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Anomalacantha dentata (Mast, 1910)

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Benson, 1966, p. 170-171; pl. 5, figs. 10-11:

Anomalacantha dentata (Mast)

Heteracantha dentata Mast, 1910, Deutsche Tiefsee-Exped., vol. 19, no. 4, p. 159, P1. 37, fig. 47.
Cladococcus lychnosphaera Hollande and Enjumet, 1960, Paris, Mus. Nat. d’Hist. Natur., Archives, vol. 7, ser. 7, p. 115, P1. 55, figs. 1, 2.

Small, spherical, latticed shell from which originate 8-12 or more long, broad, regularly arranged, three-bladed radial spines, each with thorns or lateral branches originating from the blades at 2-5 or more verticils. Pores of shell circular, of equal size, 5-6 on half the shell circumference, surrounded by well-defined, hexagonal frames. Surface of shell either smooth, thorny, or with thin, conical, often distally forked, secondary spines of variable length (up to 25 µm), all originating singly from the nodes of the intervening bars. In fully developed tests a verticil of long, arborescently branched lateral spines is present on each main spine. All verticils at a common distance from the center of the test. The lateral, arborescent branches do not anastomose with those of adjacent main spines; therefore, an outer shell is not developed.

Measurements: based on 30 specimens from stations 81, 191, and 192: diameter of shell 53-69 µm, length of radial spines 166-246 µm, breadth at their bases 6-12 µm.

Remarks. There is no essential difference between the Gulf species and Cladococcus lychnosphaera Hollande and Enjumet. The only difference of note is the variable number of verticils of lateral branches on the radial spines of the Gulf specimens. The genus Cladococcus Müller (1856, p. 485) is defined as having all spines similar, but in the Gulf specimens as well as in the illustrations of C. lychnosphaera (Hollande and Enjumet, 1960, P1. 55, figs. 1, 2) there are branched or unbranched, thin, conical by-spines in addition to the radial main spines; this species, therefore, should be placed in the genus Anomalacantha Loeblich and Tappan [= Heteracantha Mast]. Heteracantha dentata Mast differs from the Gulf species only in the lack of relatively large arborescent branches which arise from the rnain spines at a common level. This feature is characteristic only of fully developed individuals. The majority of the specimens from the Gulf are identical with Mast's species.

Distribution. This species is nearly cosmopolitan in the Gulf and undergoes a marked increase in frequency in the northern half of the Gulf. It is very rare at the few southern Gulf stations where it is present, namely 34, 56, 81, 91, 92, 93, 95, and 99. North of this region it is present at all stations except 203 and 214. It is rare at all stations except 151 (2.6%), l84 (2.8%), 192 (2.4%), and 206 (2.4%) where it is common. In general its frequency is highest at stations located within or near the diatomite facies; therefore, its distribution in the northern Gulf is influenced by upwelling. Its higher frequency in the northern Gulf also suggests its greater tolerance for waters with higher than average temperature and salinity. Its distribution in the southern Gulf does not appear to be related to upwelling in this region.
This species is widespread in Recent tropical seas. Heteracantha dentata Mast was reported from the tropical Atlantic in the region of the Canary Islands. Cladococcus lychnosphaera Hollande and Enjumet was reported from the Mediterranean Sea in the Bay of Algiers.

Benson 1966











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