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Lamprocyclas hadros Nigrini and Caulet, 1992

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Lamprocyclas hadros Nrigrini and Caulet, n. sp.
Plate 5, figures 7-12; plate 6, figure 1

Description: Shell heavy, surface rough with small longitudinal ridges between the pore rows of the thorax. Cephalis trilobate, open or, at least, with a large pore at the base of the apical horn; remaining cephalic pores in well defined longitudinal rows separated by distinct ridges, which in some specimens are prolonged into the basal part of the apical horn. Strong, three-bladed apical horn. Lateral spines extend into the thoracic wall sometimes forming shallow depressions and may project as small thorns. Collar stricture not pronounced.

Thorax conical with subcircular pores, increasing slightly in size distally, arranged in longitudinal rows, 13-15 on a half equator. Lumbar stricture well defined.

Abdomen elongate-campanulate with subcircular pores, increasing in size distally, arranged in longitudinal rows, 13-15 on a half equator. Mouth slightly constricted. Poreless peristome generally not well differentiated from terminal teeth, which are usually strong and irregular, sometimes forked, often quite long (up to 29 µm). Some specimens (pl. 5, fig. 8I have only rudimentary teeth, but can still be distinguished by the characteristic cephalic structure and enlarged abdomen. Small, thorn-like projections scattered over the distal surface of the abdomen. In a few specimens the abdominal pores are disorganized distally (pl. 5, fig. 7), giving a lace-like appearance.

Dimensions (based on 22 specimens): Length of apical horn 67-86 µm; of cephalis 33-40 µm; of thorax 67-82 µm; of abdomen (excluding peristome and terminal teeth) 95-160 µm; of terminal teeth up to 48 µm. Maximum breadth of cephalis 33-38 µm; of thorax 100-22 µm; of abdomen 154-192 µm.

Distinguishing characters: Species differs from L. maritalis Haeckel ventrocosa Nigrini by having an open, rather than closed, cephalis bearing distinct longitudinal ridges. In addition it generally has a longer abdomen, less constricted mouth and longer, often forked and more irregular terminal teeth when present. We have also observed a similar, undescribed form of Lamprocyclas (pl. 5, fig. 2) with an open cephalic structure, but which can be distinguished from L. hadros by its smaller abdomen and by its more disorganized cephalic pores and less distinct cephalic ridges. Forms with a lace-like termination resemble members of the Lamprocyrtis hannai (Campbell and Clark) group, but L. hannai is generally smaller and lacks prominent cephalic ridges.

Range: In the Peru material the species ranges form the early Pliocene (S. peregrina Zone) to the Recent; it is few to common. On the Oman material the species is not so common, but ranges from the Late Miocene (D. Petterssoni Zone) to the Recent. In the oldest Miocene material forms transitional with the L. hannai group were observed. The species is absent from the Somali material.

Type: Holotype 112-683A-2H-cc, 1-S40/0, MNHN (Paris) No. F61416; Paratype 112-688A-1H-cc, 1-M29/3, MNHN (Paris) No. F61417; Paratype 117-751B-12X-cc, Z35/4, MNHN (Paris) No. F61418.

Etymology: hadros = well-developed, stout (Greek).
Nigrini and Caulet 1992











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