The structure of certain Jurassic holostean fishes, with special reference to their neurocrania

Abstract

The term Holostei is in the process of being transformed from one expressing (or intending to express) some phylogenetic type of classification into one denoting a structural grade— a transformation commonly suffered by a term of long standing as the essential characters of its component genera are better understood. Unfortunately, understanding of this particular stage in Actinopterygian evolution is far from complete, and at present it is not possible to replace the old classification by one that will not have to be thoroughly revised in a few years’ time. Since, therefore, the present work (which was essentially complete in 1940) deals primarily with the structure of a few Jurassic neurocrania the term Holostei may still serve conveniently to cover the families in which they are found, although the origin of these is largely unknown and their degree of relationship a matter of debate. It will be found that a study of neurocrania occasionally produces some new evidence on these problems, but for a more complete'discussion on classification reference may be made to those works expressly dealing with the subject, especially Brough (1939), Rayner (1941) and Westoll (1944)

The skull and pectoral girdle of the parasemionotid fishWatsonulus eugnathoidesfrom the Early Triassic Sakamena Group of Madagascar, with comments on the relationships of the holostean fishes

“…In the degree of ossification, proportions, and many other details, the neurocranium of Watsonulus is similar to Heterolepidotus (Patterson, 1975), Macrepistius (Schaeffer,197 l), Caturus (Rayner, 1948), and, of course, other parasemionotids, especially the Early Triassic specimen from East Greenland figured by Patterson (1975, figs. 24-28).…”

The Strawberry Bank Lagerstätte reveals insights into Early Jurassic life

“…The scales are thick and shiny-surfaced, rhombic in shape. The amiiform Caturus is known from two specimens, including an isolated neurocranium (BRLSI M1288), which Rayner (1948) described in detail from serial sections.…”

Morphology of theSemionotus elegansspecies group from the Early Jurassic part of the Newark Supergroup of eastern North America with comments on the Family Semionotidae (Neopterygii)

“…Rayner (1948) first pointed out the uniquely shared features of the "epiotic" in Lepisosteus and semionotids. The possible homology of the these "epiotics" with the pterotic is discussed extensively by Patterson (1 975:452-454) although he does not comment explicitly on whether this similarity should be interpreted as primitive, convergent, or uniquely derived.…”

“…8E1). Dorsally, the metapterygoid is split into a medially directed flange forming the posteromedial portion of the palate, and a dorsally directed flange which laps onto the hyomandibular as in Amia and Lepidotes (Allis, 1897;Rayner, 1948;Jarvik, 1980;.…”