The Pacific Plate (Figures 1,2) is the largest of all Earth's lithospheric plates and occupies most of the area that has been referred to as the Pacific Basin (Figures 3, 4). Eastern Pacific: The eastern part of the Pacific is not included in the Indo-Pacific. Of the 28 Indo-Pacific species, eight are restricted to the Indo-West Pacific, and 20 occur non-marginally on the Pacific Plate.
It extends from the eastern Indian Ocean to the western edge of the Pacific Plate in the New Guinea region (Smith-Vaniz and Springer, 1971; Springer, unpublished data). Xiphasia setifer ranges from the east coast of Africa to the western edge of the Pacific plate; X. The absence of drepanids in the non-marginal parts of the Pacific plate is perhaps unexpected.
Gobiopsis sensu stricto is distributed from southeastern Africa to the western edge of the Pacific Plate. Therefore, there are nine species of Thalasoma present in the non-marginal parts of the Pacific Plate. Four of the monotypic genera (Pinjalo, Symphorichthys, and Symphorus, which are shallow-dwelling, and Lipocheilus, which occurs at depths of 94 m or more) do not occur on the Pacific Plate in a non-marginal manner.
Only one of the species occurs non-marginally on the Pacific shelf, and only on the Hawaiian Islands (with the exception of Hawaii). Two of the species range from the western Indian Ocean to the edge of the Pacific plate; The family is restricted to the Indo-Western Pacific, from the east coast of Africa (Smith, 1959) to New Guinea (Munro, 1958, as Ctenotrypauchen among Taenioidae), at the edge of the Pacific Plate.
Discussion
Fourteen Queensland families do not occur (or are not expected to occur) in South-East Africa, and 13 South-East African families do not occur (or are not expected to occur) in Queensland. Similar numbers for these families were reported by Myers and Shepard (1981) only for Guam, on the edge of the Pacific plate. Using information obtained from an analysis of the coastal fish fauna of the Pacific plate, I attempted to determine the total number of coastal fish species for the entire Indo-Pacific.
Rosewater (1972) believed that the closest relative of the widespread Pacific plate endemic gastropod, Tectarius grandinatus, is T. In contrast to the overwhelming majority of the fish families that are well represented on the. If no islands of the relatively young Caroline Islands chain3 were on the Pacific Plate.
The remaining 152 species of fossils are also represented in the extant fauna of the Hawaiian Islands. Nevertheless, it is instructive to examine the causes (particularly geotectonic causes) and consequences of the limited types of extinctions that may occur on the Pacific Plate. It is possible that some of the genera now considered endemic will turn out to be more widely distributed in the Indo-Pacific.
The abundance of coastal endemic fish species on the Plate, especially the widespread endemics, convinced me of the importance of the Pacific Plate as a biogeographic region. However, I would wholeheartedly agree with recognizing the Indo-Pacific as a biogeographical unit, with the Pacific Plate distinguished as a major sub-unit. DISTRIBUTION OF DISTRIBUTION DISTRIBUTION OF THE HAWAIIAN ISLANDS AND NORTH-SOUTH ON THE PACIFIC BEACH.—It is more. known for the geology and biology of the Hawaiian Islands than any other island area in the Indo-Pacific.
Kay (in litt.) now informs me that a small proportion of Hawaiian molluscs have their closest relationships (not cladistically determined) with molluscs on the Pacific plate. Concurrent with the formation of some of the islands of the Hawaiian Imperial Chain, other island groups formed as far to the southeast on the Pacific Plate near the East Pacific Rise. In Time Period 2, two possible vicariance events occurred, one of which is island integration (Figure 61: Hypothesis 1a) and one of which is not (Figure 61: Hypothesis Ib); in the latter case, Southeast Oceania is isolated from the rest of the Pacific Plate.
Much of the following discussion is based on geologic information from these two studies. The ancient structure closest to Pitcairn is in the high Gambier group of islands (4.7–7.1 m.y.) of the southern Tuamotu Archipelago. Rosenblatt provided me with a list of 31 species (not all identified as species) in the San Felix collection.
Formal cladistic relationships between the Marquesas endemics have not been proposed, but these relationships are clearly with other species on the Pacific Plate. A vicarious event occurred that isolated the Marquesas from the other islands of the Pacific plate and allowed divergence of (at least) the Marquesas population. Older, non-preserving parts of the Pacific plate are thought to have been subducted beneath the continental areas bordering the plate's western margin.
The thrust causing the northwestward movement of the plate (Figure 1) from the active formation region (East Pacific Rise) is not known. The western edge of the Pacific plate therefore delineates the Andesite line of biogeographers and geologists (see Appendix 1 for a historical discussion of the Andesite line). These transform faults intersected the spreading uplift that was continuous (with offsets) with the spreading uplift that formed the southwestern margin of the Pacific plate.
At least the gap could have isolated the Pacific Plate in this region and contributed to the subsequent divergence of the Plate biota (or the formation of Type 1 endemics). The geotectonic history of the islands along the Pacific plate margin extending from New Guinea to the Tonga Islands is highly complex, and much remains to be explained. The discussion here is mainly confined to that part of the margin which extends from the New Hebrides to the Tonga Islands.
Most of the Type 2 endemics (see discussion of species endemism) I report from the Pacific Plate are restricted to the islands extending east from the Tonga Islands to Easter Island. The same vicarious event could enforce the endemism of the widespread Pacific plate endemics (type 1). The Cenozoic history given here appears to have little bearing on an explanation of the present-day biotic isolation of the Pacific plate in the Polynesian area.
Addendum
