Shield of Osteolepis

Published online by Cambridge University Press:  01 May 2009

T. Stanley Westoll
T. Stanley Westoll
Affiliation:
University College, London.
Get access Rights & Permissions [Opens in a new window]

Summary

The structure of the fronto-ethmoid shield of Osteolepis macrolepidotus Ag. is described fully for the first time, and the homology of the dermal bones is discussed. The most interesting feature is the recognition of the existence of a sensory-canal bone bearing teeth in the position of the premaxillary of Tetrapods, with which it is shown to be homologous; the nomenclature of the equivalent bones suggested by Säve-Söderbergh is discussed and revised.

The presence of a continuous cosmine sheet overlying several bones is emphasized, and the problem of growth of such a combination is brought out. It is shown that the problem can be solved by extensive resorption and redeposition of cosmine, and this hitherto unnoticed change is demonstrated in a number ofOsteolepids and in some Dipnoi. The results of the resorption are to free the bones of the head from the cosmine, and thus to expose the top of the true bone ; the new characters are those usually associated with different genera, usually placed in distinct families.

Finally it is noted that the resorption involves a general chemical change affecting cosmine all over the body, which it is suggested may be due to the release of an internal secretion, the whole process of resorption and redeposition of cosmine being cyclic and almost certainly seasonal, growth being therefore a seasonal change.

Type
Original Articles
Information
Geological Magazine , Volume 73 , Issue 4 , April 1936 , pp. 157 - 171
Copyright
Copyright © Cambridge University Press 1936

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

BIBLIOGRAPHY

Forster, Cooper C., (In the press) Dipterus from Achanarras.Google Scholar
Goodrich, E. S., 1908. “On the Scales of Fish,” Proc. Zool. Soc. Lond., 1907, p. 751.Google Scholar
Hills, E. S., 1933. “On a primitive Dipnoan from the Middle Devonian Rocks of New South Wales,” Ann. Mag. Nat. Hist. (10), xi, p. 634.CrossRefGoogle Scholar
Mccoy, F., 1855. Systematic Description of British Palaeozoic Fossils, in Sedgwick and McCoy, The British Palaeozoic Rocks and Fossils, London.Google Scholar
Moy-Thomas, J. A., 1934. “On the Teeth of the larval Belone vulgaris, and the attachment of Teeth in Fishes,” Quart. Journ. Microsc. Sci., 76, p. 481.Google Scholar
Pehrson, T., 1922. “Some Points in the Cranial Development of Teleostomian Fishes,” Acta Zoologica, Bd 3, p. 1.CrossRefGoogle Scholar
Säve-Söderbergh, G., 1932. “Preliminary Note on Devonian Stegocephalians from East Greenland,” Medd. om Grönland, 94, No. 7.Google Scholar
Säve-Söderbergh, G., 1933. “The dermal bones of the head and the lateral-line system in Osteolepis macrolepidotus Ag., etc.”. Nov. Act. Reg. Soc. Scient, Upsaliensis (iv), 9, No. 2.Google Scholar
Säve-Söderbergh, G., 1935. “On the Dermal Bones of the Head in Labyrinthodont Stegocephalians and Primitive Reptilia, etc.,” Medd. om Grönland, 98, no. 3.Google Scholar
Stensiö, E. A., 1922. “Notes on certain Crossopterygians,” Proc. Zool. Soc. Lond., 1922, 1241.Google Scholar
Swinnerton, H. H., 1923. Outlines of Palaeontology, London (another edition, 1930).Google Scholar
Traquair, R. H., 1888. “Notes on the Nomenclature of the Fishes of the Old Red Sandstone of Great Britain,” Geol. Mag., 516.Google Scholar
Watson, D. M. S., 1925. “The Structure of Certain Palaeoniscids, and the relationship of that group with other Bony Fish,” Proc. Zool. Soc. Lond., 1925, 815.CrossRefGoogle Scholar
Woodward, A. Smith, 1891: Catalogue of Fossil Fishes, part ii, British Mus. (Nat. Hist.).Google Scholar