Nassarius (Mollusca:Neogastropoda
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NASSARIUS (MOLLUSCA:NEOGASTROPODA) FROM THE NEOGE~I<~ OF NORTHWESTERN ECUADOR 1 WILLIAM D. PITT i AND LOIS J. PITT l ABSTRACT East Pacific, as well as the Caribbean Recent and fossil faunas. NassarlUs mas The nassarid fauna from the Neogene tus Olsson, 1964, was descnbed froT!l the formations of northwestern Ecuador con Picaderos Formation, and occurs in both sists of five species, none of which are the Angostura and Onzole formations. known from either the Recent or fossil fau Other species include: N. thielei Olsson, nas of the Caribbean or Pacific. There is 1964, from the Esmeraldas beds, with one species with affinities to the western affinities to an Indo-Pacific species: N. Pacific Recent fauna, one with affinities to hylus Olsson, 1964, known only from the Recent species in both the Caribbean and the Esmeraldas beds; and one species N. eastern Pacific faunas, the remaining repetiti Olsson, 1964, known on:y from •rp three species are known only from the Onzole FormatiOn. Ecuadorian Neogene, one of which, The Angostura Forme t!on of Late Nassarius mcmahini, n. sp., is confined to Miocene age (planktic for tminifpral zom• the Angostura Formation. N. 16) is the oldest formation di~cus~ed .n this paper. The name was first publi~hEd INTRODUCTION by Stainforth (1948, pp. 142, 143, 146 fol lowing an unpublished report of the It is generally accepted that there was International Ecuadorian Petroleum free passage of water between the Company ({lde Bristow and Hoff:!:e!:ter, Caribbean Sea and the Pacific Ocean, 1977' p. 32). through the Isthmus of Panama, for much The name "Esmeralda::: Formation \V<. of the Tertiary Period, allowing exchange proposed by Olsson ( 1942, p. 26Ul for tr1e of molluscan species. It has been suggest highly foraminiferal tuffaceous .,hale-, ed that the closure took place about 3.5 exposed along the coa,.:;t of E.'mt ra:da~ MA (Saito,1976). Jones and Hasson (1985) Province and the Esmeratdas Rivt r. accepted this date as the most likely time Bristow and Hoffstetter ( 1977, p. 141 rec when migration of species ended, with ognized the name Esmeraldas Formation final emergence of the Isthmus at about 3 but considered it to be part of the On.wle MA or later. Formation. Vokes (1988, p. 4) found .t <hff. The Neogene faunas of northwestern cult to accept the name Onzole Formatwn Ecuador have either direct or indirect rela for the mollusk nch depo.'its along the tionship to Caribbean or Pacific faunas, Esmeraldas coast from Punta Gordo. to both Recent and fossil. This paper will dis Camarones and used the term cuss nassarid species from two Neogene "Esmeraldas beds for these deposits formations of northwestern Ecuador, rang exposed at the top of the Onzole ing in age from Late Miocene to Late Formation. Pliocene, and their relationship t o Olsson (1964, p. 10), in discussing fo:,si:: Caribbean and Pacific fa u nas. It is not from the Picaderos Formation, ::>tated that intended to be a monograph of the Family the name came from the village of N assariidae. Picaderos, which is near the center of th•' The five species discussed in this paper outcrop on the Rio Santiago. He h-,ted 16 are all endemic to the Neogene of north s pecies of mollusks from the PtcaderO'i western Ecuador. One species, N . mcmahi F ormation. Of these five occur at ni, n. sp., from the Angostura Formation Picaderos, four occur at Playa de Tign·, has affinities with species in the Recent three are not mentioned in the text, two on ly occur at Cueva de Angostura (Angostura Formation), one is from Playa de Tigre and Picaderos, and one is in tht' 1 Field Associate, Dept. of Geology, California text but not on the faunal list. Academy of Sciences, San Francisco, California, Olsson described the Picaderos For 94118 rna tion as occurring along the Rw 2 Home Address: 2444 38th Ave ., Sacramento, Santiago near the village of Picaderos: California, 95822 however, in the text he shows two 135 136 Tulane Studies in Geology and Paleontology Vol. 29 Picaderos species as occurring along the Class GASTROPODA Cuvier, 1797 Rio Onzole and considerd some Picaderos Subclass PROSOBRANCHIA species as being from the Borbon Milne-Edwards, 1848 Formation. Superorder CAENOGASTROPODA Bristow and Hoffstetter (1977, p. 219, Cox, 1959 232) state that the name Picaderos Order NEOGASTROPODA Thiele, 1925 Formation is in disuse and consider it to Superfamily MURICOIDEA be equal to the Onzole Formation. The Rafinesque, 1815 Servicio N acional de Geologia y Minera Family NASSARIIDAE Iredale, 1916 (Cuadro no. 83) also considers the Subfamily NASSARIINAE Picaderos Formation to be equal to the Onzole Formation; however, it places Genus NASSARIUS Dumeril, 1806 Olsson's Playa de Tigre locality at the border of the Onzole and Angostura forma Nassarius DUMERIL, 1806, Zool. Anal., p. 166. tions