ARTHRODIRE PREDATION BY ONCYCHODUS (PISCES, CROSSOPTERYGII) FROM THE LATE DEVONIAN GOGO FORMATION, WESTERN AUSTRALIA

WA Museum Records and Supplements | Updated 1 decade ago

Introduction: During late September - early October 1990 a joint expedition by the Australian National University Geology Department and the Western Australian Museum collected a large number of well-preserved fossil fishes from the Gogo Formation, outcropping approximately 100km east of Fitzroy Crossing. Amogst the new finds is a well-preserved example of the predatory crossopterygian fish Onychodus sp. The specimen (WAM 90.11.1; Figure I) is of special interest though because the bones of an arthrodire (Pisces, Placodermi) were found enclosed within the cranial bones of the Onychodus showing the first direct evidence of active predation on arthrodires by Onychodus. The nature of fossilisation of the fish remains in the Gogo Formation is such that, after death, the onset of concretion formation was rapid, preventing damage to many of the delicate perichondral cartilage bones of the gill-aches (Long 1988). Because the skull bones and most of the body of the Onychodus were not all present in the concretion, it is concluded that the specimen was partially disrupted after its death. This is not unusual because the skull roof bones of this specimen were only loosely connected, and none were in articulated position. It appears that the Onychodus choked on the placoderm and fell to the bottom where it was either partly scavenged or decomposed before a larger section of the head, including the gullet with the placoderm remains, was quickly buried in the sediment.

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Author(s) LONG, JOHN A. : Part 2
Page Number
479