Ne W Neritidae from Baja, Mexico 645 646 Alan J
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NE W NERITIDAE FROM BAJA, MEXICO 645 646 ALAN J. CUSHING WOODS AND L. R. SAUL microstructure from that of the shell and more of the callus makes aperture down the most susceptible to dissolution. Cossmann (1925, stable position for the shell. Despite Yonge, p. 200) suggested that the deck area is fre- the topography of the apertural face of Ve- quently destroyed by fossilization. The UCLA lates seems ill-fit to a hard substrate. Had specimens do not appear to have a feathered Velates lived on a firm but not hard bottom, edge where the deck is missing. Instead there its heavy callus would have provided stability is an apparently normal shell thickness, in the presence of currents. abruptly cracked off. That all specimens are The association of abundant V perversus broken in the same area suggests either a at UCLA loc. 4244 with Turritella andersoni structural weakness in the shell or perhaps Dickerson and Venericardia (Pacificor) hornii the activities of a predator. Neritids are known lutmani Turner is further indication of a to resorb internal shell structures (Wood- firm to moderately soft bottom rather than a ward, 1892) whose absence might promote hard substrate. This association also suggests shell failure during fossilization. In that case, a sublittoral rather than littoral habitat, and broken pieces of the deck might be expected the large Velates spp. with thin outer lips may to be found adjacent to the break. Such have have lived in slightly deeper water than most not been found in these specimens. Predator modern neritids. The abandonment by the breakage, a likely explanation, would tend to neritaceans of such shallow-water, level-bot- scatter the fragments. Vermeij (1977) has in- tom habitats may have been caused by pred- dicated that increased gastropod shell stur- ator pressure. In contrast to the thin lip of diness in the later Cretaceous may have been the typical form, the thickened outer lip of a response to increase in shell-destroying some Velates spp., such as V. vizcainoensis, predators. If these Otostoma retracted well would remain unbroken in a rougher water back into their shells a blow to the deck area habitat. might gain access to the animal. Addition of callus to the deck area could be a response VELATES VIZCAINOENSIS n. sp. to this weakness. Figures 5.8-5.14 Although sharing some morphological Description.—Shell small for the genus similarities with Otostoma, Velates has abap- (Table 2), thick walled, capuliform; spire very erturally a patelloid shape suggestive of life low, enveloped by later whorls and callus; upon a hard substrate. Yonge (1960, p. 116) whorl very roundly inflated, enlarging rap- stated that marine neritaceans are universally idly; spiral surface smooth, ablabral margin distributed on hard substrate between tide overlapped by thick callus deposit; deck marks and in shallow water; they do not in- broad, swollen with thick callus deposit and vade muddy areas. The thick convex callus thick-walled ablabral margins lapping onto pad of Velates, however, gives the apertural spiral surface, slight lunate depression along side a very different configuration to that of the inner lip, and marked "umbilical" some other gastropods which are abapertur- depression; aperture semioval; inner lip edge ally similar. Crepidula, Concholepas, and slightly convex to the aperture with 7 sub- limpets clamp the rim of shell down onto a equal strong teeth separated by interspaces hard substrate, but Velates, on a flat surface, almost as wide as the teeth; teeth grouped rests on the convex deck and the medial area from anterior to posterior into small anterior of the outer lip edge, and the shell rocks readi- pair, large submedian tooth, large posterior ly resting on these two convexly curved areas. pair, and medium posterior pair, projecting Specimens of V. perversus from the Paris as ridges onto the deck nearly halfway across Basin are beautifully preserved, and many lunate depression; outer lip smooth, thick- specimens retain some of their color mark- ened. ings. The apertural face is devoid of color Type specimens.