and within the Angostura Formation. Type species: Buccinum arcularia Linn., 1758, Olsson's collecting data is not precise by monotypy. enough to know exactly how close to Playa de Tigre he made his collections, thus it is Subgenus NASSARIUS s.s. difficult to know in which formation this NASSARIUS (NASSARIUS) REPETITI locality should be placed. Olsson, in the Olsson text, also listed some species as occurring Plate 1, figure 4 at Picaderos; Borbon Formation. It is pos Nassarius repetiti OLSSON, 1964, Neogene sible that some of his collecting data is in Moll. Northwest. Ecuador, p. 146, pl. 24, figs. 6, error and we may never know where some 6a. of his specimens were really collected. Description: "The shell is small, subovate, with an elevated sharp spire of about seven ABBREVIATIONS FOR whorls, including that of the small nucleus con REPOSITORY INSTITUTIONS sisting of one turn. The sculpture of the spire whorls consists of three rows of sharply beaded CASG - California Academy of Sciences, spiral cords which stand high above the adja San Francisco, California. cent sutural zones, which thus appear as if USNM- United States National Museum deeply excavated, the fine suture itself lying of Natural History, Washington D.C. away in the bottom as if hidden. The spirals on PRI - Paleontological Research Institution, the apertural side of the body whorl number Ithaca, New York. about seven with an additional eight or nine, much smaller ones, partly smooth lying along ACKNOWLEDGMENTS the basal sulcus and over the short beak in front. The .spiral cords are neatly beaded by We want to thank Elt:lily Vokes for mak small axials which faintly undulate the spiral ing Tulane University collections avail interspaces. On mature specimens, the sculp able and for help with the manuscript. We ture is obsolete on the back of the body whorl, also want to thank the following persons replaced there by a large smooth patch. The for making museum collections available: aperture is broadly subovate with a short longi Thomas Waller, United States National tudinal posterior canal at its junction with the Museum of Natural History; Gary parietal wall. The outer lip is thickened by a rib Rosenberg, Academy of Natural Sciences, on the back, and bears on its inner side four or Philadelphia; and Warren Allmon, more small denticles. There is a thin spread of Paleontological Research Institution. callus over the inner lip through which the Thanks also to Allan McMakin of Astoria, underlying spiral cords still show through; the Oregon, for the photography. parietal callus extends downward over the pil lar is a small shelflike feature [sic], bearing four small denticles a long it. The siphonal canal SYSTEMATIC PALEONTOLOGY notch is deep, its sides a little elevated, its fasci ole marked with small smooth spirals but has Phylum MOLLUSCA Cuvier, 1797 no bordering keel." (Olsson, 1964) No.4 N eogene Nassarius 137 Holotype: USNM 643999; height 14.6 mm, Pacific species N . iodes (Dall, l919 J, N. diameter 7.8 mm. moestus (Hinds, 1844), and !v. tiarula Type locality: Onzole Formation, Telembi, (Kiener, 1841), which occurs as far north Esmeraldas Prov., Ecuador. as San Francisco, Califorma 1 &'"> N. tegula Occurrence: Onzole Formation, Ecuador. (Reeve, 1853), see Skoglund, 1992, p. 85]. Nassarius iodes differs from N. mcmalani Discussion: Nassarius repetiti is similar in having three or four weak l1rations on toN. complanatus (Powys, 1835) from the the inner side of the outer lip and one Tropical East Pacific but differs in being much larger one posterior to the other:- at larger, more slender with the spire whorls about the center of the apertu.re The body slightly convex rather than straight sided. whorl of N. iodes has ten axml ribs, fc<ding Olsson (1964, p. 145) placed Telembi in the out on the last one-third of !he wnorl, Angostura Formation; however, Bristow which are crossed by seven spiral grooves: and Hoffstetter (1977, p. 218) place the the columellar callus pdrl IS thm. locality at Telembi within the Onzole Nassarius moestus differs in h.av ng fou.r Formation. sh ort lirations on thP inner <:;Ide of the outer lip and one much largt>r tha'1 the NASSARIUS (NASSARIUS) MCMAKlNI rest, posterior to the other:;; at tht· rt·"ltPr of Pitt and Pitt, n. sp. the aperture. InN. moestus the body whorl Plate 1, figure 1 h as ten beaded, axial ribs with s-mooth Description: Shell small; five whorls, plus a interspaces, fading out on the last one protoconch of about two rounded, smooth third of the whorl. Nassarius tiurula di~' whorls, end broken. First spire whorl expanding fers in having five short lirations on the abruptly, axial sculpture appearing immediatly, inner side of the outer lip with one much but eroded on early whorls; remaining spire larger liration posterior to the re t, at tne whorls with eleven axial ribs crossed by about cen ter of the aperture.