A NLAV CRETACEOUS FISH. 
95 
structure, and the whole series as preserved is isospondylous. Lateral pits do not 
appear to have been present. 
Remains of ribs are adpressed to the vertebrse exposed behind the opercular, 
and these are attached just below the median line of the centra. Other remains of 
lengthy ribs are to be seen in the matrix below the last two vertebrse. The surfaces 
of some of the fragments, M*hich have an enamelled appearance, are channeled. The 
actual method of their attachment is obscured. 
The vertebrse are very distinct from those from Queensland concisely described 
and figured, but unnamed, by Smith Woodward (1894, p. 447.) 
Classifkation . — In view of the special interest attached to the osteology of 
Lower Cretaceous fislies, a fairly full descri])tion of this Flinders River fossil has been 
attempted, although the condition of some of the bones has made this difficult. It 
is with considerable diffidence that the writer records tentative views as to its actual 
classification. The cranium of Flindersicldhys denmeadi agrees in some respects 
with the general characters of the primitive Actino])terygii at the dawn of the 
Cretaceous era, as outlined by Smith W^oodward in his introduction to Vol. IV of his 
great ‘‘ Catalogue of Fossil Fishes.” It affords another example of the difficulty of 
separating "Ganoid” and ‘‘ Teleostean” groups. Unfortunately certain salient 
features used in diagnostic keys, such as those by Smith Woodward (1901, Part IV"), 
and Tate Regan (1909 and 1929), cannot be verified in the fossil, and its affinities 
can only be suggested on the evidence of the com])lex of characters available. The 
status of the Order Isospondyli has been recently criticised by W. Garstang (1931) 
in his interesting stvuly of ]4iyletic classification, and Goodrich (1909, p. 370) writes 
that “ the group can no longer be fitted into any ])hylogenetic scheme.” It is 
convenient, however, to ])lace FlindersicMhys with its completely ossified, symmetrical 
vertebrae, in this assemblage, as the term Isospondyli is in such general use. Although 
the fossil cannot be positively allocated to any of tlie families of the Isospondyli with 
which com]>arisons have been made, it is tentatively ])lace(l in the Family Elopidse. 
So far as the evidence is available, its complex of characters agrees fairly well with this 
group. W. G. Ridewood (1904, ]v 54) has expressed the opinion that the Elopidae 
are the most archaic of existing Teleosteans,” but adds that some of the extinct forms 
would seem to be more specialised than the living EJIoj^s and Megalops. 
The presence of a gular plate in Flindersichlhys is probably significatit, but tliis 
is also characteristic of the Amiidai, and other Arnioidei. 4die massive structure of 
the sub-orbital bones do not suggest close affinities with the Oligopleurida^y although 
the vertebrse are very similar. On the other hand the undoubted presence of ganoine 
is an anomalous condition for the Elopida^. Flindersicldhys does not appear to be 
closely related to the ljej)tolepida% so well represented in Jurassic deposits in Australia, 
in which the persiste}it notochord is evident in the centra. It appears to possess both 
Holostean and Teleostean characters. The Lower Cretaceous was evidently a period 
of rapid evolution for bony fishes. 
Smith Woodward records (1912, p. 253) that some Cretaceous genera combine 
'' features which are characteristic even of separate families in the existing fauna.” 