—Holotype, UCLA 59421; markings, but the abapertural surface is paratypes, UCLA 59422-59425. marked. There is even a thin color-marked Type locality. —UCLA 7083, east of Bahia layer deposited over the callus on this surface. Sebastian Vizcaino, Baja California, Mexico. The aperture, therefore, probably faced down Age. —Late Paleocene(?). upon the substrate. Furthermore the weight Remarks. — The above description is based NEWNERITIDAE FROMBAJA, MEXICO 647 TABLE 2—Dimensions of Velates vizcainoensis n. sp. Specimens Height Width Thickness Inner lip length Aperture width UCLA 59421 13.8 mm 15.8 mm 10.0 mm 8.5 mm 3.0 mm UCLA 59422 14.1 mm 15.9 mm 8.5 mm* 9.2 mm 3.8 mm UCLA 59423 13.2 mm 14.5 mm 10.0 mm 8.4 mm 3.3 mm UCLA 59424 12.0 mm 13.5 mm 4.0 mm* 7.7 mm 3.4 mm * Incomplete. upon six specimens (two complete), all from unequal bifid teeth rather than 7 teeth, 6 of the type locality. All are small for Velates, which are paired. but this may be characteristic of the deposit V. vokesi Cooke, 1946, (=Neretina(l) gran- rather than of the species. V. vizcainoensis is dis Cooke, 1919, non Sowerby, 1840) has a most similar to V. californicus Vokes, 1935, higher spire than V. vizcainoensis with an which is also of Paleocene age at its type lo- angulate shoulder similar to V. perversus cality. It differs from V calif ornicus in its rather than the rounded shoulder of V. viz- thickened outer lip, less marked lunate cainoensis. Woodring (1957, p. 67) also sug- depression bordering the inner lip, thicker gested that V.floridanus Richards, 1946, may more rolled ablabral deck margins, and be V. perversus. The low rounded cords on slightly less convexly swollen deck surface. the "columellar callus" described and figured V. vizcainoensis differs from V. perversus in by Richards (1946, p. 2, Text Pl. 2, fig. 1) are its roundly inflated whorl, its thickened outer apparently on the internal mold and are not lip margin, its broader teeth on the inner lip comparable to extensions of the teeth of V. separated by interspaces nearly as wide as the vizcainoensis upon the deck. The interior of teeth that project as ridges onto the deck. The V. vizcainoensis (Figure 5.8) shows no trace spire of V. vizcainoensis is also apparently of any similar cords. Richards' figures—in lower and enveloped at an earlier growth stage more conical shape, oval plan, and large size— than is that of V. perversus. The thickened are more suggestive of V. perversus than of outer lip is similar to that of V. perversus V. vizcainoensis or V. californicus. V. vicensis (Gmelin) subsp.(?) (Woodring, 1957, p. 66, Staid-Staadt, 1964, and V. vicensis rotundior Pl. 14, figs. 5-8) and to that of V. balkanicus Staid-Staadt, 1964, are described from Span- Bontscheff, 1897, (p. 380, Pl. 6, figs. 1-6) that ish localities of Ledian age (Farres and Staid- also has a thickened and rimmed outer lip, Staadt, 1964). Unfortunately apertures were but V. balkanicus has heavier teeth than V. not exposed. Both, however, have a subangu- perversus subsp. from Panama, and Wood- late shoulder similar to that of V. perversus ring doubted that the rimmed outer lip in- and a sulcus from spire to posterior margin dicated close relationship. Because V. per- that is not present on V. vizcainoensis or V. versus (Gmelin) subspecies(?) is, except for the perversus. The deck callus of V. vizcainoensis thickened rimmed outer lip, similar to V. is less swollen than that of V. perversus, and perversus, its thickened outer lip is unlikely to the periphery is rounded by the thick, rolled- indicate close relationship to V. vizcainoensis. over callus. V. vizcainoensis differs from V. balkanicus in Etymology. — The species is named for the having 7 teeth on the inner lip rather than 8, Bahia Sebastian Vizcaino, 0.9 km west of the a shallower lunate depression on the inner lip, fossil locality. thick rolled-over callus deposit around the ablabral margin, convex rather than straight inner lip profile, and a shallower "umbilical" VELATES CALIFORNICUS Vokes, 1935 depression. Figures 5.15-5.16, 5.18-5.19, 5.21 V noetlingi Cossmann and Pissarro, 1909 Velates californicus VOKES, 1935, p. 384, PL. 26, (= V tibeticus Douville, 1916, fide Cox, 1931) figs. 3-8t ; SAUL, 1983a, p. 80, figs. A-C. is more oval, has a very low spire, and slightly Hypotype. — UCLA 58275. more conispiral coiling. It is also said (Coss- Locality.—UCLA loc. 3173, Simi Hills, mann and Pissarro, 1909, p. 76) to have 6 Ventura Co., Calif. 648 ALAN J. CUSHING WOODS AND L. R. SAUL Dimensions of UCLA 58275.— Height 23.2 (Stewart, 1946, p. 92). This suggests that the mm; width 28.0 mm; thickness 15.0 mm; basal Avenal might not be younger than late length of inner lip 16.3 mm; width of aper- "Capay." Keppler, Squires and Fritsche tural opening 11.0 mm. (1984), however, recognized only "Domen- Age.—Late Paleocene through early Eocene. gine Stage" mollusks from the Avenal. The Vokes (1935) considered V. californicus to "Domengine" was considered to be of middle range from early middle Eocene to late mid- Eocene age (Givens, 1974, p. 22), but the dle Eocene. He placed the type locality of V. lower "Domengine" is now recognized as californicus (UCB loc. 3792) and that of his being correlative with the upper Ypresian and plesiotype (UCB loc. 7009) in the lower Lla- of early Eocene age (Saul, 1983a, fig. 1). jas Formation, but recent mapping in the Simi Remarks.